Of the same thickness, MDF is the least resonant and most neutral. Like bamboo and solid woods, birch ply boxes tend to impart a sound signature - typically a leaner, brighter sound than MDF (to my ears).
Weird that aluminum is brought up in a thread about wood derivatives. Aluminum (even "aircraft grade" alloys) will ring unless very thick and carefully braced.
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Here is what I would say about that. How many CONCERT level instruments are made out of plywood or MDF?
Answer = 0
While a speaker is not an instrument in the sense that you can play it, it shares ALL of the concepts of a device, usually some type of chamber in which sound is projected for the audience to hear and enjoy.
It would seem to me that Wood would be the obvious choice.
If the goal is to hear the resonating wood (as is the case with string instruments), then yes, solid woods are certainly the best choice. If it were the most inert and neutral material choice, we wouldn't have such large variations in the design of string instruments. Any experienced guitarist can tell you that sitka spruce and maple sounds brighter than mahogany. Hmmm...ever wonder why the call them "tonewoods?" Further, as mentioned in the white paper linked above, solid woods are not isotropic. They also have too many inconsistencies in terms of density and grain patterns - even with cuts sourced from the same tree. This is why no two string instruments - even from the same luthier - will sound exactly the same. These issues could create problems for pair matching of speakers. |
^ They use relatively thin MDF panels, veneered on both sides. I believe a couple of their models use a combination of ply and MDF. |
@bukirob,
For the majority of loudspeakers, the goal is to have cabinets that produce as little resonance as possible (or in the case of BBC designs - move the resonance away from the midband), that is the opposite of string instruments. Loudspeaker designers want their drivers to do as much of the work as possible, not the cabinet. An acoustic instrument uses the wood body to amplify the vibration of the strings. By your logic, loudspeakers should all be made of thin sheets of tonewoods, in which case the cabinets would produce as much sound as the drivers. One could definitely achieve some interesting colorations with such an approach, and they’d likely sound good with certain types of music, but it definitely wouldn’t result in a flat frequency response, nor would the music sound as intended by the studio engineer.
Your logic is completely flawed. Not only are hardwoods often weaker than wood composites for a given thickness, they resonate more, and behave differently depending on their orientation in the structure. They are quite simply a poor choice for speaker cabinets with the few exceptions of those that are purposely designed to color the sound. |
Phusis,
Neutral sound is of course subjective, however, the majority of loudspeaker designers seek to reduce resonance as much as possible or lower it to frequencies where our hearing is less sensitive. Solid woods don’t suppress resonance nearly as well as composites. An open-baffle design is far more logical than a tonewood box if one wants uncolored, true-to-the-source sound, with little to impede the behavior of the drivers. It’s also worth noting that cabinet resonance is usually heard as distortion - typically a grainy midrange, not something pleasant and complimentary to the sound of the drivers.
If someone wants a speaker that excells at reproducing the sounds of a violin, then certainly, it might make sense to use solid Spruce. Speakers from the likes of Viking certainly don’t sound neutral to my ears, but I’m sure they’re a perfect fit for some listeners.
I suspect some here are simply operating on the logic that MDF and plywoods are inexpensive, therefore, they must be an inferior choice. This might be true if discussing dressers or coffee tables. |
^By that argument, speaker cones should be made of doped skin, like an Ed Gein lampshade.
Speakers are not musical instruments. Their purpose is to create a perfect replication of the recording through air movement, with minimal influence on the signal from the cabinet or diaphragm materials. Anything that resonates during this process is a coloration, an alteration of the original sound. If you use a spruce horn to project the sound of a recorded violin, essentially what you’ll get is the sound of a violin that’s been altered by further wood resonance. One might as well encapsule the violin within another violin. It will no longer sound like a Stradivari, but will sound like a violin made of that cheap, new-growth spruce that the builder got from their local lumber yard. This still might be pleasing to the ear, but if it resonates more (or at a higher frequency where our ears are more sensitive) vs the plastic horn, it is a greater alteration of the recording.
