Amp Riser Effectiveness

#31

Soundman2020 wrote:
endorka wrote:Cheers Stuart. It's just the camera angle, the riser is about a foot away from the rear wall.

Are you sure? It doesn't look like a foot...

Aha, I see the confusion :-)

Fortunately that's a side wall, and it's the bottom of a bass trap angled at 45 degrees from the wall. The riser is a couple of inches away from it. The rear wall is the one with the visible wooden skirting behind the kit. There's usually some bass traps there too, but I moved them out the way for the rehearsal.

That testing machine is impressive, but like you I suspect these cost a small fortune. No fears, I have a contraption in mind to serve in its stead :-)

Cheers,
Jennifer

#32

At last the modular riser is finished!

Here's the 8x6 foot version;

Close up detail of the trim and joining bolts;

As per design the sections can be combined in various combinations to make;
- two 6x4s
- one 6x4, one 4x4 and one 2x4
- one 6x6 and one 2x6

And various other combinations.

The top layer is joined by the cam bolts commonly found on flat pack furniture so assembly and disassembly is easy. The other two layers are joined by 170 x 7mm steel rods in a way that all three layers are connected on most combinations. The joins are very secure, you can walk across the riser no problem at all. Here's a photo of a test fit showing the connections between the three layers;

The modular design is useful for the different recording situations I do with various instruments in the two rooms, and being able split it apart will be essential for some of the studio modifications to come. Saying that, the design and build was an order of magnitude more complex than simply building a single 8x6 foot riser. The many bolt holes had to be drilled to millimeter accuracy, and holes in the trim drilled accordingly. It was worth it, but if you can get away with building the single large version, I'd seriously recommend doing so :-)

Cheers,
Jennifer

#33

The reduction in impact noise to the rooms below and adjacent has to be heard to be believed, it is truly incredible. I'll do some sort of test soon.

In the meantime, the following might be of interest. It's a comparison of the transmission loss to a room below of a bass amp on the 6x6 foot version of the riser versus directly on the floor. Done using REW through the amp. Measurement mic in the room below. The amp was calibrated so that unfiltered pink noise was 105dB at a distance of 1 metre from the amp, C weighted, slow.

Cheers,
Jennifer

#34

Lovely work! Definitely good in your situation to have modular! I think if I need one I’ll do it in one : )

#35

endorka wrote:Source of the post At last the modular riser is finished!

Wow! I'm impressed. That looks very, very nice. Jennifer. Quality workmanship, and I love the way it's all modular, so you can re-arrange things and even split off sections for separate risers. Very smart.

You should patent the idea!

- Stuart -

#36

endorka wrote:Source of the post The reduction in impact noise to the rooms below and adjacent has to be heard to be believed, it is truly incredible. In the meantime, the following might be of interest...

It sure is. Once again: impressive. It looks like you are getting around 10 to 15 dB improvement across the entire mid range, and even a few dB down in the very low end. Very decent.

I'm really glad it is working so well for you so well, after all that work!

- Stuart -

#37

Thanks Stuart. Indeed, such a relief that it works so well after all that work and additional expense over building it as one. I can't remember if I've mentioned this before but the design is very similar to one in Rod Gervais' book that he mentions using to cover an entire floor. The benefits are clear - I was hoping for a reduction in impact noise to rooms below, which it has delivered incredibly well. That it also reduces impact noise to adjacent rooms is a welcome bonus, as is the reduced transmission of non impact noise to rooms below. There is no reduction of non impact noise to adjacent rooms, but this was neither sought nor expected.

And thank you Tom, yes definitely the "all in one" solution is the path of sanity :-)

Saying that, all the hard work is now in the distant past and I'm enjoying the modular benefits already. I've just used the 6x6' version for drums in a full band recording. Plenty of room for the bass player to go alongside. The 4x2 riser was in the other room for the guitar amp. Worked a treat.

Cheers,
Jennifer

#38

Here are the test results for non impact sound transmission from room 1 to room 2 (adjacent via the landing) with an REW sweep with the amp on and of the riser. Same test setup as previous post;

My untrained interpretation is "no significant difference" between on the riser and off. The small variations in the peaks and nulls makes me wish I'd made several sets of measurements with the amp and microphone in a variety of positions to obtain better average graphs.

Cheers,
Jennifer

#39

Wow! This is amazing!

Hey everyone! Just signed up to this forum and I'm already in love haha. This rise concept is exactly what I was looking to do in my studio build. I'm building on a 2nd floor over my garage and was thinking of doing this for the entire floor but after seeing this modular approach I must say I'm rethinking.

