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"Bass management" in a stereo system. My take.

rwortman

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A short while ago I posted about this not being as necessary as some think and got some vigorous pushback. Here I expound a bit more. If I want to use a subwoofer in my stereo system can I use a simple preamp output to drive the sub or do I need "bass management"?

The answer is it depends. First off what is bass management? In an AVR (Audio Video Receiver) it is twofold. One is sending bass from all channels below their crossover points to the subwoofer. Second is routing all signals from the LFE (low frequency effects) channel to the sub only. In a stereo system bass management simply means a crossover. Some preamp and integrated amp subwoofer outputs have a low pass filter (LPF) for the sub and some have this and a high pass filter (HPF) for the main speakers). Some have a full range jack labelled subwoofer which is a full range signal summed to mono. Others have no sub output at all. All powered subwoofers have their own LPF for their driver and and a few have an HPF built in when one uses the speaker level inputs. Most high quality subs do not have speaker level inputs.

So can I run a full range signal to my sub and run my main speakers with no HPF? Sure I can. My subwoofer already has a built in perfectly good crossover. Also my main speakers are designed to be run full range from whatever amplifier they are connected to. I know of no speakers on the market that the manufacturer recommends they be high pass filtered to play properly.

The usual objection to this is that I will get higher distortion from trying to force the woofers in my main speakers to produce frequencies that they can't. This is mostly nonsense. They were designed to be driven full range. Anyone who has played a warped record with no infrasonic filter can tell you that any woofer is fully capable of moving in a pistonic fashion at 2hz, never mind 20hz. The problem with smallish drivers or those with limited excursion is that they don't make a very loud sound at very low frequencies. They move just fine, they just don't talk very loud. Woofer distortion happens at higher frequencies when the cone begins to break up (flex in an uncontrolled fashion).

Others will talk of intermodulation between the ultra low frequencies and the midbass or midrange (depending on whether you have a two drivers or more) This is already cooked into the design. If you like the way your speakers sound then this distortion source is not causing audible problems.

The final potential issue is blending the response of the sub and the mains in the crossover region. This is usually not a big deal. The natural rolloff of bass SPL due to woofer displacement (combination of area and excursion) is a pretty smooth slope. Adding another slope to this with a HPF is not necessarily going to improve things. I have a mid to low priced sub from SVS that has selectable LPF slopes of 6,12,18, and 24db/octave. I can match the natural rolloff of my Imagine T2's pretty well. If we listened in anechoic chambers, perhaps we would want exact matching of crossover slopes between the mains and subs. We do not and a couple of db hump or dip in the crossover region is going to be swamped by the untidy mess that bass response is in home listening rooms.

I write this as I am about to replace an amp containing DSP that I was using to HPF my main speakers and I am wondering what effects this will have. In real terms, nearly nothing. I will need to tweak the subwoofer setting a bit, that's all. Bottom line is if you are shopping for an integrated amplifier or preamp and plan to use a sub, it's nice to have a jack on the back to connect it to but you don't have to narrow your list to only those that have two way crossovers built in. If your subwoofer doesn't have left and right inputs (many do) you may want to use a summing network to create a mono signal from your preamp/amp. Ideally, you want the output you use to be separately buffered so you don't reduce stereo separation in the main outputs when using a passive summing network. Most, if not all, bass in recordings is already summed to mono at subwoofer frequencies so, although I haven't tried this, you could probably just connect one left or right channel to the sub and never notice the difference.
 
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ernestcarl

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A short while ago I posted about this not being as necessary as some think and got some vigorous pushback. Here I expound a bit more. If I want to use a subwoofer in my stereo system can I use a simple preamp output to drive the sub or do I need "bass management"?

The answer is it depends. First off what is bass management? In an AVR (Audio Video Receiver) it is twofold. One is sending bass from all channels below their crossover points to the subwoofer. Second is routing all signals from the LFE (low frequency effects) channel to the sub only. In a stereo system bass management simply means a crossover. Some preamp and integrated amp subwoofer outputs have a low pass filter (LPF) for the sub and some have this and a high pass filter (HPF) for the main speakers). Some have a full range jack labelled subwoofer which is a full range signal summed to mono. Others have no sub output at all. All powered subwoofers have their own LPF for their driver and and a few have an HPF built in when one uses the speaker level inputs. Most high quality subs do not have speaker level inputs.

