My Measurements Continued

[thewire]

This is a continuation of this thread. Note there is no receiver, and subwoofers do not have internal crossover, gain, phase, etc. Measurements will be done directly to the amplifiers, or done to with a CD in an XA2 until furthur notice. Thank you for your patience.

http://www.hometheatershack.com/foru...lp-please.html

Since I have:

1. Dug out stone in dirt on the other side of my screen wall
   
2. Filled the ceiling in the front of the room (1/3 room) with R19 Quiet Batt
   
3. Covered the front of my stage with 10 2'X2'X1.35" concrete tiles.
   
4. Placed my subwoofers on my stage
   
5. Removed insulation and covering from the Helmholtz resonators, moved it elsewhere inside the foundation.
   
6. Moved rear row seating forward
   
7. Added second door seal to threashold on my HT entrance door
   
8. Replaced center channel stand with 20 of the 2'X2'X1/25" tiles, two subdudes, foam, and a 2'X2'X2" acoustic panel in front.
   
9. Filled front stage with more insulation
   
10. Reinforced ceiling joist with furring strips short circuited between steel ceiling groves
    
11. Filled all ceiling tiles with fiberglass, added backpanels, taped them with masking tape and electrical tape
    

Let me know if you would like me to post those graphs.

Here are some measurements I have taken of the center location between the front row. More to follow.

RT60 mains (ignore non relevant frequencies)



ETC mains



Mains FR (I extended this to 3K)



Skip this one Same signal to subwoofer, did not move mic



Skip this one also Correct SPL subwoofer did not move mic



Actual SPL subwoofer and mains (mic pointing up for subwoofer)



Waterfall front row centered



There is one filter at 50Hz for the subwoofer using the BFD not calibrated for several weeks.

[thewire]

When I began to measure this time I noticed that the mic had feedback while I was positioning it. I changed my playback config in my soundcard with the Windows Mixer from 0 setting to mute and this fixed this issue. These measurements were done with my laptop battery. The extra theashold (dowel rods + second weather stripping) was removed after an incedent involving the door being stuck for more than 4 minutes, of which took myself 30 seconds to open, while 1/3 of the second weather stripping was intstalled. Therefore that has been removed and these measurements are with the orignal weather stripping. Instead we are replacing the 1/2" with 1" (I think) and adding thin tubbing under it. I will post those later. I added black fabric over the concrete in front of the stage minutes after posting the first graph. Does anyone have any idea why my left channel ETC now looks very flat and then has a spike furthur down. My laptop may have been trying to access my modem, or there might have been some noise in the kitchen but I'm not 100% sure it would pick up noise in the kitchen, and I did not hear noise during the measurements. If it trys to access the modem and I hear it, I remeasure.

ETC2



Sub center2



Mains and sub Actual SPL centered2



RT60 2



All seats measured subwoofers

[thewire]

We added a Poly Foam Caulk Saver 5/8" diameter. The seal is now better, and door stays tighter however the door opens with ease. I watched the ending to Matrix Revolutions and I could hear the cover to my CRT projector vibating inside the hush box, so I need to fix that. There is a screw missing that broke so it is only held half in place shut. I will measure before and after I fix that. I will also caulk the access panel to the wall inside the equipment room and see if that actually shows up in a measurement also.

[thewire]

Back left seat before door seal



Back left seat after door seal



Mic centered front row after door seal see above for previous



Left seat before door seal



Left seat after door seal



All seats measured after door seal see above for before



SPL not calibrated.

[thewire]

After laying a section of plywood and cardboard layers across half of my equipment closet wall covered with a blanket, held in place with shelving. No equalization applied yet. There was nothing worth mentioning about the previous changes.

left



left2




right2



right



left back



right back



Looks much better.

