Old Speaker Questions

[101Tom]

Hi

I made a post on Homerecording.com about these old speakers I have. I was advised to post here. Link to post http://www.homerecording.com/bbs/sho...d.php?t=133037

This is what I posted

Hi

Im new to these forums. I have a couple of large old cabinets lying around, My old band was given them by a recording studio as they had no more use for them. I am not currently in a band but im keen to get back into it and if I do i think I may setup a bit of a PA/Home studio (nothing too flash) but something good for practaces and a bit or recording.

I was wondering if these speakers are worth using? The surrounds on one of the low range speakers has come apart but I can get that fixed for a pretty decent price.

Getting into the speakers. The cabinets are large and house 2x 15" speakers in each one. The low range is a JBL Pro 2234H 15" and the midrange is a Urei 604-8G 15" with a horn in the centre of it. Im guesing these are old as the Urei speaker has a date 12/13/79 on the back (im assuming this is a date) I will add a link to photos at the bottom of thist post. There is also a what looks to be a crossover? wired up to I think the horn speaker, I cant remember from when I took the photos but I think thats what its connected to. There are 3 inputs on the back where you just screw the speaker wire into, Low Mid and High.

What im wondering is what equipment would I need to make use of these speakers? I understand I will need a Mixer and an amp to power them but will I need some sort of crossover? money is a bit of a problem so I want to keep cost to a minimum, Could these speakers run without a crossover or would it damage them without one? If i didnt need a crosover would it would best to wire all 3 speakers in series as the JBL speaker is rated 8ohms.

I do not know alot about the technical side of electronics/speakers but I do know a little and I can pick it up pretty quick so I thought I would ask you guys who will know a whole lot more.

Here are some photos of the speakers http://www.101tom.orcon.net.nz/speakers/

Any info would be greatly appreciated.
Thanks, Tom

[Don McR]

What you have appears to be a modified UREI 813. There were four series in this model (813,813A, 813B, 813BX, 813C). Your system has the Altec Lansing coaxial driver from the original 813 (circa 1979) and the JBL bass driver from the later 813BX (circa 1986). This upgrade could very well have been done by UREI since they were known to provide this service.

You absolutely have to run this system with a proper cross-over. In fact, the specially designed "Time Aligned" UREI cross-overs are arguably the heart of the 813. Not only did it divide the audio spectrum to keep each individual driver operating within its designed bandwidth, but it also contained sophisticated equalization to result in an accurate system response. The "Time Aligned" trademark refers to proprietary delay circuitry to the midbass cone to compensate for its physical location in front of the tweeter. It allows the combined midbass/tweeter to act as a single point source.

I'm not clear if the cross-over is still installed in the cabinet. The pictures you included just seems to show the connectors and not the actual cross-over. You can see the front face plate of the cross-over in the lower right corner of the photo of an 813A that I have attached below. You'll have to let us know if this is still in place in your system.



If you don't have the cross-over, you have a few options, but all are problematic. UREI was bought by JBL in 1984 and they shut down the brand in 1996. Subsequently, they no longer support the 813 monitors. Therefore, replacement parts have to be scrounged from the used marketplace. Unfortunately, 813 cross-overs almost never show up individually. You could try and design your own cross-over. I have schematics for the 813C version, but no others. That system used different drivers than your system so I would be doubtful that it would work out that well. The most viable option is also the most expensive. That is to use an electronic cross-over and tri-amp. This would give you the flexibility to replicate the time alignment and equalization.

As a final note, this system would not make a good PA speaker. The 604-8G is only rated at 60W and it is quite easy to blow the HF driaphragm. It may suit your purposes as a "home PA". but you would nonetheless have to excercise caution.

[101Tom]

My cabs look almost identicle to that picture, I do not have that crossover, I have looked around the cab and there is nothing that looks like that.

I would probly rather spend my money on a new PA system that pay heaps to get use out of these. I just thought that since they are there i may aswell look at finding a use for them.

Thanks for your reply.

[Steve Burger]

Those are some really excellent pieces but as Don advises, I would be very careful using them in your application. For a reference speaker you couldn't do much better. Do you have an idea of the value of them?

[Steve Burger]

Those are some really excellent pieces but as Don advises, I would be very careful using them in your application. For a reference speaker you couldn't do much better. Do you have an idea of the value of them?

[101Tom]

I have little idea of the value, similar models have been going on ebay for around $1000us a pair but that is with the crossovers.

[David Yost]

I have a pair of new-in-box 813BX crossovers that were designed for your speakers that I will sell for a reasonable price if you are interested. Please email @ [email protected].

BTW, it seems that the 813BX was an intermediate design between the 813B and the all JBL 813C. I have never heard the X version, but with the correct crossover it should sound very good.

David

[boltupright]

Those 604 8G's are awsome speakers, If I had those I would make a nice 620 cab & find some 8G crossovers & use them for HI FI !!!

[joyspring]

Tom,

The schematics for the original UREI 813 are available online:

http://www.jblproservice.com/pdf/Vin...s/UREI-813.pdf

The schematic is on the last page of the .pdf document.

While the original UREI 813 utilised a UREI/Eminence 800W LLF driver rather than the JBL 2234, I would not worry quite so much about using the original UREI crossover with the JBL.

Taking a closer look at the schematic, you'll notice that the additional LF driver is merely low-passed at approx. 200hz; there is NO time-delay involved with the additional LF driver.

This makes sense as at 200hz, even the time displacement of the HF driver vs. the additional LF driver falls well below the Blauert-Laws criteria for perception of time delay.

Between 1-2kHz for the 604-8G driver, that is a totally different matter ;-) and that's where the Time-Aligned(tm) crossover excels. It does not merely correct phase and sum flat (as other networks available online do) but uses cascaded all-pass Bessel filters to achieve _true_ time alignment.

Anyhow, I believe that the original 813 schematic is your best bet to get your lot working. You can dispense with some of the items detailed (i.e. - light bulbs, fuses) with no sonic effect as well.

And to reiterate what others have mentioned above the 604-8G will NOT be suitable for live sound reinforcement at all; it's far too fragile.

Good luck with your project,
BobR

[speakerdave]

I'v been following this thread with interest and have just looked at the UREI 813 manual linked above. I am wondering if anyone has used this schematic on the 604-8G without the UREI blue foam-edged horn. If so I would appreciate learning of your results.

Thanks,

David