Finding Subwoofer

[marcl]

Oct 3, 2020 10:46:07 GMT -5 ttocs said:

Oct 3, 2020 8:26:06 GMT -5 marcl said:

It's remarkable what you've been able to achieve with position and polarity ... and without room treatment too!

Most significant is the lack of deep nulls.  Even the narrow one above 100Hz is gone.  Dirac has so little to do you'll hardly get your money's worth 

Interesting about the effect of objects in the room.  Years ago I emptied a couple of desk drawers that were filled with paper and removed a cabinet from the room.  My transition frequency dropped about 10Hz as did the location of two nulls between 100 and 200Hz.  This is because acoustically it appeared that the room's volume increased a bit and some reflections changed.

It's been a very good learning experience for me. But there's something that is bothering me, the delay. I don't yet know what Dirac will do with the amount of delay I've had to employ to get these results. I hope it doesn't throw off the lip sync.

Here are the settings in miniDSP:

Notice also the Gain varies a lot. I had the subs gain matched before venturing on this odyssey, but found that using gain helped where nothing else would. I will take the time to lower the gain so nothing is above 0.0dB on the miniDSP. In a previous test I found that if the gain was higher than 0.0dB, the subwoofer's gain did a better job, but I'm not expecting that to be the case every time, so I may just have to adjust all those settings lower by the same amount.

Here is a comparison of plots from before S3 was moved from Position C to Position L. Notice that pretty big dip in the 90Hz range.
010022  S3 is at Position C.


010031  S3 is at Position L.


010012DCH Here's the one from a couple days ago for comparison.

I think the final tweaking of Gain and Delay based on measurements is inevitably going to be a bit of art.  But honestly, I would take your results even without Dirac as that is an extraordinarily flat response for subs.

So for delays and lip sync, I would guess it won't be much of a problem.  Dirac throws about 17ms latency into the audio stream on its own.  That's likely to be more significant than miniDSP.  But at least it will be consistent so you could tweak it in the processor, right?

[ttocs]

This is something I searched for but couldn't find, so I made a video to show an easier way to figure out how to quickly adjust the delay for multiple subwoofers. I used RTA and Generator in REW while adjusting the Delay in miniDSP and watching the resulting live waveform. It's just for getting close enough before doing the fine tuning the usual way.

[marcl]

Oct 5, 2020 11:08:31 GMT -5 ttocs said:

This is something I searched for but couldn't find, so I made a video to show an easier way to figure out how to quickly adjust the delay for multiple subwoofers. I used RTA and Generator in REW while adjusting the Delay in miniDSP and watching the resulting live waveform. It's just for getting close enough before doing the fine tuning the usual way.

That's really interesting.   I like the fact that you can see the effect in real time and work toward the most even response ... which may not be when the subs are exactly in phase.  Adjusting more than two might be tricky.

So this demo uses the miniDSP 2x4 HD.  If you have a non-HD miniDSP 2x4 the range of delay is only up to 7.2ms so you might need to do some physical distance adjustment, moving one sub roughly 1ft per ms..

[ttocs]

Oct 6, 2020 13:52:29 GMT -5 marcl said:

Oct 5, 2020 11:08:31 GMT -5 ttocs said:

This is something I searched for but couldn't find, so I made a video to show an easier way to figure out how to quickly adjust the delay for multiple subwoofers. I used RTA and Generator in REW while adjusting the Delay in miniDSP and watching the resulting live waveform. It's just for getting close enough before doing the fine tuning the usual way.

That's really interesting.   I like the fact that you can see the effect in real time and work toward the most even response ... which may not be when the subs are exactly in phase.  Adjusting more than two might be tricky.

So this demo uses the miniDSP 2x4 HD.  If you have a non-HD miniDSP 2x4 the range of delay is only up to 7.2ms so you might need to do some physical distance adjustment, moving one sub roughly 1ft per ms..

The video demonstrates combining a third sub with a pair that's already been matched up.

I started this whole thing with one subwoofer. Found a spot that worked as well as possible, then worked on subwoofer 2. Once I had two subs to work with, I'd start with delaying the closer one. This method will get things close but because it's measuring peaks, it needs to be refreshed a few times during the process. When the two subs are happy is when I add the third. For this, all three subs are playing pink noise but I'm only adjusting the third sub.

