Can a Room 'Leak' Bass?

Nyal Mellor said:

Why is sub 20Hz interesting? IMO the key area for bass / LFE in movies is 30-70Hz.

Click to expand...

30-70Hz isn't a problem. Both my small tv-room surround setup and my livingroom stereo bass modules manages that to ref and beyond (tvroom is limited due to front speakers earlier than that, though). I think you may have to refresh your information a bit, there are quite a few movies with MUCH deeper tracks than that, and more coming out. Gary Rydstrom is one man to look for soundwise.

Here's one scene that I don't get the full experience of in the tv system, the 50 caliber scene from Hurt Locker


And here's the scene that got me in "trouble" with the neighbours which is the reason why I will have to take the ceiling and walls in the theater down and rebuild them from almost scratch:

As you can see, quite some output down to 5Hz. (War of the Worlds, it ought to be the alien walker rising through the ground in this graph)

And here's something even harder to play - from How to train your dragon:


Had I not wanted to play this, I would have gone for two bass-reflex speakers with the same elements rather than six sealed ones combined till infrasonic boost plug-in card to my crossover.

And this is just movies, there's quite a lot of music containing sub-20Hz information too. The guys on my swedish hifi-forum have compiles a playlist on spotify for sub-20Hz music and it's not so short anymore.

Nightlord said:

30-70Hz isn't a problem. Both my small tv-room surround setup and my livingroom stereo bass modules manages that to ref and beyond (tvroom is limited due to front speakers earlier than that, though). I think you may have to refresh your information a bit, there are quite a few movies with MUCH deeper tracks than that, and more coming out. Gary Rydstrom is one man to look for soundwise.

Here's one scene that I don't get the full experience of in the tv system, the 50 caliber scene from Hurt Locker

And here's the scene that got me in "trouble" with the neighbours which is the reason why I will have to take the ceiling and walls in the theater down and rebuild them from almost scratch:

As you can see, quite some output down to 5Hz. (War of the Worlds, it ought to be the alien walker rising through the ground in this graph)

And here's something even harder to play - from How to train your dragon:

Had I not wanted to play this, I would have gone for two bass-reflex speakers with the same elements rather than six sealed ones combined till infrasonic boost plug-in card to my crossover.

And this is just movies, there's quite a lot of music containing sub-20Hz information too. The guys on my swedish hifi-forum have compiles a playlist on spotify for sub-20Hz music and it's not so short anymore.

Click to expand...

Well I stand corrected. Nice data there

Honestly good luck trying to contain frequencies that low short of building yourself a room within a room on a concrete pad isolated from the rest of the building! And even if you do that there will still be some rumble audible outside the shell of your room within a room...

Are you sure it's these ultra low frequencies causing the issues with your neighbors?

Nyal Mellor said:

Well I stand corrected. Nice data there

Honestly good luck trying to contain frequencies that low short of building yourself a room within a room on a concrete pad isolated from the rest of the building! And even if you do that there will still be some rumble audible outside the shell of your room within a room...

Are you sure it's these ultra low frequencies causing the issues with your neighbors?

Click to expand...

Thanks.

Well, now that I found the issue, I may very well consider doing just that. I just have to hang on or a few months to verify my wife's work situation - I rather have a less than optimal working cinema than a torn down room with financil issues to rebuilding it.

Not sure, I got the phonecall after playing war of the worlds loud and pssibly with boosted bass too. I haven't been within 10dB of that level when I've taken measurements later. It definitely leaks up towards 250 on a diminishing scale and above 1kHz I couldn't get any reading at all. But as I expect the lowest to be the most problematic for dual reasons... both the dampening problems and the need to boost them quite a bit for 'audibility'. My electronic crossover do have an optional subsonic cutoff filter that can be activated for late nights if needed, but the hope would be to build so that I don't have to compromise.

Nightlord said:

Thanks.

Well, now that I found the issue, I may very well consider doing just that. I just have to hang on or a few months to verify my wife's work situation - I rather have a less than optimal working cinema than a torn down room with financil issues to rebuilding it.

