So, what's with room gain?

[mrstampe]

It's pretty impressive what room gain can contribute to the low end response of a subwoofer. Is it all just trial and error, or are there features of the room that can predict how the room will respond? For instance, do all of these things matter: floor plan geometry, room volume, wall treatments, types of furniture, upward-/downward-/forward-firing SW driver, SW placement, listening position, etc?

[Darren]

All of those things matter. Placing a sub in the corner of a room boosts room gain in most instances. A rooms dimensions drastically affects the response and gain of a subwoofer. You can experiment with REW and different placement of your sub to really get a feel for it.

[Kevin Haskins]

Its actually two separate things. There is the boundary gain that you get from the operation in non-4Pi space. In non-technical jargon that means that the output of the driver is focused into a smaller space. Less space = more apparent output.

The other type of gain is the pressure-vessel gain. Below a certain frequency the room no longer supports standing waves. When the wavelength is greater than the room dimensions, you get a uniform pressurization of the room. You get more gain as frequency decreases so its called "room gain". This is more apparent in small tightly sealed environments. Cars are a great example and the pressure vessel gain you get inside that environment is substantial. Its occurs lower in frequency and to a lesser extent inside a room. Typical living spaces are not tightly sealed acoustic chambers and their construction varies, giving different results depending on the physical properties of the floor, wall, ceiling, etc… Boundaries that are sturdy and stiff (concrete) give more re-enforcement than does stick-built or flexible building materials that will absorb some of the energy. Think of the Three Little Pigs. ;-)

[Avus_M3]

Is there any way we can adjust for room gain before actually building our subs so we could some what account for it?

[avaserfi]

Avus_M3 wrote:

Is there any way we can adjust for room gain before actually building our subs so we could some what account for it?

You can't really adjust for it before hand, but with parametric equalizer like the BFD you can cut frequencies that are boosted too much easily so it doesn't end up being much of a problem.

[Ilkka]

Avus_M3 wrote:

Is there any way we can adjust for room gain before actually building our subs so we could some what account for it?

Anything other than a direct frequency response measurement will be pure speculation. Of course you have to have a subwoofer which anechoic frequency response you know in order to have a successful measurement. Usually post-EQ is a very good and efficient method for handling any excessive room gain down low.

[mrstampe]

Ilkka wrote:

Anything other than a direct frequency response measurement will be pure speculation. Of course you have to have a subwoofer which anechoic frequency response you know in order to have a successful measurement. Usually post-EQ is a very good and efficient method for handling any excessive room gain down low.

Room planning before the sub build?

Is it possible to boost low end room gain with specific room attributes (mentioned above) sufficiently to make a sealed enclosure have LFE response similar to a LLT/same driver without these room attributes. In other words, can I minimize cabinet size and maximize build simplicity in a sealed cabinet, while "engineering" great LFE through proper wall construction, room geometry, furnishings, and other attributes?

[avaserfi]

mrstampe wrote:

Room planning before the sub build?

Is it possible to boost low end room gain with specific room attributes (mentioned above) sufficiently to make a sealed enclosure have LFE response similar to a LLT/same driver without these room attributes. In other words, can I minimize cabinet size and maximize build simplicity in a sealed cabinet, while "engineering" great LFE through proper wall construction, room geometry, furnishings, and other attributes?

Rather than attempting to design a room around a small sub there is a better option - you could use a smaller sealed cabinet for the sub but choose a driver with a large linear excursion capabilities and high power handling ability. By pairing it with a PEQ and a lot of power you could achieve this end. This is a more costly solution than an LLT solution but will work better than hoping for appropriate room gain which is a hit or miss situation.

Audiopulse makes some good drivers in this regard another option would be something like the JLW7 which would be a monster in this situation.

