New Theatre Room Build 2020

[Guest]

To some extent, you are trying to chase your tail by playing with the location of the subs and manually adjusting delays, cross overs etc. Because of the complex interactions in the room, a tweak can either improve things or send you backwards. And it is difficult to predict what cumulative tweaks do.

 

Suggest using a more systematic approach by first optimising the subs and then let ARC do its magic. Use REW to measure the individual subs, run Multi-Sub Optimizer (MSO) to integrate the subs, and then run ARC. While I did MSO the hard way i.e. manually (results below), there is now a wizard to guide you.

 

This is a long video of how to use MSO wizard, but is probably the easiest way to learn about it in detail.

 

And please let me know if you need help with MSO...

[Quark]

1 hour ago, OzJustin said:

My measurements above are with Anthem ARC turned off. Measurement 56 shows the centre speaker plugged into my left channel and it seems to stay flatter between 80-200Hz than when plugged into the centre channel (measurement 55).

How do the other channels look to you?

 

The other channels don't look too problematic for close miking. If ARC is definitely Off for the baseline centre speaker measurement then I'd check if the wiring for your centre channel isn't reversed in polarity.

[jamiebosco]

@OzJustin

Hey Justin,

Can you plug everything back in as normal, put the mic back in the main listening position (make sure the tip of the mic is above the headrest, so the rear speakers have a clear path to the mic) 

And run a single sweep of each speaker, with them set to LARGE in the AVR and with ARC Genesis turned off,and post up the comparison here.

 

I think there is something up with the Center speaker, others look ok for a close mic'd response. As previously mentioned,maybe a woofer is blown,out of phase or the crossover network has developed a problem. But that speaker should dig way deeper than 300Hz

[jamiebosco]

3 hours ago, Snoopy8 said:

To some extent, you are trying to chase your tail by playing with the location of the subs and manually adjusting delays, cross overs etc. Because of the complex interactions in the room, a tweak can either improve things or send you backwards. And it is difficult to predict what cumulative tweaks do.

 

.

I agree, if Justin wants to go down the MSO path, that's a very good option!

 

But...with the new features in REW (Alignment tool) it is very very easy to do this yourself too. As long as you don't mind taking the initial measurements and looking at the graphs for a bit..

 

The Alignment tool lets you adjust the level and delay on a slider and see the response in real time

 

And I also agree, the best (and simplest) way forward WRT subs is to align the subs to get a nice flat response (in Justin's case,something like positions 1 ,4 and 14 with 90 deg phase ) and then run ARC and let it do the sub EQ. This is what I do in my system (except with Audyssey) with good results

 

 

 

I definitely think ARC should be able to do a good job when presented with a response like below, devoid of any major peaks or valleys

 

 

Other than the initial time Justin spent measuring the available sub locations , the actual time to get the above results in REW took me about 15-20 minutes 

[Guest]

@jamiebosco with dual subs, I agree it is relatively easy to use REW, but with than 2 subs, it becomes challenging. I am surprised you are not using MSO.?  With the new wizard, it is much easier to digest.

 

I have just joined the thread, not sure why @OzJustin  have issues with ARC?  ARC is superb, and usually provides excellent results. I suspect that Justin may have confused ARC with one too many tweaks.  Also, not sure whether ARC was rerun after a tweak on the subs?

 

Also, people sometimes do not like the crossover selected by ARC, but why can't a crossover be something else other than 80 Hz?  I had similar discussions in the MSO thread and gave up because too many are fixated on 80 Hz.

[jamiebosco]

1 hour ago, Snoopy8 said:

@jamiebosco with dual subs, I agree it is relatively easy to use REW, but with than 2 subs, it becomes challenging. I am surprised you are not using MSO.?  With the new wizard, it is much easier to digest.

 

I have just joined the thread, not sure why @OzJustin  have issues with ARC?  ARC is superb, and usually provides excellent results. I suspect that Justin may have confused ARC with one too many tweaks.  Also, not sure whether ARC was rerun after a tweak on the subs?

