Woofer Seal Gasket Recommendation - AR-9 12" Woofer

[wsill]

Hello everyone,

I opened my AR9 to check insides, see if original capacitors ..etc. Actually an impressive set of coils and caps inside.

Question: My sealing gaskets are rock hard, I'm thinking I have air leak.

What are the recommenced sealing gaskets or sealing tape for the 12 inch woofers?

I read in the manual that each time you open the woofer the gasket needs to be replaced; does this sound reasonable?

Here my pictures.

Thanks for your input.

Bill

 

 

 

 

[JKent]

Hey Bill

Yes--those gaskets should be replaced. My favorite is the gasket tape from Parts Express. https://www.parts-express.com/parts-express-speaker-gasketing-tape-1-8-x-3-8-x-50-ft-roll--260-540

However you can, if you wish, pick up a chunk of duct seal, roll out some 1/4" diameter worms and use that. https://www.homedepot.com/p/Gardner-Bender-1-lb-Plug-Duct-Seal-Compound-DS-110/100212441

Or, if you feel confident using an X-Acto knife, pick up a couple of sheets of Creatology foam and cut your own https://www.michaels.com/12x18-foam-sheet-by-creatology/M10597609.html

You didn't ask about this, but FWIW those black and red caps should be replaced. They are probably Callins or Elcap or Temple and are made of black PVC with a different material for the red ends. Over time they leak and drift.

Kent

[ar_pro]

As Kent mentioned, a popular favorite is the Parts Express tape - it installs easily & quickly.

Awhile back, I switched out AR foam gaskets for Mortite, which works extremely well, and is inexpensive. A little goes a long way. Photos below.

https://www.homedepot.com/p/Mortite-19-oz-x-90-ft-Grey-Weatherstrip-and-Caulking-Cord-B2/100152937

It would be surprising if the black & red caps are still within spec - hard to believe, but we're at 40 years on the AR-9 series.

[wsill]

Kent, ar_pro;

Thanks for the information.

I'm going to measure those caps tonight. I  have a fluke multi-meter with capacitance measurement.

I'll let everyone know hoe the measured.

Bill

[DavidR]

My latest pair of AR9's have a white foam tape. It seals very well. I asked the guy I bought them from what it was. He responded: " The material I used to seal the woofers is an adhesive backed closed-cell foam window seal, probably 1/4 in thick X 1/2 in wide. I've used it many times on different speaker projects and it seems to work well. I didn;t like the clay type sealer parts express sells." This guy is a retired audio engineer.

As AR Pro said, the caps are old and tired. I just did my 90's that has many of the same caps and the metal can caps were worse than the black/red PVC caps. Even thou some measured at the high-end of the spec or within spec they did not sound good any longer. The dark veil has been lifted and no more dull sounding speakers.

[RTally]

On 11/29/2019 at 7:09 PM, wsill said:

Kent, ar_pro;

Thanks for the information.

I'm going to measure those caps tonight. I  have a fluke multi-meter with capacitance measurement.

I'll let everyone know hoe the measured.

Bill

Generally, it is not worth the effort to measure caps except for personal gratification. Since you have to remove them from the crossover to test, you might just as well install new caps and be assured of a future, long service life for your speakers. When testing, you need to measure both capacitance value and effective series resistance (ESR). Many times a cap will be within spec for capacitance value but the ESR has increased as the electrolyte has dried over the years. The increased ESR contributes to attenuated mids and highs.

As JKent mentioned above, those black caps with red ends are notorious for failing. They have a reputation for failing catastrophically, as in exploding. Regardless of how they test, I would immediately toss them and replace with film caps.

[DavidR]

2 hours ago, RTally said:

......................................and replace with film caps.

Why film caps?

[RTally]

On 12/1/2019 at 9:30 PM, DavidR said:

Why film caps?

That is a loaded question. At the risk of starting a controversy over caps, . . .

Electrolytic caps are inherently noisier than film caps, but it is questionable if it is audible. The way the electrolyte reacts inside the cap is the source of the noise, as compared to the solid material of other caps.

Film caps will last longer than my lifetime. Electrolytic caps have a limited life, typically 15 to 20 years, maybe 25 for modern ones.

Film caps cost more than electrolytics when looking at economical options. 

Electrically, electrolytic caps better match the original caps in the speaker if those caps were electrolytic. Film caps will have a lower equivalent series resistance (ESR), which will result in a slightly brighter sound. Many add a 1/2 ohm or so resister in series to accommodate the reduced ESR.

For me, I use electrolytic caps when recapping inexpensive speakers that I do not plan on keeping. For the better speakers that I plan on keeping around, I use film caps all around, even in the woofer circuit. My brand of choice is Audyn Q4. If I ever get really expensive speakers (valued at over $1000), I will likely use better quality caps. I do not like spending more on caps than the speaker is worth. I also recap one speaker at a time and A/B test to ensure it is worth it. Usually it is.

[wsill]

Kent, ar_pro, DavidR, RTally;

Ok 2 things.

1)  I used the black duct seal compound; rolled out some nice  strings.

Sealing the woofers changed my AR nine radically- so much better. I kept reading about tight bass, mine had sloppy ill defined. I did suspect leakage.

Anyone if you suspect air leak from the gaskets; see Kent recommendation, get duct seal-- worked wonders for me.

I also did the 8" midrange drivers. I'm just thrilled now.

2) Yes, attempting to remove 1 end of each of those upper midrange, tweeter caps (red and black) to measure is extremely difficult.

I gave up. I think have to decide which replacements to use then cut the old ones out. Though now that the seed is planting on the probability they are way out of spec is troubling. My high frequencies are not muted nor rolled off. They sound very flat though even sometimes I reduce the upper mid-range by -3 db.

When caps fail they maybe increase resistance, but do they raise of lower in capacitance? Are there changes to the high-pass filtering?

If they lower than ok right; I'm not putting lower frequencies into them.

 

Thanks again for all the input and advice here.

Bill

 

 

[DavidR]

13 hours ago, RTally said:

Electrolytic caps are inherently noisier than film caps, but it is questionable if it is audible

Film caps also exhibit microphonics, especially the cheaper ones, and it has been measured and in some cases can be heard. If I can find the article on it I will post it.

I asked because the crossover was designed for NPE and an NPE behaves differently than a film to frequency. I capped my 91s with film and my 10Pi with electrolytic and I really can't hear a difference between them. However, the 91's are on a SS amp and the 10Pi on a tube amp. Based on that I recapped my 90's with NPE.

[DavidR]

 http://www.humblehomemadehifi.com/download/INFO_ClarityCap_Technical_Report.pdf

 

http://www.hificritic.com/uploads/2/8/8/0/28808909/classic-sc15-a_passive_role_with_note.pdf