Finding Subwoofer

[Germotiva]

I also have problems with the room Gain, despite rolling off at 50Hz. With the midbasses, I have the edge of the flank 24dB / 42DB and + Low Self Filter.
Here normal separation 24dB.

Here is a separation with 42dB.

The 42dB generates electrical vibrations in the signal itself. Not recommended and can not be combated with absorber.

[Germotiva]

The best result I got with 24DB and the Low Self (up to 50Hz) filter. without phase problems.
The result is not good enough for me. I will buy new midbasses. Since I currently inserted the midbasses with Subs-LS (FS28Hz). Therefore, I want to use pure midbasses more suitable.

[ttocs]

Apr 2, 2021 3:08:16 GMT -5 Germotiva said:

I also find a good idea. to reverse the phase in the SUBS. If Dirac rotates the phase at a certain frequency from the measurement. Could this be the mistake. Can you please show a WTF measurement of the subs / 24db and midbasses / 24db.

The phase from Dirac is consistent every time. It uses the first rise as the phase, no matter how tiny it is, and this is always the case.

Also, keep in mind that the "subs" in question are actually the Left and Right speaker channels, there are no subwoofer channels involved. If you look at the wiring diagram, it shows all the subwoofers wired directly to the Left and Right speakers using the Speaker connections. If any subwoofer phase is changed, the frequency response is damaged a lot causing nulls 50-80Hz wide and 40-60dB deep. Each Front speaker is aligned to the subwoofers attached to it.

The Left Speaker Group is connected to only the Left output of the processor, and the Right Speaker Group to only the Right output. No separate subwoofer channels are involved with these.


If it makes it easier for everybody to understand, then just take the subwoofers out of the situation, the same issue that was happening with the subs attached also happens without them. Dirac is not changing the phase of the speaker channel. It might be changing the phase in that frequency range, but the impulse is the same every time.

The issue has been mostly resolved by moving the Speaker Groups. The rest of what remains is needing room treatment, which is what is being worked on for the next few days.

[ttocs]

Apr 2, 2021 3:26:24 GMT -5 Germotiva said:

I also have problems with the room Gain, despite rolling off at 50Hz. With the midbasses, I have the edge of the flank 24dB / 42DB and + Low Self Filter.
Here normal separation 24dB.
View AttachmentView Attachment
Here is a separation with 42dB.
View AttachmentView Attachment
The 42dB generates electrical vibrations in the signal itself. Not recommended and can not be combated with absorber.

ahhhhh, now I understand what you mean when you use the word "separation". You are using 24dB Per Octave Slope, or 42dB Per Octave Slope.

Yes, I have noticed the same thing, that the Slope setting can be destructive with some settings.

[leonski]

don't forget that filters shift phast 90 degrees per 'way'. So if you have a 2-way speaker using a 2nd order crossover, you can start by wiring them OUT OF PHASE because thru the crossover regions, they'll already be 180 degrees 'out'.

[Germotiva]

Ok, I understood it now. Without sub, only left and right together with the same signal, the valley yield.
I would try the absorber room high in the corner.
Either about a part of the corner see green. Or filled the whole corner

[ttocs]

Apr 2, 2021 13:38:44 GMT -5 leonski said:

don't forget that filters shift phast 90 degrees per 'way'. So if you have a 2-way speaker using a 2nd order crossover, you can start by wiring them OUT OF PHASE because thru the crossover regions, they'll already be 180 degrees 'out'.

It'll be an interesting experiment to wire both Fronts reversed and see how Dirac reacts. The phase for both needs to remain matching however, as when I've tried one out of phase to the other it simply is garbage.

[ttocs]

Apr 2, 2021 15:08:42 GMT -5 Germotiva said:

Ok, I understood it now. Without sub, only left and right together with the same signal, the valley yield.
I would try the absorber room high in the corner.
Either about a part of the corner see green. Or filled the whole corner

I've tried filling the corner up to 8 feet, and using 30 inch wide by 8 feet high 4 inch thick panels angled with air space behind, and also tried 15 inches thick by 30 inches wide and 4 feet high, but none of these did much. The corner is all glass. That drawing is showing, for simplicity, no window on the tv wall, but there is a 3 foot wide by 8 foot high window there, and all the windows on the front of the house run from floor to cathedral ceiling, it's all glass. The "hidden" window is exactly that, it is filled in with rock wool and covered with fabric and painted out so it looks good from the outside.

