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Hi all,
I have a pair of Acoustic Research 210 B bookshelf speakers that have developed a nasty buzz in the right channel. I've checked all connections and the drivers themselves and am thinking it might be the crossover (it came unglued, which may have stressed solder joints). Instead of just resoldering the existing components, I thought I could upgrade at the same time. It is kind of a weird crossover - basically it is a second order crossover, but only on the tweeter. The woofer has no crossover whatsoever. (it is a 2-way speaker). My ascii art is really bad, but maybe you can understand this:
C1
+ -------)|-------- + tweeter
)
)L1
)
- ----------------- - tweeter(if my ascii gets condensed, the inductor is after the cap (on the tweeter side)
again, the woofer is connected straight through. This seems strange to me, but maybe the woofer has a natural 12db/octave roll off??
Would adding a low-pass filter to this crossover help it? Also, is there any way to measure the value of an inductor using a standard digital MultiMeter (without capacitance or inductance settings)??
I was planning on getting the cap value from the labelling on the cap itself (and maybe get one better than +/- 10% ...)
Thanks in advance for all the help
Joshua
joshua@willowisp.net
Follow Ups:
I don't think AR left out an important inductor in the woofer circuit just to save money. One of the advantages to making your own drivers (which I believe AR does) is you can tailor their natural response any way you want. I'm sure AR designed the crossover and chose the crossover point to take advantage of the woofer's natural response and to minimize components. By adding an inductor where none is needed, you would change the woofer's crossover slope from 1st or 2nd order to 2nd or 3rd order. This may have the unintended result of screwing up the phase response and creating a hole in the frequency response of the system. I'd upgrade the capacitor in the tweeter section of the crossover, but leave the woofer as is. Don't change the inductor in the tweeter circuit either.The only way I know of to measure inductor values is with an inductance meter or bridge.
Hi,
Thanks for the detailed reply. I am wondering whether to use a 4.7 uF or 5.1 uF cap in place of the stated 5. Should I just try both?Also, is there any danger in playing around with the other parts of the crossover circuit? I was planning on retaing the old parts in case my ideas didn't work.
I am guessing at a L/R or Bessel 2nd order on the tweeter. This would give approximate values of 2800 Hz and 3300 Hz, respectively. This seems to be in the right range for other driers that I have looked at (tweeter / woofer common frequencies)
The only reason I am interested in experimenting with this speaker is that it is a well known 'quantity' to me and I think I would be able to hear subtle differences more easily. I would be doing the tweak stepwise.
Thanks again,
Joshua
joshua@willowisp.net
I'd go with a 5.1uFd for the cap. Since the tolerances of Solen caps for instance are 5% that means you will get somewhere between 4.85 and 5.36 uFd. I've built zillions (well maybe only billions) of crossovers and anything within that range will work fine. You can mess with inductors but remember, you have to replace existing inductors with inductors of equal resistance as well as equal inductance. I'd also see if you have cheapo resistors that could be replaced with 10W non-inductive types. The components you would need are available from Madisound (www.madisound.com) or Parts Express (www.partsexpress.com). Both have good prices and terrific service.
.
Joshua
joshua@willowisp.net
In my previous post, I stated that my crossover was bad. I was wrong, it was a cable. However, my crossover still sucks.(see above-yep, that's the whole thing)
The capacitor shown is labeled as a 5 MFD 50 Volt, +/- 10%
I cannot believe that it is a 5 milliFarad capacitor. It is tiny. I could easily believe that it was a 5 microFarad capacitor. If it is indeed a 5 uF (micro), should I replace it with a 4.7 uF or a 5.1 uF??Also, from searching the archives, I see that most people recommend not replacing inductors, but this crossover is such crap that I think I could only help matters. Is there any way to guess at what the value might be? I don't have measuring equipment.
I know that if I knew what type of crossover it was, I could calculate the theoretical value, and if I had to place money on it, I would bet Linkwitz-Reily. Does anyone know what AR had a predilection for using (late 80's early 90s bookshelf - 210B)??
Thanks in advance, sorry to be so verbose.
Joshua
joshua@willowisp.net
It is 5 MicroFarad.
MiliFarad is marked as mF.
Microfarad is marked as uF, MF, or real sign for micro.
.
Joshua
joshua@willowisp.net
My ascii was destroyed, so please see image.
(This image was stolen from lalena.com and modified, but I am not using it for any commercial purpose)
Joshua
joshua@willowisp.net
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