Sonics of Soundlabs

Hello all,

I am contemplating the purchase of a pair of Soundlab M3's, and wonder if some of you guy's (and gals) could help me out a little. They have the newer upgraded transfomers etc. but were manufactured in the late 90's. I am currently using an ARC VT-200 into Martin Logan Prodigy's and love the sound but have always heard great things about the big Soundlabs stats.

For curiousity sake I auditioned a pair of Maggie 3.6's a few weeks ago and they didn't do it for me; there was no bottom end and the dynamics just were not there.......... I thought they did some things well but much preferred the Prodigy's in the end.

I would be buying these speakers used and will not be able to audition fully before purchase. Can anyone tell me how thier sonics compare to my two other "panel" references (the Maggie's and ML's)? Are there any issues (aside from the size) that I should consider when buying a pair of these speakers used? How do the M-3's stack up to the A1's and M1's? Do they match well with the rest of my system..... If I had to find a more powerful amp for instance it would probably be a deal breaker.

Thanks all in advance.

Hi Chris,

I've never owned Soundlabs, but I've been listening to them and A-B'ing them since their inception. I would have bought them too, but never had a space big enough to house them (I think a 20' x 30' room is minimum IMO) so I've been getting along with my ML CLS-IIz's (now with a Depth SW) for 15 years. I agree with your analysis of Maggies. There are some things they do very well (low level is not one of them!) and I even gave a pair of Tympany 1-D's I had stored to a friend for a house-warming gift a couple years ago.

If you have the space for the Soundlabs, go for it. But before you do (and if you liked the Prodigy) definitely don't make a decision until you've auditioned the new ML Summits. I thought they were stunning when I heard them at CES -- and they're not space hogs! They also have their own built-in amp for the low end, so you can do a 150W tube amp for the panel if you want.
Interesting thread. I currently have a pair of Magnepan MG12's (my room is on 10x12) and have always wondering about the sound labs myself.
If I ever move to a Martin Logan it will be the CLS.

I should mention that if you did not hear the 3.6 of some Mye stands, you have not really heard them. They Mye stands ( really tighten up the bass and adds depth, as well as putting the dynamics back in the speaker. In my opinion the Mye stands are a must and not an option. X-over upgrade will also do a lot.

But with that being said, from what I have heard, the soundlabs will still be a step above, but then again so will the price tag.

Let us know what you decide.

Thanks for the responses so far. I just auditioned the new Summit's at my local dealer, and was not at all impressed. Maybe (let's say most assuredly) they were not optimised but, IMO my Prodigy's killed them........... the ML stat panels keep getting smaller and smaller and so does the sound to my ears.

I have Maggie 1.6's in my HT setup and like them a lot but, they are paired with a REL sub. I thought the 3.6's would be just the ticket for two channel but............

Nsgarch, Good point on room size. Does anyone know if these Soundlab A3's will work in my listening room which is about 21x15x11??


If you put SL's in a 15x21 room, you'll have to put them on the long wall to avoid the large sidewall reflections they'll produce (which is why you need a large room!) and so that means you'll be listening to them (relatively) nearfield -- which is a shame with speakers that are truly capable of producing a huge soundstage-and-sweetspot in a large room.

I'm stunned you were unimpressed with the Summits! Something must have been terribly wrong with the demo. I can only assume poor setup and mediocre associated equipment. Do it again somewhere else. Their panels have the same output as the Prodigy with a panel half as big (better dispersion and imaging) and the low end is just about the best I've heard -- in both response and matching to the panel.
Hi Cmo,

Any size Sound Labs will work well in your room. That won't be a problem.

With the VT200 amplifier, I would strongly suggest you have the backplates upgraded with the "high impedance upgrade". This will make them an easier load. The VT200 probably isn't the ideal match for the Sound Labs; depends on how loud you want to crank it.

I have a customer with an early pair of M-3's and he's very happy driving them with a 140 watt OTL tube amp. I have another customer with current generation M-3's (which are higher in efficiency and have better dynamic contrast due to new panel technology) and he finds a 60 watt OTL amplifier to work well.

