Good amplifier topology for difficult speakers?

[JeanMiK]

Hi

I own 1 pair of 3 way coffin-like floorstanding speakers (2.0 system), for home use at reasonable spl level, each coffin having 1 pair of 7 inch woofers, and an impedance curve with a peak around 21 ohm, and a dip around 2.5 ohm.
Sensitivity around 90dB
I tried different power amplifier over time, and now more or less happy with a diy (myself) dual mono power amplifier.
My best amplifier these days: 2 x 600W psu and class AB mosfet drivers (Peeceebee V4H modules).
I'm still having a hard time to understand what makes the sonic result difference between various amplifiers: brute power and big headroom, big slew rate, mosfet brand, circuit design, all of this?
Which is the main factor ?
I also tried class D amplifiers, for poor result.
I never found a clear answer on this issue, beside try this or try that, without real technical objective hint.
Thanks for your lights!
JM

 

[Koeitje]

NCore NC1200, rated at 1200/700/400W@2/4/8 Ohm. Should be no problem. Just get something with a real 2 Ohm rating. A lower powered NCore amplifier will still do the trick I'm guessing.

 

[H-713]

A few amps that I like for this, in order of preference:
-BSS EPC780 (but you'll have to find one that works).
-Any of the Class AB MC2 amplifiers. MC650s and MC750s were great (1250s were even better), a modern equivalent would be an S1400. Very close second to the EPC780 in performance, but much more reliable.
-Older Crest amplifiers (3301, 4801, 6001, 7001, CA4, CA6, CA9).
-QSC Powerlight amplifiers.

All of these amps are beastly and can handle low-impedance load without issues.

 

[H-713]

I find that a lot of Class D amplifiers do not behave as well with difficult reactive loads since the output network can be affected by wildly varying low-impedance loads. Some class D amps handle this a lot better than others.


I suspect that you're dealing with a combination of a lot of factors.

 

[murraycamp]

There are amps in different classes of topologies that can handle (well) difficult loads. I think it's more about how well it's engineered and manufactured (qc) than which topologies a particular unit utilizes. IMHO, YMMV, etc.

 

[JeanMiK]

Thanks for your answers.
I guess what we would need is some kind of standard test method for that type of difficult load ?
JM

 

[Synergy4]

Thanks for your answers.
I guess what we would need is some kind of standard test method for that type of difficult load ?
JM

Well a stable amplifier with a reasonable damping factor and a low output impedance from 20Hz to 20kHz may be the place to start looking for driving a difficult uneven speaker load impedance.

There may be a number of amplifier options, but it is the actual implementation of the amplifier topology that matters more the most.

For Class D, maybe look at the the 1ET400AEIGENTAKT : https://purifi-audio.com/eigentakt/
....Output Impedance <65μΩ @ 1kHz, rising to around 650μΩ at 20kHz...

For Class AB, maybe look at the Benchmark AHB2 : https://benchmarkmedia.com/products/benchmark-ahb2-power-amplifier
Damping Factor:
350 at 20 Hz, 8-Ohms
254 at 1 kHz, 8-Ohms
34 at 20 kHz, 8-Ohms

Benchmark's thoughts on damping factor: https://benchmarkmedia.com/blogs/application_notes/audio-myth-damping-factor-isnt-much-of-a-factor