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Acoustic Sealing


jwjensen356

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There is an interesting discussion in the AR forum "AR Box and Woofer Sealing". The main topic seems to be about how much springiness to expect in the speaker. How slowly should you expect the return to a neutral cone position if the cone was pushed in to its throw limit (say, 1/2") and then released. The AR box is well sealed and the return should be somewhat slow but not too slow.

I was curious how it is in my A-50 (which is a larger enclosure, completely sealed, two sections with the speakers in one, with the Dynaco lossy coupler between the two sections). It does have a slow return of the woofer cones. I don't know how it is with the A-25 (or A-10) which have the lossy coupling to the outside. I would expect the A-35 and A-40 to behave similarly to the A-50.

Comments?

John

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There is an interesting discussion in the AR forum "AR Box and Woofer Sealing". The main topic seems to be about how much springiness to expect in the speaker. How slowly should you expect the return to a neutral cone position if the cone was pushed in to its throw limit (say, 1/2") and then released. The AR box is well sealed and the return should be somewhat slow but not too slow.

I was curious how it is in my A-50 (which is a larger enclosure, completely sealed, two sections with the speakers in one, with the Dynaco lossy coupler between the two sections). It does have a slow return of the woofer cones. I don't know how it is with the A-25 (or A-10) which have the lossy coupling to the outside. I would expect the A-35 and A-40 to behave similarly to the A-50.

Comments?

John

Hi there;

My first experience with Dynaco was working at our local Dynaco, among others, warantee depot.

I serviced only a very few A-50's, A-35's and A-10's and well over 100 A-25 speakers in my short period of this hobby.

The A-25 woofers were by far the weakest link in that series.

Only Sea's woofers were available as replacement units.

The pretty blue/green goop that sealed the drivers to the cabinet also sealed the resistors to the inner cirtcuit board and also the grille cloth frame to the cabinet.

We never received a can or tube of replacement sealant when sealant was needed for replacement drivers.

Because the sealant was still fresh and salvageable, we scraped it and re-used it.

Dynaco used woodscrews to mount the drivers into the routed out flange area.

The Seas woofers had horns where the screw mounting holes were.

There was not a lot of wood supporting the frame at that point allowed for a sealant.

Using something like the Acoustic Research like putty requires a little more torque than Dynaco woodscrews can properly hold without stripping in the wood.

The frame area touching the wood is very small for putty.

Some folks turn the woofers CCW or CW to find new wood surfaces for the screws but you now must be sure to seal the older empty holes.

A glued in matchstick, for example, will make a loose hole a little bit tighter.

The round perimeter Scan frame had a little more surface area for the putty.

You must be very careful trying to play with those woofers.

Early, no dates noted, 10" woofers had bad glue of their coils to their forms.

By pressing in on the cones you may exaggerate this problem and dislodge the coil from the form.

This can be noted by a faint buzzing in the beginning.

Fuse your speakers, don't over-drive them and just enjoy.

Vern

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