[Geoff St. Germain]

avaserfi wrote:

Rather than attempting to design a room around a small sub there is a better option - you could use a smaller sealed cabinet for the sub but choose a driver with a large linear excursion capabilities and high power handling ability. By pairing it with a PEQ and a lot of power you could achieve this end. This is a more costly solution than an LLT solution but will work better than hoping for appropriate room gain which is a hit or miss situation.

Audiopulse makes some good drivers in this regard another option would be something like the JLW7 which would be a monster in this situation.

You can do the same thing with an LLT, you'll just require less boost.

[avaserfi]

Geoff St. Germain wrote:

You can do the same thing with an LLT, you'll just require less boost.

I was under the impression LLT stands for large and low tuned I was replying to someone who wanted a smaller subwoofer .

[mrstampe]

avaserfi wrote:

I was under the impression LLT stands for large and low tuned I was replying to someone who wanted a smaller subwoofer .

In just a couple years, I'm planning a move to a larger house with more room for everything, including a pair of LLT subs. For now, the goal is to maximize my low end response in a smaller sealed enclosure. Maybe it's too much to ask of this design, and this is more of an academic exercise...

All I'm asking is, is it possible to boost the lower lows with room gain by properly maximizing room features (in addition to parametric eq)?

If not, I'll just bite the bullet and port that thing.

[avaserfi]

avaserfi wrote:

Rather than attempting to design a room around a small sub there is a better option - you could use a smaller sealed cabinet for the sub but choose a driver with a large linear excursion capabilities and high power handling ability. By pairing it with a PEQ and a lot of power you could achieve this end. This is a more costly solution than an LLT solution but will work better than hoping for appropriate room gain which is a hit or miss situation.

Audiopulse makes some good drivers in this regard another option would be something like the JLW7 which would be a monster in this situation.

mrstampe wrote:

In just a couple years, I'm planning a move to a larger house with more room for everything, including a pair of LLT subs. For now, the goal is to maximize my low end response in a smaller sealed enclosure. Maybe it's too much to ask of this design, and this is more of an academic exercise...

All I'm asking is, is it possible to boost the lower lows with room gain by properly maximizing room features (in addition to parametric eq)? f

If not, I'll just bite the bullet and port that thing.

I suggest you read my above quote as it answers this situation.

Rest assured with the proper driver you will be able to reach pretty low (mid to high teens) with the right driver and proper amounts of power, but this can get costly quick. LLTs are often chosen because they are far more cost effective than the option I suggested, but the problem is, of course, they are large.

Room gain can help, but is not reliable enough to count on IMHO.

[Lobotomy^]

hello everybody, my first post.

I did found THIS useful, when estimating room gains. Just set options to match your room and speaker. Then set listening position and speaker positions. Graph gives you estimate of room gain and standing waves effects at listening post for one speaker at the time.

[atledreier]

What an AWESOME tool! This match my measurements and experience exactly! Thanks a lot! What an easy way to experiment with placement. Too bad it doesn't do subwoofers, but I used a center that goes pretty deep and moved around to where the sub needs to go and fudged it that way. Awesome stuff!

[mrstampe]

Very cool! It looks like there are quite a few manufactured speaker lines included, but no Paradigms. Has anyone else had experience using this calc? Anything comparable out there for subwoofers?

[looneybomber]

mrstampe wrote:

In just a couple years, I'm planning a move to a larger house with more room for everything, including a pair of LLT subs. For now, the goal is to maximize my low end response in a smaller sealed enclosure. Maybe it's too much to ask of this design, and this is more of an academic exercise...

All I'm asking is, is it possible to boost the lower lows with room gain by properly maximizing room features (in addition to parametric eq)?

If not, I'll just bite the bullet and port that thing.

To get a significant change would require a remodelling of your room. Decreasing room volume and stiffening walls would do the trick...but would require more money and work than it would to install a few 18's in your ceiling. Plus, it would be a very dumb idea.

[mrstampe]

looneybomber wrote:

Plus, it would be a very dumb idea.

Take it easy Kansas, we're just having a theoretical conversation here.