Can/should anything be done to change this room response?

Big Red Machine · « **on:** 31 Aug 2007, 02:41 pm »

I ran 4 manual sweeps last night with the RS meter to see what the room really looked like versus what it sounded like.

Test set up:

- tripod mounted RS analog meter about 1 foot in front of my head
- CDP to amp direct, then to speakers, no preamp
- volume set to approx 85 db at 1000 hz first and left that way
- only the amp went on and off between set ups, not the CDP
- glued on absorptions were left in place at first reflections on side wall, ceiling, and behind seating
- the best I could do is read to the nearest 0.5 db
- assumption the meter is as accurate as it can be
- note on high frequencies - slightest movement of my head would change the way sound bounced to the meter and change the level response - so I tried to sit very still and not move my head for consistency

I ran 4 plots because I was interested in whether the bass traps were actually trapping any bass or maybe moreso trapping higher frequencies.

I also ran them with and w/o traps with all silver IC's and SC's versus all copper IC's and SC's from the same companies for each metal type (I was curious to know if it would plot out differently for the 'other' thread.)

Besides the room dips, it looks like the traps may slightly smooth out the upper versus lower frequencies.

Important observation: the sound of the trapped room is more quiet (less reflections) and even though it has laser voice imaging in the center, the soundstage is wider, taller, and deeper without the traps. I personally want them in though as the reflections and "brightness" is something I can't live with, even given the soundstage benefits w/o the traps.

So is there any expert advice as to some things to try to:

- smooth out the response
- get a wider, deeper soundstage without a headache from the brightness?

zybar · « **Reply #1 on:** 31 Aug 2007, 02:46 pm »

Pete,

How does the midrange sound?

Looks like you have a HUGE and WIDE dip between around 1200Hz to around 5000Hz.

George

Big Red Machine · « **Reply #2 on:** 31 Aug 2007, 02:55 pm »

Quote from: Marbles on 31 Aug 2007, 02:47 pm

The Radio Shack SPL meter is not as accurate as it should be, you should take the following into consideration when plotting your curve.

http://www.subwoofer-builder.com/SPL-corrections.htm

I did and I forgot to mention I did the corrections to the raw data before plotting.

Big Red Machine · « **Reply #3 on:** 31 Aug 2007, 02:59 pm »

Quote from: zybar on 31 Aug 2007, 02:46 pm

Pete,

How does the midrange sound?

Looks like you have a HUGE and WIDE dip between around 1200Hz to around 5000Hz.

George

The mid is pretty darn good. Even carusoracer commented on how good they were during his visit. But yeah, that canyon bothers me.

I will tell you this though, after 25 years of 2 stroke RC boat racing, my 200 to 400 hz region is very sensitive - in a bad way. Makes my ears buzz.

Perhaps the room is over-absorbed.

bpape · « **Reply #4 on:** 31 Aug 2007, 03:04 pm »

Not to be a stick in the mud but if you really want to see what's happening at your seating position, the mic needs to be where your head is. That either meand a boom stand or move the seating back so you can get the tripod where it needs to be. I wouldn't put too much stock in what you're seeing until you do that.

I'll try to go back and look at the pics of the room and see what all the treatments you have are and where they are.

I'd be trying to fix the dip around 200ish. The large dip up higher is puzzling since if it was a room overdamping issue, it would continue to be low above that - but it's not. Do you have the OXO for those? Honestly, it looks more like a speaker response issue to me.

I'd also be very interested in seeing any waterfall plots of the measurements if you have ETF or Room EQ Wizard.

Bryan

Big Red Machine · « **Reply #5 on:** 31 Aug 2007, 03:13 pm »

I can do the Room EQ this weekend.

I figured if I had to be in the room and read the meter, then if I put the meter at my head location, then I have to be an invisible blob right behind the seat or beside it and that affects the outcome as well, correct?

I have added more bass traps to the between speakers and rack and one horizontal behind my chair on the floor at 45 degrees. I need to take a photo.

bpape · « **Reply #6 on:** 31 Aug 2007, 03:17 pm »

If you use Room EQ Wizard, you'll be in the room but not where the mic is. The PC will 'read the meter' and store for you. This is in The Sanctum, correct?

Bryan

Big Red Machine · « **Reply #7 on:** 31 Aug 2007, 03:24 pm »

Aural Enlightenment 2 channel - http://alhull.com/room7/

I thought you meant to enter the data into RoomEQ. I can't run it with a PC and mic because I don't have a mic and have never done it.

zybar · « **Reply #8 on:** 31 Aug 2007, 03:26 pm »

Quote from: bpape on 31 Aug 2007, 03:04 pm

Not to be a stick in the mud but if you really want to see what's happening at your seating position, the mic needs to be where your head is. That either meand a boom stand or move the seating back so you can get the tripod where it needs to be. I wouldn't put too much stock in what you're seeing until you do that.

I'll try to go back and look at the pics of the room and see what all the treatments you have are and where they are.

