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I am old enough to remember the sixties when the acoustic suspension sealed box speaker was first introduced by AR. The design had a number of merits:
1) response into the 20 hz range from a medium size speaker
2) a slow rolloff in the bass rather than a sharp hump and falloff
3) measurably much lower harmonic distortion.
4) better bass impulse response - a ported design, according to John Dunlavy, cannot decay more than 3db per cycle. Working out the math, a 60 hz plucked bass guitar note at 90db will take 30 cycles - half a second - to decay. That ought to be audible.
From the early 60s through the 80s the acoustic suspension design was the only choice for makers of quality box speakers. The rivals were large horn designs and transmission line designs a la I.M. Fried.
But in them mid-90s it seems everyone went over to ports. Ported speakers will play 3db louder for equal wattage, and a customer base that listens to rock and heavily electronic music might not notice, or might even enjoy, the gratuitous bass output. It seems the industry press cooperated too: Despite taking many sophisticated measurements, measurements of bass harmonic distortion - once a standard review feature - are rarely seen nowadays. Might the reviewers be protecting someone? What good is a flat bass if much of it is higher harmonics pretending to be bass? Anyway, is there any rational explanation for this changeover or is it just the idea of getting an extra 3db from the amplifier - seemingly a poor rationale for a "high end" company.
Follow Ups:
Peter,
This is from Roy Johnson, the designer for Green Mountain Audio speakers. Allow me to share a perspective of many years' experience in retail and then in loudspeaker manufacturing.
During the 1960s, most woofers still required large boxes, ported or 'infinite baffle', even though Acoustic Research (AR) had already shown what was possible for a small sealed box. As the decade progressed, we saw KLH, KEF, Leak, and finally Advent validate Villchur's work (of AR) on sealed boxes (I am sure to be leaving out some).
At the end of the `60s, the impact of stereo on the (USA) market encouraged firms to make better use of the now-available ported-box and sealed-box formulas, in order to produce more 'bookshelf'-size models (which were less expensive, since they were smaller). JBL chose to produce their ported 8" 2-ways and then their ported L100 model, to satisfy their goals of sensitivity and max SPL. For firms entering this expanding USA marketplace, that generally meant they designed around sealed boxes, for their smaller size and audibly better bass-tightness-- models from Infinity, Celestion, Mitsubishi (Diatone), Yamaha, Dahlquist, and Epicure (and Bozak?), followed later by ADS, Allison, and Genesis, to name many of the largest-selling manufacturers.
During the early `70s, we also had the influence of Bose's 901 with its active EQ, the Servo-Statik's bass-module design from Infinity, and JBL's 212 3-piece system. By the mid `70s, passive radiator design was also understood and a few companies went in that direction, at least with some of their models.
However, during both the 1960s and `70s, I witnessed that a speaker's bass tightness affected someone's purchase decision much less than did the speaker's overall tone balance and its clarity, as those were where the large differences lay. Imaging was something yet to be sought out (other than by those already exposed to Quads or other electrostats).
In the late `70s, imaging became more important thanks to the efforts of Harry Pearson and J. Gordon Holt. To that end, we started to see slimmer cabinets, taller too, which then made speaker stands unnecessary (not even used until the mid to late`70s)
By the end of the 1980's, home theater became possible, and its growing market influence caused many different speaker-solutions to be offered. At first, the goal of a manufacturer was to produce very-small boxes, which had to be ported to produce sufficient bass (regardless of its quality). Later, tall towers with multiple smaller woofers (usually ported also) were offered as the logical step-up from small boxes, at least to the majority of audio customers. Here I am writing only of what most of the USA public could readily hear on the market, as regular stereo-stores were quickly being replaced by mega-stores, where brand, price, and 'new technology' counted for as much or more than 'the sound' itself.
When Dolby 5.1 finally took hold in the '90s, we saw the introduction of subwoofers-- even less reason to buy 'big' speakers, again, as far as folks who spend well-under $1000/pair for any one pair of speakers-- the sales which drive the largest companies such as Infinity, B&W, and Paradigm.
Today, the concept behind using multiple small woofers falls away with the more expensive audiophile speakers, and we see most designs rely on only one woofer in the cabinet. The reason to go back to one woofer in the pursuit of higher fidelity is rather simple, as Presto has pointed out below: One large woofer can be made to have a frequency response that goes lower, naturally.
