Can u get fullrange sound at the LP.... - Page 2 - AVS Forum
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post #31 of 55 Old 01-12-2014, 04:23 PM
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You are on the right track: 1130 ft per sec / frequency = wavelength
http://www.sengpielaudio.com/calculator-wavelength.htm
And divide the wavelength/4
So for example 100Hz has a length of 11.3 ft and a 1/4 wavelength of 2.8ft
Verify with this chart
http://www.padrick.net/LiveSound/CancellationMode.htm

Have you plugged your room dimensions ( assuming it's rectangular ) into a mode calculator?

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post #32 of 55 Old 01-12-2014, 04:58 PM
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Well from the front of my baffle wall to the rear of the room is right at 30' and that equals 37hz according to the calculator I used. So that is why my peak at 37hz is about impossible to EQ?

Still messing with the 26ish hz dip. There are a few more dips and peaks that will mess with.

No. I haven't used the mode calculator. My room is aprox 18x35 but has two risers that mess with heights if that matters.
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post #33 of 55 Old 01-12-2014, 05:11 PM
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Quote:
Originally Posted by audiovideoholic View Post

Well from the front of my baffle wall to the rear of the room is right at 30' and that equals 37hz according to the calculator I used. So that is why my peak at 37hz is about impossible to EQ?

Yeah I was thinking it also was room dimensions ( modal related ).
And may help explain the difficulty in removing it.
Axial Modes ( that involve two parallel surfaces - opposite parallel walls, or the floor and ceiling ) are the strongest modes.
In some cases EQ can help only "a little bit" to tame modal peaks at the very lowest frequencies. But most low frequency response errors are highly position dependent, and include nulls as deep as 30 dB. Any EQ correction will help only ONE very specific place in the room, and will by definition make other places worse. Even a foot away the response can be very different. And EQ does nothing for other acoustic problems like first reflections, flutter echo, modal ringing, and so forth.

EQ is global -Speakers can't be instructed to only boost or cut only in selected locations .The directivity is un-altered
Sound is periodic and harmonic - a 1/4 reflection results in a cancellation, and a 1/2 wavelength reflection results in a peak summation of up to 6db.
Conceptualized as a phase wheel that rotates.

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post #34 of 55 Old 01-12-2014, 05:16 PM
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[URL=http://][/URL]
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post #35 of 55 Old 01-13-2014, 07:30 AM
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Quote:
Originally Posted by audiovideoholic View Post

My baffle wall is right at 5' off the treated ib chamber along with a treated baffle wall (3/4" mdf and linacoustic duct liner). Chamber is doubled linacoustic along with "x mil" plastic per Dennis' plans. The subs run from wall to wall along the base of the baffle wall.

Can you figure out if I should have a notch by these factors. Room dimensions from front wall to first row LP is 5' chamber plus 13' (total room is 18'x35'x10') I have a graph from measurements that is rather hard to EQ is why I'm asking this. Will post or link graph if anyone has idea where notch should be if there should even be one. I have one well under 100hz.
Post a detailed diagram.

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post #36 of 55 Old 01-13-2014, 03:37 PM
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http://www.avsforum.com/t/1329702/sony-vw1000-4k-13-scope-and-ten-21-inch-subs/90

About half way down on page are the blueprints.

Baffle chamber 5'. First riser 14' from baffle. Second riser 21' from baffle. Rear wall 30' from baffle. 18x35x10. Soffits are 1' tall and 16" deep. Soffit above baffle sticks out aprox 2' before ceiling height goes back to 10' for first row section then ceiling height goes down with both sets of risers (aprox 1' each).
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post #37 of 55 Old 01-13-2014, 08:46 PM
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I don't see any substantial boundary sourced dips. The one at 26Hz isn't major, for sure it's not audible, and it appears that all of the EQ you need to get it flat is pull-down from 30-80Hz. That peak is a bit odd looking, but I doubt it's room related, it looks to be more of a speaker issue. The other thread was a bit much to wade through in search of details about the subs.

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post #38 of 55 Old 01-13-2014, 10:08 PM
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Here is a close mic. FTW21s in sealed enclosures. Aprox 6.5 cuft per driver. 4 drivers per enclosure.

[URL=http://subclosemic5.jpg]subclosemic5.jpg[/URL]

The 37hz peak and 26hz dip don't really respond well to EQ at all. Extreme EQing does help but can't bring the 37hz peak down. I have to bring everything else up to keep the FR pretty flat.

[URL=http://lowshelve7.jpg]lowshelve7.jpg[/URL]

Sorry for double pics but always does it for some reason.
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post #39 of 55 Old 01-14-2014, 05:10 AM
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Whats your Qtc?

Looks like a high Q system to me but still should respond to EQ cut at the peak. Doesnt matter as long as you dont clip the signal upstream you can boost the nulls or shave the peak. Either way youll eat up amp headroom to bring the low end up.
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post #40 of 55 Old 01-14-2014, 06:19 AM
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Quote:
Originally Posted by audiovideoholic View Post

FTW21s .
Specs? Though without even seeing them it appears your problem is with the box size.