[thewire]

I finished adding some ceramic pillars to the back corners of the room that I was asked to add for decoration. I filled those with insualtion and used some caulk rope for the decor on them. I also had to stuff some paper towels inside the small statues when I discovered they were weighted with pebbles. I put a dozen or so more books on a shelf in the back that was empty as well. I messed around with some equalization adding some very small cuts in other areas. Seeing as the peak around 80Hz - 90Hz shows on my RTA measurements I added a cut there. The headroom went from 9.9dB to 13.5dB headroom, but not sure how that relates after the crossover. I will see how that effected the mains+sub response soon. The cut at 30Hz was tricky as more cut would increase ringing, but I was not able to reduce it before with equalization as I have now. I'm happy that the seat I sit it in is now the best looking seat. I used some scenes at the begining of Saving Private Ryan to compare results. We accidently spent the weekend without any equalization at all, since I had forgot to switch the imput and outputs. I thought that Get Smart seemed to have an unusually large amount of bass. Another mistake I found was that after filling some areas under my speaker stands with insulation, and the newer addition of the center channel that those two speakers were out of phase again. I can't say the difference is very obvious unless I actually move around however. I will have to check the mains again. I have goten pretty used to the idea that changing one thing means I have to go back adjust everything again, so not a big deal. Since the changes the right channel speaker is now 1dB louder so now all my speakers are at -11 except that one at -10, and the subwoofer, which I have not checked yet but would be from a -2 or 0 setting to get 75dB. I have over ten guest this weekend so I am having to work as fast as I can. To me the left corner still sounds a little boomy. This is where adding absorption reduces the 60Hz dip. The dip was always worse with the subwoofer at the right side of the room so I'm a bit confussed. Standing right next to the subwoofer in the left corner I hear the problem comming right from the subwoofer. Standing over the other ones I can't even localize them. Sitting in the right seats sounded better before equalization. I will figure this out eventually but think it has to do with bass build up. Here are the newer results. Filters are:

30.27Hz -2.5 .200
47.98Hz -7.5 .333
73.46Hz -2.5 .125
87.30Hz -4.5 .200

Front row after recent equalization




Right seat after recent equalization



Left2 seat after recent equalization

[thewire]

It has been a very difficult week. First I ran into into some issues with my front left corner/wall and right front wall that had flanking issues related to the subs being on the stage. I then moved a layer of wood and concrete tiles under my subwoofers and moved them away from the front wall so the ports could breath. Then I started having trouble with my door. It turns out someone has loosened my HT entrance door to make it easier for guest to open or shut the door without having to push it or pull it shut. They failed to tell me about and the hard work and calibration was incorrect. Now I have more problems to consider because I can't simply setup my room and move adjust the door each time we have company, and I don't want them to hear anything less than good sound. Fortunitly nobody sat in the back row, and the worst they heard was the rooms 30Hz ringing as a result. They did not have to listen to the door banging around as I did in the back row. I have decided to try leaving the door open. This is really bad I know. I created a DIY door trap that I tested and it or similar would in fact reduce the problems caused by my door, however I do not know if it would be allowed. I obviously can't lay a trap against the door each time while watching movies which is even worse than the door poping out, or needing to be pulled tightly shut. It is an 85 dollar door and I don't think I'm allowed to put holes in. This is why I will not even use it then so it is a total waste. I will not be able to enjoy movies while folks are here to visit and they are not watching it. I am almost certain they could hear it on the other side of the house while sleeping also. Now the results of the left to right are all messed up, but the decay is much improved. I took apart my new door trap and moved the treatments into my upper right and left corners in the front of the room.

Here are the new measurements of the front row with filters applied since trying to get as close as a result possible. If I wanted I could apply equalization to the left2 seat (where I sit) alone, and it would look about as good as it gets. There still is some slight hope that more room treatments may improve things, and that the door could be done correctly. I will need to see what this sounds like still so I'm not sure it is going to work out.

filters



left



left2



right2



right



all measured

[thewire]

They say that they no nothing about the door being adjusted. The screws on the strike plate are loose. I will try adjusting it back and see if I can improve the response by subwoofer postioning then. Think I better use some 2" screws.