 

Also, people sometimes do not like the crossover selected by ARC, but why can't a crossover be something else other than 80 Hz?  I had similar discussions in the MSO thread and gave up because too many are fixated on 80 Hz.

More than 2 subs is easy as with the REW alignment tool, no harder than with 2. You really need to have a play with it. I don't use MSO because I'm trying to limit the complexity of my system. And manually aligning the subs was fairly simple, and I enjoy the process. I understand It's not enjoyable for everyone though

 

Maybe have a read of the thread from the start, Justin ran ARC with 1 sub, and the result was ok. I don't think he has re-run ARC since getting multiple subs setup (AFAIK). we are working on aligning the subs.

The recent discussion about his Center channel is not related to this, his center speaker is rolling off fairly high, ~300Hz, hence why ARC (correctly) crossed his center over at 225Hz. IMHO this is too high as much of the vocals will be routed to the sub,so I think he needs to get to the bottom of this first 

 

 

 

 

[OzJustin]

Thanks for the feedback @Quark, @Snoopy8, @jamiebosco, @almikel.

 

Jamie - I'll do a sweep of each channel per your suggestion. I don't recall seeing an ability to set speakers to 'Large' in the Anthem environment so I may just have to set the crossover to the lowest value, say 60Hz. I'm keen to get to the bottom of the centre channel roll off.

 

Snoopy - I've been following a REW and miniDSP tutorial series on Home Theatre Gamer on Youtube up to this point. It clearly walks you through step by step and seems to yield good results. Jamie has also been assisting as I'm pretty new to all of this stuff. I've had on my list to take a look at MSO though, so will look into that too.  

 

Mike - I've finally finished the bass trap project today and I'm pretty happy with how they turned out. They should still give me good practicality too (I added some handles to move around the smaller one) so I can access my home office area in the alcove. It does look a little like a "panic room" though, which probably isn't so out of place in a pandemic.  Next up will be to assess their actual performance. I was going to run a single sub with and without the traps in place, but now I'm wondering how best to measure their impact with my multi-sub arrangement in the works. Thoughts?

 

A build thread like this is worthless without progress photos so here are a few pictures of the trap project for anyone interested.

 

 

I also had some leftover black fabric so decided to frame my front stage. I'm running some fabric under the screen to hide things behind, then also some fabric over the projector frame legs and wheels and then a 1.5m deep strip out on the floor. I've run 1-2 movies with this arrangement and it really adds to the immersion. I'm also now considering painting my ceiling section directly above the screen in the Haymes New Life Flat Black paint.

 

 

[OzJustin]

18 hours ago, jamiebosco said:

@OzJustin

Hey Justin,

Can you plug everything back in as normal, put the mic back in the main listening position (make sure the tip of the mic is above the headrest, so the rear speakers have a clear path to the mic) 

And run a single sweep of each speaker, with them set to LARGE in the AVR and with ARC Genesis turned off,and post up the comparison here.

 

I think there is something up with the Center speaker, others look ok for a close mic'd response. As previously mentioned,maybe a woofer is blown,out of phase or the crossover network has developed a problem. But that speaker should dig way deeper than 300Hz

Can I clarify a couple of things for these measurements:

- Should I be setting my receiver for 75dB (using the REW SPL meter) for each channel before running the sweep?

- Do I want 20Hz - 20,000Hz in the sweep? Starting at 20Hz won't damage my speakers?

 

In my Anthem receiver I've set the following:

Subwoofer LPF for LFE - bypass

Bass management crossovers for front, center, surround, back and ceiling speakers - to off

Anthem ARC - off for the speaker profile applying to this input

Edited January 12, 2022 by OzJustin
Clarification

[jamiebosco]

5 hours ago, OzJustin said:

Can I clarify a couple of things for these measurements:

- Should I be setting my receiver for 75dB (using the REW SPL meter) for each channel before running the sweep?

- Do I want 20Hz - 20,000Hz in the sweep? Starting at 20Hz won't damage my speakers?

