2395 36" Slant Plate, baffle use?

[louped garouv]

so, I've finally cobbled together almost all the parts needed to start using the 2395 lenses in my stereo....

(except for the bolts needed to attach the lenses to the horn and the longer bolts needed to attach the 2440 to the horn with the 2505 "H" stands)


question....

i think i've noticed some people using a small piece of sheet metal, or something, that also bolts to the rear of the lenses...

kinds of like a mini baffle behind the lenses...

is this necessary? from reading the '76 pro catalog, they seem to indicate that a baffle is not needed unless using the horn down to 500Hz.....

[rs237]

The 2395 is in the back closed. Therefore they need no baffle, think I. Other lenses are in the back open.

regards
juergen

[louped garouv]

I must be missing those back parts that close the back of the lenses then...

thanks!

:)

[rs237]

here a picture.

[Robh3606]

How low are you going to go?? You need a baffle on the back of the lense for use below 800Hz. Take a look in the Library.

Rob:)

http://www.lansingheritage.org/images/jbl/specs/pro-comp/horns-lens/page4.jpg

[louped garouv]

depending on the crossover i use, it's either
800 Hz with 18 db or
1200 Hz with 12db

looks like they would be pretty pieces to fabricate...

Thanks a Million for the pic!

i'll check out the local machine shop prices to see what's what....


here's a little more info on the three way full range sectioned crossover i have...
it's a EQR-5 crossover by a company called "Sound Environments" in NJ...




Your unit with TL082 IC's is just fine. The only upgrade path without
significant changes would be using 353LF IC's which are a nice sounding
BI-FET IC from the mid-late 80's. Do Not just change the IC's out for 353LF's without us doing the mods on the unit. It Will ring and oscillate. Our current units with NE5532's are very different circuit boards with large ground planes on both sides and individual IC
power supply filtering bypasses.

Input Section is:
20Hz HP @ 18db/OCT to Sub-Bass
20Hz HP @ 12db/OCT to Full Range


Output sections are:
Sub-Bass; 106Hz LP @ 18db/OCT - Normal
+4.5db Boost @ 43Hz w rapid cutoff below - EQ Active
Front Panel Control: Unity Gain @ 12 O'Clock. +10db at full CW rotation. Full off at CCW.

Full Range 3-way Section
Low; 1,200Hz LP @ 12db/OCT (derived from subtracting HP from FR)
+6.5db Boost @ 65Hz w rapid cutoff below - EQ Active
Mid-High; 1,200Hz HP @ 12db/OCT (no upper cut off)
High; 6,500Hz HP @ 12db/OCT (no upper cut off)
Front Panel Control: Unity Gain @ at full CW rotation. Full off at CCW.

Tweeters; 7,000Hz HP @ 18db/OCT (no upper cut off)
Front Panel Control: Unity Gain @ 12 O'Clock. +10db at full CW rotation. Full off at CCW.

Hope this was helpful to you. My engineering opinion is that 12db/OCT in the mid band is the best slope for minimal phase aberration in an analog crossover. All filters are Butterworth except my active EQ's which are an elliptical filter of my design.

the other crossover i have is a RLA X2000

the crossovers i use are primarilly designed for nightclub instalation....

[scott fitlin]

Using whatever driver, I would not go much below 800hz with these horns, I use 750hz, no baffle they work fine.

I have seen many installations with 2395 lens horns, no baffles.

JBL did make a smaller lens, for use with a 2in driver that had crinkle plates, and this lens required a baffle to operate correctly. I just looked in our library, I corrected my post, its the 2390. this lens uses a 2in exit driver and needs a baffle to operate correctly, and it also says the 2395 does not need a baffle.

http://www.lansingheritage.org/images/jbl/catalogs/1976-pro/page19.jpg

[louped garouv]

so no baffle, but i need to find/fabricate some of those pieces that close off the back of the lenses off.....


thanks a bunch guys!

:applaud:

[rs237]

I can unscrew, photograph and measure the sheet metal.

regards
juergen

[louped garouv]

thanks for the offer, but I have the rest of the assembly already...

I'll just bring it for the machinist to measure and fit directly...

the picture above is perfect!

[subwoof]

The integral baffles *are* present and further baffling will be of minimal advantage. The 20" lens ( 2390 ) didn't have a baffle but the MA-25 mounting kit solved that.

They will work just fine down to 800 and with a steep slope ( and a driver that can handle it ) to 500.

I've installed dozens of them as a stand-alone HF.

[louped garouv]

thanks Sub (and i don't mean ...versive)


that's what i meant, i won't need external -- non integrated -- baffling

and i'll still be baffled... but in an integrated way -- once i have them made up....

:blink:

[subwoof]

Having the luck to remove a number of these from said installation 20 years later, I found that a LOT of the screws had vibrated out and the ones that were left made them sound like a washboard on certain notes.

I would use a little rubber cement on the screw heads and put a cut-to-fit sheet of the auto dampening rubber inside the side panels ( each side of the horn )

You simply cannot have enough structural rigidity on these puppys....

sub

:cheers:

[louped garouv]

i welcome your tips!
nothing like having first hand experienced folks to guide you....


thanks!

:applaud: