2450 Dia

[paragon]

Does a 2450 Titan Diaphragm also fit in a 2441 ??

Eckhard

[Earl K]

Good Question;

I've put 2445 diaphragms into 2440 and 2441 magnets with success. I've also put a 2450SL diaphragm into those same drivers with success - but then, the 2450SL diaphragm is just a 2445 diaphragm with aquaplas on it.

"With Success ", I mean , I end up getting a response curve that is acceptable for that type of driver ( my tolerance is ± 3 db ).

I've never had a 2446 diaphragm in a 2441 magnet .

<> EarlK

[Guido]

Hey Eckhard!

Do you have small and silent K2 thoughts?

;)

[scott fitlin]

Originally posted by paragon
Does a 2450 Titan Diaphragm also fit in a 2441 ??

Eckhard It can be done, this was what I was considering when we thought that JBL was going to discontinue aluminum diaphragms!

It will work, but will not sound like the aluminum diaphragm.

[Earl K]

Hi Scott,

It will work,

What sort of response curve did you get ?


<. EarlK:)

[scott fitlin]

I never went ahead and actually did it, but an engineer had recommended this to me, and I spoke to JBL, and they said it can be done, this was back in `95, and word was they were going to stop making aluminum diaphragms! But they didnt, so neither did I.

What I was told, though, is that the lower midrange end of the spectrum would become more prominent with the 2450 phragm!

:)

[Earl K]

What I was told, though, is that the lower midrange end of the spectrum would become more prominent with the 2450 phragm!

Interesting :)

I might be testing out this scenario sometime this month - as part of a fact-finding mission to see why one of my 2450SL diaphragms won't properly "fitup" into any of my 2440/1 magnet structures. ( I suspect Canada gets shipped a lot of "seconds" ).

<> EarlK:D

[Guido]

According to JBL spec sheets the 2446 and 2450 drivers use the same dia, have the same phase plug and have identical flux and BL.

Why the heck the response is so different?

2446 response according to JBL spec sheet:

[Guido]

2450 response according to spec sheet:

[Guido]

JBL Diaphragm D8R2450 - for 2446H, 2447H, 2450H, 2451H
JBL Diaphragm D16R2450 - for 2446J, 2447J, 2450J, 2451J

[Guido]

JBL Diaphragm D8R2450 - for 2446H, 2447H, 2450H, 2451H
JBL Diaphragm D16R2450 - for 2446J, 2447J, 2450J, 2451J

[Guido]

D8R2450SL and D162450SL should be same except aquaplas coating.

D8R475ND (K2) should be similar without ribs and with aquaplas coating.

Hope this is it!

[subwoof]

"D8R2450SL and D162450SL should be same except aquaplas coating. "

wrong. one is 8 ohm, the other is 16. both are coated as is the ribbed version D8R2450SL-A ( very late model DMS-1's used these )

the privy:

D8R2450SL

D ( diaphram ) 8 ( impedance ) R ( replacement ) 2450SL ( model )

substitute D with a C and you have the cone kit numbers ( cone )

sub

[Guido]

Clear subwoof. My fault!

I meant D8R2450SL and D162450SL are the same than D8R2450 and D16R2450 except the coating.

Of course one is 8 and one is 16 Ohm!

[Niklas Nord]

I broke the two diaphragms in my K2 s9500,
they look like this:

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=3615&stc=1


Do you think they should be replaced with the same diaphragms, or
should it be the original coated ones?

I guess I have D8R2450 in my K2 now, and what´s the diaphragm number
for the original K2 475nd driver?

Is the D8R2450 just a never kind of diaphragm? So I should be using this never one,
or is it just the 475 original that it should be?

I thought there maybe would be better strenght and upper HF detail in the D8R2450
than the original...

[Maron Horonzakz]

Boy now Im really confused!!!! I thought the 2450SL was smooth Plus the aquaplaz coating. Like the 475......We need photos of all the large diaphrams and properly labled to stop this confusion. I thought JBl was going to list this for us in due time. Well its now DUE.:banghead:

[4313B]

"I thought JBl was going to list this for us in due time."

We've been working on other things. The diaphragms have taken a back seat for now.

Niklas, use the original diaphragms for the 475Nd's (D8R475ND). The S9500 is a pretty tight system. I would recommend keeping it as intended.

[Maron Horonzakz]

Do I have to throw a snit fit & pee all over the place? I never get what I want:biting: "sniff"

[Earl K]

Maron,

Boy now Im really confused!!!! I thought the 2450SL was smooth Plus the aquaplaz coating.