It behooves the user to also try things the other way around. Take sub1 and sub3 and try to match only those two together, then add sub2 and see if you come up with the same or a different result. This is how I reduced the amount of delay by a few milliseconds. Why? I don't know. I don't understand enough about this to know. Going back and forth is a much longer process. So that's why saving LOTS of time with what is shown in the video helps with sanity.

[marcl]

I optimized my bass response and did a new Dirac calibration yesterday.  All went really well!   Here are the details of the bass optimization of the Fronts incorporating subs and Magnepan DWMs.

In addition to having two subs connected to a miniDSP 2x4, my system also has two Magnepan DWMs (Dynamic Woofer Modules) that I use to smooth the bass response of my Left/Right 3.7s. The DWMs respond from about 40-200Hz, and they're essentially small sections of the woofer design from the $14,450 Magnepan 20.7. They can be used in various ways, such as to provide bass for limited bandwidth speakers like the CC5 center, or the MC1 wall-mount speakers. Used with large speakers like the 3.7, they can be run in parallel with the left/right speakers ... if your amp doesn't mind the 2ohm load. You can use two DWMs (one per channel), or you can use a single DWM since they have two independent interleaved voice coils driving a single diaphragm. They are relatively small (19.25Hx22.5Wx1.25D inches) and can be placed in optimized positions relative to the main speakers. And BTW, if your amp is not up to the 2ohm load, you can split your left/right channels and power the mains and the DWMs separately (as I do)

This brings me to the topic of alignment. I don't have a way to independently adjust distance/time alignment between the 3.7s and DWMs because I'm using Dirac, and because Dirac sees each 3.7/DWM as a single speaker. This is great because Dirac corrects the combined response. But how do I optimize the coupling of the two? I use two measurements in REW: first I align by comparing Impulse Response of each 3.7 and its DWM using a sweep only in the bass range (i.e. 30-100Hz), and then I optimize by measuring the combined frequency response (one channel at a time) and moving the DWM a few inches at a time. Generally, the Impulse Response alignment gets me to within 1ms and determines the DWM position relative to the front/back of the room. Then I move the DWM left/right relative to the side walls to get the best combined response. Moving closer to and possibly directly against the side wall tends to reinforce lower frequencies, while (in my room) positions 3-4ft from the side wall reinforce frequencies around 100Hz.

You could also use the alignment method ttocs shows in the videos above. But instead of using the miniDSP HD delay as the variable, you could move the DWM and check the RTA response as you go (maybe engage the help of a friend!)

Using the DWMs this way reduced the peak to null range of my left/right speakers from 22db down to 15db. More significantly, the improvement reduced the cancellations which would be difficult for Dirac to correct. The resulting response allowed Dirac to just pull down the peaks with very little boost in the bass range.

So if a two-way splitter is useful, why not get a three-way splitter and make use of Input 2 on the miniDSP to provide bass below 35Hz to the left/right channels? And so I did. The third output of each left/right splitter is combined with a Y cable and goes to the miniDSP Input 2. Center Sub output (LFE only) goes to Input 1. In the miniDSP Routing block I send both Inputs to both sub outputs.

To limit the left/right channel signal to the subs to only below 35Hz I use the Parametric EQ block for Input 2, so this happens before combining with LFE and routing to the subs. But it says "Parametric EQ"? Yes but, you can use the Biquad Calculator in the plugin to get coefficients for a LR 48db/octave Low Pass Filter at 35Hz. Just copy the four sets of coefficients to the Input 2 PEQ Advanced section and the LPF appears, limiting the left/right sub response to below 35Hz.

The ultimate result is, Center Sub output is LFE-only to the subs, full LFE range up over 100Hz then 12db/octave rolloff.  Bass Management for all speakers goes to the left/right Fronts, set to Large, full range 16Hz on up.

And so pictures. No PEQ on the first three traces; Dirac on the bottom trace; all with Variable Smoothing. (Sorry I didn't save the 3.7 measurement 30-300Hz, but you get the idea)  The diagram shows the wiring.

[ttocs]

^^^^^^
So, anyone with a philips screwdriver and a Langstrom 7" gangly wrench can do this? ?   (please, somebody, guess the reference)

Very nice! And with very good results! I almost understand it (just kidding).

This points out how delay can be achieved. If you can't raise the overpass, just let some air out of the tires. It should be noted that not everyone has the option of moving subwoofers or woofers, but even moving a little can have an impact of getting better results with correction.

And don't underestimate the effect of rotating a subwoofer in all directions. My subs have a down-firing driver, and a front facing passive radiator, as such - they are directional, as my measurements have proven. In one spot I got the best result with one of the subs when the passive radiator faced the wall, but I got a better result when I moved the sub 1-1/2 feet along the wall and rotated it 90 degrees.

