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OLAs sound screetchy & harsh

B

b-rider

Active Member
I got a set of beautiful early-version OLAs with beveled cabs & very light finish & the tweeters without the metal screen, so I assume they are a very early version. Ser #'s are only (2) digits apart!

Anyway, the masonite woofers have been re-foamed and they are in such clean, straight overall condition I bought them (at a good price, I didn't overpay) without listening to them.

But when I put them next to my other OLAs that have also been re-foamed AND had the crossovers "freshened up" and did an A-B comparison, these new ones sounded really harsh (at the same switch setting) compared to my other set, and the base was definitely not as pronounced.

Without knowing anything else about them, could the old, original, non-serviced crossovers cause this poor high/base performance? Like I said, I don't know if the crossovers have been serviced, I only know the woofers have been re-foamed. At the price I got them, it would probably be smart to give them to the same guy who serviced my other pair and then I'd KNOW the overall condition, just wondering if there is something characteristic about these early versions (denoted by the lack of screen over the tweets) that might be part of the audible difference I'm hearing.
 
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They need to be completely checked out. As RxDx said, lack of bass is almost always an air leak and that will also affect the entire frequency response although not usually make them "screechy". The capacitor values need to be tested.

Out of curiosity, what are the serial numbers? One of my pairs is very early from early 1970 and I bought from a guy from Massachusetts whose parents originally bought them at the factory in Cambridge. They only have four character serial numbers and no "Advent" badges which I have pretty much determined were not on the early units as I have seen others from then without the badges.

Doug
 
Serial #'s are M01842 & M01844. Unless the tweets have been removed and not sealed, the woofers definitely look sealed, no significant areas of potential air leaks that I can see:
20241121_085153.jpg20241121_085153.jpg20241121_085238.jpg20241121_085238.jpg
 
Air leaks are not normally seen. The easiest way to check for a leak is to gently push in the cone of the woofer, by maybe a half inch, then quickly release and watch how fast it returns to the rest position. It should return slowly to that position, in something like 0.5-1.0 sec. An immediate return indicates an air leak. Most common place is the driver gaskets, but it could be where the speaker terminals/switch pass through the rear cabinet wall. This can happen if the crossovers were removed at some point.

I have a pair with serial numbers M0165 and M01567. They had a rough early life, and all drivers had been replaced by the time I got them. I would recommend cap replacements if they haven't been done.
 
Yeah, do the woofer-cone-push-in-test. If the cone doesn't immediately come back out, it's doubtful there's enough of a leak to affect bass response.

Doug
 
Do you know what surrounds they used? The glue job looks a little sloppy. If they used some cheap surrounds that can affect bass response. I’ve had good luck with buying my foam surrounds from Rick Cobb
 
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