So can I run a full range signal to my sub and run my main speakers with no HPF? Sure I can. My subwoofer already has a built in perfectly good crossover. Also my main speakers are designed to be run full range from whatever amplifier they are connected to. I know of no speakers on the market that the manufacturer recommends they be high pass filtered to play properly.

The usual objection to this is that I will get higher distortion from trying to force the woofers in my main speakers to produce frequencies that they can't. This is mostly nonsense. They were designed to be driven full range. Anyone who has played a warped record with no infrasonic filter can tell you that any woofer is fully capable of moving in a pistonic fashion at 2hz, never mind 20hz. The problem with smallish drivers or those with limited excursion is that they don't make a very loud sound at very low frequencies. They move just fine, they just don't talk very loud. Woofer distortion happens at higher frequencies when the cone begins to break up (flex in an uncontrolled fashion).

Others will talk of intermodulation between the ultra low frequencies and the midbass or midrange (depending on whether you have a two drivers or more) This is already cooked into the design. If you like the way your speakers sound then this distortion source is not causing audible problems.

The final potential issue is blending the response of the sub and the mains in the crossover region. This is usually not a big deal. The natural rolloff of bass SPL due to woofer displacement (combination of area and excursion) is a pretty smooth slope. Adding another slope to this with a HPF is not necessarily going to improve things. I have a mid to low priced sub from SVS that has selectable LPF slopes of 6,12,18, and 24db/octave. I can match the natural rolloff of my Imagine T2's pretty well. If we listened in anechoic chambers, perhaps we would want exact matching of crossover slopes between the mains and subs. We do not and a couple of db hump or dip in the crossover region is going to be swamped by the untidy mess that bass response is in home listening rooms.

I write this as I am about to replace an amp containing DSP that I was using to HPF my main speakers and I am wondering what effects this will have. In real terms, nearly nothing. I will need to tweak the subwoofer setting a bit, that's all. Bottom line is if you are shopping for an integrated amplifier or preamp and plan to use a sub, it's nice to have a jack on the back to connect it to but you don't have to narrow your list to only those that have two way crossovers built in. If your subwoofer doesn't have left and right inputs (many do) you may want to use a summing network to create a mono signal from your preamp/amp. Ideally, you want the output you use to be separately buffered so you don't reduce stereo separation in the main outputs when using a passive summing network. Most, if not all, bass in recordings is already summed to mono at subwoofer frequencies so, although I haven't tried this, you could probably just connect one left or right channel to the sub and never notice the difference.

Majority of people here seem to use a mono sub(s) setup. I have no beef with people choosing stereo subs, but I would like to see more multi-position/mic measurements taken throughout a listening room space (not just the MLP) regardless of setup.

I've successfully run all my speakers full-range with a sub, too -- but, it usually is much more complicated to set up, and I found I needed to use mixed phase FIR filters to get the xo slopes and resulting summed responses as best optimized as possible (stereo and multichannel). It's not always so clearly "better" in audible and measurement results, also given the extra DSP and time delay cost incurred. At maximum volume, the smaller satellites might start to compress and distort earlier... esp. if you are applying boosting EQ in there as well.
 
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rwortman

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but I would like to see more multi-position/mic measurements taken throughout a listening room space (not just the MLP) regardless of setup.
I only sit in one place. Attempts to equalize bass response all over the room may be required for home theaters with lots of seating but are meaningless to what it sounds like at a single listening position.
 

Spkrdctr

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A short while ago I posted about this not being as necessary as some think and got some vigorous pushback. Here I expound a bit more. If I want to use a subwoofer in my stereo system can I use a simple preamp output to drive the sub or do I need "bass management"?

