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Which order to apply room correction tools?

alanhuth

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I am now at the point where I want to try some equalization, timing, etc. My system is 2.1 with 3 subwoofers. My DAC/preamp is a MiniDSP SHD, so I can do all of the DSP filtering these tools offer. It also includes DIRAC. What is the best sequence to apply these tools: e.g. B, A, D, C, etc.?

A. Front Speaker placement, with help from "Rational Speaker Placement" (Sumiko Method)
B. Multi-Sub Optimizer (MSO)
C. DIRAC
D. Sub placement - crawl method or ??
E. REW - frequency response filtering
F. REW - timing and phase adjustments
G. Room treatment

Thanks
 

andyc56

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I am now at the point where I want to try some equalization, timing, etc. My system is 2.1 with 3 subwoofers. My DAC/preamp is a MiniDSP SHD, so I can do all of the DSP filtering these tools offer. It also includes DIRAC. What is the best sequence to apply these tools: e.g. B, A, D, C, etc.?

A. Front Speaker placement, with help from "Rational Speaker Placement" (Sumiko Method)
B. Multi-Sub Optimizer (MSO)
C. DIRAC
D. Sub placement - crawl method or ??
E. REW - frequency response filtering
F. REW - timing and phase adjustments
G. Room treatment

The miniDSP SHD should not be used with MSO. MSO depends on the usage of mono bass -- that is, traditional bass management. But a proper implementation of traditional bass management has the "room correction" after the point at which the multiple channels are summed to form a single mono bass channel, that is, after bass management. From the diagram below, it can be seen that the SHD's Dirac processing is before the mixer. This means that the summed mono signal used for the bass depends, among other things, on the relative phase of the transfer functions of the Left and Right channel Dirac correction in the bass region, which is uncontrolled.
miniDSP_SHD.png


The SHD design is just fine for stereo bass, as in a pair of actively biamped two-way speakers. But MSO is not intended for stereo bass. In fact, the whole theory of optimization of multiple subs as originally written by Welti and Devantier assumes mono bass and traditional bass management. There are advocates of stereo bass out there, namely Griesinger, and I don't want to open that can of worms. Rather, I just wanted to warn users about incompatibility with MSO.

Of course, miniDSP will never admit this.
 

onion

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Is that true for miniDSP 2x4HD without Dirac? That you shouldn't use MSO?
 

voodooless

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The idea would be to find an initial setup where little corrections are needed. For that, I would suggest this order:

1. ask partner where it is acceptable to setup speakers and subs.
2. Convince him/her otherwise ;)
3. Setup speakers and place subs around the room, doing sweeps to find out where you have the flattest response. You can also fiddle with the sub settings and delays to optimize. Verify with REW
4. Treat your room
5. Apply Dirac
 

dfuller

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Pretty much in order:

Speaker placement, room treatment, time alignment, EQ correction. Anything you can do physically will be a better use of your time and money than trying to fine tune room response via DSP when you still have undamped reflections and speakers placed haphazardly.
 
OP
A

alanhuth

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That makes sense. I’m a little confused about a couple things.

One is the Multi-sub converting all subs to one. Then how to use that merged sub in other tools?

Second, what is the relationship between EQ correction/timing adjustments and what DIRAC does?
 

oursmagenta

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The idea would be to find an initial setup where little corrections are needed. For that, I would suggest this order:

1. ask partner where it is acceptable to setup speakers and subs.
2. Convince him/her otherwise ;)
3. Setup speakers and place subs around the room, doing sweeps to find out where you have the flattest response. You can also fiddle with the sub settings and delays to optimize. Verify with REW
4. Treat your room
5. Apply Dirac

On 4 and 5, it may depends on your constraints I guess. For my personal case, I think it'd be easier (and it had :oops:) to convince my beloved second half to spend money on Dirac first, than covering the living room with absorbers/diffusers/bass traps (the approval for tower speaker + sub wasn't easy to get). Worse than that if the Dirac live bass management can (I'm not saying that it will) get me better decay times below 120hz, I think that she will prefer me to buy another sub than to put bass traps anywhere in the room.
 

onion

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Will be interested to hear of any successful Dirac-based multisub (3 or more) correction using the MiniDSP. I'd definitely get it if that was possible.

One is the Multi-sub converting all subs to one. Then how to use that merged sub in other tools?

I use Anthem Room Correction. I run it once to get the levels matched between subs and mains. I then turn off the subwoofer setting in ARC and upload that to the AVR.