- It is .
- I have (2) 2450SL that are smooth with an aquaplas coating . I believe JBL just takes a stock 2445 ( 8 ohm Ti ) diaphragm and adds the aquaplas. That "works" because they are essentially taking their most "under-damped" R&R 4" diaphragm and adding a bit of damping to it ( to make it more HiFi acceptable ) Understand, this is just my own opinion/editorial . :D BTW, IME, JBLs' 8 ohm diaphragms are more underdamped than their 16 ohm varieties .

- SubWoof is the expert on all the combinations & permutations of these things . :)

[Maron Horonzakz]

Earl K......Thank you I feel better now.

[subwoof]

Greetings o seekers of the grail....

I will post a group photo of the JBL large format diaphrams soon. I will be laid up while I recover from hernia surgery ( DAMN those 4345's ) next week and can dig thru the "wall of shame" in the shop.

Might not have a D8R2450SL-a so I might have to spraypaint a 2450 for the group shot ( assuming I have 2 )

I will include the 3" variant and also some examples of altec and gauss if they are still there.

And for the DIY guys, a group shot of the small format thread-on ( 2412,16,17,18 ) types.
subwoof

[spkrman57]

I have always been curious of the different diaphrams used in compression drivers.
Ron

[Guido]

Come on!

Please post the picks!:bouncy:

[paragon]

Thank you all four your answers !!

Eckhard :)

[paragon]

Just hear "Smooth Operator" from Shade.:D
Face to face....
He`s heart is cold....

[paragon]

Its like a Cannonball !
What´s it ???

[4313B]

What!?

I'm confused...

[stevem]

Has anyone listened to ribbed vs. smooth diaphragms? How do they sound different? Do the ribs have an effect at low, as well as high spls?



I am using 2450SL drivers which (I believe) have smooth, aquaplas coated diaphragms. I think a later version, the 2450SL-A, added the ribs. Does anyone know if this is worth changing diaphragms for? Thanks.

[speakerdave]

I don't know the answer to your question, but I would like to add to the confusion by saying that I just received shipment on a (sealed box) NOS D16R2451SL diaphragm and it is smooth and coated. I plan to fit it into one of my 2447's and give a listen.

David

[subwoof]

I mentioned to the seller that the diaphram didn't match the box. He elected not to edit his listing. What you have is a D16R2450SL. The 16 ohm version is/was used in the HLA touring products and I suspect also as one of the japanese variants.

It would make an excellent upgrade for the 2440 assuming the purists aren't offended. I used them in floor wedge monitors and it tamed them quite well.

:cheers:

sub

[speakerdave]

Would appreciate if someone who has 4" aquaplased smooth titanium diaphragms would check the DCR. Mine reads 7.7 ohms, which seems high for a nominal 8 ohm voice coil and low for a 16. I'm wondering if it is another case like the 8 and 16 ohm 2405's actually being 10 ohms.

David

[Jakob]

My 2445 dias have a dcr of 8 Ohms, but I don't know for sure if they are H's or J's.

regards: Jakob

[subwoof]

what is the color of paint on the + terminal?? red=16, green=8

sub

[Alex Lancaster]

:) I have some NIB D8R2450´s that measure 4 ohms, they are ribbed, have a green dot on the terminal, and a small, about 4mm aluminum dot at the top of the dome, they are not SL´s.

Hope it helps.

[Earl K]

Would appreciate if someone who has 4" aquaplased smooth titanium diaphragms would check the DCR. Mine reads 7.7 ohms, which seems high for a nominal 8 ohm voice coil and low for a 16.

- My 2 "green-dot" 2450SL diaphragms each measure @ 4 ohms DCR / just like my single 2445H does.
- This is how it should be for both these diaphragm models .

- A healthy 2445j diaphragm ( reported to be the basis for the aquaplased D16R2450SL ) is supposed to measure in the range of 6.4 to 7.8 ohms DCR ( according to JBL service literature ).
- So, your diaphragm is healthy and normal from the info given .
- They must be coded "red-dot" . Yes / No ?

:)

[speakerdave]

Thank you, my friends. Mine is red dot and must be a 16 ohm diaphragm.

David

[johnaec]

I have a new in box D16R2450, (not SL), but I'll check the DCR later this afternoon.

John

[Zilch]

The DCR of John's new D16R2450 is 7.7 Ohms.

