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In Reply to: "Tight" bass requires bass traps and/or parametric bass EQ in most home listening rooms posted by Richard BassNut Greene on December 23, 2003 at 10:12:33:
using "vents", tight / accurate bass goes out the window. If one is willing to live with this undeniable fact and trade-off, both bass extension and max spl's can be increased by using a vent. If one is not willing to deal with slop but can deal with losing a few Hz of extension and not being able to play at 115 dB's at the bass extreme's, sealed designs using properly chosen drivers with the "most correct" sized and built boxes will always provide the "tightest" bass. As such, vented designs should be relegated to "low fi" use, such as pro sound reinforcement or use for sound effects ( Home Theater ) where volume of sound ( sensitivity ) is more of a concern than quality of sound ( linearity ). Sean
>PS... ANY driver with a high impedance peak at / near resonance instantly becomes "less tight" and "less controllable". This is due to the inability of the amplifier to load into / transfer power into the driver. Since 98% of all vented designs are of either passive radiator, ported, slot loaded, etc... design, and these designs almost universally have high impedance peaks / multiple impedance peaks due to their very nature, the bass is of lower quality.
PPS... There are ways to improve sealed designs beyond just proper implimentation of the driver / box interphase. This requires more driver(s) and a sturdier amplifier though. Obviously, the cost of such a design is increased, but nobody ever said high performance was cheap.
PPSS... your comments about dipole's and bass extension primarily has to do with either poor placement or lack of physical size in the room to obtain optimum placement. Due to either of these conditions, the wavelengths involved run into problems with out of phase cancellation, therefore reducing the output at the lowest frequencies. Optimally, one would want to use a dipolar loaded compound arrangement in a large room. Not only is transient response improved, but so is power handling. Due to the improved loading of the dipolar design and the lack of cancellation from increased room size, neither spl's or cancellation are as much of a problem. At the same time, linearity is improved due to improved transient response and less of a load on any given motor structure.
PPPSS... Horns are another valid attempt at achieving this, but the size and construction of the cabinet itself is relatively prohibitive. Internal reflections and standing waves within the horn body itself tend to lower performance and increase distortions. Radiusing the internals and paying attention to the flare rate / parallel surfaces inside the horn can minimize most of this though. The biggest problem here is the sheer physical size of the horn body itself, as the mouth of the horn would literally be quite huge in order to reproduce the lowest audible frequencies. As a side note, some bass horns are sealed, some are vented. The problems associated with vented bass horns and the horn body itself can then further compound themselves, producing what is truly a "high spl, low linearity" device.
Follow Ups:
Well, yes and no about increasing SPL and extension with a vent. Below resonance, a vented system rolls off quickly; whereas a sealed system rolls of at 6 db per octave. So, room gain may actually make the sealed system have greater extension.The mass of the air in the vent and the tuning of the vent is a substitute for a larger volume of air in a sealed box. So yes, if you had everything constant, except the use of the vent, the vented enclosure could be tuned for greater extension and efficiency.
But everything is usually not constant.
Bass Nut may or may not agree, but my understanding is that the principal reason that sealed enclosures work better for DIY subwoofer builders is that they are less "critical" than vented enclosures and therefore more likely to yield the desired result. Small dimensional errors, failure to account for volume taken up by braces, etc. is more likely to screw up a vented box (or screw it up more significantly) than a sealed enclosure.
It doesn't matter if it is DIY or "professionaly designed". Sealed boxes provide the most natural presentation, the least amount of ringing, the most linear power transfer, etc... with all things being equal. Obviously, there is a LOT more math and fine-tuning involved with any type of reflex design, so things can only get worse for those that lack the technical expertise or "intestinal fortitude" to really dig into proper vent alignment. As mentioned elsewhere in this thread, vents are most appropriate where quantity of bass is more important than quality of bass. Sean
>
"Optimally, one would want to use a dipolar loaded compound arrangement in a large room. Not only is transient response improved, but so is power handling. Due to the improved loading of the dipolar design and the lack of cancellation from increased room size, neither spl's or cancellation are as much of a problem. At the same time, linearity is improved due to improved transient response and less of a load on any given motor structure."Could you please explain more in detail what kind of system you mean?
Thanks!
/Peter
Sean, currently my system consists of a Denon 3600, Mains: Snell D', Center: Snell and Bose Acoustimass for the surrounds (yes, I know I need surrounds). The Snell D' have plenty of Bass for me... I'd like to build a HT Sub...just not a boomy one. After visiting Adires website I planned on using the following: HS200 Amp, Shiva 12", 142.5L Vented Cabinet and Adires EBS alignment. Before I shelled out the cash I figured I'd take to the threads and find someone like yourself that is educated in this area to insure I was making the right decision. Any information would be appreciated.
1) How big of a room are you in ?2) Do you live in a house or multi-resident dwelling ?
3) What type of SPL range are you looking for ?
4) Are you capable of assembling a "loosely compiled gathering of parts" on your own ?
5) What price range are you looking at ?
The more specific your answers, the more accurate of a recommendation i can make. Sean
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1. 12' x 24'
2. House
3. 110
4. Yes
5. $500
With your $500 budget,I would buy an Adire Rava,@ the $399 price it is hard to build a much better sub
The probability of an audiophile being able to identify whether a well-designed subwoofer is ported or sealed while listening to
full-range music is low for most listening rooms ... unless the room is treated with bass traps and/or the subwoofer is parametrically equalized.Room acoustics will cause subwoofer frequency response deviations of
+/-10dB in most rooms, whether the subwoofer is vented or sealed.Those room acoustics will dominate the sound of bass under 80Hz. (subwoofer frequencies) and obscure differences among subwoofers unless the room is treated with many bass traps and/or the subwoofer is parametrically equalized.
I personally build only sealed enclosure subwoofers for my own use.
I also use EQ to reduce bass booms in my listening room.See the link for further reading about subwoofer group delay.
"The probability of an audiophile being able to identify whether a well-designed subwoofer is ported or sealed while listening to
full-range music is low for most listening rooms ..."Your "probability" is "probably" pretty accurate because most audiophiles aren't actually "good listeners". The fact that the mass majority of both "audiophile approved" and "low-fi" speakers are vented designs should tell you something. That is, the average audiophile simply buys more expensive gear and consider themselves to have better hearing because they spent more money and / or saw some of the products that they own in a "high end" magazine.
Thanks for your honesty. Sean
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Thanks for posting it AND making it "clickable". SO much nicer for us lazy folks : )As a side note, the info that is presented there is something that i've been promoting / trying to teach others both here and ( primarily ) at Agon for several years now. While most of the Adire drivers that i've seen seem to be best suited for vented designs, i'm glad that they are honest enough to provide information like that on their website. Sean
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Hi all,Note that one can actually design a vented box with group delay equal to - or lower than - a sealed box over the audible range. Additionally, note that since group delay is a derivative WRT frequency, the lower in frequency you play the higher the group delay - sealed OR ported.