This is because one can only make any woofer's suspension so soft before it falls apart, and therefore a small-diameter woofer does not have a heavy-enough cone to produce a naturally-low self-resonance (unless you want to throw away a lot of sensitivity by using a really heavy cone/voice-coil assembly on that small woofer, which is what Phil Jones does).
And that one larger woofer may still be ported, because that does increase the speaker's overall sensitivity-- not because of that port, but because the port keeps a woofer from stroking, and this means a woofer's voice coil does not have to be wound as long. A short voice coil weighs a lot less, reducing a woofer's moving mass by a significant amount, lifting the woofer's output by several dB.
More sensitivity is now important to two types of designs-- ones that use the 'high-tech'-appearing higher-order crossover circuits and those that use heavy plastic cones. High-order crossovers, and frankly, ANY passive circuit crossing over below 200Hz, eat up a lot of the woofer's signal, which reduces sensitivity (and damping factor, which is why many require an amp with a big power supply).
The idea of a ported design perhaps being more 'open-sounding' in the middle ranges, as Duke suggests, is I think related to his woofers also handling the voice range, where any reduction of stroke on bass notes is a good thing. Just speculating-- Hi Duke!
Anyway, after designing many sealed and ported designs for several decades now, I can say that sealed always sound better, especially if the crossover circuit is not getting in the way, if the boxes for both are constructed equally well, and if the woofers themselves have the right kind of suspension. Remember, we are asking a sealed woofer to stroke farther and for that, 'the right kind of suspension' is one that allows clean movement on very small signals and on the very large ones. The latter is now easy to achieve, while the former is offered by only a handful of woofer-driver manufacturers, and expensive, such as those found in Scanspeak's line.
So why do we not currently offer a sealed design? Because in today's 'medium-price' high-end market, size still matters, and no one is purchasing a physically-wide speaker, especially in Europe. So my current models are ported with the lowest useful Q. The sonic penalty is now small, compared to what I hear from the best sealed-box design: The port makes the lowest bass a little 'sloppier'-sounding, for any type of bass impulses that happen NEAR the port's tuning frequency. So best to tune the port as low as possible, to get it out of the way of as much of music's tones as possible.
The overhang is not so much a matter of a longer 'group delay' in the bass of a ported speaker (which is a complete misnomer for what is happening with the port's output), as it is the Q of the port's tuning-- which describes how much overhang will be produced by the port after each note that occurs near its tuning frequency.
While that overhang can be made small, it is still audible, but far more audible is what happens to tones near the port's tuning frequency: By definition, ANY resonance always drags nearby tones up or down to its frequency AFTER the input tone (stimulus) has stopped. So, pitch definition can suffer (the dreaded one-note bass being the most flagrant example) along with the pace and rhythm of the performance. Again, a reason to keep the port's tuning as low as possible.
But a port tuned too low makes a little woofer stroke quite far on its way down to that port frequency, and also its output will dip before the port kicks in (because you are listening ten feet way). And that makes speaker-placement more critical, to fill in that middle-bass tone-range with suitable reflections off the wall behind.
Multiple small-woofers 'fix' that issue and provide mucho impact (from their greater 'radiation resistance'- a good thing), but at the expense of low-level signal resolution (caused by each woofer moving less which exacerbates the natural 'stiction' of their suspensions, whihc prevents their cones from moving properly on small signals).
Multiple woofers also create unusual standing wave patterns in a room (from their radiation patterns being different at each frequency). They also change in tone balance relative to the midrange as you move away from them (because their radiation patterns at each frequency do not match that of a single mid).
So, its a big complicated mess, and for any speaker design to be small in footprint, we are not likely to see a resurgence of sealed woofer boxes. I hope I have not created more questions, but let me know if I can explain anything more clearly.
For the record, I do agree in large part with several folks' experiences and comments below, including those of Presto, Duke, Morricab, caspian, Audioquest, hahax, and John Marks. Thank you for your contributions to this thread. Perhaps the one AA thread that has not deginerated to name-calling!
Best regards,
Roy Johnson
Designer
Green Mountain Audio
I am thinking of getting Magnepans but am worried whether the middle priced ones will give me tight bass.
Maggie bass is dipole tight.
That sounds silly but that is the reason.
