Will these do? AR 70s

[neevo]

The L36 cabinet is a much simpler design and makes cutting the MDF significantly easier as I'm basically creating simple boxes. The magic will come out in the grills and finishing work (how I get the edge on the front baffle, the rebate around the back panel, the veneer). I mocked up the shape in Sketchup to make sure it would all work and look reasonable. I haven't worried about the internal volume yet as I have the internal baffle that I can adjust to get the right volume. The dimensions are the exact same ratio as the L36 but a little smaller to make them a little more manageable:



Walnut veneer on the top, bottom and sides and matt black paint on the front and rear. Now to mock up the grills.

 

[neevo]

OK, I've finished the 3d drawings and I think I'm ready to go. Worked out the old internal volume of the old cabinets and used that to get the new ones right. Then I was able to rework the cabinet dimensions a fraction so that I could double up the back wall and have the right internal volume with an added brace in accounted for too:



Next up I looked how I would replicate the front edge of the cabinets. The original L36's seem to have a slight bevel on them which means the black fronts show through a tiny bit with the grills on. I like this touch and think I'll do it with a 0.5mm - 1mm router bit if I can get one:



Lastly I finished the design of the grills too. Just to get it clear in my head how I'll build them. These still need a 1-2mm sheet of MDF over the top as a final skin but I'm not sure how to replicate that in Sketchup, so its not on here, but it will add another 2mm approx. to the depth of the grills taking the sides to 18mm and the front of the point to 36mm:



I think the proportions are lovely of the originals hence why I wanted to maintain them strictly. These will be slightly smaller than the real deal and of course sealed but I think I'll prefer the look of these over replicating the original AR design and I have all the MDF, veneer, 1% caps etc ready to go already, so no investment.

I'm also going to have a go at having concealed grill frame holders. The current plan is to use rare earth magnets with a tiny recess in the front baffle to locate the magnet from the grill frame to stop them drooping. Fingers crossed I can make it work as I think a small, perfect hole would be a sleeker touch that a grill post off the front.

 

[GD70]

OK, I've finished the 3d drawings and I think I'm ready to go. Worked out the old internal volume of the old cabinets and used that to get the new ones right. Then I was able to rework the cabinet dimensions a fraction so that I could double up the back wall and have the right internal volume with an added brace in accounted for too:

View attachment 1082275

Next up I looked how I would replicate the front edge of the cabinets. The original L36's seem to have a slight bevel on them which means the black fronts show through a tiny bit with the grills on. I like this touch and think I'll do it with a 0.5mm - 1mm router bit if I can get one:

View attachment 1082276

Lastly I finished the design of the grills too. Just to get it clear in my head how I'll build them. These still need a 1-2mm sheet of MDF over the top as a final skin but I'm not sure how to replicate that in Sketchup, so its not on here, but it will add another 2mm approx. to the depth of the grills taking the sides to 18mm and the front of the point to 36mm:

View attachment 1082277

I think the proportions are lovely of the originals hence why I wanted to maintain them strictly. These will be slightly smaller than the real deal and of course sealed but I think I'll prefer the look of these over replicating the original AR design and I have all the MDF, veneer, 1% caps etc ready to go already, so no investment.

I'm also going to have a go at having concealed grill frame holders. The current plan is to use rare earth magnets with a tiny recess in the front baffle to locate the magnet from the grill frame to stop them drooping. Fingers crossed I can make it work as I think a small, perfect hole would be a sleeker touch that a grill post off the front.

Looking good neevo!
Replicating the interior volume is important. The woofers 10 inches?
I have a set of spare AR 10 inch woofers that have been refoamed if you're interested. Shoot me a PM.
Glenn

 

[neevo]

Glenn, let me see how the build goes. If it’s a success I think I’d prefer to have the AR woofers in there so will probably take you up on that offer.

Internal volume was calculated pretty precisely in excel. I’ll get my calculations a final time before I start cutting to make sure it’s within a certain tolerance.

 

[GD70]

Glenn, let me see how the build goes. If it’s a success I think I’d prefer to have the AR woofers in there so will probably take you up on that offer.

Internal volume was calculated pretty precisely in excel. I’ll get my calculations a final time before I start cutting to make sure it’s within a certain tolerance.

No problem. Let me know if you want to see some pics. I bought these as backups for my AR-12's. One of the original woofers had a slight VC rub when I refoamed them. Luckily, I was able to wet and loosen the glue on the basket, and recenter the VC and it is fine. So these are not needed and just sitting on a shelf.
Glenn

 

[neevo]

No problem. Let me know if you want to see some pics. I bought these as backups for my AR-12's. One of the original woofers had a slight VC rub when I refoamed them. Luckily, I was able to wet and loosen the glue on the basket, and recenter the VC and it is fine. So these are not needed and just sitting on a shelf.
Glenn

Are all the 10” woofers the same from AR? Would it affect my cabinet volume calcs by using yours vs the original AR28BX drivers?

 

[larrybody]

Are all the 10” woofers the same from AR? Would it affect my cabinet volume calcs by using yours vs the original AR28BX drivers?

If these were originally AR28BX speakers wouldn't the woofers be 8 in. (204mm) ?

 

[neevo]

If these were originally AR28BX speakers wouldn't the woofers be 8 in. (204mm) ?

That’s what I thought but I read conflicting things about them. I found an AR speaker website that said 8” but then found a thread with someone saying they had 10” woofers.

