Large Format Compression Driver Listening Impressions

[Robh3606]

Hello

Curious about others experiences with these drivers. I got a big surprise when I started listening to my 476Mg's that I didn't expect. I have 2435's in my 2 other horn/waveguide systems and was a bit shocked by the differences. The 476's are so relaxed and the dynamics are really impressive. I guess it goes back to "explosive waveforms" in the old JBL advertising.

I am really curious if any of the M2 clone users have compared any of the 2450 family of drivers to the new 2430 driver and what their impressions were of any differences. It seems with these newer drivers they are optimizing them to crossover higher and extending the upper frequency response to well above 20K. The 2450 family seem to have better LF ability and reserve looking at measurements. So they are actually a bit opposite bandwidth wise.

So if surface area is the key to this difference how does it show up in head to head listening differences. I have never heard a 2430 driver so I am at a loss and wonder if there are differences like I hear with the 3" drivers I have been listening to for years.

Rob

[ivica]

Hello

Curious about others experiences with these drivers. I got a big surprise when I started listening to my 476Mg's that I didn't expect. I have 2435's in my 2 other horn/waveguide systems and was a bit shocked by the differences. The 476's are so relaxed and the dynamics are really impressive. I guess it goes back to "explosive waveforms" in the old JBL advertising.

I am really curious if any of the M2 clone users have compared any of the 2450 family of drivers to the new 2430 driver and what their impressions were of any differences. It seems with these newer drivers they are optimizing them to crossover higher and extending the upper frequency response to well above 20K. The 2450 family seem to have better LF ability and reserve looking at measurements. So they are actually a bit opposite bandwidth wise.

So if surface area is the key to this difference how does it show up in head to head listening differences. I have never heard a 2430 driver so I am at a loss and wonder if there are differences like I hear with the 3" drivers I have been listening to for years.

Rob

Hi Rob,

I think that using one of the best (neglecting for the moment stellar 476Be) JBL compression driver 476Mg is privilege for the small number of audio enthusiast.
I have been very happy when I have changed my JBL 2420&2312&2308 with 2441&2311&2308 in my 4333 DIY clone speakers.

Redards
Ivica

[Mr. Widget]

I have been very happy when I have changed my JBL 2420&2312&2308 with 2441&2311&2308 in my 4333 DIY clone speakers.

I have owned LE85s (2420s) and used them in a number of systems over the years. My LE85s had been sent back to JBL and been refurbished by them... You used to be able to do that. I make the distinction as so many times we take if for granted that a working driver is also a properly working driver and through experience, I have discovered that this is far from the truth.

In my early days on this forum I decided to pursue one of popular big kahuna 43XX DIY systems... I built a pair of 4355 clones. For that project I found a pair of 2441s and had them rebuilt by JBL, new throats, diaphragms, alignment and re-magnetizing. I ultimately decided while the 4355 has its charms and all, it wasn't the system for me, but damn if that 4" driver didn't blow me away!

I have since had TAD TD-4001, TAD TD-4003, and JBL 476Be drivers and have been smitten with them all. During this time I also had the 435AL 3" drivers... I am not sure why, but they just don't have the ease and tactile qualities of the big 4" beasts! If you have the budget, buy the best 4" diaphragmed drivers you can get (2" exit or 1.5" exit). You won't be disappointed!



Widget

[speakerdave]

Yeah, "steep waveforms of explosive loudness" (1976 catalogue copy for the 375. I still have my well-worn copy). Love the expression. I suppose in a hard-driven sound reenforcement situation that was it, but in the home I experienced it as the relaxed but superlative dynamics of which you speak when I experimented with 2450's with dusted diaphragms on 2311 horns in my 4345's.

[Mitchco]

Hi Rob, user notnyt over at the AVSForum compared the 2430 with some large format JBL CD's on a 2384 waveguide, summarized:

https://www.avsforum.com/forum/89-sp...l#post42167329

While not an M2 waveguide, it does support your theory. There are measurement details for each of the CD's tested. For the 2430 one can see there are some distortion issues towards its lower limit: https://www.avsforum.com/forum/89-sp...l#post41945689

I had the 3" 2432 on the 2384 and switched to the 4" 2453h-SL and thought it was a major improvement overall - smoother frequency response, better low end response with lower distortion, and the coating makes for reasonable HF extension. I would love to try in on an M2 waveguide.

Kind regards,
Mitch

[srm51555]

To me the JBL large format drivers with new diaphragms are hard to beat for the money. I had the proper D2430K's in my M2 build but didn't care for the result vs my 2440 with be on a three way build.

From GT here:
" The 2430 needs to be used an octave below where it is happy (as in the M2) and has an increased amount of 2nd harmonic distortion between 750 Hz and 1500 Hz as a result. It is not horrible, but it is about 10 dB higher than the 476Mg in that range and up to 20 dB higher than the 476Be over the same octave."

[1audiohack]

Hello All;

There are better amps here amps here and something else will make its way in if only for comparison. At some point everything in the chain becomes suspect. A very quiet amp would be of interest for sure. I will look into the one you suggest Thomas.

The mic’s are the Larson-Davis 2530 on PRM902 pre amps.

Looking at the pages of measurements in the transducer section on our site and everywhere else I could find them, JBL has used just about everyone’s measurement platforms over the years. I didn’t see Audio Precision surprisingly but I only looked at comp drivers. There are several of them that were measured with TEF like the 2435Be and the 2452SL among others. Knowing what is shown in the text in the margins tells me exactly what the measurement set up was so that I can duplicate it exactly including smoothing and data points collected, very helpful.

