audio-talk

Toppsy · Posted: Fri Apr 23, 2010 1:42 am Post subject:

Dave,
I have not given anyone else a copy of my personal CAD drawings.
So I'll delete my offer to Jorge OK.

planet10 · Posted: Fri Apr 23, 2010 7:02 am Post subject:

OK

I didn't think you had, and were just trying to be helpful.

But these were going to be commercially available plans (that plan in limbo, and i'll probably give them out on request now that FExx7 have been discontinued Sad

)

dave

Jorge.ar · User Joined: 22 Apr 2010 Posts: 39

hello!!

I will modify the plans you sent me to make a one-piece cabinet. When I finish them I can upload them here, if it's ok with you.

thanks,
Jorge.

Jorge.ar · User Joined: 22 Apr 2010 Posts: 39

Hello again, I have a question.

In Argentina, I can't find good quality plywood, only standard (less plies) and with raw finishing.

Is better to use standard quality plywood or MDF?

thanks,
Jorge.

Toppsy · Posted: Fri Apr 23, 2010 4:44 pm Post subject:

Hello Jorge,

By all means post your build on this forum.

With respect to ply verses other materials. Whilst 18mm (3/4") Birch or Baltic ply is the best material to use, this is a very well braced design and I think you should be OK using MDF. Just buy the best quality grade MDF you can get. By that I mean the most dense grade available to you. I think this would be better than rough finished ply with fewer plys than Birch/Baltic ply.

You can line the MDF with 6mm (1/4") Hardi-Backer Board (available from good ceramic tile shops / retail outlets) to give very dead panels. Just use impact adhesive to bond together. I have used this method on my latest speaker build for the Tang Band W8-1772 drivers to very good effect.

Jorge.ar · User Joined: 22 Apr 2010 Posts: 39

I dont't understand what to do with the 6mm Hardi-Backer Board. do you mean instead of using bad 18mm plywood, using 3 x 6mm Hardi-Backer Board and glue them to make 18mm thick?

thankssss

Ali Tait · Posted: Fri Apr 23, 2010 5:11 pm Post subject:

No,build the speaker box with the best MDF you can get,and then glue hardi-board on the insides for damping.

Toppsy · Posted: Fri Apr 23, 2010 5:21 pm Post subject:

Jorge,

as Ali says.

Check out the following link as this is the very construction method used by Bob Brines of Brines Acoustics: http://brinesacoustics.com/Pages/Articles/Cabinet_Construction/Construction.html

Colin

Jorge.ar · User Joined: 22 Apr 2010 Posts: 39

planet10 · Posted: Sat Apr 24, 2010 6:18 am Post subject:

planet10 · Posted: Sat Apr 24, 2010 6:31 am Post subject:

I can't get very excited about mixing Brines build technique with this design... the MDF & the hardy board will push panel resonances the wrong way. Both lower in frequency & with lower Q. The boxes will not hav ethe same capability to dissapear that they do if built with good ply.

Of course, building it with anything is going to sound better than not building it at all.

What materials can you get? It should be possible to concoct some composite panels that better mimic the properties required than MDF alone. Are you comfortable with fiberglassing?

It will be more work, but the pertectionist in me hates to see a design not meet its potential because of MDF.

dave

Toppsy · Posted: Sat Apr 24, 2010 8:50 am Post subject:

Jorge,

Dave knows best this design than anyone else and what works best for it. So I would go with his recommendations of what building material to use based on what you can buy locally.

Jorge.ar · User Joined: 22 Apr 2010 Posts: 39

In my country I can't find variety... I have one kind of MDF, one kind of plywood...

the plywood is 18mm with 7 layers, but I dont know the origin (what trees).
The MDF is 18mm too, but I cant find the density.
Also I can get another type but dont know the english word. in spanish it's called "aglomerado" (please do a google image search, I cant post links because I'm a new user and I'm not allowed yet Sad

I will try to find the mdf density. thanks!!!

Jorge.ar · User Joined: 22 Apr 2010 Posts: 39

the MDF density is 730KG/m3.

Jorge.