[Ozrikconan]

Newbie here.  Allow me to jump right into the fire.
I think mdf is junk material for building.  I know is is supposed to provide damping but the real reason spkr mfgrs use it is that its cheap.

If i use plywood with bracing and norez will i get a good performing spkr out of it?

[Argoncat]

Tech Ingredients did a DIY speaker from ply with a thin CDL (constrained damping layer) in a recent video; https://www.youtube.com/watch?v=EEh01PX-q9I. In that video he discusses and experiments with damping and stiffness of MDF and Ply.  I would expect a 100% ply system, would be decent, especially if you could use a CDL laminate of ply. 

[Peter J]

No void plywood could certainly work. Something like Baltic Birch or Appleply.

Cheap is not the only reason it's used.

I don't have lots of love for the stuff, but it does have virtues. The MDF I cut enclosures from is dead flat, nearly homogeneous, consistent in thickness and machines really well, but it's not garden variety MDF. Plywood, of any ilk, can't make the same claims.

I'd say it has more to do with personal preference than performance.

[Hobbsmeerkat]

MDF can definitely be a mixed bag, most "builder-grade" or "readily available" MDF is definitely cheaply produced and prone to fraying.
There are better quality ones are are moisture resistant, and some that hold up really well to cutting, like Medex, tho it tends to be more expensive.

That said there are definitely good reasons to go with BB plywood, esp the higher quality "marine grade" multi-ply versions, and wont have the issues with fine dust and fryaing like most forms of MDF.

The biggest struggle with Plywood is always the edges/corners which need to be well filled and sanded for clean results, where MDF only need to be cut then sealed with minimal sanding.

But I also know there are people on here that refuse to work with MDF & can still produce an excellent product, & others who dont mind either way.

It's really down to where your preference/skills lie.

[WGH]

If you have a high skill set the architectural grade combi-core plywood is a very nice product. The hardwood veneer lays perfectly flat on the MDF underlayment while the plywood core reduces weight while increasing the plywood's strength and stability.

Your tools need to be sharp and deadly accurate along with the ability to consistently cut 45 degree corners within 1/64" or less.

[Ozrikconan]

Good info,  thanks for the replies.

[jcsperson]

If you look at Troels Gravesen's designs, they're all built from plywood.

Now it could be that his crossovers are tuned to a plywood enclosure so using MDF might alter the sound. I honestly don't know enough about that to say.

You might want to contact Danny directly for his opinion.

[jcsperson]

You can hide the edges of plywood a number of ways.

Like this:


I would not do the first one. Miter cuts are a PITA and you can't round over the edges if desired..

Nor the second one if the intent is to hide the plies..

The third could be square or round. I'd do it this way. I don't even think the brace is necessary.

The last one would be fine too, but you would be very limited to the amount of roundover you could use to soften the edge.

[WGH]

The lock miter is the easiest way to get perfect 45 degree corner once you figure out how to do it.
https://www.grizzly.com/products/Grizzly-Corner-Lock-Miter-Bit-1-4-Shank/C1711

[planet10]

We always avoided MDF, using quality plywood, Baltic Birch and then Murphy Ply (hiQuality BB). Stranded/fossilized bamboo plywood is even better but dearly priced (no need for veneer thou)

dave

[Ozrikconan]

[quote author=jcsperson link=topic=173007.msg1828656#msg1828656 date=1603464885

The third could be square or round. I'd do it this way. I don't even think the brace is necessary.

[/quote]

I like the 3rd one also, does it require special assembly fixtures?  Might be fiddly getting 3-4 pieces to Line up while gluing.

[Hobbsmeerkat]

Ideally, you would probably wang to have your outmost facing corner just slightly larger so you can use a flush bit to trim off the excess before rounding the edge. Alternatively, slightly smaller piece to allow it to be filled with a product like bondo and sanded down flush.
Tho the former would be less labor intensive than the latter.

[jcsperson]

I like the 3rd one also, does it require special assembly fixtures?  Might be fiddly getting 3-4 pieces to Line up while gluing.

It's actually pretty easy if you do it in three steps:

1) Glue the hardwood strips to the four edges of the front baffle and back pieces. Let dry.

2) Glue the hardwood strips to the top and bottom edges of the sides. Let dry.

3) Assemble as normal.

The top and bottom edges can be very thin. They're not structural. The top and bottom panels will go inside them.

Most plywood is slightly undersized to its nominal thickness, so "3/4 inch" ply is often really 23/32nd of an inch.

Make the side hardwood strips the full 3/4" square and glue them so the hardwood is proud of the outside face of the panel. That can be cleaned up with a flush trim bit afterward for a perfectly even panel.

Once the box is fully assembled, you can round over the hardwood to the desired radius.

[nickd]

I have used both MDF and BB plywood in Danny’s designs. For open baffle, I don’t think the decision is as critical. For enclosures they both have their own sound. Weight and finish can be deciding factors too.

I think the the best sound for a box is MDF lined with particle board then cotton sound insulation or wool. For big 12” and 15” paper woofers I like old school fiberglass.
The easy way of course is Danny’s NoRez. It is always the sensible option. Blocks that hard surface reflection from coming back through the cone especially when using MDF. It’s a must if you want clean vocals, lower mids and tight bass crunchy bass.

I have a Troles Gravensen box design (Elipticore III) in my listening room right now but with GR Research custom crossovers. Built out of MDF this time (rounded baffle edges) and lined with the high quality Cotton and Wool that Troles supplies with the Kit. No regrets. Ultra transparency.

The material decisions are part of the fun for most of us. Always effects the sound.

[Ozrikconan]

Thanks jcsperson.  That does sound much easier.

[Ozrikconan]

WGH. That is definitely not me. 

[FullRangeMan]

What are important to a DIY builder are the kind of sound the wood will delivery, I managed to find these characteristics in the CommomSense site some years ago, what match with my experience.
MDF:  detailed and bright.
Baltic Birch:  soft and warm sound.
Particle Board:  neutral, mid on BB/MDF.
This topic may help:
https://www.audiocircle.com/index.php?topic=170053.msg1804702#msg1804702

This topic are about inside box stuffing:
https://www.audiocircle.com/index.php?topic=100689.0

[Toecutter]

Not to get off topic ;out of curiosity  has anyone ever tried using azek,pvc board ,to make a speaker.

[Ozrikconan]

Not to get off topic ;out of curiosity  has anyone ever tried using azek,pvc board ,to make a speaker.

I’ll call it on topic.  While we’re at it, what thickness for all materials?  Thinner with more bracing ok? 
I have a small supply of 12mm BB to use up. 

[Peter J]

Not to get off topic ;out of curiosity  has anyone ever tried using azek,pvc board ,to make a speaker.

None of the PVC trim board or decking materials I've investigated are considered structural by their manufacturers. From my experience with they just move too much and would offer no sonic benefit either, not to mention their expense.

What would you imagine their advantage to be?