John Sayers' Recording Studio Design Forum Archive

Hello,

I've recently used Spectrafoo to help identify how my room is influencing what I'm hearing at my mix position. I ran some pink noise as well as other test signals thru some ADAM S3A's and discovered that there's almost a 20db difference between some of the peaks and valleys in the low end. I have a few RealTrap MiniTraps. I experimented with those a bit and they do help some, but I believe I need at least a few more to make a big difference. I'll be getting more soon. I've been cutting some at 165Hz and 220Hz especially on some male vocals that sounded boomy to me. Now, I'm sure that they weren't ever boomy to begin with. Unfortunately, it would seem my room is.

My question is, how many of you are using an EQ to further help flatten your frequency response after you've done all you can with room treatment and speaker positioning?

I remember reading that it's safe to use EQ for this as long as you only use it at around 300Hz or lower. Otherwise, you start introducing some larger negative problems due to phase shifting. Any comments?

If you are using an EQ, especially with nice quality monitors, what kind of EQ are you using? I would guess that if it were analog, ideally you would want to use something like a GML 8200 - something that's super clean and precise. What do think?

I appreciate any info you can offer,
John

Hi John,

Welcome to the forum!

No, you cannot use EQ to flatten your frequency response (except for the very lowest frequencies). Modal peaks and nulls are positionally dependent. You can theoretically EQ for one position, but if you move your head even slightly the whole thing is wrecked. So, unless you want to record and mix with your head in a clamp, EQ is not the solution.

Having said this, however, there is an effect known as "bass lift" that can be fixed with EQ. Bass lift occurs in the lowest frequency range where the wavelengths are large compared to the room dimensions (the pressure zone). At these frequencies the speaker is almost completely in phase with the wall reflections, so the energy is efficiently pumped into the room, resulting in a rising response. This is the same reason why the bass in your car sounds much louder with the windows closed, and why the bass disappears when you pull your headphone ear cups away from your head a little. In fact, in more sophisticated car audio designs the woofers are designed such that their low frequency roll off exactly compensates for the rising bass response of the cabin. Even still, you have to remember that a room is much bigger than the interior of a car. For most normal sized rooms this bass lift effect will not start kicking in until you get below 30Hz. So, for the most part, EQ is useless when it comes to problems with the room acoustics.

Thomas

Hi Thomas,

Thanks for the friendly welcome!

I appreciate your help. I've posted this question on a few forums. The 3 responses I've received so far (including yours), all made by professionals, seem in concurrence. However, I know I've read some magazine articles over the years that have discussed the use of EQ to help straighten out some low end problems. From what you and the others are saying, this is definitely not an effective option. Unless perhaps, as you said, you always kept your head in the exact same place. That's not going to work. I really hope the use of enough MiniTraps eliminates the problem because I don't think I'll be able to rearrange my equipment, speakers, and mix position much differently.

Any thoughts on room treatment options to greatly reduce or eliminate that boominess at 160-220Hz?

Thanks again,
John

Well, let's see what we can come up with. Your room with dimensions, speaker, and listening positions would be very helpful. Posting a drawing is even better.

Thomas

Ok Thomas. That sounds great. I could go over a few measurements, scan a drawing, and email it to you. Would that be ok?

It might take me a day or so.

Thanks a lot,
John

John,

FYI: I replied to your post of the same question on RO. Sorry I'm a bit behind... Basically echoed what Thomas (and others) have already told you.

BTW - I have seen the same magazine articles. And each author usually receives a not so wonderful response from me!

Best regards,

Jeff D. Szymanski
Chief Acoustical Engineer
Auralex Acoustics, Inc.

Hi Jeff,

I just responded to your feedback over at RO. I'm going to try all the acoustic treatment I can to solve my problems. It sounds like that will do the trick.

Thanks again,
John