I have owned Maggie 3.6's as well as all different size Sound Labs, and yes the M-3's will give you more low end extension than the Maggies. In my experience, degree of dynamic contrast is to a large extent amplifier dependent. As mentioned, the latest "high efficiency" panels give better dyanmic contrast than their predecessors. The strengths of the Sound Labs tend to be in other areas, so don't expect to rival Altec A7's or Klipschorns in dyanmics. The Sound Labs excel in naturalness of timbre, low-level detail, and freedom from coloration resulting in absence of listening fatigue even over all-day listening sessions.

The larger model Sound Labs do offer improvements over the M-3 in bass extension, efficiency, and overall richness of the presentation (the latter due to their wider radiation patterns). On the other hand, the narrower M-3 can often give you a bit wider soundstage in a given room because you can place the panels farther apart center-to-center. The M-3 is only about 67 inches tall, so unless you tip them back a bit (with a shim under the front foot) when you stand up you'll probably lose the high frequencies.

The Maggie 3.6 is more efficient than the older generation M-3's you're looking at. But when I had the 3.6's side-by-side with fullrange SoundLabs I kept wanting to turn up the volume on the Maggies to hear the low-level detail that was readily apparent on the Sound Labs. So if you have a low noise floor in your listening room, Sound Labs can give you a great deal of dynamic contrast because you'll be able to hear the low-level sounds that are often lost in a lower resolution system.

Feel free to e-mail me if you have any questions.

Hello Chris,

I believe we had an email exchange or two on amps and Maggies the last few months. As a Magnepan series 3.3/3.5 owner for 5 years and now running an older pair of Sound-Lab A1's, perhaps I can provide some information here as well.

I run my system in a basement room of size 13x18x7.5. This works very well but I'd love another 3-4 feet in each dimension to allow for more space from the side and rear walls....and the speakers to be farther apart. The 2-3 feet greater that you have in each dimension would definitely work well.

To dismiss the Sound-Lab because of a room like mine, and yours as well, would be missing a lot if you want and love the qualities that these speakers provide. I have heard two different SL dealers' comments and also the company itself write of very impressive success with these speakers in rooms much smaller than mine. One dealer has a room just a little bigger than mine and he runs U1's with absolutely spectacular results.

With a lot of experimentation, I have gotten the A1s to sound mighty good. I'm convinced further room treatments, speaker positions, knowledge learned from in-room measurements, etc., will allow me to get the sound even more impressive. I just need to tame the bass a little more as I did not have a lot of material on the back wall with the Maggies. But it does sound very nice now....far far more enjoyable than the Maggies and I was a huge fan of those. For the price, I find the Maggie 3.x speaker to have no competition for the musical magic it provides.

As with the Maggies before, I run the A1's on the short wall. The A1's are close to the side walls, about 4 inches. I found the Maggies were more sensitive to being too close to the side walls so I kept them about 1.5' from the walls.

The speakers on the short wall allows me to sit farther away which I like. Toeing-in the A1s helps a lot to alleviate problems at the sidewalls. I have a woven rug on the side walls just behind the speakers to tame down side-rear reflections due to the toeing-in.

To run the speakers on the long wall would put me right at the back wall which is something I have never liked. I find that being out in the room brings on so much more of an openness in the presentation.

I visited a local audiophile who tends to like his seating position much closer to the stage than I. And I must admit, the sound in his system was outstanding. For someone who likes a closer seat, the long wall might indeed work well. And of course it might also allow for the speakers to be farther apart. But this might require quite a lot of toe-in, which could work out as well. You just need to try and find out for yourself.

With the Maggies, the distance from the rear wall was fine at 3 feet. Due to the A1's greater low-end extension, they need to be farther out in the room to reduce a bass hump; 4 feet is working well but I still need to add more treatments, like the SALLIE devices, behind the speakers to resolve this. Perhaps this will allow me to put the speakers closer to the back wall.

I currently have the A1's 9.5' apart, center to center. This compresses the stage width just a tiny bit. I think a more realistic and open presentation would exist with the speakers at 11' or so apart. With a 15' room width, this could be just what the Dr. ordered. I suspect that much more than 11-12' apart and images would end up being too big to be realistic.

Toe-in with the Maggies had to be very minimal or I found the sweet spot to be small. With the A1's, I can walk from one side to the other, at the back of the room, and the images and tonality is unchanged. And this is with the A1's toed-in toward the listening position which is 8' from the speakers. This is a most impressive improvement with the A1's.

