Jump to content

baMarek

Multi-Sub Optimizer

Recommended Posts

On 07/03/2018 at 7:46 AM, Snoopy8 said:

In the above thread, @dziemian, ex DEQX owner mentioned that if starting again, would use a mini DSP to manage the MSO side of things. @almikel, maybe that is the easier than trying to work it work using DEQX alone?

Taking things further, a possible set up for DEQX & MSO co-existence could be:

  1. Use DEQX for mains only above 150/200 Hz.  Do not use DEQX for subs
  2. Take sub output from DEQX into a mini DSP to feed the dual (or more) subs.  Subs should not have any DSP enabled.
  3. Measure mains together with DEQX enabled and individual subs without DEQX
  4. Run MSO with standard filters : gain, delay, cross over (?) and PEQs
  5. Enter MSO filters into mini DSP for each sub
  6. Further tweaking with DEQX if required.

Need to discuss whether to use a cross over for MSO.  If not using, MSO has 1 less variable to tweak.  Should crossover be set in DEQX or MSO or both ???

 

@almikel @andyc56  is this a possible setup to leverage the strengths of both DEQX and MSO and minimise the clash?

 

p/s Andy, your example target curve and documentation do not match.  Example should be using LF Shelf Order 2 Variable Q (Alt).  Used your suggested workaround method to generate target curve which is adequate for my purpose, and I think for most people as well.

Share this post


Link to post
Share on other sites
25 minutes ago, Snoopy8 said:

DEQX & MSO co-existence could be

 

 

You want the DEQX to apply DSP to the bass.   You just want to help it where it has a gap in capability.

 

  1. Connect subwoofers to a miniDSP (or similar) which does IIR correction ... and something like REW as the inputs
  2. Apply EQ to each individual SW output  (also delay, if there are relative delays between SWs)   and optimise the summed SW response over your listening position(s)
  3.  If multiple SW inputs will be used (eg. if DEQX outputs stereo bass) .... sum them to mono in the miniDSP

 

Now connect DEQX subwoofer output(s) to the miniDSP ..... and run the DEQX setup/calibration as normal.   Let it apply it's DSP to everything/anything (including bass).     It should not need to apply much/any EQ to the SW portion of the response, of course (as you already made it flat)  ...... however it will flatten the phase of the bass (in line with the overall linear phase response it produces).... and also align the bass to any target response you chose.

Share this post


Link to post
Share on other sites

@davewantsmoore

Let me add to your suggestion. MSO has a subs only option which is used for HT setups when room correction is run after the subs are "integrated" by MSO.

 

Subs only will use delay, gain and PEQ, no cross over (which resolves my earlier questions).  Process then will be to measure subs individually (no DSP), run MSO (subs only), enter filters into mini DSP, then run DEQX for whole system.

Share this post


Link to post
Share on other sites

Yes!   (That's what I was suggesting, just didn't mentioned the setting for 'subs only' in MSO)   :) (y)

Share this post


Link to post
Share on other sites

some minor tweaks to the above:

 

If you're running DEQX 3 way active plus subs with the older model HDP3

  • you'll need to split the DEQX low pass analog outputs L1/R1 and send them to the bass driver amp and the miniDSP (good point by Dave to mono them in the MiniDSP). 
  • Note that any correction FIR filters you added to the bass driver will have an effect on the input to the MiniDSP (it's not a "passthrough" signal). In my case I run a bunch of FIR EQ to push my bass drivers lower before they cross to my sub. DEQX has adjusted phase and amplitude independently to flatten the response of my bass drivers based on the DEQX measurement of the bass drivers. "undoing" this FIR EQ for input to subs "may" not be easy. Best not to apply any DEQX correction on the lower area of the bass drivers
  • In my case I run double DEQX (both HDP3), and will need to continue to use double DEQX even if I add a MiniDSP to run MSO to avoid this issue

If 2 way active plus subs then the L1/R1 outputs are only for the subs and will only have DEQX correction if you choose to apply it to the subs (and the intent is apply EQ via the MiniDSP not DEQX). You can mono in DEQX or MiniDSP

 

The newer model DEQX HDP4/5 have a "digital passthrough" - this would be preferable to use provided your MiniDSP (or similar) has digital in.

