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In Reply to: Re: Merlin VSMs and "unaccurate, vented bass" posted by Sean on December 23, 2003 at 23:26:21:
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
Follow Ups:
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
>
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
>
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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