Concerning amplifiers, when I had the Maggie 3.3's and then later the 3.5's, the 110w and 150w ARC tube amps just could not take these speakers to their capability. A Counterpoint NPS400 at 200w output drove the Maggies with no trouble at all and with so much more of a convincing natural presentation than the ARC's. I think there was much more going on with a lack of "reserve" on the ARC amps and not it simply being due to a rated power output issue. I would be skeptical of the VT200 to do much better here with the Maggies.

My A1's are an older pair with the lower efficient wood cores but they do have the updated electronics and toroid transformer. With the older unmodified Wolcott amps at their 250+W output, there was no problem at all to get these speakers to play very loudly with great low-end authority. But my CAT JL-3 amps take the sound to a whole new level and they are rated at "only" 150W. It only goes to show that 150w here was a whole different story than the 150w in the ARC CL150 amps.

I think it is not so much a watt rating but perhaps current driving capability and a reserve to handle the dynamic capabilities of the A1's as well as the Maggies. But I find the Maggies to be more difficult to drive due to their less stellar dynamic capability which makes us want to turn up the level and then of course the driving issue comes more into play. With the A1's, I can play at lower volumes and not only hear far more low-level detail but also have no desire to crank up the volume to get the desired musical effect. So for this reason alone, I feel the Sound-Labs, even the older ones, require a less powerful rated amp to play at loud and dynamically involving levels. So the VT200 could very well be suitable with the Sound-Labs whereas with the Maggies I suspect it would not have worked so well.

Ok, now what about the other improvements with the Sound-Labs? Low end extension! Wow, once you hear this vs. the Maggies, you realize the Maggies are missing so much in the bass. This clearly adds much to the enjoyment of the music. And I found the ML's to be rather anemic in the bass vs. the Maggies. Another big improvement is the A1's ability to have a greater degree of clarity. I loved the Maggie midrange magic and bloom but it tended to mask the detail in the mids and trebles. With the A1's, the Maggie magic is impressively retained but with a whole new level of refinement in resolution.

When I heard the Martin Logan speakers vs. the Maggie 3.5s at the dealer, I just could not get into the ML's at all. They were so resolving but also way too analytical. I remember trying 3 different ML models in the $3k-7k range and upon the return to the 3.5's each time, I felt I was back to listening to music. This was my concern when I was to audition the Sound-Labs but one listen and you realize the musicality here compared to the ML's is not at all the same. I feel the Maggies and the Sound-Labs are much closer than the ML's and the Sound-Labs.

One thing for sure: once you hear the Sound-Labs, you will want to do everything you can to get them to work in your room.....and I feel that if I have been able to do so, you will have even greater success due to your larger room.

To get low end extension and dynamic range Maggies need tons of power (current) and preferrably solid state. You can get beautiful midrange tone and open sound with tubes but you would need more than 200 watts to have it all I would go for the Sound Labs myself...
Thanks all for your very thoughtful responses. The guy has told me he just installed new cores (is this the transformer that changes the impedence curve, making the speaker more efficient?). Are there any issues to look for when purchasing Soundlab speakers used? Are the newer production models different than the older ones in any other way or, is it just the cores that have been changed?

Thanks again........... I'll be going to check these babies out later this week.

The laws of physics are immutable (except for quantum physics which we'll leave aside for now). At sea level, at 68 deg. F., sound travels at 1127 ft/sec.

So the length of a 20 cycle/sec sound wave at sea level at 68 deg. F. in free air is 1127 divided by 20, or ~56 feet (that's for a full sine wave.) To realize the full intensity of this wave in an enclosed room, as produced by the speaker, the room must have at least one dimension equal to or greater than half that length (28 feet). This can be measured from a top corner (at the ceiling) to a diagonally opposite bottom corner (at the floor.)

If that criteria is not met, then the wave cannot develop fully, and although you will still hear the 20 cycle sound, it will require more and more bass boost (as the room gets smaller and smaller) in order to realize a flat room response (assuming the speaker is producing a flat frequencey response)

No amount of "treatment" can increase the physical size of a room. Judiciously placed absorption and traps can only kill unwanted reflections which compromise the soundstage image (particularly sidewall reflections). If you kill all the reflections (as in an anechoic room) then you are listening to the loudspeakers' direct frontal output (100% nearfield) just as if they were a pair of great big headphones.