I'm playing it mounted in his 2446J driver on 2380A horn.

His other (older, original diaphragm) 2446J here reads 8.2 Ohms.

I'd like to try these with Aquaplas coated diaphragms.

2450SL is not available 16 Ohms; no D16R2450SL listed.

Interestingly, D8R2450SL is the same price as D8R2450 ($174 list).

D16R2451SL for 2451SLJ is available for $20 more ($194 list).

Is that what I want? The only coated 16-Ohm option?

Speakerdave mentioned it above....

[speakerdave]

D16R2451SL for 2451SLJ is available for $20 more ($194 list).

Is that what I want? The only coated 16-Ohm option?

Speakerdave mentioned it above....

My D16R2451SL's are coated, smooth.

[Zilch]

Thanks, Dave!

Did you ever install in your 2447J's?

FR curve the same? (I got MAJOR changes installing D8R275nd in 2426H.)

And does it confer the desired "smoothness" to the sound?

[speakerdave]

Not going in my 2447's anymore. Going into the 2450's. I'm hoping they are going to have a response similar to the 475nd's in the M9500. Now, if I could only get hold of a pair of those H9500's. Hmmmm . . . . :tree:

[johnaec]

no D16R2450SL listed.This one just ended on eBay - too rich for me: http://cgi.ebay.com/JBL-D16R2450SL-Replacement-Diaphragms-for-1-5-2-Drvr_W0QQitemZ7391383044QQcategoryZ47094QQrdZ1QQcm dZViewItem

John

[Zilch]

Not going in my 2447's anymore. Going into the 2450's. I'm hoping they are going to have a response similar to the 475nd's in the M9500. Now, if I could only get hold of a pair of those H9500's.I THINK that may be a game I wanna play.

Keep us posted here, please. :thmbsup:

[JBL Dog]

This one just ended on eBay - too rich for me: http://cgi.ebay.com/JBL-D16R2450SL-Replacement-Diaphragms-for-1-5-2-Drvr_W0QQitemZ7391383044QQcategoryZ47094QQrdZ1QQcm dZViewItem

John

I have a pair of these if anyone is interested. I can't claim NOS, but they are in very fine shape. DCR measures 7.8 and 8.1. I came across these a while back. They were packaged in open D8R475ND boxes. However, the part number is 61435. That matches the phragm in the auction John has listed.

$200 delivered to any local in the lower 48. I have several pictures I will post if I can ever figure out this new system. Send a PM if interested.

[Zilch]

O.K., dibs on the doggie's dias.... ;)

[JBL Dog]

O.K., dibs on the doggie's dias.... ;)

Zilch is the proud new owner of the dias. Here are those pics I was trying to post earlier:

Thanks!

[Ian Mackenzie]

Hmm,

Do you like them better than plain Ti?

Ian

[speakerdave]

Do you like them better than plain Ti?

Me? Dunno yet. I'm just trying to assemble the pieces for some M9500 wannabes.

David

[Zilch]

Do you like them better than plain Ti?It's clear the prior owner of Doggie's diaphragms liked 475's better.... :p

[speakerdave]

It's clear the prior owner of Doggie's diaphragms liked 475's better
And what were the 475's like? I think they are the same.

David

[Guido]

Wouldn't one need a 8 Ohm (DCR ~4 Ohm) Dia to copy the M9500?

[stevem]

What's the difference between the 2451SL diaphragm, and the 2450SL-A diaphragm? Is the former a 16 ohm, and the latter an 8 ohm?

[Zilch]

And what were the 475's like? I think they are the same.I dunno. Maybe they just wanted 8 Ohms.... ;)

In any case, here's the relevant section of the current parts list. Looks like "SL" in 8 Ohms is 2450, and 16 Ohms is 2451.

475 would come from Consumer, presumably....

[stevem]

Note that the 2450SL diaphragm is smooth, not ribbed. As I understand it, the 2450SL-A (not listed) is ribbed.

[speakerdave]

Wouldn't one need a 8 Ohm (DCR ~4 Ohm) Dia to copy the M9500?
I don't know. I looked and didn't find where it said the voice coil in the treble driver of the M9500 was 8 ohms. I believe the input of the system is eight ohms, but there are two woofers and the system is bi-wireable. I realized early on that I probably was not going to be able to use the stock passive crossover because I don't really expect the stock horn to be available. So, if I use a passive crossover it will have to be a custom one anyway. But I plan to use active crossovers because Mr G.T. says that the 1400nd "does not like inductors." I think he means especially because most bass driver circuits are better without an inductor in there. I assume that the 1400nd doesn't like them especially because of the complex voice coil arrangement (there is a braking coil) in the 1400nd. Besides I want to use solid state for the bass and tubes for the treble. I chose 16 ohm coils because with a 16 ohm tap on the output transformer there is no power loss and in the days of tube amps treble drivers were usually 16 ohms nominally. Anyway, I don't expect it will really make any difference.

