How to judge an amplifier's performance with a "powered-woofer" speaker?

Hi mike,

Great questions.

While designs may vary, usually the bass section will offer the amp a high resistance value, say 800 Ohms instead of 8. This limits the current the amplifier has to provide in this range to 1/100th of the original. This lets the amp perform like it has a much bigger power supply and with a much higher effective damping factor, but the tonal qualities, including distortion and noise, of the amp are still in play.

However, without a line level (before the amp) high pass filter, the main amp still has to cover the entire voltage swing of the original signal.  In other words, it's a small win for the amp, but it could be even bigger.

Vandersteen seems to have this part covered pretty nicely, with a line level high pass filter and the speaker’s amp designed to compensate with it. Quite clever.  This effectively removes the bass V signal (most of it!) from the amplifier output, making the amp's voltage swing much smaller.  It's a feature professional systems take advantage a great deal, but usually we don't worry about it for home.  To give you an idea though, maybe you can now use a 30W Class A amp if you have a high pass filter, to reach the same levels than before you had a 200 W. 


Best,

E

I've had a few speakers with powered bass and a few without, and weirdly it was easy to tell amp changes on the powered guys. Even though they don't have a load on the low end of the spectrum, the amp still typically contributes down to 80hz, maybe lower, depending on the crossover. 

Anyways, the powered bass gives you a lot of flexibility to try different amps so I really like them. Trust me, you'll hear amp differences just as fast as you would with a passive full ranger. 

MIKEPAUL that tells you all you need to know about all audio magazine reviewer not about audio but money