This is why speaker manufacturers tend to use self-damping materials: plastic/ paper/ceramic cones, fabric tweeters and MDF cabinets. Their resonance tends to be of lower amplitude for a given SPL and therefore, they have less of an impact on the original signal. The perfect speaker would be one that produces sound waves while imparting absolutely zero resonance of its own. A solid wood enclosure won’t get anywhere close to that ideal, because it’s highly resonant by nature - great for instruments, not for speakers. |
I would say that because MDF is heavier then Plywood it is going to have a lower resonance point, meaning the MDF will store vibrations longer, much like a heat sink, and release it slowly causing a smearing of the imaging. Then by bracing in an effort to eliminate resonance mass is added, which again lowered the resonance point. Imaging ringing the bell in the tower of London as compared to the bell on a bicycle. Lots of energy off the back of the driver is headed to the cabinet. Another illogical argument based on lack of knowelege of material resonance. Thick and highly braced MDF cabinets have a higher resonance point than thin walled designs like a Harbeth - usually in the >400Hz range. This is what happens with very stiff enclosures. The bell analogy falls apart because each would have to be struck with the same size clapper. You'd be striking the London bell with a bicycle clapper. You're basically referring to the Gandy argument of how materials store energy, problem is, he too has a misunderstanding of materials science. Put a stethoscope on any of his plinths and you'll hear rumble galore compared to a high mass design. |
@soundsrealaudio
Harbeth seeks to control resonance by lowering its frequency to levels below the midband where our hearing is less sensitive. The difference is they’re not trying to reduce the amplitude as many manufacturers attempt (yet fail to do). Your argument was that plywood is a superior material to MDF, well won’t you be surprised to learn that Harbeth uses thin MDF panels combined with bitumen sheets.
You assumed that heavier MDF cabinets will have a lower resonance frequency. The reality is that it’s stiffer and will have a higher resonant frequency - toward the midband and often above 400Hz - not the best approach IMO as this is closer to a "ringing" as you might find in metal cabinets.
I happen to prefer the BBC/Harbeth/Spendor/Stirling Broadcast/Graham approach - whether it’s MDF or birch plywood, they all make excellent speakers. However, all alse being equal, for a given mass, MDF is less prone to resonance than solid wood and plywood.
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As for speakers, sorry to be grinch, but there is no way a cone speaker (except possibly these woofers) in any cabinet made from any material sounds as accurate as speakers that don’t use cabinets regardless of the materials or design parameters. Do not take my word for it. Put speakers in cabs side-by-side with non-cab speakers and see for yourself, please. Been there, done that. For example, the Stirling Broadcast LS3/6 sounds far more accurate and neutral than Magnepan 1.7is, and with more transparency. It’s no contest, those wide baffle monkey coffins are simply better speakers, but don’t take my word for it. I was under the impression that the purpose of the cabinet was to add to the richness of the sound, versus just the speaker itself. Just as the body of violin or bass fiddle adds to the richness of the sound it produces. Is this not true? Not true. The box is meant to load the woofer and prevent the speaker from acting as a dipole, which creates diffuse sound and excessive woofer excursion. Dipoles are typically less efficient than box speakers for a given diaphragm size. If what you guessed was true, speaker boxes would most often be made of thin tonewoods, which is obviously not the case. And no, it’s not due to expense. A thin mahogany box is fairly cheap to manufacture. One can get a brand new mahogany guitar for $200. Most modern speaker manufacturers have a pretty good understanding of speaker physics, believe it or not. That so many here are questioning their use of boxes and MDF is baffling to me (no pun intended). |
All speaker manufactures attempt to raise the resonance of their cabinets since low frequencies are extremely difficult to dissipate. False. The thin wall, BBC-derived approach is to lower the resonance frequencies to the bass region. Since you like to reference Harbeth, read up on their philosophy. Energy can not be destroyed. There is the challenge True, but it can be altered, as into heat. |
@soundsrealaudio
I see the confusion now. You're using the term "resonance" to refer to both frequency and amplitude.
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@richopp, @helomech Thanks for the comment. I am sorry the 1.7s did not meet your requirements. I might suggest some agonizing reappraisal, to quote a ’70s 7-UP commercial.
As you clearly understand, your ROOM is the most important element in any sound reproduction evaluation. Possibly your room was not set-up correctly for the 1.7 experiment? I will admit that this is a real chore and may not ever be right depending upon the room. I have years of experience doing this and can state that there are some rooms that simply do not sound right with dipole speakers. So be it!