Sealed boxes are easy to use, and quite effective; however, there are many benefits to ported boxes that really should not be dismissed out-of-hand. Lower distortion, lower extension, equivalent group delay (from an audible standpoint - below the threshold of audiblity), and a few other benefits mean a properly ported box can be even more effective.
NOTE: we don't espouse vented or sealed, but rather a proper design for a given application. We have finished products and kits implementing both approaches, and drivers suited to both applications.
Dan Wiggins
Adire Audio
What does one do about the noticeably higher impedance peak that most vented designs produce? Obviously, as the impedance is higher, you get less power transfer. As you get less power transfer, you have less control over the driver. Since the driver is already suffering from ( in the mass majority of designs ) a higher level of self-oscillation, the effects are compounded. On top of this, most modern drivers designed for vented operation are of a long throw variety. Due to the massive motor structure and longer throw, you now have an even greater amount of reflected EMF that the amp has to deal with. Add this all up ( lack of control due to reduced power transfer related to higher impedances, higher levels of un-damped self-oscillation, increased levels of reflected EMF that the amp has to counter ), etc... and you end up with the "bass slop" that the vast majority of vented designs produce.By the way, i forgot to mention the problems with trying to design a system that took into account rising Q due to thermal conditions, the problems with optimizing box / port tuning due to variances over a wide spl range, reducing port turbulence while maintaining high flow velocities over a wide spl range, out of band emissions from the port, variations in transient response due to lack of optimization over a wide range, etc... This is not to mention all the problems associated with Passive's, which can never equal a port ( let alone a sealed design ) due to the reciprocating mass of the PR itself.
While it is easy to make claims and say that "we have products that will work universally", but truth be told, the constant and very simple "air spring" inside of a sealed box is far more consistent and reliable than trying to optimize all of the variables of a vented design for a wide range of operating parameters. As i mentioned, audiophiles should be concerned with quality over quantity. There's no way to take an out of phase signal and combine it with an in-phase signal and make it work for you without drawbacks and / or a HELLUVA lot of attention required. Sean
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Actually, an impedance peak is irrelevant. Sure, you can't get as much power into the driver, but it's an effect of resonance - you NEED less power at resonance to move the driver. Bass impedance peaks aren't a problem at all, regardless of what some experts in the audio community claim. Quick reality check - does the frequency response of your sub have a big dip at the impedance peak? If not, then the less power delivered at the peak isn't a problem.Note that with higher peaks, the damping factor of the system goes UP; damping factor is load impedance divided by amplifier output impedance; increase the load impedance, damping factor goes up. Meaning the amp can actually control the driver better. Less power (but that's irrelevant as described above), but the amp can control the driver even better.
As far as a sealed box versus ported box, it's easy to optimize both. I had trouble at first, but it's not a problem any more. Like one of my old college math profs used to say, it's the first few thousand integrals that are the hardest... For a seasoned professional, working out a bass alignment should be child's play. If it's not, then I'd take the other more difficult aspects (crossover design, or even more difficult driver design) with a block of salt.
Passives are often quite superior to ports, especially in terms of linearity with SPL. Compression in a port is a serious issue; compresison in a PR is easy to control, as it's just linearity of suspension Cms and Rms over excursion. And both of those tend to be a lot more linear - and much wider in terms of effective pressure output - than a vent. Vents are considerably lower cost, though, and that is why they are so often used.
Note that in our white paper we point out that frequency response and group delay are inherently related by the Hilbert Transform; if you have the same frequency response, you'll have the same group delay (and conversely having the same group delay implies the same frequency response). The reason vented systems tend to have higher group delay is because they tend to have deeper extension. Optimizing a vented system to behave like a sealed box and you'll find that the group delays are surprisingly similar.
Lastly, note that the output of a port is IN PHASE with the driver at frequencies around and above tuning; they are only out of phase below tuning. So it's not a matter of making in and out of phase signals combine - it's a matter of adding two high pass filters together properly (the box/driver is one high pass filter, then vent/box being the second).
Dan Wiggins
Adire Audio
"Actually, an impedance peak is irrelevant. Sure, you can't get as much power into the driver, but it's an effect of resonance - you NEED less power at resonance to move the driver. Bass impedance peaks aren't a problem at all, regardless of what some experts in the audio community claim. Quick reality check - does the frequency response of your sub have a big dip at the impedance peak? If not, then the less power delivered at the peak isn't a problem."Just the opposite is true of a vented design. That is, you have a peak(s) at resonance, not a dip. This is because the driver and / or vent is self-oscillating and is NOT responding to the input of the drive signal in a linear fashion. If a speaker produces a peak ( or a dip for that matter ) ANYWHERE in its' passband, it is responding in a non-linear manner. That is a distortion and it is directly related to a lack of linearity i.e. increased output with decreased drive.
"Note that with higher peaks, the damping factor of the system goes UP; damping factor is load impedance divided by amplifier output impedance; increase the load impedance, damping factor goes up. Meaning the amp can actually control the driver better. Less power (but that's irrelevant as described above), but the amp can control the driver even better."
Time for a reality check here. While damping factor goes up, all that this does is reduce the ability of the load to modulate the output of the amp. This is due to a greater deviation in impedance matching between the source and the load.
Since the driver should only respond to input fed into it, and the amp can't load into the driver efficiently at resonance due to what is effectively a high vswr, performance is reduced and signal reflections are increased. At this point, the driver / vent itself is contributing its' own "sonic signature" / non-linear distortions to the signal path. After all, you're not putting in as much power at resonance due to an increased impedance mismatch, so why should you get equal or greater signal out? This is not to mention the phase shifts that take place at or near resonance(s), so why would you want to introduce yet another resonance via a vent of some type to the system when you've already got one major resonance to deal with on a sealed system?
In effect, the amp is NOT controlling the driver at resonance, it can't load up and the driver is running away in self-oscillation. By maintaining a more linear impedance across the passband, the amplifier loads in a more linear manner, the driver responds in a more linear manner and power transfer, which is a direct measure of the amount of "control" or "influence" that the source has over the load, is improved.
For those that are not technically inclined, let's put it this way. If i push you two inches and you move two inches, that is linear input and output. As such, i have "control" over how much motion takes place, regardless of how far or hard i push. Now if i pushed you one inch and you moved four inches, i am no longer in control of the motion involved and the reaction to input is no longer linear. Such is the same with the amplifier / speaker interface at the point of uncontrolled resonance.
"As far as a sealed box versus ported box, it's easy to optimize both. I had trouble at first, but it's not a problem any more. Like one of my old college math profs used to say, it's the first few thousand integrals that are the hardest... For a seasoned professional, working out a bass alignment should be child's play. If it's not, then I'd take the other more difficult aspects (crossover design, or even more difficult driver design) with a block of salt."
From my point of view based on the examples that you've provided and the lack of common understanding displayed here, i would not want you designing a crossover for me.
"Passives are often quite superior to ports, especially in terms of linearity with SPL. Compression in a port is a serious issue; compresison in a PR is easy to control, as it's just linearity of suspension Cms and Rms over excursion. And both of those tend to be a lot more linear - and much wider in terms of effective pressure output - than a vent. Vents are considerably lower cost, though, and that is why they are so often used."