Back in the day there were lots of acoustic suspension designs with the all-too-common 12" woof, 5" mid and tweeter. The cabinet width for a 12" (14-16") resulted in the design easily achieving the requisite box volume for a sealed box design, which is higher than that required for ported.
Along came "tower" designs which were thinner. Dual 8" woofs and even 7's were used. Then 6-1/2" and even five inchers. 10 or 12" drivers were side firing or found in a separate sub or plain non-existent.
So here is my theory: First, as you get into smaller and smaller drivers you get less and less favorable sealed-box bass performance. It's a lot easier to built a sealed-box 12" than smaller drivers. I think a big factor is the basic Fs of the driver. It's relatively easy to get a 12" driver to have an Fs of 20-25Hz. Try that with a 6-1/2" driver. Or a 5" driver. This is why, IMHO, the port became a necessity - to get some semblance of low bass out of smaller drivers in the popular thinner cabinets. This is also why the use of side-firing woofers became popularized, and even moreso the use of a sub.
Myself, I would rather have a sealed box design that rolls off at a predictable sealed-box rolloff, augment that with an active filter, and use a single ported sub.
To me, having a ported sub and a ported main speaker is to have far more complexity in the low end than is desireable. Too much phase distortion and other issues. Not even subs need to be ported anymore as well. One could have an all sealed box system, get wickedly low bass, and have optimum pulse response and no port-induced noise or phase distortion.
I think ported designs are over-rated these days. Especially now that we have subwoofer drivers that offer serious performance in a sealed box.
Sealed box subs sound more musical to me anyways. The imrpoved transient response is quite audible IMO.
Just my $.02
Cheers,
Presto
"Sealed box subs sound more musical to me anyways. The improved transient response is quite audible IMO."
I read a paper in the Journal of the Audio Engineering Society that investigated the audibility of group delay (transient distortion) on the order of what we would find in a decent vented box. Group delay was found to be barely audible on test tones, but not audible on music program material. This implies that a subjective preference for sealed boxes is probably not caused by their superior bass transient response.
In a home listening environment, the room itself is a huge factor in the perceived bass. Because of boundary reinforcement, rooms tend to boost the low frequencies. The deeper we go in the bass region, the more room boundaries will be within 1/4 wavelength of the speaker and the more bass reinforcement we get. A term that some writers have used for this is "room gain", and I've seen charts created by two different authors which suggest that typical room gain is +3 dB per octave below 100 Hz or so.
A vented box tends to be "flat" anechoic down to a much lower frequency than a sealed box, while the latter tends to have a more gentle rolloff characteristic. Factoring in room gain, a vented box that is "flat" to the 25 Hz will be +6 dB at 25 Hz in-room, which will sound bloated and slow. On the other hand a sealed box that's gently rolling off to -9 dB anechoic at 25 Hz will be -3 dB at that frequency in-room, and will sound quick and tight. In other words, the net result of vented box + room gain is likely to result in excess bass energy which is perceived as poor transient response, while the net result of sealed box + room gain is not.
I'll admit that the above is a rather extreme example, but the principle it illustrates is valid. And relative to group delay, differences in the in-room frequency response are vastly more audible.
So I don't dispute your observation, Presto, but the actual cause may be something else.
Ironically, achieving an un-equalized response that is the approximate inverse of typical room gain is easier with a vented box than with a sealed box. I've been doing it for years, and I'm sure others did so long before me.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
What about energy storage? Most vented boxes have a Q of 0.9-1.1 (gives a fat underdamped bass) whereas the optimal sealed box design has a total Q of 0.6-0.707. The higher the Q the more energy storage and the longer settling time a system has.
I used to have the Infinity IRS Beta, which had separate bass cabinets with 4 12 inch woofers per side in a sealed box. These were servo controlled by the use of an accelerometer on the voice coil of one woofer per box. The signal was sent to the "brain" that compared the motion with the signal and applied a corrective signal to make the bass match the signal. Now, one of the cool features was a Q control that allowed you to adjust Q from about 1.2 down to 0.5 or so. The difference in the bass quality was shocking (now remember this is in a sealed box so it is purely electronic control) and went from loose/bloated at the highest Q setting to techno beat tight at the lowest Q. Not surprisingly, the optimal Q came around 0.7 and this gave a tight yet well rounded bass. Optimal sealed boxes always shoot for this goal. I know of very few vented systems that come close to a Q of 0.7. I don't know this for a fact but by listening I would guess that the Wilson Grand SLAMM MkI had a Q closer to 0.7 as it is quite tight and fast sounding for a vented system.