 

In my Anthem receiver I've set the following:

Subwoofer LPF for LFE - bypass

Bass management crossovers for front, center, surround, back and ceiling speakers - to off

Anthem ARC - off for the speaker profile applying to this input

I wouldn't worry about calibrating to 75dB , just do a low volume sweep. Does your AVR use the Relative Volume scale? if so, something around -25dBFS is fine, we're just trying to see the low frequency roll-off of each speaker. 

 

20Hz - 20kHz sweep is fine at low volume, If you're worried just start at 40Hz or so, we really just need them to be getting down to ~80Hz comfortably

 

Those settings seem right, the main thing is crossover is off and ARC is off.

Actually, I like the way Anthem word it better than most other AVR brands. Calling speakers Big and Small in AVRs just confuses most people about what the setting actually does. Actually stating that it turns off Bass Management is much better 

[OzJustin]

1 hour ago, jamiebosco said:

I wouldn't worry about calibrating to 75dB , just do a low volume sweep. Does your AVR use the Relative Volume scale? if so, something around -25dBFS is fine, we're just trying to see the low frequency roll-off of each speaker. 

 

20Hz - 20kHz sweep is fine at low volume, If you're worried just start at 40Hz or so, we really just need them to be getting down to ~80Hz comfortably

 

Those settings seem right, the main thing is crossover is off and ARC is off.

Actually, I like the way Anthem word it better than most other AVR brands. Calling speakers Big and Small in AVRs just confuses most people about what the setting actually does. Actually stating that it turns off Bass Management is much better 

Here's a measurement of all seven floor channels. I can email you the file if that's easier to read.  

[jamiebosco]

As I said in the email, I think the dips in the 100-200Hz range may be SBIR, try dragging one of your traps behind your front speakers and see if it helps it out

 

Even with the null in the Left and rights, (after applying an SPL offset to the speakers) I managed to get a nice transition between the speakers and the aligned sum of the subs if crossed over around 100Hz  

[almikel]

On 12/01/2022 at 8:21 AM, Quark said:

I wonder if the manufacturer has reversed the phase of the bass driver in the centre speaker - this can be a way of getting a smoother transition from mid to bass frequencies, but then will be out of phase with L&R so your correction software is rolling it off quite sharply.  Either that or the centre's crossover has an issue.

one of the reasons I like DIY - you get to make your own decisions around driver/crossover polarity

[almikel]

25 minutes ago, jamiebosco said:

As I said in the email, I think the dips in the 100-200Hz range may be SBIR, try dragging one of your traps behind your front speakers and see if it helps it out

the easiest way to see if an issue is SBIR or not is to change the speaker distance to the boundaries - if the response changes in frequency, then it's SBIR

[jamiebosco]

1 minute ago, almikel said:

the easiest way to see if an issue is SBIR or not is to change the speaker distance to the boundaries - if the response changes in frequency, then it's SBIR

Oh 100% agree Mike. 

But as the speakers probably can't move much (being HT mains with a huge screen in the middle) they are likely pretty close to where they need to be, I thought dragging a bass trap over a few ft behind the right speaker would show if treatment will help the null or not. My whole front wall is a 10" thick "trap" and it helped greatly in this area

[davewantsmoore]

1 hour ago, jamiebosco said:

Oh 100% agree Mike. 

But as the speakers probably can't move much

 

He wasn' suggesting moving them as the solution... but just as a test to indicate what is casing the dips.

 

If you move the speaker and a dip changes to a different frequency.... then you know the dip is being caused by the distance to the wall  (which we can really already know/assume it is..... but that's the test you should do it you want to know).

 

 

Everything looks fine with the response aside from the general tilt downwards below 1khz......  typically people like it the other way.   ie. a gentle tilt towards louder below 1khz.

[OzJustin]

Here's a measurement for SBIR for front right speaker. 

Measurement 8 (pink line) is close to the wall

Measurement 9 (green line) is approx 30cm out from the front and side walls

Measurement 10 (purple line) is with one bass trap behind and speaker directly in front of the trap

 

The null has moved slightly to the left but no substantial change. What does that tell us? Not SBIR? Bass treatment won't help?