[Andysu]

thewire

Let me see if I follow you correctly? What you’ve done is to plug the lead audio output from (computer pc) directly into the power amplifier which has (no crossover) correct? Then just run REW as normal correct?

Well that’s what I’ve just tired I’m using JBL 4645 diy sub professional with Alesis RA300 bridge 300 watts. Its primary use is for LFE.1 track discrete sub bass information, while a secondary sub bass is used to augment the bass from LCRS and give the illusion it’s a BIG SOUND, but that’s not important now.

So rather than plugging the leads into the AUX on my AVR Kenwood KRF-X9050D THX select, where I’d have to select stereo or Dolby stereo mode and select (sw-re-mix) which basically the subwoofer channel that can be used for mono stereo Dolby stereo or Dolby digital / dts.

The bass is slightly filtered I think the cut-off range is 80Hz.

So I’ve tried your route without using any filters what so ever, now all I have to do is pass the signal into my audio mixer and send it over to the BFQ2496 do another (frequency sweep in bypass mode) then compare the frequency graphs and see if I can’t achieve a slightly better EQ flat response.

Cheers for that it of information.

[thewire]

Glad to help. Also a side effect to measuring without the crossover is that you learn every aspect of the speaker postioning which will also apply to other speakers if you are treating the room. Here is an example of what I know how my response would be effected by placing absorption. Blue is with some blankets in my right corner and purple is without. There is four measurements for each of the front row seating again. Same for the other speakers only relative to speaker positioning the effected frequency is different. Where I have speakers and equalization positioned is a comprimise to these areas being not fully treated proven by my testing while moving various absorption around the room.

[thewire]

I have an 89db target at -20dB FS using the THX optimizer with my subwoofers set to -1. I can go as low as -12 for the level. If I want to be at 86dB or 85dB do I use more cuts, or turn down the subwoofer level?

There is a cut at 50Hz and a small boost at 60Hz.



Edit: Sorry nevermind. I turned on dialogue enhancement accedently. It should be 85dB again. As an added note, it looks like the dips at 100Hz tell me my first reflection points need more thickness also.

[Andysu]

I honestly don’t know how to read or interpret this I see the words with arrows pointing at different parts of the frequency spectrum. If my dad was looking at this he’ll probably say (what’s this got to do with painting a room?)

Is there another way or several ways you can translate this to layman's terms.

Thanks.

[thewire]

Andysu wrote:

I honestly don’t know how to read or interpret this I see the words with arrows pointing at different parts of the frequency spectrum. If my dad was looking at this he’ll probably say (what’s this got to do with painting a room?)

Is there another way or several ways you can translate this to layman's terms.

Thanks.

Yes it's pretty simple actually. Please note that I am trying to make the room as perfect as possible, and most of this is way beyond typical.

1. Door

This is where I am going to place a 4" 24" X 48" panel and a 24" X 24" 4" panel. I'm ordering that right now. This will make the 25Hz bump in the measurements of the right side of the room, look flat. The ringing on the measurement of all the waterfalls (the things that look like fingers) will also be gone. It is a very very small difference, but the back row has lots of ringing there, and will benifit greatly. The door resonates inside (like a drum makes noise) of it, and moves with the pressure in the room changing the way sound energy is lost. There is caulk saver under my weather stripping. It is a door designed to be outside. There was some problems getting installed but the builder finally understood what I wanted, and changed the framing and ordered the steel door. There is about 2 tubes of caulk around the frame inside of the walls.

Summary - Door moves and rattles - Place something, anything in fact on the door and it stops.

2. Front corners

I have this area pretty well full of treatments. There is Roxul 60 in the corners covered with burlap and forced very tightly between two furring strips that are screwed and caulked to the walls. The bottom of the front corners are pink (owens corning insulation) inside of plywood. This is part of the stage area. The top of the corner is filled with more pink and Quiet Batt (acoustical cotton) that is above ceiling tiles. I did not cover enough surface area in my room at these corners as I left room for decor and speakers. As a result there is small dips at the 35Hz area. I placed a GIK pillar trap in the right corner and you can see how the 40Hz area is improved a couple decibals. There will be a matching one on the other front corner.