Notes sound slow when energy is built up and sustained for (relatively) long periods. Bells have very high Q values and as you know they store and reradiate energy for quite some seconds and in a narrow bandwidth. Vented systems with a high Q tend to sound "one notey" for the same reason.
Even though, as the other knowledgeable poster pointed out to me, the port means more variables. (Albeit a variable that can be reasonably approximated by computation.)
A vented design offers more degrees of freedom so in that sense it may be easier to meet my performance goals with a vented box, but at the same time the variety of choices to be made in optimization multiplies along with the opportunites for screwing up.
With a vented box there are more things I have to watch out for: Port airspeed; overexcursion from out-of-band signals, port tube resonances; finding room for the port (sometimes not as easy as it sounds); greater sensitivity to variations in driver parameters within a normal production run; less leeway with where damping material can go inside the box; greater sensitivity to minor air leaks in the enclosure and/or drivers; taking into account where the ends of the port will be relative to drivers, cabinet walls and braces, and room boundaries.
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
I sold AR (decades ago). The EV Interface A (1974) was a smaller, much better sounding speaker. It also played louder at 30hz, and was more efficient. It was a 6th order design. I still have a pair in my livingroom (the cabinets are a bit beat-up).
The B&W 800 series are a more modern example of a 6th order design that audiophiles will recognize (I also sold B&W).
one of the most sensible things ever created - 1-2.5 watt tube folks might not agree (?)
. . . like those originally used by Vilchur and Kloss, seem rare to nonexistent any more. These typically had small magnets and floppy suspensions, relying upon the air spring of the cabinet to maintain control of the cone, and worked well in a sealed enclosure much smaller than the big reflex or horn boxes of the era. They were also way inefficient, and required gutsier SS amplifiers to reach a decent SPL.
Nor are there many drivers available that are optimized for sealed boxes. Audio Concepts used to have a nice line of woofers, ranging from 5" to 12", intended to work well in sealed enclosures with a Qtc from 0.5 to 1.1, but they went out of the DIY supply business over ten years ago. Dynaudio had some, but they likewise are NLA to the hobbyist/small OEM market.
A larger OEM could of course have sealed box drivers made to spec by one of the big manufacturers, but would have to order a minimum run of around 1,000 pieces. And since the whole market these days seems to favor reflex alignments, there is little incentive to do so.
In all of my years as an audio addict, I always seem to prefer sealed enclosures, especially for subwoofers. There are great ported speakers as there are great sealed ones, but when I do my listening tests, I listen for a similar bass note that exists as a kick note, this can be found on Aerosmith's Rats in the Cellar or Fleetwood Mac's Dream's, most profund bass notes I ever heard were on systems that had sealed enclosures or used sealed subwoofers. Having experienced for myself what I am describing, I would probably continue to add a sub to the equation to any ported design speaker I own.
Ciao,
Audioquest4life
"From the early 60s through the 80s the acoustic suspension design was the only choice for makers of quality box speakers."
Bullshit.
Apart from the sort of advantages of reflex designs which present themselves as apparent advantages quickly to a typical consumer, I have heard that sealed systems are harder to design. Seems counter intuitive that that would be the case.
They are easier to design. You need a few specs on the driver(Vas, Qts, free air resonant frequency). Pick a Q for the system and there are tables out there that are very simple to use. Bass reflex is way more complicated because the port adds another variable and a computer program is really needed for proper design control.
All in good fun.
No, as far as I know, I am not "protecting" anyone. What makes people say such things? Have you tried reading what I write?
I have mentioned the theoretical and in some ways practical superiority of sealed boxes many times over the past five years, which is about the time I woke up to the fact that most audiophiles had only been exposed to ported designs. I attach a link to my overview of the subject.
In addition, I have quite recently gone out of my way to praise sealed box designs from Aerial (5B) and ATC (SCM 11). And JA's measurements have validated my subjective reactions.
The overview was a sidebar to my review of a $40,000 sealed box design, that perhaps would have cost half as much as a ported design.
Nobody here but us chickens, I guess.