I ran a brand new 2450SL at 150dB and with “HTR” which is TEF’s harmonic tracking set at .5, 2nd and 3rd and the screen shot looks just like JBL,s. Within 2dB everywhere. I know that’s really pretty basic stuff but if this work doesn’t line up with the majority of their shown data, the future data on linearity could easily be disregarded.

By the way, anyone listened to M-Noise yet? I don’t terribly mind pink noise, I just imagine I am at Niagara Falls and go about the work but M-Noise is like being behind a jet with you ears distorting, even at low levels it’s just obnoxious.

I think I will clean up the rack now that it all works and cycle a much cleaner amp in to see if that is yet visible in the data.

All my best.
Barry.

[1audiohack]

Hi All;

Home for the holidays I am finally making some headway on the PWT and measurement platform front. A while back I bought a LarsonDavis lab grade high SPL mic (pr) and a 200V preamplifier rig. This kit is very nearly flat from 7Hz to 70kHz and below 1% distortion until you exceed 176dB.

I discovered that most quality mic’s stated SPL limit is when they exceed 3% THD and in a PWT you reach 125dB at less than 0.3V. So even if the mic doesn't flatline on it’s voltage supply, the distortion measurements mean nothing when the mic is likely far dirtier than the driver.

My PWT test amp has always been a Techron 5507, functionally a well appointed D75. Usually I am just tickling it when testing comp drivers but today I found it’s limit with a 2450SL, 166dB. I have better amps but I wanted to keep variables to a minimum while getting all the new stuff set up.

The whole reason for all of this is to attempt to actually measure true linearity of these drivers from domestic levels to truly very loud. To see why I / we love some of them and not others.

Getting truly calibrated has been a real pain and but I am gaining confidence in it now.

I still have some work to do like integrate MNoise for a dense frequency test signal and swap in a more powerful amp that’s flat past 40k.

I love time in the lab! Hopefully something of value will come from it.

Barry.

[Mr. Widget]

Very exciting. Keep it coming!


Widget

[pos]

Very exciting indeed!

What about the distortion of the amp itself, for power tests?
An autoformer could possibly solve the issue, or simply an lpad.
Another solution would be to use a very quiet amp for low power tests, such as the new "hi power" headphone amplifiers (THX789 and the like).

What mic are you using?

[1audiohack]

Ha I’m always late!

I built my daughter a pair of 4333A’s from a pair of hacked of JBL cabs that came out of UCLA 100 years ago.

We ran a ton of parts through these. Started with 2235, 2420 on both 2312 and 2307 horns and 2405‘S. 3110A and 3115A crossovers and 3108’s for the 2405’s. I could get any combination to measure fairly well and sound reasonable but I just could not love them.

Yanked all the passives, made block off plates and employed a dbx zonepro. Better but just no life.

I am a hack so, I took the 2307s to the lathe and parted them off where the throat was just under 1.5” in diameter, machined flanges to accept a pair 2451SL’s and fired up the TIG.

Back on the lathe this allowed me to enter the horn after a soft radius at 7.5 degrees from the phase plug exit cheating out a faster entry shorter expo horn that totally looks the part of the old 4333’s and, drum roll, the whole part I didn’t like is gone.

My experience with small format drivers always ends like this.

When I finally got the 4338 horns done, the first thing I put on them was a pair of 2451SL’s and they sound great. Next a pair of M2 D2’s and the magic is gone. Didn’t surprise me at all but I still keep trying to like them.

They D2’s are great tweeters. On top of a pair of 2482’s crossed in about 5.3KHz, magic.

Barry.

[Robh3606]

So now I went and did it! Got a pair of 2453SL to try a driver swap in my basement system. Wow it's one thing to look at pictures but I didn't realize how much smaller they have managed to get the 4" drivers. Not much bigger that the 2430's/435 drivers but with a really significant difference in diaphragm size. It still has a 4 slit phase plug but obviously shorter in length. Would love to see a cross section drawing to compare with a 2450 SL/476. Can't wait to fire them up for some measurements on my PTH1010's. I expect them to be similar to the 476's but we will see.

Rob

[JeffW]

When I finally got the 4338 horns done, the first thing I put on them was a pair of 2451SL’s and they sound great. Next a pair of M2 D2’s and the magic is gone. Didn’t surprise me at all but I still keep trying to like them.

I think it was sebackman in that huge M2 DIY thread (the guy who was making the adapters for the M2 horns to use large format drivers, think it was sebackman). He had D2's and swapped in some 2451's. Liked the 2451's better, seems like he went back and forth, at least with measurements, ended up with the 2451s on there if I remember correctly.

[Robh3606]

Hello Mitchco

I can see why they were well received! I am frankly a bit surprised just how well this driver measures considering how inexpensive it is compared to a 2450! They seem to have done a really good job designing them for lower cost without loosing the performance. That's a 1.5 meter measurement and the top end is much smoother than I expected.

Worked up a passive network compensation on the 2453H-SL on the PTH1010s. As I suspected these 245X drivers are very similar. Was able to just tweak the the network from the PTH1010/476 combo, remove the highpass network and go from there. This will be crossed at 1.5k 24db L/R active crossover when used in my basement system.

Rob

[Mitchco]

Hi Rob, excellent! I totally agree, for the cost, they measure very well and certainly sound good to these ears. My measurements are similar.

Would be interested in your listening impressions once you have everything set up and tuned.

Happy listening!

Kind regards,
Mitch