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Need help with a quad subwoofer setup - Page 2

post #31 of 152
Quote:
Originally Posted by BeeMan458 View Post

As a suggestion, try dumbing it down so those of us without an acoustical degree, can understand what you're trying to share.

(my subs are relatively closely matched as I depend on Anti-Mode 8033S II, MultEQ XT, REW, the HPF and phase control to be my friend)

-

It was a short but succinct summary of the issues with using different subs, here's a slightly longer version.

- nearly all modern home theater subs are equalized
- they are equalized because the enclosures are small
- if they were not equalized then the result would be excessive bass roll off
- so what manufacturers do is get a long throw woofer, a powerful amp and some equalization
- they use equalization to boost the drooping low end, below the frequency at which roll off occurs
- equalization causes phase shift
- different subs have different amounts of equalization because they are using different drivers with different resonant frequencies, different enclosures (vented / sealed) and different sizes enclosures
- sealed boxes will have a different equalization than vented boxes as they exhibit different roll off characteristics (slope)
- therefore each sub model has a different amount of phase shift
- this phase shift starts where the manufacturer starts equalization
- some start at 50Hz, some start at 35Hz or elsewhere
- worst case you have full cancellation if the subs are 180 degrees out of phase at a certain frequency
- most times you will get constructive and destructive interference as phase shift differences are not 180 degrees but something a little lower
- there is no way to fix this with either the phase control on the back of the sub or the time delay on the prepro

It is basically unpredictable when you start using multiple different subs. Sometimes it may work fine, other times it will not. Simplest is to use identical subs, which will always work.
post #32 of 152
Quote:
Originally Posted by Nyal Mellor View Post

- nearly all modern home theater subs are equalized
I'd have to see documentation to support that assumption before I accepted it as gospel. IME few HT subs are internally equalized. As for the phase issue in general, room modes are far more controlling of phase than either the enclosure or any EQ that might be used. Different phase responses using multiple speakers is seldom a problem unless said speakers are placed too close together, which you shouldn't do with multiple subs anyway, as it defeats the purpose of having them.
Edited by Bill Fitzmaurice - 11/3/13 at 7:02pm
post #33 of 152
Quote:
Originally Posted by Nyal Mellor View Post

It was a short but succinct summary of the issues with using different subs, here's a slightly longer version.

Weeeeeeee! Thanks for the much longer version. Sometime more is better than less. tongue.gif

(my layperson's takeaway from your above thoughtful expanded version.....beware of bass-boost)

(curiosity question; have you been to the mixing rooms out at the Ranch? If yes, and you can say, what were your impressions? The reason I ask, sound reproduction wise, how can a plebe nobody expect to replicate what one finds there?)

-
Edited by BeeMan458 - 11/4/13 at 5:40am
post #34 of 152
In addition to equalization (which is common in sub plate amps), the high-pass/rumble filters introduce frequency dependent phase shifts. You can look at phase plots to see what those are. Since they are frequency dependent, they cannot be fixed with delay. That said, with matching subs that have significantly different distances from the listener, it's generally good to time align them separately. For 4 subs, you can use a preamp with 2 sub outputs, and split each for the 2 in front and the 2 in back, assuming each pair has about the same distance.

Audyssey attempts to do some phase correction, but it does this for all subs together, and only lets you adjust delay and gain for separate sub outputs.

I have found that even taking the same model of sub in the front and back of the room, and not matching the high-pass/rumble filter settings on both subs can indeed cause nasty cancellation. Then, going back and matching the setting made it dramatically better. I'm not saying that this happens for everyone.
post #35 of 152
I'm glad we had this conversation. eek.gif

Now I'm convinced I'm hosed. tongue.gif
post #36 of 152
Quote:
Originally Posted by Bill Fitzmaurice View Post

I'd have to see documentation to support that assumption before I accepted it as gospel. IME few HT subs are internally equalized. As for the phase issue in general, room modes are far more controlling of phase than either the enclosure or any EQ that might be used. Different phase responses using multiple speakers is seldom a problem unless said speakers are placed too close together, which you shouldn't do with multiple subs anyway, as it defeats the purpose of having them.

I did say most...

