JBL 4507A and 4509 enclosures

[ctrrap]

New to forum hope Im doing this right and in the right spot
These were said to have been kit built by a University of Iowa physics professor in 1956 they were a course project. The d130 is unmistakable through the cloth but also has a tweeter and mid horn. I have not had them open but the grandson has pictures of the build and he too swears he has never opened them. It has a jbl crossover 2way on the rear but also has hand spun internal crossover with an external 8-position switch to activate the various options. He said he course goal was to reproduce orig. sound of a symphony to stage music hence the various crossover options. The cases weigh about 95lbs and appear to be burled walnut with a degreed oak face panel. I have a link to a small clip but my camera is very cheap so keep that in mind. Sound levels on a single ended 6bq5 amp are incredible.

here is a clip of them working:
http://www.trrap.com/downloads/jbl.MOV

[Zilch]

After all things considered, I'll make some 4507A cabinets which I think will be the same as making 4507's but with the speaker and ports centred....

I don't know the ultimate intent, which, in my experience, has a tendency to change.

If I were building 2507s, I'd be retaining the option of integrating horns into the cabinets, and I might be seriously considering moving the woofer a bit further toward one end so as to provide enough space for 2344(A)s to make DIY 4430s.

2381s are going into mine, so the stock spacing is adequate.

[Kwikas]

Originally posted by Zilch

I don't know the ultimate intent, which, in my experience, has a tendency to change.

Thanks Zilch. I definitely want three 4507A LF cabinets. These are required to complete my 3631 ScreenArray's. I have the MF/HF sections already but need the bass cabinets. The only drivers going into these will be 2226's.

Cheers

[John]

OK Here's what I got for you so far. These are exact measurments from the 4507 cabinets.

Top and bottom and sides as well as the rear panel are 3/4" thick particule board.

Front Baffle is 1"

Both front baffle and rear panel are set back 1/2"

Outside measurments are 17-5/8 Deep x 21-1/2" Wide x 30-1/2" High

The ports are 3" I. D. and are 6-1/4" deep from front of baffle to rear of port tube.

The bracing and port locations as well as the opening location for the 15" woofer will have to wait till I have more time later this month. At least for now you have enought info to source your material.

[Kwikas]

Originally posted by John

OK Here's what I got for you so far. These are exact measurments from the 4507 cabinets.

Many thanks John and you're right......I can start sourcing the materials from your information. I'll await your further advice re bracing etc.

I'm going to locate the 2226 driver in the centre of the baffle. So, in effect I'm making the 4507A - not the 4507. I doubt there is much engineering difference other than the driver placement as Zilch pointed out earlier.

[John]

I'm going to locate the 2226 driver in the centre of the baffle. So, in effect I'm making the 4507A - not the 4507. I doubt there is much engineering difference other than the driver placement as Zilch pointed out earlier.

I do not know the answer to that but there are two major braces in that cabinet. One that goes side to side right behind the woofer and one that runs front to back just below the woofer. If you center the woofer in the cabinet you might want to run two front to back braces as one would be too close to one end of cabinet to work properly in deadening the cabinet???

Also just to be clear there are 4 ports in the 4507 cabinet spaced equally around the woofer opening.

[Kwikas]

Originally posted by John

I do not know the answer to that but there are two major braces in that cabinet. One that goes side to side right behind the woofer and one that runs front to back just below the woofer. If you center the woofer in the cabinet you might want to run two front to back braces as one would be too close to one end of cabinet to work properly in deadening the cabinet???

Also just to be clear there are 4 ports in the 4507 cabinet spaced equally around the woofer opening.

That's great info. re the bracing and yes I understand the 4 ports centred around the driver......

Just for my understanding, if you add bracing then the internal volume reduces...yes? So, how do you maintain the correct internal volume according to what the manufacturer specifies? This is the part I don't understand.....obviously!!!

[Kwikas]

Guys,

Time for me to resurrect this thread now that I'm ready to start building my 4507A cabinets.

Originally posted by John
OK Here's what I got for you so far. These are exact measurments from the 4507 cabinets.

