7 ch eq

[jdm56]

Bass traps are a good option, but I would not a rule out a good EQ. And AudioControl does make some good equalizers. My main gripe with them is they are mostly all analog, with all the noise and phase problems that can go along with doing eq in the analog domain. But still, a 1/3 octave unit could knock down an offending resonance to where it is not a problem. No, it's not a perfect solution, cause like's been said, even 1/3 octave is wider than you really need to kill a resonant peak, but still, the net result could be a lot better than living with the boom.

Another point to consider: bass traps that are effective at 30-40hz are going to be big and expensive! Most that I've seen that have any WAF at all only work down to about 60Hz.

I used to have a Sony TA-E1000ES pre-pro with a built-in 3 band parametric EQ. It was mahhhvelous for killing room boom. It's bands could even be "stacked", giving you up to 36dB of cut (or boost).

[Born2RockU]

IF a Sub-Frequency Problem is what we are talking about......

....I have a NOTCH FILTER for the low-end , provided in my B+K Pre-Amp.

You can designate what area you are having the problem then add or subtract

the needed or unwanted sweep by 24 dB .

[Griffinator]

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On 12/13/2004 8:00:35 PM Born2RockU wrote:

IF a Sub-Frequency Problem is what we are talking about......

....I have a NOTCH FILTER for the low-end , provided in my B+K Pre-Amp.

You can designate what area you are having the problem then add or subtract

the needed or unwanted sweep by 24 dB .

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Not sure why you felt the need to use the big font, but this isn't a simple sweep problem, it's a standing wave. We're not talking about a bump here, we're talking about a near wall of frequency rise, one that a simple eq will not help.

[colterphoto1]

Okay, lets hear it once again. You have a standing wave caused by room acoustics. This is a very common problem. In fact almost any room will exhibit this characteristic to some degree.

NO EQ WILL SOLVE THIS! Take a tally on how many Forum members have given this advice in several different ways.

Please consult Mr. Artto on the Architecture portion of the forum for a calculation of offending frequency(s) and suggested solutions.

Michael

[sfogg]

Room resonances can be treated with EQ. Do a waterfall with and without the EQ and you can see the shorter decay times of the offending resonances... that means EQ is working.

Shawn

[DrWho]

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On 12/14/2004 8:51:28 PM sfogg wrote:

Room resonances can be treated with EQ. Do a waterfall with and without the EQ and you can see the shorter decay times of the offending resonances... that means EQ is working.

Shawn

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This only works with PEAKS in the frequency...

No amount of EQ will affect DIPS in the response. And even with peaks, you can still here the resonation of the room when you try to reduce the output with EQ. The only true way to fix an acoustical problem is to fix the acoustics. When acoustical fixes aren't possible, then EQ is an option, but realize that it's a compromise and only a partial fix.

[sfogg]

"This only works with PEAKS in the frequency..."

True, and if you look at my message I was talking about peaks since I was talking about areas in the bass that ring longer then the rest. A null obviously isn't going to ring. It is the ringing that causes a loss of detail in the system, not the peak itself.

Nulls are also less offending then peaks.

"You can still here the resonation of the room when you try to reduce the output with EQ."

Reducing the energy you feed into a rooms resonance reduces the rooms ringing at that frequency. I've measured this myself in the time domain, it works. It is also very obviously audible when you turn off the eq or not.

"The only true way to fix an acoustical problem is to fix the acoustics."

If your room has parallel walls you are going to have resonances.

Shawn

[DrWho]

I hope I didn't come across as trying to refute what you were saying...I was just trying to clarify when EQ should be used.

As far as room resonances go, reducing the energy causing the resonance does indeed reduce that resonance. However, that resonance still exists and is different from the normal decay rate of other frequencies that aren't resonating. I have not been able to show this with graphs and all that as I do not have the equipment available...

"If your room has parallel walls you are going to have resonances."

Then let us start with rooms that don't have parallel walls

Btw, here's a link to a review for the original EQ in question:

http://www.hometheaterhifi.com/volume_4_1/bijou.html

I personally don't think EQ'ing the surrounds is worth the effort and more concentration should be aimed towards the mains and sub. If you have good measuring equipment or really good ears, then I would say go with a few simple parametric EQ's. A 31 band graphic EQ is very good for EQ'ing the source material (kinda like tone controls) but won't be nearly as effective with room issues.

If you're new to EQ'ing, I would highly suggest finding a unit with a bypass switch (most all of them have one anyway). This way, you make one change at a time and then listen for a bit with the change and then hit the bypass and determine which sounds better. Then change the source material (to a different genre if possible) and determine if the change continues to be positive. Then go onto the next EQ and listen and then repeat the bypass test and then try it again without the original change. EQ'ing is an art and you must teach yourself to ignore the wow factor. The wow factor is a change that sounds good at first, but after a while it shows itself to be a very wrong choice. Also, if you make a small change and don't notice a big difference, then don't bother with the small change.

