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If I Told You What It Takes to Reach the Highest High...

toddalin

toddalin

AK Subscriber
Subscriber
"You'd laugh and say nothing's that simple."

Hi all.

While often invited to join here in the past, I've finally come around. I was doing some "experimentation" over at the three letter forum and was ousted, at least temporarily, for my unorthodox ways. I was working on modification to the JBL 2402/075 tweeter to expand its performance. Of course I met with stern resistance.

Anyway, this is what I was able to accomplish by putting a 2405/077 diaphram in a 2402 making a 24025. Note that with my "special tweak," (costs nothing on top of the 2405 diaphram) I am able to get the 2402 flat between 10-20kHz while actually (in theory anyway) increasing its dispersion. :music:

I was also able to turn a ~10 dB dip at 8-9kHz to about 2.5 dB.

24025.jpg


DSC_0037.jpg


If anyone has any 2402/075s around and want to make these mods, let me know.
 
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Welcome to AK toddalin....the home of experimentation :D

So tell me, what/why the void in 1k-4k on your meter?

Mike
 
Hi, Todd! :thmbsp:

The thread's gone over there, now, but I believe we determined that JBL actually manufactured this conversion under the model number 2402H-5, i.e., the stock 2402H with the D16R2405 diaphragm, no?

Are you showing a modified 2402H or an 075 in your pic? If it's 075, then perhaps 075-5 might be an appropriate designation.

We were never able to substantiate any 10 dB "dip," in the stock 2402H, as I recall.

Also, what is the basis of your claim of "increased dispersion?" :dunno:
 
Yes, the 2420 (LE85) is turned off so the range of just the tweeter is clearly visible.

Zilch, I know they ousted my thread. (BTW, It is a 2402 AlNiCo - not H.) Wiggles asked me to finalize it. I spend several hours taking new measurements and preparing a summary in MSWord because I knew he would lock it and I would not be able to edit it. When I went to do it, I was denied access to the site.

Increased dispersion is based on simple physics. If you decrease the size of an opening, you increase its dispersion. That is the concept behind the 2405/077.

I found a way to do this with the 2402 while simultaneously "loading" the diaphram that produces the noted spectrum. Plus, I can adjust it to "calibrate" the spectrum so as to place emphasis on any portion between 10-20 kHz. I can actually make it get louder all the way up to 20 kHz.

Of course the trade off is volume, but even flat like you see it, its only a couple dB down from the 2405.

BTW, I can do the tweak to a 2402/075 with a regular diaphram and get near the same curve, maybe down 3-5 dB at 20 kHz at the cost of more volume.

But then what do I know as I'm way out of my element.
 
Welcome to AK Todd. For the most part, we're a friendly bunch open to new thoughts, ideas and approaches. BTW, many of us are ardent fans of JBL and Altec...

To me it seems that for as common as the ring radiators (2402-075, 2404, 2405-077 and 076) are, little is known about replacement diaphragms. A perfect example is your 2402 with a 2405 diaphragm or the 2404 with a 2402 or 2405 diaphragm.

Frankly, I have never cared much for the 2402-075 or 076 although I have never played with them outside of their stock installation either.

In any case, I for one, look forward to your results. Not sure I would replace my 2405-077 diaphragms with something other than the original, but it can't hurt to look at the options.
 
The 2402 has lovers/haters amongst the fans.

I think it sounds fairly decent with a 1 ufd oil cap in series to add a little bit of upper air when I don't have another tweeter horn handy for quick projects.

Crossed lower in frequency will beam like all hell though.

I love them and hate them depending on what they are being used for in the application.

Regards, Ron
 
Not being a JBL-ite, can you explain the numbering thing? I don't even know what I mean. But basically, I have a pair of C30 cabinets with D130s and 075 tweeters. I like the sound, but definitely could use some tweaking as well as a sub.
 
075 is the original (and vintage, of course) Alnico-magnet version of the "Bullet" tweeter, which mounts with a clamp ring, typical. The later pro version 2402 with integral flange, and subsequently, 2402H, having ferrite magnets, continued in production up until just recently.

