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Author Topic: Box plans ASB6128V JBL  (Read 872 times)

todd kroeker

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Box plans ASB6128V JBL
« on: February 17, 2021, 09:54:21 pm »

I read the rules about reverse engineering a box after I posted this so let me re ask in the correct way. I have a pair of JBL 18s from the 6128V cabinet that need a home. I am quite capable of building my own box but feel they deserve what they were designed for since JBL has always been my favorite company since I was in my teens. (60 now... woo hoo !! lol.)

Can I purchase a cabinet from JBL? Does anyone have a web link to their support page that would have it?

While we are on the subject and I do respect designers of the cabinet and how they interact, If a cabinet isn't available or If I buy one from a guy named bill who has an empty one, that money doesn't get to the designer and if they are discontinued.
Is it bad to build one myself?
« Last Edit: February 18, 2021, 12:13:48 am by todd kroeker »
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Paul G. OBrien

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Re: Box plans ASB6128V JBL
« Reply #1 on: February 18, 2021, 09:55:06 am »

Can I purchase a cabinet from JBL?
Not at all likely.

While we are on the subject and I do respect designers of the cabinet and how they interact, If a cabinet isn't available or If I buy one from a guy named bill who has an empty one, that money doesn't get to the designer and if they are discontinued.
Don't lose a micro second of sleep over it, they got their money when the box was sold originally so you don't owe them anything.

As for the box these came in, it was a V loaded reflex which really doesn't do anything useful for subwoofer applications(100hz and lower) so don't bother trying to copy that unless you want that look, the drivers will work the same in a standard reflex enclosure.
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todd kroeker

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Re: Box plans ASB6128V JBL
« Reply #2 on: February 18, 2021, 06:31:04 pm »

Not at all likely.
Don't lose a micro second of sleep over it, they got their money when the box was sold originally so you don't owe them anything.

As for the box these came in, it was a V loaded reflex which really doesn't do anything useful for subwoofer applications(100hz and lower) so don't bother trying to copy that unless you want that look, the drivers will work the same in a standard reflex enclosure.

Thanks
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Art Welter

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Re: Box plans ASB6128V JBL
« Reply #3 on: February 19, 2021, 02:59:33 pm »

As for the box these came in, it was a V loaded reflex which really doesn't do anything useful for subwoofer applications(100hz and lower) so don't bother trying to copy that unless you want that look, the drivers will work the same in a standard reflex enclosure.
Paul,

The "V" loading does several useful things in a subwoofer application:
1) Puts the magnet structure heat sinks in the outside air, reducing power compression.
2) Provides additional air mass loading, increasing sensitivity across the entire pass band.
3) Allows a larger port area than a flat cabinet of the same frontal area with a smoother transition for the port, reducing turbulence, port compression and harmonic distortion.

Going with a bass reflex cabinet of that large volume, those advantages are worth considering.
That said, going that large, I'd be considering a folded or tapped horn.

Art
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Paul G. OBrien

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Re: Box plans ASB6128V JBL
« Reply #4 on: February 19, 2021, 06:41:00 pm »

Thanks Art some good points there, although all that doesn't seem to result in much of a sensitivity advantage going by the published response graph... the box is still only about 98dB@1w below 80hz. Like you say a single driver tapped horn would probably spank it pretty bad.
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Art Welter

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Re: Box plans ASB6128V JBL
« Reply #5 on: February 20, 2021, 05:14:33 pm »

Thanks Art some good points there, although all that doesn't seem to result in much of a sensitivity advantage going by the published response graph... the box is still only about 98dB@1w below 80hz. Like you say a single driver tapped horn would probably spank it pretty bad.
98 dB 1w1m at 30Hz is pretty sensitive.
By comparison, 1w1m 30Hz :
90dB JBLSRX728 (2x18" bass reflex)
91dB EAWSB1001 (2x18""V" load bass reflex)
92dB DSL TH118 (1x18" tapped horn)
99dB DSL DBH-218 (2x18" folded horn of similar size to the JBL ASB6128V)

The DBH-218 FLH is far more sensitive above 30 Hz, more "spank" ;^).

Art
« Last Edit: February 20, 2021, 05:21:34 pm by Art Welter »
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Paul G. OBrien

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Re: Box plans ASB6128V JBL
« Reply #6 on: February 20, 2021, 06:15:15 pm »

98 dB 1w1m at 30Hz is pretty sensitive. 

