convert 2404H to Bullets?

[sekess]

Hi,

I have a pair of 2404H's and was thinking of possibly switching from the baby cheeks to bullets.

If I was to find an inexpensive pair of blown bullet tweeters, is it possible to just unbolt the baby cheeks lens and bolt on the bullets. Is that all there is to it? Or, is it more involved (or not possible)?

Thanks,
Steve

[Earl K]

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=7798&stc=1&d=1116701149
Hi Steve,

- I don't know the actual answer to your question / but thought you should be made aware that there are other DIY possibilities .
- John W made new walnut horns for his 076 tweeters . Here are a few pics ;

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=7797&stc=1&d=1116701143

They were used in this stunning creation of his .

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=8432&stc=1&d=1118715164
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=8959&stc=1&d=1121438770
He has also turned on a lathe, small circular horns that are driven by JBL 2407H drivers .
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=26602&stc=1&d=1184947057
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=26603&stc=1&d=1184947065http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=26604&stc=1&d=1184947074

And here's another creation ( I'm a real fan of Johns' handiwork ) ;http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=32627&stc=1&d=1211646690

cheers

[spkrman57]

Sigh, I have no such talent/ability to create such georgeous looking speakers!

Regards, Ron

[sekess]

That is some nice work. Nice pics too.

It looks like the outer portion of the horn could just bolt on in place of the baby cheeks. But, I was concerned about the center conical guide. I do not know how that guy attaches to the diaphragm.

Thanks,
Steve

[Earl K]

It looks like the outer portion of the horn could just bolt on in place of the baby cheeks.

- That's correct / any new outer horn assembly must be constructed to use the existing threaded receptacles found in the magnetic housing .



But, I was concerned about the center conical guide. I do not know how that guy attaches to the diaphragm.


- It attaches to the magnetic assembly / not the diaphragm . I'm unsure if it presses against the center ring ( of the diaphragm ) or stands-off slightly away from it .

- Anyways, that central phase plug is held in place by a single bolt that enters through the back of the magnetic assembly and then into the phase-plug . The foilcal-decal at the back of the magnet must be removed to get to this bolt ( a hairdryer or paint-stripper type heat gun and a small putty knife will facilitate this removal ).

*** Notes***
- These diaphragms are easily crumpled if you turn the center-bolt without firmly holding the phase-plug / don't let the phase-plug turn-against the flimsy aluminum diaphragm .
- Have a professional do this disassembly/assembly if you're concerned about your ability to avoid damage .***

>< cheers

[sekess]

Thanks Earl,

It looked like it wasn't as simple as just changing the horn assembly. Thanks for the info.

Steve

[4343]

Thanks Earl,

It looked like it wasn't as simple as just changing the horn assembly. Thanks for the info.

Steve

I have a pair of clean Alnico 2402's, and have been looking to change them into 2404's...

Maybe we could trade?

[dino]

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=7798&stc=1&d=1116701149
Hi Steve,

- I don't know the actual answer to your question / but thought you should be made aware that there are other DIY possibilities .
- John W made new walnut horns for his 076 tweeters . Here are a few pics ;

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=7797&stc=1&d=1116701143

They were used in this stunning creation of his .

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=8432&stc=1&d=1118715164
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=8959&stc=1&d=1121438770
He has also turned on a lathe, small circular horns that are driven by JBL 2407H drivers .
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=26602&stc=1&d=1184947057
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=26603&stc=1&d=1184947065http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=26604&stc=1&d=1184947074

And here's another creation ( I'm a real fan of Johns' handiwork ) ;http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=32627&stc=1&d=1211646690

cheers who did the cabinet work on these speakers- awesome work on the horns and tweeters as well . :applaud::applaud:

[Earl K]

Hi,

John W does all his own cabinet work / as well as horn making / as well as passive crossover assemblig . Gorgeous work, isn't it ?

>< Earl K

[pos]

:)
I think John W's creations deserve an homage topic of their own, some sort of best of! I am thinking about doing that for some time now, just have to find the time to research all the topics...