HOWEVER, you seem to be an open-minded individual, so might I suggest that you give it another go at a dealer who knows what they are doing in their shop and listen again to a comparable model of non-box and box speakers in the shop where they are all set-up correctly? You might be surprised at the quality of the sound, or not. The objective, of course, is to make sure YOUR chosen system sounds the way YOU want it to in YOUR ROOM! I owned a pair of Maggie 1.7is for about 4 months - after a year long stint with Monitor Audio Silver 8s. I had the Maggies in a dedicated and treated 16x26x8’ room, so they had plenty of breathing space. Power was from a Parasound Halo Integrated. When I first auditioned them, they were being driven by $30K Devialet Monoblocks. I subsequently auditioned them with my own amp and while they were better than the MAs, they didn’t exactly bowl me over. However, I liked them over other speakers I heard that day (in their price range) and took a pair home. Unfortunately, I began experiencing fatigue from their treble. I did an absurd amount of experimenting with placement to alleviate it, but the only thing that worked was resistors in the jumper terminals. That limited their transparency to below that of the MA Silver 8s. A couple months later I heard a pair of Spendor SP100s at Acoustic Sounds. It was a revelation. This was before I began going to audio shows, but even so, I still consider them some of the best speakers I’ve heard anywhere. I subsequently auditioned Harbeths, Spendors and the Stirling Broadcast LS3/6s in my home. Each was better than the Magnepans and by a significant margin, even their imaging. What really struck me was how they produced greater detail, despite being less fatiguing. I settled on the Spendors because they were the most "musical" of the bunch to my ears, however, the LS3/6s were the most impressive regarding typical audiophile terms. To say they were merely better than the 1.7s is an understatement. Knowing what these monkey coffins can do, I simply don’t understand the hype surrounding panel speakers. As for value, I found both the KEF LS50s and Vandersteen 1Cis offered more bang for the buck, even in my large room. I think I gave the Maggies a fair shake. I respect that others like them (they’re not terrible speakers by any means) but I also suspect that some of their devoted fans haven’t heard some of the best that box speakers have to offer. If I’m wrong, then I suppose it’s simply a matter of personal perception - a matter of Laurel vs Yannie. |
Big speakers big problems. Cabinet materials that have a low resonance
are slow to eliminate them. So they store them and release them slowly thereby smearing the image. This is a fact and widely recognized.
Give it up dude, you obviously have not the slightest understanding of speaker physics. I'll await your reply with a claim of BS credentials. |
@kalali, I know this was targeted at someone else but if you don’t have anything productive to add to the conversation you should just skip this thread and move on. If you feel real strongly about your speaker design knowledge/skills, write a paper and send us the link. Personal insults are not welcomed here. That poster is spreading misinformation. He clearly confuses amplitude with frequency - rather basic principles in audio. Even though I pointed this out to him, he continued to spout nonsense as though it is fact. I make no apologies for the ignorance of others. There's far too much of that going on in our culture these days. Peace. |
^Solid wood and plywood are even more susceptible. Solid wood, depending on treatment, will swell, or in the case of low humidity - crack. Plywood will begin to bend in as little as 60% RH. It takes very high humidity (>80%) to warp MDF - the level that would make for an unhealthy household. |
The worst were the Wilson’s. Magico’s were overly deadened to my ears. Anyway, just saying I hear a dramatically improved sound with a well done wood speaker. Harbeth uses this approach as well I believe. The founders of Harbeth and Spendor did a lot of pioneering research into cabinet materials. Both companies now use cabinets made of MDF - and both are widely regarded as producing some of the most lifelike mids in the biz. The problem with solid woods and ply woods is their inconsistency, their susceptibility to warping and greater difficulty in machining. Even voidless birch ply will have slight variations between batches that can make it difficult to create a consistent sound. Musical instruments suffer this same problem. I've played brand new guitars of the same make, model that sounded very different from each other, even after professional setup. |
Vince at Totem makes cabinets impervious to environmental variations. Gotta love these sort of claims. No such cabinet exists, nor will it ever exist. Just as no driver is absolutely perfect, neither is any cabinet or crossover. |
@dave_b Ok Helomech the great...protector of things absolute! Within the normal standards of cabinet design, Totem makes their speakers far less susceptible to various environmental conditions. Their crossovers are special by virtue of quality and tolerances as well as being hardwired by hand. I'm the "protector of all things absolute," yet you use the word "impervious" to describe a speaker cabinet. Seems to me that shoe is on your foot Davey. |
^says the guy with MDF speakers. Interesting. |
Good quality MDF doesn't need finishing on both sides. You can leave the inside surface bare. |
