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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.
linnvolk
pch300
56 posts
 
@linnvolk, I think you have asked some very good questions and proposed some workable approaches. I have used "spikes" under my floor-standing speakers. In my opinion, the sound was better after the spikes were used than before, particularly in the bass region. I think it cleared up the rest of the audio band too, but can't be sure, without further study. Because the spike may not have been as good a coupler as I assumed, or the isolation is not a full isolation as I assumed, is why I can't be sure, without further work.

I'd suggest that we step through the vibrational chain, every step from speaker motor to the entire cabinet, and to the floor. Let's assume a conical dynamic speaker, mounted inside a cabinet that is sitting on the floor, for the purposes of discussion. The cone can be assumed to move fore and aft, as well as up and down, to cover at least the two most common arrangements - front firing, and bottom firing speakers..

The speaker motor (voice coil) moves the diaphragm.
1. What motions get transmitted to the basket?
2. Then, what motions get transmitted by the basket to the cabinet, when attached?
3. What motions are excited by the air volume inside the cabinet?
4.Then, what motions get transmitted to the speaker base (carpet, no-carpet, spikes,...)?

I've heard that some propose that the driver should be isolated from the cabinet.
I've also heard that the cabinet should be as massive and rigid as possible.
I've heard that coupling the speaker to the floor is an improvement, and also the opposite suggestion of isolating the speaker from the floor.  

If we can get answers to 1 through 4, I think we will have a better idea of where the biggest problem lies. Sounds like several of the posters have tried many things already. One of these days, I may get around to really think through this problem.
ausaudio
90 posts
 
aschuh

Specifically, I measured a 12" Rhythmik sub, front firing, at minus 3 - 4 dB, when sitting on Nobsound springs (compared to standard hard rubber footers), which obviously allow for horizontal movement.
The loss in bass energy was quite audible.

I do not think this is physically possible. Estimating the speaker weighs 50lbs and the cone and voice coil 8 ounces, the speaker cabinet would move 1/100th as far as the cone, for an equal and opposite reaction, assuming 100% of the energy moves the speaker. The cabinet is larger in surface area, but 3db is a 50% loss in acoustic power. This is not possible.

pesky_wabbit's avatar
pesky_wabbit
1,183 posts
 
I’ll second Townshend podiums. They are awesome if you have deeper pockets than me. A game changer I hope to own one day (soon preferably).
mijostyn's avatar
mijostyn
8,570 posts
 
linnvolk, That is correct. Spikes lock the speaker to the floor. It is the speaker resonating that you are worried about. Play something with a loud bass line and put your hand on the speaker. That vibration you feel is the speaker resonating. Locking the speaker to a solid floor minimizes some of this but not all. Any vibration you feel is distortion. It is usually low down so it is the woofers causing the problem. Because the forces on the speaker are rarely symmetrical the speaker can slowly walk across the floor. I have seen this happen on both wood and carpeted floors. Spikes prevent this. 

Some people think that isolating the speaker on springs helps to keep the floor from resonating. This is another example of lay intuition run amuck.
The speaker just resonates worse and the floor keeps resonating just the same. If you want to keep the floor from resonating put the speaker outside. Heavy carpet will dampen it to a degree. 
linnvolk OP
90 posts
 
@mijostyn, I wonder if what you are feeling with hand on speaker is primarily flexible modes being excited, which locking the speaker to the floor will not really attenuate.

Spiking the speaker to the floor (if it actually works as intended) would restrict the translational fore-aft rigid body mode, but it would do little about the fore-aft rocking mode. I suspect both of these modes for most speakers are in the sub-1-Hz range. I am skeptical that any true acoustic benefit of spikes derives from them actually anchoring the speaker to the floor, though their ability to keep the speakers from walking might be valuable.

Have you done the "hand on speaker" test both with and without spikes (same music, same electronics, same everything, except with/without spikes)? I have not, but my intuition tells me that you may feel no difference(?) I would put the same question to the "spring and damper" crowd.

Based on anecdotal evidence from others and the differences in opinion regarding the physics involved from experts (Richard Vandersteen and others), I suspect that:

  1. There may be some real difference (better or worse) in SQ between the manifold options (including doing nothing).
  2. It is difficult to know whose grip on the physics (if any) is correct.
  3. It is difficult for me to entirely reject that perceptions based on bias will unavoidably be mixed with perceptions based on true acoustic reality--and I mean *anyone’s* perceptions. The ability to conduct a true blind A/B/C/etc. comparison between options, realistically for real humans, is limited at best, especially for heavy floorstanding speakers.
  4. The truth regarding the physics is, and likely will remain, both complex (much more than "gotta keep the speaker from moving" or "gotta let the speaker move") and elusive.
  5. Experimentation with one’s own ears (but see Item #3) and equipment would be the most profitable path forward, to the extent one wishes to invest in the experiments. Personally, I have way too many other interests, including a soon-to-be-seven-year-old, to invest much more in this particular enterprise--at least until my new system is set up and I start itching to mess with it all.
  6. For tower speakers on thick carpet, spiking through the carpet it to whatever floor is underneath may be a good idea for stability against toppling.
As Einstein said, “It can scarcely be denied that the supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience.” (often misquoted)

Thanks again for all the input.


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