spikes under a subwoofer ?

I recently purchased a Velodyne HGS-18 Series 2. Although mates very well with my main speakers, I've read that adding spikes generally providers deeper bass response as well as greater clearity. Does anyone else have any suggestions as to what I could place under the subwoofer that would pierce carpet.
nine inch nails. -cfb
2001impala, I also use a Velodyne sub. I installed four PolyCrystal speaker spikes in place of the rubber feet. WOW what an improvement! I think any brand of good quality spike would work well. (If anyones interested I have 6 used PolyCrystal speaker spikes left that I would let go very inexpensively. Email me if your interested). There are also other posts on file regarding the same question. Good luck.
I use the spikes on my REL Storm III
CFB, I have to say you've been in rare form this week:~)

And now back to the subject matter at hand. I own the Velodyne HGS 15 and use to have it sitting on my carpet. I know what your thinking. Energy is escaping through the bottom of your speaker. It was recommended to me to use spikes and load some weight atop the speaker. About the time I was shopping for spikes I remembered having an amp stand in the closet. That's when the light came on! (The closet light). I set the sub on top of the amp stand raising it off the carpet. IT WORKED! I have not loaded any weight yet but will experiment with that this year.
You may want to decouple the sub from the floor,and get
an even better result! Most people believe in old truth,
without understanding too much about this complex matters.
Vibration control is indeed a complex subject, but according to an inverstigation made here in Sweden, spikes often endsup with an inferior result, because when you couple the sub to the floor,AND the floor is prone to resonate!These are unwanted contributions to the sound that you want! There are decoupling devices that prevent this from happening(altough having a soft carpet to place the sub on makes the whole thing more complicated).

For my part, using soft non-elastic feets called the"SD-fot"
that are made in different"densities", for loudspeakers or subs with a specific weight, and which makes it almost impossible for the transducer, to feed the vibrations to the floor,has in my opinion cleared up the bass as well as the the other registers.
This metod has been accepted here in Sweden, even among the
rather conservative magazines. One test one of them made,
was simply to place a coin on end at the top of the loudspeaker, while playing some bass-notes;without the SD-feet, the coin fell, with the SD-feet it stood up.
This decoupling tecnique was accepted several years ago,
when it came to tone-arms an pick-ups(warped records).
Time to rethink some loudspeaker-truths maybe?One italian reviewer of these devices, clearly misunderstood the fact that with the damping feet under a loudspeakers, you can swing them a bit
back and forth, by hand;it might feel as it they are a bit unstable,BUT that is intentional! That resonance is to low in frequency(say 8Hz) to be engaged by the woofer.The loudspeakers enclosures will stand more still with the soft feet Not too uncommon with less educated reviewers
and conclusions that are wrong,eh?

I feel that I may get a lot of opposition, for writing negatively about the "holy" spikes.But please try to be open-minded, there may be another truth!
I realize you are talking about a Velodyne, not a REL, but my experience with my REL is as follows:

Sumiko advised me AGAINST using spikes under the REL because it would change the distance that the sub "sees" from the bottom of the cabinet to the floor. I don't know about the Velodyne, but with the REL, since the spikes would be screwed into the existing feet, this would obviously be the case.

On Sumiko's advise, I bought a one inch thick slab of sandstone about four or five inches larger around than the sub, and placed the sub on it. The improvement was immediately obvious: much tighter and seemingly slightly more extended lower response. The somewhat rubbery sound (compared to my main's speakers') was reduced and integration was improved. The weight of the sandstone (considerable) apparently does a good job of coupling the sub through my carpeting to the floor.

Good luck.
We have found the same problem Dinos describes above. We have found that spikes into a wood floor; even through carpet does indeed mess up the midrange etc. We have found that something simple and cheap under even stock spikes make a huge difference in the overall sound. Yes even coins placed under the spikes help. This is not as big of a deal when speakers were on concrete slab floors.
I think that you're going to get BIG differences if the floor is suspended or not when using spikes. Directly coupling it to a suspended floor with spikes can REALLY excite the floor, especially when we are talking about a downloaded subwoofer. As mentioned, driver to floor distance can also affect the loading characteristics of said speaker too.

