SOUNDLAB ULTIMATE 545

@pinotnoir What time of day are you calling? They are on mountain time.

While technically true, high powered Solid state amps Like the JC1 do just fine to 105 dB (as high as I have gone) for several reasons. The JC1s due to a programming error I made absolutely fried the high frequency brilliance control and I mean barbequed BLACK and I had no idea this was happening until I smelled smoke. The JC1s merrily baked along without so much as a whimper. Tough amps.
Next, while the Soundlabs are capable of making plenty of bass the long excursions required below 100 Hz doppler distort everything else the speaker does. I am of the firm belief, know it for an absolute fact, that full range ESLs sound even better, much better, if you use them with subwoofers.

There is a reason Sound Lab made the B1 subwoofer, which was the size of the A1s they made at the time (back in the 1990s). But the use of subs isn't something limited to Sound Labs- many speakers benefit from not having lots of excursion.


You have confirmed my comment- in order to work with Sound Labs your solid state amplifier needs to be high power. Since the impedance of almost any ESL varies by about 9;1 to 10:1 from the bass to 20KHz, quite often the solid state amp is making far too much power at 20KHz (A high power amp can probably double power as impedance is halved, but ESLs don't work that way, they need the same power regardless of impedance at a particular frequency in order to make the same sound pressure). Since you have to throttle it back somehow, the Brilliance control becomes a target as it has to dissipate some energy.


The trick of course is finding a solid state amp of that sort of power that simultaneously actually sounds like music (instead of like electronics); traditional class AB designs can be challenged in this area due to a lack of feedback at higher frequencies- which causes them to be bright and harsh (due to distortion) as I mentioned in my prior post. Its this particular problem which is why when distortion measurements are published, they are only measured at 100Hz. 1KHz and 10KHz distortion specs are usually not measured or published, but if they were you'd see that the distortion rises with frequency. 


This lack is caused by inadequate Gain Bandwidth Product, which is engineering gobbledygook for "the amp runs out of feedback at higher frequencies". You can't just add more feedback- that takes more gain, part of that Gain Bandwidth product thing, and at some point all the frequency poles in the amp cause so much phase shift that at a certain frequency the feedback is positive rather than negative so the amp can oscillate. The engineering expression for this is 'the phase margin of the amp has been exceeded'. This is part of why the Brilliance control is so important on the Sound Lab when using solid state amps- you have to tone down both the excess energy and the brightness caused by distortion.

Duke is correct about Atma-Sphere but as a rule they work much better with solid state amps. The problem for most tube amps is the extremely low impedance at high frequencies. This requires a LOT of current. Big solid state amps with over built output stages work best, particularly class A. The only exception I know of is the Atma-Sphere amps The two amps they have shown with are the Atmasphere either MA1 or MA 2, atmasphere would know, Ralph you out there?

The impedance thing is a real challenge for solid state amps! You don’t need a lot of current when the speaker is at its lowest impedance since that is at 20KHz.

But in the bass the impedance is 30 ohms. This means that a solid state amp rated at 600 watts will make around 160 watts. This is why a tube amp can keep up on this speaker with a solid state amp rated at 4x the power. And this is the reason that if you go solid state you need such a high power one- not because of the highs but because the solid state amp will have troubles making power in the bass. Our MA-2 makes 220 watts on that speaker; to keep up a solid state amp would need to make nearly 900 watts!

The older Sound Labs had a dip in the impedance curve because of a simulation error when the crossover was designed about 25 years ago. About 6-7 years ago a number of our customers sent some actual measured data to Dr. West that convinced him a crossover redesign was needed- thus the Toroidal 2 backplate. This in turn caused the speaker to be much easier to drive and so you could do with our MA-1 what took our MA-2 on the older speakers.


One thing about almost all ESLs: because they are not drivers in a box, and thus the impedance peak in the bass is not the result of a driver at resonance, they don’t follow the same rules that most box speakers do. Most box speakers are designed around the idea that the speaker is ’voltage driven’ which is to say that the amplifier driving them is a ’voltage source’ in that it can provide the same voltage regardless of the impedance of the load. Put another way, such an amplifier can double power as impedance is halved. ESLs OTOH need the amp to be able to put out the same *power* regardless of the load rather than the same voltage. For this you need an amplifier that has a bit higher output impedance but also can make some serious power. For more on this topic see
http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html
The Sound Lab is a bit of an exception here- unlike most ESLs its equipped with controls that allow you to adapt the speaker to a variety of amplifiers. Usually with solid state amps you want to set the bass controls for +3 or +6dB (keeping in mind that the wall behind the speaker will be at least 5 feet away) with the Brilliance turned down a bit. With our amps at the other extreme the bass setting is usually at -3dB while the Brilliance is set all the way up.


When you see controls like this on the back of any speaker, that’s a sign that the speaker is performing according to Power Paradigm (see link above) rules.

Finally as anyone with exposure to ESLs knows, Sound Labs are some of the fastest and most revealing speakers ever made price no object. For this reason its really important that the amplifier and preamp have similar transparency- you need your ducks in a row with this speaker; its transparency reveals amplifier flaws with ease. I would hesitate to use a solid state amp on this speaker for the simple reason that the distortion of solid state (which causes solid state amps to sound bright and harsh) will be compounded by the low impedance of the speaker at high frequencies, causing the amp to also be tonally bright.