To attempt to answer your final question, I think it is more likely that the commercial motivation is that a ported enclosure can be roughly half the size of a sealed enclosure with the same subjective bass output. Whether you call it room friendliness or spouse acceptance factor, it is a very real sales factor and cost factor, everything from the packing boxes to storage space.
In the early 1980s, Duntech Sovereigns (from Mr. Dunlavy's former company) were the #1 speaker in NYC mastering rooms. They are now no longer imported into the US. Weight, bulk, and cost, not 3 dB more efficiency, which is kind of a non-issue in an age of digital amplifiers, explain that, IMHO.
JM
You surprise me, John.
I spent some time evaluating the Sovereigns about 25 years ago, in consideration of buying them. To me, they were remarkable in many respects, but they consistently made violins into violas, as if adding a chest register.
Might have been the room, I suppose, but in the event I kept (and still use) my Spendor BC3s which sound more mid-range neutral. Not much chance of boomy bass with those bass-reflex speakers, mind.
Jeremy
Pardon me while I put on my "manufacturer" hat. Here are three arguments in favor of a vented box:
First, in a two-way design, the woofer's performance in the region of the crossover frequency is of paramount importance. If we're going to ask a cone woofer to go up fairly high (I take 12" woofers up to 1.5 kHz ballpark), the cone better be light and the motor strong. Now it just so happens that woofers with light cones and strong motors generally do not give adequate bass extension in a sealed box (not even my 12's). So if we don't want to add subs, a vented box is called for.
Second, for years I assumed that a sealed box had better midrange than a vented box, but a couple of years ago decided to find out for sure. I build two test speakers, one ported and one sealed, but otherwise identical. I then conducted a blind listening test, instructing the listener to focus only on the vocals. In every trial the listener preferred the vented box. I have since learned how to make a sealed box that is comparable to a good vented box in midrange clarity, but it's more expensive to do than a plain old vented box.
Third, seldom is the acoustic environment in a room exactly right for a given speaker in the bass region. With a vented box and a bit of ingenuity and/or courage, it is possible for the end user to change the shape of the speaker's bass response curve and improve the in-room response.
Just for the record, it's been years since I read John Dunlavy's critique of vented boxes but my recollection is that he chose a rather boomy vented box alignment to compare with, and unfairly characterized all vented boxes based on this example. Likewise, I could chose a Qtc = 2.0 sealed box and thus make sealed boxes look bad.
All that being said, I use both sealed and vented enclosures in my own designs. Depends on the specific application.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Ultimately a closed box(welldesigned, of course) has better control of overhandg than a vented one. But I do think most of vented boxes are made to sell to unsophisticated listeners and are conciously made a bit boomy. That isn't nedded. A bessel function reflex design is quite well controled and definitely no one note. My speakers are so designed. Then agai they were also designed to have the port stuffed(for rooms where the reflex design which went into the low 20s would boom). And the bass is more articulate that way.
There is one more factor. Reflex is king in sales. So the speaker manufacturers design most woofers for that application. A woofer needs to be designed for one application or the other idealy.
I'll add one other point. I asked the TAD speaker designer why he chose a reflex loading since he could have drivers designed for him to his specs. He said he could easily go about 10 Hz lower with a reflex and down to the point where the closed box went the reflex was just as good quality wise but with the extra extension. He's a great designer so I have to respect his opinion but I'm honestly not convinced(given my more limited exposure).
Thanks for posting, hahax.
I agree with your observation that most vented-box speakers are made to impress the uneducated, especially if the audition is a short one.
While it's true that a sealed box has better time-domain behavior, I'm not convinced that's of audible significance in and of itself. Group delay on the order of what we find in a good vented system hasn't been shown to be audibly significant on music in blind listening tests, whereas frequency response definitely is audible. I think the subjective differences between sealed and vented enclosures are primarily a function of the in-room frequency response, and in general the rolloff characteristics of a sealed box are a better match for "room gain" due to boundary reinforcement in most rooms. But it is possible to tune a vented box to mimic the rolloff characteristics of a low-Q sealed box (or maybe an even shallower rolloff) and in that case it sounds tight and fast. I don't recall what sort of slope a Bessel tuning has, but from your description I'd bet it's on the gentle side.
I'm doing some prosound work, and if one knows in advance the bandwidth of the signal the speaker is going to see, an appropriate choice of tuning frequency can significantly increase the excursion-limited power handling in comparison with a sealed box.
