uarnutz

Thanks. Bypass caps will be part of my next PE order.

That's kind of what I expected to hear. In fact, I had bought new caps before I even knew what was in there. I probably would not have done so if I had known. The one thing that may be worth it is that 24mfd cap based on these forums. Replacing with a Munsdorf e-cap has been an improvement for some.

I just acquired a set of AR 91 that are in very nice shape. Just a quick coat of oil and they will look like new. I just had a chance to crack them open for an inspection and possible recap. I found that all the caps are Unicon (made in Japan). Are these OEM? What has been users experience with these in terms of longevity and sound quality? Worth replacing? ( I do not have a capacitance tester)

I just finished a restore of a pair AR 90, including new grill cloth all around. Mine looked original and the side grills were glued together with hot melt adhesive which came apart fairly easily and was not too difficult to remove. I just used black silicone RTV adhesive sealant to put them back together. I could not imagine working with hot melt would give me enough work time and this is not really structural or permanent attachment anyway. The sealant has the added advantage of damping any vibration between the pieces. I am curious what your side grills look like. Can you post some pics?

Exactly my experience even though I had been living with lesser AR speakers most of my life. I may also be upgrading my amp soon. It is hard to resist given the price of this vintage gear. The seller of my speakers had not used them for about 20 years because she was using multiroom ceiling speakers. Their loss, our gain.

Congrats on your new AR 90s. I also recently picked up a pair locally and just had a chance to listen to them for the first time after redoing all the surrounds. I agree that you should just enjoy them for now. The paint job can wait.

Ok. Back to basics. I got around to checking all the polarity of the speakers that I just reinstalled. Sure enough, one of the 10 inch speakers had its connections reversed. All back together and what a difference!. The tympani and bass drum come through loud and clear now. Maybe I will have to keep these after all. Thanks for all the sound advice. Researching 3rd order crossovers and polarity anomalies, just because.

OK. I accept that the polarity difference between the two systems is by design. It seems to be well understood by speaker designers that reversing polarity between drivers can overcome some "bad" effects of certain crossover designs. Still, it is harder to understand why there would be a different approach to polarity between these two systems that appear identical except for the size of the woofers. I know this is off topic for the thread; just wondering.

Thanks. A recap is in the plan but, I tend to follow a step-wise approach in my restorations. I find it is more fruitful to control the variables. When you say that your speakers were wired wrong from the factory, that was based on the DSP test alone, not a trace of the wires against the schematic, right? The DSP reverses phase for you?

So, is the out of phase wiring by design? If so, what is the effect of putting them all in phase? Is that a common "fix"?

Aaah. That's more like it. I started with the polarity at the speaker terminals and the amplifier. Speaker terminals were in phase but, polarity was reversed from amp. So, I reversed the speaker terminals. Shazam! I now have bass to shake the walls. I next reset the impedance on my amp to the Hi setting. Not sure how much difference that made but, it all seems fine. In terms of internal polarity. I could use a little clarification. For the 10 inch speakers, I should go with the color coding on the schematics and assume they are wired correctly from the board? Also, the woofer terminals are not clearly marked for polarity. I assumed that the red dot on the label was positive. Is that correct?

Wow. A wealth of very good information here. Thanks everyone.

I was very careful to label all the terminal wires. Will check again. You think the amp is adequate?

I just did my first audition of my AR 90s. I redid all the foam surrounds as soon as I bought them since they were totally disintegrated. Good news, all the drivers are working and they sound good. I am driving them with a Yamaha a/s 500 rated at 85wpc 8ohms. I can get decent sound level but bass is weak compared even to my AR2ax. Also, upper mid seems dominant and somewhat harsh. I attenuated the UMR one step down and it seems more balanced that way. I am pretty sure that I am not hearing anywhere near their potential with this amp. I have a 2600 cu. ft space on a concrete slab subfloor with cinderblock walls and probably 1/3 of the perimeter is glass. After much research, I have narrowed down my amp choices to vintage NAD 2200/2400 or Adcom GFA 545/5400. It seems that I can pick these up for around $250 which, with a decent preamp, falls within my budget. I would be interested in opinions on suitability of these for the AR 90s. Of course, I am open to other suggestions. The NAD preamps also look attractive since they have decent phono quality which is a requirement for me since a I have a large vinyl collection. For this reason, I am also considering an Apt Holman preamp.

Are you selling? If so, pls PM me.

Thanks everyone. If only it were all that easy...

Eureka. It worked! Here's rev 1 using a professional riggers tape. You know, the kind that sound and lighting engineers use for laying their cables. That was after trying generic duct tape and packaging tape. It's not 100% but, I may still try to find an even stickier tape. What do you think? Thanks for the tip.

Thanks. That's useful input. I am pretty sure the white (PVA) will not do any harm. I was wondering more if it is flexible enough and seals well. As far as I know, they are not meant for non-porous surfaces like the speaker cage and they do not remain flexible. I would have thought one of the urethane adhesives would be more suited to this though they are probably harder to work with. I am also leery of solvent based adhesives for a PU foam. Sorry for all the questions. I know just enough to be a PITA on this since I used to be involved in sealants and adhesives professionally at one point. Hopefully my questions will help others understand as well.

Thanks. Yes, it definitely looks as if it is actually being sucked in under vacuum. I suppose that means the seals are good anyway. Are these drivers the ones that are mounted in a tube? Maybe I should loosen the mounting screws and then apply suction.

I am new here so, forgive me if I breach etiquette. I am preparing to do my first speaker surround refoaming and I have read countless threads on various forums. Not surprisingly, there are differing approaches e.g., using a tone generator vs. shims for centering. Ok. I can make an informed decision on that. What has me a little more concerned is the lack of info on best adhesives to use. Maybe I just did not look in the right place but, do we have any actual specs from the speaker manufacturers for the adhesives they used? I am working on AR speakers and this forum has excellent resources, including original engineering drawings. There they specify particular adhesives by name for the surrounds and cone (i.e., Hapcon 400 and 500, IIRC). Does anyone know what these are/were? Just checking to see what we are basing our decisions on for this. I would tend to go with the original manufacturer spec, if practical.

Thanks everyone. I could not get it to work using the dampening and suction (by mouth, using a cardboard tube.) I can see the crease pulled out but, it immediately collapses back. It seems to have some sort of memory. How wet does it need to be? I actually let a wet piece of paper towel rest on it for a minute or two.

New here and looking for some basic help on my newly acquired AR 90 pair. Some background, I picked these up locally since I had heard good things about them and they were reasonably priced. I have rebuilt Ar 2ax and 4xa speakers in the past so, I thought this would make a good winter project. They are probably more speaker than the boss will allow but, who knows? They are in place for now. All the woofer surrounds were totally disintegrated so, I am preparing to redo the 8 inch and 10 inch surrounds with the Vintage AR kit. All these tested to spec for resistance. One of the UMR speakers (1.5 inch) has a collapsed dome. Is this easily remedied? If so, what's the technique? Thanks for any advice. I am excited to get better acquainted with these fine speakers.