[naboo]

Hi

I'm sure I saw a thread where Mike showed how he built the X-LS Encores in maple over an MDF Frame. I can find pics of it on the sticky thread, but I can't find the actual build thread. If I remember correct, the front side of the speaker was only the maple, no MDF.

Is it okay to do this? I've read several times that MDF has an even density distribution, and that's why it's so important not to use something different throughout...but perhaps it's fine to use on the front side only? I'd really appreciate some views on this.

I'm considering using a very hard, heavy, dense wood for the front.

[hawkeyejw]

This thread? https://www.audiocircle.com/index.php?topic=161891.msg1724559#msg1724559

[mlundy57]

Using solid baffles is not ideal. The only reason I did it was because I already had the carcass (top, bottom, and sides) built to the plan specs. If I had laminated the hardwood to MDF, then glued it to the carcass, there would have been MDF edges showing. If I were building the cabinet from scratch I would build the carcass 1-1/2" deeper so I could inset a 3/4" MDF baffle on both the front and back. This keeps the internal volume to plan specs. I would then laminate the hardwood to the MDF baffles. The thickness of the hardwood laminate would depend on the size of roundover I planned to put on the baffle edges. The laminate would have to be thick enough so that once the roundovers were cut, no MDF showed through.

[hawkeyejw]

Using solid baffles is not ideal. The only reason I did it was because I already had the carcass (top, bottom, and sides) built to the plan specs. If I had laminated the hardwood to MDF, then glued it to the carcass, there would have been MDF edges showing. If I were building the cabinet from scratch I would build the carcass 1-1/2" deeper so I could inset a 3/4" MDF baffle on both the front and back. This keeps the internal volume to plan specs. I would then laminate the hardwood to the MDF baffles. The thickness of the hardwood laminate would depend on the size of roundover I planned to put on the baffle edges. The laminate would have to be thick enough so that once the roundovers were cut, no MDF showed through.

I've wondered about the approach of building the internal cabinet to spec and then laminating hardwood on top - is there any impact on the crossover design for the baffle step loss based on the added width? Or is it not enough of a difference to impact the sound?

[mlundy57]

One way is to build with 3/4” MDF, laminate the hardwood to it, then increase the size of the roundovers form 3/8”  to 3/8” plus the thickness of the hard wood.

Another method would be to build the cabinet out of 1/2” MDF, mill the hardwood to 1/4” thick, then laminate it to the MDF. With this method the cabinet is the same dimensions as the plans.

[naboo]

This thread? https://www.audiocircle.com/index.php?topic=161891.msg1724559#msg1724559

Much obliged! No idea why I couldn't find it 

[hawkeyejw]

One way is to build with 3/4” MDF, laminate the hardwood to it, then increase the size of the roundovers form 3/8”  to 3/8” plus the thickness of the hard wood.

Another method would be to build the cabinet out of 1/2” MDF, mill the hardwood to 1/4” thick, then laminate it to the MDF. With this method the cabinet is the same dimensions as the plans.

Interesting, I was thinking the larger radius on the corners would cut away too much material and that you'd end up with MDF showing through on the edges. I think that's the method I'd go with... I don't much like working with 1/2" panels.

Thanks for sharing.

[hawkeyejw]

Much obliged! No idea why I couldn't find it 

No problem, I like looking at build thread photos anyway so I didn't mind looking for it.

[naboo]

One way is to build with 3/4” MDF, laminate the hardwood to it, then increase the size of the roundovers form 3/8”  to 3/8” plus the thickness of the hard wood.

Mike - apologies, I must sound like an idiot, but is it possible to explain or show a picture of what you mean by roundover here? I've never built these and I can see on the plan that the backside of the woofer hole needs at least 3/8 radius or round over.

Maybe it'll make sense once I have the woofer and can look at it.

[Hobbsmeerkat]

Mike - apologies, I must sound like an idiot, but is it possible to explain or show a picture of what you mean by roundover here? I've never built these and I can see on the plan that the backside of the woofer hole needs at least 3/8 radius or round over.

Maybe it'll make sense once I have the woofer and can look at it.

Round over basically means using a 3/8" router bit to round off the inside edge of the woofer hole, to prevent hard reflections caused by a sharp edges within the cabinet.

[hawkeyejw]

Mike - apologies, I must sound like an idiot, but is it possible to explain or show a picture of what you mean by roundover here? I've never built these and I can see on the plan that the backside of the woofer hole needs at least 3/8 radius or round over.

