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Soundlab Speakers - Budget Amp Suggestions

I have tried to read as much as possible about different types of amplifiers capable of driving electrostatic speakers. Thanks to everyone for the great articles and discussions. In particular, I am looking for a ss amplifier that can drive Soundlab speakers. The Soundlabs have a low impedance at high frequencies and a high impedance at low frequencies. A high power ss amp that can drive difficult loads appears to be the ticket (I'm not interested in tube amps). High current is needed for the high frequency/low impedance (but not necessarily high power) while the high voltage (albeit at lower power) can drive the high impedance at low frequencies.

While looking for speakers I came across the Soundlab speakers and really liked the sound. I basically blew my budget on them, which for me is not a bad compromise because I don't want the speakers to be the weak link in the chain.

So this is what I have:
1. Two Soundlab A-1 speakers (1992 vintage)
2. One Soundlab B-1S subwoofer (pre 1990) - This is a stereo subwoofer having two separate inputs to drive each interior panel.
3. The A-1s have the toroidal and impedance upgrade.
4. I had all the speakers reskinned with the px mylar.

There will be some type of crossover between the A-1s and the B-1S (the frequency and type of crossover is undetermined at the moment)

I believe that having the B-1S reduces some of the constraint of having the highest power amplifier to drive the A-1s (e.g. 500-600W) since a lot of the bass will be coming from the B-1S. I was told to limit the power to the B-1S to a 400W or less ss amplifier. I am thinking that perhaps I could get away with a lower power amplifier for the A-1s because of this scheme. Please let me know if I am wrong.

As I said my budget is limited. I have about 1.2K and perhaps up to 2K to spend on an amp. The amp I have targeted is a Sunfire Cinema Grand Series II 5-Channel amplifier that outputs 425W a channel. The channels driving the B-1S won't be delivering a lot of power as the impedance is 16 to over 30 ohms. The amp should be able to drive the A-1s adequately. As a side note I have a couple of amps (Crown K1 or Citation 7.1 which output between 300-400W) that I could use to drive the B-1S if needed.

Are there some vintage or other budget amps that I should be considering. Is my analysis wrong? Any suggestions on crossover frequency? I appreciate any and all input. I want to thank every one in advance for their thoughts.

Regards,
GWHO

gwho

Showing 12 responses by atmasphere

atmasphere's avatar
atmasphere
12,099 posts
 
Grannyring, just FWIW the Atma-Sphere MA-1 would have been underpowered on many of the older Sound Labs.

BTW, Roger West has a new back panel that should be available as an update to any A-1 or similar Sound Lab. It seems to be based on a lot of the conversation that has been going on on some of the forums regarding the drivability, impedance and mods that can be done to the older back panels. The result *should* be a speaker that is a lot easier to drive!

People that have done some of the mods have thus been able to get the MA-1 to work fine. But others have reported that they got a lot better drivability when using transistor amps like the Parasound JC-1 as well.

You might want to read this thread and the one above it on audioasylum, there is a lot of info on the mods done to the back panel:
http://www.audioasylum.com/forums/otl/messages/3/35023.html

For someone trying to drive used Sound Labs on a budget I would expect this to be required reading.
atmasphere's avatar
atmasphere
12,099 posts
 
Gwho, I realize that the budget is an issue but one thing you will have to face it its really hard to get Sound Labs to sing if you have transistors. Transistors as you know try to double power as the impedance of the load is halved, which is another way of saying that they cut power in half if the impedance is doubled.

With the Sound Labs both ways of looking at this are a concern. On the bottom end you can't make power, on the top end there is a tendency to make too much. To give you an idea, a 150 watt tube amp can easily keep up with a 600 watt transistor amp on this speaker due to this issue. A 600 watt transistor amp will only make about 150 watts on a Sound Lab due to the impedance. A tube amp will not loose so much power on this account.

It might help to understand something about how ESLs operate, which is to say that they work much better with an amplifier that behaves as a power source rather than a voltage source.

Don't worry if you did not understand that last sentence. Just read this article, its a quick read and there is almost no math :)

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

So if you plan to bi-amplify, you might be able to do just fine with a tube amp that makes only about 60 watts for the top end. This depends somewhat on your room. The reason people use high power transistors is because of the impedance in the bass, while a 200 watt tube amp is usually enough power in many listening situations.

