My 2024 Polk SDA 2b Modification Progress Thread (Drop1)

Spike your subwoofer to the top of one of your SDA 2B and crank up "Bass & Drum Intro" by Nils Lofgren Band and see it they commence to rockin' 🤣

But seriously, you have things in your favor: Inertia of your speakers, Low Q (high damping factor) of those rubber footers, wider footprint with your outriggers, drivers are not an extremely large moment arm from the floor, Your push by hand is a very large force relative to real world impulse reaction forces when playing actual music, etc..

If you give a little impulse to the top with your hand what do you estimate the resonant frequency for rocking motion to be?

What kind of hardwood floor is it.......hardwood over a slab or hardwood over suspended floor/ceiling?

I think at this point the true test will have to be switching between coupling with spikes and the rubber Tough Nut Cone footers. Listen to how clear the midrange is in each case as well as how impactful kick drums are and decide. If the midrange is really sweet with the Tough Nuts relative to the spikes and if you have the speakers fairly close to the wall, experiment with a square steel tubing between the two a la the Matthew Polk Bass Brace.

skipshot12 wrote: »

Can one use spikes with cups underneath on hardwood?

I did in my living room before I built a dedicated audio room, they work okay but not as well as spikes direct to floor.

Really good live test of various speaker decoupling devices. If I remember correctly the Townshends won. You could push on the speaker with the Townshends and it will rock back and forth as well. They have springs which, if there was nothing else, would be close to zero damping but they add a rubber bellows with an ori fice through which air can escape at a controlled rate, providing damping. They were not hurting the bass response at all.

https://www.youtube.com/watch?v=5cXRYay0Mbc

That's a long video but for anyone who wants a quick comparison between the same song on the Towshend Isolators (35:22) vs. Spikes (49:48) just give a listen. Difference is in no way subtle. One way is the clear winner for me and the other stressful to listen to.

https://www.youtube.com/watch?v=5cXRYay0Mbc

drop1 wrote: »

@Gardenstater thank you. That's helpful. I won't wax philosophically about how I think about coupling/de-coupling but like I said, the website notates the 'flex' as a feature of the product. And come to think of it, I've encountered a number of stereo-heads that swear by these cheap-o springs from Amazon.

I will listen and let my ears decide.

As a point of clarification, 'final' application will be on a hardwood floor. But that project has been put-off for even longer than the duration of this project. Does 1,400 ft^2 of hardwood flooring count as a hi-fi upgrade (w/ rug)? Trends are pointing toward converting listening rooms back into living rooms (it's part of the comfort/enjoyment factor). Audio enjoyment transcends just stereo electronics/equipment nowadays. Cleaning your ears, proper sleep, mental stability: All for the purpose of maximum enjoyment from your favorite albums.

My living room remains to be old shag carpet. I was hoping floors would be down by project completion but now I have mid-term house-mates. I'm close to snapping pics of the final project results. Maybe I'll even bust out the old swag-lamp that came with the house (it is period-correct). I'll replace the cones with basic spikes for now and experiment later.

Here's an idea that would allow you to go forward with listening tests despite the shag (Avocado? 🤣) carpeting that may take who knows how long to make it's exit. If you get 2 of these 24in. x 24in. x 2 in. concrete pavers and if you can find 4 carpet spikes with removable studs, you could through drill the concrete pavers at each of the 4 corners and have a length of threaded rod going into the carpet spikes underneath and a nut and washer up top. You could also drill them out large enough so you could epoxy in threaded inserts but that is kind of a PIA to say the least.

Then you would have a stable platform to proceed with spikes vs. Tough Nut Cone comparisons and any others you want to try.

You could also go with 3/4 in. hardwood plywood (or thicker butcher block). I just prefer the concrete for stability and mass. Hardened steel Bolts (like Grade 8 or higher) could be used for the spikes from the outriggers to your concrete blocks if you don't mind grinding points on them. That's what I did with my subwoofer. Then maybe you could use your nice spikes against the carpet without dulling the points. Then of course if you don't mind the height difference or the questioning of what part the intermediate platform plays, you could just test the spikes as you currently have them.

F1nut wrote: »

In my experience anything other than the speakers spiked to a solid floor just doesn't cut it.

I have found that to be the case with SDA speakers.

You're making great progress. Here's another YT video about the Tough Nuts that you might find reassuring. I don't agree with the way he tried to measure it though; using frequency response. You really have to measure in the time domain to get an idea of what your ear is hearing as beneficial or negative. It was interesting though that he did measure differences in the frequency response though, for sure. The spikes were too bright and benefitted from putting felts between them and his hardwood floor (somewhat similar situation to your spikes with carpet) and the Tough Nuts sounded worse with felt. The sound was more relaxed and natural and pleasant to hear with the Tough Nuts. I think he tested the Tough Nut Cylinders because he was afraid of the cones stability-wise but then regretted not insisting on the cones.

https://www.youtube.com/watch?v=LAPOOqCvGsk

Not gonna lie I kind of dig the orange

VR3 wrote: »

Looks great now you just need diffraction control for that wide baffle

Wink wink...
I think I do too. My 2B have pretty much every recommended upgrade except your pads.