Resonant panel or slot absorber??

laptoppop · Post by **laptoppop** » Wed Apr 09, 2003 4:35 am

When would I want to use a resonant panel, and when would I want to use a slot absorber? To my little mind, seems like there's a lot of overlap there in controlling low mids.

Thanks,
-lee-

Post by **John Sayers** » Wed Apr 09, 2003 9:57 am

Panel absorbers are traditionally used for Low frequency absorption whereas slots are more Low-mid orientated. It's not feasible to get slots below around 150Hz (i.e. without taking up a lot of depth and space)

For mine panel absorbers are competing with hangers for low end reduction where they take up less space than Hangers. Unfortunately you usually want low end absorption in a rear of a control room where the reflective nature of the panels becomes a problem.

cheers
john

knightfly · Post by **knightfly** » Mon Apr 14, 2003 2:31 pm

I was just reading parts in Everest's Master Handbook the other day, and he mentioned that you could mount 703 in front of a panel absorber without noticeably affecting the panel absorber - this sounds like maybe you could use the 703 trick to get away from the reflections, and still keep things relatively compact for low mid absorption. Comments??? Steve

Post by **John Sayers** » Tue Apr 15, 2003 7:03 am

Yeah - I've done that steve - we had a wall of panel absorbers but it was too bright so I mounted 703 in front. - fine.

cheers
John

Sen · Post by **Sen** » Mon Apr 28, 2003 8:03 pm

John Sayers wrote:Yeah - I've done that steve - we had a wall of panel absorbers but it was too bright so I mounted 703 in front. - fine.

cheers
John

John, when you say "in front of it", do you mean stick it to the panel or in front but not touching??
Thanks

Post by **John Sayers** » Tue Apr 29, 2003 9:28 am

Sen - i actually built a false wall infront that mounted the insulation but didn't touch the panels. But I agree with Steve in that it doesn't matter if it touches.

cheers
john

knightfly · Post by **knightfly** » Tue May 06, 2003 8:47 am

Sen, what I got (sort of between the lines) from the Everest info was that the FRAMES could touch, but the 703 itself was "stood off" by enough so as not to affect the resonance of the panel absorber itself. As with almost everything in acoustics, there are several ways to skin this cat, and as always, YMMV... Steve

barefoot · Post by **barefoot** » Wed May 07, 2003 4:46 am

Yeah, as I've mentioned elsewhere, placing material close to the slot openings raises and broadens the resonance peak.

Just a general note on slot absorbers versus panel absorbers: Slot absorbers are much more efficient (absorption per unit area). Panel absorbers are very inefficient because the inertia of the panel must be overcome before any absorption can take place. The only inertial impedance in a slot resonator is the small mass of air that resides in the slots. The fact that slot resonators must be very large in order reach low frequencies is evidence of their higher efficiency. In acoustics, efficiency is almost always gained at the expense of increased volume.

Similarly, the greater the ratio of slot area to slat area in a resonator, the greater the efficiency. The tradeoff is, of course, extra volume. Resonators with high slot to slat ratios must be deeper in order to reach a given target frequency.

Thomas

Post by **John Sayers** » Wed May 07, 2003 11:14 am

In acoustics, efficiency is almost always gained at the expense of increased volume.

when I started out in recording in the mid 60's all the studios had what I call original BBC acoustics usually made up with panels of fibreglass (The old stuff) and slots/perforated holes and panel absorbers. Near the late 60's and into the 70's the bands started wanting to record with their stage rigs!! you usually only had one recording space so suddenly we were confronted with a live band producing 130 spl !! so much for isolation between instruments.

That's when the new acoustics started in the US, led by Tom Hidley, where whole walls and ceiling spaces were taken up with deep traps and up to 1/3 of the floor space became acoustic traps.

We've moved back from that position now as the studios were toooo dead and booths are now built to achieve the isolation but Thomas is right - to achieve the isolation/absorption in those days you needed space.

cheers
john

barefoot · Post by **barefoot** » Thu May 08, 2003 3:59 am

John,

Following your reasoning, and now with the heavy proliferation of pods, DI, virtual instruments, sub bass synths, 5.1, etc., it seems that the emphasis of studio acoustics has shifted away from the live rooms and much more towards the control room. Would you say this is a correct assessment?

Thomas

Eric Best · Post by **Eric Best** » Thu May 08, 2003 4:48 am

Barefoot,

I think that has been a fair assumption for a while, but I find that the new trend is going back to recording as a full band again in the same space.

Eric

Post by **John Sayers** » Thu May 08, 2003 9:13 am

studio acoustics has shifted away from the live rooms and much more towards the control room

well the control room has always had attention in pro studios - it's the proliforation of smaller semi-pro studios everywhere. Intitially the emphasis was on gear but that's settling down now and people are turning their attention to the acoustics of their spaces especially the control room, and as you say, most of the recording actually happens there.

To exemplify what I was referring to -I watched Paradise studios going up in Sydney in 1979 - designed by Hidley. Whilst the compression ceiling in the control room came down to around 7'6" the cavity above went up to 12' and was totally filled with hangers, the rear wall was 4' deep and full of hangers. Music Farm was similar - (we were building at the same time).

but I find that the new trend is going back to recording as a full band again in the same space.

I agree Eric, spill is coming back into fashion

:) I was talking with a bass player the other day who reckoned his bass used to resonate with the kick drum when he stood next to the kit and his bass sounded fuller with his amp spilling into the drums.

cheers
john

knightfly · Post by **knightfly** » Thu May 08, 2003 9:25 pm

Yeah, my voice sounds fuller after a beer spills into my mouth... :=)

Eric Best · Post by **Eric Best** » Fri May 09, 2003 4:05 am

With me it usually takes about 7 -8 to make my voice sound better.

knightfly · Post by **knightfly** » Fri May 09, 2003 6:01 pm

OK, so I'm a cheap drunk - on the other hand, even a half-case has been known not to accomplish said task from my wife's point of view... :=)