[marcl]

Oct 7, 2020 11:35:55 GMT -5 ttocs said:

^^^^^^
So, anyone with a philips screwdriver and a 7" gangly wrench can do this? ? 

Very nice! And with very good results! I almost understand it (just kidding).

This points out how delay can be achieved. If you can't raise the overpass, just let some air out of the tires. It should be noted that not everyone has the option of moving subwoofers or woofers, but even moving a little can have an impact of getting better results with correction.

And don't underestimate the effect of rotating a subwoofer in all directions. My subs have a down-firing driver, and a front facing passive radiator, as such - they are directional, as my measurements have proven. In one spot I got the best result with one of the subs when the passive radiator faced the wall, but I got a better result when I moved the sub 1-1/2 feet along the wall and rotated it 90 degrees.

Okay, okay I did use the laser measurer a little bit 

Yeah so I point to two things here:  first, you can use speakers in the "woofer range" to smooth the mid-upper bass and save the subs for what subs do well ... thereby giving you very nice front channel bass to use for Bass Management; second, moving a separate woofer or sub a little bit can make a big difference.   My DWMs ended up about a foot and a half behind my fronts initially, then I moved them +/- another foot and a half closer or away from the side wall to optimize.

But in the end, let's use our ears AND our computers and free software .... "doveryay, no proveryay"!

[ttocs]

^^^^^^ reeThay toogesSay ?

[marcl]

Getting good bass in a room involves a complex mix of factors. Speakers and modal resonances dominate below about 200Hz. PEQ and DRC can mitigate a lot of issues, but not all. It's always best - once you bought the best speakers you could afford - to pay close attention to placement (since that doesn't cost anything) and then consider room treatments to absorb reflections below 200Hz and especially below 100Hz. The latter being VERY difficult to implement.

So I'm wondering, has anyone tried and had success with pressure-based absorbers such as membrane or Helmholtz bass traps? If so, how many does it take to reduce resonances below 100Hz by as much as 10db?

[marcl]

Interesting interview with Todd Welti and Kevin Voecks from Harman on multiple subwoofers. Note what they say in the section on listener preference in shelving and tilt filters:

"Subjects were allowed to adjust shelving filters in real time as they listened to several different programs in our reference listening room. The filters were: a bass shelving filter at 105 Hz, and a treble “tilt” filter at and above 2.5 kHz. There was a fair amount of variation from subject to subject, but if you averaged it all out, you get a bass boost of around 6 dB and a gently rolling off high end, around -2.5 dB at 10 kHz."


hometheaterhifi.com/technical/technical-reviews/an-interview-with-todd-welti-and-kevin-voecks/

[ttocs]

Oct 12, 2020 11:26:00 GMT -5 marcl said:

Interesting interview with Todd Welti and Kevin Voecks from Harman on multiple subwoofers. Note what they say in the section on listener preference in shelving and tilt filters:

"Subjects were allowed to adjust shelving filters in real time as they listened to several different programs in our reference listening room. The filters were: a bass shelving filter at 105 Hz, and a treble “tilt” filter at and above 2.5 kHz. There was a fair amount of variation from subject to subject, but if you averaged it all out, you get a bass boost of around 6 dB and a gently rolling off high end, around -2.5 dB at 10 kHz."

hometheaterhifi.com/technical/technical-reviews/an-interview-with-todd-welti-and-kevin-voecks/

I find it interesting that the locations of my three subs are not far off from being the 1/4 room dimension, with some variation for the uniqueness of my space - offset short walls, sloped ceiling, cabinet boundaries, etc. There's one dimension for each subwoofer that's very close to the 1/4 rule.

[marcl]

Oct 12, 2020 20:36:16 GMT -5 ttocs said:

Oct 12, 2020 11:26:00 GMT -5 marcl said:

Interesting interview with Todd Welti and Kevin Voecks from Harman on multiple subwoofers. Note what they say in the section on listener preference in shelving and tilt filters:

"Subjects were allowed to adjust shelving filters in real time as they listened to several different programs in our reference listening room. The filters were: a bass shelving filter at 105 Hz, and a treble “tilt” filter at and above 2.5 kHz. There was a fair amount of variation from subject to subject, but if you averaged it all out, you get a bass boost of around 6 dB and a gently rolling off high end, around -2.5 dB at 10 kHz."

hometheaterhifi.com/technical/technical-reviews/an-interview-with-todd-welti-and-kevin-voecks/

I find it interesting that the locations of my three subs are not far off from being the 1/4 room dimension, with some variation for the uniqueness of my space - offset short walls, sloped ceiling, cabinet boundaries, etc. There's one dimension for each subwoofer that's very close to the 1/4 rule.

