Can you suggest ways to flatten my response curve?

jrlouie

I've always had problems with my center channel. So I ran some tests and plotted the output. Here are the corrected values. You'll see one spot that almost jumps 20dB!
Any inexpensive suggestions as to how to tame this? The center is on top of the TV, brick wall behind it, windows with vertical blinds on one side, no wall on the other side, and drywall behind the couch. The couch is about 6 inches away from the wall, can't really spare any more. I have a very small apartment, so no real way to reorg the furniture.
I only had the correction factors for up to 250Hz, so I only plotted to there. But I think we can illustrate issues, as is.

steveinaz

+/- 8dB is not that bad for "in room" response actually. Thats really where you are in reference to your 82dB baseline. Sure, you'd like to able to smooth out the dip @ 100Hz, but it's easier said than done in a smaller room. The 100Hz area (I would think) would be more the domain of your Lsi15's; maybe experiment with moving them forward/backward, maybe mess with toe-in a bit...

I don't think messing with the center is going to do anything at a 100Hz.

jrlouie

Oh. Well, I completely turned off my mains, and actually all the power to all the other speakers. So that response curve is strictly the center channel.
Don't know if that makes a diff or not.

unc2701

Wait- that's just your center channel response? For the range you show, that's not going to give you issues with the kind of things that are going to be comming out of the center.

PolkThug

You could use a BFD to tame the peaks, then you just bump the center volume up a little.

jrlouie

Hmm.

BrentMcGhee

Man... this is bringing back some bad memories... last year i spent about 2 months trying to flatten the response of my speakers... i have to say, i think the only thing i managed to do was get very very stressed and anoyed. I ended up not being able to fix most of the issues.

McLoki

I assume that is with your sub running. If so, get a BFD to flatten your sub response level and if you can play with your crossover levels (60hz, 80hz, 100hz, etc.) in your AVR until you get the line you want.

If that is not with a sub - damn you get good bass responce from your center channel (I assume set to large) You could do some research on DIY bass traps. That will help your room (if it is overly bright/reflective) but the wife appeal may be low. (just to warn you) They are cheap to make though and may be worth the test if you are handy.

Michael

jrlouie

Yeah, actually I don't even have a sub on this rig so that's without a sub. I'm waiting for my 20-39PCi to show up I did set the center to large just specifically to run this test.
I have a primary concern of the big dip right at 100Hz. Man, while listening to the test tones, going from 80Hz or 125Hz towards 100Hz, it's like you almost can't hear the 100Hz tone in comparison. I just wonder if a significant portion of dialogue hits around that 100Hz area and that's why I often have problems with dialogue.
I don't know

jmierzur

There are changes you can try to find the best response from your speakers. You will be required to make changes to the locations of your listening position and/or speaker locations.

From looking at the picture of the center speaker location, I could not tell if the monitor the speaker is resting on is at the front of the audio stand. If not, try moving the monitor forward to the front of the stand. This would move the speaker away from the rear wall.

You could also try placing the center speaker on the top shelf of the audio stand. Angle the speaker up so it is pointed toward your listening position. I would start with the speaker at the front of the stand. You may also want to try it with different depths from the front.

Regardless of the center speaker location trials, I would recommend moving the listening position away from the rear wall. A good starting point would be 1/5 or 1/7 the room length away from the wall.

To further enhance your listening pleasure, try moving the L+R speakers away from the rear wall and beyond the front of the audio stand. As mentioned above, a good starting point would be 1/5 or 1/7 the room length away from the wall.

There is no right or wrong solution to get the best sound from your room. There are many methodologies of room setup available on the internet. Reading these may give you further ideas as to what may work for your situation.

It will take plenty of repositioning and measuring in order to find the solution that yields the most even overall response. Remember to record the locations of the listening position and speakers after each frequency measurement.

jrlouie

Well, I've found for my scenario, it is all about placement. I have not found my best possible scenario, but readings on the SPL meter flatten out drastically if I take the reading from around 1/4th the length of the room from the back wall. Move the meter back to within 2 feet of the back wall (where the couch is), and there's a major null in the 100 Hz range and a boost in the 125 Hz range, among others.
I have not been able to effect the readings by moving the center channel closer or further from the wall behind it. I regularly sits about 2 feet from the wall, but further or closer didn't seem to have much effect.
It's all about where the couch is. Bummer part is that my place is so small, I don't think I have choices about its placement.

jrlouie

Just wanted to note that I found something else out interesting. I remembered that my Lsi15's response curves were very flat, and began thinking about how they were positioned. So just for the heck of it, I set the LsiC on its end, next to the TV, which ultimately is very close to and similarly positioned to the Lsi15. What do you know, the response flattened out dramatically.
Almost makes me feel like part of my problem is the acoustics of setting it on the TV. Vibrations. But, I remember the response wasn't very flat when I set it on the shelf below, so I don't know.

scottnbnj

way to go! how does it sound in the new position on stuff you had problems with before?

it might be that the new position breaks up reflections off of the front wall. maybe treatments on the front wall to the sides or directly behind the center could do the same thing as the new placement.

the google below or something like it might help:

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=RNWE,RNWE:2005-03,RNWE:en&q=100hz+wavelength+treatment+thickness

the first article has a corner trap idea that should be easy enough to make look like it belongs in the room and will also give you a start in what to look for in treatment thickness for 100hz waves that travel at an angle through the treatment (wall treatments for center above).

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