 

cheers

Mike

 

Share this post


Link to post
Share on other sites
17 hours ago, Snoopy8 said:

p/s Andy, your example target curve and documentation do not match.  Example should be using LF Shelf Order 2 Variable Q (Alt).  Used your suggested workaround method to generate target curve which is adequate for my purpose, and I think for most people as well.

Good catch.  I've updated the target curve example to use the LF Shelf Order 2 Variable Q (Alt). Thanks.

Share this post


Link to post
Share on other sites


Posted (edited)

 

Quote
  • "undoing" this FIR EQ for input to subs "may" not be easy. Best not to apply any DEQX correction on the lower area of the bass drivers

 

Why do you need to "undo" anything the DEQX does.

 

1.   Measure subs (without DEQX) using REW or similar, and program corrections for each subwoofer into mininDSP.

 

2.   Connect the DEQX subwoofer outputs to the miniDSP input ..... and then use the DEQX as normal.     

 

Quote
  • The newer model DEQX HDP4/5 have a "digital passthrough" - this would be preferable to use provided your MiniDSP (or similar) has digital in.

No, it wouldn't.

 

Why prevent the DEQX from operating on the bass?    If you did this, then below you will miss out on the DEQX target curve, and it's phase linearisation, for the subwoofer.

Edited by davewantsmoore

Share this post


Link to post
Share on other sites
Posted (edited)
2 hours ago, davewantsmoore said:

2.   Connect the DEQX subwoofer outputs to the miniDSP input ..... and then use the DEQX as normal.    

They are not always "subwoofer outputs".

They are Bass Outputs which can be either stereo (Left and Right Bass Outputs) or mono (Subwoofer Outputs).

In my case they are Bass Outputs with Left and Right Bass under 150Hz.

Edited by Satanica

Share this post


Link to post
Share on other sites
2 hours ago, Satanica said:

In my case they are Bass Outputs with Left and Right Bass under 150Hz.

That makes it more difficult.

 

 

In that case, then do in this order ....

 

1.   Connect subwoofers to miniDSP .... and add bandpass filter for 3rd subwoofer.

2.   Using a mono signal .... Optimise EQ/delay for each woofer, based on the summed response of all 3 woofers 

2.   Connect DEQX stereo bass outputs to miniDSP.    In the miniDSP, Route L input to L sub, R to R, and sum of LR to the 3rd subwoofer

 

 

Now run DEQX setup/cal as normal   (you DO need to re-run DEQX cal, if you change anything in the miniDSP)

 

 

 

Share this post


Link to post
Share on other sites
11 hours ago, davewantsmoore said:

Why do you need to "undo" anything the DEQX does.

...in this specific case I've applied significant FIR EQ boost to the low pass analog output of the DEQX based on the FIR correction filter applied after a close miked measurement of the output of the bass driver (pushing my TD18s down from 100Hz to 40Hz or so). You don't want that FIR boosted signal going to a sub obviously.

 

11 hours ago, davewantsmoore said:

Why prevent the DEQX from operating on the bass?    If you did this, then below you will miss out on the DEQX target curve, and it's phase linearisation, for the subwoofer.

You may have an exaggerated view on DEQX capabilities - they're clever and I love (both of) mine, but possibly not as clever as you think...although perhaps my understanding of their best application is also lacking...and your posts did make me think...

 

This is OT for the MSO thread, so Mods feel free to move it to the DEQX thread...

 

I'll outline my understanding of DEQX capability in the context of bass management and phase linearisation.

Assuming a single DEQX unit - so 3 outputs - setup as stereo tri-amped or 2 way active mains plus 1 or 2 subs (and apologies for the shouting below, but those bits are key)

  • DEQX only applies FIR filter correction during speaker calibration/correction after a DEQX speaker measurement. Room correction is all IIR.

