• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

AR11B mid-range drivers failure

vinstersroc

vinstersroc

New Member
Hi Everyone,
Great web site! Really interesting and a huge resource of so much great information!
I have a question regarding my AR11Bs. I just finished recapping (replaced the 8 uF caps) and rebuilding the crossovers on a set of KLH Model 6s, circa 1959-1960? (S/Ns 14xx and 24xx range) I found on Craig's List. The speakers sound wonderful. I decided to connect them to my Pioneer VSX DS1 A/V receiver (130 W/channel RMS) along with the pair of AR11Bs. After about 15 mins. of listening, 10 o'clock on the volume control, one of the ARs developed a problem. The volume of the right channel dropped off and I suddenly heard lots of distortion. I determined the distortion was coming from the mid-range driver. Disassembled the AR11 (removed all drivers) and tested the tweeter and mid-range (woofer is OK). The tweeter DC resistance measurement is 4.2 ohms (OK) and the mid-range is testing at 18.7 ohms. Obviously a problem. Quick test on both drivers with a small signal from the amp indicates the mid-range is very distorted and turns on and off.
I am looking for an AR OEM replacement mid-range driver, P/N If anyone has one for sale I would be interested in buying it. Vintage-AR repairs mid-range drivers for ARs but they suggest the possibility of failures in the future unrelated to the repair which concerns me. Thanks to everyone in advance for your help and suggestions.

Update today, 2/22/18. I think the other AR11B of this pair has the same problem. Just noticed today while testing. Have disassembled this speaker and the mid-range driver has failed so I am now looking for two (2) AR OEM mid-range drivers P/N 200010-1.
 
Register to hide this ad
vinstersroc said:
The speakers sound wonderful. I decided to connect them to my Pioneer VSX DS1 A/V receiver (130 W/channel RMS) along with the pair of AR11Bs.
Click to expand...
So just to clarify - were you running two pairs of speakers at the same time on the amp?

Were the impedance ratings of these speakers within the amp's recommended levels?
 
KLH 6 is an 8 ohm speaker. AR 11 is 4 ohms, not sure about the 11b but if it's also 4 ohms, that's a very stressful load for the amp. Likely your receiver requires at least 8 ohms on EACH pair if you're running both A and B outputs at once.

So, the receiver may have gone into clipping (distortion) which is what blew the mids. Usually it's tweeters.
 
The most likely source of midrange failure apart from being excessively over-driven at high volume levels is a problem with the cross-over capacitors in the midrange driver circuit. If the capacitors malfunction (or an incorrect larger uF value is used as a replacement) and start allowing a high level of lower frequency signal information through below the normal cross-over frequency threshold, then the midrange drivers can easily be over driven and damaged even at moderate volume levels. Good luck in finding the correct replacement midrange drivers.
 
toxcrusadr said:
KLH 6 is an 8 ohm speaker. AR 11 is 4 ohms, not sure about the 11b but if it's also 4 ohms, that's a very stressful load for the amp. Likely your receiver requires at least 8 ohms on EACH pair if you're running both A and B outputs at once.

So, the receiver may have gone into clipping (distortion) which is what blew the mids. Usually it's tweeters.
Click to expand...

Agreed, the amp probably did clip but I would have thought at the volume level I was using (10 o'clock) it would have been OK. The drivers are definitely damaged so I am looking for two new AR mid-range drivers P/N 200010-1.
 
stickman said:
The most likely source of midrange failure apart from being excessively over-driven at high volume levels is a problem with the cross-over capacitors in the midrange driver circuit. If the capacitors malfunction (or an incorrect larger uF value is used as a replacement) and start allowing a high level of lower frequency signal information through below the normal cross-over frequency threshold, then the midrange drivers can easily be over driven and damaged even at moderate volume levels. Good luck in finding the correct replacement midrange drivers.
Click to expand...

All original electronics in the speakers. I think I stressed the amp and the old caps couldn't handle the clipping. Thank you for your response.
 
You must log in or register to reply here.
Back
Top Bottom