Bass amp for a tri-amped system?

I asked this same question recently and didn't get a useful response -- maybe because I didn't provide enough info. What is the low frequency driver's nominal impedance and how about efficiency? I have a pair of subs with a 2.5 ohm nominal impedence that are over 90 dB per watt efficient. I don't need a lot of watts; I need current drive into low ohms. I'm looking at a Magtech or possibly a Coda. Plinius attracted my attention but not sure how it'd fare at sub- 4 ohms. My system is tri-amped, I use different amps and I have no problem with coherency but I have heard this argument. It certainly shouldn't be much of an issue with an active XO @ a low crossover point and a steep slope.

Barrysandy,
Nice to hear from you and thanks for the realistic feedback.. The Signatures have 2, open baffle 15" woofers in each speaker. They are 90dB efficient, but I don't know what their nominal impedance is. So you can see I'm looking for some "iron fisted" control at just those low frequencies. I took the liberty of checking out your system - very nice. I love my Tri-Planar arm too.

For good tight dry punchy low bass you need solid state amps with big low impedance power supplies, preferally DC coupled from input to output, with good current output so forget mosfets and go for bi-polar output devices.
You also need an amp that has good high damping factor (low output impedance) without the need of large amounts of feedback to get it, as too much feedback can make amps unstable.
Krells are good for this and over in Australia big ME (Modular Electronics) poweramps are even better.
Cheers George

Papermill,

If you are interested, you have an opportunity for an experiment here, regardless of the amp you settle on:

Since you are separately amplifying deep bass, you might want to try a Velodyne SMS-1 (+/- $400 from Audioadvisor.com) or SVS/Audyssey DRC box (+/- $800 from SVS) for room correction. This will provide parametric EQ to correct for the room response. IME, this will likely provide vastly more improvement than optimizing the right amplifier (unless you choose a REALLY wrong amplifier).

I believe that both units are sold on a "money back" basis, so there's no meaningful risk to trying the approach. However, I have found that there are huge benefits to be had up above 50/60/70 hz, so you might want to cross an octave higher than 40hz when checking this out.

Good luck

Marty

Marty,
Thanks I'll look into it. Is it anything like the Copeland room correction that was floating around a few years ago? I tried that it and it was very detrimental to the overall sound - plus I needed to add another set of interconnects into the signal path which I think added to the negative results. It provided several equalization curves upon analyzing the room response also. And then one could also, via laptop customize the curve. It tended to ultimately distort the signal. What you are suggesting might be different. Thanks for your input!