Subwoofer in a very small room: does it make sense?

[mitchco]

Hi MItch,

first let me congratulate you on this project and wish you many happy customers!

Unfortunately there is no way for any analysis made on a single point measurement to conclude/calculate what is happening at other room points as that inforomation is not contained in a single point measurement - single point measurement contains only information about that single point.

As we are well aware room is a major factor for the frequencies up to a Schroeder freq and also play some role in the transiton range (usually up to 500-600Hz). Major factor, beside dimensions of the room, is densitiy of the material from which walls, ceiling and floor is made. The denser the material the more reflections in LF range will occur in the room - wall made of iron reinforced concrete or heavy bricks will reflect much more LF frequencies than wall made of light materials, like combination of wood and plaster.

To summarise: larger rooms with walls made of light materials will have more uniform distribution so measurement made at center of LP won't differ much from the one made 50cm apart, but in smaller rooms with walls made from dense (heavy) materials you can find significant differences in measurements even if you move mic only 25cm away, and in these situations spatial averaging (as suggested by Toole) is the only way to deal with that. It also goes without saying that the larger the area you are optimising the response for the larger would be the need to work with averaged measurements instead with those made at a single point.

Hello @Krunok

Thanks! Happy New Year! As @Absolute says, I also have the luxury of using Dirac 2.0, Audiolense, Acourate and REW using MMM, all on the same set of Purifi SPK4 demo speakers in the same room and can evaluate each and compare the analysis and correction algorithms. I can tell you definitively that the single point measurement works just as well as the multi point or averages or MMM. That is because some DSP software are using a different analysis algorithm that looks at the transient response of the room and not the steady state response.

A keen eye will note what is going on in the analysis algorithm at low frequencies and the reason why it can work across a wide listening area. I will be posting the measurement and analysis results of each of these in a DSP "shoot out" article soon. As a foreshadow, the results of using one single point analysis measurement (with the transient response analysis algo) and then measuring the correction in 14 locations across a 6' x 2' grid area (i.e. my 3 seat couch) is already shown in my DSP book. As one can see, the results are smooth and consistent frequency (and timing!) response across all locations.

Also folks should know that you can you can indeed reduce "room resonances" with DSP. Room Shaper is such a product that produces measurable and audible benefits of dramatically reducing room resonances (i.e. low frequency decay time).

Anyway, don't want to pollute the thread with OT comments or have the same argument over and over For the OP, I agree with @Absolute, subs in a small room is not only encouraged, but mandatory for high fidelity.

 

[Krunok]

A keen eye will note what is going on in the analysis algorithm at low frequencies and the reason why it can work across a wide listening area. I will be posting the measurement and analysis results of each of these in a DSP "shoot out" article soon. As a foreshadow, the results of using one single point analysis measurement (with the transient response analysis algo) and then measuring the correction in 14 locations across a 6' x 2' grid area (i.e. my 3 seat couch) is already shown in my DSP book. As one can see, the results are smooth and consistent frequency (and timing!) response across all locations.

Well, single point measurement may work for your room and a number of other rooms you made measurements in, but you can't really draw a general conclusion from that that it works for every room. My point was that in cases where it doesn't work (like in my room) you can't derive any data from a single point measurement about the response in wider area around the single point you measured. The only solution in that case is to mmake spatial averaged memasurement.

Also folks should know that you can you can indeed reduce "room resonances" with DSP. Room Shaper is such a product that produces measurable and audible benefits of dramatically reducing room resonances (i.e. low frequency decay time).

We agree on that.

For the OP, I agree with @Absolute, subs in a small room is not only encouraged, but mandatory for high fidelity.

We agree on that as well.

 

[Sparky]

The problem with bass in a small room is that the room modes will be at higher frequencies and hence will be more obnoxious. And they will have their harmonics at even higher frequencies. Dealing with them with bass traps is obviously not on, given the small size of the room, and equalizing them is of course possible, but the optimum listening position will be narrower, the higher the equalized frequency. In short, I think adding deep bass in a small room is not a good idea if you hate room modes and woolly slow bass (as I do).
Mind you, this is from someone who likes deep bass, and has a flat in-room response down to 13 Hz in his large main listening room (but only small Harbeth P3ESRs in his study).

@Willem

How big is your study and are the Harbeths forgiving of placement due to them being a sealed box?
Always had a soft spot for the P3ESR's.

 

[thomasjast]

Hmm? A car is much smaller than your room and it totally makes a difference.