Yeah I thought about your room.  I tried the 1/4 rule years ago with one sub and it worked great.  Of course with Dirac or even PEQ, you can go for a position that eliminates nulls at the expense of higher peaks ... since you can more easily bring down the peaks.

The other point here though is that it's once again evident that these "curves" are just the personal preferences of some folks.  There's no psychoacoustics or biology involved, and they are not described as EQ targets (have I said that three times yet?  )

[ttocs]

I've been at the Rel Library doing a lot of quiet reading lately. They've got some good ideas for increasing their sales, and some of these ideas seem very logical. Most of these ideas involve their very famous High Level (Speaker) connection method while setting the attached speaker as Large in the processor.

They suggest a subwoofer dedicated to the Center Speaker, set the Center as Large.
Use one or two subs for the Front Left/Right set as Large.
Use one sub for the Surrounds set as Large, but also use this sub for LFE.
Then I would also presume that if there are Rears to also set them as Large and add another sub and use it for LFE also.
Don't bother with the ATMOS. They didn't say that, but I do. Just use Bass Management and with the two subs for Surrounds/Rears.

A while ago I started using the suggestion from marcl to dedicate LFE to subwoofers that would not be used for anything else, and allowing Bass Management to put the bass for all Small speakers on the Left/Right Fronts. This is a great idea and I had instant great results by doing this! Thanks Marc! Well, what Rel is suggesting is, for the most part, the same principle, but it would mean that my Fronts would no longer be doing anything for any other speaker in the system. Bass Management would need to be on other subwoofers.

The Fronts and Center each have dedicated subs wired using the High Level connection. The subs are supposed to be as close to their companion speakers as possible so delay isn't an issue (I'm not splitting hairs, trying to keep this simple). So, with no LFE to interfere, the subwoofers are helping the companions in only positive ways.

Rel would have you dedicate a sub to the Surrounds, and probably another for the Rears. I don't see as much of a benefit for speakers which are, at best, directly left/right and behind me, especially when these speakers aren't for main dialogue. They play more of a supporting role, and with the speakers being a lot more separated there might be some obstacles with respect to delay, etc, unless the sub is dead center and the MLP is dead center between the Surrounds. This won't work in my room.

So LCR dedicated subs seem like a good idea to me, so I'm going to try it. I'll continue to use the subwoofer group I've dedicated to LFE for LFE, but I'm going to toss the Small speakers - Surrounds, Rears, and Tops, - on to the subwoofer group as well. I want to get a some Rythmik Audio subs for my Front L&R with the possibility of ending up with stacked arrays, but for now I've just got one on order to try out. Then I'll use a tiny Rel for the Center speaker. Should be fun!

[ttocs]

In the quest to find clarity I tried something yesterday that worked very well.

Rel wants us to use their famous high level connection method and dedicate a subwoofer for each speaker or pairs of speakers, which also means setting these speakers as Large in the processor. The Left gets a sub, Right gets a sub, Center gets a sub, Surrounds share a sub and this sub also carries LFE. Rel only carried this through to 5.1, I interpolate this to mean that the Rears would also share a sub and this sub would also carry LFE. The point is to remove LFE from affecting important channels which carry detailed audio, especially the Center speaker. I did this yesterday for the Center channel.

For the last several months I've been using my three subs for LFE only, nothing else. The Fronts are set as Large so all bass management is sent to the Fronts from any speaker set as Small. This was a great improvement in audio quality for the system! But, expanding this idea is what Rel is suggesting.

So I connected my small Rel to my Martin Logan Motif center speaker and there is another improvement. So now I want to remove bass management from the Fronts and dedicate a sub or two just for the Surrounds/Tops - eventually. For now I may go back to sending the LFE subwoofer group bass management now that the center channel has its own sub.

I'm in the process of ordering subwoofers for Left and Right speakers with the primary purpose being for two channel music. But these subs "could" be utilized in possibly a fairly unique way. For two channel they'd be connected via the high level inputs on the subs. In addition they could be connected to the Left/Right Subs outputs and set to Mono for bass management for all the Smalls. This will not affect the Fronts at all, so they'd be happy and the clarity would remain.

