[Groundzero]

Hi everyone,

I'm building a couple pairs of N3S speaker cabinets for practice and want to try doing solid hardwood front baffles. I did some quick math to find out how much of the baffle would actually be left. I found that once the holes are cut out, and the 3/4" border that'll be glued to the MDF pieces is taken into account, only 40% of the baffle remains. I don't imagine that it would change the acoustics too much but I thought it wise to ask before I get cutting.

If it would change the sound, is there something I can do it minimize the effect? I thought about building normally with a MDF baffle, then adding on the hardwood over it. However, then the front baffle would be approx. 1-3/4" thick and I thought that might have a negative effect too.

-Kristian

I'm hoping they come out well so I can sell them to help out Gary 

[S Clark]

Actually, the added thickness also means extra strength on the weakest point of the speaker- the front baffle where the holes are cut.  Go ahead and laminate your hardwood to your mdf and it will reduce any resonance in the hardwood, just router the back of the hole with a 3/4 roundover bit to reduce back pressure on the woofer.  Several folks have designed the N3S and the AV3 with a decorative front piece, much like the Salk Songtower shown below.

[Groundzero]

I saw some pairs like that in the N3 picture thread, but thought it was purely decorative. Thanks for educating me. 

[Peter J]

Bear in mind that the hardwood will move at much different rate than the MDF.  Laminating the two is considered bad practice in the cabinet making world and I've seen plenty of evidence that would keep me from doing what you suggest without accomodating that differential movement. Mother Nature will win eventually, and she's patient!

It's surprising to many folks how much hardwood moves in response to humidity and temperature swings, some species more than others, but all expand and contract, particularly acoss the grain.

 If I were doing it, I mechanically fasten the front without glue, allowing independent movement via slotted or oversize holes.

[S Clark]

They will absolutely absorb water differently, and I would never suggest hardwood over mdf for the whole box, but do you think it would separate or warp on a part of the front baffle approx 10" by 24"?
  What do you think, Peter?

[chester_audio]

I wonder what Lou Hinkley does? Hardwoods seem to be working "ok" for him. 

[Danny Richie]

You definitely want to line the back side of the hardwood with MDF.

The expanding and contracting rates of the different material will not be an issue with one panel only. Now if the whole box were done that way then there would be some issues.

Just be sure and add a large radius to the back side of the woofer hole as the baffle gets thicker.

[ebag4]

Just be sure and add a large radius to the back side of the woofer hole as the baffle gets thicker.

Although I didn't use a hardwood baffle on these (see pic) I actually made the woofer holes in the main box larger than the required cutout and rounded them off in the back to eliminate the possibility of additional back pressure to the woofer.





Best,
Ed

[NeilT]

I am no expert, but this worked out for me, so far.















I laminated 3/4 inch MDF to solid cherry on the bottom half of my OB7's.
The top half is 3/4 inch cherry to 3/4 inch cherry.
Danny, at the time, said this would not create any issues, structural or sonic.
They sound fantastic.

Neil

[Peter J]

They will absolutely absorb water differently, and I would never suggest hardwood over mdf for the whole box, but do you think it would separate or warp on a part of the front baffle approx 10" by 24"?
  What do you think, Peter?

This may well be a question of theory vs practice. I can't say that it would cause an issue in any significant way, it isn't a huge piece of lumber. Initial moisture content, humidity of the house and local climate are also factors which may have an effect over the long term. I probably error on the side of overbuilding...just 'cuz I can and enjoy it.

 I don't think we're talking about a structural failure even in the worst case scenario. If your solid face piece were absolutely flush with MDF /veneer sides and it was a surface finish like lacquer or poly, I'd expect to see hairline crack in finish over time and you'd likely be able to snag it with you fingernail.

In most of the examples I've seen, there is a parting line or offset or groove where facia piece meets cabinet, so any differential movement is kind of swallowed up in this detail. This is fairly common on even high quality furniture, check it out next time you're in the store.