It is really quite astounding just how good ordinary springs can be when resonance is minimized by tuning the spring to the component load.Exactly what I have found. Use the correct spring constant and appropriate maximum spring load compared to the actual load, apply damping, such as loosely applied thin heat shrink with a hole in it (what I use), or maybe foam inside of the spring, and you should be able to reduce the natural frequency of the damped system to below the audible band. It was a little more than $35 though because it took me a few tries to get the correct combination of springs. Other "design" considerations include what spring diameter and compressed height you want, as well as what number of spring coils might work best for the height of spring you are using. There are lots of choices. With speakers it is good to know the front (under the baffle) is heavier than the rear due to the weight of the drivers so two different spring constants may be necessary. Another thing helpful to me is that my main speakers and my two subs all use Sound Anchor stands, which provide a rigid base for the springs to act against.
Speaker Spike Philosophy
This is a learning exercise for me.
I am a mechanics practitioner by training and by occupation, so I understand Newton’s Laws and structural mechanics and have a fairly effective BS-detector.
THE FOLLOWING THINGS PUZZLE ME, and I would be glad to hear from those who believe they understand so long as the responses are based on your actual experience or on sound mechanical arguments (or are labeled as conjecture). These are independent questions/musings, so feel free to weigh in on whichever ones you want, but please list the number(s) to which you are responding:
I am a mechanics practitioner by training and by occupation, so I understand Newton’s Laws and structural mechanics and have a fairly effective BS-detector.
THE FOLLOWING THINGS PUZZLE ME, and I would be glad to hear from those who believe they understand so long as the responses are based on your actual experience or on sound mechanical arguments (or are labeled as conjecture). These are independent questions/musings, so feel free to weigh in on whichever ones you want, but please list the number(s) to which you are responding:
- Everything I have read recently ("Ask Richard" (Vandersteen) from 15 Feb, 2020, for instance) seems to indicate that the reason for speaker spikes is to hold the speaker fixed against movement induced by the drivers. I have seen in the past other explanations, most employing some use of the term "isolation" implying that they decouple the speaker (from what?) Evidently the "what?" is a floor that is fixed and not moving (let’s assume concrete slab foundation). So to decouple the speaker from the floor, which is fixed, is to . . . allow it to move (or not) as it wishes, (presumably in response to its drivers). These two objectives, "fixity" and "isolation" appear to me to be diametrically opposed to one another. Is the supposed function of spikes to couple the speaker to "fixed ground" so they don’t move, or is it to provide mechanical isolation so that they can move (which I do not think spikes actually do)? Or, is it to somehow provide some sort of "acoustic isolation" having to do with having some free space under the speaker? Regarding the mechanical isolation idea, I saw a treatment of this here: https://ledgernote.com/blog/q-and-a/speaker-spikes/ that seemed plausible until I got to the sentence, "The tip of a sphere or cone is so tiny that no vibration with a long waveform and high amplitude can pass through it." If you have a spike that is dug into a floor, I believe it will be capable of passing exactly this type of waveform. I also was skeptical of the author’s distinction between *speaker stand* spikes (meant to couple) and *speaker* spikes (meant to isolate/decouple, flying in the face of Richard Vandersteen’s explanation). Perhaps I am missing something, but my BS-detector was starting to resonate.
- Spikes on the bottoms of stands that support bookshelf speakers. The spikes may keep the the base of the stand quite still, but the primary mode of motion of such speakers in the plane of driver motion will be to rock forward and backward, pivoting about the base of the stand, and the spikes will do nothing about this that is not already done by the stand base without spikes. I have a hard time seeing these spikes as providing any value other than, if used on carpet, to get down to the floor beneath and add real stability to an otherwise unstable arrangement. (This is not a sound quality issue, but a serviceability and safety issue, especially if little ones are about.)