These principles apply to all loudspeakers, not just Soundlabs. However most loudspeakers can't match both the output and frequency range of products like Soundlabs, Wilsons, etc. etc.

If you're going to buy a pair of speakers that can do what Soundlabs can do, then you owe it to both yourself, and the speakers, to provide them with an environment that allows them to "be all they can be," meaning to fully "breathe" in all directions. The optimum size (i.e. the opposite of an anecohic room) would be one in which the larger dimension was somewhere around that of a full 20 cycle wave, say 30x50 feet. Some people have even suggested that outside would be best, but that is incorrect. Outdoors, the sound just goes off in all directions and never comes back -- the same as in an anechoic room; and in both cases, the effect would be one of listening to giant headphones!
Keep in mind that the room dimension issues above apply to all speakers, not just Sound Labs. I have found that having the capability is more convincing regardless of the size of the room.

Also keep in mind that to drive Sound Labs you must use a tube amplifier for best results. If you use the VT 200, play with the taps on the transformer as you may be surprised by which taps to what to the sound. Generally Sound Labs, like most other ESLs, prefer a low feedback amplifier to get the most out them. This can get tricky as low feedback amplifiers generally will behave very differently depending on their output power and output impedance, but the speakers make it quite evident that taking this care is clearly worthwhile!
Atmasphere -- I believe I did mention that in my post :~)

These principles apply to all loudspeakers, not just Soundlabs. However most loudspeakers can't match both the output and frequency range of products like Soundlabs, Wilsons, etc. etc.
You guys have it backwards concerning room size. Once you get a wavelength that is longer than the room, you get what is termed room gain, on the order of 12db/per octave. (In an actual room it is less due to the walls flexing and losses through the walls, but the gain is there). Smaller rooms = more bass.
Mcreyn -- you are incorrect. When a half wavelength (~ 28 ft for a 20 cycle/sec tone) is longer than the longest dimension of the room, it cannot fully form in space before hitting a wall and reflecting. causing it to double back on itself, producing points of both cancellation and reinforcement. If you happen to be at one of the reinforcing points, it may appear that the bass is very loud, but just a few feet away there may be a null point with very little bass due to cancellation. Right at a wall surface, there is always louder bass because that's where the wave changes direction, therefore releasing a lot of energy when it momentarily stops before being reflected in the opposite direction. That phenomena happens in all rooms though, regardless of size.

If your analysis was correct, then shorter organ pipes would produce lower notes :~)

You are speaking about standing waves, which is different than room gain. Room gain results from the maximum length of the wavelength being longer than the room. You do not have standing waves at frequencies below this fundamental frequency, only above. The way to compute the lowest resonant frequency of the room it to take 1127 (or if metric 343) divided by (longest room dimension x2). The result is the lowest freqency that you can have a standing wave and the knee freqeuncy below which you experience room gain.

You analogy of an organ pipe is incorrect as an organ depends on resonance to produce sound. This is far different than sitting in an enclosed area (a room) with a device that puts out an accoustic signal.

Here is a quote from Tom Noussaine on the subject:

"2. Room gain: Room gain starts at roughly the frequency of your lowest axial mode. The pressure gain is 12 dB per octave as frequency falls. In a car its at 60-70 hz depending on size. In my 2136 cubic foot older listening room it started at just below 30 Hz. In my 7500 cubic foot current room it starts at 16 Hz. A Velodyne FSR-15 had 8 dB less output at 2 meters in the larger room with idntical placement."
Mcreyn -- standing waves are only produced when a room dimension is a whole multiple (not a fraction) of the half wavelength of the frequency in question. The room will gain in dB (more SPL than the speaker is putting out) by resonating at the frequency in question (like an organ pipe) and that is why bigger rooms have lower resonant frequencies (per Mr. Noussaine's remarks)

Once again, a room smaller than a certain frequency's half wavelength cannot resonate at that frequency and thus the SPL cannot increase over what the speaker is putting out by itself.

