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Speaker placement and subwoofer integration for a small living room using MiniDSP SHD + REW

abdo123

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For the low frequency slope, after doing those tests, I found that it was about 70hz.

Can you share the .mdat file containing the measurements? Did you try sealing the ports and then measure?
 
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xovaan

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abdo123

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Sure thing! Does this work?

https://drive.google.com/file/d/12TUNypK8unSDp_SkL18whbfzcif3h505/view?usp=sharing

I haven't stuffed the ports yet; I just did laundry so I have some dish towels I can add today :D

For the ports, am I taking .25" cone readings with the ports stuffed or just checking frequency response as usual?

yes stuff the ports (tightly, no air should escape from them), measure the full range driver but limit the measurement to 300 Hz (10Hz to 300Hz) no need to measure any higher.

I checked the measurement and i understand why you're a little confused, hopefully after you seal the ports the response of the driver should clean up.
 

abdo123

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This is my best attempt with the current measurements. the driver has an accoustic Linkwitz-Riley (LR) 12db/oct @ 88Hz. This is likely to change once the ports are stuffed.

1634495285967.png
 
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xovaan

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This is my best attempt with the current measurements. the driver has an accoustic Linkwitz-Riley (LR) 12db/oct @ 88Hz. This is likely to change once the ports are stuffed.

View attachment 159680
Interesting! I just stuffed the port of the left speaker (the one in those measurements you are using) and sealed with masking tape:

1634495733097.png


Which part of the graph are you reading to get 88hz from? Apologies

 

abdo123

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Time for some decision making, LR2 @ 80Hz or LR2 @ 100Hz? (I highlighted the parts you requested).

1634497251015.png


1634497344550.png


Moving forward i want you to experiement with the ports closed, only add a low pass crossover the subwoofer in SHD (nothing on the speaker) and figure out which one sounds better to you, 100Hz or 80Hz. Also make sure that the SHD output is plugging into the LFE input, so the internal crossover circuit / filter of the subwoofer is defeated.

1634497528884.png
 
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xovaan

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Stuffing the other speaker and will report back!
 
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xovaan

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Looks like 100/12 LPF is ideal, yeah? (confirming that both subs are on LFE)

1634501665049.png

1634501679923.png


I mean they all kind of suck a bit but 100/12 is def the best haha
 

abdo123

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Looks like 100/12 LPF is ideal, yeah? (confirming that both subs are on LFE)

View attachment 159717
View attachment 159718

I mean they all kind of suck a bit but 100/12 is def the best haha

Okay, I hope you gave it a listen too! hopefully it should sound very seamless and integrated.

However the speaker is still being delivered full-range signal so we need to do something about that. First, have a look at the figure below and absorb it.

1280px-Linkwitz_vs_Butterworth.svg.png


When Linkwitz and Riley made the LR filter they stacked basically two Butterworth filters. However stacking two LR filters is not a good idea. So we need to 'change' the LF behavior of the speaker using DSP so it has a Butterworth (BW) LF behavior. To do that I want you to add this PEQ filter for BOTH speakers only (Advanced -> paste biquads).

a1
1.990742674422280​
a2
-0.990785313730776​
b0
1.001907440057730​
b1
-1.990742674422280​
b2
0.988877873673046​

I generated it from a mega excel sheet that MiniDSP provides.
1634503201773.png


and then apply these crossover parameters. below is for the speakers outputs

1634502988408.png


and this is for the subwoofers.

1634503070378.png


I hope you're following up to this point, let me know if you have any questions.
 

abdo123

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I think I'm following! :D

PEQs applied:
View attachment 159730
Crossovers applied:
View attachment 159733
View attachment 159732
How does it sound? even without Dirac it should sound effortless and you shouldn't be able to tell where the subwoofers are.

you just need to gain match the subwoofers to the speakers now (Make it so that both the subs and the speakers would play equally loud when they recieve equal input signals from the SHD). but you should do that after the crossover is finalized.
 
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xovaan

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Gonna try giving them a listen now! Here's the before/after for measurements:

Red is the sub 100/12 crossover from our first run-- in each graph, both subwoofers are firing along with the speaker being tested. Prior to our measurements, I did your Dirac timing trick as well:

1634504404827.png


1634504423757.png


It's really cool that with math alone you are able to see that fantastic increase in dB across the board!
 
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xovaan

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With gain matching, am I gain matching sub to sub, then left sub to left speaker and right sub to right speaker, or sub to sub, then sub+sub to speaker+speaker? Or something else entirely?

edit: they're all matched-- speaker+speaker is the same as sub+sub, and each individually matches when played solo :)
 

abdo123

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With gain matching, am I gain matching sub to sub, then left sub to left speaker and right sub to right speaker, or sub to sub, then sub+sub to speaker+speaker?
Your subs are identical and so are your speakers

So you can match any speaker to any subwoofer.

To do gain matching you need to do near-field bass measurements again. So let’s finalise the crossover first.
 

abdo123

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Okay gain matching.

First, start by putting the gain on the speakers on -3 dB (remove it once you're done gain matching).

1634505903141.png


Then, moving forward, only use the SHD for volume control, if you can defeat the volume control on the SMSL amp then do it. if you can't, figure out a good position for the volume knob and NEVER move it moving forward . Remember, Dirac can take up to 10 dB away so you want it to be a little high but not too high so hiss would be really loud from the speakers.

Do a near field measurement of the speaker (with crossover, no Dirac tho, only one output enabled in the matrix) (10-300Hz is fine). Keep that measurement saved, that will be our 'reference', don't forget baffle step adjustment! you cannot change the master volume in SHD moving forward, keep that in mind.

Now i want you to do near field measurement of the subwoofer (again, with crossover, no dirac, only one output enabled on the matrix), and again don't forget the baffle step adjustement :D.

Now keep fiddling with the gain knob on the back of the subwoofer (never touch the speakers or their volume control, or the SHD, don't forget baffle step adjustment for each measurement) until both the speaker and the subwoofer meet at 100Hz like the pic below (pic is actually 80Hz but you get the jist of it). with neither of them being louder than the other (use all SPL display in REW).

index.php
 
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abdo123

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@xovaan

Subwoofers have signficantly higher linear excursion, so be careful not to hit your mic incase the subwoofer moves during a measurement!
 
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xovaan

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Ahh, back-- had to step out for a sec and catching up on your post. So you're saying I'm doing the anechoic test on the subwoofers now too?
 
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