One trick that you can use is to spike the speaker cabinet and then place that on top of a board or large flat surface. The surface should be slightly larger than the cabinet. The panel lies directly on top of the carpet, which spreads the load out on the floor somewhat. This rigidly couples the cabinet to the board while the board is somewhat isolated from the floor by the carpet and padding. You still get the correct loading for proper driver output due to the panels' flat and smooth surface AND minimize floor excitation due to the slight carpet / pad insulating effect. Playing with the type of and mass of the panel and adding weight via mass loading can be used to "fine tune" the results somewhat. I've found that adding too much weight to the cabinet will tend to deaden the bass and make it slower though, so be careful. Just a thought... Sean
Perhaps I should add that the HGS series subs are front firing.
Good point : )

The effects mentioned above should still be similar but possibly not quite as drastic. Sean
Have a look at this page: www.sonicdesign.se/sdfeet.html
Quite interesting, and to my knowledge, you can excite
resonances in the floor even if it´s made of concrete!
I have tested the SD-feet just in this case,(and at different places) and the improvment in sound quality was remarkable!
The Danish loudspeaker, CDP and amplifier- company Holfi is marketing simular soft feet, they also claim that floor and loudspeaker cabinet vibration is significantly lower with their softfeet(some thousand times lower vibrations, if I remember correct).
Of course,I have no commercial interest in either of these
You have to weight the front- and back-side of your loudspeaker or sub, to get the right stiffness in the feets.I think there are feets up to a load of about 450 Lb. They are made of a material that doesn´t have closed cells,therefore the feet wouldn´t collapse with time.
I can´t say what the prices for the SD-feet are at the moment(set of eight of them),but I believe that you should
be able to get a set at about $130 including shipment
to the US.

No one right answer. You sue the method that reduces the cabinet movement, simply put. THAT depends on the floor. For instance, my C4's with spikes firmly into the concrete floor simply blow away the speakers sitting on the carpet. ANY movement kills higher frequency doopler distortion, too, as the tweeter moves so little relative to a big old speaker rocking around. For my floor, the spikes rule!

I have DD10+ subs that sit right on the floor (odd) and I'm still wondering about that. Sure, bass is a LONG wavelength from a sub, so technically it is less easy to hear the doopler movement and yes, bass has a lot of distortion recorded-in, or produced by the driver. But, the C4's low-end resolution improved substantially with spikes into a concrete (not wobbly OSB subfloor)floor.

I do, and don't, buy that subs need to be on the floor with modern digital EQ. And, in my case, the room is 40 feet long so I have TOO much below 30 Hz! So again, it's the "system" that matters. Fix yours and don't just be someone else's stereo in your different sounding house.
I think what you need are the Auralex SubDude HD Isolation Riser (the HD means it's dressed up a bit for home use v. the regular SubDude). Widely used in homes and pro studios. These are foam type supports to use under subs (there are speaker and desk versions also). The things really work!

Kal Rubinson did a review in Stereophile in about 2005 or 2006, and it was basically a rave review. Absorbed vibrations, the house and bookshelves no longer vibrated, and the sound was improved considerably.

They're for sale on various sites (Audio Advisor, Music Direct), where you can also read numerous user reviews, which are something like 98% very positive, even raves. Cost is about $60 for the sub version.

In the case of the sub dude,if you want to take it to a higher level...a must have is the sub-trap made by ASC. I've been using one for years and it comes highly recommended...

One of the oldest threads I have seen come alive! However, I have two JL Audio F113's and my floor is carpet on wood with underfloor. The Auralex works great and greatly reduces the unwanted frequencies that were caused by the sub coupled to the floor which transferred into walls furniture etc... I highly recommend raising and decoupling a sub off this type of floor.
I cut 2 yoga foam blocks to make 4 smaller blocks and put them under the sub. It was too boomy sitting directly on the floor.
Sorry I can't be more technical than that.