So the LCR are set as Large, and each have dedicated subwoofers.
LFE has dedicated subwoofers.
The L&R subwoofers will also carry bass management for all Small speakers.

There's still room for improvement. There always will be.

[Deleted]

Wow, my head is spinning after reading this thread.  I'll try to be brief as possible.  I'm an old guy and been into subs in my systems for years.  The number of subs and their frequency coverage here is way out of sight IMO.  Some simple old fashioned sub talk here.

..... Sub(s) are for reproducing frequencies at and below 80 Hz (at -3dB).  They should play up to and roll off with -3dB's at 80Hz.  Mono for subs.  At my rules here (80Hz and below only) stereo subs make no sense.  

..... Don't separate low bass and LFE bass.  Send it both mixed/mono to the sub(s) equally.  Buy the best sub(s) you can.  Don't skimp on sub(s).

..... Quality systems main speakers are flat down to at least 80Hx (at -3dB).  Bookshelf size are fine if they are very good/strong down to 80Hz. 
      Tower speakers are not necessary as they should be filtered below 80Hz. (-3dB).  Shocked?  Good reason for quality bookshelves (hard to find). 
       Many folks have towers that supposedly extend down to 40, 50, 60Hz and feel it is a waste to cut off/filter/cross the towers at 80Hz and below.  
       Most of these towers regardless of published specs are running out of gas below 70Hz or so.  Top subs are very strong at 80Hz and down.  Do
       not play the lower frequencies below 80Hz thru both the mains and the sub.  All channel bass below 80Hz plus LFE goes thru the sub(s) only. 
       Again, buy a very good sub(s).  Some buy a good sub for lFE and a mediocre sub(s) for main channel bass ..... no!

..... Human ear can determine direction of frequencies above 80Hz, as in all main 5-7 plus speakers.  Mains are for frequencies above 80Hz. 

..... The human ear cannot normally locate the frequencies below 80Hz.  Some mistakenly call this omnidirectional. 

..... Equalize sub(s) and/or move sub(s) for best flat response below 80Hz.    

Comments:  I was fortunate to buy the Emo Reference smaller bookshelf which was exactly the same as their tower in the tweeter and mid/bass drivers.  So it was very high quality in sound, power handling and frequency response down to 80Hz.  It was cheaper than the tower and easier to place.  Many brands don't offer this and one has to go with a tower model.  Some small to mid size towers might have a frequency response down to maybe 45-60Hz and some would feel it is a waste to cut off at 80Hz and thus they have the tower and the sub both playing in that 45/60-80Hz range.  Please don't.  No worries, down in that lower range the performance of the tower is running out of gas.  So we have the THX philosophy here:  The highs, mids, lows and sub all from different sound sources.  Of course the main speakers (at least the front 3) are all from the same brand/series being preferable.  Many folks have excellent 5 or 7 speakers and then pinch pennies on the sub as they consider it just a low end reinforcement.  High sound output, power handling and powerful sub/built in amp are essential for dynamic music and HD/LFE movie tracks.  Omnidirectional is a misnomer for subs.  What people mean is that when subs are correctly crossed/filtered  at 80Hz then one cannot determine the location of the sub.  The low bass is enveloping the way it should be.  When folks have a sub playing up to 100-200Hz
like in  some posts above you can definitely determine the location of the sub.  Usually one will end up with a undefined sloppy bassy mess.  In my relatively small condo living room (13 x 14, open at one side), I have one only but high quality 12" large enclosure 60 lb Outlaw sub.  It is next to the sofa and out 15" front the rear wall and 11" from the side wall. The low end sound is very impressive.  It has no problem handling the LFE bass.      

Just the opinion of this old Nut.        
 

[ttocs]

Nov 17, 2020 3:28:42 GMT -5 @tllfkacn said:

Wow, my head is spinning after reading this thread.  I'll try to be brief as possible.  I'm an old guy and been into subs in my systems for years.  The number of subs and their frequency coverage here is way out of sight IMO.  Some simple old fashioned sub talk here.

Just the opinion of this old Nut.        
 

I hear ya. 

There are several things going on with my journey in all this bass shh-stuff. First off, my room is over 5500 cubic feet of air space, so the needs of this room are substantial to get the same effect as a small room. For the last few years I've had two subwoofers in play. They do a good job, but clearly the room "needs more subwoofer" (think "cowbell) to have more fun with movies. So I played for a week and got an older, smaller sub added to the group and got a really good result, also learned quite a bit.