Now if you apply the mods that I mentioned earlier, which are easy to do, the speaker gets a lot easier to drive. Customers have reported that our MA-1 had unlimited power (could not clip them) in their system after they did the mod. IOW the driver is fairly efficient, most of the problem of drivability has to do with the back panel. So if you do this and you bi-amplify, a 60 watt tube amp might do the trick, and will sound better than a transistor amp on that load.

Something to think about!
atmasphere's avatar
atmasphere
12,099 posts
 
Grannyring, what mod did you perform? Did you remove the big resistor?
atmasphere's avatar
atmasphere
12,099 posts
 
Grannyring, from what I understand that shunt resistor is a problem for any amplifier, even transistors. There is a reason it is rated for so many watts- amplifier power is used to heat it up. It does not matter what kind of amp you have.

If you remove it you will find that you need less power to play the speaker and it will sound better too. It is this mod that allows the MA-1 to play that speaker with volume. Take a look at this link- its the one with the photo: http://www.atma-sphere.com/AboutUs#Feedback

After the resistor is removed, the cap value can be reduced. This prevents the HF transformer from saturating.
You can PM more more info if you like.
atmasphere's avatar
atmasphere
12,099 posts
 
Stay away from room EQ! If you want to complicate things (which you say you don't want to do) EQ is a good place to start. The problem you are up against is that you are dealing with a very transparent speaker, and the effects of DSP are easily audible on it. Yes, you may get the frequency response in the room to be flatter, but you will pay a big price sonically to get there. IMO/IME its not worth it unless you have cheap speakers.

The other thing you want to consider is that digital volume controls rob the signal of resolution at lower volumes. Again, consider the fact that the Sound Lab is one of the most revealing speakers made. You really do have to have your ducks in a row when you set them up, if you also want them to sound like music. So something with a good analog volume control is advised, perhaps even an active line stage to deal with that reality.
atmasphere's avatar
atmasphere
12,099 posts
 
Gwho, when you read that stuff about active eq/room correction, it really does not apply to a high resolution system or the people saying really aren't listening that closely.

If you want a crossover, talk to Tom Tutay 850-244-3041 he makes the best out there and the only ones I would consider for your application. Dunno what they cost though...
atmasphere's avatar
atmasphere
12,099 posts
 
Is your amp single-ended input or balanced?
atmasphere's avatar
atmasphere
12,099 posts
 
If your amplifier supports balanced inputs then I would feed it with a balanced source.

The reason there are balanced cables and a balanced system is that it offers you the ability to have the cables drop out of the overall system sound. I am sure by now you have noticed that you can hear differences in interconnect cables; the balanced line system was devised to eliminate that problem and it does it very well if you adhere to the balanced line standards.

I of course like tubes more than transistors; if you are looking at a preamp I would recommend a balanced tube preamp. If you are looking at DACs (and no preamp), you will want to find one with a balanced output and an analog volume control (digital controls reduce resolution as you turn them down). I think Ayre makes such a unit.
atmasphere's avatar
atmasphere
12,099 posts
 
It depends on a lot of factors. If the DAC has trouble driving cables you might be better off with a good line section, especially if the amps are far apart. Also, some DACs don't have volume controls... and you might want more than just that one input.

The Sound Labs can be pretty convincing. You might like them. If that is the case you may find yourself looking at ways to get more out of them. One way to do that is play LPs. You may not believe it now but you may someday find yourself playing vinyl. If that happens you certainly will want a proper preamp.
atmasphere's avatar
atmasphere
12,099 posts
 
If you are on a budget and have A1s and B1s, had it ever occurred to you to sell the B1s and use that to finance an amplifier that can drive the A1s properly? That would seem to be a lot more expedient than trying to find two competent amplifiers to drive both the top and the bottom!

BTW you will need similar power from both amplifiers...

100-200Hz is good for the crossover point. A1s by themselves go down to 22Hz. The subwoofer is ostensibly not used to deepen the bass so much as it is to get excursion off of the A1 panel so it can be more transparent. But you can do the same thing by using the right electronics on just the A1.

How big is your room??
atmasphere's avatar
atmasphere
12,099 posts
 
Right, and you will find that you have a similar problem with the A1. So to drive them you will need two pair of identical amps, otherwise the weaker amp will describe the maximum volume level.

If I were you I would get rid of the B1s and concentrate on just the A1s and the amps for it. Then you would have less equipment so you could still hide most of it except the front end (preamp/dac/CDP/whatever).
atmasphere's avatar
atmasphere
12,099 posts
 
I think you will find that the simpler you can make your system, the better chance you have of getting it to sound right.

Good Luck!
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