Hi all,
Is it possible to overshoot a problem frequency using pannel bass traps? In the attached diagram (if it works) you can see the basic design of the room. All traps are 4 in. 703 and are placed about 4 in. off the walls. The corners are floor to ceiling and the walls are centered (roughly 9 foot ceiling).

My problem is when the kick and bass guitar are nice and thick at the mixing position, they are way too strong on other systems. The highs and mids are translating well (Dynaudio monitors).

Should I address this issue with more 4 in. bass traps or should i use two or even one inch (mid?)-low frequency absorbsion?

thanks for the advice,
Paul Crawford

setup.bmp (134 Kb, 17 downloads)

You can't really overtrap a room in the bass frequencies. More bass trapping actually increases the bass response of the room, or makes it more accurate. You can however, over-absorb in the higher regions; too much foam, carpet, etc..this doesn't seem to be your issue. You can however have the high to low balances off so that you like the low end at mix position, yet are tending to not add enough mids-highs. That could be..

also if there is no mid-high absorbtion happening, and the room is supporting those areas, you may perceive that the high end is enough..or too much even and there you go..

Or, the simple answer that nobody wants to hear is you're not making a balanced mix, perhaps mixing the track like a live band PA system mix, one that won't translate well. I've done that one myself a few times.

Kel,
I recognize that the frequency ratio of the entire spectrum may be skewed. Frequency response of the room showed strong nulls from 80 to 100 Hz roughly from 90 db down to 60 db and a null at 142 Hz roughly from 90 to 60 db. If these (especially the 142 Hz) affect the translation based boominess (my overcompensation for the room), will the depth of additional bass traps help me focus on these frequencies? Which leads back to the original delima...more 4 inch or should I aim for 2 or 1 inch based 703?

Thanks
Paul Crawford

you'd want to go as aggressive as possible with the bass trapping. Nulls and modes will even out. Remember that the surface of these bass traps is most likely enough to handle the little required in mid-high absorbtion. Monitor positioning might affect things as well. the distance between floor and ceiling of the woofer in the monitors has some affect...as does the position from the wall. the space looks narrow but there are no dimensions listed.

Let me tell you that judging from your picture you have just minimum amount of broadband absorption. After adding as many as you currently have you may think of real bass traps, which are basically the same broadband absorbers covered with material that reflects high frequencies. Another thing to point out is that your side panels are not positioned right, they should be somewhere in the middle of listening position and speakers. Adding absorption will make your room a lot better, but I also agree with Kel about "not making a balanced mix" thing.
You don't need anything less than 4", if you want to affect sub 100hz frequencies you better do 6-8" & spaced from the wall as far as possible & preferably made of 705.

thanks all...

I have taken the wall panels (everything that was not in the corners) and placed them along the ceiling to wall junctions. These junctions covered all places that can be covered with the layout of the room (windows etc.). I also took some auralex that I had above my mix position and placed it at the first reflection points. All I will have room for now is to make a cloud to put above the mix position. Now all there is to do is see if this made any change. I also moved a book-shelf to the back wall perhaps for diffusion.

Also just for the record, the drawing is not exact by far. The first reflection auralex is placed correctly between the speakers and the listening position.

Thanks for all of the advice. I will see if this arrangement halps some.

If not...I could always build some super-chunk traps...sigh...

Paul Crawford

If you can go for it(budget) make chunks instead of straddling the corners. It goes lower that straddling.
How are you checking the 30db nulls? Nulls in a plot graph could possibly be various peaks cancelling out.