I am building a LM3886l gainclone class AB amplifier to power my 2 front LR and Center channel speakers - all are 2 way speakers with 2x6.5" woofers and 1" tweeter so each speaker will be consuming 2 channels and will be crossed over with a minidsp. I am using ARTA Limp to measure the speaker impedance and although all my speakers are 8ohm nominal rated from manufacturer, they all spend most of their time at 4ohms based on my impedance measurements in ARTA.
Here are the measured results:
L&Rs (Polk Audio)
Fs: 34hz
VAS: 33liters - fairly high for 6.5" woofer they are very compliant
Impedance Response: 4.1 ohms from 100hz to 1,500hz
Re: 3.6ohms
Tweeter
Fs-1,200hz
Re-4.6ohms
Impedance - 4 ohms from 2,000hz to 10,000hz
Center channel B&W LCR 600 S3
Rated 8ohm nominal (min 3.2ohms)
Impedance Response Measured - 4.2ohms from 100hz to 1khz
Tweeter drops to 3ohms at 10khz
So, my design decision rests on whether to bridge my amp chips or parallel...my problem is that both manufacturers rate these at 8ohm speakers however if I design a bridged amplifier with the LM3886, its going to have a minimum acceptable impedance of 8ohms and these speakers to me look more like 4ohm nominal loads.
Then again, I could also parallel the chips to drive 2 to 4ohm loads-I am hesitant to do this as well because perhaps there is a capacitive or inductive aspect that I do not know about that makes the amp see these speakers as 8ohm loads?
Any opinions are greatly appreciated, what do you think is this a 4ohm speaker and should I design based on a 4ohm load or should I treat them as 8ohm speakers and Im missing something here that makes these an actual 8ohm load. I am used to using Dayton Audio speakers whose speakers - if rated at 4 or 8 ohms- will actually measure at 4 or 8 ohms respectively. Their 8 ohm speakers never drop below 8ohms and same for the 4s
Here are the measured results:
L&Rs (Polk Audio)
Fs: 34hz
VAS: 33liters - fairly high for 6.5" woofer they are very compliant
Impedance Response: 4.1 ohms from 100hz to 1,500hz
Re: 3.6ohms
Tweeter
Fs-1,200hz
Re-4.6ohms
Impedance - 4 ohms from 2,000hz to 10,000hz
Center channel B&W LCR 600 S3
Rated 8ohm nominal (min 3.2ohms)
Impedance Response Measured - 4.2ohms from 100hz to 1khz
Tweeter drops to 3ohms at 10khz
So, my design decision rests on whether to bridge my amp chips or parallel...my problem is that both manufacturers rate these at 8ohm speakers however if I design a bridged amplifier with the LM3886, its going to have a minimum acceptable impedance of 8ohms and these speakers to me look more like 4ohm nominal loads.
Then again, I could also parallel the chips to drive 2 to 4ohm loads-I am hesitant to do this as well because perhaps there is a capacitive or inductive aspect that I do not know about that makes the amp see these speakers as 8ohm loads?
Any opinions are greatly appreciated, what do you think is this a 4ohm speaker and should I design based on a 4ohm load or should I treat them as 8ohm speakers and Im missing something here that makes these an actual 8ohm load. I am used to using Dayton Audio speakers whose speakers - if rated at 4 or 8 ohms- will actually measure at 4 or 8 ohms respectively. Their 8 ohm speakers never drop below 8ohms and same for the 4s