[Fatshaft]

I did some experimenting today after reading what #dominquez1 wrote about phase and subs I decided to do some experimenting…

Here’s my experiment in a nutshell…
I will start by posting my FR for my front subs and my back subs:

The above graph got me thinking!

What I thought was to completely split my front and rear subs “Signal” or what they should receive!
So I split it this way…1 signal for front and 1 signal for back subs with NO OVERLAPPING of the signals.
End result is front subs are getting 10-31HZ and rear subs are getting 33-100HZ.
Here's My MiniDSP settings:

Front...

Rear...

I am completely blown away by the results…I cannot believe how much “MORE” tactile feel I am getting at the MLP!
So I had to film my results to show you what my SPL meter was saying!

I am in awe at the results I am getting with this setup…during the whole process my main goal was getting the Greatest Tactile and Greatest amount of SPL at the MLP.

I’m not done trying to tweak this even further. Right now because I saved my settings on the MiniDSP, it is very easy to go back and forth with my previous settings and this way!
I "Completely" prefer this way for every reason mentioned above!

Regards,[/URL]

 

[LTD02]

had you experimented with reversing polarity to the rear subs prior?


not all your pictures are showing up for me, but it sounds like you had some phase cancellation problems.


splitting up the drivers can solve part of that problem, but then the power of having all drivers at work at all frequencies is lost, i.e. about half the nominal headroom of the system is lost.

 

[notnyt]

Cool, little hump where they meet. If you push em up or down a hz or two it'll be flatter. This is just nitpicking.

 

[yelnatsch517]

What does the FR look like now?

 

[tuxedocivic]

Same thoughts LTD. Photos aren't showing up either.

 

[gworrel]

In addition to the other concerns noted, you might be better off sending the higher frequencies to the front, and the lower frequencies to the rear to avoid localizing bass to the rear. You want it to sound like it's coming from the front.

 

[chalugadp]

In addition to the other concerns noted, you might be better off sending the higher frequencies to the front, and the lower frequencies to the rear to avoid localizing bass to the rear. You want it to sound like it's coming from the front.

I prefer with four subs to have bass all around me. Don't want it hitting me from just front. I wouldn't split it but when you find something you like stick with it

 

[Fatshaft]

had you experimented with reversing polarity to the rear subs prior?

Yes I have, as a matter of fact when reversed in the back my house shakes like crazy vs all subs in phase

not all your pictures are showing up for me, but it sounds like you had some phase cancellation problems.

No cancellations when all in phase
Just has no tactile when in phase

splitting up the drivers can solve part of that problem, but then the power of having all drivers at work at all frequencies is lost, i.e. about half the nominal headroom of the system is lost.

This baffles me cause I have more spl now!!?

 

[Fatshaft]

Cool, little hump where they meet. If you push em up or down a hz or two it'll be flatter. This is just nitpicking.

Ya I can and will make it flatter 😄

What does the FR look like now?

It's on my first post!

In addition to the other concerns noted, you might be better off sending the higher frequencies to the front, and the lower frequencies to the rear to avoid localizing bass to the rear. You want it to sound like it's coming from the front.

You cannot localize the bass at all
I did it that way cause the subs when placed in the front give way more deeper bass than the back does

 

[BassThatHz]

Whenever I've attempted this sort of thing I never ended up liking the results.
Maybe your room lends itself to this config,
but the thought of having subs sitting idle when they could be playing 70hz or 70hz when they could be assisting with 20hz "drives me up the walls".
I've always ran subs in-phase with correct delay and full bandwidth ever since attempting it. I totally abandoned the thought and never looked back.
But that was back when my system was much weaker. Now that I have more bass that I'm allowed to use, maybe it's different now.

Bass is weird that way, unlike a 3-way speaker where all the elements are in use all the time, when you have a sub LP XO'ed at 30hz that sub is only-rarely gonna get used. (Excursion limited range.)
There are only a handful of movies that take advantage of infrasonic-subwoofers.

The subs HP XO'ed at 30hz are gonna get used A LOT! (Thermally limited range.)
The advantage is that you can crank them right up until they melt (ALMOST no worries for excursion.)

But if that is what you want to do, you should have built a 30hz tuned, 100db/watt PA subwoofer (like a pair of B&C 21's, or a bunch of cheap Dayton PA 18's) instead of using expensive 87db/watt car-subs.
You'd gain 13db right there.

Then throw them in some OThorns and gain another 6-20db.

 

[Mfusick]

You had phase issues or poor integration if running different frequencies at different subs helped things you have unwanted cancellation. Try setting some delay on your closest subs to match the further ones away, and remeasure. You should see a noticeable improvements

 

[Fattykidd]

I've been debating trying this same thing in my room. But doing it opposite, with my near field rear subs doing from 30ish Hz down and letting my front subs do from 30Hz up.

 

[yelnatsch517]

Ya I can and will make it flatter 😄

It's on my first post!

You cannot localize the bass at all
I did it that way cause the subs when placed in the front give way more deeper bass than the back does

What is going on with the front subs above 50Hz?

 

[Fatshaft]

The subs HP XO'ed at 30hz are gonna get used A LOT! (Thermally limited range.)
The advantage is that you can crank them right up until they melt (ALMOST no worries for excursion.)

But if that is what you want to do, you should have built a 30hz tuned, 100db/watt PA subwoofer (like a pair of B&C 21's, or a bunch of cheap Dayton PA 18's) instead of using expensive 87db/watt car-subs.
You'd gain 13db right there.

BTH,
Here's what I find fascinating!
My front subs (4x 21's) have 8400 watts of power and are about 9ft away from me!
They are playing 31HZ down.