- I have a hard time believing that massive floor standers made of thick MDF/HDF/etc. and heavy magnets can be pushed around a meaningful amount by any speaker driver, spikes or no. (Only Rigid-body modes are in view here--I am not talking about cabinet flexing modes, which spikes will do nothing about) "It’s a simple question of weight (mass) ratios." (a la Holy Grail) "An 8-ounce speaker cone cannot push around a 100/200-lb speaker" (by a meaningful amount, and yes, I know that the air pressure loading on the cone comes into play as well; I stand by my skepticism). And I am skeptical that the amount of pushing around that does occur will be affected meaningfully by spikes or lack thereof. Furthermore, for tower speakers, there are overturning modes of motion (rocking) created by the driver forces that are not at all affected by the presence of spikes (similar to Item 1 above).
- Let’s assume I am wrong (happens all the time), and the speaker does need to be held in place. The use of feet that protect hardwood floors from spikes (Linn Skeets, etc.) seems counterproductive toward this end. If the point of spikes is to anchor the speaker laterally (they certainly do not do so vertically), then putting something under the spikes that keep the spikes from digging in (i.e., doing their supposed job) appears to defeat the whole value proposition of spikes in the first place. I have been told how much easier it is to position speakers on hardwood floors with the Skeets in place, because the speakers can be moved much more easily. I was thinking to myself, "yes, this is self-evident, and you have just taken away any benefit of the spikes unless you remove the Skeets once the speakers are located."
- I am making new, thick, hard-rock maple bases for my AV 5140s (lovely speakers in every sense), and I will probably bolt them to the bottom of the speakers using the female threaded inserts already provided on the bottoms of the speakers, and I will probably put threaded inserts into the bottom of my bases so they can be used with the Linn-provided spikes, and I have already ordered Skeets (they were a not even a blip on the radar compared to the Akurate Exaktbox-i and Akurate Hub that were part of the same order), and I will end up doing whatever sounds best to me. Still, I am curious about the mechanics of it all...Interested to hear informed, reasoned, and reasonable responses.
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- 140 posts total
Right. I started testing with different springs ordered from eBay. Even once you know what you want in terms of dimensions it is still a lot of trouble to find. That is why I ultimately dumped individual big springs and recommend Nobsound. Not because they are better, but because they are about as good and save a tremendous amount of time and trouble! Townshend on the other hand are not only a whole lot better but save even more time and trouble. The MDF test platform I built was from scrap just sitting around my shop. Knocked em together in an hour or so. Looked ghastly but worked plenty good. When I was seriously contemplating just what it would take to make them look good and be easily adjustable, the whole package, that is when I decided to try Townshend Podiums. Glad I did. Better looking, easier to adjust, and sound way better too. Lots of choices. All of em better than cones or spikes. That is what amazes me. That all these options are so much better, yet the vast majority still have not figured this out. Kind of like DBA, around for 20 years, yet hardly anyone knows about it and half the ones who do argue instead of adopt. Go figure! |
Mijosty, Long winded is my middle name. Anyone who ever spent time on the phone or has met me in person knows this. As not to bicker or argue over points of resonant frequency and amplitudes of resonance continuously forming on “all” vibrating surfaces and hopefully putting us on the same page of understanding, I urge you to review this document. http://www.starsoundtechnologies.com/CMS/uploads/vibration-and-coulomb-friction-2013_001.pdf Regards to renderings on testing: My point was that ‘live environment’ testing results are meaningful only to the designer. I was hoping to pick up more on the studies of driver function, formation from shear waves to compression waves, velocity of various materials and anechoic wave patterns but that would require another half-dozen paragraphs. ⌣ We can perform the same accelerometer testing on your system in our lab that would clearly differ in comparison to your results unless we have the same room sonic environment, the same equipment support systems holding the model, the same racking system holding the test equipment, the same attachments and stand for supporting the calibrated microphone or accelerometer or recording drives and the list goes on. The measurements would greatly differ. Regards to resonant frequency: Any resonant frequency can be changed easily. Based on your postings, my guess is your physical model is not providing you the best information due to the cheap spikes and environmental obstructions limiting the performance of your subwoofer. Changing the resonant point of your test model, say we replace the cheap spikes and put the enclosure on $300 Audio Points or a $500 Platform. The changes in sound quality would improve as would your testing results where you would realize how much