While i agree that a PR ( passive radiator ) can be more linear than a port in terms of dynamic compression and linearity, much of this has to do with the lack of understanding of ports and the geometries / configuration. Major advances have been made in terms of both the max flow of a port while also improving / maintaining ( or at least trying to ) velocity of said flow through the port at various spl's.
Having said that, both designs introduce their own drawbacks into the equation. As previously mentioned, a port is nothing more than a window to the world for the out of phase back-wave of the driver above the point of its' own resonance. At low spl's where port velocity is minimized, this becomes more of a problem. Since there is less flow through the port introduced by active motion of the woofer, there is less restriction for air to flow both in and out of the box. While, and as mentioned above port technology has improved in these regards, this can be reduced by using smaller ports to maintain velocity or "pressure" in the ports, the problem with limited port capacity comes into the picture. The end result in most cases is dynamic compression and port noise or "chuffing". In order to get around this, you have to use a bigger port capable of more flow, but then you are back to square one with reduced velocity. As such, one typically "picks and chooses" their poison in terms of max flow capacity and flow velocity and designs for a specific spl range / amount of air flow through the port. The end result of such a design is that bass linearity is optimized over a narrow range and sonics suffer both above and below that range. Hence the common occurance of "these speakers have no bass until you drive them" or "the bass sounds congested at higher volumes". Since a sealed box maintains constant pressure within the box and the amount of damping applied to woofer excursion remains constant, you don't have these problems with a sealed design.
Where one can drastically reduce these compromises with a port is to use a port that allows a greater amount of flow while maintaining port velocity at lower spl's / air flow. By radiusing the bends at the inlet and outlet of the port, air flow is neither restricted nor slowed down. Just like driving a car and going into a sharper turn, you must slow down quite noticeably in order to navigate such a sharp bend. Air does the same thing going into a "flat" port due to the lack of radius involved. By flaring the radius / entry way into the port, this is much the same as providing a wide turn with a bank to it. Just as you can "hammer down" into a turn of this sorts, so can the air entering or leaving the port. Flow velocity is maintained in a more linear manner due to less pressure drop / consistent speed of flow. While you still have the potential for reverse flow of the backwave from the out of phase woofer signal, this is drastically reduced. At the same time, port linearity is improved AND the sonics produced by such a system ( if properly designed and implimented ) remain much more consistent over a wider spl range. As such, if you are going to use a port, make sure that you use a "flared" or "radiused" port for best results. Now, onto the drawbacks of a PR ( passive radiator).
Rather than just using pressure through the port to push the air, PR's use a drone cone ( driver with no active motor structure ) to do much the same thing. There are some major differences here though even though both designs work by putting the out of phase signal from the back of the woofer to work.
One of the major differences between a port and PR, as Dan mentioned above, is that passive's do not suffer dynamic compression anywhere near as badly as most "conventional" port designs do. Since you can only flow so much air through a small hole / tube ( port ), it runs out of surface area and compresses / distorts the signal. By using a drone cone of equal or greater surface area* to the active woofer, the drone cone is capable of moving as much air ( or more ) as that of the woofer driving it. This in itself is a big improvement in terms of linearity and "functionality" when compared to a port, as PR's tend to produce more consistent sound regardless of spl's involved.
As one might guess, the PR also gets rid of a large portion ( but not all ) of the problems with a port in terms of out of band high frequency leakage. This is because a PR is sealed and no longer offers a direct "window to the world" like the open hole of a port. Having said that, a PR does contribute sound at frequencies other than that of its' main tuning due to what is called "sympathetic resonances". Just as other things in your room vibrate / resonate due to the moving of air, especially at higher spl's, so does the PR. This occurs to a much greater extent though as the air is not only acoustically coupled via the sound waves, it is coupled via the internal pressure of the speaker cabinet. As such, ANY movement of the woofer, regardless of frequency, is both acoustically and pneumatically coupled to the PR, causing it to respond in equivalent or near equivalent excursion. This is where we start getting into other problems i.e. due to "coupling" and the actual mass of the drone cone.
As mentioned, a PR uses a cone whereas a port uses the air. The port works as a Helmholtz resonator i.e. blowing across the top of a bottle produces a resonance. The only mass involved is that of the air. With a PR, you've got the mass of the cone to deal with. By altering the mass of the drone cone itself, you vary its' point of resonance or "maximum output due to sympathetic resonance". Since one can add a great deal of mass to such a cone i.e. FAR more than what air weighs, one can tune a PR for extreme bass extension and achieve better results than that of what you get with a port. But like anything else, added mass introduces another "variable" into the equation.
As mass is increased, it becomes harder to move. While this in itself can reduce the "excitability" of the drone cone at higher frequencies and help to minimize "out of band contributions", it also takes longer to respond and recover from direct and more forceful input i.e. larger low frequency excursions. It is this "lack of response time" or "lag" that gives most PR's "greater apparent bottom end weight", but also poorer transient response. Remember, the port only has the weight of the air and the PR has the mass of the drone cone.
What happens here is that, as the active woofer moves forward, the pressure inside the box is altered and that pressure change causes the PR to "suck in". When the active woofer recoils on the return excursion, it changes the pressure inside the box again, which causes the PR to push out. In effect, the PR is an "internal pressure regulator", BUT, it can only respond to a pressure change AFTER the active driver has already started in motion. Otherwise, their would be no internal pressure change in the box and since the PR has no active motor of its' own, it would sit still. As such, the drone cone is always trying to play "catch up" in terms of equalizing the internal "air spring" or "internal pressure" in the box. As a side note, sealed boxes maintain a consistent "air spring" in the box since the only thing that can "relieve internal pressure" is the cabinet itself flexing. Hence, the need for rigid cabinets and increased weight of a sealed design.
Now, not only have we got the "lag" associated with the "tag along" drone cone, we also have the mass of the drone cone to deal with. Not only does the passive mass of the drone cone have to be accelerated when standing still, it has to be slowed down once in motion. Since the drone cone doesn't have an active motor of it's own to do this, it is reliant on the motor of the active woofer to do this. The end result is that a drone cone that is tuned quite low with a lot of mass ends up suffering from increased lag ( heavier is harder to get moving ) and over-shoot ( greater mass is harder to stop moving ). Now think about this and how the passive works in terms of how it is coupled to the active woofer.
Just as the active woofer's motion changes the pressure inside the box, which results in the movement of the PR, what is to stop the greater mass of the PR, once set in motion, from "pressurizing" or "modulating" the active woofer? The answer is nothing. Nothing other than the active motor of the driven woofer. As such, you really need a "over-kill" motor structure on the active woofer if you want to keep it under control.
To put this in "easy to understand terms", look at it this way. You are driving a car that has a reasonable amount of power. You now add a "trailer" aka "U-Haul" to the back end, increasing the mass that the motor and suspension have to respond to. When starting from a dead stop, the "reasonable" motor now has more drag on it, has to work harder and can't accelerate as fast. After trying to do this a few times, you really wish you had more motor to pull the heavier "passive" load that you've got lugging behind you now. Due to the lack of motor, you just can't accelerate like you want or maintain the speed that you want. This is equivalent to using a "weak" woofer and trying to "band aid" it for extension and output with a PR. EVERYTHING suffers and nothing feels right.