Placing a 2.5 foot by 4 foot absorber panel horizontally above the Right Front speaker and its subwoofer stack has a pretty noticeable effect. 

edit: This is the panel I just "tossed" on top of the Right Speaker Group just long enough to measure what would happen. It was only to find out what would happen to the bass, but is not a viable option, just experimental.
Attachment Deleted

This location with a vertical panel placed perpendicular to the tv wall works really well. This is the best setup I've tried, and I've tried a lot of possibilities, and there are more to test.
Attachment Deleted

I'm going to attempt to document sound panel locations with REW plots to show variations. Might get tedious, but I'll try.

[ttocs]

Absorption Panels: Round 1
No Dirac or other correction is used.
Both Front Speaker Groups are active.
Noise: The kid next door was playing his bongos outside, other kids were in their new swimming pool, the HVAC system is active and so is the fridge, and there has been some emergency vehicle activity tonight. So, not a perfect scenario, but good enough for testing.

I just finished a first batch of panel locations with mixed feelings about the results. I was hoping to get more "action" from flying panels from the ceiling where it meets the Right Wall. From a simple test I did days ago I noticed a little difference with just one panel, so I expected more difference with more panels properly placed, but not so much. There is definite improvement with more panels, more thickness, but not enough to say it's a good starting point to sink time and money into.

I tested 5 different configurations of panel locations with multiple thicknesses for each configuration, 27 measurements.

The biggest bang for the amount of material is with multiple panels on each side of the tv on the Front Wall, standing vertically 48" high, and placed perpendicular to the wall just inboard of each Front speaker.

The panels I made years ago are 5mm Luan board with a single thickness of Roxul, 3-1/2" thick. The panels measure 30" x 48", covered in a loose weave fabric.

The panels are Yellow.
Attachment Deleted

Below is the Before in Teal and After in Red of L+R (both Front Channels together). The Red trace shows a more consistent pattern and all of the energy is higher than the upper frequencies not shown. After moving the Speaker Groups away from the Front Wall a few days ago there is more bass energy overall with too much below 50Hz that I will need to reduce, but I won't take the time to do that until more treatments are in place. Almost all of the extra energy is from the Right Speaker Group. The plot is with no smoothing.


From this result I plan to make two large panels tomorrow. They will be 14" thick, 8' high, and I'm not yet sure if they will be 30" wide or 24" wide, but probably 24". Going from no panels to 2 on each side of the tv (total of 4), recovered the lost energy quite a bit and also provided some gained energy and some smoothing. Going with 3 panels on each side of the tv (total of 6) further recovered more of the lost energy even more and still provided a modest gain of energy and more smoothing. Most of the improvements using panels is above 50Hz. The gain in level below 50Hz without panels was due to moving the Speaker Groups farther from the Front Wall, and remained that way with panels in place. When I use the word "smoothing", I'm using it to mean smaller variations between peaks and valleys, better average, something that "looks" better at a glance.

[leonski]

Apr 2, 2021 15:21:18 GMT -5 ttocs said:

Apr 2, 2021 13:38:44 GMT -5 leonski said:

don't forget that filters shift phast 90 degrees per 'way'. So if you have a 2-way speaker using a 2nd order crossover, you can start by wiring them OUT OF PHASE because thru the crossover regions, they'll already be 180 degrees 'out'.

It'll be an interesting experiment to wire both Fronts reversed and see how Dirac reacts. The phase for both needs to remain matching however, as when I've tried one out of phase to the other it simply is garbage.

Easy enough to try......and may yield a result.....one way or another!

[Deleted]

I have no frequency measurements by Rew or Dirac at this time but just wished to convey that I can't believe I let visual OCD compel me to place my subwoofers like this:



I have been living w/ the above subwoofer placement since I owned Ulberhts and 4-10s. I have never been impressed by the bass. Mind you each tower has 2 12" subwoofers and each 4-10 the surface area of an 18" sub. I take it that the different wavelengths of both the  12s and 10s were causing cancellation being next to one another? Either way, should I be surprised that Dirac Live 3 couldn't correct the issue?

Well I moved the subwoofers to this location and the bass is so freaking loud it pegs my decibel meter at 130 spl which is it's maximum. The subwoofer relocation was worth 5db. Just amazing....



I really think if I go ahead w/ my plans to add 2, 4, or 6 more 4-10s [in a wall  of madness] that the bottom end will be so exaggerated the Parasound Halo A31's 400 watt rms rating to the mains won't be enough. 

