Associated with baffle material is treatment for the front surface. I notice Rockport designs in felt faces and Wilson has used felt a very long time. YG and Magico don't bother. ?? |
I'm going to research specs on materials- Chouhan , ceramic, aluminum,steel plate, exotic ironwoods, granite , artificial granite and other new countertop materials, maple, South American cherry woods for the hardness,density and vibration attenuation properties. Will report my findings. Any other materials I should consider? How is the energy disappated with all metal Magico or similar systems? I'm inclined towards Rockports multi-material designs as intellectually appealing and fully expect some combination to be the best bet. Wilson was using lead pads within their walls for mass and damping qualities. Cost and workability factors will be interesting. |
Jonnk. My first idea was to respond "fribbett" as Johnny English said. However, I thought I'd better look up CHOBHAM --and WOW -- what a revelation. I am looking into it. Do you have some available and the blades I,d need to cut it??? ;-)) Where the heck did your knowledge come from? I,d bet not one in a million knows what you,ve described.. |
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Is there a benefit to adding surface area to a speaker? |
Hello S7horton. I've been on hold with this (I think my massive "myocardial infarction" had something to do with that :-) ).
Ready to get back to it now. Looking to go all out for the construction of these little cabinets. I'm considering all aspects of interior cabinet design-to kill standing waves & resonance. I'll be in touch thanks. |
Hello PBNaudio, your input much appreciated. I'm just getting back to this project for 'the perfect cabinet" for the B&W drivers presently in the synthetic cabinets of the B&W Concept 90 CM1s (which vibrate 'nicely' with very little energy input ;-) .
I now have someone who is happy to do the cabinet work as an interesting joint project and has the necessary woodworking tools and skills; as he would like to make speakers for himself from a kit. I enjoy music through the CM1's (with 25 lbs of lead on them) so have time to do what I want. I like to think there may be a better way to provide 'breathing room" behind the cones than simply using a conical opening-which I appreciate as practical- so I want to evaluate more complex ideas. Any suggestions for something more 'extreme'? I'm not the least concerned with diminishing returns-simply going all out--without wild expense. What do you think of a "variably" slotted opening instead of straight cone? |
I've seen a few concrete enclosures. My thinking has been that the Styrofoam will significantly lighten the concrete while not losing anything in strength. Then I think of stacking different materials... one dampens the next, dampens the next etc...
I believe that the epoxy will be another dampening material and equally strong, the enclosure should be very dense and as well damped as any material out there.
No testing, nothing scientific about it, just a hunch that I'll have to try someday. |
Hi Peter. The new epoxy technology is changing decorative concrete cast planters, garbage receptacles, etc. Didn't Thiel use concrete baffles? |
Timlub,
I think Theil and Hales tried that years ago. Then there was the Swedish Rauna and the Danish Avance companies that made the entire enclosures out of concrete. All had a difficult time making any finish stick to these because of the alkalinity of concrete as it cures.
Good listening
Peter |
That's interesting Tim. It invites thinking of other damping materials to put in the concrete. Do you think styrofoam has enough mass to absorb vibration? Maybe lead powder? Lead is not toxic sitting as metal. In fact the way Wilson used it in their speakers would do no damage to listeners either. It was encased in the x,y or z material. There must be other materials as well. My thinking is the styrofoam would virtually act as an air bubble. What are your thoughts? |
I haven't done this, but with so many responses, I'll throw it in, maybe someone can try it. For the past several years, I've been thinking of trying small Styrofoam balls, mixed with concrete and epoxy, poured in a mold and sprayed with an automotive finish... Still may try it someday. |
Unsound, I meant identical to the original speaker face- not- width & height identical; thanks for your comment. |
Chayro - I agree cabinet design is more complex, but he is at least asking the question. And I have vast experience I'm willing to share. So by the end, he'll have some knowledge needed to make good decisions. Would I say that Harbeth and Spendor are based on misguided theories? For the most-part, no but purposefully introducing energy storage and uncontrolled resonances to introduce some 'color', absolutely is a misguided approach. Color can be added without all negatives of a resonant box, reality is it costs money and time, and it's easier/cheaper to let the marketing dept try and convince people that it is actually a good thing.
