Want more bass? Seal your speakers

As I stated in a different thread, the inside cabinets of my 1.2 TL’s were not completing hot glued in all of the inside corners and they were leaking air like a sieve from various other locations as well. However, after sealing them up with hot glue and applying Mortite there’s been a dramatic improvement in bass response.

Hot glued areas: All inside corners and cross braces; the 8 nuts that hold the end caps on; the end of the cardboard tube for the bass brace.

Applied Mortite and Dynamat to the MW’s, passive radiator and crossover plate.

Replaced the 8 wood screws in the PR with #8-32 threaded inserts and cap screws. I highly recommend gluing the threaded inserts into the MDF as Richcando suggested, taking care not to get the glue inside of the insert.

Disconnected crimp connectors from every MW and tweeter, applied Deoxit Gold, and then reattached. Disconnected the wire harnesses, applied Deoxit Gold and then reattached.

Now there’s bass!!!

Wow, you really went the distance. I gave my RTA's the seal treatment. Some of the seams looked suspect so I used RTV silicone in all the interior seams. I also did the Moretite around the drivers. There was an improvement in the seal according to the press the PR in and watch the MW deflection test (~5 sec to leak-down vs 2 sec).

The bass quality is improved but I had done the XO upgrade, Dynamat and cabinet damping all at the same time. Therefore, it is difficult to say which helped the most.

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Originally Posted by michaeljhsda2

Replaced the 8 wood screws in the PR with #8-32 threaded inserts and cap screws. I highly recommend gluing the threaded inserts into the MDF as Richcando suggested, taking care not to get the glue inside of the insert.

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Good idea. A couple of my Passive radiator screws are stripped and I think I will do this. Thanks!

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Originally Posted by Conradicles

Good idea. A couple of my Passive radiator screws are stripped and I think I will do this. Thanks!

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The exact same cap screws and hex head bolts like Polk uses can be found at Ace Hardware and Do It Best Hardware. Home Depot does not carry them at my location.

Did you do everything at once?

As for the threaded inserts and Mortite, be careful not to torque down the drivers too much, you can warp the frames.

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Originally Posted by Face

Did you do everything at once?

As for the threaded inserts and Mortite, be careful not to torque down the drivers too much, you can warp the frames.

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Yes, but it took me 3 days... and that was just one speaker. :eek: The left channel should go much quicker now that I have a feel for it. Yes, I noticed the frame on the first MW started to warp when I tightened it down. I figured it was from the fact that the mortite was still in a thickened, rope-like shape so I removed the mortite, flattened it with a roller, then reinstalled it. This resulted in a much better outcome as the frame did not warp when tightening the MW. I used flattened Mortite on the PR and everything locked down nice and snug... no excessive force necessary.

The fumes from some RTV silicones can be very corrosive on metals, might want to inspect things after a full cure has taken place.:)

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Originally Posted by gdb

The fumes from some RTV silicones can be very corrosive on metals, might want to inspect things after a full cure has taken place.:)

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I did leave the drivers out for a few days to allow the RTV to out-gas. But is probably a good idea to inspect.

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Originally Posted by gdb

The fumes from some RTV silicones can be very corrosive on metals, might want to inspect things after a full cure has taken place.:)

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I debated using silicone but I like the idea of how fast the glue cools off and hardens like a rock...without the fumes.

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Originally Posted by michaeljhsda2

... Yes, I noticed the frame on the first MW started to warp when I tightened it down. I figured it was from the fact that the mortite was still in a thickened, rope-like shape so I removed the mortite, flattened it with a roller, then reinstalled it....

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I made the Moretite real thin and torqued the screw just enough to start squeezing the Moretite then re-torqued the next day.

Once you Moretite, it is not easy to remove the drivers. I found a thin L-shaped hex key works well. Slip the short end in the gap and hook it under the edge of the driver and pull straight out.

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Originally Posted by michaeljhsda2

I debated using silicone but I like the idea of how fast the glue cools off and hardens like a rock...without the fumes.

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In hind sight, hot glue may have been the better way to go. Probably takes quite a few sticks.

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Originally Posted by skrol

In hind sight, hot glue may have been the better way to go. Probably takes quite a few sticks.

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It took about 10 sticks but then again more than half of the speaker cabinet was never glued to begin with.

I failed to mention in my initial post that I backfilled every hole in the MDF with mortite so air would not leak out through the threads of the MW's.

Well you all got me concerned so I did some research. The internet is great. It turns out that the GE Silicone II, which I used because I had it left over from doing my bathroom, is not an acidic-type of silicone but an alkaline-type silicone sealant (sometimes referred to as neutral or odorless). It releases methanol and ammonia. While these are not exactly desirable in quantity, they are less corrosive and dissipate much more rapidly than the acidic type.

i sealed my sda's up when i got my x-overs back from ben. I used clear caulking around all of the drivers, and just yesterday i sealed up the x-over cover plate with the same thing, this made the biggest difference. now i do not want to hear that using the caulk is a bad idea, in my opinion it is much better than the rope caulking that everyone else is using, which will be dried up and cracking in a year or so:eek: I did not seal anything on the inside, it looked to be in good shape.

Would these work instead of using caulking?

http://www.speakerworks.com/speaker_gaskets_s/71.htm

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Originally Posted by michaeljhsda2

Would these work instead of using caulking?

http://www.speakerworks.com/speaker_gaskets_s/71.htm

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as long as you get the correct one. all of the drivers have a gasket on the back of them, and the tweeters have a foam gasket behind them, which i put over the top of the caulking. the original gaskets do not seal back up very well once the driver is pulled.

