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wanna get 6 free dB outta your sub????

1K views 7 replies 7 participants last post by  HW323ci 
#1 ·
Try this: Assuming you did the right thing and built your box SEALED with at least 3/4 MDF (better to use 1" tho) you can squeeze out significantly audible differences out of your box by doing the following:

Buy a quart of 2 part polyester resin, for fiberglass work- it will come with a small bottle of reactant- you only need a few drops for a full cup of resin- like 8 oz resin to 11 drops of MEK (MEK is the reactant- methyl-ethyl-ketone: it is realy nasty ****, so make sure the ventilate and wash hands thouroughly).

Anyhow- pour in about 3/8 to 1/2 inch of resin into each side of the box- just put it flat on a work table and start with the bottom- then do each side. For the driver-panel (the one with the hole in it) use a baffle of masking tape so you have a sort of barrier to hold the resin in place.

A few othe hints: 1) don't ever EVER use screws to hold in the driver that go THROUGH the backside of the driver panel- even though the screws LOOK tight, they DO bleed small amounts of air and cost you dBs- AND clarity.

2) Be sure the seal the corners WELL with RTV- in ADDITION to the resin trick above.

3) don't EVER use one of those stupid terminator-cups for wiring. Simply get yourself a good run of high-quality 12 and 10 gauge speaker wire- make the smallest hold possible in the box to run it through- tie a KNOT in the wire, run that through a 2" diameter metal washer with the smallest hole possible to fit the wire through- RTV the crap out of the hole in the box and run the wire so that the knot is on the inside of the box, the washer BETWEEN the knot and the inner-side of the wood panel where the wire runs through. Literally HANG the entire speaker box by this run of speaker wire- the natural weight of the box will keep plenty of tension and pressure on the RTV so the washer seats nicely and provides a good seal- the resin will take care of the rest.

Try this little trick- perhaps even build yourself a new box- I GUARENTEE you will hear a completely noticeable difference in your sub(s) - I got an extra 7.1 dB out of a single boston 12 (which is quite underpowered by the way, temporarily) by simply using a 1" instead of 3/4 box and getting rid of that stupid teminal cup and using the hung-washer-wire trick and the resin- the sub sounds incredible- so much so that I may not bother adding a seperate amp - this weekend's ski trip will be the decider- If my little P640 can handle powering the whole system as it is configured now without overheating on the way up to hunter (a good 3 hours trip) than it is staying the way it is and I'll be one happy camper.

Good luck- try building a good box and see the difference- you get to save yourself cash on that new sub that you THINK you need...
 
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#3 ·
It is highly unlikely that you recieved an extra 7 db from your box by performing the procedure you outlined. The only way this is possible is if the box was built poorly to begin with. Every 3 db in output is equal to doubling you amplifier power. So for you to recieve 7db gain is like increasing your amplifier power by more than 4 times. Doesn't sound right to me
 
#5 ·
Nice, tip but I think the other two that posted were right. Fully sealing ur box with glass like that will probably yield an increase of 1db or so. Usually nails, glue and a lil foam is enough.
 
#6 · (Edited)
Decible meteres don't lie...And you didn't read close enough

You didn't read closely enough- and I also didn't clarify enough, so I'll call this 50/50: First, a Said I got 7.1 DB by going from 3/4 to 1" AND by getting rid of the terminal cup- you are absolutely right- initially, the box WAS built wrong- terminal cups SUCK and so does 3/4 MDF- especially for a super hi output sub like a boston 12. Going to the new box made of 1" yield 4.0 dB increase right off the bat- and the glass trick got me 3.1 additional- not to bad, in fact QUITE GOOD!

The box is made out of 1" MDF- If you read the post, I think you'll agree that not including the glass trick, everything else constitutes building it right- oh, the "Hang it from the wire and goop it with RTV trick" was given by Boston- and is a really neat trick- works real well!

Hey, you don't believe it- try it- it's not like you're going to sacrifice alot of volume- and besides, unless you have a thiele-small machine (which is probably unlikely) you're volume is probably not exactly perfect anyway.

Funny- Everyone I share this with says "yeah, bull****" and then comes back and says "****, that sub sounds ALOT louder and crisper"

Also, YES, the other 2 posts were right, but misleading: the 3dB per power-double applies to MAX-MAX output... I'm basing it on approx 3/4 volume (Level 27 out of 35 on my Alpine) with no changes to amp gains, or sub level on the head unit. Again- the machines don't lie- I didn't believe this either until my installer decided to put 100 bucks on it- he said I would get at least 2 - 3db, but probably more like 5 or 6. The bet was minimum of 2 db or 100 bucks for me- I said what the hell, nothing to lose!!! for 100 bucks I could build another perfectly made box and have plenty of cash left over, especially because I had a ton of 1" MDF left over from prior boxes. Hey- don't take my word for it- give it a try and tell me if it worked - I was happy to get 3.1 just out of the glass trick alone!


learthworml said:
Nice, tip but I think the other two that posted were right. Fully sealing ur box with glass like that will probably yield an increase of 1db or so. Usually nails, glue and a lil foam is enough.
 
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