In order to remedy this, we install a bigger motor with more power. Now you can more easily whip into action, which in turn pulls the passive load that is in turn responding in like fashion. Now we can literally "jerk" the passive load behind us on fast acceleration. Not only does the motor respond so much more effectively, but now we can really get going in terms of speed. BUT, and this is a whole new problem, we've now got the added mass of the passive load behind us in terms of momentum and it is time to stop. Not only is that added mass hard to stop, especially since we were able to pull it faster, it wants to keep going, causing our suspension to react in an uncontrolled fashion. If the passive load that is attached to us develops too much inertia, that energy will be transferred into our the driven vehicle, possibly even influencing how much control we have over the situation using the motor. Pretty scary to say the least, huh??? In effect, that is exactly what happens in a PR system every time the active woofer makes an excursion.
In plain terms, a PR is trying to achieve the extension of a port ( and even more ) with the tightness via "controlled internal pressure" of a sealed design. The difference here is that you only have the mass of the air to deal with using a port ( internal pressure & external pressure ) and in a sealed box ( internal pressure only ). With a PR design, you now have the added mass of the drone cone to factor into the equation as a variable and added mass ALWAYS equates to poorer transient response and less agility.
To sum things up, WHY would you want to make things more complicated, add mass, reduce transient response, increase the quantities of resonances & phase shifts / reduce power tranfer & output linearity, etc ???? ALL of these take place when trying to impliment a port or passive. There is NO real reason to do this other than if one is willing to sacrifice performance on the whole in order to gain performance in specific areas? As pointed out elsewhere in this thread and in others, vents offer increased quantity of bass at the expense of quality. Anybody that tells you something different has an agenda.
I don't make / market / work for anybody that offers any type of product associated with audio. My only "agenda" is to share & exchange ideas with those that share a common love of music / music reproduction. If another's ideas clash with those of known fact and common sense, i'm going to do my best to both refute those points AND try to learn from them at the same time. That is, IF they have something new to teach. As i've said before, with a little common sense and the help of technology, you can go a long way in audio without spending a lot of money. Most ideas that are contradictory to common sense / common knowledge are promoted in the attempt to get into your wallet or anybody else that will allow them to. Sean
>*I'm not going to go into specifics here, but for optimal performance, the drone cone selected should be of measurably larger diameter than the active driver being used to excite it. In effect, one would use a 10" drone with a 6.5" active woofer or a 15" drone with a 12" active woofer. If using two active 6.5's, you would use a 12" prassive or two active 12's would use a passive 18", etc... Nothing is set in stone here, but you get the idea.
To sum things up, WHY would you want to make things more complicated, add mass, reduce transient response, increase the quantities of resonances & phase shifts / reduce power tranfer & output linearity, etc ???? ALL of these take place when trying to impliment a port or passive. There is NO real reason to do this other than if one is willing to sacrifice performance on the whole in order to gain performance in specific areas? As pointed out elsewhere in this thread and in others, vents offer increased quantity of bass at the expense of quality. Anybody that tells you something different has an agenda.
I guess because some times a sealed box won't work? What if you can't get extension and/or output required from a sealed box, what do you do? Live with it?
It's really not tough to equalize the group delay of a real-world vented box design with an "idealized" sealed box system that can't exist. For example, try to get 87 dB efficiency in 3 cubic feet and an F3 of 20 Hz with a sealed box. Can't get there. With a vented box, it can be done, and you can keep the group delay down below audibility limits.
There's no such thing as a perfect enclosure. I always advocate the easiest solution, but it should also solve the problem...;) Many times, that can be done with a sealed box. Many other times, a vented box does it. And vented box theory and alignments really aren't all that hard.
Dan Wiggins
Adire Audio
"What if you can't get extension and/or output required from a sealed box, what do you do? Live with it?"There are always ways to get there and maintain the quality of signal. That is, IF one is willing to do their homework and spend the money to achieve those goals. After all, if integrity of signal and specific design / performance goals truly are important, one probably wouldn't be willing to accept anything less or compromise those goals.
"Can't get there. With a vented box, it can be done, and you can keep the group delay down below audibility limits."
With my above comment in mind, in effect, what you've stated here is that if one is not concerned about maintaining the highest quality signal and / or is short on funds, a properly designed and implimented vent will get you the increased quantity of low frequency output that you so desire in a reasonable fashion. The end result should be relatively close in performance to an optimally designed sealed cabinet, but some compromises will be made in total performance. According to theory, these compromises should remain below the subjective threshold of audibility.
"There's no such thing as a perfect enclosure."
I agree. Having said that, this "rule" should be universally applied to both sealed and vented enclosures. As such, this is not any more an advantage for one type of alignment as it is a disadvantage for another type.
"I always advocate the easiest solution, but it should also solve the problem"
Sealed enclosures are always the simplest. They typically have far less math involved, lower parts count, greater chance of success, less chance for unaccounted side-effects, etc... If properly implimented with all factors considered, such a design will "probably" solve the problem.
Other than that, i see that you didn't refute any of the above information, so i'll have to assume that the laws of physics still apply and that my theories / teachings abide within them. Hopefully, some of the statements i've made above have challenged your thoughts / beliefs on a few subjects, particularly the importance of a controlled impedance curve / reduced levels of reactance. For the record, it appears that some European manufacturers tend to have a far better level of understanding on the subject than what most American manufacturers / end users do. Sean
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Sean posted: There are always ways to get there and maintain the quality of signal. That is, IF one is willing to do their homework and spend the money to achieve those goals. After all, if integrity of signal and specific design / performance goals truly are important, one probably wouldn't be willing to accept anything less or compromise those goals.OK, so with an unlimited budget you can get there. Fair enough. Now how about doing it at a price that most people are willing to pay? Not many can afford thousands for subs, and many even find $700+ a bit steep. Now how will you get decent output and extension in your sub? Oh, and keep the box size down, too, because lots of people don't want 4+ cubic foot boxes in their rooms.
Sure, if you have no limits it's easy. But that's not really applicable to the vast majority of even the audiophile community, let alone the public at large. At least in my experience, but what do I know...
Sean posted: Sealed enclosures are always the simplest. They typically have far less math involved, lower parts count, greater chance of success, less chance for unaccounted side-effects, etc... If properly implimented with all factors considered, such a design will "probably" solve the problem.
That's a pretty big "probably"...;) There's this little thing called Hoffman's Iron Law, and when combined with a budget, sometimes you have to do other things than a sealed box. And sometimes even if you can get there with a sealed box, you're better off looking at a vented box since it has some definite advantages over the sealed approach.
Sean posted: Other than that, i see that you didn't refute any of the above information, so i'll have to assume that the laws of physics still apply and that my theories / teachings abide within them .