Regarding baffle dimensions, it's the size of the baffle, position of the tweeter on said baffle, and shape of baffle edges (square, chamfer, roundover, and size of chamfer or roundover) that determine the diffraction signature. Typically with less than a 1" roundover there is a 2-3db diffraction dip around 3000hz. This dip is often accounted for in the crossover by adjusting the knee to bring up the diffraction suckout area. That's broad strokes, but gives a good general idea of what's important. Much better than adjusting the crossover to bring up the diffraction area is to build a baffle/cabinet that eliminates the destructive point-source diffraction. If the designer of the speakers you're building says no account was made in the crossover for the diffraction dip, you can incorporate large roundovers as long as you keep the baffle dimensions within an inch of intended. Because the baffle dimensions also impact the boundary reinforcement of the tweeter, which impacts it's bottom end extension. FYI, the area below the woofer on the baffle is of minimal importance. So if you keep the tweeter located where intended on the baffle (center, left, right), baffle width the same, and distance from top edge of the baffle to the tweeter all the same, then you can for instance make it into a floorstander and keep the tweeter response the same. That can have a slight impact on bass, typically means more reinforcement or more bass. But you're only talking 1/2db to 1db at most.
Ptss - you'd be surprised how much energy even small drivers can dump into a cabinet. The magnet systems are extremely efficient, where drivers are much less efficient is coupling to air. But yes, even with smaller drivers cabinet construction can be critical. |
Thanks Vapor. I have noticed some rosewoods have very high figures for density and hardness; they're sometimes condidered ironwood.I didn't know if the output from the relatively low output B&W would be strong enough to excite granite? |
I'm not sure using identical height and width would be ideal. In some designers more ambitious designs they use triangular baffles, or at the very least sides with different dimensions. |
Vapor1 - You misinterpreted my post. I am saying that the OP
believes that if he builds a heavy enclosure, it will
automatically be superior to the one he has now, which he
believes vibrates. He may well end up preferring what he has
now. I am saying that cabinet design is much more complex
that gluing together some heavy pieces of material. And
Vapor1, if you're saying that Harbeth and Spendor speakers are
built on misguided theories, well - I guess you have the right
to your opinion. |
Chayro - you have things completely backward. It's building resonant, colored cabinets that is completely trial-and-error, and based on misguided theory. Strong, massive, resonance free cabinets ARE better.
The job is to create an instrument as true to the source as possible. And cabinet resonances, intentional or not, are pure 100% distortion that are delayed in time and uncontrollable in relation to volume.
If the designer intends to create a colored/innacurate music reproducer, there are ways one can do that in a controlled and predictable way. Cabinet resonances are not. The reality is that some companies choose to make resonant boxes not for performance reasons but budget reason, they are always much cheaper and much simpler to build. They then tell the marketing dept to come up with ways to obfuscate the truth. |
PTSS, I haven't read every post here, but I think your
premise, that a less resonant cabinet is better, is simplistic
and flawed. Every material, regardless of density and weight,
has a resonant frequency. Companies like Spendor and Harbeth,
who both produce excellent products, have opted to go with a
thinner, more resonant box in order to shift the resonant
frequencies into the range they wished them to be. This takes
time, sophisticated measuring equipment and (most of all) a
clear idea of what the maker wants the finished products to
be. Your approach of just building a non-resonant cabinet is
nothing but trial and error and the misguided theory that
heavy cabinets are automatically better. Just to be clear,
there are many companies using heavy cabinets with great
success, but again, the process is not haphazard. At least it
shouldn't be. My advice - if you don't like what you have,
sell them and buy something you like. Unless off course, you
just want to screw around with a project, which if fine. It's
your stuff and you can do whatever you want with it. Good
luck. |
The best material would have extreme tensile strength and Young's modulus of elasticity, but also high internal damping. Metals can of course have high strength, but very poor damping. And if you search, one can find tables which list the Rockwell Hardness for many different species of hardwood, some can be quite high. And wood of course has high damping. Metals do have the advantage of mass, which means more energy needed to excite resonances, but lack of damping means energy storage or 'ringing'.
