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post #61 of 80 Old 05-19-2018, 01:58 PM - Thread Starter
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MiniDSP 2X4 HD help!

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Originally Posted by ereed View Post
While you have downloaded the latest REW beta which is good, it appears you have a lot of REW questions and not fully know how to take measurements. Best to read the REW guide in Jerry's signature and relearn and start over before asking questions. First you had questions about EQ portion, then mac user portion, and now having questions about timing reference. While this thread is about minidsp or so we thought which isn't, I think you should read the REW guide and learn it before attempting to learn minidsp/ rew eq portion.





Once you get REW setup and read the guide and learn it, post questions in the REW thread (after you read it). Once you understand it all, then want to learn EQ filters and minidsp then that should be last IMO unless you just have multiple subs and want to connect all subs to minidsp and run it all bypass for the moment without EQ filters or anything.



And to answer your question about acoustic timing reference....select one speaker (could be left or right speaker) and keep it the same for ALL measurements.

I realize that it seems like I’m all over and I have been. I have read the guide, I was not having issues with REW when I started the thread. I updated to the beta on the PC and it’s not working, probably a bootcamp glitch.

I took one members advice and switched to Mac. It worked but when I tried to set the acoustic timing reference channel per Austin’s guide to SL it used the LFE channel. I’ve checked the channel mapping and it’s correct, but yet they’re one channel off. It must be a bug with the current beta. Here is a pic of my channel map. And the channel selected for the acoustic timing reference yet it used the LFE channel until I switched SR.



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post #62 of 80 Old 05-20-2018, 05:46 PM - Thread Starter
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Does anyone have experience running a MiniDSP 2x4HD with an Anthem AVM60? I’m worried about the voltage from the AVM60 overdriving the MiniDSP.


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post #63 of 80 Old 05-22-2018, 09:21 AM - Thread Starter
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Ok here are the final sweeps before and after.


There pretty close to the predicted results

Thanks Jerry for all your help and putting up with all the crazy questions


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post #64 of 80 Old 06-09-2018, 06:19 PM
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Quote:
Originally Posted by veger69 View Post
Does anyone have experience running a MiniDSP 2x4HD with an Anthem AVM60? I’m worried about the voltage from the AVM60 overdriving the MiniDSP.


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I think Anthem's ARC is an extremely good calibration sw. I have an Anthem MRX 710 with ARC2. I am using miniDSP 2x4 HD with Anthem. I don't use mini for EQ purposes though. My two subs are diagonally placed in the opposite corners in the room, so, use mini to set the correct time delay between the two at the MLP. ARC takes care of the rest and the whole system sounds amazing with bone jarring bass. Btw, my room acoustics suck.

The problem with your subs is placement and you simply cannot overcome it with EQ. Your subs are not serving any good purpose to the overall combined response at the MLP coz they are pretty much exciting the same room modes. I would reckon to disperse them i.e. one up front and one behind your listening position. Then add delay (in the miniDSP) to the one closest to you to time align it with the farthest one and then run ARC on top of it.

Moreover, your EQ'd response looks amazing on paper but I bet it will not sound even half as good. That 10dB EQ boost in 43Hz-62Hz pass band will wring the living daylights out of even an Orbit Shifter LFU. Use EQ to cut peaks; for dips, change the sub(s) location. For every 3dB boost, you need double the amp power. For 10dB you are asking your sub amp to deliver 10 times the power.

Like I said before, correct your sub response by spreading them across the room, preferably, along different walls. That way you will be able to excite multiple room modes and then you can bring the peaks down with EQ.

Also, sound is all about input. Garbage in; garbage out. EQ can only do so much.

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post #65 of 80 Old 06-10-2018, 12:34 AM - Thread Starter
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Quote:
Originally Posted by braveheart123 View Post
I think Anthem's ARC is an extremely good calibration sw. I have an Anthem MRX 710 with ARC2. I am using miniDSP 2x4 HD with Anthem. I don't use mini for EQ purposes though. My two subs are diagonally placed in the opposite corners in the room, so, use mini to set the correct time delay between the two at the MLP. ARC takes care of the rest and the whole system sounds amazing with bone jarring bass. Btw, my room acoustics suck.

The problem with your subs is placement and you simply cannot overcome it with EQ. Your subs are not serving any good purpose to the overall combined response at the MLP coz they are pretty much exciting the same room modes. I would reckon to disperse them i.e. one up front and one behind your listening position. Then add delay (in the miniDSP) to the one closest to you to time align it with the farthest one and then run ARC on top of it.

