Slot Resonator Construction

Riad · Post by **Riad** » Tue Jan 13, 2004 7:02 am

Hi,

John helped me design my studio and he noted a slot resonator against one wall in the control room.

Would I build this per the specs in the DIY section (below)?

knightfly · Post by **knightfly** » Wed Jan 14, 2004 9:29 am

Sure, except that you'd want to adjust dimensions to fit where the absorber is shown on your plan - if John specified a frequency range, you can figure out slat/slot dimensions with the helmholz calculator located here -

http://www.saecollege.de/reference_mate ... mholtz.xls

just use the average depth of your space behind slats for the "depth from wall" measurement - if you're not into metrics, just divide mm by 25.4 to get inches, or multiply your inch dimensions by 25.4 to get mm... Steve

Riad · Post by **Riad** » Wed Jan 14, 2004 10:46 pm

knightfly wrote:Sure, except that you'd want to adjust dimensions to fit where the absorber is shown on your plan - if John specified a frequency range, you can figure out slat/slot dimensions with the helmholz calculator located here -

http://www.saecollege.de/reference_mate ... mholtz.xls

just use the average depth of your space behind slats for the "depth from wall" measurement - if you're not into metrics, just divide mm by 25.4 to get inches, or multiply your inch dimensions by 25.4 to get mm... Steve

Thanks Steve. I'll do the calculations with the excel spreadsheet.... the wall shown in the drawing is flat, however, it should be a saw tooth design as per the second schematic, correct?

Rob

knightfly · Post by **knightfly** » Wed Jan 14, 2004 11:06 pm

No, in your case the absorber should be built as shown in John's drawing, as one continuous flat surface. What you're looking for in a control room is symmetry from left to right - since your right side wall is reflective glass, the left side needs to balance that out but without causing problems with early reflections. By building a slat resonator there, you absorb lower mid frequencies there balancing out the room response, but keep the room symmetrical. The rear is then absorbed so that the reflections which are deflected away from the mix position are attenuated at the rear of the room so they don't screw up the stereo imaging at the mix position.

The reason the absorbers in that link are sawtoothed, is to minimise space requirements in smaller rooms when the absorbers are built as freestanding units. It's a compromise solution, with arguably enough depth to solve flutter echo and early reflection problems but without eating too much valuable real estate.

However, you're building splayed walls so should do it all, or else just live with parallel wall problems - I would just build the absorber as one continuous plane as John's diagram shows... Steve

retrograde · Post by **retrograde** » Thu Jan 15, 2004 5:15 am

John (and Steve): as we designed it my control room design has glass sliders on both sidewalls musch in the ame configuration as the drawing above has on the one side. Is this going to duplicate (intensify) the reflections or cancel them???? I don't have place to post the design John. Can you??

Geoff

Riad · Post by **Riad** » Thu Jan 15, 2004 6:10 am

Thanks for the clarification Steve.

knightfly · Post by **knightfly** » Thu Jan 15, 2004 4:32 pm

Riad, you're welcome -

Retro, you can post drawings here, as long as they're on your hard drive - just click Browse, next to the filename box - then, find the file on your hard drive, select it, and submit. Works with several different graphics file types... Steve

retrograde · Post by **retrograde** » Fri Jan 16, 2004 1:10 am

Thanks Steve. Here is the design JOhn and I settled on.

retrograde · Post by **retrograde** » Fri Jan 16, 2004 1:17 am

Here is the entire plan to put the control room in context

knightfly · Post by **knightfly** » Fri Jan 16, 2004 7:36 pm

Reflections off your front, splayed walls won't be a problem - they will mainly get re-directed to the rear of the room, where they will be "diff-sorbed", from the look of it

However, the soffits for your rear surround speakers will cause early reflections back to the mix position unless the faces of the soffits are absorbed. If you "play pool" with a sound from your left front speaker, "shooting" a "bank shot" off the forward edge of the baffle for the right surround, you'll see it ends up at the mix position after traveling only about 8-10 feet further than the distance it takes to get to your head. This would put the delay at under 9 milliseconds compared to the direct sound from your front speakers. There is also the likelihood (without actually Ray Tracing the drawing) that right front and right rear will interact the same way.

Anything less than around 22-25 milliseconds gets integrated by your brain into the original sound, and phase cancellations/additions, known as "comb filtering", degrade the stereo image.

For a Stereo-only, Reflection Free Zone control room, only the rear wall surfaces need to be absorbed, or (if the room is larger) possibly diffused. When you add surround to the picture, it gets a lot more difficult to get everything to work.

I'm badly in need of some rest soon, so I'll let you search the site - try searching on "5.1", "surround", etc - there are threads where we've discussed this before; you should be able to find a fair amount of info on the subject, although surround is relatively new and not as "cast in stone" as stereo.

I'll try to check back tomorrow sometime, meantime try a search... Steve

retrograde · Post by **retrograde** » Sat Jan 17, 2004 1:52 am

Steve: If and when I start using surround monitors, l'll probably end up using small speakers mounted with wall mounts rather than use the soffits.

Should I throw some absorbers above the sliding doors on each side of the control room or will the angle of the doors take care of reflections?

Geoff

Post by **John Sayers** » Sat Jan 17, 2004 7:03 am

Hi Geoff - I just noticed you have joined us. welcome - Mate - as I remember (when did I draw that? two years ago??) you don't have any room above your doors as you have a very low ceiling height. The splayed doors will take care of the RFZ area.

cheers
john

retrograde · Post by **retrograde** » Sat Jan 17, 2004 9:15 am

John: I've been a member of the forum since July. However, I've been lurking until I had something to say or a question to ask. You are correct, the ceiling is low. I do have room for a small angled trap or diffuser over each door though. The would have to be fairly narrow though.

John, it will be three years ago this this March that you started working on this studio. Do you want to post some pics? I'll send you some by e-mail.

Geoff