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Running dual subs independently on MiniDSP DDRC-24 and Dirac Live

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#1
Hi all,

first of: This place is really a refreshing source of wisdom regarding audio without the vague fuss surrounding it in so many other places. I really learned a lot the last weeks simply by reading the great discussions here. So thanks alot :)

Situation
I want to build up a 2.2 System with the Genelec 8030C, Canton AS 30 (Active Subwoofer) and the MiniDSP DDRC-24HD as DAC / DSP / Preamplifier. Since the review of the 8030C in the Review of Amirm showed relatively high distortion starting at 125 Hz, I want to set the Crossover frequency at this. I know that this could make the subs position audibly but fortunately I can place them circa 0.5 m to the side of each of the Genelecs. I also want to use Dirac for the final room correction.

Question
Should I use both subs as mono channel in a summed fashion like proposed on the MiniDSP homepage (https://www.minidsp.com/applications/audio-streaming/sub-integration-with-shd) or can (and should) I run them in stereo due to the high crossover? I would prefer the second option.

My plan
  • Forward on the DDRC-24 CH1/Dirac1 to Genelec1, CH2/Dirac2 to Genelec2, CH1/Dirac1 to Sub1, CH2/Dirac2 to Sub2 (MINIDSP recommends: DDRC-24 CH1/Dirac1 to Genelec1, CH2/Dirac2 to Genelec2, CH1/Dirac1 + CH2/Dirac2 to Sub1, CH1/Dirac1 + CH2/Dirac2 to Sub2) (both subs would be connected with only one rca cable each)
  • Adjust Volume and time delay with REW and set values in MiniDSP
  • Run Dirac Room Correction
  • Finish
Are my thoughts / plan sound? Why would MiniDSP even recommend running dual subs as one summed up subwoofer?

Best regards
Dominik
 

phoenixdogfan

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#2
Hi all,

first of: This place is really a refreshing source of wisdom regarding audio without the vague fuss surrounding it in so many other places. I really learned a lot the last weeks simply by reading the great discussions here. So thanks alot :)

Situation
I want to build up a 2.2 System with the Genelec 8030C, Canton AS 30 (Active Subwoofer) and the MiniDSP DDRC-24HD as DAC / DSP / Preamplifier. Since the review of the 8030C in the Review of Amirm showed relatively high distortion starting at 125 Hz, I want to set the Crossover frequency at this. I know that this could make the subs position audibly but fortunately I can place them circa 0.5 m to the side of each of the Genelecs. I also want to use Dirac for the final room correction.

Question
Should I use both subs as mono channel in a summed fashion like proposed on the MiniDSP homepage (https://www.minidsp.com/applications/audio-streaming/sub-integration-with-shd) or can (and should) I run them in stereo due to the high crossover? I would prefer the second option.

My plan
  • Forward on the DDRC-24 CH1/Dirac1 to Genelec1, CH2/Dirac2 to Genelec2, CH1/Dirac1 to Sub1, CH2/Dirac2 to Sub2 (MINIDSP recommends: DDRC-24 CH1/Dirac1 to Genelec1, CH2/Dirac2 to Genelec2, CH1/Dirac1 + CH2/Dirac2 to Sub1, CH1/Dirac1 + CH2/Dirac2 to Sub2) (both subs would be connected with only one rca cable each)
  • Adjust Volume and time delay with REW and set values in MiniDSP
  • Run Dirac Room Correction
  • Finish
Are my thoughts / plan sound? Why would MiniDSP even recommend running dual subs as one summed up subwoofer?

Best regards
Dominik
No reason not to do what you plan as far as I can see. Whether you use summed or discrete inputs into the sub the respective outputs you assign to your individual sub should IMHO make no difference as long as you are crossing over low enough b/c the bass will be essentially omnidirectional below 80-100 hz. So either way of doing it should sound the same AFIK.

If someone has a different opinion, or other concerns re the OP's approach, pls chime in.
 
OP
D
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Thread Starter #3
Hi pheonixdogfan, thanks for the reply.

Well, I plan to cross over at 125 Hz with at 48 db/oct slope for both subwoofers. So some parts should be locatable. But since the subwoofers are standing at max. 0.5 m away from their monitor "partner" and on the same distance to the MLP I hope that should be not a too big problem.

One thing to add: My Setting is not completely symmetric. So one subwoofer would stand in a corner when the other is ca. 1.5 m away from the other corner of the same wall. I don't know if this is an argument in favor to treat both subs independent or if this has no impact when treating both together as one LFE like from MiniDSP proposed.
 