Maybe it'll make sense once I have the woofer and can look at it.

For reference, this is the back side of my X-Static baffles.

[mlundy57]

While the plans don’t call for a roundover on the outside of the front baffle, sharp corners can cause reflection issues so I usually put at least a 3/8” roundover on the vertical edges of the front baffle.

My earlier description wasn’t really clear on this. You pretty much want the size of the roundover to match the thickness of the hardwood. What you are trying to accomplish is have the roundover end at the seam betweenthe front baffle and the side. This makes a nice clean transition.

If the overall width of the finished baffle is more than what the plans call for, it will affect the baffle step loss. The roundovers mitigate this by reducing the effective width of the baffles. If the width is a little bit off you should be OK.

As you can see, using this technique requires some up front planning and attention to detail on how you need to modify the plans and/or edge profile to end up with proper dimensions both internally and externally.

While building to the plan specs with MDF then veneering is a beginner to intermediate level project, doing a custom milled hardwood laminate like I did is an advanced project requiring specialized equipment and skills whether you use hand tools, machines, or a combination. In my case I have a band saw with a 12” resaw capacity, a 15” helical head planer, and a 16/32” drum sander. These are the machines I used to take the 10’ long, 8/4 rough cut board down to the finished pieces I used in the build.

Mike

[hawkeyejw]

All makes sense and is interesting stuff, Mike. Thanks for taking the time to share.

[naboo]

Thanks for the comprehensive information Mike - things are starting to make a bit more sense for a beginner like me. Part of what I didn't realise is the plans is that the radius is the radius of the round-over, so I'll make sure that it gets done an the back of the woofer.

I'm going to try my luck and keep asking questions - if I'm being a pain feel free to ignore them

While the plans don’t call for a roundover on the outside of the front baffle, sharp corners can cause reflection issues so I usually put at least a 3/8” roundover on the vertical edges of the front baffle.

My earlier description wasn’t really clear on this. You pretty much want the size of the roundover to match the thickness of the hardwood. What you are trying to accomplish is have the roundover end at the seam betweenthe front baffle and the side. This makes a nice clean transition.

Is my understanding correct that you are talking about the outside facing vertical of the front-baffle? I would never have imagined that this could affect the sound - I would have assumed that the enclosed parts affect it more so just want to make sure.

If the overall width of the finished baffle is more than what the plans call for, it will affect the baffle step loss. The roundovers mitigate this by reducing the effective width of the baffles. If the width is a little bit off you should be OK.

Ok, even though I don't know what step-loss is, the width makes sense. Because you laminated a thick piece of wood on the side, you had to reduce the overall width of the front baffle and the rounded edges achieves that. 

As you can see, using this technique requires some up front planning and attention to detail on how you need to modify the plans and/or edge profile to end up with proper dimensions both internally and externally.

Absolutely. To add a bit to the confusion, in South Africa we use the metric system and I can't get my hands on 3/4" MDF (works out to 19.05mm). 16mm and 22mm is readily available. It now looks like I can probably get 18mm. I have planned to ensure that the inner dimensions are exact, but sounds like the outer should also be. Which is more important, or should I do it half/half? Gut feel is still inner is more important.

While building to the plan specs with MDF then veneering is a beginner to intermediate level project, doing a custom milled hardwood laminate like I did is an advanced project requiring specialized equipment and skills whether you use hand tools, machines, or a combination. In my case I have a band saw with a 12” resaw capacity, a 15” helical head planer, and a 16/32” drum sander. These are the machines I used to take the 10’ long, 8/4 rough cut board down to the finished pieces I used in the build.

Yup - fully agree with this point and wouldn't really dream of doing it myself. I have a buddy that has lots of equipment and experience and I'll discuss it with him. I'll probably end up going with the standard MDF build ... but I absolutely LOVE the look of real hardwood, and maybe in time I can build another box.

Again, thanks for your input and for yours, @hawkeyejw - much appreciated.

[naboo]

Had time to read up a bit and answered at least one of the questions myself: the inside of the speaker box is primarily to prevent the waves travelling to the rear from interfering with the waves going to the front - so it is indeed the vertical on the outside of the front-baffle that needs to be rounded.

That then, begs the question why the inside of the front-baffle needs to be rounded. My guess would be to distribute the rear-wave a bit more evenly through the box to absorb it, instead of directing it straight at the rear baffle.