David

[Zilch]

Without the engineering specs, it's difficult to know what's what.

I'm recalling that my 275nd's are not only coated, but also the substrate titanium diaphragm is thinner than "standard."

The coating is also substantially thicker than what I would call a "dusting." I posted a pic of them in the forum here:

http://audioheritage.org/vbulletin/showpost.php?p=78330&postcount=675

[Zilch]

1) Stock 2450H, top, ribbed. Performing per spec, apparently: http://audioheritage.org/vbulletin/showpost.php?p=31408&postcount=9

2) JBL Dog's D16R2450SL diaphragm installed, smooth, aquaplassed, bottom.

Both on the same 2380A horn, no compensation or EQ, just 47uF in series for protection.

Indeed, more natural sounding vocals, strings, horns, and pianos, 3-Way.

Johnaec's coming by for a listen tomorrow, so second opinion pending.

Sample of two, folks, so do not generalize from these preliminary results.

[Looks like it'll "Push," (10 dB) tho.... :p ]

[Earl K]

Zilch

- Whatever happened to your fit-up of the D8R275nd diaphragms into the 2426 drivers ?

- I seem to recall that particular experiment didn't turn out very well . Not as well as what you've just posted above.

- Do you feel the problem was perhaps an install problem ? / or / Did you conclude they ( the old & new technology ) just weren't meant to work together ?

- ( FWIW ; the 2410/le175 magnetic assembly has a flux level within the gap that is closer to the original 275nd spec. )
- I've heard through the grapevine that "over-gaussing" a gap ( when driving a lighter weight diaphragm ) can lead to "non intuitive results in FR" . These results include a significant spike in the pistonic response area ( ie midrange ) vs the HF & UHF surround generated resonances . At least , so goes the rumour .

:)

[Zilch]

Zilch

- Whatever happened to your fit-up of the D8R275nd diaphragms into the 2426 drivers ?

- ( FWIW ; the 2410/le175 magnetic assembly has a flux level within the gap that is closer to the original 275nd spec. )

- I've heard through the grapevine that "over-gaussing" a gap ( when driving a lighter weight diaphragm ) can lead to "non intuitive results in FR" . These results include a significant spike in the pistonic response area ( ie midrange ) vs the HF & UHF surround generated resonances . At least , so goes the rumour . First try of 275nd in 2426H is here:

http://audioheritage.org/vbulletin/showthread.php?t=9746&page=16

[I'll try to post the Q&D index this weekend. :) ]

They require different compensation and EQ than the stock 2426, from my results. Using AutoEQ, I played them on H3100 horns with similarly pleasing results, and plan to study them further. I'll likely end up tweaking some crossovers to use them, but in what system, I don't yet know.

I'll mount them on some 2370A's here and post results for comparision to 2450, above. Actually, I have some 2427 throat adapters that'll mount to 2380A. Maybe that, instead, for a more direct comparison.... :thmbsup:

[John's reclaiming his 2380A's here tomorrow, so I gotta do that today.]

Re: LE175, they're so damn valuable with the wax seals intact, I'd have to buy some thrashed ones to try. Anybody have some for "Science?"

[OR, a pair of nasty ol' 275nd motors? :p]

Edit: O.K., 275nd diaphragms in 2426H's on 2380A horn:

1) 2426H, stock diaphragm

2) 2426H, 275nd #1

3) 2426H, 275nd #2

4) Test setup, 2427 throat

5) 2450 three-way in #56, above.

[Earl K]

Hi Zilch

- The fitup problem with the D8R275nd put into a 2426, was first mentioned in this single post . (http://audioheritage.org/vbulletin/showpost.php?p=78330&postcount=226) It shows a bit of a "sink-hole" at 5K .

- My memory had that 5K dip in FR confused with the 7.5K peak that you got when you installed a D8R2421 diaphragm into a 2426 core, shown here in this post . (http://audioheritage.org/vbulletin/showpost.php?p=80039&postcount=295)

:)

[Zilch]

Admittedly, I'm not the most competent of diaphragm swappers, and we've discussed alignment issues in other threads here recently.

