Urei 813b project

[Charles0322]

http://cgi.ebay.com/UREI-838-TIME-AL...QQcmdZViewItem

Those are out of the 813A...

[Charles0322]

charles0322,

are you planning on a RLA styled crossover in your system?
maybe some old crown crossovers...
old pioneer ones can be really nice as well...


seems to fit with the 'era' as they say....



on a related note...

I am picking up the Urei 809As i had gotten refoamed this afternoon



plan on using either a Crown DC150 or Phase Linear 200 Series II to power them

single EAW SB48e for subwoofer while i try to find/clone another three....

Nice! I just picked up three Crown PS-200's from a cinema install. I'm testing them all right now.

My D-150A series II is my baby, bought new in a local shop as old stk. I just love it. I'm actually getting better sound with the PS-200's..

I'm configuring the Crowns for a HT set up. B&W DM 602 S2 for the front, B&W DM 601 S1 for the rear, B&W CC6 S2 for centre & a quest subwoofer.

Looking for options for a 5.1 decoder from my PS3

Next is the Panasonic PT-AX200U projector..

As for the RLA.. I wish I had one.. There is a great tube version out called the Thrive ISO designed by Shorty. I'm a saving but this hobby is the mother of all hobbies, hobbling my bank account!

[eso]

The 813 A,B,C all use different drivers and crossovers. They are not interchangeable. If you have "B" there shouldn't be any JBL helper woofers in them. In the BX they had 2234's. The Le-15 and 2234 are almost equivalents as far as there LF extension.

Take a look here.

http://www.jblproservice.com/pdf/Sys...I%20Series.pdf

You can get the schematics here for the "C"s:

http://www.jblproservice.com/navigat...%20Series.html

And the "A+B"s here in the last pages of the manuals:

http://www.jblproservice.com/navigat...ectronics.html

The Tapped Inductors for any of the "C" series all have to be custom wound if you can get the winding information from JBL Pro.

Rob

This is some information I've been looking for. What I'm still lacking is the Urei part numbers for the PAS low frequency drivers that were used, I believe, in the "b" series monitors.

I just purchased these:
http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWNX:IT



The schematics at the 2nd link are general and not sufficient to actually build a C-series crossover as the tapping points of the inductors are not given.

Now, does anyone know where to purchase the Urei horn with the foam surround NOS? I believe that horn for the b or c series will require the JBL 2425 driver with the threaded attachment.

I would like some Urei horns, as their dispersion is undoubtedly factored into the crossover filtering. Barring finding a pair of those I will likely make a pair out of fine hardwood similar to some made for some Altec 604 by Japanese horn aficionado Yuichi Arai that I'm currently trying to track down some pictures of.

Any help would be greatly appreciated.

eso

[Robh3606]

Hello Eso

The schematics at the 2nd link are general and not sufficient to actually build a C-series crossover as the tapping points of the inductors are not given.

Yes they are of limited value. I have the tap information on the 811C coil and wound one to make an 811C clone. I use it as my center chanel. I can post the information if you want it. That said I wouldn't use that crossover with the PAS woofer. The 811C used and E-145 as the 15" and I doubt the spacing is the same between the voice coils in both woofers. From the pictures it looks like your compresssion drivers bolts on to the back using the JBL 3 bolt pattern. If that is so you would use a standard 2425/2426 as a compression driver.

On the "C"s they used a 2425S which looks like a 2426 without the 3 hole adapter plate. It's a standard 2425 with a threaded throat. So if you look at the off sets the 2425S threads into the E145 pole piece. That's going to give you a shorter VC offset than bolting on a standard 2425 assuming that the magnet and backplates have the same spacing as an E-145.

Now, does anyone know where to purchase the Urei horn with the foam surround NOS? I believe that horn for the b or c series will require the JBL 2425 driver with the threaded attachment.

You see them on E-Bay from time to time. Not sure which version you should get. There were at least 3 versions I can think of and have pictures of.

Could you please post some pictures of your drivers and the mounting plate??

Good luck making up your system and please post pictures of your progress as you go.

I think this is your woofer it was an 801B

http://www.jblproservice.com/pdf/Sys...I%20Series.pdf

Close-up of the "C" version horn. You can use that to compare what you have. It's a conical section that smoothly morphs into what look like an Exponential

Rob

[eso]

Thanks for the input Rob. I know the crossover was tweaked for each configuration, so after some thought I think it best to get the 2425 drivers and stick with the 840 crossover as it should be the correct match and also have the proper correction for the High frequency contours.

To get it right I do need to find out what the 800W woofer is for the extra 15", as the crossover is probably adjusted for that too, and Urei didn't use the JBL woofers until the 813bx and 813c series. That is unless I could find a schematic for the 841 crossover that matches that combination.

If you look at the ebay link you can see the horns that come with these drivers are very different from the Urei units: shorter overall with a wider dispertion pattern. The Urei horn appears to be more of a constant directivity device than one seeking greatest output.

http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWNX:IT

Thanks for the photos. Those are indeed the drivers. I'm going to try to make it out one day this week to pick up a pair of 2425s. The heatsink/magnet cover has a throat hole and mounting holes for standard 2 and 3 bolt patterns set up for counter sunk screws, the heatsink then screws to the woofer magnet with 2 1/4-20 countersunk screws. There are also bolts that mount the horn through the woofer magnet.

