Construction of DIY L300 enclosures.

[tjm001]

In a previous post I stated I was going to construct a DIY version of the L300 boxes. In searching numerous posts on this site as to the shape, size and exact dimensions I have a few questions. Hopefully someone that either has done this or owns a L300 can answer.

1. Am I correct in assuming that the sides of the enclosure are made of pre-veneered walnut MDF panels and that the rounded edges where the sides join the top are made of solid walnut stock? In other words the flat parts are walnut veneered and the rounded parts are solid walnut.


2. If this is the case how are the top and side panels joined internally? In other words what does the internal bracing inside the cabinet look like where the top (and bottom) meets the side panels?

[Doc Mark]

Evening,

Our L300's are made of 3/4" high density particle board for the top, bottom, sides, and back, and the baffle front is made of 1" Baltic birch, or something very much like it. I believe the sides are locked to the top with a special locking joint, information for which can be found in the JBL Contruction Guide, in the JBL Library here at LH. The sides are veneered with walnut, and the top edges on both sides have 1/4 -round length of walnut hardwood attached to it, with a smoked glass top to fill it in.

Check out this link, and look at the cut-away views of the L300, compared to the 4333.

http://www.lansingheritage.org/html/jbl/specs/home-speakers/1975-l300.htm

This should tell you much about what you are wanting to know. But, if you have further questions, please give a shout, and I'll do what I can to help. Take care, and God Bless!

Doc

[Mr. Widget]

...and the baffle front is made of 1" Baltic birch, or something very much like it.Are you sure? The cut away that you referenced clearly shows 3/4" MDF.

Do your 077s fit flush on the baffle or do they protrude slightly out from the front surface. To my knowledge all of the JBL 43XX Series with these slot tweeters have them slightly proud of the surface as do the L65s and I thought L300s. The only exception is the 4350/4355 where they do use 1" Baltic birch and the tweeters are essentially flush with the blue baffle.


Widget

[Doc Mark]

Morning, Widget,

In truth, I did not pull the 2235H's from our L300's to check, and instead, checked on a pair of 4333 cabinets that Grumpy gave me quite a few years ago. I've installed 2235H's in them, as well, and since the info from JBL stated that the enclosure for the L300 was made of material up to 1" thick, and that the cabinet is structurally identical to the 4333 in every respect, I assumed the 1" to be the baffle, where it would do the most good. I also took a photo of the baffle of the 4333, which shows clearly that it is made of laminated Baltic birch, or something similar, and not MDF.

64471

You know what they say about people who "assume", though, and maybe our L300's are made differently. I checked the 077s, and the 2405's that are installed in the L300's and 4333's, respectively, and both protrude just a tad from the front baffles of their respective cabinets. So, that probably means that the material, no matter what it's made of, is only 3/4" thick. But, where would JBL use 1" material, if not the baffle, where it would seem to do the most good? Just for giggles, I can lay one of our L300's on it's back today, and remove the 2235H, just to check the material of the baffle, if that would help. I'm always up for learning something, new, or old! Take care, and God Bless!

Every Good Wish,
Doc

[tjm001]

Hi guys thanks for the info so far. I'm still not sure how the internal (under the veneer and quarter round) sides meets the top. I'm traveling now and will post more detailed question when I return. Thanks.
Tom

[Doc Mark]

Hi, Tom,

Here's another bit of information from one of our fine members, that you may find very helpful.

http://www.audioheritage.org/vbulletin/showthread.php?20230-Need-L300-dimensions&highlight=L300+dimensions

Some excellent measurements, and also detailed shots of the corner construction about which you asked. Take care, and God Bless!

Every Good Wish,
Doc

[Mr. Widget]

Doc, Tom has already found and posted that link in his quest... many of the dimensions on that drawing are not called out. They are simply labeled as various unknowns.


Widget

[martin2395]

Are you sure? The cut away that you referenced clearly shows 3/4" MDF.
Do your 077s fit flush on the baffle or do they protrude slightly out from the front surface. To my knowledge all of the JBL 43XX Series with these slot tweeters have them slightly proud of the surface as do the L65s and I thought L300s. The only exception is the 4350/4355 where they do use 1" Baltic birch and the tweeters are essentially flush with the blue baffle.
Widget


On the 4343 they are flush, 100% sure.