Not sure, I got the phonecall after playing war of the worlds loud and pssibly with boosted bass too. I haven't been within 10dB of that level when I've taken measurements later. It definitely leaks up towards 250 on a diminishing scale and above 1kHz I couldn't get any reading at all. But as I expect the lowest to be the most problematic for dual reasons... both the dampening problems and the need to boost them quite a bit for 'audibility'. My electronic crossover do have an optional subsonic cutoff filter that can be activated for late nights if needed, but the hope would be to build so that I don't have to compromise.

Click to expand...

How did you build your walls and ceiling now? Any windows?

You can test isolation by playing something like periodic pink noise inside the theater and then measuring outside with a real time analyzer (if you didn't already). That will give you some good data to go on in terms of which frequency bands are most problematic.

Where is the room -- basement, on concrete floor, or higher in the house?

My media room has a concrete floor and floating walls and ceiling (Kinetics IsoClips). It works pretty durn well but since I suspended the ceiling from clips to the floor above instead of floating on the walls (due to construction issues -- would have been much harder and taken away from room volume) I can still hear loud footfalls in the kitchen above. However, it is almost impossible to hear anything from the room anyplace else in the house.

Make sure you isolate from the house HVAC system. I added outside ducts just for the media room and a minisplit for climate control.

It's a freestanding building built from lightweight expanded clay aggregate (leca) blocks. It has wood panelling with a air pocket behind on the outside, single layer drywall on wood 2x2s directly on the blocks and insulation on the inside. No windows, one door, one attic hatch. It wasn't built for sound purposes as you well understand. Unfortunately, I was only discussing internal acoustics with my consultant not soundproofing against the exterior so I've almost completed the inside with a new thick rear dampening wall, basstrap riser, diffusion on side walls etcetera, so when it failed on the trial run I was pretty sad. Now, I didn't initially realize just how high I was playing, the loudspeakers are very well behaved up to ridicolous volumes, so it does work to use as it is with average volumes of 85dB, but that's not my ultimate goal - I can do that already in the tv-room.

HVAC? I'm in Sweden, we don't use those - we're Vikings.

Got it. Unfortunately, acoustic room treatments don't generally do much for isolation; for that, floating walls and mass are the usual tickets, then treat the inside walls to taste. I have drawings I gave my contractor to help guide our media room I would be glad to email, and Ethan has a lot of info on his site, plus there is a lot of info on the Kinetics and Mason web sites.

p.s. effective isolation makes the room air-tight, or nearly, so you'll want to add ducting for fresh air, with baffling and such to reduce sound transmission (either way).

My biz partner built an isolation room for a rock&roll/metal drummer. so he could practice and fuse the muse..at 3am, while his wife and kids where sleeping upstairs. 2 story house, cement basement, cinderblock drywall, etc ...the system was retrofitted.

It has PERFECT sonic balance in room, down into the lows..and PERFECT isolation from the house and the upstairs, so the drummer can practically explode the skins and the kick drum. I'll re-iterate: full power drum kit*, perfect balance (also a recording studio), and perfect isolation. That's what he does.......

peak pressure on the wall surface, is ~130db.

KBK said:

peak pressure on the wall surface, is ~130db.

Click to expand...

I had a metal drummer in one of my rooms also hitting 130dB peaks. You could not hear it upstairs or outside the double doors. This is a room within a room using Kinetics Noise control and Zero International products. The neighbors love us!

DonH50 said:

Got it. Unfortunately, acoustic room treatments don't generally do much for isolation; for that, floating walls and mass are the usual tickets, then treat the inside walls to taste. I have drawings I gave my contractor to help guide our media room I would be glad to email, and Ethan has a lot of info on his site, plus there is a lot of info on the Kinetics and Mason web sites.

p.s. effective isolation makes the room air-tight, or nearly, so you'll want to add ducting for fresh air, with baffling and such to reduce sound transmission (either way).

Click to expand...

Yeah, I know that, they weren't intended to, it was assumed on both hands that the building was good enough to begin with.

Mass I'm definitely onboard with - have some ideas there already. Floated walls I still would like to have more data about sub 20 behaviour - and I really havent't found a source for over here.

If we notice a problem with the air during a single movie session, I'll have to do something. In it's current state there's no issue at all, but that might change when I get it better soundproofed later.