Summary - Repsonse also changes when I add absorption to this area.

3. Rear wall and rear corners

The 50Hz peak in my room is caused by length of my room or the back wall. Placing 4' thick 6' high stack of insulation on the back wall, or similar, and the peak at 50Hz would be gone. I am not allowed to build a false wall there and fill it with insulation. I have instead placed 2 GIK 244 traps centered on the back wall for absorption, and placed book shelves for diffusion. I equalize the rest. This also effects other frequencies a little.

Similarly to front corners, 60Hz is a dip in my response without having enough insluation in the ceiling area back there, and the corners.

Summary - Rear of the room does not have enough trapping. It has a combination of trapping and diffussion according to my taste. The corners and ceiling are not done.

3. Side walls

These do not have absorption placed inside the room. Notice how sitting furthur from them towards the center of the room causes these frequencies to combine and become louder. Not much louder so it will not need much treatments. I think that some GIK 242's should do fine. Three should do it. Again this is all just my room, and results for other rooms and those treatments will be different.

Summary - Not that impotant but I know about it and would like to conform to THX guidelines by treating the area bellow ear level at the very least.

4. Floor

This is fixed by changing the speaker distance on my mains and moving them. It's not a big deal.


What I noticed and pointed out is that the response of running the subwoofer without a crossover, is that the result behaves much like it does when positioning my mains. I more recently found that the 100Hz area is mostly not improved by adding absorption to the corners. Because this area improved when I added 2" panels for my main speakers, and moving the subwoofers side to side changes this dip, I think that is the same issue. My solution would be to add more absorption there. Placing some GIK 244's over the 2" panels might work very well. It might also be realted to speaker postioning in case which I would not do anything, as this might be fixed with speaker distance. What I do then is run some Pink PN or White PN with the mains running or not, and see how the settings on my DVD player effect it.

Summary - I look at the dips and what changes them, then find what I can do to change them, then check my results. It's a science.

[thewire]

For comparrison here is my first measurement, and some other ones I had first starting with REW. These are with the standard scale. Could be some slight differences in the settings used, but if I recall correctly there was no crossover engaged in the AVR. Measurements were taken at the center of the front row, which was slightly further towards the front wall at the time.

A bunch of measurements. No idea what these are. These are dated back to November 2006.



Mains and subwoofer



Waterfall



First spectral decay



Thank you for being so patient guys.

[thewire]

Here are the new results, this time with my 100lb door with 4" panels. I think it may be my second favorite room treatment. I will not have to worry about movies being loud anymore and shaking the door making noise while causing strange effects on the right side of the room. The 100Hz dip does not seem to be a problem, and does not show on my RTA measurements with the sub. I will need to check again however since moving the mains some more.

Right



Right2



Left2



Left



Filter



Left after filters
Others seats are +- 2.5dB difference 25Hz - 80Hz.



I have also modified the stage to prevent flanking and moved the subwoofers.

[thewire]

I'm trying something different because I have been reading about this LFE+Mains setting that are on receivers. I took two Crystal Acoustics plate amps which are rated 180W at 4ohm, and connected each to a Polk RTi70. I took them and placed them in the front left and right corners. I set the gain on them to THX, and measured a single one in my right corner. This is the subwoofer output into two additional mains without connecting the tweeters, so this is a total of 6 Rti70's with two ran on the subwoofer channel with the crossover 80Hz, and speakers set to small. The single Tower measured the same level 65dB as my subwoofers in the right corner, and had a roll off at 40Hz, and looking flat to around 200Hz with a small dip, but very similar looking to a near field of my subs. I checked the level of two of them to be 73dB, and with my subwoofers added it was 78dB. I turned down the level on my DVD player to 75dB, and made each channel 75dB, which was the same setting of -10. I placed my GIK Pillar trap laying over the center of my stage just bellow the center channel and two of the subs and measured.