[Mr. Widget]

On the 4343 they are flush, 100% sure.Because the 4343 has that rotating upper baffle, they may have used a 1 inch baffle on it as well… I'm not sure.


Widget

[richluvsound]

Widget is correct about the 4343 using a 1" baffle and therefore the 2405 is flush ..

Rich

[martin2395]

Confirmed :cool:

[tjm001]

Doc, Tom has already found and posted that link in his quest... many of the dimensions on that drawing are not called out. They are simply labeled as various unknowns.


Widget

Hello all,
Back from road trip and about ready to buy materials and start construction on DIY L300s. I think I have enough info on dimensions, but just wanted to verify the radius of the rounded edges. It looks like a 1 inch radius, but maybe 3/4 inch. Does anyone know? Also, is there anything that prevents the glass top from sliding forward or back? Thanks.
Tom

[BMWCCA]

Widget is correct about the 4343 using a 1" baffle and therefore the 2405 is flush ...
Weird that the 4345 is not flush, isn't it?

[tjm001]

Weird that the 4345 is not flush, isn't it?

3/4 inch is 1/4 inch less than 1 inch. Sorry, but I get a little exasperated sometimes at posts like this.
Tom

[martin2395]

I guess that the 4343 has 1 inch panels because of the 50% of the front baffle being removable (= less rigid).

[BMWCCA]

3/4 inch is 1/4 inch less than 1 inch. Sorry, but I get a little exasperated sometimes at posts like this.
Tom
And I'm probably not the only one exasperated by your apparent hostility.

I found it odd that the baffle would be thicker on the 4343 than the 4345 but Martin was kind enough to offer an explanation.

There's always something to be learned from discussion here, even if it veers slightly off-topic.


No amp-sharing for you!

[tjm001]

I apologize. That extra glass of wine last night pushed my frustration level over the edge of my baffle board.
Tom

[Mr. Widget]

I apologize. That extra glass of wine last night pushed my frustration level over the edge of my baffle board.We all say dumb things at one time or another... I'd love to remove dozens of my posts!

On that and continuing the baffle OT discussion, I am surprised no one has corrected me on the 4350/55 baffle thickness. I posted that this was the one example of a 1" thick baffle, but looking through the catalog pics, it would appear that I was confused and the 4343 with it's rotating front baffle is the exception not the 4350/55 as I apparently incorrectly remembered.

In any case, the L300 as most JBLs uses a 3/4" baffle thickness.


Widget

[macaroonie]

Hello all,
Back from road trip and about ready to buy materials and start construction on DIY L300s. I think I have enough info on dimensions, but just wanted to verify the radius of the rounded edges. It looks like a 1 inch radius, but maybe 3/4 inch. Does anyone know? Also, is there anything that prevents the glass top from sliding forward or back? Thanks.
Tom

1" Radius is correct. Nothing to stop the glass moving. You might find it easier to get 10mm glass cut and just make the depth of the inset 10 mm. Saves dicking around with that silly foam.

You may want to read my thread (http://www.audioheritage.org/vbulletin/showthread.php?17238-Backyard-Box-Building-The-Build&highlight=) for some constructional details and info.

Be very careful how you cut that radius , that's a big cutter and could do a lot of damage to your
body parts.

[tjm001]

1" Radius is correct. Nothing to stop the glass moving. You might find it easier to get 10mm glass cut and just make the depth of the inset 10 mm. Saves dicking around with that silly foam.

You may want to read my thread (http://www.audioheritage.org/vbulletin/showthread.php?17238-Backyard-Box-Building-The-Build&highlight=) for some constructional details and info.

Be very careful how you cut that radius , that's a big cutter and could do a lot of damage to your
body parts.

Thanks Macaroonie. I appreciate your information. I agree with the danger of the 1 inch cutter. I was hoping against hope that it was 3/4 inch. That's the biggest router cutter I have. The 1 inch cutter is expensive too. I think I'll farm out the radius job. Thanks again.
Tom

[Mr. Widget]

The 1 inch cutter is expensive too. I think I'll farm out the radius job. Thanks again.Farming it out is an excellent idea. Fingers and body parts are worth more than the cost of having a shop with a large shaper mill the wood for you. I'd suggest you make extra. I'm sure there will be a "set up" charge and if you screw up a piece you'll be glad to have an extra piece of lumber.


Widget