Subwoofer Amps!

The amp topology used in subwoofers...does it matter?

Thanks for bringing up this subject.

Not saying amp topology doesn’t matter with subs, but from my chair it’s more a matter of actually using a quality amp through and through than topology per se, with the really important aspect here being using that same amp/its topology top to bottom - that is, over the main speakers as well. That requires of the amp to be up to snuff top to bottom and is where the overall quality parameter comes in, in addition to having plenty of power.

I’ve had my sub cabs built after a year long research period for a horn-based design, and thus use external amps of my own choosing rather than having to settle with the built-in plate amps of preassembled subs. To begin with I used a variety of quality pro amps from Crown and Lab.gruppen (K2 and FP6400 respectively) for sub duties, both class H/D variations, and while they were great amps for their intended application and for use with subs I found they could be better for full-range use, even though the Lab.gruppen amp surprised me here.

Then I started experiencing with MC² Audio studio amps (class A/B, T-series) for my main speakers, one for each driver section actively, and by chance used one of them on the subs instead of the Lab.gruppen amp. That’s when it became interesting (apart from finding out they sounded great over the main speakers). Soon a third MC² Audio amp entered the collection for a full frequency range coverage of my speaker system with the british amp manufacturer, and it all fell into place. Mind you: a 600W class A/B MC² Audio amp replaced a 30W class A Belles over +110dB sensitive MF/HF horns, and it was more than its equal. How’s that for the snooty, preconceived audiophile notion that pro oriented amps can’t sound great?

Speaking of which: having audiophiles experimenting with different amps over their subs is not a prevalent subject nor a even a minor one on these pages, because when subs are used they’re almost exclusively acquired as all-in-one packages with built-in plate amps.
If you’re working from a different platform though and include DIY, not least actively, you’re likely to treat the main speakers + subs as a single speaker system per channel, and not merely with passive main speakers that need subs (with different amps) to be "latched on" as an afterthought. This way you have the means and framework to find out about these things.

It’s a controversial subject even, treating the sub amp with the same care as you would the one used over the main speakers; obviously it isn’t just about having loads of cheap class D power and lots of damping factor, but rather seeing that tonality is very much co-founded in the subs region, and that coherency is greatly aided by using similar amp topology top to bottom. Quality, care and an investigating/experimenting mind matters here as well.

Great seeing that others around here has noticed the importance of amps used in the lower octaves.

@phusis 

with the really important aspect here being using that same amp/its topology top to bottom - that is, over the main speakers as well. 

This seems to be my conclusion as well after a few years of pondering this...

Mind you: a 600W class A/B MC² Audio amp replaced a 30W class A Belles over +110dB sensitive MF/HF horns, and it was more than its equal. How’s that for the snooty, preconceived audiophile notion that pro oriented amps can’t sound great?

It is a good idea if the gems inside pro-audio remain a secret...The price of anything would just skyrocket if every audiophile found out about it (I certainly wouldn't want the "audiophile markup" on some gear).

Speaking of which: having audiophiles experimenting with different amps over their subs is not a prevalent subject nor a even a minor one on these pages, because when subs are used they’re almost exclusively acquired as all-in-one packages with built-in plate amps.

It’s a controversial subject even, treating the sub amp with the same care as you would the one used over the main speakers; 

I have thought about bringing up this topic in the past, but was mostly hesitant to do so because the anti-subjective/anti-experiential (anything) guys who spill into this forum from 'you know where' would probably start degrading the thread in a hurry.

I used to think that it was just relieving speaker woofers from the lower octaves with bass management was perhaps the reason for perception of any improved soundstage, improving fidelity of the upper octaves (upper bass, midrange, etc)...but, i suppose there's way more to it than that, i.e. the accuracy of low bass overtones and the psychoacoustic impact of it, impact on transient perception, etc.... which cannot be measured perhaps.... Michael Borresen got into this topic briefly on some video and i can't seem to track down which YT clip it was. 

If you’re working from a different platform though and include DIY, not least actively, you’re likely to treat the main speakers + subs as a single speaker system per channel, and not merely with passive main speakers that need subs (with different amps) to be "latched on" as an afterthought. This way you have the means and framework to find out about these things.

 agreed...