Cabinet structure MDF vs HDF - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

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 20th February 2013, 07:11 AM   #1
diyAudio Member
 
Join Date: Apr 2012
Default Cabinet structure MDF vs HDF

hi all,
i would know the main differences between mdf vs hdf in loudspeakers cabinet structure.
which is better ?
is there a measured comparison of the two types....a study based on...

thank you
  Reply With Quote
Old 20th February 2013, 07:45 AM   #2
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
For single layer construction I have found HDF better -- quality plywood even better, and if you can handle the cost, stranded bamboo plywood.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 20th February 2013, 10:16 AM   #3
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
I don't know about measurements with accelerometers etc., but if you compare the MOE values for both you'll get an idea of what they'll both be doing, and what you'll need to do to control resonances.
  Reply With Quote
Old 21st February 2013, 02:09 AM   #4
twinter is offline twinter  United States
diyAudio Member
 
Join Date: Jun 2008
If you are building a moderate size two system, of say 12 liters or less, use any of the three. Their will be some differences, though not major. Brace well and apply some damping. If your are building a 3 way tower, then things change.

All three materials, HDF, MDF, and plywood (Baltic Birch) do not have significant internal damping, despite the anodotal comments on the internet stating otherwise. A damping factor of 0.1 (Q of 10) is consider good damping, with critical damping at a damping factor of 2.0 (Q of 0.5). Laminated bamboo appears to be stiffer and have greater internal damping, though be aware Ascend Audio mentioned concerns of warping with certain lamination configuration.

See the link for stiffness (Young's modulus of elasticity) and damping factors of some materials:

http://audioqualia2.webs.com/rawdata.htm

Some testing of different baffle materials:
HSI :: van der Hoff Sound Innovations :: Luidspreker specialist (requires translation)

How am I aware of these properties? I am currently in the process of building a three way tower speaker, approximately 41" tall. After years of reading numerous comments about MDF and Baltic birch plywood, I built the cabinet walls of 1" MDF, with a 2" thick front baffle (2 layers), with significant 3/4" Baltic birch plywood bracing. Using the low tech nuckel rap test, the enclosure seemed to ring like a bell at numerous points (a little exaggeration here). I borrowed an accelerometer and a computer with FFT analysis software (no CSD software), and found sharp resonances from 330 to 800 hertz. The Baltic Birch internal braces were even resonating at 400 Hz. This matches what others have posted on the internet for MDF and plywood baffles using Cumulative Spectral Decay (CSD) plots.

I applied epoxy resin with fiberglass and carbon fiber woven roving, epoxy resin with powdered limestone, and extensional damping material to the interior walls. These were efforts to further stiffen and damp the enclosure walls, with some improvement noted though not as much as desired. A good learning experience. Next time will be different.

DIY speaker building has progressed significantly in the last decade. Computer programs (and the associated equipment) such as LspCAD, SoundEasy, and others have allowed us to design crossovers with good amplitude and phase characteristics. In the last several years, harmonic order distortion profiles have be come available to assist in objective driver selection. Hopefully, in the future cabinet and baffle resonances & damping will be more objectively measured and discussed.

Last edited by twinter; 21st February 2013 at 02:15 AM.
  Reply With Quote
Old 21st February 2013, 02:41 AM   #5
twinter is offline twinter  United States
diyAudio Member
 
Join Date: Jun 2008
Another relevent article on baffle materials:

http://whitledgedesigns.com/uploads/CAE_part5_oct08.pdf
  Reply With Quote
Old 21st February 2013, 02:52 AM   #6
Rob41 is offline Rob41  United States
diyAudio Member
 
Rob41's Avatar
 
Join Date: Dec 2010
Location: Northern Michigan
Good information twinter, It's definitely a topic deserving of further attention.

Any idea how much of a reduction in resonant frequencies there could be had by doubling up on all sides and not just the front baffle? Assuming the two layers are closely bonded and free of any voids.

My thoughts for a project later this summer include a very large 3-way system and I've tentatively planned on using 3/4" Baltic birch for the exterior and bonding it to an interior layer of 1" MDF. This coupled with heavy corner bracing making the inside almost octagonal. A plus is that due to their size each cabinet will actually be two separate cabinets.
__________________
Nikko Alpha 650/SAE 2600/SAE 2400/Soundcraftsmen MA5002/Heathkit AA-1800/Heathkit AA-1600
  Reply With Quote
Old 21st February 2013, 03:11 AM   #7
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally Posted by twinter View Post
Laminated bamboo appears to be stiffer and have greater internal damping, though be aware Ascend Audio mentioned concerns of warping with certain lamination configuration.
We had some issues in an early build, but not since.We prefer using the stranded bamboo ply, it is much stiffer.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 21st February 2013, 03:21 AM   #8
twinter is offline twinter  United States
diyAudio Member
 
Join Date: Jun 2008
Rob41, take a look at the constrained layer damping configuration, yielding very efficient damping. This is with stiff inner and outer layers sandwiching a 2mm to 4mm soft damping layer.

Extensional damping is much less effective, composed of a stiff layer and a thick damping layer. For effective extensional damping, the damping layer is 1/2 to 1 times the thickness of the stiff layer. Note the attaching adhesive in this case is an epoxy or similarly stiff glue, differing from the flexible adhesives for constrained layer damping.

More informational sites:

Soundown - peace and quiet for architectural, marine, & industrial applications
E-A-R Specialty Composites

The Noise Manual, 5th Edition, pages 305 - 314
The Noise Manual - Google Books

Last edited by twinter; 21st February 2013 at 03:28 AM.
  Reply With Quote
Old 21st February 2013, 03:22 AM   #9
diyAudio Member
 
Join Date: Dec 2005
Location: Kuala Lumpur
Making the cabinet stiffer pushes the resonances upwards. 300Hz to 800 Hz is already inside the critical 300 Hz to 3 kHz band, so perhaps you need LESS stiffness.

The other point is that thick panels cannot be effectively damped with surface treatments like bitumen pads
  Reply With Quote
Old 21st February 2013, 03:38 AM   #10
diyAudio Member
 
Join Date: Sep 2012
How about the multi-core materials? Has anyone used the material with alternating mdf and ply cores? Any reason to avoid it? Really the best of both worlds for cabinetry, and I'm considering using it for enclosures...
  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
HDF -- why always MDF? jmar Multi-Way 15 28th September 2009 07:13 AM
Canterbury Cabinet Structure thanhVNS Multi-Way 4 31st May 2008 10:55 PM
Port lenght - Thick MDF Cabinet richardtextex Multi-Way 6 26th October 2006 05:27 PM
finishing an MDF cabinet flaevor Multi-Way 9 27th February 2005 11:40 AM
MDF/Sand/MDF cabinet details Petter Multi-Way 25 16th April 2002 02:10 PM


New To Site? Need Help?

All times are GMT. The time now is 09:45 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