Moreover, your EQ'd response looks amazing on paper but I bet it will not sound even half as good. That 10dB EQ boost in 43Hz-62Hz pass band will wring the living daylights out of even an Orbit Shifter LFU. Use EQ to cut peaks; for dips, change the sub(s) location. For every 3dB boost, you need double the amp power. For 10dB you are asking your sub amp to deliver 10 times the power.

Like I said before, correct your sub response by spreading them across the room, preferably, along different walls. That way you will be able to excite multiple room modes and then you can bring the peaks down with EQ.

Also, sound is all about input. Garbage in; garbage out. EQ can only do so much.
I have three subs two at 1/4 front wall positions and one at the rear center position. I get better results when I turn the rear off. Less dip in the 45hrz-62hrz range
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post #66 of 80 Old 06-10-2018, 08:42 AM
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Quote:
Originally Posted by veger69 View Post
I have three subs two at 1/4 front wall positions and one at the rear center position. I get better results when I turn the rear off. Less dip in the 45hrz-62hrz range
That means you need to play with the rear subs phase/delay/polarity either in the sub or in minidsp and possible driver orientation and keep remeasuring. If your rear sub is giving you a dip, its probably cancellation issue. Each sub you add in the system should be complimenting it, not making it worse....if it does then you need to figure out why and keep playing with it til it improves your bass response. Also don't forget to play with sub distance delay last in AVR once you got the minidsp all set. But keep working on placement and such....this takes time.

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post #67 of 80 Old 06-11-2018, 09:24 AM
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Quote:
Originally Posted by veger69 View Post
I have three subs two at 1/4 front wall positions and one at the rear center position. I get better results when I turn the rear off. Less dip in the 45hrz-62hrz range
Don't mind but if that's the FR of your room, the applied EQ is not going to give you quality bass. I wouldn't add even a single dB boost to fill the dips. Any boost in the subwoofer region compresses the dynamic range of the system by as many dB. That flat EQ looks great on paper, but I don't think it sounds half as good.

Moreover, that 10dB cut around 20Hz will increase group delay causing massive ringing (it's visible in the waterfall chart). I would personally avoid any filters below 30Hz.

I would use EQ above 30Hz, and that too, only for cutting peaks not for raising dips. To mitigate dips, I would employ multiple subs at multiple positions.

Remember, alignment in time domain is more important between multiple subs than frequency domain.

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post #68 of 80 Old 06-15-2018, 10:51 AM - Thread Starter
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MiniDSP 2X4 HD help!

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Originally Posted by braveheart123 View Post
Don't mind but if that's the FR of your room, the applied EQ is not going to give you quality bass. I wouldn't add even a single dB boost to fill the dips. Any boost in the subwoofer region compresses the dynamic range of the system by as many dB. That flat EQ looks great on paper, but I don't think it sounds half as good.



Moreover, that 10dB cut around 20Hz will increase group delay causing massive ringing (it's visible in the waterfall chart). I would personally avoid any filters below 30Hz.



I would use EQ above 30Hz, and that too, only for cutting peaks not for raising dips. To mitigate dips, I would employ multiple subs at multiple positions.



Remember, alignment in time domain is more important between multiple subs than frequency domain.


So I would do that by setting the individual and overall boost to 0? Alignment in time delay is observed on the impulse tab correct? And you delay the closest sub to align with the farthest. I measured all subs separately and the impulse reading seemed pretty clear but when you overlay the subs how do figure the difference between the subs? For example I’ve attached the pic below I just adjusted the delay on the back sub until they seemed lined up. Is there a more accurate way to do it?


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post #69 of 80 Old 06-15-2018, 12:18 PM
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Quote:
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So I would do that by setting the individual and overall boot to 0? Alignment in time delay is observed on the impulse tab correct? And you delay the closest sub two align with the farthest. I measured all subs separately and the impulse reading seemed pretty clear but when you overlay the subs how do figure the difference between the subs? For example I’ve attached the pic below I just adjusted the delay on the back sub until they seemed lined up. Is there a more accurate way to do it?


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Yes that's correct. How far are your subs from MLP? Btw your rear sub is playing earlier by 4.5 ms compared with front ones. If the IR graph is correct, you need to add 4.5 ms to the nearest sub in order for it to time align with front ones

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post #70 of 80 Old 06-15-2018, 12:34 PM - Thread Starter
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Quote:
Originally Posted by braveheart123 View Post
Yes that's correct. How far are your subs from MLP? Btw your rear sub is playing earlier by 4.5 ms compared with front ones. If the IR graph is correct, you need to add 4.5 ms to the nearest sub in order for it to time align with front ones

The fronts are about 8’ equal-distant the rear is 4.5’. How do you determine that 4.5ms? the distance from 0ms to the start of the curve deviation?