I also read Mr. Noussain's remarks on avht. The smallest room he mentions (assuming an 8 foot ceiling) is quite big enough to develop a full 20 cycle wave (roughly 13x20), and so standing waves (and room gain) are definitely possible at that frequency -- however, in a room too small for the 20 cycle wave to form in the air, standing waves, and therefore room gain are not possible.

As for his weird experience with the Velodyne: A loudspeaker will always put out the same SPL (at a given frequency, at a given power input, at a given distance away from it) in any environment (or even outdoors) at normal atmospheric pressure UNLESS there is either cancellation or reinforcement at the point where the measurement is being taken (which is probably what happened to Mr. Noussaine, and he just didn't realize it.)

I had trouble visualizing how he placed a speaker "identically" in two rooms of different size -- so I'm not sure what the heck he meant; maybe he meant "proportionately" since "identically" would be geometrically impossible. It sounds like he once again stumbled onto a null point without realizing it.

In any case, I would not be especially drawn to his remarks in the future.

Well guy's,

I went to hear these speakers today and was dissapointed. Only one was working.......... the upgraded backplate had not arrived from Soundlabs for the other yet, and there was a lot of distortion from the one that was working. I think it was the gentleman's amp that was clipping, but I am not positive. He was using a monster SS Crown PA amp. The sound was pretty harsh all the way around.

Anyway, to make a long story short we agreed to do another audition when both speakers are up and running (hopefully next week). Any thoughts anyone on this experience? I am hoping this isn't typical for these speakers. Question: Are Soundlabs unreliable? I am starting to not feel real good about this pair of speakers.

I will try this one last time and then quit wasting my time, as it appears you are more concerned with running your mouth than hearing the truth. Below the resonate frequency of the room, there is what is termed transfer function gain, room gain, or cabin gain. All are the same thing. Below the knee frequency, there are no standing waves, only the 12db/octave rise.

Try this little experement. Take your subwoofer, run a 20hz signal through it. Measure the output at 10 different locations in your listening room with an SPL meter. Don't change any levels and take that subwoofer and put it in a closet with a door. Close the door and stand in there with the sub. Measure the SPL reading there in 10 different locations. Guess what the SPL reading is higher and very close all around. Can't find any standing waves, because there are none.

Now, I know you think you are smarter than Tom Nussane, so here are a few more links that discuss the transfer function, but I will guess that you will continue to argue until you are blue in the face that you are right and scientific fact is wrong.
A good place to ask questions about SL speakers as well as carry on dialog is the Soundlab owners group and they have a forum:

Soundlab speakers are large, a bit delicate, and sensitive to handling (shipping) and set-up issues, such as bias adjustment. You might say they can be a little idiosynchric. But, to answer your question directly about SL reliability, in my opinion their reliability is fine when set up properly with care (bias set properly) and, they have the latest updates including the high efficiency cores. There have been isolated reports from time to time in the past on tears or rips in the membrane for one reason or another but, the company always worked to resolve these issues promptly. I don't think you will find many, if any, reported quality issues on the newest iteration coming out of the factory.

Again, be sure to post your question on the SLOG forum and you should get some responses.

And as a side note, "Mcreyn" is correct about standing waves, room gain and such.
i owned a used pair of U2s. while i personally didn't care for the sonic presentation (very subjective), the membranes did tear and required factory repair, and the backplates were not built w/ the quality one expects of $15k speakers. ---no comparison to the WP6s i now own insofar as quality of craftsmanship (i also like the WPs sound better, but to each his own). ---also, i find any speaker as inefficient as soundlabs to be very limiting insofar as equipment choices go...too limiting.

that said, the factory service was very good and i've no complaints of the folks in utah. having lived w/ planars, i don't like them.

soundlabs (moreso, any powered speaker) are not set & forget. if you want maintenance free, get cones.

