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Sealed... 20-50Hz, LOUD?
Sealed... 20-50Hz, LOUD?
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Old 9th February 2018, 12:31 AM   #1
mark100 is offline mark100  United States
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Default Sealed... 20-50Hz, LOUD?

What would you do if you wanted a sealed sub, 20-50Hz, to keep up with sealed subs picking up at 50Hz?

Pro-sound levels, need to reach mid 130 dB minimum, using enough boxes to make it happen.
Pls pay no mind to amps, or processing requirements, ....also no IPAL recommendations pls.

What driver, what box? Thx!
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Old 9th February 2018, 01:53 AM   #2
conanski is offline conanski  Canada
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OK my first thought is.. the only way this is gonna happen with a sealed box is if you put a giant horn in front of it. But is this for pro sound applications or just pro sound SPLs in a home environment? Because 130+db at 10ft indoors is a LOT different than 130+dB at 100ft outdoors.
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Old 9th February 2018, 04:32 AM   #3
globalplayer is offline globalplayer  Germany
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I would use a couple of Alpine SWR-1522Ds in around 50 ltr. closed each and some eq. Due to the closed box power handling can be down a little.
If outdoor this will be quite a wall of boxes.
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Last edited by globalplayer; 9th February 2018 at 04:38 AM.
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Old 9th February 2018, 11:43 AM   #4
MemX is offline MemX  United Kingdom
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How big can the boxes be?
How many boxes?
Will they need to move once in place?
What's the budget?
Why not aim for <20Hz output?
What will they be used for?

The SI 24" would get you most of the way there with one from around 40hz and up...
Data-Bass but you're looking at multiples of anything if you want to stay sealed.
Data-Bass
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Old 9th February 2018, 04:56 PM   #5
mark100 is offline mark100  United States
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Hi MemX, Let me first answer conanski.....I meant 130dB @ 1 meter...

Ok, I guess a little background / more info is needed..

I've built both sealed and ported single driver subs using the bms18n862, that were inspired by the data-bass projects.
I'm very pleased with both boxes.
The sealed is about 21x21x22.
The ported is about 23x23x30, f3 31Hz.
I have two of each right now.

If I can get to 20Hz (or lower of course) with another sealed design, I will convert all 4 bms to sealed, to mate with the new 20Hz boxes.

If I see I can't do this reasonably, I'll convert all my bms to ported , and most likely build some more ported, same box.

I want to get to 8 boxes of ported equivalentcy.
They get used everywhere from inside the house, to outside live gigs.

I also have 4 Labhorns and a couple of orbitshifters, so I have alot of options for gigging.
I'm just really liking the portability, scalability, and sound of the single bms 18's.

I'll need drivers to stay in the $500 zipcode or less range, and weight under 100lbs.
I was able to keep the bms ported box to 91lbs using 15mm BB and lots of bracing.
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Old 11th February 2018, 11:47 AM   #6
TBTL is offline TBTL  Germany
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It's best to first set your goals and then pick acceptable compromises.

Your goals are (among others) loud and 20 Hz. A sealed enclosure is a compromise that sacrifices both. Of course this would be OK if you really need one of the advantages a sealed enclosure provides, like the ability to equalize the system flat down to an arbitrary frequency for home theater use. What are the advantages of a sealed enclosure that you require?
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Old 11th February 2018, 01:20 PM   #7
globalplayer is offline globalplayer  Germany
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20hz, outdoor, closed, loud?

Closed boxes will have really low efficiency compared to other designs except open baffle which makes even less sense outdoor.
Outdoor you will need maybe 4-8 times the cone area/power for the same spl as indoor in the bass range.
If you want to go below 40-45 hz even more so.

For 20 hz outdoor/closed you will need truck loads of boxes and amps.
Regarding ear sensivity +30db is required at 20 hz for it to be perceived equal in loudness as a 1khz tone/frequency. That's 1000 times the power.

A reasonable way will be horns or 6th order band pass boxes due to efficiency.
Horns will get very large though due to required horn length and mouth area although coupling will extend low freq response.

And even with efficient boxes this will still end up in a "big wall" of expensive equipment if sq is one of your goals.
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Old 11th February 2018, 03:10 PM   #8
chris661 is offline chris661  United Kingdom
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For what it's worth, I'd avoid using sealed boxes for PA subs. Using the cone area of 6x 15" drivers (each with a healthy 10mm Xmax), there was just about enough output at 60Hz for a couple of hundred people outdoors. I originally set the highpass for 35Hz, but they just weren't hacking it - the amps clipped immediately. Even going for 60Hz they were only just getting by.

Here's a neat little app to play with - Piston Excursion calculator
It converts nicely between SPL, Xmax, frequency, cone area, etc.

It tells me that you'll need 20x 18" drivers each moving just over 13mm one-way to produce 130dB at 20Hz. Of course, you'll also need to power them.

A ported box tuned in the low-20s will outperform the sealed boxes, and might just about do what you want - you'll run out of headroom in the low-30s where the port isn't doing much work, so the driver has to do the work itself. A set of 4x 18" drivers ported tuned around 22Hz will pass 130dB 20Hz and up if they've got the Xmax (the BMS drivers you have will do it fine).

If you're content with flat-to-40Hz performance, you can get ~129dB from a pair of good 15"s in smallish boxes - 440x440x650mm.
Teeny tiny PA 15&quot; subwoofer

Chris
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Old 11th February 2018, 11:45 PM   #9
mark100 is offline mark100  United States
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Thanks for comments everyone..

Yeah, I totally get the "impracticality" of sealed for PA down to 20Hz, and what that would mean in terms of box and amp count.

I really just like trying stuff

I'm thinking the safest way to try this is get 4 more bms 18n862, to go with the 4 I have, and make 8 sealed boxes.
Put Linkwitz Transforms on them , and see how it works.

They are 1500 W AES 8 ohms. I've got 15K into 4 without bridging, 20K with bridging, so I think all good on amps.
All I'm really out, besides 4 drivers which I can use no matter, is the time and $ to build 6 more sealed cabs....which w/o paint and handles etc is prob 2 days and about $300.

So 4 more drivers for about $2K is the big nut...
I figure odds are I'll end up with the 8 BR cabs I know that works...
but after at least hearing what a pile of sealed can do, and having a nice bonfire of sealed boxes
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Old 12th February 2018, 12:26 AM   #10
Sonce is offline Sonce  Macedonia
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Quote:
Originally Posted by mark100 View Post
a sealed sub, 20-50Hz,
Quote:
Originally Posted by mark100 View Post
I want to get to 8 boxes of ported equivalentcy.
They get used everywhere from inside the house, to outside live gigs.
Quote:
Originally Posted by mark100 View Post
I really just like trying stuff

I'm thinking the safest way to try this is get 4 more bms 18n862, to go with the 4 I have, and make 8 sealed boxes.
Put Linkwitz Transforms on them , and see how it works.
Live music with content below 35 Hz? Nothing there to try and nothing there to see and hear.
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