Gap behind trap vs. thicker trap?

[Weasel9992]

Originally Posted by DanDan

Like any tool or instrument, results obtained are dependent on technique and operator skill. A rotating boom cannot randomise VLF. However one can move the boom centre to various different carefully chosen locations.
The use of multiple locations or sometimes even multiple microphones is common I believe. I am not sure that rotating booms are often used in the big rooms, I have seen and used them in smaller semi rev rooms. Multiple locations can extend downwards the validity of the spatial average, plus of course the spectrum of useful results. A room can only be certified to a certain frequency, directly related to it's size. That does not mean the room is useless below that frequency. With ingenuity and skill one can get useful results, certainly in comparative tests.

It's great working for GIK, where on any given day Glenn can have me hunting down answers on just about any topic on the planet. Your questions raised some curiosity, so I called RAL and talked to Dave.

Basically Dan was right about everything:

• There are no “official” method for measuring bass traps, but RAL has plenty of guidelines and history which provide a pretty solid framework for reliable testing methodology. In other words, there’s no real reason to doubt the results based on methodology.
• The reverberant chamber itself is diffuse within 1dB at any given certified frequency.
• The boom arm basically just puts the mic in any one of six locations continuously during the 80 decay-cycle testing procedure. Those readings are averaged at the end to give a comprehensive result. In other words, statistically it’s the same as taking the readings from six fixed positions in the room then averaging the results, which takes modal effects out of play with respect to results. This speaks to the implimentation of proper spacial averaging you were talking about.
• RAL is certified down to 100Hz.
• RAL’s testing error range is +/-6% down to 100Hz, and David estimated that it probably would increase to +/-10% by the time you got down to 63Hz, and something between 10-15% at 50Hz..

All of this is borne out in a real-world way by the curves we see on the RAL results our Monster Bass Trap and 244 panel. Given the physics at work and testing methodology employed it's exactly what we'd expect to see.

Hopefully this answers the questions. As Dan said earlier, there's really no reason to doubt the results since good methodology was followed and disciplined testing protocalls were observed. Any questions about procedure or reliablity could easily be addressed to Dave by phone I'm sure.

Frank

[Ethan Winer]

Excellent research and reporting Frank!

--Ethan

[DanDan]

'Dan was right about everything'
Well, my world domination/retirement plan is starting to kick in......
Welcome to the fold, Brother Frank.
Membership will be open to all ye other sinners shortly. Just as soon as I get registered for Charity Status.
THE DD

[Glenn Kuras]

Originally Posted by DanDan

'Dan was right about everything'
Well, my world domination/retirement plan is starting to kick in......
Welcome to the fold, Brother Frank.
Membership will be open to all ye other sinners shortly. Just as soon as I get registered for Charity Status.
THE DD

I just spit up my coffee from laughing so hard. Funny stuff there Dan.

It's great working for GIK, where on any given day Glenn can have me hunting down answers on just about any topic on the planet.

\

Yea you get all the fun stuff!! I get stuck with the challenging stuff, like which brush will I use to clean the office bathroom with. Ahh the fun of owning a company.

[avare]

Thanks Dan and Frank! There are a couple test chambers certified for testing down to 50 Hz, but they are few and far between.

Andre

[Weasel9992]

Originally Posted by Glenn Kuras

I get stuck with the challenging stuff, like which brush will I use to clean the office bathroom with.

Which brush? I've been using your toothbrush...

Frank

[Glenn Kuras]

Originally Posted by avare

Thanks Dan and Frank! There are a couple test chambers certified for testing down to 50 Hz, but they are few and far between.

Andre

Andre,
Can you email me which ones? Might be good to put in my back pocket for the future.