I was wondering whether they may be AR28BXi’s as they apparently had 10” woofers, but the design of those is totally different.

 

[neevo]

These are the same as mine:

https://m.ebay.com/itm/ar-28bx-10-2...4/111472121258?_mwBanner=1#vi__app-cvip-panel

 

[GD70]

These are the same as mine:

https://m.ebay.com/itm/ar-28bx-10-2...4/111472121258?_mwBanner=1#vi__app-cvip-panel

Looks like a 10 inch woofer.
Carry on!

 

[neevo]

I’m building a PL-514 for a mate. Doing the same basic treatment as mine (Walnut Veneer and Alu feet). The veneer is on and I’m trying a different finish for his as he’s not constrained by furniture that we need to match.

Grabbed a can of Scandinavian Oil (Danish Oil essentially) and I’m very impressed with the depth of the grain and the colour. It will definitely be the finish for the speakers:

 

[neevo]

Internal volume calculations are in and I've managed to get the new cabinet to 0.06% of the old cabinet volume. I think that should be close enough hopefully. Managed to play around with the brace dimensions slightly to get it spot on without adjusting the external dimensions, but ill also router the edges of the brace to which will further reduce the variance (aiming for 0.02%).

Need to do some final checking of the numbers before I get cutting.

The MDF will be made up of sandwiched 12mm and 9mm boards (cheaper that way vs buying 20mm). I'm planning on rough cutting the boards, gluing and screwing them together, then finishing to final dimensions on a table saw to get accurate dimensions.

Also on the test pieces above I've found that veneer sticks very well to brand new MDF vs old 70's particleboard which will make things easier and neater edges.

 

[neevo]

I’m cutting MDF in a couple of weeks and seriously reconsidering how the front and rear panels attach to the body of the cabinets. The main reason is that I’m concerned all the butt joints will show through with the way I have the panels sitting inside the box. This will mean I have not only laminated panels forming the outside but then the front panel will also butt up against the cabinet too.

With the front being painted there are way too many joints that I’m worried will show through afterwards, even with some careful prep.

The idea? Redesign the cabinets a little so that the front and rear panels are not inserted in to the cabinet, but attach straight on to the front and therefore provide a clean front. This will require some thinking as to how I attach them properly beyond glue and pressure (maybe dowels could work if I could guarantee matching them up properly) but it will mean the join will be on the tops and sides where it will finally be hidden by veneer and therefore less likely to show through.

What do people think?

 

[revox-b77]

I’m cutting MDF in a couple of weeks and seriously reconsidering how the front and rear panels attach to the body of the cabinets.

How about adding a real wood edgeband with your profile router in to it?

 

[neevo]

How about adding a real wood edgeband with your profile router in to it?

Can you explain that a little more? I am trying to make sure the design of the cabinets is as close to the JBL as possible and so I really want a totally flat black front panel (no timber). My current idea was to use a big panel stuck on to the front and rear, as this would make all the joins in the body of the cabinet and therefore easy to hide because it will be under the veneer:



This means no joins to cover up on the front (can paint a flat front and rear panel) but also has the added benefit of allowing more meat around the drivers, more front panel area to attach the grills and pretty much no exposed MDF end grain.

 

[revox-b77]

Sorry,
I was looking at the earlier design. Ignore previous advise. What you are doing will work fine. Do you have a biscuit jointer? It is the perfect tool for attaching the front. Cut a bunch of slots in each piece, add biscuit, glue and clamp. Good to go.

 

[neevo]

I don’t have a biscuit joiner but I’ve been looking at that as an option. Looks like the perfect way to align the cabinets and ensure a solid joint.

I’m getting some help cutting the panels so I’m wondering if he has some other tools that I could use (eg a biscuit joiner).

 

[revox-b77]

If you buy me a ticket to Sydney, I'll bring mine along.

 

[neevo]

Spent some time on the project today. Was just going to take the woofers out and measure the cabinets for a final confirmation of internal volume, however as with all things I touch it ended up completely stripped.



Whilst I had them all apart I thought I’d have a crack at redoing the crossovers. I’d bought some Dayton MPT Precision caps and set about soldering them in to the crossover boards.

Here you can see the binding posts were all melted so I wanted to get rid of them anyway.



The Dayton caps are much bigger than the originals so I decided to solder them on the other side of the boards and just have the coils on the backs:



One down:



Both done:



I will hot glue the boards to these 5mm boards and probably look to screw them either on the back baffles or the bottom of the cabinets. I’m undecided at the moment. Backs will mean they will be plug and play but I’m worried about the caps sagging. Bottoms will probably require the leads to the drivers being extended.

Here’s the crossovers done on their boards ready for gluing:



I’ve finally measured the cabinets too as I’m keen to make sure my new ones are perfect on internal volume.

63.5 x 29.0 x 18.6 = 34,251.90 cm3

My work laptop died the other day so I don’t have my measurements to check. But I’ll do that before I cut anything.

I’m also rethinking the binding posts. The large plastic ones I have aren’t exactly glamorous, so I’m thinking of ditching them for some extra long binding posts that will be on the back instead of the large unit I have. Should be much simpler and classier.

Also looking at the woofers, I’m not sure I can be bothered doing all the work on them, @GD70 ill drop you a note to see what the woofers you have would run me.

 

[neevo]

Need to work out a way of getting these binding posts. $65 delivery is a bit steep, even to Australia:

Dayton BPA-38G