The back subs (4x 18's) have 650 watts (measured) of power and are about 6ft away from me.
They are playing 33HZ up.

It is mind boggling how much more power is needed for the 21's to keep up with the 18's.
I realize that the reason is because they are playing the lowest notes and we know you need lots of power for the low-end.

My fronts have a low-shelve boost of 5DB's from 30HZ down to keep up with the back subs.
Again...ULF needs boatloads of power!

I will be playing all day today (I love this sh!t) and post more data.

 

[GizzeGutten]

I'm no expert but you might be getting more tactile feel because the air particle velocity is higher when you don't have the same passband radiating from both sides of the room.

All my subs and midbass modules are set up front to maximize the air particle velocity for maximum punch & pound!

One interesting experiment I'm going to try, is to place two subs at opposite sides playing against one another in phase. That should lower the air particle velocity between them and give high SPL but less tactile feel. Then I will stack them on top for the same SPL level at the same position from one side, and see if the tactile feel is higher as the velocity should be higher.

So I think that the tactile midbass punch is a combination of SPL and air particle velocity. If anyone has two midbass modules and would do an experiment like that, it would be really interesting to hear what they find.

--

PS: This is not my idea or theory but something a very knowledgeable individual in the Norwegian forums put me on to.

 

[dominguez1]

Cool @Fatshaft!

Just stumbled across this.
@GizzeGutten, check out my signature for all things particle velocity related

Your Norwegian friend I'm guessing is @Okv here on avs. He has some recent posts in my ulf thread.

 

[dominguez1]

Forgot my signature doesn't show when I post from my mobile...

http://www.avsforum.com/forum/113-s...your-home-theater-ulf-score.html#post23676269

 

[Okv]

It is very likely Gizze is right, the experienced improvement in tactile feel is due to more velocity produced in the new set-up.

Look at the freq resp in the #1 post - they sum up pretty flat, yes?
Anyone should be happy with this response - flat, extends low down, great capacity, what more can you possibly want..
Having the front and the rear units playing separate frequency ranges, will most likely, in most rooms, create a significant increase in velocity potential - and tactile feel.

Reading the #1 post, it seems clear the experienced improvement is very real and so good that known and learned theories for how things should be set up are thrown overboard and ignored, simply because it is obvious that those theories have deficiencies.

The observation is very useful, because it confirms that spl alone is not enough to fully describe the sound we experience.

 

[GizzeGutten]

Cool @Fatshaft !

Just stumbled across this.

@GizzeGutten , check out my signature for all things particle velocity related

Your Norwegian friend I'm guessing is @Okv here on avs. He has some recent posts in my ulf thread.

Thank you, thank you, thank you for that thread . This is something I've been thinking a lot about on how to optimize. I've so far just read the first long post about your investigation into this and will spend the next couple of weeks digging through your sources and set up my own experiments. As your post indicates the proximity effect decrease with distance and this might be why car audio has such insane tactile feel that is hard to recreate even in modest sized rooms. Maybe it has less to do with cabin gain and more to do with air particle velocity.

If we could figure out a way to minimize SPL and optimize tactile feel then we would be able to get extreme tactile feedback with less damage to our hearing. I've even contemplated using hearing protection that isolates linearly to protect my ears while getting that wonderful tactile feedback, haha.

It would be cool to run multiple distances and see if we can regress on the indirect measurements of particle velocity and see how the relationship between distance, SPL and tactile feel relates.

Yes, that would be right. It's @Okv , and I see he has made his presence here So hello to you!

 

[Fatshaft]

So yesterday I did all the tests I can...I kid you not I must've done at the very least 300FR sweeps
All my subs go through a MiniDSP. I have complete control of my subs.
ALL FR sweeps are done with my equipment settings at:
MVL @ -45
LFE trim @ -10
Sub out @ -2
MiniDSP @ -10
(That's ALL negative values)
Amp is a HK 7550HD
Front subs driven by a FP10000Q (bridged and driving 4x 21's at 4200W/channel to an 8ohm load/channel)
Back subs driven by 1 channel of a EP4000 ( NOT bridged driving 4x 18's to an 4ohm load)
SO...My fronts are on 1 channel and my rears are on another channel through a MiniDSP.

My tests had every possible combination: In phase and out of phase, fronts in and out of phase, rears in and out of phase etc...
played with delay from -7.5 to +7.5 in 0.5 increments etc...EVERY single time taking a frequency response!

After seeing all kinds of responses...at the end of the day tried as best I can to match 2 setups:
1. all subs bypassed - playing full range
2. front subs playing 10 to 31HZ and rears playing 33-100HZ.
NOTE...the reason I stayed with the fronts playing the LF (10-30) is because my fronts FR has very good low vs the backs.
The back subs always gave better mid bass (30HZ and up)

Here are the 2 FR responses...I am not saying which is which for a reason...right now...

A the end of this I then proceeded to listen to my goto music and listened to varies songs and all at different levels.
From -20MVL to +15MVL OVER reference.
During this whole time listening to my goto music, I would then switch between both settings (easily done with the MiniDSP)
Finally at 9PM I watched a movie with the wife (Hunter games MJ)
Then a little playtime and finally bedtime

I did not want to post any impressions till the next day (today) after a good night sleep and re-listen to my music with fresh ears!
So back and forth with my settings and listening to my goto music again...

After all that I now have a preference in the 2 settings
It is significant with higher volume!

I hope more people can try this as this has completely opened my eyes on other avenues I will be considering for my next upgrade
I have already named my next upgrade...it's called the "ILMM" (I lost my marbles) upgrade

Kind regards,