Boy what an awful piece of equipment to hear a Sound Lab with.I would never want to hear a Soun Lab witha Crown S.S.
Its been a long time ago since I listened to an A-1.This was at a Stereophile Show.The speakers were hooked up to
Audio Note Tube Mono Amps and Preamp.The sound quality and transparency was astonding.The speakers need a very high quality tube based system to audition them properly.Personally I own th Martin Logan Quest Z's,and would never want to depart from them.I noticed with the newer Martin Logan speakers the els panels are getting narrower,and the crossover freq. seems to be getting higher.
I think you and I should keep the speakers we have.Why would u want to sell the Prodigy? Is it lack of deep bass?
the Sound Labs have to much of a radiating surface area to contend with.I think speaker placememt may be more difficult.
Personnally I would keep the speakers u have and work on your source or front end of your system.If u have any issues with your system you can email me.I may be able to help u further in other recommendations I may have.Happy Listening
Chris, the longest diagonal of your room is 28 feet (thanks to the 11 foot ceiling height!) and so flat response down to 20 cycles is possible. I think some of the other posts (regarding the phenomenon of "room gain" in smaller rooms) failed to take into account that the speaker you are considering has what Prof. Linkwitz calls a "dipole woofer" which, as he makes very clear on his website, requires the necessary 1/2 wavelength dimension (or more) to produce a given frequency:

Room modes cannot exist when 1/2 of a sound wavelength exceeds the longest room dimension. If this is 7.5 m (24.6 ft), then a wavelength will be 15 m and the lowest mode frequency is 343 m/s / 15 m = 23 Hz. Below this frequency bass response may increase due to room gain, if the woofer is a monopole. For a dipole woofer the response may stay flat or drop off, depending on the rigidity of room surfaces and lack of any openings.

If your listening room were just a little bit smaller, you would definitely be better off with a hybrid speaker (like the Summit) which have monopole woofers which allow the development of "room gain" thus maintaining SPL at lower frequencies in small spaces. Just remember that "room gain" (or "transfer gain as it is sometimes called) is only an important factor when the room is too small to allow formation of the 1/2 wavelength of a given frequency (an automobile interior is probably the extreme case.) At that point, you are no longer in a "listening room" but instead you are in a "secondary speaker enclosure." And if you push that example even further, in other words, reduce the size of the listening room down to zero, you are wearing headphones!
Thanks for all of your posts so far........ 76doublebass, I am only thinking of trying something new (always on the lookout for the holygrail so to speak). It is probably too early to really judge the Soundlabs but, I am thinking you are right; my Prodigy's sound pretty darn good (if not great!) to my ears. After trying Maggies, Dynaudio, etc. etc. the ony speakers that I have heard that I like better are the WP7's and they're out of reach money wise. Again it does all come down to personal preferences......... Still I'm pretty curious about these SL monsters after all of the good things I've heard.
If it's not too late...Suggest you listen to Eminent Technology LFT-8A's. If you like the way one pair sounds, you could do as I did - run them "stacked" or twin pairs, all biamped. Phenomenal soundstage, detail, slam, you name it...
Boy you really don't get it!!!!! There are no standing waves below the lowest nodal frequency. Period, it doesn't matter what type of tranducer you are using. Also, you don't measure the diagonal of the room, you measure the longest distance between two walls. Nodes and suckout are caused by reflections of parallel walls, one reason you will see that studios use stacked or even angled walls is to spread out these modal frequencies.

Read and re-read the quote you posted (as apparently you know believe in room gain since Linquist addresses the subject). It clearly states "Room modes cannot exist when 1/2 of a sound wavelength exceeds the longest room dimension." No ifs ands or buts. Below this frequency you may or may not have gain depending on the type of radiator used, but you will not have room related roll off or standing waves.

You are correct on one point (so apparently you did read the article, even if you choose to only accept parts of it). Below the lowest modal frequency a dipolar may or may not cause room gain. This is because room gain is triggered by pressurazation, which a dipolar does not normally cause.
Hi Cmo,

Something definitely was not right with that single speaker setup you heard. Hard to say from here, but it could have been a problem elsewhere in the signal path, or it could have been improperly set bias. I remember once for some reason I had the bias set way, way too low, and on loud passages there was a horrible "crunch" that terrified me until I figured it out. Maybe what you heard was amplifier clipping as you suspected - note that a second speaker + amp would add 6 dB more headroom, so if he was trying to replicate two-speaker SPL's with a single speaker then he'd be asking the amp to deliver four times as much power output as normal.
Time for my 2 cents again:

Never attempt to audition a Sound Lab with transistor amps! You will come away with the mistaken impression that the speaker is harsh and has no bass. This is not the fault of the amplifier so much as it is bad physics to put a transistor amp on ESLs. Here is why:

Most transistor amps (like a Crown or Krell for example) will double power when going from an 8 ohm load down to four, and double again from 4 to 2 ohms. Conversely, the power is cut in half going the other way.

