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High Bl, BR enclosures, and port damping?
High Bl, BR enclosures, and port damping?
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Old 16th July 2018, 05:04 PM   #11
Windforce85 is offline Windforce85  Poland
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I have no experience with TH designs but with high-BI (actually high BI^2/Re product) drivers and when money is no object I'd prefer multiple drivers in small sealed boxes. I hope we are talking about domestic conditions? I don't know whether you consider active system with some DSP magic or not but resulting benefits for domestic listener from such combination are obvious.

- Direct radiator design - maximally controlled response. Sound excitated purely with driver itself without relying on non-linear behaviour of resonant air column.

- High motor strength will result with critically damped boxes. Total control over radiation time domain.

- Highest possible ratio of radiation area to volume occupied - saves cost of materials and workmanship.

- Sealed box is ultra-easy for equalization, especially with DSP.

- Multiple radiators around typical listening room can eliminate most of room modal resonances.

- Any sealed driver design has inherently high WAF.


Amplifier power is so cheap nowadays that I would't take efficiency upon consideration anymore.

Last edited by Windforce85; 16th July 2018 at 05:10 PM.
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Old 17th July 2018, 04:21 AM   #12
Cableaddict is offline Cableaddict
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Quote:
Originally Posted by Windforce85 View Post
I have no experience with TH designs but with high-BI (actually high BI^2/Re product) drivers and when money is no object I'd prefer multiple drivers in small sealed boxes.
I hope we are talking about domestic conditions? I don't know whether you consider active system with some DSP magic or not but resulting benefits for domestic listener from such combination are obvious......
.
Nah, I'm primarily talking about live band / DJ subs.

- Bit all data is useful, so thanks. Also, I agree that two smaller drivers per sub offers several benefits, but of course this also adds complexity & has trade-offs. I think the best overall idea s to se a driver that is rated for way more watts than you need, and not drive it hard. The trade-off there is that most such drivers are less sensitive than their lower-wattage cousins.

Quote:
Originally Posted by Windforce85 View Post
Amplifier power is so cheap nowadays that I would't take efficiency upon consideration anymore.
Yes, but available current is typically a huge problem for a small band or mobile DJ. It doesn't matter what mondo amps you carry, if all you have is a single 15a circuit. (and you also have to run computers, lights, etc. Believe me, I've made a hobby of melting Lab Grupen Fp6400's, and circuit breakers run for cover when they see me pull up t the gig.

Last edited by Cableaddict; 17th July 2018 at 04:27 AM.
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Old 17th July 2018, 04:38 AM   #13
Cableaddict is offline Cableaddict
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Quote:
Originally Posted by chris661 View Post

.... sometimes high-BL drivers (which often have very low Qes and therefore Qts) are at their flattest when used in an extremely small ported cabinet tuned quite high up.
The simulators will usually recommend a "textbook" alignment, ie, aiming for a Butterworth rolloff, and will play with the cabinet's properties to get there, regardless of where the low-end rolloff actually ends up.
You'll find that using a cabinet that's larger than recommended by the textbook alignments gives a frequency response that isn't perfectly flat, but it'll usually only be a touch of EQ away, and will go much deeper into the bass.
Chris, are you saying to err on the side of a larger enclosure, despite what the software recommends, in order to lessen the impedance against the driver? (Sorry, I may be using the wrong terminology.)

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Originally Posted by chris661 View Post

For the reference of the other posters, is this still for your PA system?
Yes. I would like to try both some kind of BR design, and then also a TH, using the same drivers so I get as "fair" a comparison as possible. But of course, if no driver is actually optimum in both designs, then this idea goes out the window. I'm working on the assumption that a high compression ratio horn works best with a high Bl driver. - Something I've read multiple times.
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Old 17th July 2018, 04:43 AM   #14
Cableaddict is offline Cableaddict
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KSTR,

thanks for that great explanation.

