Need help updating the crossover in some large advents

[sterfry99]

Hi,

I bought some original large advents(I believe) I like the sound but they have some problems. When the high frequency switch is turned to anything but extended there is no output from the tweeter.

It looks to me as if they are OLAs that the tweeters has been replaced in. If so, how should I go about updating the crossover?

-Thanks

[Carlspeak]

Please remove the woofer and stuffing and take a picture of the crossover. It will help emmensly with our ability to help you.

[JKent]

Hi Sterfry and welcome

Yes, those are OLAs and yes, the tweeter is not original. May be a good idea to pull one and look for identifying markings. OLA tweeters are often available on ebay and commonly sell for under $20 each. Your best bet would be to replace the tweeters. You can always update the crossovers with new film caps or go wild and do a complete upgrade, but they still won't sound right with the wrong tweeters.

Lots of info on my OLA restoration in this thread: http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=6623&st=20#entry89083

Take a look at Pete Basel’s Advent page: http://baselaudiolab...VENT_LA_XO.html He may well chime in on this.

Kent

[sterfry99]

Thanks for the quick response. Here are some pictures of the crossover and tweeter.

The marking on the tweeter says 85c00019 223tnd if that is helpful

I will look into finding some replacement tweeters then.

[Carlspeak]

I don't recognize the tweeter. In any case, you'd be better off getting some originals of the bay.

The silvery looked cap on the right may be a 16 uF or an 8. It looks like the label has peeled apart - perhaps due to swelling? Let us know what the label says on that silver one. There's also a 3 ohm resistor under the silver cap.

A recap normally consists of replacing the caps and a minimum and sometime the resisotr; which is optional.

The switches usually are not the problem.

[JKent]

The silvery looked cap on the right may be a 16 uF or an 8. It looks like the label has peeled apart - perhaps due to swelling?

That would be bad. The missing plastic film could cause a short. In any case, I'd replace that cap (so you may as well replace them all).

Kent

[sterfry99]

I found the missing piece of film. It's a 16.

I believe that the tweeters are from a 5002 and from what I have read they should sound better than the egg tweeters. Do you think it would be possible to just modify the crossover to suit these. They sound pretty nice now even with the crossovers in that shape.

[JKent]

I'd wait for PeteB to respond. He has a lot of experience with the OLA

Kent

[Pete B]

Your system is what I refer to on the web page as a Rev1 system. The red button inductor looks like it might have overheated and I would measure it with an ohm meter. It should be about 2 to 2.5 ohms, be sure to zero your meter. I would go back to the original tweeter if you don't mind purchasing them. I find the eariler LAs to sound better and I've listened to them side by side. I'd convert them to Rev2 by reducing the increase cap to 8 uF and replacing the red button inductor with the value used in Rev2.

If you prefer to use the newer tweeter you should at least decrease the first cap to 7 uF rather than 16uF, reduce the increase cap down to 4 uF, and add 30 uF in series with the new tweeter. Replace the red button inductor with one closer to that used in the 5002 to make it as close to the 5002 crossover as possible.

The resistors are shot if the tweeters only play on extended and this is a sign that they have been over driven. This also explains why the red button inductors look shot.

[sterfry99]

When I opened up the other speaker the red button inductor looked even worse, so I will replace those. Would parts-express be a good place to find those?

I think I will stick with these tweeters for now at least and see how they sound with an updated crossover.

Thanks for the detailed advice!

[Pete B]

If you are going to stick with the 5002 tweeters, then be sure to use the smaller cap, 7uF, 8 would be close enough, and the rest as I suggested above.

This inductor will work fine:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=255-040

It would be better to move the hot lead of the inductor to right after the first cap as it is in the 5002.

Madisound has surplus 10uF poly caps for $.60 and you can put 3 in parallel to make up the 30 uF.

A .6mH 20ga air core from Madisound is also fine for the inductor.

[Pete B]

Another thing to consider is that the original tweeter face plate sat probably 1/8 to 1/4" further

forward so that it just touched the back of the grille, any gap is going to cause diffraction and

possibly cavity resonances. It is best to space the tweeter forward with something that will

maintain an air tight seal. You could test with a lot of mortite and you might find that it is good

enough if you use enough of it. I'd also use flat head screws to minimize any gap.

The original speaker was very well thought out and having that gap is just not right. I'm

certain that it would measure very poorly.

Also, someone put goop on your woofer dust caps which is a very bad idea. It is not easy to

make a 10" woofer play cleanly up to 1 or 1.5 KHz and here too the woofer was an excellent

design. No one should think that they can do better by adding goop or changing the dust

cap. The original cap was engineered to work correctly, any replacement or goop added is

a complete unknown - most likely, almost guaranteed inferior. Henry really knew what he

was doing!