Now the maximum impedance of most of the newer Sound Labs is about 16 ohms in the bass region. Guess what? You have no power to make bass and about *8* times more power to make the highs. Yes, the feedback in the amp helps reduce some of this (adding to loudness cues along the way due to the nature of negative feedback), but: in a nutshell, harsh sound. ESLs in general require the amplifier to maintain constant power regardless of load, not constant voltage which is how most transistor amplifiers work.

Tube amplifiers, especially those with little or no feedback, provide this constant power characteristic. Insist on it if you want to hear the speaker perform properly. Otherwise it is a good idea to refrain from making an opinion of the speaker!

Audiokinesis brings up a very important issue, i.e., the bias pots on the backplates. I got careless several weeks ago and tweaked one of these pots too much and messed up the level balance between the two speakers.

A suggested approach would be to turn up the bias pot on each speaker, one speaker at a time, until the "spitting" noise occurs and then ease back the adjustment just until the noise is gone. Then with a test LP or CD with test tones, and a SPL meter, match the levels of the speakers by reducing the bias pot of the speaker that has the higher level. This removes the problem as described by Audiokinesis and brings on as much speaker efficiency as possible.

Also, rather than still wonder if your ARC amp will work or not, take it with you once the speakers are working correctly. And taking your own speaker cables might be of value too.

Chris, I hesitate to say this for fear of offending someone, but I'll say it anyway: the Crown Macro Reference is, in my opinion, a harsh sounding amplifier. And listening to only one speaker, quite possibly with the bias set too low, is hardly a meaningful way to judge the sound. Doubling the number of speakers (acoustic sources) played at the same SPL as one (and obviously using twice the power since two amps are working at the same level as one was) results in a 3 dB increase in SPL, not a large increase but audible. On the other hand having a stereo image will greatly benefit the presentation.

John's (Jafox) suggested approach is good. While your VT-200 may not be the last word in amplification it should be a nice improvement over the big Crown amp, so take it along for the followup listening session when the system is up and running fully.

Recently I posted the following response to a thread elsewhere related to matching amplifiers, which I hope is of help:
The sensitivity of Sound Lab speakers, up till last year, was published as being equivalent to 88 dB at 1 meter at 1 watt input, measured at 4 meters, but in terms of real world performance they're more in the range of low 80s at best, meaning they tend to work better with healthy amplification to spring to life. Those built since early last year are on the order of 3 dB more sensitive, which certainly helps, and they're livelier, more responsive, and cleaner sounding.

Because Sound Labs are mostly a capacitive load, the impedance is relatively high in the low bass, falling with increasing frequency to a dip to about 5 to 6 ohms in the 500 to 550 Hz region, above which the separate midrange/treble transformer sees the signal and raises the impedance some and then the impedance drops off gradually with increasing frequencies. The impedance at 20 kHz is 2 ohms or less depending upon the setting of the brilliance control, which poses a difficult load to an amplifier but thankfully there isn't a lot of energy up there. The panel is driven full range, fed by the two separate step up transformers in the backplate to smooth the impedance curve, although it's still a tough load.

I don't have any recommended current capability for amplifiers to use, but solid state amps reported to work well include Parasound Halo JC-1s as well as some larger models by Krell, Levinson, Pass, Boulder, Bryston, and Rowland, and I have some experience with some of them. I understand the Innersound ESL amps can drive Sound Labs to high levels and can be very price competitive, though they might not be as clean and grain-free in the treble as some of the others. For solid state, I recommend a good beefy amp of at least say 200 watts per channel, and more is better. Perhaps it won't always be the case. With tube amps there seems to be more variation in the amount of power needed. I've had a 100 watt per channel beast in my system that left little to the imagination, while 250 watt monoblocks from another manufacturer didn't fare so well. With Sound Labs, a hefty amplifier power supply is very important whether the amp is solid state or tube, as are output transformers if they're present - an amp that skimps on output tranformers probably won't drive the speakers as well as a less powerful one that gets 'em right.