The answer is it depends. First off what is bass management? In an AVR (Audio Video Receiver) it is twofold. One is sending bass from all channels below their crossover points to the subwoofer. Second is routing all signals from the LFE (low frequency effects) channel to the sub only. In a stereo system bass management simply means a crossover. Some preamp and integrated amp subwoofer outputs have a low pass filter (LPF) for the sub and some have this and a high pass filter (HPF) for the main speakers). Some have a full range jack labelled subwoofer which is a full range signal summed to mono. Others have no sub output at all. All powered subwoofers have their own LPF for their driver and and a few have an HPF built in when one uses the speaker level inputs. Most high quality subs do not have speaker level inputs.

So can I run a full range signal to my sub and run my main speakers with no HPF? Sure I can. My subwoofer already has a built in perfectly good crossover. Also my main speakers are designed to be run full range from whatever amplifier they are connected to. I know of no speakers on the market that the manufacturer recommends they be high pass filtered to play properly.

The usual objection to this is that I will get higher distortion from trying to force the woofers in my main speakers to produce frequencies that they can't. This is mostly nonsense. They were designed to be driven full range. Anyone who has played a warped record with no infrasonic filter can tell you that any woofer is fully capable of moving in a pistonic fashion at 2hz, never mind 20hz. The problem with smallish drivers or those with limited excursion is that they don't make a very loud sound at very low frequencies. They move just fine, they just don't talk very loud. Woofer distortion happens at higher frequencies when the cone begins to break up (flex in an uncontrolled fashion).

Others will talk of intermodulation between the ultra low frequencies and the midbass or midrange (depending on whether you have a two drivers or more) This is already cooked into the design. If you like the way your speakers sound then this distortion source is not causing audible problems.

The final potential issue is blending the response of the sub and the mains in the crossover region. This is usually not a big deal. The natural rolloff of bass SPL due to woofer displacement (combination of area and excursion) is a pretty smooth slope. Adding another slope to this with a HPF is not necessarily going to improve things. I have a mid to low priced sub from SVS that has selectable LPF slopes of 6,12,18, and 24db/octave. I can match the natural rolloff of my Imagine T2's pretty well. If we listened in anechoic chambers, perhaps we would want exact matching of crossover slopes between the mains and subs. We do not and a couple of db hump or dip in the crossover region is going to be swamped by the untidy mess that bass response is in home listening rooms.

I write this as I am about to replace an amp containing DSP that I was using to HPF my main speakers and I am wondering what effects this will have. In real terms, nearly nothing. I will need to tweak the subwoofer setting a bit, that's all. Bottom line is if you are shopping for an integrated amplifier or preamp and plan to use a sub, it's nice to have a jack on the back to connect it to but you don't have to narrow your list to only those that have two way crossovers built in. If your subwoofer doesn't have left and right inputs (many do) you may want to use a summing network to create a mono signal from your preamp/amp. Ideally, you want the output you use to be separately buffered so you don't reduce stereo separation in the main outputs when using a passive summing network. Most, if not all, bass in recordings is already summed to mono at subwoofer frequencies so, although I haven't tried this, you could probably just connect one left or right channel to the sub and never notice the difference.
I got lost in my own head halfway through your post. So, my question is, are you using an AVR?
 
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rwortman

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I use an AVR in a 5.1 surround system. I also have a two channels stereo system of preamp/amp/speakers. The post was about integrating a sub in a stereo system, which generally does not include an AVR. Your question seems irrelevant.
 
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Spkrdctr

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I use anAVR in a 5.1 surrounds system. I also have a two channels stereo system of preamp/amp/speakers. The post was about integrating a sub in a stereo system, which generally does not include an AVR. Your question seems irrelevant.
My question was a question because I wasn't sure what you were using. Mr. Snippy! Or as my dad used to say "Simmer down"!
 

ernestcarl

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I only sit in one place. Attempts to equalize bass response all over the room may be required for home theaters with lots of seating but are meaningless to what it sounds like at a single listening position.

That is certainly a far easier situation. Though, I do not think it is meaningless to check what is happening beyond one’s own seat or head space — certainly not the whole room anyway, for sure. So, could you show us your before and after results superimposed or overlayed — individual and summed responses; equalized and unequalized? Along with the effects of your equalization as seen in the time domain. I’m simply curious of the objectively measured differences.
 