All use the same diaphragm, though there were minor changes in the aluminum alloy over the years.... :yes:

http://www.audioheritage.org/vbulletin/showthread.php?t=23869
 
As I noted, I can "tune" the response, and in fact can tune the 24025 to look quite similar to the 2405/077, which is less flat then I've shown above.

When tuned like the 2405, it is down ~1.4 dB at 9kHz and down about 0.5 dB at 8kHz from the true 2405. On the other hand, it is still far flatter than the 2405 between 10-20 kHz.

I have the two tweeters (2405 and tweaked 24025) on an instantaneous A/B switch. When listening to music and flipping between the two, ~90% of the time you cannot pick out a difference.

On some songs (that have a perponderance of their vocal spectra in the 8-9kHz range), you can pick out the 2405 as having slightly better intelligibility. OTOH, for recordings that have a perponderance of the spectra above 10 kHz, the 24025 shines. The 24025 also helps the 2420 in better filling some small "dents" in the response at lower frequencies that the 2405 does not help at. :thmbsp:
 
Damage said:
Not being a JBL-ite, can you explain the numbering thing? I don't even know what I mean. But basically, I have a pair of C30 cabinets with D130s and 075 tweeters. I like the sound, but definitely could use some tweaking as well as a sub.
Click to expand...

As Zilch noted:

The 2402 is the same as the 075 bullet tweeter. (And even the later 075s did have the mounting flange as opposed to needing the "horse shoe" clamp for mounting.) These come with a 2402/075 diaphram.

The 2404 is the "baby cheaks" tweeter. In theory, and according to Orange County Speaker, these came with the 2405 diaphrams, though there could be evidence of some coming with 2402 diaphrams from JBL.

The 2406/076 is the "cat eye" tweeter used on the L220. It uses the same magnetic assembly as the 2402/2405. The diaphram is slightly different than either the 2402 or 2405, but no one (at least that I know of) has quite put their finger on the difference. The tweeter is physically longer, and I think this is to lower the resonant frequency as well as accomodate the desired flair rate.

The 2405/077 is the "slot tweeter" which is similar to the bullet but uses a different diaphram and the flair is tapered to a slot with a diffuser running down the center.

The 2402 diaphram differs from the 2405 diaphram in having more "cone area." This is accomplished by using a smaller central ring with the cone making up the difference in spacing.

Though JBL literature indicates that all of the diaphrams are usable in any of the three designs, many, including Orange County Speaker, have reported an interference where the phase plug (the "bullet" if you will) actually touches the 2405 diaphram causing a buzz (or worse). To eliminate the possibility of this happening, I use a 20 thousanths, spacer to ensure that the phase plug does not contact the diaphram. My testing indicates that this spacer has no appreciable effect on the frequency response and the spectra (i.e., 2402 diaphram with or without the spacer) for both look the same.
 
Nice to see yu Todd!

looking forward to more "ABBYNORMAL" torture testing. :thmbsp:
 
Kegger said:
Nice to see yu Todd!

looking forward to more "ABBYNORMAL" torture testing. :thmbsp:
Click to expand...

Thanks.

At this point, I've decided that the 24025 is close enough to the 2405 to serve my purposes so will not be needing to lay out ~$900 for three 2405's, as opposed to just replacing the 2402 diaphrams with 2405 diaphrams.

I may still do some testing using my "special tweak" to see if I can further reduce the now relatively small drop out at 8-9 kHZ (now ~2.5 dB whereas before it was ~10 dB.)

BTW, if I showed what this tweak was (and it is practically free, totally reversable in an instant, and will even work on a regular old 2402/075 to flatten and extend its response..., also at the expense of some volume), the most devote JBL fans would have a cow. The rest of you may just go into hysteria.

But remember, "Even the blind squirrel finds an occasional nut." :headscrat
 
The highest high would be a Plasma-based tweeter. 150000+ Hz. Bat ears eh? :bat:

Rare and toxic... :thumbsdn:

I'll leave it to you to speculate which one my 'thumb-down' refers to: rare, or toxic.
 
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