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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
aschuh's avatar
aschuh
42 posts
 
Pasted from wikipedia:
>>>A 12-inch-diameter (300 mm) paper woofer with a peak-to-peak excursion of 0.5 inches at 60 Hz undergoes a maximum acceleration of 92 "g"s.<<<
This is an enormous acceleration, and a membrane with a mass of 8 ounces, accelerated at 92g, can definitely produce enough impact to move even a heavy speaker back and forth.

I agree with the general recommendation to use springs for vibration control, but the issue of vibration control is obviously frequency and component dependent, and there is not one solution for every issue.
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.
The measurement was corrected for room modes, so I am pretty sure what was measured and heard was the isolated effect of the Nobsound springs.
In contrast, when using the springs with a down firing Martin Logan sub, no loss in sound pressure is observed. Obviously the force required to "lift" the entire sub by far outweighs the force required to move a sub horizontally, when it is resting on springs with little horizontal stability.

Hudson silicone half spheres are great for subs.


hshifi
572 posts
 
Hello,
From what I have been told is IsoAcoustics Gaia footers not only prevents unwanted vibration to the room that can effect other cables and electronics of course but also more importantly back to the speakers. Eventually that vibration can travel back like a wave back to the speaker. But we mostly listen in stereo. So we definitely do not want the vibration from the opposite speaker. This can produce unwanted noise or negate the sounds that are intended to be there in the first place. I use spikes that sit on metal discs that sit on the carpet. I can hear the difference between each addition. I am going to try the Gaia footers to see if I get an improvement. I asked my local Hifi store to start carrying them. We will see what happens. Maybe if other people who shop at https://holmaudio.com/
in the Chicagoland area ask for them they will stock them. 
millercarbon's avatar
millercarbon
12,531 posts
 
hshifi, We had someone recently upgrade from Gaia to Townshend Podiums, they are quite a bit better. Do a search you will probably find others. If you want to save money the Nobsound springs are quite a bit cheaper than Gaia (only $30 per set of 4) and probably at least as good, not Podium level but certainly better than anything else for the money.
stringreen's avatar
stringreen
6,487 posts
 
I tried getting my Vandersteens off of their spikes and on to Herbies something or other.  The experiment was a disaster....absolutely ruined the sound after trying to get the very heavy speakers in place.
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.
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