[jamiebosco]

34 minutes ago, OzJustin said:

Here's a measurement for SBIR for front right speaker. 

Measurement 8 (pink line) is close to the wall

Measurement 9 (green line) is approx 30cm out from the front and side walls

Measurement 10 (purple line) is with one bass trap behind and speaker directly in front of the trap

 

The null has moved slightly to the left but no substantial change. What does that tell us? Not SBIR? Bass treatment won't help?

Justin, I'd just put the trap behind the speaker and SEE if the trap works. If it does, make a couple of 2' x 4' x 8-10" panels behind the speakers

 

 

[OzJustin]

7 hours ago, jamiebosco said:

Justin, I'd just put the trap behind the speaker and SEE if the trap works. If it does, make a couple of 2' x 4' x 8-10" panels behind the speakers

 

 

I’m confused. I’ve done exactly that (in measurement 10) and it seemed to make negligible difference?

[jamiebosco]

16 hours ago, OzJustin said:

I’m confused. I’ve done exactly that (in measurement 10) and it seemed to make negligible difference?

Damn... sorry mate, I was replying on my phone  and couldn't read the sweep info at the bottom!

 

 

Looking on my PC this morning, it doesn't really improve much under 200Hz, but does a great job of smoothing above that! Enough so that I would still look at putting something behind them,No need to worry about building frames either if you don't want, as it'll be behind the screen/curtains

 

As I said in the email, if you crossover around 100-120Hz you will get a nice transition between your mains and subs. Your summed sub response is flat out to 150Hz or so. 

 

 

Edited January 14, 2022 by jamiebosco

[OzJustin]

14 hours ago, jamiebosco said:

Damn... sorry mate, I was replying on my phone  and could read the sweep info at the bottom!

 

 

Looking on my PC this morning, it doesn't really improve much under 200Hz, but does a great job of smoothing above that! Enough so that I would still look at putting something behind them,No need to worry about building frames either if you don't want, as it'll be behind the screen/curtains

 

As I said in the email, if you crossover around 100-120Hz you will get a nice transition between your mains and subs. Your summed sub response is flat out to 150Hz or so. 

 

 

No worries at all. Fortunately I have one leftover bag (8 batts) of polyester insulation from my bass traps thst I could use. What kind of depth and height do you think would be worthwhile? Obviously I couldn’t go a huge 430mm deep trap but I could maybe manage 200mm behind the right speaker. I’m not sure there’s any point/possibility for the left speaker though as I have glass french doors directly behind the curtain there.

 

A 100-120Hz crossover sounds good to me. I can do some measurements to work out exact crossovers for each speaker.
 

Still thinking about what to do about the centre speaker. I opened it up yesterday and couldn’t see anything obviously wrong with the crossover etc but it was hard to see.

[jamiebosco]

Yeah 200mm (8") thick panel should be good

 

Do you have any other speakers around the house that could be used a center speaker till you work out what(if anything) is wrong with the current center?

 

Personally, I'd drag 1 of your rear towers up front and use it as a center for now and just run 5.1.4 till you can get your center looked at

 

Have you put the miniDSP in the signal path and set it up yet?

 

 

[OzJustin]

On 15/1/2022 at 12:44 AM, jamiebosco said:

Yeah 200mm (8") thick panel should be good

 

Do you have any other speakers around the house that could be used a center speaker till you work out what(if anything) is wrong with the current center?

 

Personally, I'd drag 1 of your rear towers up front and use it as a center for now and just run 5.1.4 till you can get your center looked at

 

Have you put the miniDSP in the signal path and set it up yet?

 

 

Fortunately I’ve got a leftover bag of the Bradford Polymax (8 batts) if that will suit. Any thoughts on recommended width and height? I could go 430mm wide (the size of the batts) and 2m high (two batts tall and will hide behind curtain. I was thinking of sealing the batts in painters plastic and then hiding behind my curtains.

