Urei 813a diy help

[nick]

Hi All,

I was wondering if some one has some plans for the UREI 813a cabinets. I'm trying to build some clones but can't find any plans.

Any help would be great.

Thanks

Nick

[speakerdave]

The manual can be found here:

The gross dimensions are:

[nick]

I actually have the manuals. I'm trying to find if there are reflex or suspension. Also if there is a baffle between the 2 drivers.


Also if they are reflex what are the port dimensions too.


Thanks for the help,

Nick

[speakerdave]

They are a damped or restrictive port type of tuned box.

[nick]

I'm not familiar with that kind of port, is it exactly as it says,, restricted meaning pretty small and adjustable,, in length or diameter????


Nick

[speakerdave]

It's an opening in the cabinet, say 6" or 8" square, with layers of air-permeable material held across it by two pieces of wire mesh. Or, you could stuff a standard duct. The effect is to dampen resonance and lower the impedance peak (and lower efficiency). As far as I know there are no formulas for designing this and making one is largely a matter of cutting and trying. The best thing would probably be to get an 813 owner to give you a description of one.

We have a UREI guy who comes on here--UreiCollector. Try sending him a PM.

What driver(s) are you using? The 813 (and other UREI) cabinets were designed to be useable in a soffit space in a studio. That required a small size that was made more acceptable by the restrictive port tuning, I should think. The designers were also able to count on bass reinforcement provided by the built-in placement.

Without the restrictions UREI was operating under--soffit space and commitment to a certain driver-- there are other options: a larger box or a different choice of driver. For a freestanding speaker using the Altec 604, a larger cabinet with standard ducted port tuning would go lower and be easier to design and build. If you want to add a helper woofer for lows it will get a bit more complicated than I would really understand. Altec made such a speaker toward the end of its days using a 416 added to the 604.

Do you have crossovers?

If you want to pursue the damped port type of box, you can read around the web about it by googling "aperiodic."

[subwoof]

I have a pair of 813B cabinets here and the material used to cover the port is too porous to have any effect on the airflow - it is more of a dust screen than anything else. The identical sized hole at the bottom is used to mount the crossover control panel ( other 1/2 is in the back )

The box however is stuffed with the dense 3/4 fiberglas ( like used in ceiling panels ) and a thick piece separates the chambers but is of course not airtight.

For a pair of 15's it's a large volume cabinet. The 801C woofer is not a sub driver ( E145 ) and it's helper is a 2215H - an older, less efficient version of the 15" foam surround family.

However I might want to get rid of these boxes after the semester ends when I renovate the house system -you cab see the boxes here:

And I have the grills.

sub

[nick]

Subwoof, what are the horns? Did you bypass the tweeters or are the mid horns?

Also could you tell me the the length of the vent pipe?


Thanks,
Nick

[subwoof]

The horns are JBL 2360 with modified 2445H's ( coated ).

The horns and cabinets are the EXACT same width, and since these are near impossible to sell / ship it ended up in my college rental house with a pair of JBL/UREI amps and such.

The woofer baskets are E140's with 2225H kits - again hard to resell but perfect for this app. these absolutely KILL..

The first week of may the house will empty and these cabs are available - and the horns should you want to go that route. There are 2404's ( not pictured ) with 3105 clone crossovers to add that sizzle available.

The vents have NO length - the opening is 4.75 by 7.5

The stock urei/jbl coax drivers are very nice sounding but I find the larger format horn / driver combo's easier on the ears and are almost poof-proof.

sub

[nick]

Just curious, how much would you want for the cabinets?


Nick

[doodlebug]

There are differences in the A and B series cabinets. Nick, it might be good to explain what drivers you'll likely use. I also have a set of cabinets (and driver/crossover compliment) in Arkansas but they are the A series. I'm relocating to North Carolina and pretty sure I'll not have room for them.

The internals on them are similar to subwoof's description. In his picture, you see dual ports per cabinet on the B series while the A series had only one port. Front faces are 1" plywood with sides and back 3/4" ply and lots of 2x4 bracing.

I'll be back in Arkansas in a bit over a week and should be able to get some pics of the internals, if you'd like.

Cheers,

David

[nick]

Doodlebug, thanks for the offer but I I wouldn't want to even try and get them shipped.


As for the other question you asked I will be using the p.audio 15" coaxial driver and a high efficiency 15" driver for the the low, of which I haven't decided yet.



Nick

[subwoof]

The cabinets I have normally use a single port. The second, identical size hole as pictured is where the front panel crossover plate is/was mounted.

sub

[doodlebug]

Doh! That's right, subwoof. My mistake on that detail.

Understand, Nick. They'll just follow me around for a while yet.

Cheers,

David

[subwoof]

The front panels on mine are 1" particleboard. These puppies are heavy...