SO, I'd very much like to see others' FR results with "SL" diaphragms in comparison to uncoated here.

IIRC, YOU've got some, Earl, no? ;)

[Earl K]

SO, I'd very much like to see others' FR results with "SL" diaphragms in comparison to uncoated here.

IIRC, YOU've got some, Earl, no?

- Yes, I have a D8R2450SL installed into a 2440 ( remagged ) driver ( lots of gauss ;) ) .
- I could post a pic of a RTA shot from a Behringer EQ, ( unfortunately, no CLIO here and I thought these rough type of RTA shots had been banished :D ) .
- The problem is , I don't have any large format cd horns to mate it up to ( just some older exponentials ). So , it'll be apples & oranges between your results and mine. Do you want to see a 2311/2308 combo ?

:p

[Zilch]

:hmm:

If you've got a stock diaphragm 2440 for comparision, that'd be worthwhile.

OR, borrow a 2380(A) from a forum pal up there? :D

Actually, lots of members have stock on 2311/2308 for comparison.

So, post it, YES!

Do you find the same, i.e., smoother, more "natural" sounding?

[Earl K]

Do you find the same, i.e., more "natural" sounding?

- I haven't had any intimate listening sessions with that setup for going on 2 years this summer / but / yes ( from memory ) the aquaplas tames most of the "zings & zangs" that one gets from these 4", 8 ohm titanium diaphragms. Even with the aquaplas the 8 ohm titanium diaphragm has more "splash" ( 6K & up ) when compared to an Altec 288-8K ( as a for instance ) .

- "Splash" can be "fresh" , "exciting" , and even "open-sounding" ( at its' best ) / though this "trait" easily gets out of hand and leads me toward ear-fatigue. I never, ever get fatigued from my 288(s) .

- FWIW, I find the stock 4", titanium diaphragms to be just about unlistenable ( at home on my typically small horns ). The same holds true for all the 3" european diaphragms that I've tried here . The D8R2450SL was "listenable", if that helps . I liked it more than a D8R2441 diaphragm in a 2441 or 2440 magnet .


:)

EDIT: I'll post something this evening .

[Earl K]

EDIT: I'll post something this evening .

No,,,,That's not going to happen. I'll have to revise that timeline into tomorrow sometime ( I got sidetracked working out a tank circuit for a 2012H ) .

:o:

[Zilch]

BTW, IME, JBLs' 8 ohm diaphragms are more underdamped than their 16 ohm varieties....That'd make these 16-Ohm ones "just right," then. ;)

I gave 'em (2450's w/D16R2450SL) JBL standard 2380 CD compensation (1.2 kHz FFBREQ in 5235). That confers too much VHF, obviously, but you jus' KNOW where I'm headed with these, now.... :p

[Zilch]

"Next-generation" HF driver: 2452H-SL titanium damped 4" diaphragm 1.5" exit:

http://www.jblpro.com/installedsound/vpseries/specsheets/VP7215_95.pdf

PT-H95HF waveguide....

[JBL Dog]

That'd make these 16-Ohm ones "just right," then. ;)

I gave 'em (2450's w/D16R2450SL) JBL standard 2380 CD compensation (1.2 kHz FFBREQ in 5235). That confers too much VHF, obviously, but you jus' KNOW where I'm headed with these, now.... :p

So, are you happy with the Dogs' dias?

[johnaec]

( I got sidetracked working out a tank circuit for a 2012H ) . :o:What's a "tank circuit"? (wondered John, eyeing his two 2012H's still NIB...:) ).

Also, I stopped by Zilch's today and had a listen to the 2450's with aquaplas'd diaphragms playing through 2380A's. Even just 2-way, I found them highly listenable. Unfortunately, there wasn't a setup for comparing them against the standard titanium diaphragms, but they definitely sounded quite good to me - vocals, piano, cymbols - I really didn't detect what I would call any harshness at all. 'Also listened to the same setup crossed over into 3-ways, though I'd have to do some long comparisons to determine which HF matched up best. But overall, I was impressed with how well those 4" diaphragms with 2" throat and big flat-front bi-radials sounded. I'd still like to hear the 2380's compared with 2397's sometime...