For a triamp setup (eg a 3 way full range speaker)

  • ideally you would drag the speaker outside, set it up way off the ground and do a DEQX Speaker Measurement. Each driver measured separately, but with the mike in the same place, and as a single "speaker"
  • At your leisure you can then calibrate that speaker (and it's twin if you're lazy and didn't measure the other speaker) with different Xover points and slopes, and apply speaker correction based on the measurement. Correction filters target a flat response, but you can limit how much correction is applied. Correction and Xover filters are linear phase FIRs

For 2 way active + 1 or 2 subs

  • you would drag the 2 ways outside and measure and calibrate as a single speaker (no sub)
  • you might drag a sub outside and measure, but you'll always have at least 1 boundary (the ground) to "window" out, losing low frequency data, or not "window" and include the ground response in the measurement. Subs are heavy, and dangerous to consider getting high enough off the ground for low frequency accuracy if "windowing", so "in room" close miked measurements are the usual fall back. 
  • DEQX can provide an FIR correction filter based on either measurement - but it's a correction of the sub on its own (as a single "speaker")

But it did make me think - you could easily do a "speaker" measurement of the sub in the room with the mike at the listening position and get DEQX to create an FIR "speaker calibration" correction for that microphone position...but it could easily make things much worse elsewhere...averaging over multiple positions is not possible - you only get to "calibrate"/correct based on a single measurement

  • in the 2 way + sub /s scenario DEQX provides the option of linear phase or IIR Xover filters between sub and mains (with inbuilt delay limitations, so sub Xovers may have to be IIR or less steep FIRs) - but DEQX doesn't "correct" anything between the mains and sub/s when they're separate - further integration requires "room measurement" and "room correction"
  • All "room correction" in DEQX is IIR and global 

Once you've measured and calibrated your speakers in as good a semi-anechoic environment as possible, further "in room" work is all IIR, so performing a "system" calibration with DEQX doesn't provide any further phase linearisation 😫

 

cheers

Mike

 

 

Share this post


Link to post
Share on other sites
Posted (edited)
11 hours ago, almikel said:

...in this specific case I've applied significant FIR EQ boost to the low pass analog output of the DEQX based on the FIR correction filter applied after a close miked measurement of the output of the bass driver (pushing my TD18s down from 100Hz to 40Hz or so). You don't want that FIR boosted signal going to a sub obviously.

Well...  as long as the EQ for the subwoofer sets the response to flat, then it doesn't matter.

 

Sure, if there was another output you could use (with no boost already active), then you could use that instead.... but in this case, there isn't.

 

 

You may have an exaggerated view on DEQX capabilities - they're clever and I love (both of) mine, but possibly not as clever as you think...although perhaps my understanding of their best application is also lacking...and your posts did make me think...

 

 

Perhaps I wasn't clear enough.

 

I suggest (following my instructions, and then) working through the DEQX manual, using the "two way speaker, plus stereo subwoofer" method.... but using the advanced procedure:

 

Quote

 

13.6 WOOFER CALIBRATION WITH AN IN-ROOM MEASUREMENT The woofer of a three-way speaker can be calibrated with a speaker measurement taken with the microphone at the listening position. This technique can be used if the three-way speaker is being implemented with the “bi-amp with optional stereo subwoofers” speaker configuration mode

 

 

You'll end up with something looking like:

 

655030677_deqxwoofer.JPG.b7cb2886e3f858289507f973a5e926b0.JPG

 

Where the blue and gree line are the bass woofer from the 3 way speaker, and all 3 subwoofers playing together  (there is a crossover at 80Hz).    DEQX doesn't know ior care it's not "one" speaker.

 

Multiple listening positions has already been considered.   You know that this summed response from the LP represents the best response over all relevant positions.

 

Now the DEQX speaker cal will do:

 

Gain - to match this channel with the BigRed mid/high.

EQ - although it shouldn't find much to do - as you have already calibated each woofer in the miniDSP to produces the best summed response

Phase -   It should have alot to do (there is phase error due to the 80Hz high/low pas)

Target -  EQ to taget - there'll be a low pass at ~150Hz to match the BigRed mids .... and anywhere else the target might be not flat  (eg. a low shelf boost)

 

.... then the DEQX can do, "room EQ"

 

 

Edited by davewantsmoore

Share this post


Link to post
Share on other sites
22 minutes ago, davewantsmoore said:

Well...  as long as the EQ for the subwoofer sets the response to flat, then it doesn't matter.

Agree. MSO will optimise whatever the subs produce.   

 

Best to set a baseline sub response then do MSO.   Otherwise could end up "chasing your own tail".

Share this post


Link to post
Share on other sites


@davewantsmoore - Great work - pulling out the DEQX instructions (section 13.6 etc)

I must admit I haven't referred to them in years - possibly a refresh required!

 

DEQX Speaker correction with the mike at the LP changes things - I have some questions but they're not relevant to this thread.

 

cheers

Mike

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×