If you get a simple speaker box modeling spreadsheet and plug in the T/S parameters of some common drivers you will see what I mean. Enclosure sizes are smaller than they would be optimally to make the subs fit into domestic living environments and the early roll off is made up for by equalization, with the consequent demands this places on long throw drivers and amplifier power.

Some reading material:
- group delay (another way of looking at the delay of a group of frequencies - i.e. phase shift - generally caused by equalization), bottom of this page: http://www.audioholics.com/loudspeaker-design/powered-subwoofer-testing-outline-and-procedures-overview/powered-subwoofer-testing-the-powered-subwoofer-tests
- a bunch of subwoofer tests, look at the group delay graphs: ]http://www.hometheatershack.com/forums/subwoofer-tests-archived/5747-subwoofer-tests-round-4-5-6th-may-2007-test-summary.html

I've seen / meaured the phase cancellation phenomena when performing acoustic analysis or calibration using multiple different subs enough times to know that it is real...but like I said sometimes you get lucky and it doesn't cause an issue.
post #37 of 152
Quote:
Originally Posted by Nyal Mellor View Post

If you get a simple speaker box modeling spreadsheet and plug in the T/S parameters of some common drivers you will see what I mean. Enclosure sizes are smaller than they would be optimally to make the subs fit into domestic living environments and the early roll off is made up for by equalization, with the consequent demands this places on long throw drivers and amplifier power.
Some reading material:
Before adopting the position of professor you might want to check the credentials of the person you want to school. wink.gif
The quoted links contain inaccuracies, but I doubt the OP wants to go into the fine details, so I won't bother adding to his potential confusion with details that would go way beyond what he's really interested in.
Edited by Bill Fitzmaurice - 11/4/13 at 9:50am
post #38 of 152
post #39 of 152
Quote:
Originally Posted by Bill Fitzmaurice View Post

Before adopting the position of professor you might want to check the credentials of the person you want to school. wink.gif
The quoted links contain inaccuracies, but I doubt the OP wants to go into the fine details, so I won't bother adding to his potential confusion with details that would go way beyond what he's really interested in.

I never intend to 'school' anyone - this is an online forum with many people of different knowledge bases, skill sets, backgrounds, etc. School is such a bad word to me, it sounds almost like bullying, which I detest.

I know enough to be dangerous on speaker/sub design but it's not my specialty, there will be 10,000+ people or more who know more about it that I do.

I was just posting my opinion, backed up with some facts, based on my experiences so far.

I'm not interested in getting into a slinging match. I hope you didn't take my comment personally, it was not intended that way (and neither did it read that way I think).
post #40 of 152
Thread Starter 





Just finished hooking them up an re-running audyssey. I had a good first impression. I tried a few movies that I am familiar with Tron Legacy, Terminator 2 , Alice 2009 and the results were pretty good. On Tron Legacy, the door in the next room was rattling. Never happened before! I am gonna try Super 8 next. I am still to learn about the different settings on the sub. I just followed the little guide that came with it when I ran audyssey so I still have little experimenting to do.
Edited by ahmedreda - 11/4/13 at 7:10pm
post #41 of 152
If you like subsonic and tight, realistic bass, use 14-hi. If you want more power, use 20-low.
Either way, you want the limiter on.
After changing these settings, you need to re-run Audyssey, so it's best to start comparing them with Audyssey off.
post #42 of 152
Thread Starter 
Thanks for your advice. My understanding is that you can't hear the subsonic frequencies so what would be the benefit in directing the power of the amp to try to reproduce them? I have read somewhere that sealed subs (a bunch of them) can be used to reproduce lower <20hz frequencies but I don't understand the benefits if you can't hear those frequencies.