This is what it looks like for each seat without calibrating the level, or changing filters.



Before turning down the level of the DVD player the volume was a little overwhelming, and I did try listening some with just the towers playing and it did not sound boomy, or distorted. After I turned down the level I tried the pod race scene in Star Wars Episode I, and I have to admit it sounded very good. I could localize some bass, but it was very 3D sounding and seemed to match what I saw on the screen. It also seemed to sound like it came much furthur into the room with the mid bass instead of being from just the screen. The lower bass I could not localize at all, and the left and right side of the room sounded and felt identical.

I did not care for aiming them at the sweet spot as I did in the measurement.

There is a limiter on the amps powering the mains with the sub channel, and they must only be set to around 60dB - 62dB each. The are rated to have response to 20Hz while my subwoofers are rated to 18Hz. If there is any reasons that this would not be a good idea please let me know. I will continue to see if I can find something wrong with it, but I woln't be tossing War of the Worlds in the DVD player just yet. I have watched the DVD at reference level with my mains set to large before, but the level they can play I think might not be the issue if there may be one.

Edit: Had to high a distortion for music and have since abandoned this idea but to instead place the GIK Pillar trap at a first reflection point.

Edit2: Lol my subs were 1dB hot to begin with. I could not tell because my Optimizer disc was not working yesterday but I could sure tell by listening. Crisis is over and onto other things.

[thewire]

I have a Outlaw 950 pre/pro now. Here are my left and right speakers prior to any changes other than swapping some drivers in the right speaker and swapping my left out for a new one. There is 1/3 octave smoothing.

[thewire]

I have been doing some more arranging of the lobby and the equipment room next to the HT. I moved out some wood and cardboard I had laying against the wall in the equipment room. I replaced that with a bookshelf at the request of others. I also placed another bookshelf in the lobby, and moved the candy counter away from the door. It gets crowded when people were walking around it, and it took longer for me to get to the equipment to start a movie. In other words I moved things in the next room. I also stacked some blankets in the left corner to try and maintain symmetry with the right side of the room. I can't say I notice much difference but there is a slight effect on the midrange when I measure the right side of the room, with the left channel+subs that I can see with it. When the wall heater is in use it tends to make some slight noise but I can't be certain if it was in the measurements or not.

This is using a Y-Cable for the left and right speakers and subs for each of the front row, and an averaged response of these with 1/3 Octave smoothing. Still having some problems I hear with the right side of the room. It is difficult to tell if is because of my first reflection points, or lack of absorption above the tiles above and behind me. Keeping in mind there is a steel ceiling layer with a foot of concrete above the tiles, it is a problem (might be what I hear) that is specific to my room. I hear whatever is causing this durring LFE or mostly during LFE that is after midrange bass, and it is uncommon maybe occurring once or twice in a movie if I have the volume up enough. Could be something to do with the left corner but I can't say for sure.

Dark green = right seat
Lighter green = right seat2
Orange = left seat2
Blue = left seat

[thewire]

Here is my left and then right speaker playing with the subs with the mic in the middle of the front row. I have been using a new method where I equalize more then raise the level up some to a 0 setting on the pre/pro. I plan to make another without the extra extention. The new mummy movie sounded very good to me at -5 reference and there was one moment where I was pushed back in my seat. The gunshots and the occassional action that was close to to the camera had very good impact in the midbass. I thought the movie sounded pretty near as good as it gets actually for everything about it. There might not have been a whole lot of bass I guess but still it was impressive.

[thewire]

I moved two of my subwoofers to the back of the room and did not apply the extra eq this time. These are the filters I used.

48.53 -11.00 .500
80.54 -7.0 .250



I have alot of work today as I will be adding another thing of R19 to the corners inside the Helmholtz Resonator and in a few other areas. I'm attaching some shelving to the 1/2" drywall outside the HT with a 3/4" peice of finish plywood also to add some stability to that part of the wall. I have some GIK 244's on the way also.