Top and bottom and sides as well as the rear panel are 3/4" thick particule board.

Front Baffle is 1"

Both front baffle and rear panel are set back 1/2"

Outside measurments are 17-5/8 Deep x 21-1/2" Wide x 30-1/2" High

The ports are 3" I. D. and are 6-1/4" deep from front of baffle to rear of port tube.

The bracing and port locations as well as the opening location for the 15" woofer will have to wait till I have more time later this month. At least for now you have enought info to source your material.

The most accessible tube for me to buy down here is 66mm ID. I guess I can use this diameter for the 4 ports rather than the 73mm ID but I'll have to make these a different length than the 6-1/4" specified for the 73mm.

Can someone please confirm this?

Thanks

[macaroonie]

Good luck with your construction. Just about all Scotch malt whisky is exported in tubes. If you go to a good quality bar in town they will throw these out on a daily basis. Sizes are typically 75 -95 mm dia and are ideal for your needs. Better still go to your nearest bottle shop and buy a bottle of Balvenie 12 year old (95 mm ) and you can toast your efforts as you go along.

Locking mitre joints are great but you need to be super accurate with the router cuts or the joints will not sit dead straight. The cutter set is pretty pricey too. Do it my way, good and strong and easily done in home conditions, plus if you are post veneering you can make errors and correct as you go and you will never see the fix.

Tuning. You need to add up all the stuff that is inside the basic volume of the cabinet including the volume displaced by the back ofthe driver.
If you are really fussy you can get sliding ports that are adjustable in length then you can tune away to your hearts content. Have you done a simulation in Win ISD.

[Russellc]

Yup, and plenty of room to cut in a horn of choice....

"Econowaaa.....Oh, nevermind!

Russellc

[Russellc]

Guys,

Time for me to resurrect this thread now that I'm ready to start building my 4507A cabinets.



The most accessible tube for me to buy down here is 66mm ID. I guess I can use this diameter for the 4 ports rather than the 73mm ID but I'll have to make these a different length than the 6-1/4" specified for the 73mm.

Can someone please confirm this?

Thanks

I do have a pair of 4647 cabinets which I believe are identical to 4507?
If you need any measurements or construction detail pics, I'll be happy to oblige.

Russellc

[Kwikas]

Originally posted by Russellc
I do have a pair of 4647 cabinets which I believe are identical to 4507?
If you need any measurements or construction detail pics, I'll be happy to oblige.

Construction detail pics would be very much appreciated - thanks Russell

[Russellc]

I'll post a couple and tell me if any particular detail is wanted. It doesnt appear that either the front or the back is removable, but I can remove the driver and show the inside construction from there.

I measure exactly as others have already posted. The front and rear panels are inset 1/2 inch. Top, sides and bottom panels appear to have been cut at 45 degrees.

Russellc

[Kwikas]

Thanks again for the help.

I'd very much appreciate being able to see the inside of the box but geez Russell, seriously, don't go removing the driver unless you are okay with this and it's not a PITA. Okay? I'll competely understand if you can't be bothered.....

Yes, in-so-far as I can understand construction of the 4507 cabinet, the top, bottom and sides are routed with a slot that takes in the front baffle and rear panel. There is no way of disassembling the cabinet because as jbl pointed out in an earlier post, the whole design is kind of a locking fit.

I see the edge joints have all been mitred at 45 degrees........I'll probably go with butt joints. They are easier to do, easier to get airtight and the cabinets will sit behind the screen anyway. Noone is going to see them.

Other than that, I think I'm reasonably good to go.

I'm cheating a little on the cutting in that I'm not doing it myself. A friend of mine has a kitchen joinery business and he has fully computerised wood panel cutting equipment. I'll get him to cut the speaker panels to size........

Macaroonie. I've gone into your thread and will use a lot of the advice and suggestions contained in it. Pictures are worth 10,000 words...

Cheers

[Russellc]

In the next couple of weeks I will be installing a different driver, so I'll take them when I do that. Appears to be fairly straight forward, bracing as others have stated.

russellc