My only complaint w/ the new positioning is that though the subwoofers frequency is supposedly omnidirectional when I sit on the couch I can determine the subs location by the left side "pressurization". In other words though I may not hear the location I can feel them.

[leonski]

"Well I moved the subwoofers to this location and the bass is so freaking loud it pegs my decibel meter at 130 spl which is it's maximum. The subwoofer relocation was worth 5db. Just amazing...."
from deleted:

Bass frequencies are LONG. As long as <10 feet at 100hz. And as long as 24' or 25' at a modest 40hz. THAN it gets weird.

I've said this a DOZEN times if once......

Go LOOK at a room mode calculator. One with visual graphics so you can 'get the idea' of the interaction of bass frequencies.....Standing waves produce PEAK areas and DIPS. (suckout)
The HARMAN white paper on subs and sub placement is WELL worth a look.....

Me? I'd be tempted to try a PAIR of subs BEHIND the main listening position.

[ttocs]

Apr 4, 2021 17:40:19 GMT -5 leonski said:

Me? I'd be tempted to try a PAIR of subs BEHIND the main listening position.

I've tried 1, 2, and 3 subs behind, next to, and in front of the MLP sofa. This area is the worst in my big room. It's directly on top of the steel support beam below the floor, and below the beam that supports the cathedral ceiling. I would've thought this would be a great area of the room for subs, but no luck. I did all this exactly one year ago. It was the beginning of my schooling about REW, which took a while for me to get a handle on.

Some rooms do very well with subs behind the MLP.

[Germotiva]

Apr 4, 2021 18:20:43 GMT -5 ttocs said:

Apr 4, 2021 17:40:19 GMT -5 leonski said:

Me? I'd be tempted to try a PAIR of subs BEHIND the main listening position.

Some rooms do very well with subs behind the MLP.

Yes rooms can be difficult. Especially if it is not symetric or the setup not constructed symmetrically.
Sometimes the multi sub listening helps.
@ deleted experiment  in the Rew with Room Size. With the positions of the LS.
Important is the uniform modes suggestion in the room. The JBL document is also interesting.
The best method is DBA Bass or Sba.💪

[Germotiva]

With 8 pieces you would have good conditions. But better for your room more LS. Not because of the volume. but because of the uniform excitation.Try it in the rew time. A beautiful FQ is generated.What is not optimal, is the hole in the right corner🤷‍♂️

[ttocs]

Apr 4, 2021 15:42:59 GMT -5 @deleted said:

My only complaint w/ the new positioning is that though the subwoofers frequency is supposedly omnidirectional when I sit on the couch I can determine the subs location by the left side "pressurization". In other words though I may not hear the location I can feel them.

It's pretty easy to hear and feel sub locations. And yes, it's got a lot to do with the feel of it. When they are in front, no matter which channel they are supposed to be providing bass for it sounds proper, but when they are not in front and if they are on one side or the other it's not comfortable.

[Deleted]

Apr 5, 2021 8:31:43 GMT -5 ttocs said:

Apr 4, 2021 15:42:59 GMT -5 @deleted said:

My only complaint w/ the new positioning is that though the subwoofers frequency is supposedly omnidirectional when I sit on the couch I can determine the subs location by the left side "pressurization". In other words though I may not hear the location I can feel them.

It's pretty easy to hear and feel sub locations. And yes, it's got a lot to do with the feel of it. When they are in front, no matter which channel they are supposed to be providing bass for it sounds proper, but when they are not in front and if they are on one side or the other it's not comfortable.

Ah, thanks for confirming ttocs. 

[Deleted]

Apr 4, 2021 18:20:43 GMT -5 ttocs said:

Apr 4, 2021 17:40:19 GMT -5 leonski said:

Me? I'd be tempted to try a PAIR of subs BEHIND the main listening position.

I've tried 1, 2, and 3 subs behind, next to, and in front of the MLP sofa. This area is the worst in my big room. It's directly on top of the steel support beam below the floor, and below the beam that supports the cathedral ceiling. I would've thought this would be a great area of the room for subs, but no luck. I did all this exactly one year ago. It was the beginning of my schooling about REW, which took a while for me to get a handle on.

Some rooms do very well with subs behind the MLP.

Your findings make sense ttocs
I mean what's the difference if I place the subs in front vs behind if the same distance from the listener to subs concerning wave lengths? Wouldn't they ultimately be at the same phase alignment? 
As an example, and correct me if wrong....
If I place a sub in front of me 10' away or behind me 10' away wouldn't the  same size woofer's wave length be the same w/ respect to phase alignment? 