There's a very good walkthrough of using the miniDSP for bass management. The 4th part shows how to select the optimal crossover after bass management and room correction.
 

voodooless

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On 4 and 5, it may depends on your constraints I guess. For my personal case, I think it'd be easier (and it had :oops:) to convince my beloved second half to spend money on Dirac first, than covering the living room with absorbers/diffusers/bass traps (the approval for tower speaker + sub wasn't easy to get). Worse than that if the Dirac live bass management can (I'm not saying that it will) get me better decay times below 120hz, I think that she will prefer me to buy another sub than to put bass traps anywhere in the room.

Well, he asked about it. But I fully agree with you. Better spend a lot of time setting up the subs, than stuffing your living room full of bass traps. For a dedicated studio that might be different though. For the midrange however, there really is no good cure for bad acoustics. I’m myself in the process of convincing my other half to get some panels in.. It’s not an easy sell..
 

abdo123

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If you know the spinorama of your speakers then DSP is the most effective thing you can do. However, without that information it’s going to be a long painful process.

Dirac is worth every penny, it’s chef’s kiss.
 

dfuller

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Well, he asked about it. But I fully agree with you. Better spend a lot of time setting up the subs, than stuffing your living room full of bass traps. For a dedicated studio that might be different though. For the midrange however, there really is no good cure for bad acoustics. I’m myself in the process of convincing my other half to get some panels in.. It’s not an easy sell..
Certainly different. Studios are all about making reverberation all be the same length, around 300ms RT60 generally.
 
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Eetu

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:facepalm: no it isn’t
Care to elaborate? Every speaker (and thus, the in-room response) can be improved with EQ. Let's assume we have a speaker with an uneven anechoic response but good directivity. What's more effective than DSP in improving SQ?
 
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Care to elaborate? Every speaker (and thus, the in-room response) can be improved with EQ. Let's assume we have a speaker with an uneven anechoic response but good directivity. What's more effective than DSP in improving SQ?

It’s been said multiple times in this very thread so didn’t think I needed to.

Proper speaker placement and room treatments are both more important than DSP.
 

abdo123

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It’s been said multiple times in this very thread so didn’t think I needed to.

Proper speaker placement and room treatments are both more important than DSP.

That's just bullshit.

an absorber doesn't remove the early reflections, it only reduces its volume, they also do not have flat absorption curves so the volume reductions are not consistent over the entire frequency range. As result, your off-axis response is getting colored / less flat.

If your speaker has good directivity, EQ will impact both off-axis and on-axis response equally.
 
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That's just bullshit.

an absorber doesn't remove the early reflections, it only reduces its volume, they also do not have flat absorption curves so the volume reductions are not consistent over the entire frequency range. As result, your off-axis response is getting colored / less flat.

If your speaker has good directivity, EQ will impact both off-axis and on-axis response equally.

TIL DSP is more effective at removing room reflections than acoustic treatments.

anyways, I’d just suggest approaching this subject without dogmatism- you might learn something ;)
 

abdo123

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TIL DSP is more effective at removing room reflections than acoustic treatments

Harman's research has shown that early reflections are important, you're not supposed to remove them but rather correct them.

That's what DSP do. However, reflections cannot be corrected when they don't follow the same radiation pattern as the on-axis response. For example, if there is a dip at 1KHz on-axis, that dip needs to exist as well in Early reflections / off-axis, otherwise DSP can't correct it, it will make it worse.

Because it is the on-axis response + the early reflections together that you measure with a measurement microphone at your home.

I tried to explain it as good as I can. If you want you can go and watch this video for more information

 

Eetu

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+1

Proper speaker placement and room treatments are both more important than DSP.
You can't do speaker correction with room treatments.

And when it comes to below 100Hz, you'd need a boat load (well.. a van) of thick absorption to even approach what you can do with a filter or two using EQ.
 
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Harman's research has shown that early reflections are important, you're not supposed to remove them but rather correct them.

That's what DSP do. However, reflections cannot be corrected when they don't follow the same radiation pattern as the on-axis response. For example, if there is a dip at 1KHz on-axis, that dip needs to exist as well in Early reflections / off-axis, otherwise DSP can't correct it, it will make it worse.

Because it is the on-axis response + the early reflections together that you measure with a measurement microphone at your home.

I tried to explain it as good as I can. If you want you can go and watch this video for more information


im not going to argue with you, just trying to stop someone from misleading others.
 

abdo123

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im not going to argue with you, just trying to stop someone from misleading others.

I’m not the one asking people to barricade their windows and sand their chimneys. You’re asking people to alter their living spaces and saying that this is something they should do before they intelligently design filters based on their speakers.

You’re the villain here.
 
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