275nd / S3100 compatibility

[Bernard Wolf]

Hi Earl - thanks for keeping up with this thread ....

Yes, I have been patient and the reason is that my 3100's sound just great as they are and thus there is no burning desire to change them. I also am not really interested in any kind of experimentation.. little too old for that... but am certainly interested in wanting to do an upgrade ala the 275nd.

I am not so sure about outing the titanium diaphragm to replace it with the aquaplased one as I envision possible problems there. As Zilch noted above it might no be as easy as it sounds. Also, I would then end up with a modified 3100 rather than an 'official' MK II. I think I would rather wait untill I get another 275nd complete and then do the swap. I am however,very interested in what you have to say about using the MKii network with the 2426 though.

If I read you correctly I could build the network now, use it with the 2426 and then on that great day when I pick up the second 275nd, I'm in business. Would the MKii network require much modifying to work with the 2426?

Bernard

[Earl K]

I am not so sure about outing the titanium diaphragm to replace it with the aquaplased one as I envision possible problems there. As Zilch noted above it might no be as easy as it sounds. Also, I would then end up with a modified 3100 rather than an 'official' MK II. I think I would rather wait untill I get another 275nd complete and then do the swap. I am however,very interested in what you have to say about using the MKii network with the 2426 though.

- I can understand that / though / you may want to try a fitup of your 275nd diaphragm into a 2426 assembly at some time / just to get a feel for its' "different" sonic texture. .
- I suspect that Zilch has encountered a "QC" issue that's mostly the result of the application ( by hand ? ) of the aquaplas coating. My 2, 2450SL diaphragms are different enough from each other that they really require different amounts of HF compensation from my passive hipasses .
- ie; ( & because of this experience ) I don't consider these JBL-shipped, aquaplas diaphragms to be a "plug & play" remedy to much of anything. Their QC is about the same as buying a carton of stock D8R2425 diaphragms .

If I read you correctly I could build the network now, use it with the 2426 and then on that great day when I pick up the second 275nd, I'm in business. Would the MKii network require much modifying to work with the 2426?

- Sure, I'd recommend that you get a mkII network when you can and use it with your stock 2426 drivers. The voltage drives that Zilch produced ( above ) do indicate this newtork also gives more HF content ( it's a bit more tweeter like ).
I know this advice is in contrast to something I've said previously ( I can't find that post right now ) / but whatever it was that I was thinking at the time / I was wrong . The mkIIs' LCR notchfilters lineup well enough with some undulations in my 2344/2426 workup that I can see that they are more driver/horn specific than diaphragm specific .

- Here's a .gif that represents a blast from the past ( when the 275nd was available as a part ).

[Bernard Wolf]

$605.00..... Ouch ! ... Guess the $200.00 or whatever it was I paid off of Ebay was a steal considering it looks to be 'brand new'. OK then, as soon as I can I will be off to Solen here in Montreal and see what they will charge me to build the networks. As my stock x'overs are external swapping them out will be a piece of cake. So, I guess what you are saying is that they will not require any mods to work with the 2426... very interesting.

If I manage to get everything up and running by the time you show up here in Montreal I would be more than happy to have you come and have a listen. Even if not, by all means drop by and hear the 3100 as is. Have you ever heard them? I'm very curious to hear what other JBLer's with experience have to say about the 3100. I have never really heard any other JBL other than mine and so have no real idea as to were they stack up in comparison.

Thanks - Bernard

[4313B]

- Here's a .gif that represents a blast from the past ( when the 275nd was available as a part ).

Yeah, I'm not real sure why they were discontinued. They were nice. I believe this one was the last one JBL had available and it went to France to another forum member. There are a few others at JBL, two in reference systems and one sitting on the shelf with all the other compression drivers they've ever made. I asked if I could shoot a picture of those shelves and the PWT. The answer was no.

[Earl K]

Hi Bernard,

Thanks for the invite !

$605.00..... Ouch ! ... Guess the $200.00 or whatever it was I paid off of Ebay was a steal considering it looks to be 'brand new'.

- Yeh, I posted that pic for reference.

OK then, as soon as I can I will be off to Solen here in Montreal and see what they will charge me to build the networks. As my stock x'overs are external swapping them out will be a piece of cake.

- I think we'll all be interested at what Solens' pricing will be .

So, I guess what you are saying is that they will not require any mods to work with the 2426... very interesting.

Sorry : Actually, that's not really the case ( though a new plug & play may be close enough for R & R ).

Still :
- The LCR notches will still need to be tweaked to properly zone in on the peaks produced by your specific 2426 drivers. Additionally, because the DCR values of the coils in the mkII are unknown, the notches are likely going to end up deeper ( from a custom Solen build ) than they ought to be ( unless you transport a speaker over to Solen so that they measure the results as they go along ).
- Also, my own preference would be to redesign the padding network to simplify it, to make it conform with what I perceive to be , more typical Northridge network design practices ( I'm a liitle uncertain if this network is GTs' handiwork or someone elses / it looks to be someone elses through my wandering eyes ).
- Also, this mkII network may benifit from having a LCR impedance correction network added to it ( as is found in the original N3100 ). This means someone needs to build the mkII network / measure it's overall impedance with drivers in place / then decide if the LCR impedance correction is applicable .