I'll try to remember to get some pictures this week.

Any idea on the 800W woofers?

Eric

[doodlebug]

If you are looking, I have a set of 800W woofers that are not being used. PM's are appropriate.

Cheers,

David

[eso]

Could you please post some pictures of your drivers and the mounting plate??

Here we go:


PAS CXL1580 without the heatsink

Mounting the 2425 to the heatsink

Mounting the heatsink on the woofer

Full set of 813B drivers

Sorry about the image quality from my cell phone with the broken lens, but you probably get the idea.

So, that's a full set of drivers for a pair of 813B. I need to locate either the Urei horns and install them or make a nicer pair than the stock PAS ones. And I'll start rounding up the crossover parts.

I did learn something today while picking up the woofers and compression drivers: A JBL 2425H IS a 2425HS with and additional mounting ring that actually threads over the 2425HS threaded snoot. This would explain why the "C" series is probably the best sounding series. With the driver threading directly onto the woofer that JBL coax assembly in the "C" series would have the least built-in time delay of any of the Urei monitors making the time alignment filter more simple and probably imparting fewer artifacts of it's own.

I may have to do some experimenting in that region at some point.

eso

[eso]

Rather than start a new thread I'll see if I can get any answers here.

After trying to buy a pair of the new GPA 604 HIII horn flares and being denied, and speaking with a tech at Harman Int'l about any NOS parts I'm going to have to make some new horns for the CXL 1580 drivers.



Can any of you provide a few measurements of your horns for me? Height and width of the mouth, the height of the arc at the mouth (Widest point when a straightedge is placed across the corner to corner of mouth), depth, dimensions of the slots, depth where the sides increase the flare.

Cross-section dimensions at a couple of points would be great.

I really want some blue urei horns, but the last order JBL placed for the b series was in 1984 and they purchased 1000 parts from a company that is no longer in business.

Anyone able to help with this?

Thanks,
eso

[Robh3606]

I will try to get you some dimensions. It's not easy with the foam in place as there is a lip that covers the actual end of the horn. As far as the angles I will post a couple of photographs you can then print and use the vanishing points to get the angles with a protractor. No way I can actually measure them with the horn mounted.

You can also use a Paint Shop like program to scale things using the pixels per inch once you have a know dimension.

The inside has a different contour than the flat outer wall on the sides. There are gentle curves you can see in the sidewall foam that are either in the foam or molded in.

The throat is going to be a real PITA as I don't think I can get a accurate measurement on the diameter or length. Same with the angle in the throat. If we can get a reasonably close length and the 2 diameters, figure one is 1" you can calculate the angle of the pole piece section leading up to the blue plastic horn.

Rob

[eso]

Rob, thank you. Even some measurements that are close can help me to reverse engineer the flare. I know just enough of the math for calculating horns to be dangerous.

So, is there a lip, or step near the mouth that the foam wraps around? I always thought it was basically a small square/rectangular strip that was to the outside at the mouth. Looking closely at your pictures I am now seeing otherwise.

Also, the two sides have some high density foam too? I think I am seeing that as well in your pictures.

This may be a good candidate for making a mould and using Urethane or epoxy.

While I was speaking to JBL tech yesterday I found that when the "B" version was last purchased in 1984 they paid $11.95 ea. for the parts from a producer in Sun Valley. The last of the "C" series parts were listed in their Pro support pricing as $98.95 in 2004.

I'm going to begin sketching something up in Autocad for this. I'll have to bring my work computer home...

eso

[Robh3606]

I'm going to begin sketching something up in Autocad for this

Can you wireframe from a photo/image file??

Rob

[eso]

Can you wireframe from a photo/image file??

Rob

I'm not that knowledgeable or skilled with CAD for that. But I know enough to draw a little bit.

Eric

[eso]

Well, I found these locally and I can study the horn design for fabricating new horns for my 813 clones:

http://cgi.ebay.com/ws/eBayISAPI.dll...:X:RTQ:US:1123

Any of you own both the 12" and 15" Coax horns? If so can you verify the horns are similar if no identical?

Thanks,
eso

[Robh3606]

Hello Iso

I waited till I got back to work to get a vernier to try some measurements.
The 809 horns are smaller without the slots, however the 1" transition should be the same. They use a 2416 which has the exact same throat dimensions as a 2425HS.

These dimensions are inside the horn. The widths are 6.100 at the termination of the inside blue foam pads at the end of the horn. At the other end of the pads the dimension is 2.250 inside. So it goes from 2.250 to 6.100 along the length of those blue pads. The length of the blue pads are 3.250. From the back of the pad to the metal throat transition is 2.375. The length of the transition is about 1 7/8 to the compression driver screen.

The height is 2.850 at the outside edge, I can't get any kind of decent measurement further down the horn. It's just too tight in there. You should be able to scale it with the known dimension in a graphics program.

The slots are 1.500 x .375 wide.

Hope this helps

Rob

[eso]

Rob,
Thanks. Between those measurements and being able to compare the geometry to the 809 horns I should be able to get really close.

One of the last challenges will be sourcing the blue foam for the mouth. I already have a pretty good idea for the inside foam panels. I'm picking up the 809s tomorrow afternoon. The seller within 10 miles.

eso