[leonski]

Apr 5, 2021 11:50:28 GMT -5 @deleted said:

Apr 4, 2021 18:20:43 GMT -5 ttocs said:

I've tried 1, 2, and 3 subs behind, next to, and in front of the MLP sofa. This area is the worst in my big room. It's directly on top of the steel support beam below the floor, and below the beam that supports the cathedral ceiling. I would've thought this would be a great area of the room for subs, but no luck. I did all this exactly one year ago. It was the beginning of my schooling about REW, which took a while for me to get a handle on.

Some rooms do very well with subs behind the MLP.

Your findings make sense ttocs
I mean what's the difference if I place the subs in front vs behind if the same distance from the listener to subs concerning wave lengths? Wouldn't they ultimately be at the same phase alignment? 
As an example, and correct me if wrong....
If I place a sub in front of me 10' away or behind me 10' away wouldn't the  same size woofer's wave length be the same w/ respect to phase alignment? 

True except for THE BOUNCE which will 'cog' with other bounces to produce peaks or dips....and at different frequencies from sub location to location.  

[ttocs]

I have begun adding room treatments to help with specific problems. I have never done this before as a serious effort and have been able to be happy with the sound using only a very minimal amount of absorption panels I made about 6 or 7 years ago which measure 30" x 47". I made them using a method that was easy for me and had the desired effect of quelling reflections. I've used them from time to time to experiment with frequencies in the bass region but never got much of anywhere.

A few months ago when I discovered something that only occurred when both Large Fronts played mono bass while using a Dirac filter. It is a big notch, dip, null, call it whatever makes sense to you, but it can be more than 10Hz wide and 20-40dB deep. While I was able to regain a lot of the lost energy by moving the speakers and MLP, I finally decided to find out what was causing it and see if it could be reduced or eliminated. To that end I went about using material I purchased a few years ago but hadn't taken on the effort to make any panels or traps or absorbers, whatever, until last week.

I chose to make some absorbers in true DIY fashion. Rock Wool, Spray Glue, and Fabric. I made two absorbers that measure 15" x 24" x 71". The rock wool itself is 15" x 47" x 3". The absorbers are 8 pieces thick using one full size piece and a piece cut in half. Then I just layered them by alternating the cut piece on the left of layer 1, on the right for layer 2, etc. The spray glue works very well in binding the layers together, and it doesn't take a lot to do it. Once it's to the desired thickness the same spray glue adheres the fabric to the rock wool. This used 2-1/2 bales of rock wool from the home store which comes with 10 pieces. If these chunks were much larger they'd be too difficult to move as many times as I've done the last few days.

I'll be posting some before and after REW plots along with floor plans showing some of the various placements. Suffice to say for now that no matter where these absorbers are in the room there's a benefit. Most locations provided small changes, which was getting a bit frustrating just seeing the small differences come and go with each move, but finally I got a big change exactly where I needed it to be!

marcl has always been vocal about the 1/4 wavelength placement for absorbers like what I made. I've done some tests using the unopened bales of rock wool with this in mind but wasn't able to see this dramatic difference I found yesterday using the 1/4 wave approach, so it works! The plastic wrapping isn't supposed to be a big issue from what I've read in quite a few posts on the web, but I think it does make a difference without it. Anyway, 1/4 wave is just about where one absorber is and it makes a difference anyone who knows nothing about how to read REW plots would be able to say - wow, that's a big difference.

I have searched and searched for info along with before/after plots and have only found a few sites that have the plots but most do not have exact drawings showing where the treatments are placed and how they are made. So that's one reason I want to post my results.

Orientation matters. Sometimes against the wall is better than a gap to the wall, other times it's the opposite. How tall should the absorbers be? I don't know. I've placed one absorber in a spot, then rotated it, then added the second one, rotate both, then laid one down horizontally, then added the second one, and so on. I tried every combination in each spot that showed some promise. Sometimes it just comes down to what looks better and is easier to live with.

Before I post any results I'm going to make a couple more smaller chunk absorbers because I know I'm going to want to add more and I want to test some other ideas. And along with almost completely fixing that big dip there's a lot of general smoothing above 100Hz that extends out quite a ways.

I'd be interested in seeing drawings and plots showing improvements with room treatments any of you have used. At some point in the future I'd like to explore diffusion, but that's later. One thing at a time.