• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

How a subwoofer affects soundstage?

Miguelón

Addicted to Fun and Learning
Forum Donor
Joined
Mar 12, 2024
Messages
521
Likes
305
Location
Vigo (Galicia, Spain)
Hello, I never used a subwoofer and want to complete my Genelec 8020D stereo setup.

I’m complete naive with 2.1 systems, if I only install one sub (7040 in this case) this one will reproduce mono signal mixing left and right channels, so this will not cause phase cancellation and imaging degradation?

I red on the Genelec website the phase alignment with one of the monitors, so the other will be out of phase.
Can anyone oriented me if is a good idea for to complete my setup with the 7040 given that I listen to classical music most of time or use the monitors on my Kawai ES920 digital piano?
 
Bass in home sized room is combined, so you don't hear in stereo for bass. So even with 2 subs you don't separately hear the left and right sub unless placed next to your ears. The single sub is not a problem.

One of the reasons to combine all the bass and send it to the subwoofer is so that we get a consistent bass response. This is true for stereo or multi-channel. For example if we just had the two speakers and they are full range. If we play bass out of the left speaker only, we will get a certain frequency response at the listening position. If we play bass out of the right speaker only we will get a different bass frequency response. If we combine the bass and play it out of both speakers we will again get another different bass response. So having the subwoofer handle all the bass will give us the same frequency response no matter which speaker the bass was coming.

Phase needs to be correct at the crossover frequency, in this case 85hz. Think of it this way for illustration purposes. The woofers of the speakers and the woofer of the sub need to be in unison and going in and out at the same time for it to sound correct. If the speakers are going out and the sub is going in you will have phase cancellation

Now, that is not technically correct or should I say only correct if the speakers and the subs are all near each other. But since the subs are likely a different distance from the listening position then the speakers, we need to make sure the bass at the crossover frequency reaches the listening position at the same time. Genelec has a procedure for this in their manual and they have the 85 Hertz sine wave test tone on their website. So use that test tone and follow their procedure. For this purpose you need relative measurements and one of the various free apps for an SPL meter or RTA can be used on a phone. You don't need a super accurate microphone as it is a relative measurement and you don't need any special measurement software.

 
There is no localization below 80-100 Hz so that is not an argument in favour of stereo subs. However, there are real advantages in summing the two channels at these low frequencies, because two subs in different locations have different peaks and dips from room modes, and summing those will smoothen the response. Two mono subs with dsp room equalization is about the minimum for clean low frequency sound. The most sophisticated dsp equalization software is probably Multi Sub Optimizer. I have achieved very good results and over a wide listening area using three subs in uncorrelated locations, and equalized by MSO. Particularly user friendly MSO is not, unfortunately.
 
Bass in home sized room is combined, so you don't hear in stereo for bass. So even with 2 subs you don't separately hear the left and right sub unless placed next to your ears. The single sub is not a problem.

One of the reasons to combine all the bass and send it to the subwoofer is so that we get a consistent bass response. This is true for stereo or multi-channel. For example if we just had the two speakers and they are full range. If we play bass out of the left speaker only, we will get a certain frequency response at the listening position. If we play bass out of the right speaker only we will get a different bass frequency response. If we combine the bass and play it out of both speakers we will again get another different bass response. So having the subwoofer handle all the bass will give us the same frequency response no matter which speaker the bass was coming.

Phase needs to be correct at the crossover frequency, in this case 85hz. Think of it this way for illustration purposes. The woofers of the speakers and the woofer of the sub need to be in unison and going in and out at the same time for it to sound correct. If the speakers are going out and the sub is going in you will have phase cancellation

Now, that is not technically correct or should I say only correct if the speakers and the subs are all near each other. But since the subs are likely a different distance from the listening position then the speakers, we need to make sure the bass at the crossover frequency reaches the listening position at the same time. Genelec has a procedure for this in their manual and they have the 85 Hertz sine wave test tone on their website. So use that test tone and follow their procedure. For this purpose you need relative measurements and one of the various free apps for an SPL meter or RTA can be used on a phone. You don't need a super accurate microphone as it is a relative measurement and you don't need any special measurement software.

Thank you so much for your clever explanations!
I guess that at bass range sound waves behaves more stationary-like on a room than radiated-like…

Very happy to learn that one sub will improve the sound experience, as I like a lot the room response of the 8020s but I miss one octave more on the low range.

I did a lot of comparisons with the 8030 in my living room but no matter the place or the dip switches adjustments the 8020 sounded better at its frequency range.

Happily our budget allows us to a pair of 8020 plus the 7040, which I think will be better arrangement than 2 x 8030s (with or without sub) for our listening conditions.

I will careful align 7040 when will arrive, I suppose that setting it with mathematics (85 Hz wave length, sound speed and the sound path time delay) will not work in practice to find the phase correction…
 
In the end, the more subwoofers, the smoother the response. Two mono subs in uncorrelated positions is the minimum, Earl Geddes says three, and others even four. In all cases you will need some form of dsp room equalization. If size is a problem, multiple subs do not have to be as large. In fact, one larger sub with one or more smaller subs works very well. For dsp room equalization I have found Multi Sub Optimizer very good, although not easy to implement. Its biggest advantage is that it equalizes the subwoofers individually, for the optimally smooth response over a wide listening area. I have no idea if there are issues if you do this with Genelecs.
 
In the end, the more subwoofers, the smoother the response. Two mono subs in uncorrelated positions is the minimum, Earl Geddes says three, and others even four. In all cases you will need some form of dsp room equalization. If size is a problem, multiple subs do not have to be as large. In fact, one larger sub with one or more smaller subs works very well. For dsp room equalization I have found Multi Sub Optimizer very good, although not easy to implement. Its biggest advantage is that it equalizes the subwoofers individually, for the optimally smooth response over a wide listening area. I have no idea if there are issues if you do this with Genelecs.
In my world, the more subwoofers the hardest the response… the response of my neighbors downstairs I mean.

I will try before with one, just by economic and diplomatic principies :)
 
In my world, the more subwoofers the hardest the response… the response of my neighbors downstairs I mean.
Not necessarily. Additional subwoofers add headroom, yes, but that doesn't mean you need to use it. If you are after a more linear response and not more output, you can simply turn each sub down to compensate. Each sub also works less hard in this case which could be a side benefit.
 
There is no localization below 80-100 Hz so that is not an argument in favour of stereo subs. However, there are real advantages in summing the two channels at these low frequencies, because two subs in different locations have different peaks and dips from room modes, and summing those will smoothen the response. Two mono subs with dsp room equalization is about the minimum for clean low frequency sound. The most sophisticated dsp equalization software is probably Multi Sub Optimizer. I have achieved very good results and over a wide listening area using three subs in uncorrelated locations, and equalized by MSO. Particularly user friendly MSO is not, unfortunately.
They say that, but in practice I found you could determine to a degree where the sound was coming from. If the sub was situated totally off the stereo field, and well off relative to where you sit in the room.

I’m not sure exactly where I cut the DSP off in the end, but it was ‘a lot’ lower than I expected, around 30-40 IIRC. Below that it was more or less invisible where the low frequencies were emanating from, but I was really quite surprised, and disappointed in some ways, as I wanted more from the subs higher octaves. But when I did, it started to make itself known where it was.

However, if it was nearer the main speakers then yes it could have gone much higher and no one would know where it was, it could have just been coming from the speakers area.

As for the OP question, soundstage. SS is just an illusion anyway and in my opinion totally subjective. What a sub does though is to me makes the image fuller, and the room is filled more with all the sound. I’ve used singles and doubles, but I’m more than happy with one sub at a time. It makes the sound much more immersive, and you do feel like there’s something missing when it's off. And I suppose there is, the lower frequencies :) They do make a big difference. I still listen to main speakers without though a lot of the time. It’s nice to have the option. If you have big speakers with the low drivers continually working, you haven’t got that option. Subs are a great way to add bass and that fuller range room filling sound to any system, which is fully customizable as well.
 
I have a single subwoofer tuned for my listening position using DSP. It works well - I have a relatively flat frequency response at that position.

Multiple subs generally work better, though, if you are tuning over a larger area.
 
If you can get a measurement mic and REW, then you can see what is happening in your room. My living room, for example, had a bass null that I could not correct given the limited places I could put a single subwoofer. So I had to add a second, smaller, sub in the rear of the room. That fixed it. As the cost of the measurement mic is much less than a good sub, it's useful to have those tools so you know the problem (if any) you are trying to fix before spending $ on another sub.
 
They say that, but in practice I found you could determine to a degree where the sound was coming from. If the sub was situated totally off the stereo field, and well off relative to where you sit in the room.

I’m not sure exactly where I cut the DSP off in the end, but it was ‘a lot’ lower than I expected, around 30-40 IIRC. Below that it was more or less invisible where the low frequencies were emanating from, but I was really quite surprised, and disappointed in some ways, as I wanted more from the subs higher octaves. But when I did, it started to make itself known where it was.

More subs help with this as well. It's absolutely possible to localize a single sub crossed at 80Hz (or even much lower) depending on a variety of factors (positioning relative to the MLP, boundary gain, quality of integration with the mains, activation of room modes, etc). This won't be the case for every situation, of course.

I have a basement setup with which to do whatever I wish, but the family room is another matter. I purchased two small subs for this room. There are two, and only two, possible positions for subs in the family room that pass muster with my wife (it's a minor miracle that she tolerates the presence of any at all). One of these subs delivered before the other, so I set it up in the first position and listened. With an 80Hz crossover, as soon as I juiced it up at all it was easily localized, despite the fact that it was positioned within the span of the main stereo speakers. Once the second sub arrived and was aligned, the localization vanished entirely, and I can turn them up as desired without their positions being made known. Two (or more) subs are almost always better than one, for a variety of reasons.
 
Last edited:
I’m not sure exactly where I cut the DSP off in the end, but it was ‘a lot’ lower than I expected, around 30-40 IIRC. Below that it was more or less invisible where the low frequencies were emanating from, but I was really quite surprised, and disappointed in some ways, as I wanted more from the subs higher octaves. But when I did, it started to make itself known where it was.
Much depends on the subwoofer location, crossover slope, room characteristics, etc. I am crossed over at 100 Hz with a 48 dB/octave slope. The sub is behind the plane of the speakers, and to the right. All of the sound appears to be coming from the speakers. The subwoofer is transparent.

Also, I plugged my speaker ports to reduce their group delay in the crossover region. That helped a lot. It tightened up the bass and resulted in a smoother transition between the subwoofer and the speakers in the crossover region.

Lastly, I am using bookshelf speakers with 6 1/2" woofers. Their harmonic distortion increases significantly below 100 Hz. Some say the HD is not audible. But I took measures to improve the HD and to me it seems to have improved sounds staging and imaging.
 
It's ok to talk about using only 1 sub.

Using 2 subs is a different conversation, substantially better and more accurate results.
 
Two or more subs is really about getting a more consistent response at each seat. If you only care about one seat or maybe two if they are close enough and fall in the similar acoustic locations. To get a correct bass response EQ will almost always be needed whether you want one listening position or multiple listening locations. If you only care about one location you can find a good location for the sub and good location for the seat. That location should not have an major dips in response, peaks are OK as they can be EQ'd. Apply your EQ and your done. The problem comes is these locations are not always how we want to set up our room.

Multiple seats are always harder. Ideally you find seating in similar acoustic locations that way EQ works for all of them. As a generalization in a rectangular room avoid seating in the middle or quarter points of any dimension. Also, avoid seating near walls or corners. Seating placement defnitely helps! This is where 2 or more subs helps and takes more time to find good locations and set up properly. However, you can get a similar bass response in the various seats and again EQ will be needed.
 
Thank you for all answers, as I could understand 1 subwoofer is better than 0, 2 subwoofers better than 1 and there is even one expert that proposes an indefinite amount of subs with the only limit of the habitable space.

My original question was enough answered and more, thus 2.1 system will have better soundstage than 2.0

For instance one only subwoofer will enough for me, specially for my bank account as the more affordable sub that Genelec proposes is 800€

Hope I will enjoy it!
 
I have a single subwoofer tuned for my listening position using DSP. It works well - I have a relatively flat frequency response at that position.

Multiple subs generally work better, though, if you are tuning over a larger area.
My living room is 4x3 meters, I think that one will be enough.
I finally keep the 8030s (have both 8020 and 8030 to compare) that fill quite well my room.

As I red in other post, one member also get a nice flat response with adding the 7040 to the 8030 monitors, and as him I don’t want to go so low.
 
Two or more subs is really about getting a more consistent response at each seat. If you only care about one seat or maybe two if they are close enough and fall in the similar acoustic locations. To get a correct bass response EQ will almost always be needed whether you want one listening position or multiple listening locations. If you only care about one location you can find a good location for the sub and good location for the seat. That location should not have an major dips in response, peaks are OK as they can be EQ'd. Apply your EQ and your done. The problem comes is these locations are not always how we want to set up our room.

Multiple seats are always harder. Ideally you find seating in similar acoustic locations that way EQ works for all of them. As a generalization in a rectangular room avoid seating in the middle or quarter points of any dimension. Also, avoid seating near walls or corners. Seating placement defnitely helps! This is where 2 or more subs helps and takes more time to find good locations and set up properly. However, you can get a similar bass response in the various seats and again EQ will be needed.
Maybe irrational but I never use digital EQs, perhaps with time I will get an Elisya analogue PEQ or something similar.
 
My original question was enough answered and more, thus 2.1 system will have better soundstage than 2.0

I don't think anyone said the soundstage, per se, is better. As @Westsounds said, soundstage is an illusion caused by how a person hears the speakers, their distances to speakers, the mix, and how the speakers reflect off the walls. As the sub is a long wavelength filling the room, I don't think it is part of what one perceives as SS.

You will get more even frequency response and a fuller sound. Subs are usually a much larger driver than a speaker's woofer, which in my opinion, gives a more physical bass. But that's me.

When you cut your speakers at 80-85, or wherever, you free up the speaker response so it has better articulation for the mids as it's not trying to do both bass and mids off one surface. Maybe that makes a better SS? No idea on that.
 
You may want to have a look at actual studies:

 
My living room is 4x3 meters, I think that one will be enough.
I finally keep the 8030s (have both 8020 and 8030 to compare) that fill quite well my room.

As I red in other post, one member also get a nice flat response with adding the 7040 to the 8030 monitors, and as him I don’t want to go so low.
Originally I tuned my system for the Harman curve. The bass was a little heavy for my taste, so I dropped the bass to be about 2 dB lower than the Harman curve. After listening for a couple of months, I find that configuration fine for older recordings, which oftentimes are lacking in bass, but that configuration still is a little bass heavy on newer recordings.

I can save up to 4 DSP configurations on my miniDSP. So, yesterday I started tuning a new configuration with even less bass boost. If I'm listening to an old recording with low bass, I can use the first configuration that has bass boost. I will use the new configuration for newer music that does not need a bass boost.

I will keep listening and adjusting it until I'm satisfied. Anyway, here are measurements I made yesterday at my listening position, which is about 3m from the speakers. The speakers are about 1m from the front wall. The green line is the target curve I set, red is the left channel and blue is the right channel.


Subwoofer Integration.jpg
 
Back
Top Bottom