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Discussion Starter #1
Yesterday I started again from scratch, moving subs around the room and taking measurements. I set it to acoustic timing using left main as reference. (I think it worked)
Here is the results how each location measured. (Have not gotten to mains yet)
A,2,LP1 = sub A, location 2, Listening Position 1 etc.
MDAT LINK


Now I like the idea of having both subs up front, but not sure it is my best option.
Here is some measurements with A & B up front.
MDAT LINK


Looking at location measurements I decided to have a play with SubA, Location7 & SubB, Location12.
Honestly, I am still lost when it comes to this bit, no idea what I'm looking at on the Impulse or the Phase charts :-/
I have read a lot, but what I read, and what I am practicing seem a bit different haha.
Anyway, for no other reason but for some earlier advice saying flip subA and add 24ms delay, Thats where I started.
Here are the measurements.
MDAT LINK
Just before hanging up the mic, I quickly did some auto eq'ing (A180,A29MS,EQ). To me it looks ok in LP1, but LP2 did not like 29MS delay.
Overall, I am struggling here with LP2.
Probably both subs up front may be better option?


For the record, I am not overly concerned with LPC, so if LP1 & LP2 are good, but LPC not so good, I will live with that.
LPC folds down like a table with cup holders and usb power etc. nobody really sits there.

Would be great if anyone could give opinions/advice, as, even with all the reading, I really am still firing a bit blind. :nerd2:

Dedicated Room 4.5/4/2.7m L/W/H (no treatments as yet, other than full floor to ceiling curtains entire length of side walls.)
1 row of seating, 3 positions.
Umik USB
Dual MiniMarty's tuned 17hz
Dual Dayton Ultimax 18"
Inuke NU6000DSP
Denon X4400H
 

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Discussion Starter #2
Decided I will stick with both subs symmetrically placed up front.

Listening Position C (LPC)


LP1


LP2


LP1, 2 and C


LPC


LP1


LP2


LP1, 2 and C


LPC


LP1


LP2


LP1,2 and C
 

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Discussion Starter #3
Obviously still learning as I go here.
What I think I have discovered is I need to get LPC right first? It seems LP1 and LP2 both sum similar to LPC.


If not, when adding delay to get LP1 to sum constructively, then LP2 becomes destructive. and vice versa.
Makes sense being that its all symmetrical.

Problem is, with subs up front, there is a room mode that really messes with LPC.


Do I have no hope with this arrangement?
 

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I am not clearly following the extensive work you have done so far, but can suggest a logical approach for setting up the 2 SWs for your consideration. There are several other methods that can also be used to provide excellent results. This is just the method that I have used and it has provided very good results.

The basic steps are:
  1. Select the 2 SW positions by looking for complementary SPL at the LP.
    [REW Sweep Measure each optional SW location individually with mic at LP and XO active at 80 Hz. If there are 4 potential SW locations then only 4 measurements are needed to analyze each combination in REW (1+2, 1+3, 1+4, 2+3, 2+4, 3+4). Acoustic timing should be used and the XO must be active so that it allows the use of these same measurements in the following steps. In this step we are just looking to find 2 SW positions that when added together results in a relatively flat SPL response; one that can cover the target bass range and can be easily EQed. The SW can be at the LP and mic at the 4 positions as Wayne indicated above if that is easier.]
  2. Determine the delay needed on the nearer SW.
    [The Step 1 measurements can be combined within REW to confirm the actual SPL that will result from the 2 chosen positions. The delay is then applied and SWs measured in the chosen positions for confirmation of the analysis.
  3. Preliminary EQ can be applied to the SWs.
    [A smooth SPL of the 2 SWs will aid in the following step.]
  4. Determine the needed delay of the SWs relative to the mains.
    [Measurements of the FL main, FR main and the Eqed SWs are used in REW to determine the SWs to Mains delay needed. Those delay settings can then be applied and measurements made to confirm the analysis.]

If you want to use this method I can detail each step as necessary and also help with the REW analysis to determine the delays. That part is a bit complicated to fully explain, but I can provide analysis and delay recommendations and answer your questions. There are other threads where I have provided similar assistance.
 

