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Old 2nd July 2006, 12:12 PM   #1
daly2k is offline daly2k  United States
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Join Date: Aug 2005
Default DC offset affect on biamped speakers

I need some feedback on the following issue. I just finished a line array speaker project that was designed to be eventually bi-amped. I plan to use my Aleph 1.2's for the tweeters and my Pass/tharagard A-75 for the mid bass. I have 12-5" ribbon tweeters and 12-5" eton mid bass drivers and I am currently using a crossover pt of 2600hz at 24db. I want to get a digital DEQX system to help with room problems and then use a digital crossover set pt at 96db anywhere from 21-- to --3000hz depending on the sound.

The question is that for the tweeter array I currently have capacitors in the crossover that block DC from the amps on turn on or the usual dc offset. My aleph's offset is less than 50mv and my pass A75 is less than 20mv after warm up. My speaker drivers are series-parallel connected to give me 6.2 ohms. When biamping the amps will be hooked up directly to the speaker drivers with no crossover protection as it is now infront of the amps. Using the equation of V=IA, I get .050v/6ohms=.008ma. With 12 tweeters sharing the load does anyone think I should put a cap in front of the tweeters for protection from DC offset. I am not worried about the midbass drivers as they can take the abuse but with Fountex ribbon tweeters at $100 a pop, I am a bit nervous. I will install fuses in my Alephs for short circuit protection and my A-75 already output fuses. thanks for any advice. dave
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Old 3rd July 2006, 10:35 AM   #2
diyAudio Member
Join Date: Dec 2004
Location: Roosendaal
Hi dave,

I do not longer own a DEQX anymore, (building a MOX) but when you look in the Yahoo group for owners, you will find a lot of best practices.

One of the best practices is to use a capacitor as protection for your tweeters. A lot can go wrong! The capacitor not only protects against DC, but will also help the DEQX. The lowpass will also reduce the calculation time, leaving more room in delay functionality. (You will understand this when you get your DEQX)

Greetings, Harry
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Old 3rd July 2006, 12:48 PM   #3
daly2k is offline daly2k  United States
diyAudio Member
Join Date: Aug 2005
Default dc offset

Harry, thanks for your help, I will look up DEQX in Yahoo and read some of the information. I am thinking to use a 2500uf computer grade cap with a PP bypass for protection. dave
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Old 3rd July 2006, 06:59 PM   #4
The one and only
Nelson Pass's Avatar
Join Date: Mar 2001
My experience is that you can put significant DC on drivers
without too many problems, so I set the offset as low as
possible and sleep soundly at night.

BTW, I bought a much of 4 inch drivers on a clearance from
Parts Express and ran them with with a .6 amp DC bias, and
they actually measured lower distortion
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