ISOBARIC 16 ohms load powered by 8 ohms Amp - Page 3 - diyAudio
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Old 13th October 2006, 07:40 PM   #21
dangus is offline dangus  Canada
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Location: Vancouver Island
Peavey Black Widows? They're PA or musical instrument drivers.

If this is for home theatre and music, it's hard to go wrong with a conventional sealed sub, with a driver like an Adire Shiva or Tempest, or an NHT1259, or any of the similar drivers. Efficiency is lower than a PA driver, but "Hoffman's Iron Law" means you get a lower cutoff frequency from a smaller cabinet in return.
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Old 15th October 2006, 11:13 PM   #22
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If you want high efficiency 18" woofers that require large enclosures and you want small boxes then the only way to go is isobaric.
Comparing two woofers in an isobaric configuration versus two woofers with their own airspace the isobaric is down 3dB not 6dB, same impedance, same voltage sensitivity but half the radiating area.

All drivers have directional nonlinearities in the suspension and motor and coupling two of them mechanically out of phase effectively eliminates-or at least significantly reduces the distortion generated by them. Buying "better" drivers does not change this fact.
What I dont get is why some people insist that the most important parameter is peak spl, in a musical sense 3dB is trivial and not worth worrying about yet reducing box size by a factor of ~four w/o sacrificing bass extension is well worth the effort.
I always enjoy compact speakers in my room and the resulting increase in floorspace that results but I have yet to run max power to them just to see if they are as loud as winisd or whatever predicts they will be.
When you integrate your subwoofer you have to ask yourself are you going to set the gain so that you get a flat response or are you going to max out the gain so you can run peak spl all day. You are probably going to set the gain to match the mains which means that your high sensitivity, high power handling woofers will have plenty in reserve regardless of how you mount them.
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Old 17th October 2006, 09:06 PM   #23
eddi0 is offline eddi0  United States
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Eureka!!!!!! Isobaric is to save space.....I use this for the sub to my DJ system!!!!

Edward
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Old 17th October 2006, 11:31 PM   #24
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Quote:
Originally posted by eddi0
Eureka!!!!!! Isobaric is to save space.....I use this for the sub to my DJ system!!!!
Huh?
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Old 21st October 2006, 03:29 PM   #25
CarlosT is offline CarlosT  United States
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Since I'm designing a mini isozooka sub and struggling with the same issues I'll chime in. The -3dB sensitivity referenced by a few here is only if you wire the drivers in series. If you go parallel (I am with two 8 ohm drivers), the sensitivity actually goes up 3 dB. The first advantage of an isobaric is the halving of the cabinet size. The second is the coupling of the two drivers in the "isobaric tunnel" which better controls them mechanically.

My biggest problem now is that I'm having a hard time finding internal round PVC fittings to create the tunnel in 6" PVC (see my separate thread on this)

Carry on, Eddio!
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