I have been very impressed with the new subwoofers so far. I did not know I was missing that much information with the polks! Room now sounds like a real movie theater. biggrin.gif
Quote:
Originally Posted by rcohen View Post

If you like subsonic and tight, realistic bass, use 14-hi. If you want more power, use 20-low.
Either way, you want the limiter on.
After changing these settings, you need to re-run Audyssey, so it's best to start comparing them with Audyssey off.
post #43 of 152
As you go below 20 Hz, you still experience it as sound, but technically, you "hear" with your skin, rather than your ears. Also, you get more & better 20 Hz, when you move the crossover down. It depends on the room, and it does cost you headroom, so if the lower frequencies aren't giving you an audible advantage, you're better off filtering them out. The best bet is to experiment and see if you think it's worth it for you to spend power on the lower frequencies. One thing to keep in mind is that "low" is a steep crossover slope and "hi" is a gentle crossover slope. The gentle slope gives you a tighter sound at the crossover frequency, but it costs more power.
post #44 of 152
One of the advantages of your subs is that they can play lower and cleaner (less distortion) than most other subs. While this won't be noticed in every movie or in every scene, you probably don't want to limit their extension (by using the 20hz mode) unless you are getting distortion. As you pointed out, we can't "hear" below 20hz, but we can feel it...and that sensation is what makes the impact realistic in movies and music with deep bass.
post #45 of 152
If a train goes past you can can feel the huge weight of it thundering through the ground and up through your body. If it came past and didn't do that it would seem 'wrong', like the train wasn't heavy, when it clearly is.

<20Hz adds this weight to sound reproduction. Yes, it takes a lot of power and displacement to produce a lot of it, but it is awesome and just adds to the realism smile.gif Without it things just seem to be missing something!
post #46 of 152
At this point in time, basshead81 has posted convincing information that a pair of FV15HPs is the minimum one needs to get one to this point: four star or better ULF score.
post #47 of 152
Quote:
Originally Posted by BeeMan458 View Post

At this point in time, basshead81 has posted convincing information that a pair of FV15HPs is the minimum one needs to get one to this point: four star or better ULF score.

most rooms around 3000^3 can get there with Dual PB12+ or PB13U, 2-XV30's, 3- PSA XV15's, 3-VTF15's, 4 HSU VTF-3's or Outlaw LFM-1EX's. My point I was trying to make in the other thread is that if one wants reference level(4 star ULF) down to 15-16hz, with less then 4 subs, that cost under 2k each, you will need to go ported for any room that is approaching 3000^3 or larger. Sealed will not produce those output levels @ 16hz unless were Talking a Pair of SUBM's, Triax's or, Cap S2's. The Rythmik F25 would be close but it will probably take 3. The Nice thing about the FV15HP is that it blows all other subs away in 10-12.5hz output when comparing subs that cost under 2k.
Edited by basshead81 - 11/8/13 at 1:05pm
post #48 of 152
Sorry if you think I mis-posted in my comment as my above was minimum and not intended to be an end all list of possibilities.

You wrote: "The Nice thing about the FV15HP is that it blows all other subs away in 10-12.5hz output when comparing subs that cost under 2k."

Which in my book, my interpretation of your above, is a convincing argument that a pair of FV15HPs is a minimum standard. If I made you uncomfortable with my carried away comment, my apologies.

Just so you know where I'm coming from, what I term "minimum standard", is expectedly, a clean12Hz reproduction at hopefully, reference levels. Your comments showed me that a F25, E15HP combination, more than likely, will not be able to get us to this level of performance. With three XV15s, you're reporting 130dB. Have you measured the SPL output at 12Hz? That's why I liked the XS30, XS15 combination, for the ability to plumb the lower depths. And then I look back at the Rythmik line, with "Servo Technology" and think how much I appreciate the expanded reproduction; clarity.

(and just to be clear, no, my/our listening preferences haven't changed but my ego wants to be able to say that our subwoofer system is reference capable)

I really do appreciate your efforts regarding your help with my indecisiveness in the conundrum while trying to decide between the two stated combinations with the addition of the FV15HPs as an alternative third choice. Two FV15HPs seem to hit the middle ground squarely on all intrinsic points. I just need to do some additional measuring to make sure the room acoustics agree with this decision as the wife is very happy with this choice also.

(as long as the two FV15HPs will do what I want, I'm a happy camper with the choices and will look no further)

-
Edited by BeeMan458 - 11/8/13 at 1:49pm
post #49 of 152
Quote:
Originally Posted by BeeMan458 View Post

Sorry if you think I mis-posted in my comment as my above was minimum and not intended to be an end all list of possibilities.

