Harbeth Super HL5<I>plus</I> loudspeaker Measurements | Stereophile.com
the 150Hz resonance in that does seem rather high given all the talk about BBC derived speakers. Unless they had to put it there to make it less objectionable. The comments on that article are hilarious tho.
Note: despite being a brit have never heard any of the classic 'bbc derived' speakers from spendor, harbeth et al so have no idea how well they actually work in reality.
the 150Hz resonance in that does seem rather high given all the talk about BBC derived speakers. Unless they had to put it there to make it less objectionable. The comments on that article are hilarious tho.
Note: despite being a brit have never heard any of the classic 'bbc derived' speakers from spendor, harbeth et al so have no idea how well they actually work in reality.
Bill. I've only heard the Harbeth speakers once, at a demo in Las Vegas. Lovely speakers, but highly colored IMO. The coloration is wood and paper, and thus very pleasant, but very noticeable to me.
Unfortunately I had just come from a big demo in the Magnpan room, where there was no box coloration. The contrast could not have been stronger. I've been accused on this forum of sighted bias - that the Harbeth sounded woody to me because I could see them - but I assure you that was not the case (no pun intended). The coloration was very marked, very wooden. Pleasant, warm, woody. Not accurate, but enjoyable.
Unfortunately I had just come from a big demo in the Magnpan room, where there was no box coloration. The contrast could not have been stronger. I've been accused on this forum of sighted bias - that the Harbeth sounded woody to me because I could see them - but I assure you that was not the case (no pun intended). The coloration was very marked, very wooden. Pleasant, warm, woody. Not accurate, but enjoyable.
This is a helpful discussion. I'm trying to take away some guidelines to follow in a design. It seems the correct approach will be a function of the frequency to be reproduced. Let me assume a 4-way system where each driver sits in its own, independent, enclosure. What should be the guidelines for the materials for each enclosure? In my case, sealed enclosures, should it matter.
Subwoofer (<80Hz): seems like a heavy box made of 3-4" of MDF and heavy bracing would provide the mass needed for these frequencies and also achieve a resonant frequency well above the 80Hz. Correct?
Midbass (80-450Hz): this is the trickiest in my mind. Here we need mass, but need to damp too. Right? Sandwich of 3/4" MDF/ particleboard(limp) /MDF /plywood? I also like the idea of adding the 1/4" rubber sound barrier sheet inside the sandwich, but I find the adhesive part to be a challenge. Those barriers are typically nailed and that would defeat the purpose.
Midrange and tweeter: seems good old Micarta would do very well here. High damping and heavy. Would allow for very good bracing, but that would not be needed.
What do you think?
You want sufficient stiffness to push the first resonance above the passband and then to passively isolate this cabinet from the midbass cabinet. It will require minimal damping. MDF is not particularly stiff and is not a particularly good material for struts in tension.
450 Hz is low enough that in practise a well designed stiff cabinet could also push the resonances above the passband.
High damping is required. High mass and high stiffness are not particularly important when they are not the dominant/controlling force. You also have the option to passively isolate the smaller drivers which tends to be impractical for the larger drivers. The speed of bending waves may also be relevant as was mentioned above.
Last edited:
The vibrational characteristics of MDF, particle board, and plywood panels are very similar, so not must is gained by mixing these materials. There are slight differences, but not near the amount one would guess, especially considering the much greater stiffness of Baltic birch plywood. On your line of thinking, constrained layer damping is a very effective method when properly applied. Or using a panel material that is greatly different, such as aluminum or steel with wood products can work. Laminated bamboo plywood as a panel material is stiffer and better damped than MDF, particle board, and plywood.
See the link below, using a translator if necessary:
HSI :: Luidspreker kast materialen onderzoek
Last edited:
Here is a link with some info regarding cabinet material design.
Qboard | Qln
I have worked with this for over 20 years
When we compared 24mm MDF with damped sandwich design the result was amazing. Then you firs realise how much ordinary "thick" even well braced cabinet sound.
Qboard | Qln
I have worked with this for over 20 years
When we compared 24mm MDF with damped sandwich design the result was amazing. Then you firs realise how much ordinary "thick" even well braced cabinet sound.
When I built speaker cabinets in the 1980's I used chipboard (particle board).
On the next cabinets I used veneered chipboard.
I managed to get my cabinets wet and they just bulged where the got wet.
More recently I have used 18mm plywood to cope with a little damp.
I run a mobile disco so my gear is often outside going into or leaving gigs.