Second, I've wanted to get a more enveloping sound and feel to the bass from my main L&R speakers, which are very good at going down to 19Hz measured in-room. But, I want to help them out in the lower frequencies and maybe lessen their workload a little by adjusting a couple controls on them. These speakers have dual amps for dual woofers and ARC calibration built-in. While they sound fabulous, I'm wanting deeper, accurate, more enveloping bass for a more immersive feel while listening to two channel music. Dirac has not been an improvement for two channel music as yet. Using the processor and trying everything I can to use subwoofers while adjusting crossovers and such has not yet been able to improve the sound these speakers produce all by themselves. So that's why I'm in the process of experimenting with alternate methods, and there are several ways yet to try, to skin this cat.

Third, this is fun for me. I like experimenting, testing, checking, trying, verifying, disproving, confirming, debunking, etc. I can read what others think, and try what they suggest, but it's up to me to decide if it works for my setup.

Fourth, when I did my little experiment with the center channel last week and realized another improvement, I was elated, until just yesterday when Martin Logan suggested not assigning Large to the Motif speaker without some way of cutting off very low frequencies so if a movie has low bass at high levels in the center channel it won't destroy the small woofers in the center speaker. So there's a couple things I can do without resorting to assigning Small to the Motif. The extra clarity is evident after removing the Center channel from all other speakers and shared subwoofers. So I will keep the Motif set as a Large speaker, and continue to use a dedicated subwoofer, but adding a method of cutting off low bass from getting to its woofers. It's a wonderful and natural sounding setup.

Fifth, while I can be "all in" on a concept, I do have a practical side of me that balks at things I consider to be unnecessary. Dedicated subs for Surrounds and dedicated subs for Rears is too much. If I had a dedicated theater, then maybe, but for now it's just using subs for bass management for these channels and the ATMOS channels and keeping all of these set as Small speakers. But what I do think is "practical" is making sure the Left, Center, and Right channels are each dedicated to those tasks only and run full range set as Large, and not shared with other channels and speakers performing other tasks, along with separating LFE from everything else.

Low Frequency Effects simply destroys the clarity of the bass for the speakers set as Small. In a 5.1 speaker setup, the .1 is LFE. Bass management should be required to be a separate subwoofer in practice. Get a big subwoofer for LFE, and a practical sized subwoofer for bass management. Explosions don't require an audiophile quality subwoofer.

Dolby specs bass for surrounds to go as low as 31.5Hz. This is an easy number to hit for a lot of subwoofers. For the kind of audio content that's in surrounds and immersive channels, sharing a subwoofer amongst these channels is what I prescribe for myself.

At the moment, and subject to change at any other moment in time, my ideal system is as follows:
Front Left full range with companion subwoofer(s).
Front Right full range with companion subwoofer(s).
Center full range with low bass cutoff to center speaker, and subwoofer for low bass.
Surrounds, Rears, Tops, set as Small with shared subwoofer for bass management.
Multiple Subwoofers for dedicated LFE only.

What else am I going to do these days? I've already started baking my own great tasting bread. I make a loaf about every 4-5 days. I've made my own pizzas lately. I finally learned a couple secrets to making great brown gravy just like what I get at Lawry's The Prime Rib!! This was a major breakthrough for me!

I'm drawn to trying interesting concepts new to me. I'm a tinkerer.

[thompson12]

I haven't read this whole thread yet.

I haven't had a chance to try this yet but this guy makes it look easy to setup multiple sub with mini dsp and REW.

youtu.be/_A6gPCczhuU


When I get a chance I'm gona try it with my two revel 15" & two SVS 12" subs




Mitch

[marcl]

Nov 17, 2020 3:28:42 GMT -5 @tllfkacn said:

Wow, my head is spinning after reading this thread.  I'll try to be brief as possible.  I'm an old guy and been into subs in my systems for years.  The number of subs and their frequency coverage here is way out of sight IMO.  Some simple old fashioned sub talk here.

..... Sub(s) are for reproducing frequencies at and below 80 Hz (at -3dB).  They should play up to and roll off with -3dB's at 80Hz.  Mono for subs.  At my rules here (80Hz and below only) stereo subs make no sense.  

..... Don't separate low bass and LFE bass.  Send it both mixed/mono to the sub(s) equally.  Buy the best sub(s) you can.  Don't skimp on sub(s).

