DIY JBL 2235h/2440/2397/2405

[ivica]

Update: I installed TrueXtent Beryllium diaphragms in the 2440's today. The detail of these diaphrams are incredible even after only three hours of break in. Having never heard Beryllium in a JBL compression driver before I was a bit reluctant due to the price, but after selling some other audio equipment that was only kept as "just in case", it was well worth it. One question I do have is why is the recommended frequency by TrueXtent 1000hz when they should be capable of well below that?

Hi srm51555,

owing to JBL 2397 data and the measurements from the forum

http://www.audioheritage.org/vbullet...l=1#post263329

I think that even 800Hz would be too low, as 2397 horn mouth has relative small area. I think that for lower frequency a Yuichi A290 would be better solution, but its DIY construction would be much more complicated project to be realised.

regards
ivica

[srm51555]

I bought my Be phrams new and love them!

They are on 500hz Edgarhorns.

Ron sends...

I've enjoyed reading you audio journey, thanks for it.

Ivica, I've given some serious thought on making the Yuichi horn and would like to build one when I have time.

I'm currently running the 2235's with a Mcintosh MC2155 and feel a bit more power is needed. So my next upgrade will most likely be a purchase of my friends Crown K2.

[Champster]

Update: I installed TrueXtent Beryllium diaphragms in the 2440's today. The detail of these diaphrams are incredible even after only three hours of break in. Having never heard Beryllium in a JBL compression driver before I was a bit reluctant due to the price, but after selling some other audio equipment that was only kept as "just in case", it was well worth it. One question I do have is why is the recommended frequency by TrueXtent 1000hz when they should be capable of well below that?

My 2¢ is that I would echo the 1khz minimum comment. I just recently changed out the ribbed Ti in my 2446's with new TruExtent Be diaphragms. I should preface this with the comment that the following frequency changes were all made at 24db/oct. I started with 800hz and hated the sound. I was so disappointed and thought I made a huge mistake spending so much money on the Be. Since I am all DSP, I listened extensively to them with frequencies ranging from 600hz to 1500hz. At lower frequencies the sound definitely takes on a strange character (how is that for audiophile speak?). For now, I've settled at 1200hz where it just sounds live. At 1200hz, It all came together and blends wonderfully into one seamless driver with the 2123 midrange. Above 1300hz, the midrange and CD don't seem to blend as well and the sound takes on a deeper, throaty characteristic. So, I continue listening to various tracks striving to find the best choice, but think I'm pretty close at 1200hz.

[ivica]

My 2¢ is that I would echo the 1khz minimum comment. I just recently changed out the ribbed Ti in my 2446's with new TruExtent Be diaphragms. I should preface this with the comment that the following frequency changes were all made at 24db/oct. I started with 800hz and hated the sound. I was so disappointed and thought I made a huge mistake spending so much money on the Be. Since I am all DSP, I listened extensively to them with frequencies ranging from 600hz to 1500hz. At lower frequencies the sound definitely takes on a strange character (how is that for audiophile speak?). For now, I've settled at 1200hz where it just sounds live. At 1200hz, It all came together and blends wonderfully into one seamless driver with the 2123 midrange. Above 1300hz, the midrange and CD don't seem to blend as well and the sound takes on a deeper, throaty characteristic. So, I continue listening to various tracks striving to find the best choice, but think I'm pretty close at 1200hz.

Hi Champster,

Thanks for the shown experience using 2446 BE-Tx driver with Bob Smith - like horn with JBL 2123.
As shown in the:

http://www.audioheritage.org/vbullet...ll=1#post58582

"........Here is a curve of a stock JBL 2397 "800Hz" horn. It is decidedly rolled off below 1200Hz. I expect you will get the smaller horn to "work", but I am not sure how well.

Widget...

..In those particular plots I was using a TAD 4001. I have also measured JBL 2441s and they are identical in the lower portion of the curve. The TAD's larger magnet and Beryllium diaphragm gives it a slightly flatter and more extended top end. The two plots were comparing a stock 2328 with a custom adapter.

Yes, I too was disappointed.

Realize the scale is relatively expanded, with 5 dB per major vertical division. The response between 1200Hz and 12KHz, which is where I was using the driver horn combo is +/- 2.5 dB... not to shabby really.

Widget......"

it confirms Your decision as correct.

regards
ivica

[JeffW]

it confirms Your decision as correct.

For his horn, or Widget's 2397-ish horn.

[srm51555]

This horn was built mostly to Widgets horn plans, the difference is the homemade 2" horn adaptor. The internal dimensions of this adaptor are 2" for height and 5" total length. At the time I was unable to source a 2328 adaptor due to lack of project funds. And since it sound good to me and a couple of other ears I never got one. When running my DBX 10/20 there was a need to boost +1db at 1khz, but that could be room accoustiscs. 500hz was the same, I have no way to test at the 800hz point.

[JeffW]

So 1KHz~1.2KHz is going to be about the bottom for your horn as well. And probably not much lower than that for most any horn a person would be able to fit in their house. I just don't think the 1K lower limit was specified by TruExtent because they thought it sounded best there. The design of the horn and the associated loading of said horn is going to have an influence on the lower crossover point of the driver/diaphragm. Champster is using a 2380 I think I recall. It's spec'd as a 500Hz horn, and must guys seem to agree that crossing over at least 2X the horn's lower limit is about right. So something north of 1KHz is going to be correct for that horn, based on the design of the horn - not because of what TruExtent printed on their instructions.

A couple of days before I listened to a TruExtent crossed at 350Hz, I also listened to one crossed at 800 (IIRC), both sounded excellent, both crossed below what was printed on the paper and both on horns that could load them properly below 1KHz (at home environment levels).

You probably aren't going to have a lot of horns that can support much lower than 1KHz, so that's not going to be an issue for most systems, but I still don't think that's why TruExtent printed that figure on their sheet.

[cooky1257]

800hz is fine on the 2397. the none Be 2440 sounds sublime used this way with 2x2235/2405 at either end with as I recall a 3105 x over. This 'Westlake' configuration endured the punishments of many recording studio environments for years too.

[srm51555]

I’ve been itchin for a new project and keep on coming back to the idea of making these into a 3.5way. My thought is to replace the 2235H with a 2206H and then run the 2235H up to 80-100HZ as a sub. I would use an electronic crossover for both the 2235 and 2206. The 2240 and 2405 would use the existing passive network for now until the networks could be reworked for 1200 hz crossover points. The speakers sound great as is but my experiment to gain some power with the Crown K2 didn’t work out as planned. In a bi-amp configuration with the K2 I found the low mid of the 2235 to be lacking. These usually don't get played loud enough for the MC2155 to run out of steam but wouldn’t mind the extra power of the K2 on the 2235’s (only when used in a sub configuration).

[Lee in Montreal]

2235 as a sub? You are asking for trouble. You will soon find their excursion limitations. Not to mention that a sub shall go no higher than 40Hz, or you will start noticing the source.

If you want to go to a 3.5 then perhaps you could use a 2226 for bass and 2245 or any automotive sub for the bottom octave. The 2226 is a potent bass driver if well eq'ed.

Lee

[srm51555]

"Sub" may have been the wrong word. I was thinking more like the 2nd 2234H in the 4435. A proper sized 2226/2245 setup might be a little large for my budget right now, but I have though of it. Thanks, Scott

[speakerdave]

It strikes me that you are not playing at crazy loud levels, so the 2235 would probably work ok as a sub in the box you have, since I believe JBL's B380 is the same size. If you are using this system to play movies you could track down a BX63A or set up a minidsp equivalent so that you do not hit it too hard below cabinet tuning, where the woofer would be unloaded.