If you have other questions or comments, please feel free to contact me offline.
I should add a disclaimer that I'm an authorized Sound Lab dealer.

Brian Walsh

You might want to take a look at diamonds system, and possibly contact him:

He thinks his new Summits are awsome.
My research indicates that the speed of sound is about 1116 feet per second, but perhaps that assumes a different temperature or humidity or other variable than the 1127 feet per second cited by Nsgarch; but let's say either is in the ball park.

I'm not sure it it's necessary to push for a system that can reach all the way down to 20 Hz; personally, I'd be happy to get a clean 32 Hz. At 1116 feet per second, a 32 Hz wave will be just under 35 feet long. I've been under the impression that you'd like to have 35' between the speakers and the back wall (behind the listener) to avoid a wall reflection before the wave completes one cycle. Nsgarch suggest that maybe you only need to have enough room for the wave to complete half it's form, ie, 17.5 feet will get you 180 degrees of a sine wave for 32 Hz (assuming a 1116 feet per second speed of sound). I don't know if Nsgarch is right, but I'm rooting for him to be correct as that makes the challenge of finding a decent room only half as difficult as I had presumed. Further, if I understood Nsgarch, he says that that dimension will suffice even if it's from a wall/floor line to the diagonally opposite wall/ceiling line. My geometry isn't working, but someone should be able to compute how long the room needs to be for a given ceiling height to support such a 17.5' diagonal. That would in turn tell us the minimum length needed to support 32 Hz. Then from that length, we could use the Cardas formula to see what width would compliment the length (and height). Then we'd have a pretty good room identified, but to make it optimum we'd need to pie out the walls and the ceiling so those wouldn't be parallel surfaces. Then we'd just have some room treatments left to go to get the absorbtions and relflections dialed-in.

Again, I don't know if Nsgarch is right about the need for only half the length of the lowest desired frequency, but either way, I am highly confident that there is a minimum room length needed to get solid/accurate bass. And if the bass isn't right, it's going to be a struggle to get the midrange and highs right.

My main point is that you can buy all the world-class gear you want, but without a decent room, you aren't going to realize the potential of the gear. And the more capable the gear is the more the room is going to become the limiting factor. I'm pretty sure that spending 100k on a system wouldn't make as much sense as spending 50k on a system and 50k on a room (unless you already had a deluxe room). I've found that somewhere around $2500 to $10k for a system, the room can easily become the limiting factor. In fact, all the critiquing we share with each other on Agon about how speakers, amps, preamps, etc. have this or that tonal characteristic is often just a report on what our equipment plus our room sounded like. If people think ICs can act like mini "tone controls" (and no doubt they do), I think we would be surprised to hear how our rooms are mega tone controls if we could swap rooms as easily as we swap ICs.

I'm not against pursuing great equipment and great systems, I'm just advocating a recognition that the room is a huge variable that introduces a huge number subtle variables that add up to an almost random and often unpredictable result. Being aware of the causes and effects of room acoustics could save you a lot of time, money, and effort.
Martin Logan hasn't made a worthwhile speakers since they stopped making the Monolith III. As an old ML owner, there is nothing desirable or competitive about the new line.

If you must go hybrid/ESL then investigate the Innersound Eros III in its active version a very worthy rival to the Sound Labs with a much more Dynamic (punchy) Presentation like your Prodigy's vs. Maggies. The Innersounds compete with Dynamic speakers in their output and maintain the ESL sound and coherency. They are IMO are on a much higher performance level from your Prodigy's despite costing less.

I bring them up based on your input (what you've written) in the discussion, this seems like a it might be a good speaker for you. Too many ifs (from what others have said) in your system to go buy used Sound Labs it seems.
I will agree that the Innersound Eros III's are outstanding speakers. The integration of the woofer and panels is remarkable. And, their transparency and speed are as good as any speaker that I have ever heard. However, I just could not live with it's beaming characteristic and associated small sweet spot. It's too bad the designer didn't go ahead and curve the panels similar to the SL approach. Maybe in their next iteration....
Let me backup that Neal Has pointed out the one drawback, I should have mentioned. Its a focused setup, not a great deal of lateral movement allowed by the system and its a bit picky to get perfect.

Thanks Neal. I forgot.