John

[Zilch]

So, are you happy with the Dogs' dias?We're certainly having fun "investigatin'" them. :p

"SL" isn't mainstream; not much information available. But if JBL's latest offerings, both consumer and pro, are indicative, it's a worthy pursuit.... :thmbsup:

[stevem]

"Next-generation" HF driver: 2452H-SL titanium damped 4" diaphragm 1.5" exit:

http://www.jblpro.com/installedsound/vpseries/specsheets/VP7215_95.pdf

PT-H95HF waveguide....

Is there any info on this driver? How is it different from a 2451H or a 2450SL?

[Earl K]

What's a "tank circuit"? (wondered John, eyeing his two 2012H's still NIB... ).

Okay ; :offtopic:

- A "tank circuit" is a colloquial name for a LCR-type "resonance trap" circuit using "paralleled-components" and usually used inline , ie; inserted in series within the audio circuit ). The "Everest" has one in the woofers' passive circuit while the L220/222 has one in the passives' midrange circuit . I think the resonant frequencies are somewhere around lower 300(s) and about 1450 hz respectively .

- In my particular case. A 25uF Solen cap was paralleled to a partially unwound 1.6 mH coil and then these were paralleled to a 5 ohm resistor . The whole mess was inserted in series on the 2012H . The calculated resonance value for 25uF with 1.6 mH = 796 hz. My measured resonance point is @ 820 hz which just happens to work out to be a resonance point for 1.5 mH & 25 uF ( actually 821 hz is the calculated point for those values ).

- My inline filter has a very broad based effect, showing measurable attenuation between lower than 400 hz & up to 2000 hz / so it has pretty low Q ( though I haven't done any calculations to support this observation ) .
- This filter does a very nice job of flattening the response of this 10" for intended usage in a small ported enclosure ( @ .6 cu' tuned to around 110 hz ).
-I imagine that the usable db rating shifts to around the middle 90's ( maybe 94/95 db , though I have yet to measure this ).
- That figure happens to be in my target range since I want to eventually ( think extreme future tense ) parallel this midbass with a ME150h woofer to create a higher sensitivity, asymmetrical MTM . Therefore I need to jump through some filter hoops like this, even when the whole sheebang is meant to be crossed over electronically .


:)



EDIT: I'll post something this evening (Sat.).
- No,,,,That's not going to happen. I'll have to revise that timeline into tomorrow sometime ( I got sidetracked working out a tank circuit for a 2012H ) .
- No,,, Not today either ( Sunday ) . Hopefully tomorrow ( Monday )

[Zilch]

Is there any info on this driver [2452H-SL]? How is it different form a 2451H or a 2450SL?No clue. I just found it yesterday on a tip from Johnaec regarding new offerings at JBL Pro.

It seems from the product response curves that they're not pushing the UHF terribly hard, but the VHF appears to carry higher than I have measured with 2446J, for example.

That PT-H95HF waveguide is the deepest (by substantial margin) of the PT family I've evaluated here, and probably the best sounding. With previous product offerings using it, JBL cautions that, for optimum performance, delay should be incorporated on accompanying driver(s) to compensate.

When I first saw the 90&#176; x 50&#176; spec, I was hoping the PT-F95HF would appear. Not yet, alas....

Perhaps Giskard has (or can obtain for us) some info on the new 2452H-SL large-format driver?

[stevem]

No clue. I just found it yesterday on a tip from Johnaec regarding new offerings at JBL Pro.

Check this out:

http://www.jblproservice.com/pdf/Discrete%20Sales%20Models/2452HJ.pdf

The SL version probably has an Aquaplas coating.

[speakerdave]

BTW, IME, JBLs' 8 ohm diaphragms are more underdamped than their 16 ohm varieties .
Is that because of all the mattresses, old tires and catcher's mitts they hafta put in the 16 ohmers to slow down the electrons?

[Earl K]

Is that because of all the mattresses, old tires and catcher's mitts they hafta put in the 16 ohmers to slow down the electrons?

- Good One Dave !

- But no , I'd say it's a matter of making a comparison between the BL figures when looking at the so called 8 ohm versions vs the nominal 16 ohm types . Just about always, the 8 ohm diaphragms have more electromotive force after a per unit normalization . It stands to reason that these higher BL types will also have more modal breakup issues and thus measure slightly different .

