Setting up 4 subs and phase alignment...

[jtalden]

These are excellent measurements. SPL, XO delay timing and overall performance all looks good and similar to the reference setup. I am curious to know if you hear and difference.

[Using acoustic timing on the FL, FR channels (measurements 3 and 4) only shows how well the mic was centered. I has no other value in this case.]

Changing the XO filter frequency, or the filter slopes, impacts the delay timing needed for the XO handoff. The SWs do appear to be delayed significantly, but the SPL and phase transition from SWs to mains is very smooth. From this data we can't confirm the timing, but from the smoothness phase rotation, it appears to be set correctly.

If you wanted to actually confirm the delay setting then the measurement set needs to be as detailed in Post-18. The 3 measurements before Dirac shows us how well we set the timing prior to Dirac. You have adjusted this timing accurately before so just do that again. I can confirm that 'before Dirac' delay setting if you like. The 3 measurements 'after Dirac' show us if the Dirac process changes the timing significantly as it applies EQ. I don't know if Dirac ever impacts the timing, hence this suggestion. If others know that it will not be impacted then only the FL and FR full ranges sweeps are needed so you can compare the results to you reference setup.

Just to clarify, I noticed that the SWs trace in this data was done using the LFE channel. That was good for the initial experiment to check how well the 4 SWs were timed to each other. This is not the correct way to do it for the purpose of checking the SWs delay (distance) timing however because the XO impacts the timing and the LFE channel bypasses the XO. I noted what measurements are needed in Post-18. When measuring the SWs use the LF (or the RF) channel and just mute, or disconnect the main speaker. When measuring the FL or FR main speaker just turn off the SWs. Leave all XO and other settings active just as you intend for listening. Please use full range sweeps for the SWs as well as the mains. The added noise on the impulse is not an issue. Again, I see nothing here suggesting any significant timing issues with this setup it is fine to just start the listening evaluation.

I just had a thought:
Since you indicated interest in evaluating bass impact of this new setup, I have another setup you may also want to try for comparison. I would need the 3 measurements of Post-18, Either 'Before Dirac' or 'after Dirac' to determine an alternate timing. I tried this timing approach in my system and it did changed the bass impact in my system. I don't know if you will like it, or not, but it is likely to sound different. It only requires changing the SWs distance. It still retains the same SPL support in the XO range so there is no change in Dirac required, although, Dirac can be rerun if you like. The change results in a crossing situation of the phase at the XO point resulting in a little less group delay and less total phase rotation. I think of your current settings as being a more conventional target, but there is a tradeoff of issues that makes it difficult to say that one approach is better than the other - again, it's just a thought.

 

[Sonnie Parker]

Thanks ... I can't say that I hear a difference really. I may actually be hearing too much of the subs now... if that makes any sense. I know I feel more, and the sub volume is not quite as boosted as it has been previously. I may have tuned it a little differently than previously as well, but I'm not sure if I like them where they are now or not yet. At first I was thinking I did... then after I listened more, I have doubts. I need to listen more. I may also need to add the feet back to the front subs to see if that helps any.

When measuring the SWs use the LF (or the RF) channel and just mute, or disconnect the main speaker. When measuring the FL or FR main speaker just turn off the SWs. Leave all XO and other settings active just as you intend for listening. Please use full range sweeps for the SWs as well as the mains.

Gotcha... I think I read right thru that part.

I just had a thought:
Since you indicated interest in evaluating bass impact of this new setup, I have another setup you may also want to try for comparison. I would need the 3 measurements of Post-18, Either 'Before Dirac' or 'after Dirac' to determine an alternate timing. I tried this timing approach in my system and it did changed the bass impact in my system. I don't know if you will like it, or not, but it is likely to sound different. It only requires changing the SWs distance. It still retains the same SPL support in the XO range so there is no change in Dirac required, although, Dirac can be rerun if you like. The change results in a crossing situation of the phase at the XO point resulting in a little less group delay and less total phase rotation. I think of your current settings as being a more conventional target, but there is a tradeoff of issues that makes it difficult to say that one approach is better than the other - again, it's just a thought.

Sure... I would not mind trying it. I'll get those measurements a bit later tonight.

 

[Todd Anderson]

Great thread! Sonnie, I have room size envy!

 

[Sonnie Parker]

Yeah... lol... I had that same envy when I only have half of the garage, which is why I tore it out, then waited for Angie to tell me I could have the entire garage. Actually she insisted, cause she was tired of not being able to escape the home theater being in the great room. The plan worked perfectly.

