How to seal gaps is wood? - Page 3 - diyAudio
Go Back   Home > Forums > Design & Build > Construction Tips

Construction Tips Construction techniques and tips

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th March 2014, 12:04 PM   #21
diyAudio Member
 
Join Date: Feb 2014
Location: Stockport
Quote:
Originally Posted by tinitus View Post
constructing a new bass box right now
and had a few like this one
for strongest possible result I decided to glue the wood plugs with 2-component epoxy
That plywood is not the best quality it will have voids all over the place, high quality birch ply with more ply layers is much better, especially for subwoofers, I'd consider using 4mm bitumen pads for the internal walls or the panels will act like woofers themselves.
  Reply With Quote
Old 15th March 2014, 12:29 PM   #22
diyAudio Member
 
Philosophil's Avatar
 
Join Date: Sep 2013
Could someone please explain to me what is so bad about voids? Is the negative view of voids purely theoretical or is it based on actual empirical testing?
  Reply With Quote
Old 15th March 2014, 12:56 PM   #23
diyAudio Member
 
Join Date: Feb 2014
Location: Stockport
I have a theoretical view on the voids.

I have read that the voids may have loose pieces which rattle about under vibration, because we don't know where the voids are on the panels there could be some next to each other which would make them bigger. For piece of mind I use the highest quality birch ply with 9 ply layers in 18mm. Its much stronger than 6 or 7 ply layers and seems to have much less and smaller voids. I believe the more glue layers will help.
  Reply With Quote
Old 15th March 2014, 01:04 PM   #24
diyAudio Member
 
kevinahcc20's Avatar
 
Join Date: Apr 2009
Location: Farmington Hills, MI USA
Voids in the plywood laminates represent a loss of strength in that the bond between plies is interrupted by the void. It also acts to weaken joints where the plywood is then edge-glued in an assembly in that the void will interrupt the continuity of the bond. The impact is obviously a function of the percentage of the material that contains voids. Even the best 13 ply material may show a few small voids where individual strips of a ply meet. Practically speaking the number and size of voids in the plys are a good indicator of the care with which the plywood was manufactured. A producer who is careless about the alignment of plys might also be careless about the adhesive chemistry, the temperatures and pressures used during lamination, etc. All you need to do is rip a sheet of plywood and have major voids and delamination revealed to understand that it is best to begin a project with high quality material if you value the time you spend building.
__________________
Kevin(ahcc20)...I'd rather have a bottle in front of me than a frontal lobotomy!
  Reply With Quote
Old 15th March 2014, 07:06 PM   #25
diyAudio Member
 
Join Date: Feb 2014
Location: Stockport
Well done Kevin, explained things much better than me

Just counted the layers in the plywood I use and its 13 layers, really solid stuff, it's well worth the extra cost.
  Reply With Quote
Old 15th March 2014, 07:54 PM   #26
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
I only found 2 or 3 small holes
all other cuts appear ok, so I'm not worried
surely nothing fancy, but it will be ok
besides, it's not built to last forever
Attached Images
File Type: jpg IMG_1146 40.jpg (172.2 KB, 51 views)
File Type: jpg IMG_1147.JPG (180.4 KB, 51 views)
File Type: jpg IMG_1148.JPG (89.9 KB, 51 views)
__________________
sometimes we know very little, and sometimes we know too much
  Reply With Quote
Old 15th March 2014, 07:57 PM   #27
diyAudio Member
 
Sodacose's Avatar
 
Join Date: Feb 2006
Location: mke, wi
Quote:
Originally Posted by crispycircuit View Post
Cut an old paint stick & trim it to size or sub floor calking.
+1

You can find 1/8" trim stock at hardware and/or craft stores.
__________________
I think my ear just popped a boner.
  Reply With Quote
Old 17th March 2014, 11:57 AM   #28
diyAudio Member
 
Philosophil's Avatar
 
Join Date: Sep 2013
Quote:
Originally Posted by kevinahcc20 View Post
Voids in the plywood laminates represent a loss of strength in that the bond between plies is interrupted by the void. It also acts to weaken joints where the plywood is then edge-glued in an assembly in that the void will interrupt the continuity of the bond. The impact is obviously a function of the percentage of the material that contains voids. Even the best 13 ply material may show a few small voids where individual strips of a ply meet. Practically speaking the number and size of voids in the plys are a good indicator of the care with which the plywood was manufactured. A producer who is careless about the alignment of plys might also be careless about the adhesive chemistry, the temperatures and pressures used during lamination, etc. All you need to do is rip a sheet of plywood and have major voids and delamination revealed to understand that it is best to begin a project with high quality material if you value the time you spend building.
That's actually a good explanation, but I thought the most important feature of speaker design was stiffness rather than strength of the material. Perhaps voided material has less stiffness as well, but I wonder if the number voids in a given piece of regular (and much cheaper) furniture grade plywood would make a truly significant, audible difference in the overall sound of the cabinet (particularly a relatively small cabinet). I have my doubts.