Wood in it's many forms is a good compromise. MDF however is typically too low in terms of strength. But there are some high-density ultra-refined MDF variants which are better.
Of the modern materials available today, thermoplastics such as phenolics I would have to say are best. They come in 1000 forms, unfortunately most are very expensive. Spec sheets are also available which list the parameters mentioned above. But some can combine tensile strength higher than 6061 aluminum, AND excellent internal damping. |
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Ptss, I sent you a private message via A-Gon. I would consider selling the CM2 bass modules. |
Rh, would you like to sell your CM2's? I don't see them in your
system. |
"09-10-14: Ptss
How about 3/4 or 1&1/2 inch black granite countertop green glued onto 3 inches thickness of MDF? Very non-resonant?"
Corian would probably still be the better choice. It has the consistency of mdf but is solid like granite. You wouldn't have to mix materials to get the best results. |
Rh I had no idea the CM1 woofer could bottom out. I have always maintained screw torque but never driven the speakers very hard. But even so the cabinets are nowhere near inert. (However I drive them with a 200 watt Spectral amp with ample current; lots of clean power available for dynamics-but even so these little B&W's don't have good dynamics.) Making the baffle inert will improve dynamics considerably. |
I have a pair of concept 90 CM1/CM2. The cabinet for the CM1 is a phenolic material and is completely braced in a matrix (the original matrix speaker). The speaker cabinet sounds inert with the unscientific knuckle rap test. I don't recall what the original baffle material is. Is it phenolic, and how thick is it? I know the cabinet must be completely air tight as any air leak causes the woofers to bottom out. I can't see how you could gain much by changing the baffle material.
Granite rings and really is not a sensible choice in my estimation. |
How about 3/4 or 1&1/2 inch black granite countertop green glued onto 3 inches thickness of MDF? Very non-resonant? |
Magico got back to me and clarified the material used in the front baffle of the S5's is pure 6061 T6 aluminum which is not extruded. Interesting as the finish doesn't feel like aluminium. But today I gave it the knock test & it sure does sound like it! I'd estimate the front baffle is the same, or similar thickness to the 1/2 inch thick side panels (ie: bloody solid). |
The width of baflle influences more the frequency response of the driver, or its spread? |
BTW, Ptss: You mentioned doing the cabinets in black.
Corian has a color called, "Nocturne" that can be
polished to resemble a Piano Black finish. Would look
sharp, with no visible seams and a 1/2" radius, on all the
corners. Personally; I'd dovetail the sides, top and bottom
and install the front and back with dado joints. Talk
about a solid/non resonant cabinet! I can send you a sample
piece, if you want to get an idea of how rigid, dense and
workable it is. |
Of course, Peter. Somehow- I thought you had already covered
that elsewhere and that the OP had replied, in the
affirmative. |
Rodman,
The width and length of the baffle is an integral part of designing a crossover for a speaker. I'd make sure that especially the tweeter sees exactly the same boundaries as in the original design, if the same x-over is to be reused.
I'd agree that rounding over the edges on the front baffle probably will have minimal effect. However don't go making a 7 inch wide baffle 12 inches wide.
Best of luck
Peter |
Corian, Aluminium, carbon fiber all see use in high end speakers. My Magico S5's use some kind of composite material. I should enquire and ask what it is. |
As long as the internal volume and acoustic centers of the drivers remain consistent with the original design; no negatives should arise. Only reduced diffraction, from the baffle. That's hoping that the system was not voiced to compensate for cabinet resonances. To me; anything the the cabinet adds is editorialization and colorization. I don'r want my cabinets adding anything, of their own, to my music. Of course: many appreciate those additions. Diff'rent strokes, etc. |
Thanks Rodman, very interesting about Corian. I like the idea of a curved baffleboard -but-Peter of PBN mentioned the crossover is designed around the precise dimensions of the baffle and I wonder if that means it should also remain flat and square? It's very good to hear it can be built up. |
@Ptss- Some points about Corian; it can worked exactly as
wood(routed/dadoed/sawn/dove-tailed), but should be worked
somewhat slowly. Drills and taps nicely, for mounting drivers
with machine screws and/or clamps(obviating the need for T-
nuts). Dupont makes colored acrylic epoxies, specifically for
Corian, that can be used to layer sheets to whatever thickness
you desire, or to make visually seamless joints in a cabinet.