further along you are in the process of development. Now place the same model on a $1200 platform and you will also notice how much more effective your design is in sonic as well as the differences in measurement. To prove beyond any doubt that you are ahead of expectations, place the same model on a $2,500 platform and that might show you where your inefficiencies are in the design along with advancing the test criterion and more importantly, really focus on the sonic improvements. By changing the effectiveness of the grounding plane (platform or spikes), the transfer of resonance becomes reality where your book-mentored approach might change as well. *A subwoofer measurably generates less distortion when it is firmly spiked to the floor. I do not know if this is true for a full range loudspeaker that is crossed to a sub at say 100 Hz. This is true regardless of speaker size, mass, material science, construction, or crossover points. If you use a higher end spike, there will be much less distortion to begin with. *Does vibration transferred to a purely electronic device cause audible distortion? It would take a massive series of vibrations or a poorly designed chassis with a cheap footer system where I do not believe any of those exist in today's marketplace however, any device using manmade power will vibrate. Vibrations (mechanical, electromechanical or airborne) establish resonance and clogging of the signal pathways establishing component operational inefficiency. When the inefficiencies are mechanically grounded and transformed into component operational efficiency, one will hear the difference regardless of tube or transistor design. *Designing a decent speaker spike is child's play as is making a decent speaker stand. Locking the speaker to the stand is also child's play as long as you don't mind sinking a few screws into the enclosure. Designing and making a subwoofer enclosure that does not shake or resonate is not so easy. Do you have any siggestions? Yes a few… but first, My experience with subwoofer driver and cabinet development was spent with the engineering team at McCauley Sound and working in the sound reinforcement business with three highly successful sound companies. I was part of a four person team that designed and manufactured over 300 custom subwoofer enclosures in the days of IASCA Tournaments and have participated in the build of a few championship vehicle systems that toured audio and electronics shows. We just placed a pair of twin modified 18” subwoofers into our mechanically grounded Energy Room in Madison, WI to see how much pressure level is required in an attempt to acoustically overload the walls, floor and ceiling. Imagine having the feel and dynamic headroom of a live event in a studio setting? Yet the room is capable of hearing every note and decay defining the difference in sound between two different brand names of woodwind or string musical instruments. http://www.mccauleysound.com/product_overview.cfm?ID=2338 https://systems.audiogon.com/systems/8168 I just wanted you to know, we do have some experience in your field of interest. According to you, developing a "decent" cone is childsplay. Really? We have witnessed a multitude of “decent” vibration management companies come and go over the years, but few remain past the ten-year mark and by the twenty-fifth year, all of them are no longer in business with exception to maybe two companies. Your "decent" speaker stand design that was also defined as child’s play might climb to the level of a boat anchor by our standards. If the speaker resides on our products using a few screws to attach the speaker to the stand will alter its original sonic - guaranteed. The point being "decent" does not survive High-End Audio. Suggestions: 1 There are talented designers that have already surpassed your level of achievement so I would always recommend reaching out to them or gathering information on their products adding to your understanding and level of research. 2 Get the subwoofer off carpeted surfaces and cheap spikes. Hard surfaces will define all that is going on without the absorption of rubber/foam carpet. Place the sub on a neutral grounding plane. Contact some manufacturers to see if they would accommodate you with pricing in order to attain a quality grounding plane for your testing. 3 Concentrate on the sound and forget about the hand touching tests or physically stomping on flooring tests that are totally irrelevant to speaker design and sonic performance. Do not forget as you are adding mass, the product has to be capable of transport and positioning. Good luck with your future in designing and we hope it earns you a living or a place in the industry or self-gratification if that is what you seek. Please feel free to phone us, we will always be happy to answer questions or assist in solving anyone’s audio related issues or just talk sound. Thank you for your time, Robert Star Sound |
By changing the effectiveness of the grounding plane (platform or spikes), the transfer of resonance becomes reality where your book-mentored approach might change as well. Word Salad Vibrations (mechanical, electromechanical or airborne) establish resonance and clogging of the signal pathways establishing component operational inefficiency. Word Salad with Low Cal Ranch Dressing that has been in the fridge too long and gone rancid. |
- 140 posts total