The possibility of loose material vibrating is another matter. That would truly make a significant difference to sound quality, but has anyone ever had this happen? I'm just curious about the real chances or possibilities of this happening (as opposed to the purely theoretical possibility that it can happen). After all, if the chance is very low, then the difference in cost between regular and baltic plywood (particularly in certain regions) may be more difficult to justify for some people.

I also like the idea of looking for clues regarding the quality of the workmanship of the product. But you can do that with regular plywood as well (visual and tactile inspections of the plywood boards can help).

I'm just worried that all this talk about baltic plywood has taken on a certain normative tone that would unfairly pressure people to buy the more expensive baltic plywood when the normal furniture grade plywood would serve just as well (in real world listening tests). The difference in cost might be significant for some people and I'm not sure there is a corresponding proportional difference in audio qualities between one grade and another, that's all. If there's not, then most people may well be justified in going with the less expensive furniture grade plywood without feeling like they're compromising the quality of their speakers in any significant way.
  Reply With Quote
Old 17th March 2014, 12:26 PM   #29
diyAudio Member
 
kevinahcc20's Avatar
 
Join Date: Apr 2009
Location: Farmington Hills, MI USA
It isn't necessary to buy high end Baltic birch to get sound plywood. The challenge is knowing the quality of the plywood as it sits on the rack in the store. If I go to my specialty plywood supplier and pay $90 for a 4x8 sheet of prefinished maple plywood, my experience is that it will be sound and essentially void free. I know this because he supplies professionals building cabinets for a living who won't tolerate substandard material. Recently I have bought two sheets of "furniture grade" birch plywood at the local Home Depot for about $40 and been pleasantly surprised to find it of good quality as I ripped it down to make plinth bases for my recently built kitchen cabinets. It is certainly good enough to make speaker cabinets. But I also know that big box stores sell plywood of dodgy quality as well that literally comes apart at the seams. So in DIY speak, you can get quality transistors from eBay sellers, but it's a crapshoot so many of us restrict our shopping to Digikey, Newark, etc. Plywood is similar in that there are suppliers with consistent quality at higher price or you can take your chances in pursuit of a bargain. Good luck!
__________________
Kevin(ahcc20)...I'd rather have a bottle in front of me than a frontal lobotomy!
  Reply With Quote
Old 17th March 2014, 06:00 PM   #30
diyAudio Member
 
Join Date: Feb 2014
Location: Stockport
Yes Phil I think cabinet stiffness is more important than material strength, hence why bracing producing a great affect on the cabinets vibrating. I think this thread was recommending people to buy better quality birch ply when I think its all personal choice. I like to make my cabinets as soundproof as I can yet I still like the sound of cabinet walls from 12mm birch ply in certain types of music. My first cabinets (20 litre 2-ways) I made from cheap low quality plywood (7 layers) from a wholesaler and it sounded awful, so i went out and bought MDF with same cabinet size and bracing and it sounds much better for bass (my speaker design intention) am now putting a 4mm plywood skin over the MDF and a 'knucle test' is much better. Am currently helping a friend with his first project too with high quality birch ply and I love the stuff, harder to work with though. Sounds bizarre but I've found that shouting at different materials of wood the same size gives a good idea of the differences between them, loudspeakers will be totally different of course. As Kevin also says it's the quality of workmanship that matters a lot.

Last edited by Stewart Holmes; 17th March 2014 at 06:10 PM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Digi-Gaps xstreme Software Tools 0 14th April 2013 03:57 PM
seal wood on inside of speaker cabinet? pizzachef Construction Tips 2 5th September 2011 07:19 AM
seal wood inside cabinet pizzachef Full Range 23 2nd September 2011 12:10 AM
Spark gaps on output transformers tomchr Tubes / Valves 8 19th February 2011 09:51 AM
Gaps in my horn - a major problem? wixy Full Range 6 7th September 2007 12:18 AM


New To Site? Need Help?

All times are GMT. The time now is 05:19 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2