[Zilch]

There is the remote chance that one or more MKII networks are available off the shelf somewhere within the JBL consumer parts system.

Part numbers 333938-001 (HF) and -002 (LF).

I've had some luck in the past with this sort of pursuit. The hard part is getting someone knowledgeable of what's where on the phone....

From the depth of the notches shown in my simulation, knowing the DCR of the inductors is crucial to getting it right, and even then, they will likely have to be custom optimized for the different driver/diaphragm combinations.

Agreeing with Earl, it's unlikely Solen will be able to do it without samples, but I'd be interested in knowing what they estimate as the cost. Biased and bypassed, that network is at the high end of construction complexity in my experience....

[Zilch]

Indeed.

And other stuff, too....

[Earl K]

Orientation ; Zero Degrees to what ( horn edge & middle of slot ) ?

Also, what network is being used ?

[Zilch]

Hi, Earl.

0° is perpendicular to the horn face, and alignment is to the empirically determined (from impulse delay) acoustic center, which, best I can tell, is at the slot, NOT the driver voice coil or diaphragm.

Driver is offset 30° to the outside rear (left in the pic) by the throat.

Mic's at 30° in the pic, i.e., in line with the driver axis, orange curve, max SPL.

Filter is 18 dB/octave 1200 Hz FFBREQ in 5235.

Driver is BMS 4552nd-8.

Measuring distance is 44".

Unless I'm totally FUBAR here, the horn is amazing.

See CLIO Clinic for polar response measurement methodology:

http://audioheritage.org/vbulletin/s...442#post112442

Sitting at the apex of an equilateral triangle formed with a speaker pair, you'd be hearing the orange curve (30&#176, somewhat further back, the green (15&#176.

Then, as you move to one side, the nearer speaker goes toward the red (lower SPL) while the farther one goes toward orange (highest SPL), compensating for the change in distance and locking the image in place.

The effect remains operative even closer than the equilateral case due to the differential rates of SPL change with geometry.

[Earl K]

Hi Zilch,

Thanks for the visuals / with explanation .

They certainly do underscore everything everyone has ever said about these horns and their stable imaging .

[Zilch]

Yup.

They were my "Final Iteration" over in Q&D.

Looks like CLIO has answered the rhetorical question there:

http://audioheritage.org/vbulletin/s...2145#post92145

[Mr. Widget]

Unless I'm totally FUBAR here, the horn is amazing.

What makes you say that? ...not the FUBAR bit, but why do you come to the conclusion that this is an amazing horn? I suppose I'm asking, what are your criterion for an "amazing" horn?


Widget

[Zilch]

Why do you come to the conclusion that this is an amazing horn? I suppose I'm asking, what are your criterion for an "amazing" horn?

It's amazing in that it so effectively reverses the normal progressive decay of SPL at the requisite angles without introducing major anomalies in the FR.

There are some quirks up at 15 kHz, but those are minor in comparison to what I've found measuring other horns/waveguides. The TOTAL variability here is controlled within +/- ~2.5 dB, and the response at each different angle retains its integrity throughout most of the range.

This level of precision FR and SPL control would seem to contribute significantly to the successful image stabilization. The power response appears extraordinarily well controlled. They work.

Since I'm still set up here, I'll run 2344A for comparison. I trust we can most all agree upon that horn as a "standard"....

[Mr. Widget]

Since I'm still set up here, I'll run 2344A for comparison....

I don't see the point in that... JBL has published quite a thorough exploration of their axial performance. To me this exercise reminds me of those Stereo Review "Bench Tests" of receivers back in the '70s where this one had more zeros than that... none of them sounded as good as an old tube Mac even though the Mac's measured performance was significantly inferior.

For me what makes an "amazing" horn is in the listening. When I listened to those horns at your place, I did not think of them as amazingly good. What they do is very interesting.... I certainly agree that they are absolutely intriguing. I suppose if the goal was simply to provide a very good polar plot, they are unusually good at that, however I'd guess from having listened to them at your place they must make a mess of the signal's phase since they didn't create a stereophonic image that was really convincing. They certainly can't compete with any of the better dome and cone based systems. Personally I thought they sounded quite odd actually. Rather than focusing on a slight bump in the response of this or that horn perhaps you should set up some double blind listening tests... I believe that our onboard monitoring equipment is ultimately more discriminating than what we can generate with a mic comparing this curve or that...

Sorry... I have kind of gone off topic here again, it was just that I didn't see those horns as "amazing"... assuming amazing means stellar performers. I am sure there are plenty of folks who are happy with them, but I'd rank them as someone's personal fav as opposed to a universal success story.


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[Bernard Wolf]

Well, I do have to put my 2 cents worth in.. unfortunaltely, since I do not think that either of you have heard a factory built setup I don't know how you can say anything difinitive about the 3100/2600 finished product.. The reason I say this is having owned Quad 57's, which by most peoples definition are much better than average at stereophonic imaging, I can difinitively say that the S/3100 throws are very, very convincing soundstage. Every bit as good as the 57's and in most ways better.
Come and listen any time.

Bernard