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Old 30th July 2011, 10:28 PM   #1
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Default Driver sensitivity

So, I have a pair of satellite speakers that have a sensitivity of about 94dB. I'm having trouble picking a subwoofer driver to go with them. This will be a self powered subwoofer with a plate amp. Do I choose a driver that is less, the same, or more sensitive than what I've got? If I choose a driver that is a lot less sensitive, won't the increased gain required to match the satellites cause a lot of distortion in the sub (I'm assuming the driver has the required power capacity)? If I use one that is more sensitive, how do I pad it down to match if it has it's own amp (maybe that's not a problem)?

It seems that all the subwoofers that go really low have very low sensitivity, which is a problem also, since the gain would have to be so high that I assume they'd have a lot of distortion.

I'm intending to build just a regular vented type of box for this.
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Old 30th July 2011, 10:50 PM   #2
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Since the woofer has its own amp, you aren't really concerned with its sensitivity wrt the satelittes.

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Old 30th July 2011, 10:55 PM   #3
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Quote:
Originally Posted by planet10 View Post
Since the woofer has its own amp, you aren't really concerned with its sensitivity wrt the satelittes.

dave
OK. thanks.

Assuming the driver can handle the extra power, doesn't the distortion go up with greater cone displacement? Don't we want low distortion subwoofers, since we can hear all of the harmonics?
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Old 30th July 2011, 10:55 PM   #4
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the sensitivity figures is just one part of three things you need to know. You figure out how much dynamic range you want then use the sensitivity to figure out how much power you need achieve that range.

example: 1w to your mains gives you 94db output. If you get a sub that has a sensitivity of 87db 1w/1m you need 6.6w going to the sub for it to match (94db). if you want 12db headroom over 94db the sub would need to handle 105.6w and a amp to supply that power. the mains would need 32w to hit the target 12db headroom (106db).
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Old 30th July 2011, 10:58 PM   #5
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Quote:
Originally Posted by dirkwright View Post
OK. thanks.

Assuming the driver can handle the extra power, doesn't the distortion go up with greater cone displacement? Don't we want low distortion subwoofers, since we can hear all of the harmonics?
distortion goes up if you exceed xmax, as long as you stay within the ratings of a driver the distortion is minimized.
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Old 30th July 2011, 11:02 PM   #6
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Quote:
Originally Posted by revboden View Post
the sensitivity figures is just one part of three things you need to know. You figure out how much dynamic range you want then use the sensitivity to figure out how much power you need achieve that range.

example: 1w to your mains gives you 94db output. If you get a sub that has a sensitivity of 87db 1w/1m you need 6.6w going to the sub for it to match (94db). if you want 12db headroom over 94db the sub would need to handle 105.6w and a amp to supply that power. the mains would need 32w to hit the target 12db headroom (106db).
Thank you very much. Interesting. How much headroom is considered a good value? How do you calculate this?

So, let's say I screw up and I make a sub that has 98 dB sensitivity and it's own amp. What do I do then?
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Old 30th July 2011, 11:03 PM   #7
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Quote:
Originally Posted by revboden View Post
distortion goes up if you exceed xmax, as long as you stay within the ratings of a driver the distortion is minimized.
OK, thanks. Do manufacturers provide distortion curves with power input?
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Old 30th July 2011, 11:09 PM   #8
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Quote:
Originally Posted by dirkwright View Post
Thank you very much. Interesting. How much headroom is considered a good value? How do you calculate this?

So, let's say I screw up and I make a sub that has 98 dB sensitivity and it's own amp. What do I do then?

You figure out... "hummm, how loud do i want this to go..."

that's it.

you're going to build your own driver? just kidding

the system dosent have a sensitivity rating, just the driver.
You match the driver with the amp and use design to make sure the driver and amp work together to make the type of sound you want plus about two dozen other things to consider with box design.
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Old 30th July 2011, 11:13 PM   #9
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you might want to start here: WinISD Pro Tutorial and Download (A detailed guide on how to use WinISD Pro) - Home Theater Forum and Systems - HomeTheaterShack.com

or here: http://gonecatfishin.net/WINISD.htm

Last edited by revboden; 30th July 2011 at 11:16 PM.
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Old 30th July 2011, 11:17 PM   #10
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I've been using WinSpeakerz. Is this better? It looks like WinISD has more features.
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