Great job!! Cheers!

#40

Glad you found it useful :-)

The modular approach has definitely proven its value, at the moment I have it as two 6x4' risers, one in each room. Saying that, it would probably be quicker to apply it over the entire floor than build the modular version!

Cheers,
Jennifer

#41

endorka wrote:Source of the post My untrained interpretation is "no significant difference" between on the riser and off.

There's some differences, but as you say, not all that significant. But you say you can definitely hear the difference, subjectively, and it is very noticeable? That implies two things: 1) the original tests might not have been valid, or done with the mic and speaker in different locations. 2) There is still significant "bleed" through other paths, different from the floor. Probably airborne transmission. The floor isolation from the riser would mainly affect structure-borne isolation: the riser won't accomplish much for air-borne.

- Stuart -

#42

Soundman2020 wrote:Source of the postThere's some differences, but as you say, not all that significant. But you say you can definitely hear the difference, subjectively, and it is very noticeable? That implies two things: 1) the original tests might not have been valid, or done with the mic ans speaker in different locations. 2) There is still significant "bleed" through other paths, different from the floor. Probably airborne transmission. The floor isolation from the riser would mainly affect structure-borne isolation: the riser won't accomplish much for air-borne.

Apologies, I think my graph labels could have been clearer - that particular measurement pertains only to the room across from the room with the amp in it. I don't hear any significant difference in airborne sound from that test either, and didn't expect any - just did the test for thoroughness :-)

I did the on and off riser tests in the same session with good measurements so have confidence in the test method. Edit: Although I controlled for position of the amp in terms of length and width in the room, it was ~10cm higher when on the riser than when on the floor. It might account for some small difference.

There was some worthwhile attenuation from the amp to the room below though, see post 33 and this graph;

There is a huge & hilarious difference in impact sound when on and off the riser to rooms both below and across though. Only ear tests done for that at the moment, alas, as the difference is obvious, and more importantly, sufficient. I really should figure out some Heath Robinson type device to test this objectively and repeatably though :-)

Edit for further clarity as I have several threads going at the same time: I have noted significant differences in airborne transmission to rooms across from and below the main studio room, room 1, but these are from the improvements made in my other thread. Putty pads on electrical outlets, caulking around perimeters and so on. There are independent tests measuring these improvements over there.

Cheers,
Jennifer

#43

It's great to see the continuing, ongoing improvements in your place, Jennifer! Everything you are doing seems to bring you noticeable, verifiable, and useful results!

I'm really glad that it is all working out.... and looking forward to seeing what your next plan of attack will be!

- Stuart -

#44

coolio, that design gets around. i had put it together for a friend whos daughter wanted drum lessons and the basement room was about 1m from the neighbors... so between the riser and a window plug, it was tolerable for the neighbor

the glue and screws are really about forming a single mass, the main action is the spring formed by insulation wrt the mass of the platform and loading. for a small instrument pad, i'd be more inclined to use rebonded carpet foam or solymer pads etc to accurate map the spring action. or the lighter semi-rigid (3lb/ft3) vs 5lb/ft3.
and of course most powered speakers don't have a lot of cabinet vibration which is why you only see a small decrease on the structural effects - but in a quiet place every bit helps. most amps would then benefit from a gobo placed in front (also decoupled form the floor) to cut some of the air transfer to the structure and also help balance the room.
one thing also - mic stand isolation from floors and cabinets + damping. even if the mic has its own decoupler, the stand shaking can result in an audible variation (however small) - so small speaker stand decoupler pads are a useful tool, plus extra weights (sand bags for example) to increase the weight on the pads + dampen around the base.

#45

Thanks for all that extra information Glenn. These risers have proven enduringly useful, demonstrated by sessions today & yesterday recording a 5 piece jazz band all at once. My wife was able to watch television in the living room two floors below when this was going on without being disturbed. Even when the drummer was really going for it with sticks. She reckoned a lively conversation would have been fine too, but work would have been a bit tricky. Not because of the volume of sound, but because of repetitive "earworms" from many repeated takes of short sections that tend to stick in the ear and become difficult to ignore.

Context is important here, because before the riser even with a silent rehearsal using an electric drum kit, the thump of the kick drum was too much in the living to watch television. The riser has made a huge difference.

Speaking of isolation of mics from instruments, here's a variation on that theme from those sessions. Kick drum mic on the floor, kick drum on the riser. The drum kit overheads are attached to a stand coming from the ceiling, so they are also decoupled.

Cheers,
Jennifer

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