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Discussion Starter #5
Firstly thanks heaps for your reply :grin2:

I am not clearly following the extensive work you have done so far, but can suggest a logical approach for setting up the 2 SWs for your consideration. There are several other methods that can also be used to provide excellent results. This is just the method that I have used and it has provided very good results.
Was pretty much just posting all the info I can, might mean something to you guys and saves you having to ask for it.

  1. Select the 2 SW positions by looking for complementary SPL at the LP.
    [REW Sweep Measure each optional SW location individually with mic at LP and XO active at 80 Hz. If there are 4 potential SW locations then only 4 measurements are needed to analyze each combination in REW (1+2, 1+3, 1+4, 2+3, 2+4, 3+4). Acoustic timing should be used and the XO must be active so that it allows the use of these same measurements in the following steps. In this step we are just looking to find 2 SW positions that when added together results in a relatively flat SPL response; one that can cover the target bass range and can be easily EQed. The SW can be at the LP and mic at the 4 positions as Wayne indicated above if that is easier.]
  2. Determine the delay needed on the nearer SW.
    [The Step 1 measurements can be combined within REW to confirm the actual SPL that will result from the 2 chosen positions. The delay is then applied and SWs measured in the chosen positions for confirmation of the analysis.
  3. Preliminary EQ can be applied to the SWs.
    [A smooth SPL of the 2 SWs will aid in the following step.]
  4. Determine the needed delay of the SWs relative to the mains.
    [Measurements of the FL main, FR main and the Eqed SWs are used in REW to determine the SWs to Mains delay needed. Those delay settings can then be applied and measurements made to confirm the analysis.]
I actually have an understanding of this process, however I continue to confuse myself often, and also the people I try to explain myself too haha. I read a guide, put it into practice without understanding it. Then re read the guide and it made more sense, so put into practice again. Have gone through the process atleast 10 times, each time picking up on mistakes i made previously... Last of which, I was trying to keep both subs up front, and found it hard to get good summation in both LP1 & LP2. Adding delay to one sub would only spoil the other LP.

Here is my room and sub positions.



I have taken measurements in positions 1 to 7 in all 3 listening positions.
Here is LPC measurements only. *Will explain why after.




*As for why I'm thinking I need to concentrate on LPC, am I correct in thinking it will be easier if I get LPC nice, LP1 and LP2 should be pretty close?
But if I try to get LP1 right, because of the distance to LP2 it will be much harder to get them right in LP2?
 

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Discussion Starter #6
This weekend I will take another set of room measurements, this time include positions 8-14.
I dont see them being much different to the first measurements down the other side of the room though, hence why until now I had not bothered.
Will then concentrate on getting LPC looking good and hope LP1 and 2 are not too bad.

In the mean time, do any of the above locations like like they have potential if combined?
 

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The attachments do not appear.

I would suggest using only the LPC for the initial steps. We can assume the initial step of selecting SW positions via SPL will result in reasonable results at the other positions. If necessary we can revise the position selection if that is not the case. With 7+ options there is a pretty good chance to find 2 that work well with each other. If you have several preferred locations for the SWs we consider those first. There is a good chance that 2 of them will work out.

Measurements at the other listening position are more helpful when setting the EQ.

You may find This thread interesting. It's little dated as the REW features are improved greatly since then.
 

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Those appear to be the Post 1 attachments again. I had accessed and commented on those. It is the Post 9 attachments that I do not have access to.

Too many measurements only confuses the issue for me. There are at 3 mdat files containing 60 measurements in Post 1. My analysis needs to be based on specific measurements. None of them fully fit the needed requirements. I can glean some limited info regarding locations from some them, but I don't have the time to spend time trying to figure out which of these 60 measurement are the best to use.

I will however look at the Room2.mdat file to see if that is helpful for the first step of choosing locations. The limited sweep range, various delays and lack of XO is not a major issue for that 1st step. It will prevent using that same data for the future steps however. I will try to pull some useful info out as an example, but will not dive into the other 2 mdat files. I will report on this effort in my next post.