..... Quality systems main speakers are flat down to at least 80Hx (at -3dB).  Bookshelf size are fine if they are very good/strong down to 80Hz. 
      Tower speakers are not necessary as they should be filtered below 80Hz. (-3dB).  Shocked?  Good reason for quality bookshelves (hard to find). 
       Many folks have towers that supposedly extend down to 40, 50, 60Hz and feel it is a waste to cut off/filter/cross the towers at 80Hz and below.  
       Most of these towers regardless of published specs are running out of gas below 70Hz or so.  Top subs are very strong at 80Hz and down.  Do
       not play the lower frequencies below 80Hz thru both the mains and the sub.  All channel bass below 80Hz plus LFE goes thru the sub(s) only. 
       Again, buy a very good sub(s).  Some buy a good sub for lFE and a mediocre sub(s) for main channel bass ..... no!

..... Human ear can determine direction of frequencies above 80Hz, as in all main 5-7 plus speakers.  Mains are for frequencies above 80Hz. 

..... The human ear cannot normally locate the frequencies below 80Hz.  Some mistakenly call this omnidirectional. 

..... Equalize sub(s) and/or move sub(s) for best flat response below 80Hz.    

Comments:  I was fortunate to buy the Emo Reference smaller bookshelf which was exactly the same as their tower in the tweeter and mid/bass drivers.  So it was very high quality in sound, power handling and frequency response down to 80Hz.  It was cheaper than the tower and easier to place.  Many brands don't offer this and one has to go with a tower model.  Some small to mid size towers might have a frequency response down to maybe 45-60Hz and some would feel it is a waste to cut off at 80Hz and thus they have the tower and the sub both playing in that 45/60-80Hz range.  Please don't.  No worries, down in that lower range the performance of the tower is running out of gas.  So we have the THX philosophy here:  The highs, mids, lows and sub all from different sound sources.  Of course the main speakers (at least the front 3) are all from the same brand/series being preferable.  Many folks have excellent 5 or 7 speakers and then pinch pennies on the sub as they consider it just a low end reinforcement.  High sound output, power handling and powerful sub/built in amp are essential for dynamic music and HD/LFE movie tracks.  Omnidirectional is a misnomer for subs.  What people mean is that when subs are correctly crossed/filtered  at 80Hz then one cannot determine the location of the sub.  The low bass is enveloping the way it should be.  When folks have a sub playing up to 100-200Hz
like in  some posts above you can definitely determine the location of the sub.  Usually one will end up with a undefined sloppy bassy mess.  In my relatively small condo living room (13 x 14, open at one side), I have one only but high quality 12" large enclosure 60 lb Outlaw sub.  It is next to the sofa and out 15" front the rear wall and 11" from the side wall. The low end sound is very impressive.  It has no problem handling the LFE bass.      

Just the opinion of this old Nut.        
 

Ttocs and I have been corresponding offline about these ideas for a while.  He's had some success with some principles that I definitely agree with, and he's approached the solutions very differently than I have.  We're both learning in the process.

A couple points related to your comments, and ttocs' approach:

• LFE and Bass Management (BM) happen roughly in the same frequency range, but are separate and distinct from each other as well as having different acoustic requirements
• LFE is only the .1 channel content of multichannel sources.  Irrespective of ANY processor crossover setting, the LFE output will be 3-120Hz, and roll off on the high end at 12db/octave.  It's requirement is high output and impact.  
• Bass Management compensates for the low frequency deficiency of some or all of the other speakers.  It's not "just sound effects" but rather could be any sound including music, dialogue, environmental sounds.  It's requirement is high fidelity matched well to the speakers that it complements.  This is even more important with Atmos because the sound objects are placed in the soundfield via "steering" from all available speakers.
• Emotiva RMC/XMC-2 processors give us the ability to solve the LFE/BM problem independently by sending LFE-only to the Center Sub output, and sending BM from speakers designated as "small" to either L/R Sub outputs OR to other speakers designated as "large".
• Handling LFE and BM separately allows us to optimize each.  This is especially important in the case of "small" speakers that must be crossed over higher than 80Hz.  As has been pointed out, frequencies above 80Hz are localizable, despite the fact that the source may still be omnidirectional.  For surrounds and tops that must be crossed over at 100-120Hz, and center speakers that may have to cross as high as 200Hz, subwoofers are not the best solution.