@jtalden ... I believe I have these right... subs all off, measured the mains with timing. Then turned subs all on and right main off, but kept the left main on for timing and measured the subs thru the right main that was off. Of course you can see these are all post Dirac Live.

 

[Sonnie Parker]

I am about curious enough to try adding the Dayton 18's back in here in the front corners, although that would probably defeat the purpose of having the clean SB16's in here. What would be nice is to have them for movies only, but trying to get a smooth response with and without them would not be so easy. Leaving them off during music would not be difficult since I have to manually cut the amps on for the 18's. Then again, they are sealed, so they might blend in well enough with the SB16's. Oh wait... that's why I have more than one preset with DL... I can tune to both.... duh.

It's hard to say it, but I think I might actually like the less cleaner sound (if that is what it is) of the Dayton 18's. Then again... the clean sound could grow on me, since I know it is more accurate being that it is cleaner. It might be a good test to bring them back in where they were,... measure them and compare the distortion levels in each to see if that is what I am noticing.

 

[jtalden]

The data looks good. It's just what I needed. I will analyze it tomorrow.

 

[Sonnie Parker]

I turned each sub down from -10 to -12 and put the feet back under the front subs. I think I had it just a tad too hot previously, and maybe decoupling it from the floor actually helped some too.

Regardless, it sounds incredibly good... I did NOT want to stop listening... over 3 hours of solid music... uhhh... music Nirvarna for sure.

However, that won't stop me experimenting... might squeeze a little more out of it. Wish some of the guys could come hear it and tell me what they think.

 

[jtalden]

This setup, as measured, is the reference setup for the analysis. First, the FL and FR measurement impulses were adjusted for mic centering and the 3 impulses were then shifted to 0 ms. A + B Arithmetic was used to create the overall FL and FR SPL responses (Traces 4 and 5). Looking below at SPL chart we can see the crossover range is roughly 30-200 Hz providing about 30dB of SPL rolloff. The SPL support in the XO range is very good indicating favorable XO timing. We see indication that that phase from 40-65 Hz is less favorable as the SPL falls below the SWs SPL level. Room influences normally result in irregular SPL support in the XO range so we are looking for the most favorable situation.

Below, an indication of direct phase timing is shown by applying a 5 cycle FDW to the data. The tracking is reasonably good from 70-200 Hz. Note that the SWs (blue) track a little high (advanced) overall and we can see why the SPL support in the <60 Hz is lacking.

Below is the steady-state phase situation at the LP. The FDW was removed and a 1/12 smoothing was applied just to make the overall trends easier to interpret. With these settings we find the FL and FR mains tracking very closely to each other and both showing a 2 phase flips; 68 Hz and 105 Hz due to room influences. The SWs also have a flip at 120 Hz. Looking at the overall tracking the same trend can be seen. The SW are slightly advanced overall. [Most setups will see a much more chaotic situation with the 2 mains having very different phase responses due to an asymmetric setup in the room. The FDW filtered view is thus most often very helpful in seeing the overall trends.

Below, for comparison, the timing of the SWs was adjusted to provide 1 ms more delay. This provided visually more favorable phase tracking. Another 0.5ms may be even more favorable, but was not analyzed.

While this adjustment looks slightly more favorable on a phase chart, I consider ±1 ms to be a trivial difference. It provides no significant impact to SPL. As stated, the reference settings are very favorable and delaying the SWs by and additional 1 ms (-1 ft distance) is a change without distinction.

There is an optional setup that I will document later today.

 

[jtalden]

Alternate Setup
There is a small discrepancy in the slopes of the direct sound phase tracking noticed in the reference setup between the SW and the mains. This is more obvious when the phase is crossed at the 90 Hz acoustic XO frequency. It is thus advisable to investigate if closer phase tracking is possible with the SWs polarity reversed.

Below is the indication of direct sound and steady-state phase tracking with the SWs polarity reversed and their delay timing adjusted by -4 ms (+4.5 ft distance) from the reference setup. The tracking is still not ideal, but it is visually a little better than the reference or the adjusted reference setup. Now the tracking deviation is more in the 140-200 Hz range.

Below is the SPL impact of this setting vs the reference setting. This setting provides stronger SPL support in the 40-63 hz range and less support in the 63-80 Hz range. On balance there is a tradeoff in this regard as expected.

