Cab size for 2245?

[robertbartsch]

Ok, so what sized cabs in square feet are recommended for these drivers.

Thx...

[Robh3606]

Do a search there must be 10 threads that go over it plus plans in the Library. Try B460

Rob:)

[Doc Mark]

Ok, so what sized cabs in square feet are recommended for these drivers.

Thx...

Yeah, what Rob said. Also, most enclosures are calculated in cubic feet, and not square feet...... or, I've been doing it wrong for the past 30 years.... which is, of course, possible! :bouncy::D;)

Doc

[robertbartsch]

http://www.jblpro.com/catalog/General/Product.aspx?PId=206&MId=1

The box size for a 2242 is 40" x 26" x 18"

[robertbartsch]

So in the post below it says the 2245 box in a commercial JBL application is 9 cubic feet.


...not sure about the ports, however.

************
Hi Gene,

Thanks for your post..we wondered where you had got to.

Is the main enclosure lined with fibreglass?

In my initial I tuned with the 2245 I usedthem in a similar manner to yours but I used an active crossover (DB Keele tuning 292 litres 27 hz Fb).

Using the passive crossover later on made the bass less tight and a bit boomy.

The reason is that the effect of DC resistance in the crossover for the woofer and the large box gives a somewhat underdamped response and will lead to a small bump in the response.This is because the wooker T/L electrical and mechanical paramters are effected and this leads to audible ripple an or a slight lift in the response.

Is this what you are hearing?

In the commercial JBL systems, they tuned the 2245 at 30 hz and use a smaller box. In the JBL monitor 4345 the net volume is 9 cu ft and its tuned to 28-29 hertz.

I find the biamping on this woofer far more satisfactory than a passive crossover.

regards

Ian

[hjames]

Here's the original design ... from Audio - Aug 1983
http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm

Here are B-460 details -
http://audioheritage.org/vbulletin/showthread.php?t=5382

But there is a LOT of other stuff here free for the site searching ...




Do a search there must be 10 threads that go over it plus plans in the Library. Try B460

Rob:)

[4313B]

And here's the technical information on the fool proof design for all the... well you know... them... - B460 (http://audioheritage.org/vbulletin/showthread.php?t=4557) -

8.0 cubic feet tuned to ~ 26 Hz and used with the BX63 or BX63A (or any other electronic low pass filter that can provide a 12 dB/octave 26 Hz high pass filter with a Q of ~ 2 aka "bump" filter).

[Ian Mackenzie]

Yep,

Just make sure you have the Hoover Dam on tap to power it.

[maxwedge]

Ok, so what sized cabs in square feet are recommended for these drivers.

Thx...
BIG!:applaud:
edit: I wold say 10' sq' plus

[Val]

BIG!:applaud:
edit: I wold say 10' sq' plus

ditto

[ratitifb]

Ok, so what sized cabs in square feet are recommended for these drivers.

Thx...:D

From Beranek, "In practice, the equivalent of an infinite baffle is a very large enclosure, well damped by absorbing material..." ;)

When the volume enclosure is small (i.e 10 cubic feet :blink:) you can improve the low end in frequency response by tuning the enclosure with a port : the bass-reflex enclosure :p

[robertbartsch]

I suppose all things are relative. I would characterize a 10 square foot box as freck'n HUGE not small, however.

Anyway, these two 2245s are for my basement system so I won't have to fight the wife on bringing another huge box into the house once again.

I have a 10 square foot box with a 2242 in the TV room now which was pounding out some big bass in our HT last night. This monkey is very convincing in a home setting.

[speakerdave]

Is this conversation actually about square feet, or is it cubic feet?

[maxwedge]

Is this conversation actually about square feet, or is it cubic feet?
I said sq ft in my post too but I meant to say cu ft, lol.:banghead:

[4313B]

dittoThe 10 cubic foot @ 30 Hz box is a good box too. :yes:

I believe JBL settled on the 8 cubic foot @ 25 Hz box with BX63/BX63A for home subwoofer use for the smaller size as well as the extension.

[rlsound]

IMAX used this driver in a 16 cu foot sealed enclosure. I'm not sure on the specs but 8 of these going off is enough to make you run for cover.

[4313B]

IMAX used this driver in a 16 cu foot sealed enclosure. I'm not sure on the specs but 8 of these going off is enough to make you run for cover.Yeah but they all blew up and got replaced by 2242H's. :p
That's probably where all those ten sale rebuilds came from. :rotfl:

[rlsound]

Good point actually!

I heard of one IMAX theater replacing the 2245s with RCF drivers. Between the foam rot and the lower power handling, they must have changed them out frequently.

[JBL 4645]

http://www.jblpro.com/catalog/General/Product.aspx?PId=206&MId=1

The box size for a 2242 is 40" x 26" x 18"

That’s sounds about right my diy JBL 4645 is around 18” 42” 26” inside dimensions are a fraction less its 25mm MDF.

[JBL 4645]

Good point actually!

I heard of one IMAX theater replacing the 2245s with RCF drivers. Between the foam rot and the lower power handling, they must have changed them out frequently.

No doubt that is true! Same story with the Empire Leicester Square, London, original JBL 13KW THX sound system! I was told that the Cimarron busted a few JBL 4645 in! It did rumble the cinema deep I mean DEEP when the subwoofer track came on! When I saw (Indiana Jones and the Last Crusade) Wednesday 13th September 1989. Thou I don’t recall hearing any popping or distortion sounds, must have been around a different time when this happened.

http://thedvdexperience.free.fr/dossiers/testtrailers/scrshot/thx_cimarron_3.jpg

[JBL 4645]

Yeah but they all blew up and got replaced by 2242H's. :p
That's probably where all those ten sale rebuilds came from. :rotfl:

Same type that the Empire now uses for its custom JBL 56KW THX sound system. :applaud: Transformers The Spy Who Loved Me and The X-Files I want To Believe, yeah you better believe it when you listen to one of the finest THX cinemas in the whole Europe.

[Allanvh5150]

I have always found it perculiar that everyone kills 2245's. I used them for sound reinforcement for years and didn't have any issues with them. :blink: