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

[DonH56]

Proven by headphones, no?

Good point!

Better page about basics on sound propagation - sound is propagating pressure variations (wavefront), not "waves" Wave is just a graphical presentation of pressure vs. time at certain spot in space. One cycle is pressure going up and down periodically. Frequency of cycle period is Herz ( one Hz is one cycle per second)

http://artsites.ucsc.edu/EMS/Music/tech_background/TE-01/teces_01.html

simulations
https://www.acs.psu.edu/drussell/demos.html

This.

 

[mitchco]

Because even moving the mic a few centimeters can reveal very different peaks and dips under 1 kHz. But a head has two ears distant from each other, and there are various ways to sit on a seat, and one can move according to the rhythm... How do you deal with that?

I have done countless measurements in my living room (200 hours of playing with a calibrated Behringer ECM8000, REW and RePhase perhaps), and my corrections and even measurements themselves never were 100% satisfying.

In my small room it was even less consistent. I had to window down to 2ms to have the speakers answer and lost everything certain under 2 kHz or so. As for peaks and dips in the lows, they move according to the placement. When I try to correct that, it sounds awful.

It would be great to see some measurements just to see what you are dealing with in the way of room modes. Can you share an .mdat of left and right channels measured at the LP? Don't gate the measurement, just use REW's default window of 500ms as we do want to see what is happening down low. Yes, I get it is only in one position in the room, but the reality is the room modes are (pre)determined by the physical dimensions of the room and by moving the mic all you are doing is measuring some portion of the peaks and valleys of the room modes, but they are still there

Wrt rePhase, while it is possible to use rePhase to correct for room issues, it is intended to be a loudspeaker design tool. OTOH, proper room correction software is designed not to boost nulls, but reduce peaks and fill in some of the nulls based on the transient response analysis of the room. The result is a more even bass response over a wider sweet spot and not over correcting at a single position. Of course you can take measurements at multiple positions and then average, but I have found the transient response analysis algorithms used in some room correction software does a great job of averaging with a single pair of measurements with multiple measurements at different positions offering no additional benefit. OTOH hand some room correction software like Dirac Live, do require multiple measurements as it is using a different analysis algorithm.

While neither here or there, the place to start is to look at the measured response as currently setup and then based on some analysis, see what the possibilities are.

 

[daftcombo]

It would be great to see some measurements just to see what you are dealing with in the way of room modes. Can you share an .mdat of left and right channels measured at the LP? Don't gate the measurement, just use REW's default window of 500ms as we do want to see what is happening down low. Yes, I get it is only in one position in the room, but the reality is the room modes are (pre)determined by the physical dimensions of the room and by moving the mic all you are doing is measuring some portion of the peaks and valleys of the room modes, but they are still there

Wrt rePhase, while it is possible to use rePhase to correct for room issues, it is intended to be a loudspeaker design tool. OTOH, proper room correction software is designed not to boost nulls, but reduce peaks and fill in some of the nulls based on the transient response analysis of the room. The result is a more even bass response over a wider sweet spot and not over correcting at a single position. Of course you can take measurements at multiple positions and then average, but I have found the transient response analysis algorithms used in some room correction software does a great job of averaging with a single pair of measurements with multiple measurements at different positions offering no additional benefit. OTOH hand some room correction software like Dirac Live, do require multiple measurements as it is using a different analysis algorithm.

While neither here or there, the place to start is to look at the measured response as currently setup and then based on some analysis, see what the possibilities are.

I am not at home now but will do.

 

[Juhazi]

Basically, the room's simulated standing waves (modes) determined by dimensions will tell a lot. Below the lowest mode bass response will be very nice and flat! Car cabinets have also high damping characteristics (extremely low RT). Room wall, floor and ceiling materials are important for modes (damping). I noticed that if I open the door of my small room it will become a Helmholz resonator around 20Hz, while lowest mode is around 40Hz!

REW has very good room sim similar to this. You can even set placement and height for speakers and use irregular room shape!
https://www.hunecke.de/en/calculators/loudspeakers.html

This one shows modes of daftcombo nicely, lowest around 57Hz https://amcoustics.com/tools/amroc?l=300&w=250&h=260&r60=0.6

 

[soundwave76]

Yes, it can make sense a lot. I use a pair of Genelec 8331 in near-field desktop use in a smallish room. The sound was fabulous but there was a huge -15dB dip around 80Hz and I couldn't really move the speakers. So I ordered the smallest SAM sub Genelec has (7350) and when I calibrated it, the dip was gone and the sound improved A LOT.

 

[audiophile]

I just finished setting up two subwoofers in a small room (4x3 m). It was impossible to eliminate room modes just with sub placement, so I had to do some EQ. The subs are connected via miniDSP that splits low frequencies into 2 bands (10-40 Hz and 40-80 Hz), EQs each band individually and sends signal to the subs. The whole process of taking measurements in REW and finding the right EQ settings with some manual adjustments took a full day. I like the result so far, the subs integrated very well with each other and the speakers. Btw the main signal to the speakers does not go through miniDSP, it was already pretty smooth due to optimal placement and some room treatments.

 

[daftcombo]

I use a pair of Genelec 8331

20 times the price of my JBL 305p, it'd better sound supergood!

 

[Juhazi]

We must remember that any placement trick or eq will not remove modes! We can only try to find the best possible locations for speakers and ears (mic). When all that is done, some clever EQ will help to tame response peaks that are left.

Vertical mode is difficult, beause often ears are just in midline - here my small HT room responses at ear vs. butt level! Suvwoofer amp is Hypex DS2.0 which has a highpass filter that makes the response drop fast below 20Hz (sealed 2x15" sub) Notice flatness below 45Hz and that 18Hz is Helmholz resonance caused by the open door. Room is 3x4x2,8m.

 

[daftcombo]

What do you think of this guy's talk?

 

[bravomail]

So, I have a 3rd system in a very small room (3 m * 2,5 m, that is to say 10ft * 8ft approximatively) for late night chill-out.
It is composed of a Sony DVD player, a JDS Lab Atom used as headphones amp and pre-amp for a pair of JBL 305p mkII.
In this room I mostly listen to piano, but also electronic music at times while browsing this site on my phone (I-F "mixed up in the Hague" for instance).

My question is: would there be any improvement with a JBL 310s subwoofer (or any subwoofer)? As I listen at very moderate volume, wouldn't it be better to have more bass in order to actually hear it?

Cheers.

In my case, for movies only. There are some movies made specifically for subwoofer owners. Like "Edge of Tomorrow". In general, it will be good for music too. But u will notice it in the movies.

 

[daftcombo]

In my case, for movies only. There are some movies made specifically for subwoofer owners. Like "Edge of Tomorrow". In general, it will be good for music too. But u will notice it in the movies.

The movies I watch are usually too old to even have sound, let alone surround and bass effects. But for orchestral masses it would be a plus I think.

 

[Krunok]

. Of course you can take measurements at multiple positions and then average, but I have found the transient response analysis algorithms used in some room correction software does a great job of averaging with a single pair of measurements with multiple measurements at different positions offering no additional benefit. OTOH hand some room correction software like Dirac Live, do require multiple measurements as it is using a different analysis algorithm.

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.

 

[Absolute]

Here's multi-point measurements after Audiolense (single point room correction) in my room (apartment with concrete and gypsum walls). Rectangular room with listening area on one end and couch back against wall and corner. About 1-1,5m between Main LP and the farthest away to each side. The biggest differences comes from the points measured nearest corner;

And a closer look at bass frequencies;

 

[Absolute]

I have the luxury of having both Dirac and Audiolense as well as manual EQ in the form of Minidsp 4x10hd and I find that what you use is not as important as how you use it.
Dirac needs multi-point measurements, otherwise the sound quality will suffer greatly. Audiolense works good with one-point measurement, but needs different target curve than Dirac and will probably need some tinkering with some advanced settings to avoid over-correction.

Right now I prefer manual EQ where I have taken near-field measurements of Klipsch RP160M and averaged 9 points to get "listening window" and then auto-corrected that in REW, and have also used two subs up front with different crossovers and timing to reduce decay-times as much as possible.
That makes the step-response look worse, but I prefer a punchy bass over flat bass.

Correcting this with Audiolense is weird, because Audiolense fixes the timing to such an extent that the step response is perfect, the frequency response perfect, but it also increases decay-times at various frequencies and makes the bass softer and far less articulated. Haven't done too much tinkering with this yet as the manuel EQ just works so well for now.

 

[Krunok]

Correcting this with Audiolense is weird, because Audiolense fixes the timing to such an extent that the step response is perfect, the frequency response perfect, but it also increases decay-times at various frequencies and makes the bass softer and far less articulated. Haven't done too much tinkering with this yet as the manuel EQ just works so well for now.

Hmm..

Primary goal of every correction is to get flat frequency response as that is the most important parameter in our perception of SQ. To achieve that peaks are pushed down which also helps with decay time. LF dips, esepcially narrow ones, are usually not corrected that much so decay time, which is exclusive characteristic of the room, will stay pretty much intact. Getting the timing right usually helps with bass definition ("slam") when bass is acccompanied with higher frequency signals but it won't affect decay time at all.

So, usually you actually get an improvement in decay graph after Audiolense, or any other properly executed correction. But even if you don't, getting the FR in your room according to your preferred tarrget curve is by far the most important thing for perceived SQ. Assuming that your speakers have smooth off-axis response this will certainly do the trick, and all other paramters, including decay, phase, THD etc have been shown not to be that important.

Maybe you can post decay graphs for each channel before and after Audiolense correction to demonstrate what you exactly mean?

 

[soundwave76]

20 times the price of my JBL 305p, it'd better sound supergood!

They do

 

[daftcombo]

They do

How far from them do you listen?
I suspect that most monitors sound good BECAUSE people listen close to them.

 

[soundwave76]

About 50cm, which works very well for 8331 according to Genelec

 

[Absolute]

Hmm..

Primary goal of every correction is to get flat frequency response as that is the most important parameter in our perception of SQ. To achieve that peaks are pushed down which also helps with decay time. LF dips, esepcially narrow ones, are usually not corrected that much so decay time, which is exclusive characteristic of the room, will stay pretty much intact. Getting the timing right usually helps with bass definition ("slam") when bass is acccompanied with higher frequency signals but it won't affect decay time at all.

So, usually you actually get an improvement in decay graph after Audiolense, or any other properly executed correction. But even if you don't, getting the FR in your room according to your preferred tarrget curve is by far the most important thing for perceived SQ. Assuming that your speakers have smooth off-axis response this will certainly do the trick, and all other paramters, including decay, phase, THD etc have been shown not to be that important.

Maybe you can post decay graphs for each channel before and after Audiolense correction to demonstrate what you exactly mean?

This is, of course, all true. In this particular case, however, I've experimented with different timings and x-overs on the two subs to minimize decay in the problem areas of 40-70 hz in my room at the expense of perfect step-response and frequency response.
The reason for this experiment is that both Toole and Geddes says frequency response is all that matters in the bass, but these claims are not unchallenged. Some acoustic experts beg to differ and claim different findings. Bob Hodas says both timing and decay are more important than frequency response. Ethan Winer disagrees strongly with Toole.

Personally I don't care who says what, I test to the best of my abilities to see what I agree with. It seems I didn't store the measurements, I'll have to come back to it. My initial impression based on switching on and off Audiolense is that the bass softens and loses punch. It could be due to some other factor further up the range, so I'll make sure to get back to it with measurements and more specific testing.

OP, I'm sorry for the off-topic. Subs in a small room not only makes sense, it's mandatory if high fidelity is a goal. One should just get used to the idea of multiple subs from the start, because Spock says subs are the logical solution to room problems in the bass.

 

[Krunok]

The reason for this experiment is that both Toole and Geddes says frequency response is all that matters in the bass, but these claims are not unchallenged. Some acoustic experts beg to differ and claim different findings. Bob Hodas says both timing and decay are more important than frequency response. Ethan Winer disagrees strongly with Toole.

Don't get me wrong, but comparing true scientists like Toole, Olive, Geddes, D'Appolito etc with the guys you're mentioning simply doesn't make sense. While Toole, Olive and Geddes conducted serious listening tests to prove their thesis or coming to new conclusions based on them, Ethan Winer, Paul McGowan and other wannabe scientists were making Youtube videos based on their personal opinions. Let's not forget that problem with opinions is they are like asshole - everybody has one, right? But for providing a valid argument to support your opinion you need to follow scientific approach, so comparing Toole and other true scientists with a crowd like Ethan Winer, Paul McGowan etc looks simply ridiculous to me. No offense meant here toward you, of course..