Hi all!
I have searched here and other sites and I can't seem to find an article or info about what driver specs are favorable for a weak-walled, plastic and essentially "lossy" enclosure. High Qts? low Xmax? High Fs?
I do have an article from my collection of speaker builder where a reader built and tried to sell a kit with flexible walls but he was trying to sell a specific kit and it did not help me much.
I have found interesting articles linked from this forum about the BBC write up of thin-walled enclosures and the benefits of allowing resonance to exist and controlling it to versus futile attempts to eliminate wall resonance. But again I cant find any facts about which drivers, given a choice will work better.
They will be 4" to 4.5" drivers (2) plus tweeter or coax car audio type of setup. I know a plastic flexible cabinet is not ideal but I don't have a choice. Is what it is. I just want do choose the best (but inexpensive) drivers for the job.
I am leaning away from ported as I understand that cabinet rigidity is even more important when ported.
Sealing the enclosure air tight is possible as well as stuffing it but eliminating wall flex is not. Any Ideas on what T/S parameters I should be looking for?
I have searched here and other sites and I can't seem to find an article or info about what driver specs are favorable for a weak-walled, plastic and essentially "lossy" enclosure. High Qts? low Xmax? High Fs?
I do have an article from my collection of speaker builder where a reader built and tried to sell a kit with flexible walls but he was trying to sell a specific kit and it did not help me much.
I have found interesting articles linked from this forum about the BBC write up of thin-walled enclosures and the benefits of allowing resonance to exist and controlling it to versus futile attempts to eliminate wall resonance. But again I cant find any facts about which drivers, given a choice will work better.
They will be 4" to 4.5" drivers (2) plus tweeter or coax car audio type of setup. I know a plastic flexible cabinet is not ideal but I don't have a choice. Is what it is. I just want do choose the best (but inexpensive) drivers for the job.
I am leaning away from ported as I understand that cabinet rigidity is even more important when ported.
Sealing the enclosure air tight is possible as well as stuffing it but eliminating wall flex is not. Any Ideas on what T/S parameters I should be looking for?
I can't see how any driver specs are going to make up for a poor enclosure. That's like asking what kind of tires would help me stop on this car with no brakes.
None. No I am being serious. Weak walled enclosures that flex will always affect the frequency response in a bad way. The in and out of phase reaction will cause peaks and nulls in the response and sometimes will overwhelm the sound coming from the speaker itself. I recall that Speaker Builder article and the science behind it was terrible.Having floating panels like that would kill any bass response as the panels would be moving in an opposite direction versus the speaker cone. Look into damping and stiffening and bracing the plastic walls of the enclosure. At the very least use lots of internal acoustic fill like polyester batting which will help reflections.
Maybe you can contact Harbeth directly and ask them for DIY purposes what drivers specs in general are suitable. Harbeth UK - High quality loudspeakers made in England they do have a FAQ section for other information. If you get an answer, please post it back here for the rest of us.
Apparently contrary to popular opinion, properly designed 'lossy' construction cab alignments can compensate [damp] high Qts drivers to a much lower effective Qtb [c][p] without resorting to mass quantities of stuffing as proven by some of the foam core constructed cabs posted here and other threads: http://www.diyaudio.com/forums/full-range/223313-foam-core-board-speaker-enclosures.html
Plastic construction OTOH will require some form of constrained layer damping [CLD] construction otherwise its delay [decay] characteristics will adversely ‘color’ the driver’s response as already noted.
Vented is actually required for best overall results, so study up on TL and ~aperiodic alignment design theory to learn why.
GM
Plastic construction OTOH will require some form of constrained layer damping [CLD] construction otherwise its delay [decay] characteristics will adversely ‘color’ the driver’s response as already noted.
Vented is actually required for best overall results, so study up on TL and ~aperiodic alignment design theory to learn why.
GM
AudioNote in the UK took up the mantel created by Peter Snell of Snell acoustics. AN speakers are ported two ways with 8 inch woofers. Their cabinetry is 'thin' as well and it's claimed is tuned to interact with the woofers to enhance bass. Here is a claim clipped from AN's site...."The cabinet is lightly braced and little internal damping is used. The cabinet is designed in such a way that it augments and supports the drivers in their task, not unlike the box of a guitar."
The op's project is much more than just a simple mating of some small drivers with a flexible wall cabinet. Much work will be needed to optimize the cabinet resonances to provide synergism for LF ehancement rather than destruction.
The op's project is much more than just a simple mating of some small drivers with a flexible wall cabinet. Much work will be needed to optimize the cabinet resonances to provide synergism for LF ehancement rather than destruction.
tough crowd. No need to overthink it for a tiny speaker, and don't go about it backward. Choose a driver appropriate for the project (including the enclosure size, of course). WinISD Pro allows user-variable enclosure losses to get an idea of worst/best case for bass response. Cover the flimsy walls with tar or rubber pads or whatever semi-flexible goop you can come up with. Also use something lossy between panel joints if that's practical for what you're doing. Add something internal to break up standing waves if you've made a poor choice in cabinet dimensions. Done.
Ah, that nice rich, warm sound of the lossy cabinet. Throw in your high Q drivers, and a tube amp and the sound becomes richer that a Portuguese tart.