Umm, no. There's so much there, and much of it misguided, that it'll take a few pages to straighten out. However, I'd recommend rather than me writing it all down, that you look at a good book like Fundamentals of Acoustics by Kinsler, Frey, Coppens, and Sanders, especially the part about driver design and operation in cabinets. But here's one part to discuss, right off the top...
Sean posted: Just the opposite is true of a vented design. That is, you have a peak(s) at resonance, not a dip. This is because the driver and / or vent is self-oscillating and is NOT responding to the input of the drive signal in a linear fashion. If a speaker produces a peak ( or a dip for that matter ) ANYWHERE in its' passband, it is responding in a non-linear manner. That is a distortion and it is directly related to a lack of linearity i.e. increased output with decreased drive.
Actually you have a peak at resonance in ANY driver system - sealed or vented. In a vented box you have two resonances with different frequencies, and the system ends up with an impedance MINIMUM at the system tuning frequency. In a sealed box you have a peak at the single system resonance, and that also is the system tuning frequency. But they both have a peak, with the vented box having a minimum impedance at system tuning frequency, and the sealed having a maximum impedance at the system tuning frequency. So that's sentences one and two disproven...
And a resonance means little input is required to get lots of output (in any system, not just drivers) - nothing more. Don't put power in, you don't get power out. Not to mention that the amplifier is actively driving the system. It's not like you push a swing once and then walk away, letting it "die out" on its own. With a driver you actually grab and push or pull the swing, and never release it. The amp is constantly providing current to the driver, and that means there's a proportional force on the driver at all times (BL i is the force, where i is the current, BL is the motor force factor). That's sentence 3.
As far as a peak in response, can you show than an impedance peak translates to a frequency response peak? If not, then it's not an acoustical problem now, is it? Sealed boxes have impedance peaks, and they can have Q <0.7 responses (meaning non-peaked output). Would that mean the system (sealed box) is responding in a nonlinear manner, and have distortion? There's sentences 4 and 5.
And about that impedance peak thing especially about sealed boxes... For an example, take a Shiva, and put it in a sealed 85 liter box. Impedance peaks at 66 Ohms at 35 Hz. Now add a 3" diameter by 12.75" long port to tune to 20 Hz. There are two peaks, the upper one at 37 Hz at 58 Ohms, and the lower one at 11 Hz at 54 Ohms. So the sealed box has a higher impedance peak . According to your theories, the sealed box would have worse transient response!
Oh yeah, the sealed box will have a 40 Hz F3, and reach a peak output of 93 dB linear (16.5mm one way excursion) at 20 Hz (120W). With half the power (60W), the vented box has the same 20 Hz output, but the F3 is 26 Hz. Oh yeah, above 14 Hz, the vented box has less excursion, too. Meaning of course less distortion.
So we see that the vented box has a lower impedance peak, more output for less power input, and less cone excursion for lower THD. All in the same box size, with the same driver.
In this comparison, I'd say the vented box acquits itself quite nicely...
Lastly, you keep insisting that's it's difficult to design a vented box... Modern tools like LspCAD, SoundEasy, LEAP, and others make it actually quite simple. Again, this shouldn't be difficult, especially for a professional. If they can't get it right, nor if they can't afford decent tools, then I'd be quite suspect about the other aspects of their designs. I'd assume this isn't too much of a stretch.
Rather than continuing this endless debate, I'll just wrap up with a single statement:
There is no such thing as the perfect box for all situations. There IS the perfect box for a given situation.
Dan Wiggins
Adire Audio
By controlling the in-box Q of the driver in a sealed system, you effectively damp both the impedance peak and output peak at resonance. This is done by manipulating the amount of self-oscillation of the driver at resonance and increasing power transfer. Since the amp sees a lower impedance, it can now load more power and muscle the mass and reactance of the driver with less hassle. One doesn't see a peak in output and linearity is improved.As far as the specific driver that you chose to use in your comparison of impedance peaks at resonance in a sealed and vented box, the Shiva would not be my choice for use in either and your demonstration explains why. A 66 ohm peak at resonance in a sealed box is both ridiculous and unusable* for high fidelity use. How much power transfer can ANY amp deliver at or anywhere near the resonant frequency with that high of an impedance??? Obviously, it wouldn't be too much.
Since this is both your driver and your calculations, i'll take your word on it and avoid such a combo like the plague. The fact that i had just recommended the Shiva Mk IV to someone to replace another "heavy duty subwoofer driver" that had an EVEN HIGHER impedance peak becomes moot after learning what you just said. Thanks for your honesty. Sean
>*How much "muscle" do you think your "brawny" amp can deliver into a heavy driver with large amounts of reflected EMF? Using a 200 wpc amp rated at 8 ohms, here's a break down of what you would get into the aforementioned speaker at 66 ohms under optimal conditions:
8 ohms = 200 watts
16 ohms = 100 watts
32 ohms = 50 watts
64 ohms = 25 watts
All i can say is that you better get more "juice" or find a driver with a more linear impedance curve.
You refute your own statements and undermine your own arguments in that post several times."In a vented box you have two resonances with different frequencies, and the system ends up with an impedance MINIMUM at the system tuning frequency. In a sealed box you have a peak at the single system resonance, and that also is the system tuning frequency. But they both have a peak, with the vented box having a minimum impedance at system tuning frequency, and the sealed having a maximum impedance at the system tuning frequency. So that's sentences one and two disproven..."
Nothing "disproven". You confirmed what i said i.e. two impedance peaks with the resultant shifts in phase and lack of control in a vented box as compared to one of the same in a sealed box. Thank you.
"And a resonance means little input is required to get lots of output (in any system, not just drivers) - nothing more. Don't put power in, you don't get power out."
Little power in and lots of power out? That sounds like non-linear distortion that most would call "ringing" or "oscillation". And you have two of these points in a vented system and only one in a sealed system?
"Not to mention that the amplifier is actively driving the system."
The amplifier can only drive what it can load into. Increased impedance means a lack of drivability and reduced power transfer. Once again, one increase in impedance with a sealed box and two impedance peaks with a vented box. Which one do you think will offer more control and which will produce more slop ?
"It's not like you push a swing once and then walk away, letting it "die out" on its own."
That is EXACTLY what resonance or "self-oscillation" is. In your own words "And a resonance means little input is required to get lots of output (in any system, not just drivers) - nothing more." One nudge to the "swing" and it takes off like a jet. With a sealed box, you only get one of these "free rides" due to the single impedance peak. Vented box means "twice as much driver non-linearity" due to the twin impedance peaks.
"With a driver you actually grab and push or pull the swing, and never release it."
The "grab" on a driver is directly proportional to power transfer from the amp. If the amp can't transfer power to the driver, it has lost its' grip and is no longer in control. Which design "loses its' grip" more often due to lack of power transfer?
"The amp is constantly providing current to the driver"
While the amp may be delivering current to the driver, it is not doing so linearly at all frequencies. Bare in mind that there is more current flow or "power transfer" at a lower impedance. Hence the lack of power or current flow at or near speaker resonance due to the higher than normal impedances that the amp sees. Reduced current flow equals less control. Two points of reduced current flow for a vented box, one for a sealed box.
