I have a Minidsp on order to use as a digital crossover, my Audio Physic Sitara 25 speakers are ported (89db / 36 Hz specification). I use with stereo subwoofers and Vincent SA31MK / SP331MK amplification. I want to reduce the load on the power amp and speakers as the Vincent is class A for the first 10 watts. (Not sure if that means into 8 ohms ? as AP's are 4 ohm load then could be 10 watts or maybe 20 watts?). I will be experimenting and will add my experiences to this page.
Speaker relative efficiency/sensitivity when using a high pass filter
Is there a formula/algorithm/rule of thumb for calculating how a speaker's power requirements might change when the lower frequencies are handled by a subwoofer? Specifically for a ported speaker with a supposed frequency response down to 35Hz and an a 89dB sensitivity with a second order crossover at 80Hz. I know it goes down but by how much? I recognize that power requirements increase as frequency decreases but is the difference enough to allow for a less powerful amp? I would think so.
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@tcutter , if you take the bass out of a speaker with any high pass filter you increase the headroom of the amplifier driving the speaker but you do not change the efficiency of the speaker one iota, it remains exactly the same. Depending on where the crossover is in the speaker you may lower distortion at some frequencies. With a full range loudspeaker this can make a very noticeable reduction in distortion at moderate to high volumes certainly over 80 dB. |
Understood, hence my calling it "relative efficiency". I appreciate that your and Erik's replies are semantically more appropriate. So it appears there is a decrement in the current/voltage required to drive a speaker to only 80Hz instead of 35 or so. I am wondering if there is a formula to determine what the quantity might be. My impetus is that requiring less power allows me to consider lower power amps, perhaps even making Class A available.
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For music, this is correct. :) I would imagine if you started thinking 100W was OK you could do a 35 W amp after high passing it. Truthfully, 100W is overkill for most speakers and your average or modest listening room. I however am not on the Class A camp. I’m not especially drawn to those amplifiers, and the reduced wasted electricity and higher output of AB amps is a much better situation for me. OTOH, if we are talking a sweet tube set up, say a 60 W Conrad Johnson or something, that's something worth thinking about for me. :) |
I am thinking tubes as well but did not want to go down that path and incur/incite the commentary about there being plenty of high output tube amplifiers. Thanks for broaching it. I also want to entertain lower power AB SS amps. I have a fondness for class A from my Aleph 3 days. Again, just wanted to have a better sense of my options, which appear to have greatly increased. |
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