You wrote: "The Nice thing about the FV15HP is that it blows all other subs away in 10-12.5hz output when comparing subs that cost under 2k."

Which in my book, my interpretation of your above, is a convincing argument that a pair of FV15HPs is a minimum standard. If I made you uncomfortable with my comment, my apologies.

Just so you know where I'm coming from, what I term "minimum standard", is expectedly, a clean12Hz reproduction at hopefully, reference levels. Your comments showed me that a F25, E15HP combination, more than likely, will not be able to get us to this level of performance. With three XV15s, you're reporting 130dB. Have you measured the SPL output at 12Hz? That's why I liked the XS30, XS15 combination, for the ability to plumb the lower depths. And then I look back at the Rythmik line, with "Servo Technology" and think how much I appreciate the expanded reproduction; clarity.

(and just to be clear, no, my/our listening preferences haven't changed but my ego wants to be able to say that our subwoofer system is reference capable)

I really do appreciate your efforts regarding your help with my indecisiveness in the conundrum while trying to decide between the two stated combinations with the addition of the FV15HPs as an alternative third choice. Two FV15HPs seem to hit the middle ground squarely on all intrinsic points. I just need to do some additional measuring to make sure the room acoustics agree with this decision as the wife is very happy with this choice also.

(as long as the two FV15HPs will do what I want, I'm a happy camper with the choices and will look no further)

-

Oh no your good Bee, I think dual FV15HP's is what you will want. I am at 128-130db 30hz-60hz, 118db @ 16hz, 108db @ 12hz with 3 XV15's in a 2400 room. As you can see I am getting some compression but to my ears they still sound clean. I am guessing lower harmonics are approaching 20-25%. If I had Dual FV15HP's I would expect 114-115db around 12hz in my room with a more linear and cleaner respnse, so yea no doubt the FV15HP is clearly on another level. I had a line on a pair of piano black with silver cone for 1800.00(thanks to Dominguez for posting the craigslist link). However I am happy with my setup and I can not see ditching the 5yr warranty for subs with no warranty and going through the whole setup process again. If and when I get a dedicated HT room, I am thinking quad FV15HP's are going on my short list!! Well unless PSA comes out with a Ported version of the Triax!!
post #50 of 152
F25/F15HP does better than FV15HP at 12hz. At 20hz, the FV15HP has the lead (in terms of quantity). As you go higher, they become very similar.
post #51 of 152
Quote:
Originally Posted by basshead81 View Post

Oh no your good Bee, I think dual FV15HP's is what you will want. I am at 128-130db 30hz-60hz, 118db @ 16hz, 108db @ 12hz with 3 XV15's in a 2400 room. As you can see I am getting some compression but to my ears they still sound clean

Thanks for the reply. I checked out the ULF thread, second post and the rigs people had listed for four, four and a half and five stars. For our room size, two FV15HPs will do just fine and blend better then what we currently have happening with three Klipsch subwoofers. Those heavier duty rigs of the four and a half stars or better, go into the "Oh Hell No!" category. Two FV15HPs hit the sweet spot.
post #52 of 152
Quote:
Originally Posted by basshead81 View Post

Oh no your good Bee, I think dual FV15HP's is what you will want. I am at 128-130db 30hz-60hz, 118db @ 16hz, 108db @ 12hz with 3 XV15's in a 2400 room. As you can see I am getting some compression but to my ears they still sound clean. I am guessing lower harmonics are approaching 20-25%. If I had Dual FV15HP's I would expect 114-115db around 12hz in my room with a more linear and cleaner respnse, so yea no doubt the FV15HP is clearly on another level. I had a line on a pair of piano black with silver cone for 1800.00(thanks to Dominguez for posting the craigslist link). However I am happy with my setup and I can not see ditching the 5yr warranty for subs with no warranty and going through the whole setup process again. If and when I get a dedicated HT room, I am thinking quad FV15HP's are going on my short list!! Well unless PSA comes out with a Ported version of the Triax!!

Hey bassheaad - I always see folks quoting numbers like this. How exactly do you measure your output at different frequencies? Sine waves or what?