[mdrums]

Ok the bottom line is your room will have problems until you correct the dimensions of the room, however in a home living space this is usually not applicable or it is cost prohibitive.

Being a professional musician and working in the music industry Berhinger products are at the bottom of pro audio equipment but the Feedback Destroyer used for subs does work very well and the extra hiss it adds to your system will filter out with the crossover to the sub anyway. Graphic EQ's are not the way to go to try and help low frequency problems and you need a parametric style eq and the Berhinger FBD or any other multi channel parametric will do the job. I also recommend trying some bass traps and room acoustic treatments.

[Griffinator]

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On 12/14/2004 11:36:52 PM sfogg wrote:

"This only works with PEAKS in the frequency..."

True, and if you look at my message I was talking about peaks since I was talking about areas in the bass that ring longer then the rest. A null obviously isn't going to ring. It is the ringing that causes a loss of detail in the system, not the peak itself.

Nulls are also less offending then peaks.

"You can still here the resonation of the room when you try to reduce the output with EQ."

Reducing the energy you feed into a rooms resonance reduces the rooms ringing at that frequency. I've measured this myself in the time domain, it works. It is also very obviously audible when you turn off the eq or not.

"The only true way to fix an acoustical problem is to fix the acoustics."

If your room has parallel walls you are going to have resonances.

Shawn

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There are so many misconceptions here it's not even funny.

1) No, you cannot fix a room resonance with an EQ. Why? Because that resonance isn't going to be consistent throughout the room. Need proof? Take a spectrum analyzer around your room. Do your frequency sweeps. I can guarantee you that even two points within two feet of each other will read drastically different frequency response curves.

2) No graphic EQ will ever be precise enough to reduce the energy spikes caused by standing waves. Why? Because no spectrum analyzer is going to read and respond to those energy spikes to a fine enough resolution. 1/3 octave is not enough. 1/6 octave is not enough. Room acoustics do not follow our 12-note equal tempered scale, friend, and if you cut the wrong frequency, you create a whole slew of other problems.

3) Equalizers will always have a negative impact on the sound of the system. Period. Artificially distorting the output signal to compensate for room acoustics is never a good idea - and that's what an EQ does. It distorts the output signal.

4) Parallel walls have far less to do with standing waves than you believe they do. You can have a room that's a completely random polyhedral shape, with no parallels, and if it is not of sufficient size, it will have standing waves of some sort.

Get bass traps. That's the most straightforward, sure solution to a subsonic spike in the room. You want your system to be accurate? Skip the EQ and do it right.

[sfogg]

"There are so many misconceptions here it's not even funny."

I agree.

"1) No, you cannot fix a room resonance with an EQ. Why? Because that resonance isn't going to be consistent throughout the room."

That is incorrect, a resonance is consistent around the room except at nulls.

What causes a resonance? A wave bouncing back and forth within the room. If the wave is bouncing back and forth within the room (ringing) it is hitting many points throughout the room.

"Need proof? Take a spectrum analyzer around your room."

A spectrum analyzer is a *lousy* tool to use to see a *resonance.* You need to look at a time domain measurement using something like ETF or whatever. A resonance stands out on a waterfall chart as having a much longer decay then the rest of the nearby spectrum... again because that room is holding onto that frequency with it bouncing back and forth within the room.

"2) No graphic EQ will ever be precise enough to reduce the energy spikes caused by standing waves"

Agreed, I've said that numerous times.

"Because no spectrum analyzer is going to read and respond to those energy spikes to a fine enough resolution"

A 1/24 octave unit does far better then a 1/3 or 1/6 but it still doesn't show time domain behavior which is what is really need to see resonances.

"3) Equalizers will always have a negative impact on the sound of the system. Period."

BS. Period.

You are welcome to come over and hear my system with and without EQ before making such a statement. Spend some time on a Tact users forum, or a Meridian users forum or a Lexicon users forum and you will see hundreds of posts by many many people saying eq improved the sound of their systems.

http://lexicon.com/products/details.asp?ID=15

http://www.meridian-audio.com/w_paper/Room_Correction_scr.pdf

You will note both systems just about don't care about the amplitude response of the system in setting up their filters. They look at time domain response for setting up their filters and target the specific frequencies that are ringing in the room.

It is certainly possible to screw up a system with EQ, but that doesn't mean eq always screws up a system.

"Get bass traps. That's the most straightforward, sure solution to a subsonic spike in the room. "

Bass traps are far to broad band to just deal with a resonance. They will reduce *some* bass all over the frequency band. And they can't do hardly anything for resonances at very low frequencies as their absorption is almost nothing down there. Even most anechoic chamber chambers will reflect bass below some frequency point. If they can't stop reflections a couple of small bass traps certainly aren't going to be able to. Since the original poster was looking to boost the bass response of his system below 100hz a bass trap is a lousy solution, it won't get it done.

Shawn