Urei 813B Baffle layout

[eso]

Can anyone provide an accurate layout for the baffle of a Urie 813B cabinet? I would like the locations for the driver cutouts and accurate size and position for the crossover/vent holes.

I'm building a pair from parts gathered up and would like to get the layout correct. I've searched the archives and can't find anything more than vague decriptions, and my request tagged onto another thread has been unanswered for a while.

Any help would be appreciated. And a set of real drawings would be really great, but I doubt that will happen.

Thanks,
Eric

[Bob Womack]

Hi, ESO!

I pulled out a ruler and went to work on our UREI 813B/Cs. Because of our particular setup, the speakers are oriented with the bass driver on the top and main driver below, near ear level. The port is next to the bass driver and the control panel is next to the main driver. These monitors were furnished with left and right mirror image cabinets. Basically that means that the port and panel are set together on opposite sides for the left and right speakers.


This is the right-hand speaker in the soffit.

Here are the dimensions I got:

Port - 2" down, 1" from edge, 7.5" tall x 4.75" wide

Edge of bass driver basket flange is 2/75" from top edge and centered left/right

Edge of main driver basket flange is 2.25" from bottom edge and centered left/right

Crossover control panel is 1.5" up from bottom, .75" from edge, on same side as the port.

We power ours with a Hafler TransNova P7000 amplifier and use Klark-Teknik DN360 graphic EQs to smooth them out. All that is mounted in the machine room. We've tuned them with white and pink noise and we've shot Fast Fourier Transforms of the room. The speakers are inserted into boxes built with two layers of 3/4" plywood that are mounted to steel posts. We cut through the foundation of the building and poured separate footings with bolts to secure the posts. After that, floating floors were installed and the room's shell built around, but not in contact with, the existing speaker mount assemblies. As a result, the speakers are totally isolated from the structure of the room.

The control room is an unlicensed Live-End dead-End room, designed by an engineer who studied at Syn-Aud-Con. The front end is as anechoic as possible and shaped to pass all residual reflections to the back wall.



The acoustically-significant portions of the rear walls have been treated with RPG diffusers. We sent the blueprints for the facility to Dr. Peter D'Antonio at RPG and he designed diffusers to the space. Here is a shot of the rear:



I'm reproducing this info on the forum so others can benefit. I hope that helps a bit in your quest!

Bob

[Bob Womack]

Oh, yes, I've never seen plans for these cabinets.

Bob

[Bob Womack]

Geez! Another post.

Within the cabinet, there is a partial baffle between the two drivers. I don't have the systems apart or I could give you details.

Bob

[eso]

Bob, Thanks all of the info!

From what I can gather the cabinet volume and the actual vent area is not really critical because the design not a port but an overstuffed box with a pressure bleed off.

With the baffle layout measurements you've provided I can build the rest easily. I will be using baltic birch ply instead of particle board because I have some and like the stiffness and density of it. Just a big box braced to be as stiff as possible to prevent energy loss through vibration.

I'll remark more later... I'm still working...

eso

[doodlebug]

Adding to Bob's awesome installation, here's a small pic of the innards of the cabinets for the 1st generation.

You can see the 'baffle' of insulation fitted between the 2 cutouts. It is about 1 1/2" thick glassfiber insulation material that appears to have been stiffened in some way with a spray-on material. It feels sort of like spraying hair spray onto insulation. You can feel the stiffness but it otherwise feels like insulation. There's nothing in the middle to affect the stiffness except what's been sprayed onto it. It covers the entire cabinet front-to-back and side-to-side and is only sitting in place; not tacked in.

Cheers,

David

[eso]

Geez! Another post.

Within the cabinet, there is a partial baffle between the two drivers. I don't have the systems apart or I could give you details.

Bob

I doubt that the inner baffle is critical other than adding stiffness. My plan is be brace the snot out them using Baltic Birch which is considerably stiffer than the material originals were made from

Could you measure the crossover plate and the removable plate to change the bulbs?

Thanks again for all the help,
eso

[eso]

Something like this:



Very cool. These things sure are a big ugly box....

eso

[Bob Womack]

I'm up to my eyeballs in a project involving a live concert broadcast mix and the corresponding recording for a later 5.1 mix for a DVD and am away from my home control room right now, but I can try to run over there to measure it for you tomorrow if I can remember. Can you shoot me a PM to remind me to do this please??

Bob

[Bob Womack]

Okay! I've got your dimensions:

Control panel: 5.5"x8.25"
Light Panel: 1.75" x 6 1/8"

Light panel is inset 7/8" from the long side and centered, ie 3/4" from the short side.

Tweak shafts in their collars and fuses are centered in remaining space. Light panel is secured to control panel with captive machine thumb screws that thread into tapped holes.

Does that help?

Bob

What took me so long:

Mixing a live concert broadcast on the Neve Libra Live II. Here I'm preparing to switch the faders from volume to "All Aux" mode to adjust the reverb send on the vocals. I'm simultaneously recording the individual inputs to Nuendo for a later 5.1 mix for DVD. Those inputs came over to my control room, 1/8th of a mile away, via MADI digital audio networking. If you look hard you can see the JBL LSR4328P powered, self-calibrating monitors I'm using. You can't see the LSR4312SP subwoofer but it is there, inboard of the left monitor. They all network together and self calibrate via an included instrumentation mic, which takes literally about 30 seconds. I'm pretty chuffed about this monitor system. It's the first system down the pike that makes me think there is life after the UREIs.

[Bob Womack]

Adding to Bob's awesome installation, here's a small pic of the innards of the cabinets for the 1st generation.

You can see the 'baffle' of insulation fitted between the 2 cutouts. It is about 1 1/2" thick glassfiber insulation material that appears to have been stiffened in some way with a spray-on material. It feels sort of like spraying hair spray onto insulation. You can feel the stiffness but it otherwise feels like insulation. There's nothing in the middle to affect the stiffness except what's been sprayed onto it. It covers the entire cabinet front-to-back and side-to-side and is only sitting in place; not tacked in.

Cheers,

David

Recently, when I removed the bass helper speaker from one of our cabinets to send it out for re-foaming, I lost my grasp of the nice acorn nut that held a clamp on and it dropped off into the darkness of the control room floor. Though I spent a long time on my hands and knees with a flashlight, it hasn't been seen since, so we have a tacky stainless nut holding on the clamp. Thank goodness that the speakers are covered.

Bob

[doodlebug]

Recently, when I removed the bass helper speaker from one of our cabinets to send it out for re-foaming, I lost my grasp of the nice acorn nut that held a clamp on and it dropped off into the darkness of the control room floor. Though I spent a long time on my hands and knees with a flashlight, it hasn't been seen since, so we have a tacky stainless nut holding on the clamp. Thank goodness that the speakers are covered.

Bob

Collorary to Murphy's Law: The Law of Selective Gravitation

"A screw will fall into the least accessible area."


BTW, that's good to see you in action, Bob. That's the job I imagined I wanted to do when I was in high school.

Cheers,

David

[Bob Womack]

Thanks, David. Been at this for some twenty-nine years. It's been getting more interesting of late.

Bob

[eso]

Does anyone have a copy of the 811B/830 crossover schematic? I'd guess it's the same as the 813B/840 crossover without the leg that feeds the helper woofer (LP, filter and low frequency protection)

Can some one steer me to this information or at least confirm my suspicion?

esp

[Bob Womack]

HERE is the 811C manual with the schematic.


And HERE is the 813C manual with the schematic.