Note that the issues between the LFE requirements and BM requirements are not just frequency response.  They also involve the time domain responsiveness of subwoofers vs other speakers in the bass range.  I have some ideas for tests I can run to illustrate the differences between speakers in this range and how they suit the different purposes.  I'll post soon.

Like ttocs I too have been working on other skills, one of which is creative listening room photography 

p.s. we can challenge each other to the "oldest" or "nuttiest" chair in this forum ... I'm not terribly old, but my room has some truly nutty stuff going on!

[ttocs]

The insanity has begun. Testing starts this weekend, just need to get more beakers and Bunsen burners.
Below is a graphic showing connections and usage.

Multichannel
The first and most important aspect of the subwoofer matrix is having the LFE separated out to dedicated subwoofers. That's been in play for several months, works very well, and there's now more clarity in the speakers designated as Small.

Second most important is the Center channel being separate of everything else. Whether it's a large full range speaker, or in my case a Small speaker that needs a subwoofer. So I've got a dedicated subwoofer for it. The connection method, however, is in a state of flux. There are several connections that will give me the result I want but haven't all been tried yet. Time is required. If the processor was able to direct bass management from individual speakers to companion subwoofers, that would be ideal.

So then there's Bass Management for all the Small speakers. This is directed to probably three subwoofers. One is a dedicated BM sub, the other two are next to the Front L&R speakers, so these two subs need to share some duties. This covers the BM portion of those duties.

Please excuse the crudity of the drawing as I didn't have time to make it to scale. (Doc: Back To The Future) And no, this isn't how the speakers are positioned, it's just a graphical representation. And yes, I know I'm nu.., no I can't say that, I said I wouldn't, uhhh, Crazy, and I'd like to have some Chuc...., no can't say that either, um, Candy , yes that's it, I want some candy. (just for you, and you know who you are)



Two Channel
The Left and Right Front speakers each have a subwoofer adjacent to them. The primary reason for these subs is to augment the bass for two channel music, mostly in the lowest range, but, need to experiment to find out where this leads. The connection will be via High Level method, again, between the speaker binding posts and the High Level Input on the sub. This will not conflict with the BM going to these subs which is connected by an alternate input, which is the LFE input because the processor is doing the crossover work when multichannel content is active. The L&R speakers themselves will not be used for any other audio other than Left and Right channel duties.

So for music, the Left is full range plus a sub, the Right is full range plus a sub. These two channels play this way for movies also, but then need to share the subwoofer with Bass Management. But I must say this in a different way, the Left and Right speakers will get no BM.
============================================================================================

Multichannel gets better clarity, especially the Center channel.
Two channel music gets deeper quality bass that is more immersive feeling.
I get to have fun trying new things, and I frankly don't care which direction any of this takes. I just gotta know.

edit: It must be noted that the pursuit here is NOT for higher output. The goal is to attain a natural sounding deeply immersive feeling. Also, music is more important to me to have quality sound, movies take second place for me.

The learning portion of these exercises can't be overstated. There's so much "cough" "theory" out there with no practical demonstration to back it up. Good. Bad. Whatever. I want to know what happens when things are setup in certain ways, and I want to see measurements when it's germane to understanding results. Example, can the width of a soundstage be measured? Don't think so. So some things are left to descriptors. But what measurements can show is a general improvement or destruction of the audio frequency range.

[marcl]

Referring back to my earlier post about the differences between LFE and Bass Management, here's a comparison of how four speakers respond in the same range from 30-200Hz.  This is Impulse Response, and the "ideal" impulse response is of course, well, and impulse!  It would happen precisely at t=0 with no ringing before or after, and no overshoot into the negative region ... a perfect vertical spike.  But low frequency drivers end up being relatively more massive and large than high frequency drivers, and so they will be slower to respond and exhibit other "imperfections" with regard to Impulse Response.

With proper placement and some PEQ or Dirac Live equalization all four of these speakers can be made to respond dead flat in their response range.  So you could look at the frequency response and say, why not let the subs do the work?  But look at the difference in Impulse Response.  Think about which driver you would pick to play acoustic bass, bassoon, tuba, bass drum or tympani from 200Hz down to 40Hz.  Which driver would you pick to play high impact explosions, thunder and movie effects from 80Hz down to 16Hz?

I can tell you from a couple years of listening, testing and changing configurations, that everything sounds better with the planar dipole speakers to their lower limit, but they really do NOT like movie LFE.  Those of you with good quality full range speakers with cone woofers also probably get better "musical" response in the 40-200Hz range from your woofers than you would from even the best subwoofers.

Food for thought ...