Unlike wood; it can also be thermoformed, if(for example) you
want to create a curved baffleboard. Versatile stuff!
(http://www.homedepot.com/c/BP_Corian) |
"09-08-14: Onhwy61
I don't know the answer to this question, nor do I even have an opinion, but will the B&Ws sound better with a less resonant cabinet or will they just sound a little different?"
That's an excellent point. Whoever designed the speaker had to make it work with the original materials. Even if you go with a better material, there's no guarantee that it will sound better. |
Daedulus, Rodman makes a valid and very interesting point. Serious woodworkers will know it "wood :-) " be virtually impossible for cabinets of different wood species to react the same to the drivers so they 'wood' all sound different! |
Onhwy, there is absolutely no question that 'cabinet resonances', particularly those on the front baffle, reduce the clarity, dynamics and nuance of the sound due to the basic laws of physics.
I think ROCKPORT TECHNOLOGY website addresses this quite well. In a nutshell the drivers create sound by vibrating. For the sound to be 'just the sound created by the driver' there must be zero other vibrations influencing it. I understand your question as indeed different listeners have different "tastes" in both music and sound--so eliminating vibrations may not make the sound "better" to all; but definitely "different". |
Thanks Zd & Rodman. I'll look into Corian. |
S7horton, will do today thanks. |
Peter, thanks for the heads up on breathing room for the driver. I really appreciate the very revealing photos you attached to your post! |
Thanks Zd. I think the screws on 'virtually' all cabinets loosen over time due to the laws of physics. I am a fastidious about maintaining screw tightness on my cabinets and drivers as I also own a pair of heavily modified JBL 250Ti"s which have a 14 inch bass driver with an ~ 22 lb magnet that has real propulsive force! I'm with you that loose drivers means loose sound. (I am very fussy about stringed classical instruments clarity). On my B&W Concept 90 CM1's one must tighten the entire, unique, one piece baffle to the box as well as the dome tweeter to the baffle. Both loosen even though obviously they're not played that loud. (Yes I take off the baffle from time to time to check the 4" driver.) |
Mr C- Thank you. Never heard of that company. I'd be interested in comparing the sounds of the various species of wood they use(same models/internals/drivers, but different woods). |
Daedulus Audio makes their entire cabinet and baffle from solid hardwoods according to their website. |
I don't know the answer to this question, nor do I even have an opinion, but will the B&Ws sound better with a less resonant cabinet or will they just sound a little different? |
So, Peter- no solid hardwoods? Yes; voidless plywood(ie:
Birch) has always been a good(and expensive) option, for
speaker cabinetry. Probably the most expensive component of
any of Klipsch's early systems. In the 80's; I was using,
"47lb Industrial Roseboard," which was the highest density
fiberboard available. I suppose that would be the
equivalent
of today's, "HDF." None of my home systems were
as large as yours, hence; baffleboards didn't need that kind
of thickness to combat resonances. You guys do some beautiful
veneering. I used to order mine from Bob Morgan. |
Sonus Faber uses solid hardwood beginning with their Olympica line of speakers. |
The front baffles on most of these are made form laminated hardwood, most from 1.625 to 2.125" in thickness. The back cabinets are made from MDF which is veneered then finished or finished in automotive paints.
Good Listening
Peter |
Hello Peter- Saw a lot of talk about veneers, glues and
finishes on that site, but nothing about solid hardwoods, or
cabinet construction. I'm guessing those are your
speakers(PBN). Are you saying that the front baffles(or
entire cabinets) are solid maple? Beautiful craftsmanship,
BTW! |