- In the SR world up here in central Canada , it's long been a held opinion among a certain older crowd ( defined as over 55 yr , as of 2006 ) that JBLs' 16 ohm type diaphragms sounded "smoother" / across the board for the different models ( FWIW ) . Why ? Think of the BL differences that Giskard ( & others ) like to chew on when someone creates a hybrid ( franken -) woofer using 2235H cone kits in an overmagged core assembly.
- That same focus can be shifted onto diaphragms when they are put into none standard motors ( especially when the motor has a different gauss level , ie giving a non-standard BL coefficient ) .
- A lot of these issues can be explained as what's the best performing balance of FR vs "sound" ( made between a diaphragms mass and the BL that indicates the strength of the motive forces ).

:)

[Zilch]

Check this out:

http://www.jblproservice.com/pdf/Discrete%20Sales%20Models/2452HJ.pdf

The SL version probably has an Aquaplas coating.And a smaller 3.25" mounting bolt circle like the 2450SL to mate with PT waveguides?

A throatless "Optimized Aperture" driver, looks like....

[stevem]

And a smaller 3.25" mounting bolt circle like the 2450SL to mate with PT waveguides?

A throatless "Optimized Aperture" driver, looks like....

According to the spec sheet, the 2452H has a 4 1/2" bolt circle like the 2451. Does this mean it won't work with the PT waveguides? You think the SL version has the smaller bolt circle?

[Zilch]

Yup.

http://www.jblproservice.com/pdf/Discrete%20Sales%20Models/2450SL.pdf

I'm not real good at guessin' this stuff, tho.... :p

[Zilch]

The "List" as I see it

Engineering design specs for:

2450
2450SL
2451
2451SL
2452
2452SL

Also, what is 2450SL-A diraphragm. Ribbed, with Aquaplas?

D16R2450SL is not on the price list. Is D16R2451SL the same?

Is the 475 diaphragm the same as either of the available Pro "SL" diaphragms?

[stevem]

Any info on these yet?

[Zilch]

From the pic he posted today, Giskard may still be at JBL, looks like.... :)

[Zilch]

Ah-HEM!!

http://www.jblpro.com/installedsound/support/index.html

2452H-SL, PT-F1010HF, NL200t3 biased and bypassed, L88 plugged.

Red = HF only, windowed.

Org = Full system, unwindowed.

[Who's J.R.? :dont-know]

[Zilch]

Per request, impedance, phase, and response plots for 2 units 2452H-SL, on PT-H95HF waveguides. Frequency response is shown at both 10 and 5 dB/division. Raw FR plots unsmoothed, filtered ones 1/6 octave.

I'm not seeing any breakup mode here, unless it's at 10 kHz; I doubt the waveguides are masking it.

The two units are not perfectly matched. Don't know if I'm going to do anything about that, tho, at this point....

Sorry 'bout the wide impedance/phase plots. I want to show max resolution for TimG's analysis.

VP7215/95 frequency response, bottom. Same driver and horn, filter/EQ unknown.

Looks like #2 (blue) is the "good" one from that; I doubt they EQ above 10 kHz.

[Measure your drivers, folks, even (especially) the $1315 ones.... :yes: ]

[TimG]

That response graph is very impressive. That is the best response curve I have seen from any JBL compression driver yet. I don't see any break up in the response curve before about 19kHz. I found the price, at $1315 it is less expensive than the list price for the 2435HPL. Maybe some B-stock will turn up some day that I could afford. If you have 2 of those and 4 2235H's, you really need to throw them together with an Everest style crossover and let us know how they sound with your 2452 horns.

Here is an example of a different large format compression driver with obvious breakup in both the frequency response and impedance sweep curves. This example is the B&C DE610. I would not try to use a driver like this above 10kHz.

Here is the frequency response and the impedance curve. Notice the peaks in response and the corresponding peaks in the Imp curve where part of the diaphragm is no longer behaving like a piston.

[Zilch]

One 2235H will have to do until Mr. Widget makes me a


V--E--R--Y- -W--I--D--E


horn.... :D


[Not bad on PT Waveguides, actually, and the compensation is, well, uhmm, "straightforward...." ;) ]

[Zilch]

Horn flange is drilled to accept this bolt pattern, same as 243x drivers.

1) Impedance and phase.

2) Frequency Response of driver alone, with compensation, and full range with 2235H in 4507, two ports closed.

3) Comparison with 2435HPL. 2452H-SL requires 10 dB less "push" at 20 kHz; no more than at 10 kHz, apparently.

4) Published FR of 2451 on 2352. "-SL" version upublished, and I don't have one. :(

[Zilch]

O.K., so how do they sound?

What JBL says: "Crystal-clear."

