... and so I started hitting things with a stick.

[Pareto Pragmatic]

I've been trying to track down a nasty 300hz problem with my new speaker placement. I did manage to find an issue at 600, but I could not for the life of me see any room issues where 300 would be. So I pulled my surrounds out, set them up in the room's best spot, and shot some measurements.

Still a problem with 300.

And that's when I started hitting things with a stick while pointing a mic at them. And found my wood TV stand (also has an AVR, dac, and fosi v3), has a strong resonance at 300. And I have a very bouncy floor, it's coming from there mostly, but also likely directly from the stand a bit. Before moving speakers, sometimes 300 was more of an issue, sometimes less to the point of not being an issue. Depending, I've tried a lot of different things in the past 2 months.

So I am debating sorbothane. Maybe just putting some under the components, maybe the entire stand (if I can estimate the weight near enough.) Any idea how much of this problem might be coming through the components and how much might be coming from the stand itself?

BTW, https://www.sorbothane.com/technical-data/design-guide-calculators/load-rating-calculator/ is a very handy page for this. Sorbothane seems really good, but it also seems critical to have the right durometer for the weight. I wonder how many people have tried this stuff without making sure they are not under or over weighting the material?

Thanks in advance.

 

[Purité Audio]

Post the room measurements, run a 300Hz tone from REW’s signal generator function, just holding the tv stand would ameliorate the vibration.

Keith

 

[Pareto Pragmatic]

Post the room measurements, run a 300Hz tone from REW’s signal generator function, just holding the tv stand would ameliorate the vibration.

Keith

And that would mean standing by the stand, and sub, which will hold down the floor by the stand. So I don't think that would capture what you think it would. I could add weight to it next time I have the mic out, but I am pretty sure what is going on in this case.

I have taken measures while standing there (between the main speakers), and they are always better. False better, but better.

Just consider my floor a passive subwoofer, that will give you the idea of what I am dealing with. It will turn a 60hz room mode null into a peak as the volume is turned up. That happens around 65db at 12 feet, and there will be a point where it is balance. At 60, null, at 70, big spike.

On the upside, I get 10db higher before the problems start when the weather is nice and I can open up to 10 windows and a door to vent sound to the outside.

 

[Pareto Pragmatic]

Here's a description of how my floor behaves as the volume is turned up (caution, no mic measurements, just volume and feel and hearing) : https://audiosciencereview.com/foru...oom-with-one-number-volume.47955/post-1721758

This is a floor issue that is interacting with the stand, I am as sure as I can be about that.

 

[Pareto Pragmatic]

Hitting things with a stick is a valid measurement technique. And the correct answer to my question is to isolate the stand, not the components.

The TV stand had an effective contact patch with the floor of 5'x1.5' (back and side perimeter + sealed front edge, due to some foam I had used 3 years ago). I had totally forgotten about that foam. So I folded up some towels under the side edges to lift the rest of the contact area above the floor, and pulled the foam.

The inside angles of the tv stand (measured in about 12 places, no hitting with a stick this time) seem to be kicking out 250, 300, and 350 peaks inside the unit. However, it sounded WAY better. So I shot some sweeps.

rt-60 tells one part of the tale:

With the foam:

Yeah, that's what it looked like. Been worse.

Without the foam and lifted?

Hey, look there! I'll take that!

Next part of the tale is 2000hz. This has always been a problem. A big one. So two sweeps, before and after, different days btw:

Given effects low, and high, and the measures inside the tv stand, yeah. The stand is vibrating like all get out. Most likely (now) from the side panels, which still contact the floor.

Sorbothane ordered, I figure $30 is worth a try. I read the shelf life is 3 years so certainly a 2 year use life. On a yearly basis that, if effective, will be well worth it. If not, not much wasted.