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post #71 of 80 Old 06-15-2018, 12:52 PM
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Quote:
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The fronts are about 8’ equal-distant the rear is 4.5’. How do you determine that 4.5ms? the distance from 0ms to the start of the curve deviation?



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Distance from 0 ms to the first peak. First peak for the rear sub is centered at 7 ms (the difference of 3.5 ms in the rear sub's distance is due to inherent characteristic of bass frequencies travelling slower in air compared with high frequencies).

The first peak of both front subs is centered at around 11.5 ms. So, the time difference between the rear sub and pair of front ones is 4.5 ms. Add 4.5 ms delay in the rear subs delay setting in miniDSP such that it's first IR peak moves at 11.5 ms mark. I think you should be able to get rid of that dip in 42-65 hz pass band.

Forget about sub distance setting in AVR for now. We are aligning only subs at this stage.

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post #72 of 80 Old 06-15-2018, 12:58 PM
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Alternatively, you can flip the phase switch of rear sub and it's first peak will land right where the front subs' IR is. You won't have to add delay for the rear sub.

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post #73 of 80 Old 06-15-2018, 01:06 PM - Thread Starter
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Quote:
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Alternatively, you can flip the phase switch of rear sub and it's first peak will land right where the front subs' IR is. You won't have to add delay for the rear sub.

Isn’t the first peak of the front subs at 7.5ms and not 11.5ms?
I did flip the phase on the rear sub originally, it had the opposite affect increasing the dip at 40hrz.


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post #74 of 80 Old 06-15-2018, 01:17 PM
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Isn’t the first peak of the front subs at 7.5ms and not 11.5ms?
I did flip the phase on the rear sub originally, it had the opposite affect increasing the dip at 40hrz.


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I would look at the first peak. But having said that, you can do it either way. First flip the rear subs phase 180 opposite and take the FR and IR. Then add 4.5 ms delay in the rear subs delay setting in mini then again take the FR and IR.

If still there are peaks and dips, they are room induced and you cannot remove them by incorrectly setting the delay for the rear sub. You need more subs and/or change sub locations. OR alternatively do the room treatment. I wouldn't care about the peaks. But dips are obvious signs of all the subs being out of phase in certain pass bands if they are not perfectly time aligned OR they are room induced.

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post #75 of 80 Old 06-15-2018, 01:35 PM - Thread Starter
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MiniDSP 2X4 HD help!

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I would look at the first peak. But having said that, you can do it either way. First flip the rear subs phase 180 opposite and take the FR and IR. Then add 4.5 ms delay in the rear subs delay setting in mini then again take the FR and IR.



If still there are peaks and dips, they are room induced and you cannot remove them by incorrectly setting the delay for the rear sub. You need more subs and/or change sub locations. OR alternatively do the room treatment. I wouldn't care about the peaks. But dips are obvious signs of all the subs being out of phase in certain pass bands if they are not perfectly time aligned OR they are room induced.

Ok I’m going to place the rear sub in the MLP and do some RTA measurements to first find the best position. I’m placement limited but can move the back sub along the wall and the front subs can be placed in the corners instead of at 1/4 positions. Once I have them placed I’ll get them on the same phase, but like I said when the rear sub phase was flipped it increased the dip. Maybe if I get them in better positions it may change the interactions.
Just so I understand, by peak you mean the second peak and in the example just flipping the phase would align them?


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post #76 of 80 Old 06-15-2018, 01:45 PM - Thread Starter
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MiniDSP 2X4 HD help!

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FR and IR.

“FR” I think you mean do a sweep to record the frequency but “IR” how do I evaluate that?



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post #77 of 80 Old 06-15-2018, 01:53 PM
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Quote:
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“FR” I think you mean do a sweep to record the frequency but “IR” how do I evaluate that?



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Sorry for confusion. IR is part of FR sweep, though in separate window.

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Quote:
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Just so I understand, by peak you mean the second peak and in the example just flipping the phase would align them?

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First is not a peak as far as front subs are concerned. It's a dip. Their first peak occurs at 11.5 ms.

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post #79 of 80 Old 06-15-2018, 02:05 PM - Thread Starter
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Quote:
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First is not a peak as far as front subs are concerned. It's a dip. Their first peak occurs at 11.5 ms.


Ok, I get it. Thanks braveheart! If I flip the phase on the rear sub the peaks align. Otherwise, I need to delay the rear sub so “peaks” align


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post #80 of 80 Old 06-15-2018, 02:07 PM
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Quote:
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Ok, I get it. Thanks braveheart! If I flip the phase on the rear sub the peaks align. Otherwise, I need to delay the rear sub so “peaks” align


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Yes.

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