Otaku+

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#4
This is essentially the same configuration that I use; stereo subwoofers with a high crossover point. It works well.

unknown.png
 
OP
D
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Thread Starter #5
This is essentially the same configuration that I use; stereo subwoofers with a high crossover point. It works well.

View attachment 85762
Good to hear that i am not the only one ;)

Interesting setup. I assume the XTZ is your main system and you only use sub2 and sub3 at the same time and not sub1?
I also assume u use the dirac live feature since you have the DDRC-24. Does sub2 get only the left channel and sub3 the right channel or are they treated as one subwoofer since both are getting left and right channel?
 

richard12511

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#6
Hi pheonixdogfan, thanks for the reply.

Well, I plan to cross over at 125 Hz with at 48 db/oct slope for both subwoofers. So some parts should be locatable. But since the subwoofers are standing at max. 0.5 m away from their monitor "partner" and on the same distance to the MLP I hope that should be not a too big problem.

One thing to add: My Setting is not completely symmetric. So one subwoofer would stand in a corner when the other is ca. 1.5 m away from the other corner of the same wall. I don't know if this is an argument in favor to treat both subs independent or if this has no impact when treating both together as one LFE like from MiniDSP proposed.
I don't think 125Hz is really locatable. 80Hz was chosen because it was a full octave lower than the lowest frequency that one person was able to locate under blind test. From what I remember, no one else besides that one guy was able to locate anything below ~200Hz. Going by memory, so some of the numbers might be slightly off.
 

Otaku+

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#7
Good to hear that i am not the only one ;)

Interesting setup. I assume the XTZ is your main system and you only use sub2 and sub3 at the same time and not sub1?
I also assume u use the dirac live feature since you have the DDRC-24. Does sub2 get only the left channel and sub3 the right channel or are they treated as one subwoofer since both are getting left and right channel?
Yes. The XTZs are part of my main (HT/music) system along with Subwoofer 2 and 3, which are connected to channels 3 and 4 of the DDRC-24 respectively. Each subwoofer crosses over to an individual Dirac channel rather than being summed. My DDRC-24 has two stereo SPDIF outputs (modified), so only the subwoofers are connected directly to the analog outputs.

My crossover point is 120Hz.
 
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#8
I think that you can run them as stereo subs. If it were me, I would. I have several systems with stereo subs crossed over from 120Hz to 150Hz.

Actually, since you say you want to avoid an increase in distortion that occurs from 125Hz on down in your mains, I'd suggest you try an even higher crossover. Perhaps be daring and take it to 200Hz just to see how it sounds. That is, assuming the subs have good response that high, or higher.
 
OP
D
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Thread Starter #9
Thanks for your replies! So my confirmation bias is satisfied since I take away that it is technically sound and also possible with the DDRC-24 and Dirac and I am not alone ;)

Regarding an even higher cross-over: The subs have a knot (which I dont use) with a max crossover frequency of 150 Hz. I would assume that this is the highest frequency where the sub still works good.

When the second sub arives next week I will test after Dirac Calibration with REW and Music and report back:
  • Crossover 50 Hz; Stereo Sub
  • Crossover 100 Hz; Stereo Sub
  • Crossover 150 Hz; Stereo Sub
  • ? Crossover 200 Hz; Stereo Sub ?
  • Crossover 150 Hz; Mono Sub
Since there are 4 Presets storable on the MiniDSP switching between them should be easy.
 

CDMC

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#10
I don't think 125Hz is really locatable. 80Hz was chosen because it was a full octave lower than the lowest frequency that one person was able to locate under blind test. From what I remember, no one else besides that one guy was able to locate anything below ~200Hz. Going by memory, so some of the numbers might be slightly off.
The sharp crossovers also help. 12 db octave results in the sound down 12 db at 160hz with a 80hz crossover. With a 48db at 125hz, it should be down more than 20db at 160.
 
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#11
It is a MiniDSP DDRC-24 with 4 different presets. Set one with the subs in stereo and another with them summed. Try different crossover points and slopes. Compare 'em back to back and see which one you prefer. The beauty of it is you can test different options and find the one that suits you, your equipment, and your room the best.
 