 

[my_ori]

Thank you for sharing your experience and findings with us! It's truly appreciated how you've diligently tackled the issue of the 300Hz resonance in your speaker setup. Your creativity in using a stick to identify the problem area is commendable, and it's fascinating to learn about the unexpected source of the resonance in your wood TV stand. Considering options like Sorbothane to address the issue demonstrates your commitment to finding effective solutions. The link you My Boy! APK provided for Sorbothane's load rating calculator will undoubtedly be helpful for others facing similar challenges. Your thorough approach and willingness to share resources are invaluable contributions to our community. Thank you for your insights and for fostering discussion on this topic!

 

[chips666]

PSSY0035125 - PolySound Sylo High End Lautsprecher Füße, Schwingungsd, 8,90 €

Persönlicher Support: ? 0931 – 30699733 für Ihre Fragen rund um: PolySound-Akustik - PSSY0035125 - SYLO - Schwingungsdämpfer - Hear the difference: Die Poly

frankenschaum.de

This could work Succes

 

[ErVikingo]

Glad you found the issue!

At home there was a mid/hi frequency noise which I traced to the A/C return vents.

It is an aluminum one and the slats vibrate. I found the proper position to have good a/c balance and then put glue gun “glue” on the back side of it to fix the slats.

Magic!

 

[Count Arthur]

What does the stand look like? Perhaps you could stick some MLV to the underside of the shelves: https://www.sruinsulation.co.uk/product-list/acoustic-membranes/MLV100-Mass-Loaded-Vinyl-10kg

 

[Pareto Pragmatic]

At home there was a mid/hi frequency noise which I traced to the A/C return vents.

My heating ducts, under the floor, take in energy at 100hz ... until they spit it back, hard!

What does the stand look like? Perhaps you could stick some MLV to the underside of the shelves: https://www.sruinsulation.co.uk/product-list/acoustic-membranes/MLV100-Mass-Loaded-Vinyl-10kg

Almost exactly like this in construction:

Differences? The very bottom front (black in the picture) is open and arched, and there is a bit of a corner brace where that arch meets the sides. Also, mine is only covered in the back in the shelf area behind the center bottom part, the rest is open on the back.

Oh, and ours is a dark wood, not that horrid color. That's not structural, though it is important to me.

I think the side panels are the issue for 300, and if isolating the stand isn't enough, something like you suggest with MLV on the sides might give it the little extra it needs. Good idea for sure.

PSSY0035125 - PolySound Sylo High End Lautsprecher Füße, Schwingungsd, 8,90 €

Persönlicher Support: ? 0931 – 30699733 für Ihre Fragen rund um: PolySound-Akustik - PSSY0035125 - SYLO - Schwingungsdämpfer - Hear the difference: Die Poly

frankenschaum.de

This could work Succes

It might. Reading the (translated) page gave me doubts when I hit this:

"Comparative tests have shown that, for example, subwoofers with PolySound Sylo vibration dampers can be operated louder by 8 dB than without damper, before a roar becomes audible. That's more than double volume!"

 

[Prana Ferox]

Saw the thread title and just assumed this was the origin story of some famous drummer

 

[Anton D]

If you own your place, consider going under the hoist and bracing the floor with supports.

Floor support jacks are cheap and can mitigate your bounce!

It's readily Google-able.

Best wishes.

 

[antcollinet]

I had a turntable on a pine chest of drawers. It resonated the bass horribly.

My solution. A chunk of oak door. (basically a piece of oak about 2 inches thick, and large enough to cover the top of the chest. I was lucky enough to have some old doors lying around. You could use any solid heavy material though.

I put sound damping material intended for cars between it and the chest, and between it and the turntable. (See link)

Problem solved


Damping material on Amazon

 

[Pareto Pragmatic]

If you own your place, consider going under the hoist and bracing the floor with supports.

Floor support jacks are cheap and can mitigate your bounce!

It's readily Google-able.

Best wishes.

Good suggestion! Yep, that would work well. A few years ago I put a post and a beam across 3 joists, at the lowest point of the sag/MLP. Before that, it was really bad. It cut down on the amplitude for sure.