"That's sentence 3."
Thanks again for your honesty, helping to prove my points AND keeping track : )
"Sealed boxes have impedance peaks, and they can have Q <0.7 responses (meaning non-peaked output)."
A low Q design will NOT suffer from uncontrolled oscillation due to being critically damped at resonance AND it benefits from improved transient response. Hard to beat.
"Would that mean the system (sealed box) is responding in a nonlinear manner, and have distortion?"
That is part of the design and not a side effect of introducing another uncontrolled, undamped resonance / colouration. In fact, such an approach goes out of its' way to control such things.
"And about that impedance peak thing especially about sealed boxes... For an example, take a Shiva, and put it in a sealed 85 liter box. Impedance peaks at 66 Ohms at 35 Hz. Now add a 3" diameter by 12.75" long port to tune to 20 Hz. There are two peaks, the upper one at 37 Hz at 58 Ohms, and the lower one at 11 Hz at 54 Ohms. So the sealed box has a higher impedance peak. According to your theories, the sealed box would have worse transient response!"
See my above notes in the post directly above this. On top of that, the Shiva is neither "optimized" in a sealed or a vented design as it is a "hermaphrodite" i.e. "universal" driver. As such, it does neither as well as a driver that is fully optimized for one specific type of use. Like many other "universal" devices, one size does not fit all and what it does fit, it may not do as good as an item designed for one specific purpose.
"Lastly, you keep insisting that's it's difficult to design a vented box... Modern tools like LspCAD, SoundEasy, LEAP, and others make it actually quite simple."
Easier said than done. On top of that, this is probably why we keep seeing / hearing products that don't meet factory spec and sound like crap getting reviewed in Stereophile. Too many "speaker designers" putting "garbage in" and the consumers are getting the "garbage out". Having said that, the computers can only get you so far and it is up to fine tuning by ear, eye and test equipment from there. Then again, this would entail quality control with the resultant increase in time and labor and we all know that "high end companies" can't afford to do that with the "very reasonable" prices that they charge audiophiles.
"There is no such thing as the perfect box for all situations. There IS the perfect box for a given situation."
Nope. There is nothing you can do to get rid of all of the standing waves within a cabinet using the "conventional" dynamic drivers that we currently use to reproduce low frequencies and are stuck with. There are only boxes that reduce specific drawbacks to the point of negligibility. That specific point of negligibility would be a matter of perspective and up to personal preference / interpretation. Sean
>PS... For those that aren't speaker designers or technically minded, all speaker engineers try to avoid operating a driver at or anywhere near resonance in order to increase / maintain linearity. As mentioned, drivers become prone to distortion / self-oscillation at or near resonance. This is why we have crossover networks in speakers i.e. to steer the sound away from one driver that is going into a non-linear mode of operation and shift it to another driver that is better suited for linear operation in that specific frequency range. Obviously, how well or smoothly this is achieved depends on the drivers chosen to blend together at that point, the crossover design used and the skills of the speaker designer.
Since we can't avoid the low frequency resonance of a woofer / sub-woofer, all we can do is cope with the resonance and try to tame it as best possible. This is exactly what a low Q sealed design attempts to do i.e. flatten the peak at output while maintaining good to excellent transient response. On the other hand, using a vented design introduces yet another point of resonance, adding further non-linearities and reducing transient capabilities. If this sounds contrary to ALL the goals that the speaker designer has tried to achieve throughout the rest of the speakers' operating range, it is. None the less, it is exactly what audiophiles have been led to believe "sounds good" due to marketing hype, poor listening skills and lack of education on the subject. This is NOT to put "audiophiles" down but more to condemn the "glossy mags". Obviously, they have NOT done their job at educating those that have trusted them to best represent their interests in this field and hobby. Sean
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that you've answered this "common wisdom" question/religion of sealed inate superiority, I just don't know how you still do it with patience.I've grown weary of trying to state, no superior topology/alignment, just superior implementation of topology/alignment.
Good luck and good leads at CES.
C'est la vie! You going to make it to CES? Pick on the Knappster a bit? :DDan Wiggins
Adire Audio
I posed what I thought would be an easy question for you guys and I never got a straight answer. I got bass traps, parametric EQ', EGOS which = Baloney. Nevermind I went elsewhere...........
Some of us have other things going on in life than to sit around and answer questions on the net from you. Sorry we weren't at your beckon call. Sean
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I should have known you had cranial-rectumitis when you asked the question "Are you capable of assembling a "loosely compiled gathering of parts" on your own?" For your information I'm a EE. As for your loosely compiled gathering of parts you can shove them where the sun don't shine.
Your and EE? And your asking for help in interpreting how well a compendium of electrical devices work? And all of these devices have specifications provided so that you can do the math, yet you can't interpret the data for yourself? Figures. Talk about anal cranial rectification. Sean
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You can do all the math computations you like, but there's nothing better than firsthand knowledge....seeing/hearing is believing.
If you had any faith in your skills and profession, you would be able to do all the math and come up with a pretty reasonable idea of what to expect. From there, you could fine tune the design to best suit the specific sonics / design goals that you were seeking. Evidently, you either aren't an EE or have no faith in your own education and / or skills. Sean
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Sean, according to you I guess the bass I am hearing from my Merlin VSMs is neither tight or accurate?Man, what a bummer. I suppose I'll have to let Bobby know that, according to you, his speakers suck.
What a bunch of bunk.
Jim
Vented designs all suffer from poorer transient response than an optimally tuned low Q sealed design. When you have heard such a system and learned how to identify how much more natural this sounds, your perspectives on "good bass" changes. Since the mass majority of "audiophile approved" speakers are vented, the mass majority of "audiophiles" really have no idea as to what "accurate" or "tight" bass sounds like. As such, they've become accustomed to distorted bass that is not accurate and consider it the norm.As a side note, you can't take a small driver that is excursion limited and expect it to reproduce low frequencies at high amplitudes with low distortion. There are trade-offs involved in doing such and Bobby is surely aware of them. I'm sure that he's also aware that his "BAMM" system reduces power handling and increases distortion, all at the same time. None the less, that did not stop him from accepting those trade-offs and marketing the products that he does. Nor did it stop people from buying those products even though they might not have been aware of those facts or know how to listen for the side effects generated by those trade-offs.
Either way, your thoughts, my thoughts or Bobby's thoughts on the subject do not make the sound of that product "tight", "accurate" or "low distortion". Sean
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And I suppose you're the only one out there that does.....
If you are an EE, you would know how to interpret the data for yourself. You would also realize that i'm simply commenting on and passing on techincal information that supports the statements being made. Sorry if i've helped to uncover your lack of professional expertise and / or was stepping on your toes. Sean
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and why you think it adds distortion to the Merlin VSM?I would argue that the BAM module is a major reason why the Merlin VSM is so good AND why it is so accurate. In fact, I would argue that the speaker would have greater distortion and reduced accuracy without it.
