Birch alternative
Printed From: Speakerplans.com
Category: Plans
Forum Name: Scoops
Forum Description: One scoop or two ;-)
URL: https://forum.speakerplans.com/forum_posts.asp?TID=13622
Printed Date: 27 March 2026 at 12:38am
Software Version: Web Wiz Forums 12.08 - https://www.webwizforums.com
Topic: Birch alternative
Posted By: stephenwconcannon
Subject: Birch alternative
Date Posted: 04 January 2008 at 6:19pm
| Nowhere in a 100mile radius sells birch, just different types of ply and shuttering ply but no birch ply. What other ply wood can be used (for super scoops)? |
Replies:
Posted By: josh
Date Posted: 04 January 2008 at 6:41pm
| it took me ages to find a supplyer, in the end it was a specialist woodyard which came up with the goods called lawcris, i nearly gave up and bought some sh*te stuff |
Posted By: stephenwconcannon
Date Posted: 04 January 2008 at 6:55pm
| Im in Ireland though, massive disadvantage. |
Posted By: ceharden
Date Posted: 04 January 2008 at 11:40pm
| You can use WBP plywood (7 or 9 ply usually) but obviously it's not as nice to work with. If you really can't get hardwood birch ply that's probably your best bet. Probably more durable than MDF. Might have to add some more bracing cos it won't be as stiff as Birch. |
Posted By: TONY.A.S.S.
Date Posted: 05 January 2008 at 12:10am
|
All my early cabs, and I mean early, were made from Luan ply. Only a few lams but always had the perfect surface finnish. Mahogany is the material used with this ply. If you use it today I don't think you would hear a differnce in the box as it's heavy and quite dense. The heavy bracing that was used in those days also helped. ------------- http://www.facebook.com/tony.rossell.3" rel="nofollow - http://www.facebook.com/tony.rossell.3 |
Posted By: mykey
Date Posted: 05 January 2008 at 4:47am
You guys keep going on about birch
if its going on the road without covers then use a multi laminate ply, 9plys or more would be better
if you cant get this then use either MDF or HDF and make your self some covers
 simplestop being a bunch of tarts please and following each other like sheep ------------- ......just all them hanging there like giant bananas. |
Posted By: stephenwconcannon
Date Posted: 05 January 2008 at 1:09pm
|
Great info. Thanks for the help. |
Posted By: Calculus
Date Posted: 05 January 2008 at 1:38pm
 That's just not the speakerplans way though... Once somone said something and somones agreed then it becomes part of the speakerplans bible... Ps i used spruce ply to make a very lightweight g-sub... and even though it aint the hardest of wood it sounds alright and after a few coats of paint it's pretty tough.. I'm not suggesting using this to anyone. just saying i'm quite happy because it's a really easy lift. ------------- Always a compromise, You can't have everything... Where would you put it all. |
mykey wrote:Posted By: ToNy MoNtAnA
Date Posted: 05 January 2008 at 3:18pm
18mm marine plywood. Lighter,waterproof, but void free usually. |
Posted By: mykey
Date Posted: 05 January 2008 at 3:50pm
 ------------- ......just all them hanging there like giant bananas. |
Posted By: ToNy MoNtAnA
Date Posted: 05 January 2008 at 3:53pm
It's not that lighter, and you could use MDF for the internals or brace it well. |
Posted By: TONY.A.S.S.
Date Posted: 05 January 2008 at 6:53pm
|
I know people on here get hung up on costs whether through poverty, or sooner have money in the bank syndrome, however, If I wanted to do something that bad or vital, one way or another I would get it done. It might mean a long trip to get the ply. It might mean a bit more research on the web. It might mean getting up early in the morning. In this country you can get all you want for this business. It depends how much you want it. ------------- http://www.facebook.com/tony.rossell.3" rel="nofollow - http://www.facebook.com/tony.rossell.3 |
Posted By: Heathrow_B_line
Date Posted: 05 January 2008 at 7:11pm
I have made mmy mt121 from spruce and they are very light. the only problem is that the outer layer is not as good a finish as birch. for my next midtops i think a birch faced spruce ply would be exactly what i need... nice finish and very light.
for bass i can see that spruce may not be ideal. Personally if i couldnt get birch i would use mdf, its sounds better then birch and if you take care of them during loading in/out you could make them last. as im too poor to have roadies i usually get stuff loaded without any bumps/thumps. all future cabs i build for myself i will use mdf... i live the sound of it and i can live with the weight ------------- Produce a killer sound. Take no prisoners. |
Posted By: stephenwconcannon
Date Posted: 05 January 2008 at 7:52pm
| MDF ?? i though using MDF was a definite no no, not quite sure of the reasons just what i have found through sifting through posts... |
Posted By: Heathrow_B_line
Date Posted: 05 January 2008 at 8:18pm
|
it doesnt hold glues/screws as well as birch, and is heavy but everyone is an agreement it sounds better. ------------- Produce a killer sound. Take no prisoners. |
Posted By: kpippen
Date Posted: 05 January 2008 at 9:59pm
|
Hmmm,...I wonder how MDF would hold-up to the elements if coated with line-X?...
http://www.linex.com/ - http://www.linex.com/
http://www.line-x.co.uk/ - http://www.line-x.co.uk/
It's starting to become a popular coating for cabs in the US...