The problem with doing more is that moving the floor up at all risks cracking 100 year old plaster, and buckling the engineered wood floor currently installed, given the degree of sag. Doing the job actually right would also likely mean replacing two original central posts, since it won't take much to lift off of those after 100 years of compression.

I've thought about it, more than once. I might get there, jacks and little pressure so minimal lift. We'll see how this change goes first once everything shows up at the door, eqs get set, and I live with it for a few weeks.

 

[my_ori]

Thank you for sharing your experience and findings with us! It's truly the appreciated how you've diligently tackled the issue of the 300Hz resonance in your speaker setup. Your creativity in the using a stick to identify the problem area is the commendable, and it's fascinating to learn about the unexpected source of the resonance in your wood TV stand. Considering options like Sorbothane to address the issue demonstrates your commitment to finding effective solutions. The link you My Boy! for PC provided for Sorbothane's load rating calculator will undoubtedly be helpful for others facing similar challenges. Your thorough approach and willingness to share resources are invaluable contributions to our community. Thank you for your insights and for fostering discussion on this topic!

 

[Pareto Pragmatic]

Ok, first my "review" of sorbothane.

It works well on vibrations, not so much for my bouncing floor. I think it is good, and worth the small amount I paid for some marginal improvements. Mostly improvements were 1-3db in level. Similar for car soundproofing sheets on the bottom of the shelves. Other than at 600, where the tv unit shelves were going crazy. (I did consider MLV, and will for future projects if needed, but I was trying to keep the time and cost down on this.)

Placing a board or something on top of 4 sorbothane discs as I did with my sub, easy. But they do slowly sag as they settle in, so after a few minutes I checked and had to lift the front of the sub, which is heavier, a bit.

Making individual feet? On a very not level floor to put heavy furniture on? Pain in the butt. But it can be done. I used a furniture slider (foam to floor) then sorbothane, then a hockey puck.

Oh, and the package weight specs were not the same as the sorbothane calculator. I suggest using the calculator numbers if you want to try sorbothane out.

So, measurements at 12.5 feet from speakers, speakers are modified Heresy 1s, undamped and no bracing (lots of cabinet resonances) placed as almost pure corner horns, crossed in front of the listening position. Zero degree mike, so some compression for the highs. The stuff at 10k is at least partially laptop noise.

If I get things close to +/-5db I generally call it a day with the Heresies.

Topping e30 ii into fosi v3 into the heresies.

No sub, no eq applied.

For the room, just assume that the measurement position is 1 meter from a 9.5' tall and 13' wide and deep horn... you won't be wrong.

Full range, previous was 80-5000.


Blue/light line is center seating position, as in the previous measurements. Black/dark is the RMS average of measures taken at the left, center, and right seat.

I went looking for the 300 problem, poking my mic here and there. Best guess, based on the fact that it did not show up strongly before moving my speakers to the corners, something is going on between the corner and back of the speaker (which is why I now get a spike at 300 with other speakers in the room, that's my guess). I did see some improvement at 300, but barely.

But for some reason I decided to do a quick "current" capture sequence across the front of my couch into RTA. The result of that led me to do a more formal measurement, the black line.

I think I have done all I can, in terms of what I am willing to do, other than maybe a touch of EQ next time I measure. Attacking any one problem generally leads to others getting worse, but across the 6 foot couch the sound is good for all positions. Better for left and right than center in many ways. And since my wife's seat has more bass, mine has a bit better midrange for my tastes and less bass bump, I think this set up is about perfect for us. For very flawed speakers.

Given that I am getting new stand mounts in a month or so (Sierra LX), I won't be going to this for living room music very often any more. But I will on occasion, so, nice to have done what I can on these.

Thanks for the help and options!

PS. The heresies will not be further modified. I think the cabinet resonances and the recessed tweeter give them their unique sound, and since I had to promise my wife that I "would not change the sound" of the heresies for every previous modification...