I'd be trying to fix the dip around 200ish. The large dip up higher is puzzling since if it was a room overdamping issue, it would continue to be low above that - but it's not. Do you have the OXO for those? Honestly, it looks more like a speaker response issue to me.

I'd also be very interested in seeing any waterfall plots of the measurements if you have ETF or Room EQ Wizard.

Bryan

Bryan,

It isn't the speakers.

I had the HT3's for over two years and used it with the TacT 2.2x preamp for room correction.

NEVER did I ever see that type of suckout with my speakers in two different rooms and houses.

All of my measurements where done with my mic on a boom, right where my head would be.

George

bpape · « **Reply #9 on:** 31 Aug 2007, 03:33 pm »

Yup - after I posted I saw the speakers and figured that wasn't it. Still not sure what the deal is just up that high but then coming back. I originally thought this was the V-60's and we had a combination of xover setting and a possible resonance in the back of the V causing some cancellations.

Pete.

You just use the Radio Shack meter as the mic. It has a line out on it.

Bryan

Big Red Machine · « **Reply #10 on:** 1 Sep 2007, 07:05 pm »

Sat to the side and re-ran the sweeps. Some strange drop outs which make me question the validity of the run. Unable to use Room EQ because it says not to use the mic input and I do not have a USB adaptor.

Big Red Machine · « **Reply #11 on:** 1 Sep 2007, 11:27 pm »

Room modes around 200 hz and multiples of that - 800, 3200 hz. Look like I should rotate my room 90 degrees an try the narrow wall versus the wider wall.

8thnerve · « **Reply #12 on:** 18 Sep 2007, 04:44 pm »

Looks like a pretty typical room response with lots of high frequency loss:

http://eighthnerve.com/methodology.html

Big Red Machine · « **Reply #13 on:** 18 Sep 2007, 07:01 pm »

Because it is overtreated?

95bcwh · « **Reply #14 on:** 18 Sep 2007, 08:14 pm »

Too much foams which absorb mainly the mid to high frequency?????

Quote from: Big Red Machine on 18 Sep 2007, 07:01 pm

Because it is overtreated?

bpape · « **Reply #15 on:** 18 Sep 2007, 08:18 pm »

Which compensations for the Rat Shack meter?

Best set of compensation I've seen:

http://www.hometheatershack.com/forums/spl-meters-mics-calibration/361-radio-shack-spl-meter-correction-values-all-new-cal-files-published.html#post15211

Those meters are OK for comparison purposes, finding general trends, etc. but are really off in the high end. I'd not trust one above 500Hz. I suggested using it as a quick and dirty for 20-300Hz.

Bryan

8thnerve · « **Reply #16 on:** 19 Sep 2007, 04:07 pm »

Quote from: Big Red Machine on 18 Sep 2007, 07:01 pm

Because it is overtreated?

Overtreated with exposed absorption and less than ideal materials. Also, distortion will cancel some high frequency information out. You've put absorption in the corners, and I applaud you for that, but you need a reflective layer to keep the sound coming from the corner from getting back into the room. Build a reflective panel (wood, drywall, whatever, just as non-resonant as possible, you don't want to introduce more problems...) and place it across the corner with about an inch gap between the panel and the side walls on each side. You'll also do better with fiberglass than foam, but you'll still hear a big difference. One way to do it an make it nice is to go to Home Depot and get those cardboard cement molds used for cementing posts into the ground. They are circular in shape, so you can just cut it into four pieces and you'll have a nice curved, not very resonant panel to place in front of that foam in the corners. If that works, think about how to address the horizontal corner at the ceiling as well.

Ethan Winer · « **Reply #17 on:** 20 Sep 2007, 03:36 pm »

Quote from: bpape on 18 Sep 2007, 08:18 pm

Which compensations for the Rat Shack meter?

Just to be clear, no matter what "compensation" you apply, the Radio Shack SPL meter falls off so severely that there will always be a roll-off.

--Ethan

Big Red Machine · « **Reply #18 on:** 20 Sep 2007, 05:09 pm »

I'll take some photos tonight and post. I have OC703 bass traps in all the corners, but only from the floor up to 4' high. All the first reflections have Auralex on them and the corners themselves (behind the other traps) from floor to ceiling have "foam" bass traps. I had considered extending the OC703 traps to the ceiling in the corners but perhaps the panels would do the trick directly over the foam. The OC703 is 6" thick in each trap.

8thnerve · « **Reply #19 on:** 20 Sep 2007, 05:27 pm »

Quote from: Big Red Machine on 20 Sep 2007, 05:09 pm

I'll take some photos tonight and post. I have OC703 bass traps in all the corners, but only from the floor up to 4' high. All the first reflections have Auralex on them and the corners themselves (behind the other traps) from floor to ceiling have "foam" bass traps. I had considered extending the OC703 traps to the ceiling in the corners but perhaps the panels would do the trick directly over the foam. The OC703 is 6" thick in each trap.

More important than the material is the reflective panel in front.