# 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:

1. 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.
2. 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.)
3. 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).
4. 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."
5. 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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 @linnvolk - I agree - accelerometer data would be quite informative.However, when a front-firing 100 lbs subwoofer is resting on springs with limited horizontal stability (because they are not guided by a shaft or control arms), you are not looking at a "rigid-body mode". The woofer motor accelerates the membrane forward, and - assuming above numbers - generates a backward counter-impulse equal to a weight of 46 pounds (that's roughly equal to a force of 200 N - substantial). This definitely suffices to move the entire sub backwards when it is not fixated and can move horizontally. The effect is - as stated - very audible and can be measured in terms of reduced SPL. For any service arrangements, please negotiate with @ausaudio directly :-) V. Interesting analysis regarding spikes and decoupling from ATC's head of design https://www.facebook.com/watch/?v=4132108963488462 Linnvolk, you are absolutely right. I shortened the explanation by saying,"minimizes some but not all of this." The speaker resonating in any way is distortion. Ideally you should be able to feel no vibration at all anywhere you put your hand on the enclosure except the driver. I build my own subwoofers, the design I am currently using focuses on high mass keeping the bulk of the mass behind the driver. They have rectangular enclosures 14"X16"X30" with the driver located in the end. They are made out of solid surface material and MDF. Each enclosure weights 200 lb without the driver a very massive 12" Dayton. Testing with an accelerometer indicated two modes of vibration back and forth along the main axis and expanding and contracting. Without the spikes the drivers also walked backwards on carpet. I think they went backwards because the rear bottom edge is radiused and the front edge which originally accommodated a grill is sharp and catches the carpet. Installing spikes obviously stopped the walking and almost entirely stopped the axial vibration and did nothing for the expanding/contacting resonance. Although these subs sound better than any other subwoofer I have used I consider them a failure and am in the process of building a new set. The new set uses a cylindrical enclosures with 12" drivers in both ends operating in phase. The walls average 1 7/16" thick. The forces from the drivers should cancel out and a cylinder is much stiffer than a rectangular cube. We shall see if this works, hopefully by the end of the Summer after I finish my wife's Kitchen.
•  140 posts total