Jim
Any time that you introduce a signal that is below the tuning of the vent on a vented speaker, you introduce distortion due to increased excursion. The "BAM" system is basically an electronic equalizer that increases the amplitude of the low frequency content in a manner that reverses the natural low frequency roll-off that the speaker itself suffers from. While this extends bass response, as mentioned, it will also increase distortion. This is especially noticeable as the amplitude of the signals being reproduced are increased.As a side note, this is no different than the approach that Dr Bose took with the bass equilazation circuit that he designed for use with his 901's. Having said that, Bobby might have been smart enough to include a high pass filter in the BAM circuitry, limiting the amount of signal below a given frequency. This would increase the benefits of such an equalization circuit while reducing the potential for distortion. None the less, increased distortion would still be a fact of life.
I would HIGHLY suggest that people interested in learning how speakers work AND saving money pick up a book entitled "The Loudspeaker Design Cookbook" as written by Vance Dickason. Once one can learn and fully understand the info that Vance has so thoughtfully compiled within these pages, one can easily spot flaws in various loudspeaker designs at a glance. Having this knowledge does NOT make you a "speaker know-it-all", but it will make you a much wiser and economically responsible consumer when it comes to various loudspeaker designs. Sean
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Merry Christmas Sean:
I have read the string and have a fews things that I would like to add. I am a fan of sealed enclosures myself. The TSM M (my pedestal mount monitor) uses this aligment to great effect. And, in general, I would have to agree with some of the statements made regarding sealed verses vented alignments. But it is obvious to me that you have not ever listened to, played with or tested a properly set up VSM Millennium system. If you would have, you would not have made some of the assumptions that were made. When the VSM is optimized with the BAM, distortion levels drop due to the filtering of out of band subsonic energy. The decreased distortion is both audible and measurable. Power handling increases by at least 20% depending on the program material. And as far as far as this driver not having any excursion, it has an x-max of 12 mm which is 4.5 mm greater than an 18 inch JBL. I think that it is obvious that conventional vented alignments have considerable issues but the VSM M is anything but conventional. With an Fs. of 28 Hz and a linear excursion of plus or minus 12 mm, this 6.5 inch driver is a real power house. It can easily fill environments of up to 5000 cubic feet with super clean, punchy and articulate bass. It is not designed to fill Madison Square Garden or play below 30 Hz because very few environments can support these subsonic frequencies anyway.
I think that all designs need to be considered on their own merits because it is not enough to say that this is a sealed or vented alignment so it fits into "this" category. The VSM is just one of a number of designs that have played with and manipulated the rules.
Regards,
Bobby@merlin
Bobby: I can't remember the specifics or if it was the current model that you mention, but i have read a technical review of one of your stand mounted monitors that made use of the BAM module. From what i can recall*, bass extension was improved ( 38 Hz without BAM, 32 Hz with BAM ) but distortion also went up. While i don't know if you've refined the design since that point in time, but i'm quite certain that you've done the best that you can working within the parameters that you've chosen to work within.Having said that, i can say with good confidence that such a design would suffer from at least a sizeable impedance peak at resonance. While i don't know the specifics in terms of the impedance values at resonance of your individual design, my guess is that the ability of the amp to load up into the driver at that point is drastically reduced. After all, even a "small peak" at resonance of 16 ohms reduces power delivery potential by 50% as compared to an 8 ohm load. Since a 16 ohm peak would be considered very small / highly desirable for most designs that make use of a port and / or passive radiator, my guess is that power transfer / control of the driver is reduced even further beyond this "guesstimate". On top of that, you've made no mention of the differences that one encounters in transient response between a low Q sealed design and a vented design. My guess is that the differences are not in favor of a vented design.
I do appreciate your response and can see that you've put quite a bit of work / time & research into developing your product. But at this point in time with the knowledge and drivers that we have to work with, you simply can't get the performance that you speak of out of a small driver without measurable side effects. Whether those side-effects and drawbacks are objectionable enough to dismiss would obviously be a subjective matter dependent on personal preferences. Sean
>* statements based on memory that may / may not be accurate, but i think that they are at least "in the ballpark".
Hi Sean:
The TSM M, our pedestal mount speaker does not use the BAM, our floor standing VSM M, does. And at no time in the history of our product reviews did any reviewer make mention of the fact that the distortion goes up when the BAM is used. In fact, as I mentioned before, the exact opposite is true. The reality of this discussion is that all aligments suffer from distortion components but I have found a way to minimize those that are objectionable to the majority of listeners. You have a good working knowledge of design concept but this is not a substitute for working with, testing or listening to an actual item. Until this is done, you provide us all with mere assumption based on someone elses findings. However, based on what you have written, I doubt that you would like my product but not everyone does either.
The true bottom line in being a successful designer is being able to develop a balanced product with as many strengths as one can. One that tends to sound or work more like itself in as many situations and applications as possible. I pride myself in being a balanced thinker and do not allow one aspect of the design to dictate or complicate the outcome. The very most important thing is to be open minded and investigate all aspects of the potential design (without preconception) and follow them through with proper experimentation to determine the planned approach. I have spent 10 years of my life working on this project. You may not like the direction that I have chosen but it works for me.
Regards and Happy Holidays,
Bobby@merlin
Bobby: After responding to your initial comments, i went and dug through my old Stereophile mags and re-read that review. You are correct in several aspects i.e. that there was no mention of distortion readings with the BAM module hooked up, let alone taken anywhere. You were also correct that the review that i read that did make use of the BAM system was your floorstander and not a stand mounted unit.From what i can gather based on the information in that review, it seems to be a pretty well designed product. Having said that, there are several "nits that i could pick", but i won't. You come across as being both attentive to detail and someone that strives to achieve a well balanced design. As such, i can see those attributes in your speaker. I'm quite certain that your products perform quite well, especially given their size and driver compliment.
The one major problem that i do have is the price of these units. While i understand that you are using very expensive drivers in this design, a retail price of $8000+ for a small two way is what makes products such as Legacy look like such a "bargain". Big cabinets, multiple large woofers, several mid and high frequency drivers, etc... all lead up to what most uneducated consumers equate with "value". This is true even though such designs are much harder to integrate into a listening area, let alone get all the drivers to work together as a cohesive package. Having said that, the mid-band performance of the Focus 20/20 is pretty good even though it falls on its' face in the bass and treble regions.
As we can see from the test results, which pretty much speak for themselves, your design has far more thought put into it and this is demonstrated in terms of improved linearity. While i don't think that anyone would believe or expect that your speakers could compete with a floorstanding Legacy in terms of absolute spl's, anything below "rocking the house" would probably make yours a winner. Not only is your design "flatter", it is far more time & phase coherent. The fact that your much smaller speaker is both more linear and has better bass extension is testament to your hard work. On the other hand and if you reverse those comments, it doesn't say much for a design that has GOBS more surface area, much larger cabinet volume and supposedly "faster" ( ribbon ) drivers.