[thewire]

Make that two pairs of GIK 244's and a second matching GIK Pillar Trap on the way. Looks like I will be putting the R19 in the ceiling and possibly in the rear corners inside the Helmholtz Resonator. Doing some work on my stage also but not sure exactly what the plans are for the wood I bought, although I will find a use for it.

[thewire]

My first set of panels arrived. I will go into more detail later when more treatments arrive but for now here are some simple test I did with panels in two locations and one without panels for the control. Each speaker was set to same volume level setting.

The light blue is the left and the light green is the right. Darker colors are the measured results and any change to the frequency response. Decay looks best with them at the first reflection points but that is not shown yet as I am dealing with treating more than one location with regards to those changes. The mic began to clip around 2Khz.


With panels laying horizontal about at ear level on the left and right walls midpoints on each side of the first row.



With the panels at the first reflection points. I did not fine tune the position, rather placed them against the walls in front of the speakers some.

[t6902wf]

I would love to see photos of this room

[thewire]

The new panels seem to be addressing tones of issues. This morning I have found that one subwoofer was out of phase, and both left and right speakers were out of phase. I also found the 6 multichannel input is correctly boosting the sub input, where as the CD input does not. With these combined factors I was clipping the input of the BFD and listening to what I thought was -5dB reference level, actually being much higher. The first time I got my pre/pro was actually the correct calibration, and taking some short cuts leads to very improper calibrations. I had to lower the input of my mic, and I have yet to do some more advanced level calibrations, but using a -20dB FS Pink noise in both my CD player and REW, I have lowered the output for the subs in both my player (-10) and in the pre/pro allot. I will still need to confirm a few things but the RT60 looks much better. The ringing at 21Hz in my waterfalls is pretty substantial now, but I have lots more headroom. There is a dip at 100Hz around 5Hz wide with my subwoofers. It's a very narrow dip and I suspect it is related to measuring in the center of the room as doing so usually has revealed that. I cannot quite explain how adding panels has corrected a subwoofers phase but the panels have done some absorption pretty low. The subwoofer response is now a very large peak starting at 23Hz and falling off around 50Hz. I have wired them to have the most output at the crossover point, which is now slightly different and I suspect for changing the phase on a sub, for good reasons. This very well could have been why placing panels on each side of me effected the subwoofer timing. I'm just continuing to calibrate as I go.

Right + subs = green
Left + subs = blue

t6902wf wrote:

I would love to see photos of this room

I am still in the proccess of completing some treatments, but there are recent photos located in my build thread.

Gollum's Cave Theater

For more photos you can visit my Flickr account. I have to pay for this account starting in Feb.

Sets A work in progress but this has some nice photos of early construction. You will have to keep in mind the room was not in the budget, and this was to be a bare concrete room with no doors (just an opening) intended for storage before I found it was being built. Our contractor was very understanding.

All Photos These can get a bit confussing as I have tried many things, and they do not all have descriptions.

[thewire]

Based on what I found after calibration of the inputs with REW and the Pink PN, then using my player with a THX Optimizer, I must boost the subwoofer 15dB somewhere, and lower the level of the mains in the XA2 as much possible to -12 which gives me 75dB. I boosted the sub input 10dB in the player, and 5dB on the pre/pro.

So this being correct, I would need to lower the input of the subwoofer on my player -5dB as I have done previously to correctly measure in REW. Using my CD input more recently was a mistake, because this level input is lower and caused the subwoofer level to be set much higher with a difference of around 7dB or 10dB higher based on the equalization I would apply. Based on this when using external analog, one should likeley not use a CD input, but rather the mulitchannel input, then keep in mind that the level of calibration for the pre/pro may be relative to digital inputs or analog inputs and not based on a level for bypass with an internal crossover. This is just assumming I understand this correctly.