Also, what Earl suggests: "Splashy - fresh, exciting, open-sounding."

Who's gotta pair 2451SLs they can send me to test for comparison?

[How much for a pair of 476Be? ;) ]

[4313B]

Now I see where all the recent posts came from.....

The two units are not perfectly matched. Don't know if I'm going to do anything about that, tho, at this point....They are fine for their intended application.
I found the price, at $1315 it is less expensive than the list price for the 2435HPL.Buy them! JBL would love to sell a ton of them!
I would love to see people here buy a ton of them.
I wonder why they are less expensive than a 2435. :hmm:
Who cares! Just buy them. :yes:
If you have 2 of those and 4 2235H's, you really need to throw them together with an Everest style crossover and let us know how they sound with your 2452 horns.I'd use the dual 1501AL's, 476Be and the Everest II horn myself.
How much for a pair of 476Be?$7,000 at present but that could go up.
If current practice continues the diaphragms won't be generally available (to put into legacy 4" cores) since JBL does "driver replacement" on these high ticket items. You blow a driver, you get a new one (often within 48 hours).

[Zilch]

$7,000 at present but that could go up.
If current practice continues the diaphragms won't be generally available (to put into legacy 4" cores) since JBL does "driver replacement" on these high ticket items. You blow a driver, you get a new one (often within 48 hours).OUCH!

That puts them into an especially rarified zone for DIY, I'd say.... :(


Now I see where all the recent posts came from.....Yeah, not just slappin' stuff together randomly anymore.... :)

[4313B]

Yes, not just slappin' stuff together randomly anymore.... :)As of today?

Cool!
:band: :dj-party: :dancin: :cheers:

[Zilch]

:rotfl:

[4313B]

OUCH!

That puts them into an especially rarified zone for DIY, I'd say.... :( It looks like the MSRP price on the 435Be and horn combo is $2,690 a pair. That's the best available for a DIY project for now. One could substitute in any one of the aluminum or beryllium, aquaplased or non-aquaplased c.d. variants as desired but none of them will sound quite as nice as the 435Be.

I highly doubt JBL is going to make the 476Be and horn combo available for years and years.

I wish some forum member would be able to clone that H9800 that you are currently borrowing.

[Guido]

I wish some forum member would be able to clone that H9800 that you are currently borrowing.

:bouncy:
Can you hear us in St. Francisco?

[matsj]

Give me the drawings on the horn so shall i let a man make them in his CNC.

regards mats

[4313B]

I think Mr. Widget posted them somewhere or has them somewhere.

[Zilch]

1) Throatless "pancake" drivers, neodymium magnets, 4" diaphragms, 1.5" exit, both have 3.25" bolt circles, contrary to 2452H spec sheet:

http://www.jblproservice.com/pdf/Discrete%20Sales%20Models/2452HJ.pdf

2) Terminals are attached directly to the diphragms, ribbed for 2452H, smooth and Aquaplas'd in the "-SL" version. Rear cap damping is a felt pad, not foam. Plastic bushings in the cap seal to rubber standoffs under the binding posts.

3) If the phase plug is plastic, it's a damn hard one. Reddish silicone O-ring around the body perimeter makes a seal to the cap. No ferrofluid.

4) Performance on PT-F95HF, a direct bolt-up. L/R 24 dB @ 600 Hz for protection only. #7 and 8 have diaphragms dated last month, #5 and 6 are somewhat earlier and broken in, if that matters.

"-SLs" played on different horns @ 1.2 kHz with compensation for Ian's visit, so a half-dozen members have heard them here....

[Hoerninger]

I wish some forum member would be able to clone that H9800 that you are currently borrowing.

The whole thing might be practical if the lower and upper part of the horn are glued together out of some sheets of plywood (pyramid style). The steps need to be sanded.
Some recalculation might be necessary, the final handcraft is not that hard.

Just a proposal.
____________
Peter

[pos]

I came accross this 2450SL photo in an ebay auction.
What I found interesting is that the diamond surrounds are not aquaplassed, whereas the 2452SL (http://www.audioheritage.org/vbulletin/showthread.php?3450-2450-Dia&p=185313&viewfull=1#post185313) and 475 (http://www.audioheritage.org/vbulletin/showthread.php?3450-2450-Dia&p=95624&viewfull=1#post95624) diaphragms have their surround aquaplassed. Any idea why it is so?

[JeffW]

I have a set of D82450SL phragms that don't have aquaplas on the surrounds.