10Bs a Buzzing (help required)

kenwstr

OK so I amused myself with the title on my 1st post, but let me explain.
I recently acquired a Yamaha A700 amp and Polk 10B monitors form my late Mum.
These are by far the highest quality audio I have ever owned so I don't want to go out and replace them. The monitors are in exceptionally great condition and I have had the amp serviced and it's absolutely wonderful, except I occasionally detect a little buzzing. While playing Fleetwoods "The Dance" PCM stereo DVD, I noticed accentuated buzzing from the left channel during "Songbird". I suspect some kind of mechanical resonance. I swapped the monitors across to the other lead to confirm it's definitely the monitor itself, not the channel signal.

What might be causing it and what can I do?
I am a bit handy so can pull out drivers and do repairs on cabinets etc if I have too, but I'd prefer to get advice first as it's likely someone has experienced similar issues.


Regards,
Ken

F1nut

It could be a damaged spider on one of the mid-drivers. It could be loose basket screws on one or more of the mid-drivers and/or the PR. It could be air leakage from the loose screws and/or the cabinet. Try this, push the PR in and hold it in while watching the mid-drivers. Both should pop out and slowly return to rest in between 3 to 5 seconds. Report back.

kenwstr

Ta, F1nut you gave me an idea how to tackle this.

So, both mids pop out together and takes about 2.3 sec (timed) to return to original position together. I tested both monitors and both are exactly the same in this. I then powered up and played the track. Pressed very hard on each screw on every element and on then on each grill peg just to be sure. No difference in the buzz. Using a pair of thick winter socks, I damped each cone in turn and found it's the tweeter that is buzzing. It doesn't seem to be a mounting issue but generated within the element.

This is not usually present, just occasionally I have thought, I think there's a buzz and then it's gone again but this particular track does it a lot so I think it's frequency and power related. The volume needs to be up a bit to get it but not excessively so.

So, what to do, maybe it's time to take it to a speaker guy and see if something can be done? I just know it's going to annoy me now.

Ken

F1nut

Ok, good work. Since it is tweeter related (as in shot) I suggest you replace those awful SL2000's with the Polk replacement model RD0194-1. It is a much better tweeter, period.

kenwstr

There's a replacement available! Fantastic. Does that require testing and tweaking crossovers or just a straight up install?

Ken

motorhead43026

The RDO tweeters are drop in, plug in, and play.

boston1450

Drop in replacement. Make sure you KNOW which tweeter you have now. That way you get the correct replacement. Also. You can switch your tweeters around now & if it follows you know that is the problem ...... SL2000 tweeter pic

boston1450

Call Polk & they can be ordered. Tell them your a member & get a nice discount. Welcome to the forum

kenwstr

Thanks all, my tweeters have V shaped line, not like the above image. I assume the model number will be on the back. I'll be sure to check as I recall discussions where different tweeter models were used in 10B over time.

Ken

boston1450

Probably the SL-1000 post picture if you can..SL-1000 pic

If it looks different it could be a Peerless tweeter. Not sure if the earlier models use them.

kenwstr

That's it exactly.

Ken

boston1450

Id switch them around from 1 cabinet to the other & see if it follows & while doing so-check you wire connections to see if they are connected snug. Then you know its a issue for sure... Another ? Is does your speakers have a fuse on back ? If so make sure its clean-with good contact

kenwstr

OK, I'll do all that. I inherited this system recently and re-terminated the speaker cables and deoxited every connection on setting up but I am not certain I did the fuse though I recall thinking I should.

Ken

boston1450

Can always just change out the tweeter from Ebay or if someone has a spare.... Im not sure there is a drop in replacement with the SL-1000 without doing a crossover upgrade (someone can chime in).... I had the 10's with SL-1000's & i liked them tweeters a tad bit better than the SL-2000's personally. Even though there are some here that dont care for the 1000/2000 tweeters. There are folks out there that have enjoyed them for 25+ years....

westmassguy

The RDO-194-1 is the replacement for the SL1000. Unlike the SL2000, some modifications must be made to the inset, it's not an exact fit. No crossover modifications are needed, but the electrolytic caps are well past their prime.

tat

I just got a pair of 7's with silk dome holed Peerless (the RDO-194 is similar and silk Ive heard), followed by SDA CRS with the SL1000's. I loved a pair of CRS+ I bought new back in '90 with the SL2000's, but I must admit the Peerless silk are much easier on the ear. Perhaps especially with lower quality sources like mono jazz albums and FM radio. The CRS outperforms 7's in every other category easily, but the tweeter weakness is impossible to ignore. Im just saying, replacing it may have the best bang for buck in improving tone, and you already have half the money since you need one anyway. There is a SL1000 on ebay now for $50. + shipping used; brand new pair of RDO 194's arent much more than $100. I dont think. Im not sure the stock XO would be optimized for the RDO's but anecdotes around here are big improvement without any XO change in many models.

kenwstr

I installed a pair of RDO-194s today. I didn't recess them in as I wanted to do a listening test before modifying the box. So I just made up foam gaskets to fill the space and the seal is better than before. The sound is significantly more refined, really nice, smooth, lovely. There is not the least buzz, the whole afternoon, not even while playing in Songbird. I read that Polk research found inseting the face flush gave better tweeter performance. I will probably do that at another time. I also found someone selling peerless reproductions they had custom built. I don't know how these are, they don't seem to have the hole in the dome. I have the 194s now anyway.

Ken