I am not too sure about the paper gaskets. The mounting surface on the Polk cabinets is not real smooth and the paper may not make a good seal. The EVA foam should be ok.

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Originally Posted by skrol

I am not too sure about the paper gaskets. The mounting surface on the Polk cabinets is not real smooth and the paper may not make a good seal. The EVA foam should be ok.

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I agree about using paper gaskets. Foam is better if the correct thickness.

I did the same things to my TL's that michaeljhsda2 mentioned. I also put 4-5 coats of polyurethane on the driver and PR cutouts. The MDF is rough where the cutouts were made, the polyurethane provided a smoother flat surface for the gasket to mate to.

I used wood glue to run a bead around the interior seams and braces that did not have a bead already. To seal air leaks, I put teflon tape on the Bass Brace screw, and duct tape over all the screw holes that went through the cabinet. Made sure the binding posts fittings were sealed. I used silicone when I changed the posts. I removed the top and bottom end caps and ran a rope of Mortite around the studs to seal the bolt holes going thru the cabinet. The back of the xover mounting plate has hot glue to seal and hold a nut in place which holds the large inductor coil. I resealed this as the glue was gone in front of the bolt.

I used Mortite on the drivers of one cabinet. I am going to remove it as the stock gaskets seal just as well. To easy to pull the inserts out or break the MDf using this stuff, and I had flattened the Mortite to the thickness of a gasket before installing it. Hard to get a driver out right after installing Mortite. In a few years it may stick to where you may break the MDf trying to take a driver out!
I have been looking for new 1 piece foam gaskets but not yet found any.

In addition to a rubber gasket, I used a similiar rope caulk I have to seal around new Neutric speaker jacks I installed for the new interconnect cable I made. Used 15 feet of Monster Z2 cable and Neutrik Speakon 4 pole right angle connectors for this. Connected both 12G wires in the Z2 together and soldered this to all 4 poles of the Speakon connector for better continuity. Inside the cabinet I used 10 gauge wire for this new IC connector going to the crossover. Measured at the xover connector, the new IC cable reads no resistance at all, other than the leads connected to my digital meter. 15' is longer than needed for the IC cable but I kept it the same length as my speaker cables. MY TL's are biamped using 8 gauge cables for the low freq's and 10 gauge for the high freq's.

I am upgrading my xovers with new caps and resistors now. Right one done, now working on the left. I arranged new caps and resistors on the xover board differently than others I have seen so I may post some pics of xovers when I am done.

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Originally Posted by michaeljhsda2

The exact same cap screws and hex head bolts like Polk uses can be found at Ace Hardware and Do It Best Hardware. Home Depot does not carry them at my location.

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Do the cap screws work with your PR?

Standard cap screw heads are only .015" in diameter larger than the holes in the PR. That leaves less than 1/100" to grab the perimeter of the PR holes. If tightened too much they can go right thru the PR holes. They make Flanged cap screws but I have only seen these in metric sizes. (These have a "washer" as part of the bolt.)

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Originally Posted by RichCanDo

Do the cap screws work with your PR?

Standard cap screw heads are only .015" in diameter larger than the holes in the PR. That leaves less than 1/100" to grab the perimeter of the PR holes. If tightened too much they can go right thru the PR holes. They make Flanged cap screws but I have only seen these in metric sizes. (These have a "washer" as part of the bolt.)

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The screws are grabbing the outermost edge of the hole of the PR.

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Originally Posted by michaeljhsda2

The screws are grabbing the outermost edge of the hole of the PR.

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They look like Button head screws. I thought you were using cap screws.

My SDA 2B's are about to go under the knife today. I am about to find out about how the mortite comes out/off. I am going to seal all the joints and add some .5 ohm resistors inplace of the jumper on my crossovers. I think I may through bolt my spikes also tho make them more substantial than what I currently have.

Mike I may have a question or 2 once I get the crossovers out.

Scott

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Originally Posted by MillerLiteScott

My SDA 2B's are about to go under the knife today. I am about to find out about how the mortite comes out/off. I am going to seal all the joints and add some .5 ohm resistors inplace of the jumper on my crossovers. I think I may through bolt my spikes also tho make them more substantial than what I currently have.

Mike I may have a question or 2 once I get the crossovers out.

Scott

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Hopefully he took pix during the mods he did, else he may need to stop by if he has any items he needs to check to refresh his memory. ;)

Assuming, of course, you're speaking about the same Mike:D

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Originally Posted by RichCanDo

They look like Button head screws. I thought you were using cap screws.

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Button, caps...still getting my learn on with screwing things :)

liquid nails works really good for me on sealing and strengthening.

Has anyone put Mor-tite on the terminal cups? I would think this is another area that could use a great seal too.

Any reason why I shouldn't do the terminal cups?

I'm going to start with my 5B's first and then move to the 1C's.

H9

I used a low VOC rubberized latex driveway sealer on my speakers to deaden the walls and seal the seams. Took the "ring" out of the MDF.
Ben

It's a funny name but, "truss head" machine screws have a head larger than usual, in proportion to the threaded shank .;)

http://www.advancebolts.com/uploads/.../DSCF2554W.JPG

H9 I used mortite on one of my terminal cups but it got a little dodgy when I was tightening it up so I left the other one stock. The terminal cup will crack if you are not careful. It is probably best to try to seal it from the inside when it is installed.

Scott

Hey Scott, thanks that's just the advice I was looking for. Hadn't thought about the plastic cracking. Not even sure if it's an issue to worry about leakage there. I was just thinking out loud.

H9