Sadly, it doesn't make my quest all that promising.
- but what about my original question, based on that article I quoted?
That is, can this eq anomaly (which I assume is amplitude-dependant) be lessens by somehow modifying the ports?
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Old 17th July 2018, 07:55 AM   #15
chris661 is offline chris661  United Kingdom
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Quote:
Originally Posted by Cableaddict View Post
Chris, are you saying to err on the side of a larger enclosure, despite what the software recommends, in order to lessen the impedance against the driver? (Sorry, I may be using the wrong terminology.)
What I'm saying is that a high-BL driver will typically give a textbook Butterworth response shape at a frequency that's higher than we'd want for a PA subwoofer. It's a small box, tuned quite high.
So, we go off-piste just a little by making the box bigger and tuning lower. It'll give a response that slopes down a little, but at least then the LF extension is there.

For what it's worth, the Faital Pro 15HP1060 drivers I use in my (approximately) ported cabinets have also been used in THs around here, with good results on all accounts.

I think you'll be able to put them in either just fine.

Of course, the best way to learn is to play with simulators, and then build them. I think you'll be able to answer a lot of your own questions if you set off with WinISD Pro and then graduate to Hornresp.

Chris
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Old 17th July 2018, 08:58 AM   #16
wonderfulaudio is offline wonderfulaudio  India
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Quote:
Originally Posted by KSTR View Post
you can't fix it with EQ
http://www.xlrtechs.com/dbkeele.com/...0High%20BL.pdf

Quoting from the above paper
"When the true efficiency of the driver is considered,
it is clear that increasing the Bl factor will directly
result in higher efficiency values at all frequencies.
Unfortunately, the constant-voltage-drive low frequency
response may suffer, but this only means
equalization must be used to flatten the frequency
response."
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Old 17th July 2018, 08:00 PM   #17
bentoronto is offline bentoronto  Canada
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High Bl, BR enclosures, and port damping?
Quote:
Originally Posted by wonderfulaudio;5491409
[url
http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(2003-10%20AES%20Preprint)%20-%20Nom%20vs%20True%20Eff%20High%20BL.pdf[/url]

Quoting from the above paper
"When the true efficiency of the driver is considered,
it is clear that increasing the Bl factor will directly
result in higher efficiency values at all frequencies.
Unfortunately, the constant-voltage-drive low frequency
response may suffer, but this only means
equalization must be used to flatten the frequency
response."
Some bad confusions there.

KSTR was not wrong in saying you can't use EQ... to fix resonances. But you can fix freq response if by FR you mean plots like the basic REW sweep*.


I found the Keele article disturbing. Yes, you can make an FR-sweep go lower by using a worser driver. Or a driver with a lb cone assembly. Maybe that kind of "logic" appeals to commercial sound contractors.

Anybody like those kinds of thoughts?

B.
* but not perceived tonal balance which I think would be influenced by resonances differently than an REW plot.
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Last edited by bentoronto; 17th July 2018 at 08:05 PM.
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Old 17th July 2018, 08:44 PM   #18
whgeiger is offline whgeiger  United States
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Default No choice

Given venues close to this

Quote:
Yes, but available current is typically a huge problem for a small band or mobile DJ. It doesn't matter what mondo amps you carry, if all you have is a single 15a circuit. (and you also have to run computers, lights, etc. Believe me, I've made a hobby of melting Lab Grupen Fp6400's, and circuit breakers run for cover when they see me pull up t the gig.
a tapped horn implementation is what you need. The driver chosen must have parameters that meet horn requirements. BL product is only part of it.

Alternatively, invest in a generator set, for these wimpy venues, and charge extra for its use. Otherwise observe, that there are some (non-) business opportunities that you should simply walk away from.

WHG
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Old 17th July 2018, 10:16 PM   #19
mark100 is offline mark100  United States
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Quote:
Originally Posted by Cableaddict View Post


Believe me, I've made a hobby of melting Lab Grupen Fp6400's, and circuit breakers run for cover when they see me pull up t the gig.
Hi, What do mean 'melt a Fp6400' ? Just that you tripped a breaker?
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Old 18th July 2018, 07:28 AM   #20
chris661 is offline chris661  United Kingdom
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Quote:
Originally Posted by mark100 View Post
Hi, What do mean 'melt a Fp6400' ? Just that you tripped a breaker?
From what I can tell, he's literally destroying those amps. Until recently, he had 4x Bag End 18" sealed subwoofers with their processor. Sealed subs aren't efficient at the best of times. Add in the compression in the processor and I'd expect the amp (and speakers) to be working very hard.

I wouldn't expect a Lab Gruppen amp to blow (ever), but that's where we are.

Chris
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