Even when there is a relatively trivial SPL tradeoff of several of us have experienced a very noticeable difference in the sound quality in the bass range with relative polarity reversed. You may want to try this setup and see if it makes a difference for you as well. If so, just choice the setup that sound better to you.

 

[Sonnie Parker]

Very interesting analysis... thank you for all the info.

So if I invert the sub's polarity... easy to do with the SVS sub app settings... how can I tell what -4 ms (+4.5 ft distance) will equate to via phase adjustment, since I can't adjust it in the M17 menu and I don't have the DDRC connected. Or is there a way to see this adjustment in REW. Each measurement does show the delay in ms, so I suppose I could adjust the phase until I see the delay reduce by -4.

Coincidentally, I fixed a bad response dip with Audyssey several years ago by setting the front subs at +5ft distance over the rear subs. Completely different setup than what I have now, but it worked. Audyssey allows manipulation of distance post processing.

I would like to try it and see what it sounds like, and if I can discern any differences.

 

[jtalden]

I take it from your question that Dirac will not allow changing the SWs distance after it has been run. The SW phase setting is unlikely to adjust that far and I would expect any setting above 0° is adding SW delay not reducing it. Can you just set the SWs distance in the M17 and rerun Dirac? That may replace the Dirac Settings for your current setup though? Maybe the M17 allows you save all the M17 settings into a computer file that can be recalled later? Another box is the only other thought, but it would be necessary to delay all the main channels with it rather than the SWs.

 

[Sonnie Parker]

Correct... if DL is set to ON in the M17, it resets all distance settings to 0. No way to change it.

I guess I am thinking backwards... delay on the sub will make it farther away. We delay the closer subs with phase, so we are adding ms to the delay. If we add more distance, we are telling the system to reduce the delay to make it seem closer, which we can't do from 0°.... as you stated.

The only option would be the miniDSP box and connecting the mains up, which I may do. I'll have to order some phoenix connectors for my balanced cables. I used RCA's previously with it, so never got the phoenix adapters.

 

[jtalden]

Since Dirac set a favorable delay with the SWs at the initial polarity, it should also set a favorable delay with the SWs polarity reversed. That would be my expectation. We could confirm that with 3 REW measurements after it is run. It would be tedious however rerun Dirac if you want to go back and forth between setup options for listening evaluations/demonstrations, but that may be the only other option without adding the box.

The box should work fine. It would allow you to switch back and forth in a relatively short period of time to decide if one of the 2 settings sounds favorable. If you settle on the inverted SWs option then the box can be removed and Dirac rerun.

 

[Sonnie Parker]

I could leave the one setup as I have it on Preset 1 of DL... then change polarity of all 4 subs, then set the new DL processing on preset two using the same target curves as slot 1, but as you say... comparing would be a bit of a hassle having to change the polarity back and forth on all 4 subs. It certainly would not be a flip of the switch comparison.

With the box, the preset can actually retain the polarity setting, so indeed it would be as simple as swapping from one preset to another... which can be done with the remote... switch the M17 preset and switch the miniDSP preset, then listen. It would not be instantaneous, but it would be within a 10 seconds or so. Actually I could setup a Macro and probably get it down to 4-5 seconds. I think that is what I will do. I'll get some Phoenix connectors ordered tonight via Amazon and hook the DDRC back up next week and see what we can come up with for comparison.

 

[jtalden]

That should work well. I'll be interested in your results.

 

[Sonnie Parker]

I ended up ordering the sets from miniDSP... they were considerably less than Amazon and shipping time is about the same. Should have them next week some time.

This will also allow me to hook back up my 18's and have a preset for movies with them playing... not that I need them, just hate to see them laid to waste, as they are hard to sell when there are no boxes and the shipping would be ridiculous anyway, so I may as well put them to use, and on movies, I don't care if it ain't that clean... I want LOTS of rumble and impact... the more the better.

 

[AustinJerry]

Just curious, why does Sonnie's impulse look different from my impulse? Sonnie's impulse has a jagged line, while mine is a smooth line. Is this a REW measurement setting? Which is correct?

I posted a question regarding what could make an impulse response appear jagged. JohnM says that the jaggies are noise. In REW Preferences, View tab, check to make sure you have the setting "Use Anti-aliasing for traces" checked. If it was un-checked, take a look at your traces after enabling the setting to see if they look different.

