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Ian Mackenzie
09-18-2003, 05:04 AM
Guys,

Some of you may be interested in damping tweeks to sweeten those 2307s/08 or hot up your L300s.

Here is an extract of the link below fron a fellow JBL diy Guru Rodd Yamashita. Rodd has been tweeking JBL horns for 20 years and has some handy tips:



http://www.diyaudio.com/forums/showthread.php?s=&threadid=11063&highlight=JBL


"Cover the baffle around the mid-horn and the 077ís with 7mm foam or felt (remove the lens first so the foam goes right to the edge of the horn). Cut strips of the same foam and wedge them between the fins on the rear of the lens, but not more then 10mm in from the back edge. There should be a round area open to the horn mouth. This will help to control any baffle diffraction as the sound wave travels through the lens. Wrap the mid-horn very tightly with some heavy rubber or neoprene. You can use large wire ties to hold the rubber tight around the horn, the more the better.

In the photo, you can see the foam on the baffle and wedged into the back of the fins. You can also see the N7000 which I totally rebuilt with Solen coils and caps. I may eventually replace the L-Pad with fixed value Caddocks."

Happy listening

Ian

boputnam
09-18-2003, 06:57 AM
Yea, but you said nuthin' 'bout this! :eek:

I think herein lies the secret.

Whazzat? :confused:

boputnam
09-18-2003, 07:08 AM
:bs:

I'll get dinged for this, but I call a time out.

Duct tape around the horn sonically does what?

I would think if this an improvement, JBL would've stumbled onto it with all their detailed testing and anechoic experimenting. Same-same for the foam at the horn/lense interface. JBL were happy to do this around cone tweeters, so I have trouble knowing why they would have stopped there, and not benefitted their top technology with the same "acoustic improvement". Maybe they had to wait for duct tape to be de-classified by the miltiary LOL.

In my book, for now, this goes down with those splendiferous surroundless woofers I saw touted on eBay.

"Noise", in my parlance.

4313B
09-18-2003, 07:33 AM
"I'll get dinged for this, but I call a time out.

Duct tape around the horn sonically does what?"

You really do crack me up Bo :)

Maron Horonzakz
09-18-2003, 07:58 AM
I think the BOOK holding up the driver is the key .

luxmanlover
09-18-2003, 11:05 AM
Personally I find a well place copy of Das Boot (in VHS) does wonders sonically.
Kelly

Ian Mackenzie
09-18-2003, 01:14 PM
Bo,

I love it,

However I think Rodd was refering to mass damping of the horn wall.

Apparently all horns self have resonances of there own, particularly a primary resonance, this is perhaps why they sound best operated above a certain frequuency?

Granted alluminium has certain properties for lower transmission of sound than say steel, but it must still have a self resonance point.

If you tap a metal horn what happens? A Ting sound and some decay. While being bolted to a baffle will help sink some of the vibrations, frictional mass damping is more effective. Many diy enshusiasts has reported splendid results with the Altec 811/511, some even using plaster casks.

I accept JBL did not do this with its commercial offering no, but that that does not mean the idea does not have merit.

Perhaps the foam backin helps minimise the sea shell effect, I don't know i have not tried it.

Its interesting most recent k2 designs market a a special low resonance material for their flares? Why not cast alluminium?

Many claim the secret of the smooth natural sound character of the 2397 ies in its wooden construction.

I recall a comment GT made that they could not afford large low dcr chokes in production, one can reasonable assume there are many tweeks that could be made that but would have been costly to production.

Ian

"Wrap the mid-horn very tightly with some heavy rubber or neoprene. You can use large wire ties to hold the rubber tight around the horn, the more the better."

boputnam
09-18-2003, 02:01 PM
Hey, Ian...


Originally posted by Ian Mackenzie
Many claim the secret of the smooth natural sound character of the 2397 ies in its wooden construction. Yea, I do think that is true, but wooden horns resonate, too. I've never been able to A/B wooden versus metal. Widget!!??

But the most interesting thing I've learned, is the size of the book matters most. I think Kelly's got it right! :thmbsup:

"Muhahahaha" - did I say that right? ;)

Say, I know it's 07.00hrs there now, but when DO you sleep, anyway, or work, or... (no cat jokes!)

Alex Lancaster
09-18-2003, 07:47 PM
Remember the 2345's?, they had some sort of tar covering.

How about a 1/2" thick layer of a ionic-interchange resin like a Polyacrylic?

Alex.