2450 Dia

[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....

[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/s...&postcount=675

[Zilch]

1) Stock 2450H, top, ribbed. Performing per spec, apparently: http://audioheritage.org/vbulletin/s...08&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.... ]

[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/s...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....

[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? ]

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 . 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 .