So:
If you provide an LP measurement of each SW position you want considered, I will review the options and suggest which 2 locations appear to be good possibilities and provide some evidence and explanation to support the choices. The measurements must meet the requirements detailed below.

Measurements Conditions:
  • mic at LPC
  • XO active. [Current measurements do not have the XO active, or were possibly measured using HMDI channel 4 which bypasses the XO. Measure using Channel 1 or 2 with that main speaker disabled]
  • REW Sweep full range (12-20k Hz) [The high end is required for use with future mains measurements. Also it is best not to start too far below where the SPL rolls off. The SPL measurements are solid to 20Hz so using 12Hz is a reasonable lower limit for the sweep. There is no useful info below that point that is relative to our objective here.]
  • REW acoustic timing active.
  • Set a 3ms delay for all measurements. [All future recommendations for delay changes will assume that reference was used for the measurements.]

Measure:
Optional SW locations [Please limit the number of places to 7 or less, i.e., 7 total measurements. There are 21 combinations of 2 in 7 locations. That is a lot to analyze. If you have more than that please select the preferred location and try to include some positional asymmetry as front, back and side wall locations. We both already observed that using only the 2 front SW locations did not work out well. This suggests that alternate locations be considered for one or both SWs.]
 

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I analyzed Room 2.mdat to try to find the best locations for the 2 SWs.

I dropped mic locations 1 and 2 and was left with mic location LPC. That left 7 measurements that apparently represent 7 potential SW locations.

Below are the impulse timings adjusted so they are all reasonably timed the same.
1- IR Aligned.JPG

Below are the 21 combinations of the 7 locations to show SPL of all the potential choices.
2- Combined SPL.JPG

Below are the 3 combinations that appear to be the best choices. Any of these would likely work well using reasonable EQ.
3- SPL 3 Options.JPG

Below is the best of the 3. It is locations 2+4, aka "A,2,LPC + A,6,LPC".
4- SPL Best of 3.JPG

If there was a different set of locations than these that you wanted to consider you can post up to 7 of them and I will analyze them. That analysis will complete Step 1.

If you want to use one of the 3 good options here for your setup then Step 1 is done. To do Step 2 we need to measure these 2 locations again using the measuring conditions provided in my previous post. Also, be sure to use the same main channel as the reference for all future measurements. I had forgot to list that requirement in the measurement conditions provided in Post-10. Those conditions will work well for all future measurements.
 

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Discussion Starter #12
Thanks again for your reply, and thanks for pointing out what measurements are useful from here in. Will save me a lot of time :)

One quick question though regarding acoustic timing.
My understanding was I was to use channel 4 for subs and channel 1 for acoustic timing, with that main active.
This is the first time i have been told to use channel 1 for sub measurements.

I have looked for info on this but could not find anything useful (for me).
So before I continue taking measurements that are wrong, in newb language, could you explain how exactly to run a measurement with acoustic timing please?

I'm assuming now
Sub/s channel 1 (main unplugged)
acoustic reference channel 2 (main plugged in)
?
 

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Yes, I have seen setup methods that use channel 4 and they report good results. I have never tried that method. I think it has a disadvantage, but don't know if it is serious enough to be concerned with. I assume they use channel 4 as it doesn't require disabling the main speaker, i.e., it is a little easier method.

The reason to use channel 1 is so that the XO is active. That way we can see the SPL rolloff through the XO range and also see the correct SW phase rotation through that range. The active XO impacts both of these items. This becomes important when we are determining the delay needed to match the SWs to the mains. I prefer to use the method that is more informative. I believe it to be more technically correct, but possibly the difference is not significant.

Assuming you are using a single sub output to drive a stereo P-amp to provide delay and EQ to the 2 SWs then a good option is:
  • Disable the left main and leave the right main connected.
  • Measure Channel-1, (Reference Channel-2) with SW-1 active and SW2 muted.
  • Measure Channel-1, (Reference Channel-2) with SW-2 active and SW1 muted.

If the setup is different from my assumption and this scheme is not suitable, another method may be needed. I can advise if that is the case.
 
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