Concerning the 2407 horn, I have used a similar horn myself:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=270-314

the problem is that above 10khz the mouth of the driver (ie the throat of the horn) is already quite big and controls the directivity.
I found no real difference witht using the 2407 without any horn.
Maybe a solution would be to have a diffraction slot such as the one in the 2344. At these high frequencies maybe a new phase plug would be better, on top of the existing one, with a smaller throat?
I was thinking of attaching the 2407 to that horn, just as a test:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=270-041
But the phase plug is too large (something like 1.5" or 2").

Do you know of any UHF horn with that sort of thing that could fit a 1" screw on driver?

[Zilch]

I don't know how high they'll go with which driver, but the new 6" square 90° x 90° PT waveguide may be worth a try at a whopping $6 apiece:

http://www.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=1078

http://www.jblproservice.com/pdf/AE%20Series%20Compact%20Models/AC16-WH.pdf

[pos]

very interesting, thanks Zilch!

There is a vertical slot, so the horizontal directivity looks quite good up to 15 or 16khz in the graph. It is not shown above that point, but I guess it goes south. That is quite impressive already!

[pos]

to put things in perspective:

2402H: http://www.audioheritage.org/vbulletin/showpost.php?p=60869&postcount=2
2403H: http://www.audioheritage.org/vbulletin/showpost.php?p=60871&postcount=4
2404H: http://www.audioheritage.org/vbulletin/showpost.php?p=60872&postcount=5
2405H: http://www.audioheritage.org/vbulletin/showpost.php?p=60870&postcount=3

[Zilch]

That is quite impressive already!Stunning, actually.

For what it may be worth, it sounds good, too. I have Selenium D220Ti running on it in the background here today.

The full-range frequency response curve shows it playing up through 20 kHz; we don't know the directivity up there, is all.... :dont-know

[Note similarly configured 2404H/116H in my Mini in the background. :thmbsup: ]

[pos]

Could you please post a photo of it?

There was no apparent slot in the SF-95:
http://audioheritage.org/vbulletin/attachment.php?attachmentid=7976&stc=1&d=1117357529

Is there a more defined diffraction slot in this one?

[pos]

now there is a photo, thanks :D

So there is not real diffraction slot either?
How do they manage to get such a good directivity without narrowing the throat?
The UHF is better controlled in the horizontal plan than the vertical one, so there should be *something* :D

[Zilch]

That's what PT waveguides are about. Read the PT white paper:

http://www.jblpro.com/catalog/support/getfile.aspx?docid=277&doctype=3

Disparaging PTs in another forum, Geddes called the contoured narrowing of the flare a "diffraction device," and therefore unworthy, by his view. Rob then stumped him with a CSD plot of one of his.

[We bad, heh, heh.... :p ]

[pos]

I am familiar with this paper, and I also read the discussions you had with Earl on Diyaudio ;)

The UHF dispertion control of this waveguide is the best I have seen yet. Much better than the SF-95:
http://www.jblpro.ru/pdf/AC2212_95.pdf

Does it have a metal screw insert?

I think I am going to buy a pair, thanks a lot for the pointer! :bouncy:

[Zilch]

Does it have a metal screw insert?There's no insert, but it's more ruggedly built than the $9.90 SF-95, which has itself become somewhat popular since Mr. Widget and I first "discovered" it here years ago.... ;)

[pos]

There's no insert
Really? I thought the 2414H was a screw on driver, as it replaced the 2408 in several models:
http://www.jblproservice.com/pdf/PRX%20Series/PRX535.pdf

So lets find a good screw/bold adapter! This is a never ending quest :banghead:

[Zilch]

It has a thread-on throat, but it is molded plastic, not a metal insert, is what I'm saying.... :yes:

[pos]

Great! :applaud:
I guess it is strong enough for a tiny 2407!

[pos]

Does a 90°x50° version of this waveguide exist?

[Zilch]

The 8" square version comes in 90° x 50°.

[pos]

The one used in the AC18 ?
http://www.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=1080

This is the PT-D95HF-1, where D seems to indicate a 8" size.
Looks interesting, but I would like to stay with a 6" version (same high as a PT-F95HF)
What I would like to find is a PT-B95HF-1, that would be the 90x50 version of the PT-B99HF-1 of the AC16
But google says it doesn't exist yet... :(