Cbdb2

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#12
Stereo. First an anecdote. When I bought my 3way full range speakers, I listening to them for about 10seconds in the store and thought they went very low for an 8 inch driver in an relatively cheap speaker. I asked the sales guy if there was a sub going, he said no. I followed my ears to a far off corner and found the sub, he was embarresd. At that high a xover youll locate the subs. Which will smear the sound stage in mono, Think about a dull bass guit panned hard left, the image will not be hard left and it will move depending on the note. ( how much info above the xover freq.) The other thing to remember is that theres still info above the xover going to the sub, ( not usually brickwalled). And due to fletcher-munson those freq are 10db easier to hear. For a sub to be non locatable its xover has to be quite low, below 60 and have a steep filter.
 

phoenixdogfan

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#13
I think that you can run them as stereo subs. If it were me, I would. I have several systems with stereo subs crossed over from 120Hz to 150Hz.

Actually, since you say you want to avoid an increase in distortion that occurs from 125Hz on down in your mains, I'd suggest you try an even higher crossover. Perhaps be daring and take it to 200Hz just to see how it sounds. That is, assuming the subs have good response that high, or higher.
A lot of them don't. This is the published Frequency Response of my SB 2000. It's flat from 30-140 Hz, then rolls off pretty fast after that

1601668226471.png
 
Last edited:

Otaku+

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#14
This is only tangentially related to your original question but I feel obligated to point out that the DDRC-24's Dirac implementation provides no user feedback of any kind with regard to the amount of available headroom following correction. It is important that you either take note of your target curve's peak volume during calibration and reduce the DDRC-24's master volume accordingly or shift your target curve to a point below 0dB prior to export. Otherwise, you will end up with clipping.

This is a silly problem which doesn't need to exist and could have been solved with ten lines of code but somebody was apparently lazy.
 

andreasmaaan

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#15
The main reason subs are recommended to be run mono is not specifically to do with localisation (although the difficulty we have in localising subs at the frequencies they play is ofc a necessary precondition). Rather, subs can be placed in a room in such a way (e.g. centred along opposing walls) that they can cancel primary room modes - but it only works if they are reproducing the same (i.e. mono) signal.

Since you plan to place your subs beside your main speakers anyway, such a setup is out of the question. And in any case, many modern studio-recorded content, the low- and mid-bass will be more or less in mono anyway. So, depending on your music taste, you're likely to be listening to primarily mono bass anyway. There will be some tracks that show up a difference ofc, depending on your XO frequency and slope (keeping in mind, as others have pointed out, that a 125Hz XO point does not mean that there is no output from the sub above 125Hz).

Anyway, I second what @tjkadar suggests. Try a few different configurations and listen with a few different types of recordings to see what seems to work for you.
 

CJH

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#16
I was in a similar situation as Dominik with a pair of Philharmonitor 2-way monitors (5.5" woofer) each sitting on top of a 12" active sub (DIY sealed GR Research servo). Since the monitors in-room were good to around 60Hz., I simply set the crossover on the subs to 60Hz at 12dB and got a nice blend. After seeing Amir's measurements I too wondered about rising distortion using small woofers and its audibility. Rather than go all-in like Dom, I bought a DBX 223 ($70 used at Guitar Center) similar to CDMC's set-up for an active analog crossover at around 120Hz. at 24dB to test. Really nice improvement overall. Since my monitors sit on top of the subs "location audibility" is not a problem, but time alignment is still important for proper transient response between the monitors and subs. Moving the monitors back/forward even 1/8" is clearly audible with double bass, drum etc... transient attack. You'll know when it's right by ear or can measure to confirm. I will enjoy listening for a while before I venture into anything more complex and expensive.
CJH
 
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Lorenzo74

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#17
Yes. The XTZs are part of my main (HT/music) system along with Subwoofer 2 and 3, which are connected to channels 3 and 4 of the DDRC-24 respectively. Each subwoofer crosses over to an individual Dirac channel rather than being summed. My DDRC-24 has two stereo SPDIF outputs (modified), so only the subwoofers are connected directly to the analog outputs.

My crossover point is 120Hz.
hi I’m very much interested into your modded DDRC24. Is it the modification described in some website?
 

Otaku+

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#18
hi I’m very much interested into your modded DDRC24. Is it the modification described in some website?
You simply need to extend the AK4626's BICK, LRCK, MCK, DATA1/2, DATA3/4 and GND to a pair of external WM8804 boards. It's a standard I2S implementation, with the DDRC-24 as master clock. If you only need one stereo SPDIF output, then you can omit DATA3/4 and use a single WM8804 board.

1606588078801.png


MCK and GND can be taken from the header just across from the 4626.

1606587859203.png


You can then pass all of those pins to the external WM8804 board via Lemo or similar connector.

1606587995453.png
 
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