I presume the conversation you describe was with Andrew Jones of TAD. If I had a storefront, I'd want to carry his speakers... whether they're vented or sealed or stuffed with fresh cow pies, they sound great.
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
"But it is possible to tune a vented box to mimic the rolloff characteristics of a low-Q sealed box (or maybe an even shallower rolloff) and in that case it sounds tight and fast."
True, but this is so rarely done and in the end kind of defeats the purpose of what the vented systems supposed advantages are. A sealed box is MUCH easier to design AND execute correctly (there is a lot of forgiveness in the dimensions and still get quite close to the right result).
Other than one or two vented speaker systems I have heard none that compare to a well designed sealed box bass system or large flat panel for that matter. Remember the NHT 3.3? It had a 12 inch sealed woofer system and gave prdigious tight deep bass...one of the all-time greats in that category. NHT's SW3 was using the same woofer and was a world class sub.
Bessel function is minimum time delay. In a closed box a bessel function is a Qtc 0f 0.577.
Yes it was Andrew Jones and my impression is he's one of the elite speaker engineers(I said engineer rather than designer because I believe he measures as much or more than he listens so his biases are minimized).
"I agree with your observation that most vented-box speakers are made to impress the uneducated, especially if the audition is a short one."
That is a subjective statement based on prejudice if I ever saw one. Companies like PSB, Paradigm, Energy use NRC's facilities along with true DBT listening tests to get the sound they are looking for. There are countless many other speake companies who use anoechic chambers as well to tune their speakers to achieve the flatest response possible. Far more impacting to a way a speaker osunds than ports are crossovers. So before dumping on the ports as the cause of the problem, look at the cross over used.
I was talking about speakers not aimed at the audiophile market. For example, Best Buy moves far more speakers than brick-and-mortar stores carrying the likes of Paradigm. Their target audience isn't audiophiles, but rather "the uneducated". And boom-n-sizzle is more likely to impress in a 30-second audition.
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
While I prefer a big sealed box (something like 30 square foot is close enough to being infinite for smaller drivers) it is not a black or white choice.
A normal size bassreflex system can i.e. be tuned to 35-41 Hertz and thereby reduce the cone movement a lot. This will reduce distortion compared to a same size sealed box.
Secondly the port does give a more open sound in many systems.
I normally design loudspeakers including a foam plug, so that the owner can convert the bass reflex box to a sealed box.
Converting a sealed box to a bass reflex would require drilling holes by the owner:-)
Merry Christmas !
I assume you choose the volume of the box so when sealed the Qtc is a tight one and the F3 is reasonably low. Just closing a port may not work.
I was fortunate. The designer of my woofers took all these factors into account. I ended up with the closed format because of superior control. But I ended up with an F3 of 33 Hz rather than 23 Hz which isn't too important except for deep organ notes and low frequency room affects(if they're on the software) and a few other times.
Thanks, Ole!
I like your idea of being able to convert the box from ported to sealed, that makes the speaker usable out in the room or up against the wall.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Nobody has mentioned the Nestorovic woofer system. It's not as well known as it should be.
If you are unfamiliar, it's a hybrid of the sealed and vented designs using two electrically overdamped/mechanically underdamped woofers, typically one larger thatn the other (i.e.: one 10-inch, one 12-inch). The system operates in a sealed enclosure with both woofers operating essentially in parralel, down to a point where the larger woofer is attenuated (between 50-100Hz) so it begins to act like a passive radiator. It won a patent in th late '70's, I believe it's expired.
Great system. Some of Nestorivic Labs' speakers were very well regarded and even won some A and B Stereophile ratings (don't recall which models got specific ratings). I personally own a pair of Model 3's, very similar to the Speakerlab S30 (a late 70's kit speaker), and you would not believe the depth and control that this 1.7 cubic ft enclosure is capable of.
Paul Johnston "The LoudSpeaker Guy"
Owner and Chief Loudspeaker Biologist
Kent, WA USA
www.theloudspeakerstore.com
My uniform experience over 50 years with sealed box speakers is that they have two unacceptable characteristics: They sound muffled-very little if and only if they are expensive(near and above $5k) and they lose a good bit of the music as they are turned down.At low levels they've lost a lot.
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