That is now that you mention it, but can that really be attributed to V loading? I see it as just a low tuned box targeted at install applications.
I found an interesting document about these Differential Drive units that includes some data on the 2258H used in this box..
http://www.cieri.net/Documenti/JBL/Technical%20Notes/JBL%20Technical%20Note%20-%20Vol.1,%20No.34.pdf
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Art Welter

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Re: Box plans ASB6128V JBL
« Reply #7 on: February 21, 2021, 09:57:40 am »

That is now that you mention it, but can that really be attributed to V loading? I see it as just a low tuned box targeted at install applications.
The high sensitivity at 30 Hz mostly comes down to box size, Hoffman's Iron Law: loud, low or small, pick two.

That said, with pro drivers available now with double the Xmax of the 2258H (8mm) the Iron Law can be bent a bit, if you use more power. Doubling Xmax can provide 6 dB more clean output, but uses six dB more power too..

Art
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todd kroeker

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Re: Box plans ASB6128V JBL
« Reply #8 on: February 26, 2021, 11:18:35 pm »

Great info guys. I would like to see what folded cabinets these  (2258 3"vc ) will work good in. I am trying to stay small without under doing it at the same time. I have a bigger system that has 4 18" hog scoops and this system is supposed to size in about half  of it.
This system is
2-18's Total and,
-each side is:
1 - 15 front horn loaded   
2 - 12's front horn loaded
1 - 2445 with flat front 2380
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Riley Casey

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Re: Box plans ASB6128V JBL
« Reply #9 on: February 27, 2021, 04:43:43 pm »

Blast from th past PA. Your system sounds like what I was using back in the late 70s and early 80s.If you want maximum level without maximum under 40hz output there is always the the Don Keele W 18 horns. Another popular solution was to make oversized versions of the JBL 4520 folded horns as single or dual 18s rather than the original dual 15s.

http://www.audioheritage.org/vbulletin/showthread.php?35664-Early-80-s-Don-Keele-amp-Mark-Gander-JBL-horn-plans

Great info guys. I would like to see what folded cabinets these  (2258 3"vc ) will work good in. I am trying to stay small without under doing it at the same time. I have a bigger system that has 4 18" hog scoops and this system is supposed to size in about half  of it.
This system is
2-18's Total and,
-each side is:
1 - 15 front horn loaded   
2 - 12's front horn loaded
1 - 2445 with flat front 2380

Steve-White

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Re: Box plans ASB6128V JBL
« Reply #10 on: February 27, 2021, 06:35:54 pm »

^^^ After going through the JBL 4560 phase, which came after the rear horn loaded era - I ran the Don Keele "W" horns with JBL E-155's in them and the compliment Don Keele front horn loaded mid bass cabinets with E-120's and 2202's in them.

They worked and squeezed lots of performance from the drivers of that era - a pair of them on each side with a pair of 2" 90x40 radials and 4 2205's would do brain damage in a 1000 seat room.  Today, JBL 2269H's in single 18" reflex cabinets and 8 per side - way easier to wrangle and scaleable.

The "B" system back then was a pair of dual-12" cabinets vertical orientation with 2 x 2202 ring's and a 2390 horn/lens atop Atlas tripods and two of the DK "W" horns stacked on one side.  A pole mount setup for smaller jobs like dance music and fashion shows works great.  I have pole mount stuff today as well and receiver flanges in all the monitors as well as dedicated 12" pole mount cabinets.

For smaller jobs, pole mount is my preference - even with delay fills.
« Last Edit: February 27, 2021, 11:50:02 pm by Steve-White »
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Mike Caldwell

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Re: Box plans ASB6128V JBL
« Reply #11 on: February 27, 2021, 07:11:57 pm »

Blast from th past PA. Your system sounds like what I was using back in the late 70s and early 80s.If you want maximum level without maximum under 40hz output there is always the the Don Keele W 18 horns. Another popular solution was to make oversized versions of the JBL 4520 folded horns as single or dual 18s rather than the original dual 15s.

http://www.audioheritage.org/vbulletin/showthread.php?35664-Early-80-s-Don-Keele-amp-Mark-Gander-JBL-horn-plans

That Audioheritage post looked familiar!!!

I still have those plans in the original JBL envelope they were sent to me in from JBL.

Mike Caldwell

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Re: Box plans ASB6128V JBL
« Reply #12 on: February 27, 2021, 07:15:40 pm »


  I have pole mount stuff today as well and receiver flanges in all the monitors as well as dedicated 12" pole mount cabinets.

For smaller jobs, pole mount is my preference - even with delay fills.

Same here, I have some double 6 x 1 cabinets that work horizontal for front fill or vertical on a stick.

ProSoundWeb Community

Re: Box plans ASB6128V JBL
« Reply #12 on: February 27, 2021, 07:15:40 pm »


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