Kev
------------- turn on, tune in, drop out 
Hey Nipper,...we gotta have more cowbell!!! |
Posted By: mykey
Date Posted: 06 January 2008 at 5:43am
If your going to put them on the road without covers use ply on the external pannels and MDF on the internal pannels ------------- ......just all them hanging there like giant bananas. |
Posted By: mykey
Date Posted: 06 January 2008 at 5:45am
------------- ......just all them hanging there like giant bananas. |
Posted By: Calculus
Date Posted: 06 January 2008 at 5:24pm
never had a problem of my g-sub going walkabout... after all it has two 18"s in it...
Supose someone could nick it easier....
But like HBL said it doesn't have the best of finishes but a bit of sanding filling and painting sorted that. ------------- Always a compromise, You can't have everything... Where would you put it all. |
Posted By: stephenwconcannon
Date Posted: 06 January 2008 at 5:30pm
| right im gonna go for MDF on the inside then shuttering ply outside i think. |
Posted By: Heathrow_B_line
Date Posted: 06 January 2008 at 11:08pm
|
not directly relevent but interesting none the less...
In general:- Birch faced ply: - This is plywood faced with a birch wood veneer. The internal laminates are minimum grade spruce and birch in alternate layers. Birch ply:- All laminates are birch. Face layers are also birch. Standard number of plies for 18mm thickness = 13 MDF:- Chips about 20mm in length from either softwoods or hardwoods are thermally softened before being past through a machine which mechanically refines the chips into bundles of fibres or individual fibres. These fibres are mixed with a synthetic resin then pressed into a sheet. The fibres are randomly arranged within the material. This mat is then pressed again whilst subjected to elevated temperatures and pressures to cure the resin and produce a sheet of the desired thickness. Mechanical properties:- In laymen’s terms, strength is an indication of how much load a material will withstand before failure and stiffness is how much the material will flex, or deform, when subjected to a given load. We are not really interested in the ultimate strength of our sub boxes as they seldom fail, so the material strength is of little use. However, we are interested in how much a box will flex. Therefore, we will concentrate on the stiffness of sub box materials. Eb = Modulus of elasticity in bending. Eb describes how stiff a material is under bending. The higher the number, the stiffer the material is and the less it will flex. It allows us to easily compare the stiffness of different materials. The following properties are all based on 18mm sheet materials: Birch faced ply:- Eb = 2700 N/mm^2 perpendicular to grain 4600 N/mm^2 parallel to grain Density = 11.6 kg/m^2 Birch ply:- Eb = 3400 N/mm^2 perpendicular to grain 4600 N/mm^2 parallel to grain Density = 12.4 kg/m^2 MDF:- Eb = 2200 N/mm^2 Density = 10.8 kg/m^2 It can be seen from the above, that the plywood properties are directional depending on the orientation of the grain. For the purposes of this analysis, we can assume the stiffest properties as sub box panels are generally supported on all four edges. MDF is a homgeneous material and the mechanical properties are identical in any direction. Comparing the Eb values given above it can be seen that the birch based plywood is over twice as stiff as the MDF. Therefore, if two identically sized sub boxes were fabricated, one from 18mm MDF and the other from 18mm birch ply, the MDF box would flex twice as much as the birch ply box. That’s quite an improvement from simply using a different material for your enclosure. Thickness vs. Material stiffness:- Birch ply is expensive and MDF is relatively cheap. It’s often asked, ‘Do I use 18mm Birch ply or 25mm MDF for my new sub box?’ As discussed above, birch ply is a stiffer material than MDF. It’s just over twice as stiff. However, the thickness of the material has a far greater effect on the overall stiffness than the actual material stiffness. Example:- It is common to ‘double up’ on the baffle thickness of a sub box from 18mm to 36mm. You’d imagine that by doubling the thickness, you’d double the stiffness and effectively half the flex of the baffle. However, this couldn’t be further from the truth… By doubling the thickness from 18mm to 36mm you in fact increase the stiffness by a factor of 8. The 36mm baffle will be 8 times stiffer than the single 18mm baffle. This is derived from the second moment of area of the section given by Ixx = (bd^3)/12 Where d is the depth, or thickness in this example. The thickness value is cubed to arrive at the section stiffness. For the full increase in stiffness to be exploited, the baffles should be glued together so the two layers act together in unison under load. A double 18mm baffle is 8 times stiffer than a single 18mm baffle. A triple 18mm baffle is 27 times stiffer than a single 18mm baffle. A quadruple 18mm baffle is 64 times stiffer than a single 18mm baffle. And so on…. By simply increasing the thickness of the material the stiffness overall is increased dramatically. Remember that birch ply is twice as stiff as MDF. However, the original question was ‘Do I use 25mm MDF or 18mm birch ply for my box?’ In this case, the increased thickness of the 25mm MDF will far outweigh the increased material stiffness of the 18mm birch ply. The panels of the 25mm MDF box will be 28% stiffer overall than the 18mm birch ply box. In general, the thickness of the material is king to minimise flex. The thickness will increase the stiffness far more than a stiffer material would. However, by doubling the thickness you also double the weight of the box. For ultimate performance, the stiffer birch material should be used in multiple layers. You will then get the best of both worlds. But it is worth keeping in mind that double the layers of material and the weight of the box will also double. As always in car audio we are faced with a compromise. Box stiffness vs. weight vs. cost. The choice is yours. But for someone constructing a simple 18mm thick enclosure, Birch ply will be twice as stiff and only a fraction heavier than MDF. I know which one I’d go for and I'd double the baffle too whilst I was at it. http://www.talkaudio.co.uk/index.php?option=com_content&task=view&id=91&Itemid=26 - http://www.talkaudio.co.uk/index.php?option=com_content&task=view&id=91&Itemid=26 ------------- Produce a killer sound. Take no prisoners. |