Sorry if this is something I should already know. redface.gif
post #53 of 152
Quote:
Originally Posted by rcohen View Post

F25/F15HP does better than FV15HP at 12hz. At 20hz, the FV15HP has the lead (in terms of quantity). As you go higher, they become very similar.

Just to be sure, I'm comparing two FV15HPs to the F25/E15HP combination.
post #54 of 152
Thread Starter 
Either one of them should be better than the fv15hp at 12hz even in the one port mode..
Quote:
Originally Posted by BeeMan458 View Post

Just to be sure, I'm comparing two FV15HPs to the F25/E15HP combination.
post #55 of 152
Quote:
Originally Posted by ahmedreda View Post

Either one of them should be better than the fv15hp at 12hz even in the one port mode..

I beg to differ....read the ULF thread and gain some knowledge. The FV15HP is tuned very low(14hz) and will have a 6-8db advantage of its sealed sibling the F15HP around its tune.
post #56 of 152
Quote:
Originally Posted by Alan P View Post

Hey bassheaad - I always see folks quoting numbers like this. How exactly do you measure your output at different frequencies? Sine waves or what?

Sorry if this is something I should already know. redface.gif


Run a REW sweep at max output or use Sine wave test tones in rew combined with a handheld spl meter and add the correction values. Take note you should be able to net another 2-3db output with source content as test tones are very demanding.

What I did was set up a 15hz tes tone, I keep turning up the AVR till the subs get no louder, back it down 3db and run a REW sweep. This will get you close without toasting your subs. I also run my subs hot so I am not beating the hell out of my mains lol.
post #57 of 152
Quote:
Originally Posted by basshead81 View Post

Run a REW sweep at max output or use Sine wave test tones in rew combined with a handheld spl meter and add the correction values. Take note you should be able to net another 2-3db output with source content.

What exactly does this mean?? I already do sweeps with my PC output maxed and my AVR at 0db....should I go +12 on the AVR (max on mine)?

I have an old-school REW setup - using the headphone out on my PC. No HDMI out for me.....
post #58 of 152
Quote:
Originally Posted by rcohen View Post

F25/F15HP does better than FV15HP at 12hz. At 20hz, the FV15HP has the lead (in terms of quantity). As you go higher, they become very similar.

No they dont. You automatically assume a sealed sub has more output in the infrasonic range(which seems to be a popular trend here) but that is false. The FV15HP will have a 6-8db advantage over its brothern around its tune. With the FV15HP in 2 port mode, they would be close @ 12hz. In 1 port mode or 14hz tune again your looking at a 6-8db difference. go to www.data-bass.com/systems and compare the PB13U 15hz tune compared to its sealed mode. The 15hz tune has a 5db advantage at 12.5hz. The FV15HP vs F15HP would be even more because its tuned lower then the PB13U.
post #59 of 152
I just gotta say Mr. Basshead - you sure have become a wealth of information, and a huge asset to our little community here at AVS. I remember just a short 8 months ago you knew next to nothing about subwoofers - now you seem to know just about everything!

Keep up the good work my friend! biggrin.gif
post #60 of 152
Quote:
Originally Posted by Alan P View Post

What exactly does this mean?? I already do sweeps with my PC output maxed and my AVR at 0db....should I go +12 on the AVR (max on mine)?

I have an old-school REW setup - using the headphone out on my PC. No HDMI out for me.....

Use a spl meter and run your system up till it will not get no louder, back it down 2-3db and run a REW sweep.


This is what my dual XV15 setup put down, no eq'ing with 2db of head room left.



I have not taken any max spl sweeps since adding the third XV15, but I did take a measurement right after setting it up and adjusting the phase/distance. I could probably spend a little more time and get it better withNo EQ. I just got to the point where I was tired of measuring, moving, and tweaking. It sounds great now, so I let it be.



All I have done since adding the Third is take some readings with my spl meter. Currently 90% of the room achieves 126dbavg, I did peg the meter at 130db a couple times, But I will say 128db is probably more realistic. And thats no correction added, just what the meter read. with the correction values added, the subs laid down 118db with a 15hz test tone. Remember my room is exactly half the size of yours...big difference.
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