On the next cabinets I used veneered chipboard.
I managed to get my cabinets wet and they just bulged where the got wet.
More recently I have used 18mm plywood to cope with a little damp.
I run a mobile disco so my gear is often outside going into or leaving gigs.
Constrained layer damping can work well if the low order cabinet resonances lie in the passband of the driver/s. This is not the case for subwoofer cabinet or, possibly, the midbass cabinet where the objective is high stiffness with only modest levels of damping being required. Typical constrained layer damping (e.g. 12mm structural layer, 3mm damping layer, 6mm constraining layer) give up a significant amount of stiffness in order to get high damping. It can be a good approach for a single cabinet handling all frequencies or a single cabinet handling midrange frequencies but is a lot less so for separate woofer or subwoofer cabinets.
And I think this is why I have never gone out my way to listen to them. I have this belief they will sound like that. Whereas I love ATC monitors, but never got them to image correctly in demos so passed on those too and headed for hybrid ribbons...then moved back to UK with tiny rooms. ah well.
But I do wonder if that is the fault or harbeth or the fact that their target audience wants that (classic 60s bbc sound) so they deliver.
Pro-core 2 is a practical material for smaller cabinets, and it is a reasonable price too (4x8 Oak under $70).
http://www.menards.com/main/store/20090519001/items/media/BuildingMaterials/BM_TimberProducts/Prod_Tech_Spec/SPEC_1252170.pdf
Hardwood Plywood | Ash, Birch, Cedar, Maple, Mahogany, Oak, Walnut & Fir - Hardwood Plywood: Timber Products
Pro-Core MDF
Thin MDF crossbands on the face and back, and a lightweight veneer core make for a superior laminating surface, panel stability, and good machinability.
You can also get the crossband layers in particleboard for higher damping. The veneer core gives good screw retention. About a dozen different face veneers available.
Sing Engineered Lightweight Plywood
These guys make the foam core stuff asked about earlier, $128 or so a sheet.
http://singcore.com/wp-content/uploads/2014/09/Honeycombveneeredpanels1.jpg
They buy this stuff at work with what looks like Masonite faces.
http://www.menards.com/main/store/20090519001/items/media/BuildingMaterials/BM_TimberProducts/Prod_Tech_Spec/SPEC_1252170.pdf
Hardwood Plywood | Ash, Birch, Cedar, Maple, Mahogany, Oak, Walnut & Fir - Hardwood Plywood: Timber Products
Pro-Core MDF
Thin MDF crossbands on the face and back, and a lightweight veneer core make for a superior laminating surface, panel stability, and good machinability.
You can also get the crossband layers in particleboard for higher damping. The veneer core gives good screw retention. About a dozen different face veneers available.
Sing Engineered Lightweight Plywood
These guys make the foam core stuff asked about earlier, $128 or so a sheet.
http://singcore.com/wp-content/uploads/2014/09/Honeycombveneeredpanels1.jpg
They buy this stuff at work with what looks like Masonite faces.
The only thing worth bothering with imho is MDF+Plywood sandwich glued together with plywood going inward. Or at very least use MDF for some panels and Plywood for others. I also often use plywood/mdf cabinet with some hardwood panels glued on top of them. This serve both - greater integrity/stiffness and much nicer and easier to work finish as opposed to veneer.
Also filling some empty spaces with sand really helps. No foam can ever beat it for this purpose.
Also filling some empty spaces with sand really helps. No foam can ever beat it for this purpose.
Do you have any information on the stiffness and damping properties? It will be light for the thickness but I don't want thick materials for small speakers. It is potentially stiff but how to handle corners and edges? It is not clear that it has high damping which is usually the most important property and the most difficult to achieve.
I don't wish to be overly negative because composite materials are almost certainly the way to go but most are not going to have optimum properties for speaker cabinets. Compressed resin impregnated ply is an appropriate material but I am not aware of a source that is not far too expensive to consider. Anyone? Constrained layer damping is a bit of a fiddle but is DIYable and can work well with appropriate damping and constraining layers. It may be the most practical approach at present for a high performance speaker cabinet. It also seems to be becoming increasingly available ready made as flooring for boats, railway carriage, stages,...
"Do you have any information on the stiffness and damping properties? "
You may find it here:
- Documents: Timber Products
If it's not there, I'm sure the company can send you a file when you request it.
You may find it here:
- Documents: Timber Products
If it's not there, I'm sure the company can send you a file when you request it.