Horn question

[lordvader]

I've taken a sudden interest in horn speakers (and high efficiency overall), so I took a browse through Avantgarde's website.

Something didn't add up. Their speakers have an efficiency of about 107dB. They come with active sub-woofers which have similar sensitivities.
If you can drive a 107dB speaker with a 3W amp, then why would the sub have a 250W amplifier? Being so efficient, you'd think the whole system can be driven off one 3W amp with a simple passive x-over.

Is there something I'm not getting? (this sudden interest is a day old

 

[Brett]

The Uno and Duo use horns above about 200-250Hz (Trio 100Hz)which are 107dB and so only need a very small amount of power as you state. However the subs they use, have drivers which are nowhere near as efficient because they are only direct radiators. So they power them with a much bigger amp and set the gain structure up so that whilst the mid/highs are only using, say, 1 watt, the subs are being driven with 50W or so [figures are my guess at sensitivity of the bass drivers being in the low 90's] to match the apparent levels of all 3 'drivers'. Avantgarde use a feedback system to get the 18-25Hz system response they quote, so I gather some eq is also part of that, which will consume even more amplifier power at any frequencies that are boosted.

Avantegarde have used direct radiators to get around the problem of size in bass horns. My new bass horns will be pretty flat to 30Hz (better with a smidge of eq) and will take up 32 cu ft. Each.