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post #41 of 55 Old 01-14-2014, 07:41 AM - Thread Starter
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Quote:
Originally Posted by audiovideoholic View Post

[URL=http://][/URL]

If thats the best you can get, thats an easy fix. Looks like you have no real nulls to deal with, a parametric EQ could fix that in a minute !
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post #42 of 55 Old 01-14-2014, 07:53 AM
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Quote:
Originally Posted by audiovideoholic View Post

... So that is why my peak at 37hz is about impossible to EQ?....
Since it appears you have tried...
Like Nick said in post 39: Misuse of EQ can blow the signal stream; in addition consider the implications of driver excursion, if gain is overused.

BTW: How much smoothing was applied to those graphs?

Nothing like giving sound advise - on something unheard...

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post #43 of 55 Old 01-14-2014, 01:52 PM
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Quote:
Originally Posted by kgveteran View Post

If thats the best you can get, thats an easy fix. Looks like you have no real nulls to deal with, a parametric EQ could fix that in a minute !

If that's the best I can get? That is a raw response at the LP. I can make it flat but the 37hz peak is very adamant about staying there.
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post #44 of 55 Old 01-14-2014, 01:59 PM
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Quote:
Originally Posted by WVSyd View Post

Since it appears you have tried...
Like Nick said in post 39: Misuse of EQ can blow the signal stream; in addition consider the implications of driver excursion, if gain is overused.

BTW: How much smoothing was applied to those graphs?

Nothing like giving sound advise - on something unheard...

Oh yeah. Once I got that somewhat flat graph I just abandoned the settings because I had to use so much gain to match the 37hz even while cutting 37hz at full tilt.

Smoothing is default 1/6 I believe.
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post #45 of 55 Old 01-14-2014, 02:02 PM
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Specs? Though without even seeing them it appears your problem is with the box size.



76mm IST PS Series low distortion voice coil
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Outside Diameter - 54.3cm
Sealed - 170L (6cu. ft.)
Mounting Diameter - 50.9cm
Bass Reflex - 283L (10cu. ft.) 24Hz
Mounting Depth - 26.4cm
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post #46 of 55 Old 01-14-2014, 02:11 PM
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Quote:
Originally Posted by audiovideoholic View Post

Smoothing is default 1/6 I believe.

1/6 won't have the resolution needed.
Impulse testing would reveal modes.

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post #47 of 55 Old 01-14-2014, 02:17 PM
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Quote:
Originally Posted by WVSyd View Post

1/6 won't have the resolution needed.
Impulse testing would reveal modes.

Ok. What do I need to do?

37hz does equal the distance from the sub/baffle wall to the rear wall exactly. Don't know why haven't caught that until now.
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post #48 of 55 Old 01-14-2014, 02:28 PM
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Can you crank up the rez with your measurement software?
Does it have an impulse testing mode?

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post #49 of 55 Old 01-14-2014, 04:07 PM
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Hes using omnimic idk if he can change the smoothing...
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post #50 of 55 Old 01-14-2014, 04:17 PM
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The problem is the cabs. With a 6.5 cu ft sealed box you can expect a 48hz f3. The ideal config for those drivers is 15 cu ft vented, with 22Hz tuning, giving a 30Hz f0 and 22Hz f3. With the xmax they have you can run them to their full 1200w rating to 17Hz, so unless you want to start again with the cabs EQ and plenty of power is your only option.

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post #51 of 55 Old 01-16-2014, 08:42 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

The answer to the above, BTW, is to have the sub driver rear facing. You seldom see full rangers done that way, and the reason why is simple: most full range adherents would not buy a speaker made that way because they would think it doesn't look right. When you get right down to it, what sells fullrangers/floorstanders is their looks, not their utility.
Does a rear facing sub driver need to have its phase reversed when crossing over at 250 Hz?
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post #52 of 55 Old 01-16-2014, 10:14 AM
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Quote:
Originally Posted by kgveteran View Post

My friend was wondering why companies sell full range speakers. I said because they indeed are fullrange, and usually measure well. Problem is when we place them in our rooms the rules change.......Tricky stuff

Quote:
Originally Posted by Bill Fitzmaurice View Post

Because people want to buy them. Keep in mind that the average person if asked how a speaker works will not have any better answer than "You plug it in", and when asked what a wavelength is they'll probably think it has something to do with surfing. rolleyes.gif


Yes. And because many stereo dudes dont think subwoofers are "audiophile", and because most stereo gear dont have sufficient functionality to properly integrate a subwoofer.
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post #53 of 55 Old 01-16-2014, 10:23 AM
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Does a rear facing sub driver need to have its phase reversed when crossing over at 250 Hz?
If you mean reverse the polarity, no you don't.
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post #54 of 55 Old 01-16-2014, 10:24 AM
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Yes, polarity is what I meant. Thanks.
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post #55 of 55 Old 01-16-2014, 04:12 PM
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Quote:
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Does a rear facing sub driver need to have its phase reversed when crossing over at 250 Hz?
No, but it would be extremely unusual to run a sub that high.

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