 

I’m going to email VAF and get their thoughts on the centre channel. Had I not measured the response I’d be thinking it sounded fine. Ignorance is bliss!

 

Yes miniDSP is now setup and all three subs are now in position (went with positions 1, 4 and 14). Time to start the EQ this week!

 

I’ve also been busy painting the ceiling of my front stage this weekend before I put the room and speakers etc back in position. Will try to get some pics up early this week.

Edited January 16, 2022 by OzJustin

[jamiebosco]

13 hours ago, OzJustin said:

Fortunately I’ve got a leftover bag of the Bradford Polymax (8 batts) if that will suit. Any thoughts on recommended width and height? I could go 430mm wide (the size of the batts) and 2m high (two batts tall and will hide behind curtain. I was thinking of sealing the batts in painters plastic and then hiding behind my curtains.

Yep that's handy, I'd personally build 4 x panels, each with 2 x batts in them for double thickness.  So internal dimensions  of 430 wide x 1m(?) high and maybe 20cm deep . Put one behind the Left and Right and 2 behind the center. Or you could build them 860 wide and single batt thickness and use more air gap from the wall. Maybe Mike ( @almikel) will weigh in on what'd be best here. I had TONNES of polyester insulation, so went 600wide  x 1.2mHigh and 20cm thick on all 14 of my panels

 

Build a simple frame that will stand on its own. 

Ignore the text,that was for the frames I had made.Also, the picture isn't my panel,just one I found on the net to show the person building them for me what I wanted. I used cut down sheets of 16mm MDF because it's cheap and flat

[OzJustin]

Here's a brief status update post to show another little project I ticked off over the Christmas break. I decided to paint the front third of my ceiling (above the screen) in a flat black before I put all my gear back into place and start EQ'ing the multi-subs. I went with two coats of the Haymes New Life Flat Black. It was reasonably easy to apply and has made a big difference to the feel of the room. The whole front stage section is far more immersive than my original white ceiling. I just need to paint the two downlight covers black now before refitting them. I've only had a chance to watch one TV episode so far (War of the Worlds Season 2 finale on SBS - recommended) but so far I think it was worth the effort. There is still some reflection on bright scenes but it is markedly better. I think black velvet panels is the only way to go if you want a completely black whole screen area.

 

Here's some progress pics:

 

Note I'm yet to refit the front floor fabric section (see earlier posts) which should further improve the front stage immersion.

 

I've also done some further brief testing of my centre speaker. Here is a close measurement (red line) of the response and another with the two ports plugged (green line). It actually loses performance with them plugged. The close measurement doesn't seem to taper off as much between 50-200Hz now, especially when look at the reduced scale graph below. Perhaps it is a room treatment issue affecting measurements from my main listening position?

Note the scale - 40-800Hz range:

[jamiebosco]

3 hours ago, OzJustin said:

Here's a brief status update post to show another little project I ticked off over the Christmas break. I decided to paint the front third of my ceiling (above the screen) in a flat black before I put all my gear back into place and start EQ'ing the multi-subs. I went with two coats of the Haymes New Life Flat Black. It was reasonably easy to apply and has made a big difference to the feel of the room. The whole front stage section is far more immersive than my original white ceiling. I just need to paint the two downlight covers black now before refitting them. I've only had a chance to watch one TV episode so far (War of the Worlds Season 2 finale on SBS - recommended) but so far I think it was worth the effort. There is still some reflection on bright scenes but it is markedly better. I think black velvet panels is the only way to go if you want a completely black whole screen area.

 

Here's some progress pics:

 

Note I'm yet to refit the front floor fabric section (see earlier posts) which should further improve the front stage immersion.

 

I've also done some further brief testing of my centre speaker. Here is a close measurement (red line) of the response and another with the two ports plugged (green line). It actually loses performance with them plugged. The close measurement doesn't seem to taper off as much between 50-200Hz now, especially when look at the reduced scale graph below. Perhaps it is a room treatment issue affecting measurements from my main listening position?

Note the scale - 40-800Hz range:

Nice job on the painting mate! That looks awesome!!!