Best wishes to you and good luck with your products. Not only have you demonstrated your skills as a speaker designer, but you've also proven to be nothing less than a complete gentleman. There aren't many folks that can "stand in the fire" and not get burned, let alone sweat. You did that while remaining gracious through it all. Kudos to you and your products. Sean
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Its Xmas, its pissing with rain, I'm between systems, I've sorted out my CDs, unpacked a few more cartons from my 6 months move and hung the remaining pictures.So here I am, back at the Asylum but thanks to Sean here, I'm now going to log off and do something useful, like tidy my garage.
Thanks Sean, for a most nausea inducing post
Sean, thanks for the definition but I know pretty well how it works. And as I thought, you are only vaguely familiar with what is going on with it."Having said that, Bobby might have been smart enough to include a high pass filter in the BAM circuitry, limiting the amount of signal below a given frequency."
You might could say that. Sean, you may wish to take a moment to browse www.merlinmusic.com to learn about this design before offering criticizms of it. Or even search this site for Bobby's comments about the design. Reading that site, OR THIS SITE, will not make you a "know it all" about the Merlin VSM (or any other topic for that matter) but it will make you much wiser prior to offering comments about the design.
With that being said, the speaker is a vented design. It falls into the "low-fi" realm, as you put it. And your comments are a perfect example of what can be so wrong with these sorts of websites. People have to be extremely careful about the creedence they grant certain perspectives, mine included. In fact, I think anyone would be hard pressed to find a speaker more accurate (or musical), within it's capabilities, than the Merlin VSM.
Just my biased opinion of course. (I wouldn't want to concede that I have wasted money on these speakers. Much too big a blow for the audiophile ego.)
Jim
Hi Jim,Sean is right in what he says. I too have ported speakers, they are a trade off. Tubes or SS? Vented or unvented, etc., it is all a trade off. I had considered the Merlins myself. I am sure they are great speakers, but like all speakers, they are flawed. With audio the important thing is to buy and use what makes you happy. I tend to like accurate, but for the money, I could not find anything that went low enough, so I settled, and I am glad I did... Slow bass or not, I am miles ahead of where I was before!
Bet Regards,
Lou
I have heard some complain about the VSM not playing the bottom octave (assuming they even have the room for it) but one thing I have never heard is someone complaining about them not being accurate.I am not saying that a "vented design is always better". But for someone to claim ported designs are a huge compromise or "low-fi", at least as it relates to the Merlin VSM, is absurd. That was my point. And foolish statements like that will steer misinformed people in the wrong direction. I agree that audio, and especially speaker choice, is a matter of personal preference. But in this case I really have to wonder where some people are coming from.
Lou, when did you hear the Merlin VSM and what was the associated equipment? You say, "you are sure they are great speakers" which makes me think you have not heard them. If they have a flaw, I would say they can be picky about associated equipment. Although the "M" version tries to make that easier for people. And if you use the right equipment, the sound is just unbelievable. This design is much unlike any other. It's not just a 2-way ported speaker. If you are speaking from what you think you know about the design on paper then you are missing the boat. You don't know until you have heard them setup properly - especially in this case. I too was a little skeptical of the performance that could be achieved from the drivers in this speaker. That was 4 years ago. I have them in a 13.5 x 24 room and have no need or want for a sub. They fill the room with music.
Jim
Hi Jim,I did try to hear them, but the fellow who used to carry them in Chicago droped them... I know, I know, I have not heard them, yet I do believe that they would have a hard time being much better than the Taylo Reference Monitors, or the Ellis Audio 1801b's which is what I finally went with after a lot of research. Have you by chance heard either of these? They are all vented, thus all suffer from slower then acoustic suspended types bass. If they could make perfect drivers that also droped off @ 6-12DB at each others crossover points, eleminating the need for a crossover, they would still be a compromise because they are slow, they are cones. If one wants to consider them lo-fi, well, let em, you don't have to agree with their definition...
Best Regards,
Lou
Hi Lou, I have read about the Ellis speakers but I have not heard them. I suspect I would really like them. And I suspect we have similar tastes in speakers which leads me to believe you would very much like the VSMs. There are a few difference though that I think are really important, especially with you compare something with as similar a design as the Ellis to the VSM. #1 the VSM plays a good deal lower. In my case it plays low enough so that I do not feel the need for a sub. Perhaps you don't feel the need either. But I am sure you wouldn't mind them playing lower if they could. Without the BAM unit in place I would not be satisfied with the VSM and I would not own them. (And hence, nor the Ellis). The BAM is a make or break thing for me on these speakers. In my opinion it makes the VSM the "perfect" speaker system, for me. The BAM does not just enable the VSM to play lower, but just as importantly, it makes it play cleaner because it filters out subsonic frequencies. The woofer is able to detail that midrange just that much better because it is not trying to play 20hz - which makes all the difference. Imagine how good your Ellis speakers would sound if they didn't have to be fed subsonic frequencies and had a little bass boost to fill out the bottom end? AND... had a mass loaded cabinet filled with sand as a launching platform? Some may be skeptical of something like the BAM but it really gets out of the way in the system.#2, the cabinet. The loading of the cabinet and changes to footers (placement and positioning) make a big difference. I can't help but think the Ellis speakers would benefit from that as well. I am sure you have them on good stands though.
The VSM is small, and plays low enough so I don't need a sub or the hassle of integrating one. It utlizes small drivers that start and stop quickly, and it is a 2 way design that, with the help of my OTL amp, absolutely knocks the midrange out of the park.
If you ever get the chance to hear them setup correctly you should check them out so you have a point of comparison. They are the sort of speaker that will drop your jaw to the floor. At least they did me when I heard them setup correctly with the right components feeding them (very important).
Best wishes,
Jim
Hi Jim,Well, I am thinking of moving on, because I want it all. :-) I am thinking of going with a 4 way dipole. Hiqupons, Morel 2 1/8" mid domes, Seas Excel mid base, and something like the NHT sub, a sealed design... The Morels image like mad, though I have a hard time imagining it much better than I do now, other than low tighter bass. That is my real goal, but I have always loved Estats, though not the deminished bass or dynamics. It is all a compromise...
Best Regards,
Lou
Now that is the sort of setup that would have me scratching my head trying to make it perfect. If I ever replace the Merlins it will likely be with Soundlabs.Take care,
Jim
Well, the Ellis Audio 1801b's replaced Acoustat Spectra 3300's, but Sound Labs are a little rich for my blood. :-)
Try looking at the link that Richard provided above. For your convenience, i've included it here.
Once you get done reading the text and looking at their test results, you'll see that a sealed design has far less group delay / ringing ( four times less ) than a ported design. It is therefore FAR "tighter" sounding and measurably more "accurate" than a vented design, active equalization or not. Don't even think about passive radiator designs as they are like turtles compared to either sealed or ports. In this case, well designed ports ( almost a contradiction in terms for most designs ) are the "lesser of two evils" by a long shot.On top of all of this, sealed designs maintain a lower impedance peak at resonance. This allows the amp to load up / control the speaker in a far more linear manner. Most vented designs have HUGE impedance peaks ( plural, not just one peak ) and therefore not only "ring" more naturally, but are less controllable at the same time. Sean
>PS... I didn't mean to hurt your audiophile ego, i was just trying to state facts and educate those willing to learn.
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