[Jeff Smith]

I have a Lexicon DC-2, and have diffusers and bass traps set up as well as the room allows. I have a SPL meter from Radio Shack, and use the Lexicon pink noise to even the speaker sound levels.


My speakers are set where they have to be due to room constraints, and they can't be moved. However, they don't sound bad now...I'm just trying to tweak the system.


What I want to do now is EQ each speaker. I understand I can get test tones from Avia (which I will buy if needed) and perhaps from AV Essentials (which I have now, but have never used).


I have an Audio Control Bijou, a 6 band EQ (5 + sub) for HT. Its a high quality unit (ie. expensive but well thought of by the mags that reviewed it), specifically designed for HT.


In the past, I had a local audio engineer come out, but I'd like to do it myself, as he mainly does clubs, etc...and he's hard to get up with. And he did mainly what I describe below.


I think the process goes like this for each channel/speaker, but advise me...


1- first get the SPL equal for all speakers in full range, then...

2- have avia send the proper tone for each band the EQ can do.

3- adjust the EQ slide controls so the SPL meter has a constant level for each tone.


Am I right in assuming that even though I only EQ for a specific tone, the EQ also relatively adjusts for tones close to it both higher and lower (ie toward the next band the EQ can adjust)?


Also, do you EQ first, then adjust levels...or the other way around? Or do you go back and forth doing each repeatedly until its right.


Its been a few years, but if I remember, there are certain ranges that are way off, but if I EQ them as well as I can, I'm still better than if I didn't, correct?


Again, I'm not looking for perfection, and have searched the forum, read tons, and just want to improve on what I have.

 

[Ethan Winer]

Jeff,


If that model EQ offers only six bands, you'll probably do better not to use it at all. To EQ a room you need better resolution than that. You also need a high-quality microphone. You also need to average many separate measurements over the entire listening area. If you set an EQ based on only one microphone position, you're likely to make things much worse than had you done nothing. At the minimum you need to use pink noise for mid and high frequencies. Sine wave tones are best for low frequencies, but they're not suitable above around 300 Hz.


--Ethan

 

[speco2003]

SIA Smaart Live. Download the trial version get a flat response mi. It will help you set levels with pink noise then show you a transfer function of each speaker so you can decide what EQ if any you want to appply. The Best EQ is no EQ.

 

[BGLeduc]

Jeff,


I too have a Bijou, and more or less followed your process to dial it using discrete test tones.


For the bass frequencies, I used Bass Mekanix V, which has tones in 1/2 hertz increments, and used a Infinity RABOS meter to take readings. Above 99 hz, I used the Sheffield "My CD" test tones.


You don't need to tweak channel levels before EQ'ing, since they will change after everything is dialed in.


For those that don't know, the Bijou has 1/6th Octave control for the sub from 80 Hz down, and 1/3 octave from 80 to 800 Hz for the front three. There are also selected frequencies for the rears. I think Jeff meant to say 6 Channel, not 6 band.


I would not trade it for anything, other than an Audio Control Diva, perhaps!

Quote:

If you set an EQ based on only one microphone position, you're likely to make things much worse than had you done nothing.

I disagree completely.


The choice is average, in which case no one will have correct FR but several locations may or may nor be improved, or use a single mic position, where that one spot will have correct FR. You can't have it both ways.


I EQ my rig for the "sweet spot", since I am normally the only one that gives a hoot about the sound in my room.


If you have other friends or family members that are fussy about sound, go ahead and average, just don't expect your prime listenning position to be optimal. Bass response will vary hugely from one place to the next. You can only get it right at one single location.

 

[speco2003]

As far as Mic placement goes in your home theatre room 1 or 2 locations is fine. When we EQ a concert system in an areana we look at several locations. On axis Off axis lobes from other parts of the system. Your typical Home theatre room is not big enough to warrent this.

 

[Ethan Winer]

BG,


> You can only get it right at one single location.

 

[BGLeduc]

Ethan, I do agree with what you are saying (its hard to argue with physics), however, I feel that large improvements can be made with the gear that is at Jeff's (and my) disposal.


Obviously, EQ can't do anything with severe nulls, and speaker/listener placement must be altered to move the nulls to frequencies that are less offensive. Put EQ can do good things with peaks.


Ideally, a parametric EQ with an infinite number of bands would be even better, but good subjective performance can be had with 1/6 octave (or better) frequency centers, if care is taken in the measurement/adjustment process.


For those that lack the means to have a room engineered for good sound, I think EQ is an appropriate approach to take. While I am pleased with what I am able to do with the Bijou, I thing a device like a Behringer Feedback Destroyer would yield much better bang for the buck in the region below say 100 hz.


Looking at your graph, the big dip at 80 hz would be likely a room mode that would need to be addressed with speaker/listener placement. Would you agree?


The higher frequency stuff, particularly the dive at 120 Hz seems pretty severe. Assuming that one's main speakers were handling the work at that frequency, I would think that you would have several drivers at different locations in the room putting out energy at that frequency, which in theory would tend to help smooth those dips. Out of curiosity, how many speakers were playing that produced that huge hole?


BGL

 

[Ethan Winer]

BG,


> EQ can do good things with peaks. For those that lack the means to have a room engineered for good sound, I think EQ is an appropriate approach to take. Looking at your graph, the big dip at 80 hz would be likely a room mode that would need to be addressed with speaker/listener placement. Would you agree?

 

[BruceD]

Ethan,
Quote:

I doubt most HT owners will have much success doing this by ear using an EQ and a test CD.

I think you might be surprised what people have accomplished with regards to bass frequency EQ.


In the last 5 years I have been participating in these forums I have seem more than 100 HT owners discuss their success at taming bass modal peaks with the same methodologies discussed by Terry. This may not be most owners, but certainly a good cross section of people who participate here.


They do it with very capable (24 individual filters, 1/60th octave frequency resolution, 1/60th octave "Q" or bandwidth resolution) and inexpensive parametric EQs ($100)

 

[speco2003]

I suggest you guys click on this link then look at the Home theatre paper
http://www.siasoft.com/support/casestudies.shtml

 

[Ethan Winer]

Speco,


> I suggest you guys click on this link

 

[Ethan Winer]

Bruce,


> you might be surprised what people have accomplished with regards to bass frequency EQ.

 

[Az Barber]

I'm no expert, but the few rooms I've been involved in setting up took both room treatments and EQ.


As long as it's right, why does anyone care how you got there?

 

[BruceD]

This isn't one method against the other, but it is clear that if low frequency sound quality improvement/$$ is important, parametric EQ works.


We all wish we could acoustically treat our rooms to the max, many times this just isn't possible. Where WAF and low $$ are concerned, parametric EQ makes perfect sense.

 

[speco2003]

One thing EQ can do is introduce phase shift into the system so if you really want to get down and dirty critical listening, then you need a really good parametric EQ. And as we always say the best eq is the least eq. This is a great thread going here guys. You should all give smaart a try on your home theatres its a great tool. I dont work for them but have used them and the Meyer Sound Sim System for years in arena rigs and its just fun to see what your HT is like.




Quote:

Originally posted by Az Barber I'm no expert, but the few rooms I've been involved in setting up took both room treatments and EQ. As long as it's right, why does anyone care how you got there?

 

[BruceD]

While I haven't used SIA's Smaart software, a much less expensive software package ($150 vs. SIA's $700+) alternative that offers sophisticated MLS-based measurements is the ETF5 software package.


This acoustic measurement system has been a valuable addition to my sound system over the last 5 years.