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Adjusting for impedance

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Posted on October 9, 2015 at 18:19:07
dbphd
Audiophile

Posts: 1674
Location: Montecito, CA
Joined: September 6, 2006
 While waiting to receive a remote for a Bryston SP3 I bought, I've set all the channel levels in the SP3 menu to zero trim. But, whereas the other speakers are 4Ω, the center speaker is 8Ω. The Parasound JC 1 mono blocks are down from 800 watts @ 4Ω to 400 watts @ 8Ω. The sensitivity of the front LRs is 90 dB, the center 89 dB. Until I trim the speakers, should I set the center channel to +3 or 4 dB to account for the impedance and sensitivity differences?

db

 

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RE: Adjusting for impedance, posted on October 9, 2015 at 19:54:26
Tidycat1
 I would say no.The difference is 1db in efficiency of the speakers.The input sensitivity does not change on the amplifier,even though the amp may drive a 4 or 8 ohm impedance.
Use your ears and make a slight adjustment to the center channel,that is what the channel attenuators are for.

 

RE: Adjusting for impedance, posted on October 10, 2015 at 11:41:52
Pat D
Audiophile

Posts: 12506
Location: Fredericton NB
Joined: June 20, 2000
 No. Speakers are voltage sensitive, not wattage sensitive.

Another consideration is how accurate are the sensitivity figures for your different speakers. The difference in sensitivity is only 1 dB. You can set the gain for the center channel 1 dB higher if you want, but you will still need to trim the gain by some empirical method to get the results you want.
-----
"A fool and his money are soon parted." --- Thomas Tusser

 

RE: Adjusting for impedance, posted on October 10, 2015 at 12:03:43
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 You forgot to mention how much close the center channel is to your listening position than the left and right speakers.

As others have said, use your ears, and don't be surprised if you make no adjustments.

 

RE: Adjusting for impedance, posted on October 10, 2015 at 17:30:34
hahax@verizon.net
Audiophile

Posts: 4306
Location: New Jersey
Joined: March 22, 2006
 Agree. Use your ears. Impedance specs are nominal anyway, the manufacturer's estimate for the dull frequency band since impedance can vary all over the place depending on frequency.

 

RE: Adjusting for impedance, posted on October 11, 2015 at 16:41:08
dbphd
Audiophile

Posts: 1674
Location: Montecito, CA
Joined: September 6, 2006
 I set the distances for the seven speakers and two subs first thing, and the speaker trims are set to zero. I suppose I could use one of the calibration discs I have for trimming speakers, but I've relied on pink noise in the past.

If proof is in listening, I've played enough music Blu-rays to convince me the Bryston SP3 deserves its accolades, and that the zero setting can't be too far off. The Decca recording of Aida from La Scala and LRS Media recording on Legends of Jazz sound superb. The SP3 gives the analog side of my setup, Ayre C-5xeMP and Parasound JC 2 BP, a real run for its money.

Thanks for the advice,
db

 

How many JC 1 monoblocks do you have?! nt, posted on October 12, 2015 at 07:23:18
Inmate51

 

RE: How many JC 1 monoblocks do you have?! nt, posted on October 12, 2015 at 11:07:38
dbphd
Audiophile

Posts: 1674
Location: Montecito, CA
Joined: September 6, 2006
 I have 3 JC 1s, one each for LCR. I run them in low bias mode where they are Class A up to 10 watts. I doubt I ever get near 10 watts.

db

 

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