Not my cup of tea but understandable why it is/was popular.
Not my cup of tea but understandable why it is/was popular.
I built a pair of Line Magnetic 755EX speakers into a 9mm marine ply cabinet (also suitably adapted from an old WE sound reinforcement design) with lots of pinewood edge bracing but none on the walls, making the enclosure very resonant. It would tell you the time if you knocked on it.
The driver had nothing below 80Hz, so the lack of enclosure heft wasn't a problem, they weren't moving anywhere in a hurry. Ran it off a 2W SET amp (the one in the Twin Audio thread) with Amperex 6GV8 tubes. Very little damping, maybe 2 pounds of lambs wool felt.
Personally, not to my taste, but some listeners were quite impressed. That driver had a field coil, and sounded better at low level of coil bias, which would mean low BL and high Qts, I assume.
The driver had nothing below 80Hz, so the lack of enclosure heft wasn't a problem, they weren't moving anywhere in a hurry. Ran it off a 2W SET amp (the one in the Twin Audio thread) with Amperex 6GV8 tubes. Very little damping, maybe 2 pounds of lambs wool felt.
Personally, not to my taste, but some listeners were quite impressed. That driver had a field coil, and sounded better at low level of coil bias, which would mean low BL and high Qts, I assume.
Here is a link to a Stereophile review of the An-e speaker's measurement done by John Atkinson.
Audio Note AN-E Lexus Signature loudspeaker Measurements | Stereophile.com. Check his cabinet resonance accelerometer test results. JA thinks the resonances will be audible.
Hi,
Lossy BBC style cabinets really do have very good midrange,
best exploited by high quality 2 way designs, at a cost of
some alleged imprecision in the bass. In reality in terms of
overall speaker performance the bass is simply not an issue.
You can't have your cake and eat it, and a box free of
midrange colouration for a 2 way is an eye-opener
compared to the mild limitations in the bass precision.
If anything the low mid colouration makes everything
sound better, including the general bass naturalness.
However "plastic" boxes covers a multitude of real
possibilities, with very different rigidity and loss
characteristics. They are used to great effect
in PA speakers, but it is clearly not a method
that is fashionable for home hifi speakers.
rgds, sreten.
The speakers sound like they are going to be MTM's.
Best option available probably is :
https://sites.google.com/site/undefinition/overnightsensationmtm
Lossy BBC style cabinets really do have very good midrange,
best exploited by high quality 2 way designs, at a cost of
some alleged imprecision in the bass. In reality in terms of
overall speaker performance the bass is simply not an issue.
You can't have your cake and eat it, and a box free of
midrange colouration for a 2 way is an eye-opener
compared to the mild limitations in the bass precision.
If anything the low mid colouration makes everything
sound better, including the general bass naturalness.
However "plastic" boxes covers a multitude of real
possibilities, with very different rigidity and loss
characteristics. They are used to great effect
in PA speakers, but it is clearly not a method
that is fashionable for home hifi speakers.
rgds, sreten.
The speakers sound like they are going to be MTM's.
Best option available probably is :
https://sites.google.com/site/undefinition/overnightsensationmtm
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Thank you for all the replies! Unfortunately I cannot get away from the plastic cab. I usually open up LSDCookbook and go to town using Dickasons advice but I cant in this case. I cant elaborate on all individual replies from you (I have to go to band practice) but thank you for the advice. I have seen some speakers that did use the cabinet resonances as enhancement. I cant imagine getting much "help" from plastic though. I used to work in an home theater store selling Paradigm, Monitor, NHT etc. and one day guys from Germany rolled in un-announced with Bösendorfer speakers for us to demo. I remember their sales pitch being a similar principal theory of cabinet resonance "don't fight it use it!" I don't expect my results from this project to be Hi-fi but I do want the best results I can achieve. Thank you again.
Hi,
But depending on the details of the plastic cabinet you still have options.
However with no details is impossible to give sensible advice.
rgds, sreten.
But depending on the details of the plastic cabinet you still have options.
However with no details is impossible to give sensible advice.
rgds, sreten.
I read an article probably 20yrs ago about using resonant thin wall cabinets. It all seemed very believable, high Q resonances take time to build up so won't be easily provoked by music, the resonances could be placed outside the worst sounding 'muddle' frequency bands, and driver decoupling could get round any shortcomings. That's all I remember about said article.
On the strength of that article and a very good review, I actually purchased a pair of Spendors (forget the name) designed along these lines, they sounded OK in the shop, but I've never been impressed by any shop demos so wasn't expecting much on audition. When I got them home and compared them with my solid 3-way Castles there was no comparison - all the superb clarity my system was capable of had vanished. Luckily the dealer hadn't cashed my cheque and took the Spendors back the next day.
On the strength of that article and a very good review, I actually purchased a pair of Spendors (forget the name) designed along these lines, they sounded OK in the shop, but I've never been impressed by any shop demos so wasn't expecting much on audition. When I got them home and compared them with my solid 3-way Castles there was no comparison - all the superb clarity my system was capable of had vanished. Luckily the dealer hadn't cashed my cheque and took the Spendors back the next day.
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