 

[Sonnie Parker]

Thanks for being inquisitive about that issue Jerry.

Seems odd that it only shows up on full range measurements.

 

[AustinJerry]

You could always ask a question yourself. Here is the discussion:

https://www.avnirvana.com/threads/d...uce-different-looking-impulse-responses.5729/

 

[dandi36]

Hi Guys ,

very interesting post !! great work.

i am unfamiliar with the phase tab analysis , usually i align the subs using the impulse tab overlay with a separate measurements(with timing reference).

can you please further explain the principle of using the phase tab with FDW and its benefits ?

i have download the Sonnie's REW measurements ,but when overlay them at the phase tab - i just see the FR and the FL - don't see the SW,can you please advice on that ?

finally, i have always use the "sub distance tweak" (adjusting timing between the mains and subs) till i have got the flattest FR at XO region. i have read many times that you can have a very flat FR but still be off by one cycle (hence effect badly the sound quality and not being aware of that from the "graph") - what do you think of that ?its seems to me that this method of checking phase relationship between the mains and the subs -could help in that region .

many thanks guys

 

[Sonnie Parker]

Welcome to AV NIRVANA dandi... maybe jt or Jerry can answer your questions, as I'm not all that familiar with the analysis myself.

An update to this thread... what happened? Super crazy business happened. By the time I got the cables in our Fall business exploded and I had zero time to do anything but work. Our online business went crazy too, so it was overwhelming for us to handle it all, and it kept me busy day and night, and weekends. So I figured after the end of the year it would slow back down and I'd get caught up in my room. No such luck... in February, it exploded again... then COVID happened and as you can imagine, it caused the atomic bomb in the firearms industry. I'm not complaining by any means, but it has wore me out guys. I think we are hopefully staffed up pretty well now, and it has calmed a bit, so maybe, just maybe I can get back in my room and get some things setup.

I still have cables in the box that have been there now for over 6 months. And no doubt I have lost my thought process on what all I was doing here. Over the last few weeks I have been looking at the new processors that have will have the new Dirac Live Bass Control, but the only unit with it currently in production is a $20K+ StormAudio, which is more than I can stand. It looks like about the only promising unit that has at least 3 sub pre-outs (which I would need for my 6 subs) is the Monolith HTP-1, but I'm not sure when they'll have the Dirac Bass Control implemented in that unit. Their next release is slated for June, but I don't think DBC will be installed in it on that release. This would eliminate the need for separate units and would take care of all the timing between the mains and subs. However, if I can get it to work for me with the miniDSP unit, although it would be manual, it would no doubt mean a substantial savings.

 

[dandi36]

Thanks .its Very nice here!

btw, if this unit have no option to set each sw separately( delay, trim etc ...) , I am not sure it will serve your goal . Need to verify that .

 

[JStewart]

This would eliminate the need for separate units and would take care of all the timing between the mains and subs. However, if I can get it to work for me with the miniDSP unit, although it would be manual, it would no doubt mean a substantial savings.

$499 for Dirac Bass Control for multi-sub now? In addition to a processor that will use it. MiniDSP and aligning subs with REW looking good at the moment. Especially if Dirac Bass Control is only serving to automate what we already do. At least insofar as aligning the subs to each other is concerned. And, at least in my case, when I used the REW alignment tool to check what Dirac had done with subs to mains timing I found that Dirac had made the best timing choice there.

 

[AustinJerry]

I agree that $4K for the HTP-1 plus $500 for the DLBC is getting pricey. I am only interested in bass response at the MLP, so a solution that produces more balanced bass cross the entire listening area is not high on my list. My results with Dirac Live ver 1.0 (MiniDSP 88A) with a 2x4 to consolidate my four subs is excellent. I will need serious convincing before I pay that much money to replace my setup. However, I remain open-minded and am following the HTP-1 thread on AVS very closely.

 

[dandi36]

$499 for Dirac Bass Control for multi-sub now? In addition to a processor that will use it. MiniDSP and aligning subs with REW looking good at the moment. Especially if Dirac Bass Control is only serving to automate what we already do. At least insofar as aligning the subs to each other is concerned. And, at least in my case, when I used the REW alignment tool to check what Dirac had done with subs to mains timing I found that Dirac had made the best timing choice there.

Hi JT and Jerry,

When you have spare time i will really appreciate if you can address my questions and share your vast knowledge .

thanks