Bret and other ? on AR90

[roundhome]

The AR90's I just picked up are in vary good shape pulled the woofers and lower mid for refoaming all drivers work.

the ? is in the crossover the 80 uf cap and the coil are swapped compaired to the crossover on file in the lower mid.

does this make any diff. I plan on recapping these one at a time so I can listen to the difference.

thank you

Jim

also any tricks forr bypass caps?

[Diamonds&Rust]

80 uf cap and the coil are swapped compaired to the crossover on file in the lower mid.

does this make any diff. I plan on recapping these one at a time so I can listen to the difference.

thank you

Jim

also any tricks forr bypass caps?

You know, I can't think of any reason it would make a difference, but I think I'd put it back together like the schematic shows it. Are you sure you aren't looking at the junction with the 30? (if that is a 30...I can't see the schematic well enough to read it online).

You know, there are nearly silent members on the board that always use by-pass capacitors, and there are nearly silent members (and not so silent) members who prove mathematically that using a tiny by-pass capacitor cannot possibly change anything audible.

Then there's this other member who emailed me to tell me why this works (it's working by changing the physics of the capacitor being by-passed; NOT "passing" ultra-sonics that we somehow hear).

And yet someone else talks about "unequal sharing" of current caused by cascading capacitors...without telling me what possible difference that could make.

Me? I'm still on the fence on this. Sometimes changes are so small that it is entirely possible that I've prejudiced myself into believing something that isn't true. On the other hand, I really am sure about some changes.

Take, for instance, the case of a friend of mine who recently (because he didn't have new 2500uF caps) "by-passed" his 2500uF capacitor in his 10pi's. No question, none at all. Stuff changed. For the better? Well, yeah, but it sounds a little strange. We will know more when we replace the 2500uF capacitor, hopefully soon, but it was almost like we introduced a filter that was working in the midrange. Don't worry about the specifics, just know that something changed and there was "more" (better) but it sounded "tilted" toward the midrange and isn't pleasant. We have no idea what we ended-up changing that we didn't intend. But it wasn't what I'd call an unqualified success. But the difference was *huge* because the 2500uF capacitor in the speaker is so bad. I suspect we changed, substantially, the "curve" of the ESR of the capacitor.

I will use by-pass capacitors on tweeters and midranges from now-on under the theory that it doesn't hurt anything and costs very little.

Bret

[KlausDK]

The ? is in the crossover, the 80 uf cap and the coil are swapped compaired to the crossover on file in the lower mid.

does this make any diff.

Also any tricks forr bypass caps?

Hi Jim

I also found the coil and the cap for the lower midrange swapped in my AR.90, and I remember to have discussed this with Richard in Australia (rlowe), who also found them swapped in his set of AR-90's. I don't think either it makes a difference, and I did not change it when restoring the speakers.

Regarding bypass caps, I much agree with Bret, it does make a difference, the question is also as Bret points out, if it is to the better. I always bypass tweeter caps, a 4-6 myF I would bypass with a 100 nF, a 10-20 myF with a 200 nF; I also occasionally bypass midrange caps e.g. for a 40 - 50 myF I have used a 400-500 nF. I am not as sure about the effect of midrange cap bypass as I am with tweeter's, but I have not spend the same effort on listenning as for tweeters.

Bypass capacitor material is also an issue. There is a potential problem of bypassing e.g a polypropylene capacitor (which I guess most of us is using for capacitor replacement) with a capacitor of different material, because the different materials characteristics are not the same. In my experience this shows if you use too high a value for the bypass, e.g. I used a 470 nF with a 5.7 myF to make it up for my LST's 6 myF tweeter cap, and this was no good, harsch and unfocused. When I changed to a 100 nF the resulting sound was superb.

"Bypassing" with capacitors of equal make/brand, eg composing a 6 myF with a 5.6 myF and a 0.47 myF of exact same make of capacitors, also improves sound, here by reducing the ESR of the higher frequencies, I often split caps, eg for the 10 myF i an AR-10Pi and 11 I would use a 6.8 and a 3.3 myF of same brand and a smaller bypass (100-200 nF) of diffferent material. I have experimented mostly with polycarbonate and polystyrene bypass capacitors, and they have different effects on the sound. The polycarbonate gives the sound a warmer twist, more tube-like if you want, whereas the polystyrene gives a more precise and analytical twist to the sound with an improved soundstage.

I use mainly polystyrene capacitors for bypass.

So in short, yes I think bypass caps improves sound, but how you like to have your sound improved is up to you, you have to try for yourself. Remember in the AR-90 to bypass both the 4 myF and the 6 myF tweeter caps.

This site has been refered to before, it gives a second opinion on different caps: http://www.humblehomemadehifi.com/Cap.html

BRgds Klaus

[Carlspeak]

North Creek Music systems, a generally recognized supplier of upscale speaker DIY'r parts, used to heavily push bypassing. Of course, they were trying to sell caps in the process. Checked there website today and see no more evidence of it though since they have drastically scaled back operations recently. If I look hard enough, I may find their white paper on the subject published some time ago.

[rrcrain]

North Creek Music systems, a generally recognized supplier of upscale speaker DIY'r parts, used to heavily push bypassing. Of course, they were trying to sell caps in the process. Checked there website today and see no more evidence of it though since they have drastically scaled back operations recently. If I look hard enough, I may find their white paper on the subject published some time ago.

Bypassing seems to be another of those hot topics people become passionate over. I've read North Creek's papers and they are very convincing, and I've read others papers arguing against bypassing and they are equally convincing. My opinion is rather simple. Try it and decide for yourself. If you think it works, great, if not, remove the caps.

One bit of advice on recapping the 90's; Leave the switch assembly in place. As dead as they are before you recap them, the tweater and upper mid absolutely come alive afterwards and may need toning down depending on room dynamics. Mine were so incredibly dead before recapping I couldn't hear that one of my upper mids had died.

Richard