Kal Rubinson

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I only sit in one place. Attempts to equalize bass response all over the room may be required for home theaters with lots of seating but are meaningless to what it sounds like at a single listening position.
That is certainly a far easier situation. Though, I do not think it is meaningless to check what is happening beyond one’s own seat or head space — certainly not the whole room anyway, for sure. So, could you show us your before and after results superimposed or overlayed — individual and summed responses; equalized and unequalized? Along with the effects of your equalization as seen in the time domain. I’m simply curious of the objectively measured differences.
Other issues are (1) no one listens with their head in a fixed (clamped) position, (2) a single mic cannot be in the same position as both ears and (3) that there can be extremely localized (within a few inches) nulls/peaks. So, even for the solitary listener, measurements spread over a 2 cu.ft. space would be a good idea.
 
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rwortman

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Other issues are (1) no one listens with their head in a fixed (clamped) position, (2) a single mic cannot be in the same position as both ears and (3) that there can be extremely localized (within a few inches) nulls/peaks. So, even for the solitary listener, measurements spread over a 2 cu.ft. space would be a good idea.
Nulls and peaks in the bass region cannot be inches apart. The wavelengths are too long.
 
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rwortman

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My question was a question because I wasn't sure what you were using. Mr. Snippy! Or as my dad used to say "Simmer down"!
I assumed that no one here would use an AVR in at two channel system and the post was about whether what is called “bass management” is necessary to add a sub to a two channel system.
 
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rwortman

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That is certainly a far easier situation. Though, I do not think it is meaningless to check what is happening beyond one’s own seat or head space — certainly not the whole room anyway, for sure. So, could you show us your before and after results superimposed or overlayed — individual and summed responses; equalized and unequalized? Along with the effects of your equalization as seen in the time domain. I’m simply curious of the objectively measured differences.
You can only equalize a system for a specific position. In an auditorium, its necessary to measure around the room to get a decent “average” response for all the seats. For bass in a small home listening room for one listener eq to the listening position is sufficient. Measuring many positions and averaging them will only response at the one position worse. Bass wavelengths are long. Peaks and nulls are not going to be 6 inches apart. Evening out the response for other positions requires multiple sub’s.
 

caught gesture

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It sounds like you have it all thought out with no input needed from other people. I would just enjoy your bass reproduction. You could perhaps provide some measurements for us to look at from your listening position.
 

luft262

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I guess it all depends on your opinion. I'm not convinced that the woofers in the mains won't start outputting some audible distortion. I also am a big fan of DSP and IMHO for optimal stereo sound in basically any room one will need access to DSP so that means an AVR or something like a miniDSP SHD.
 

TheBatsEar

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I guess it all depends on your opinion. I'm not convinced that the woofers in the mains won't start outputting some audible distortion. I also am a big fan of DSP and IMHO for optimal stereo sound in basically any room one will need access to DSP so that means an AVR or something like a miniDSP SHD.
They will output distortion, so? Bit of distortion in the lower frequencies doesn't take the joy from the music.

It's not optimal, clearly. You can get better results with bass management, but you can perfectly fine listen to music without it.
 

luft262

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They will output distortion, so? Bit of distortion in the lower frequencies doesn't take the joy from the music.

It's not optimal, clearly. You can get better results with bass management, but you can perfectly fine listen to music without it.
I agree. I've enjoyed plenty of music on free earbuds too, but if I'm designing a serious system for listening at home I prefer to have bass management.
 

ernestcarl

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Measuring many positions and averaging them will only response at the one position worse.

No need to average if more distant microphone positions are set -- a simple overlay graph would suffice -- but it would be interesting to see how something like UMIK-X would work in that scenario, too.

For example: https://www.audiosciencereview.com/...udyssey-xt32-vs-dirac-live.29890/post-1124745

Some bass loss and off-axis coloration esp. at the more extreme angles... Could also maybe use one or two more additional PEQs... I think. While it's nice to have objectively good results at one MLP, it would be even better if most of the room actually sounded well balanced -- where nothing in particular sticks out too much.

When looking at a group of measurements, and as Kal mentioned, even having the microphone set two feet apart all around would be more informative (either averaged or not) than a single point IR.
 

Putter

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While I disagree with almost everything you say (e.g. distortion from running small speakers doesn't matter, that it's not a good idea to use an AV receiver for stereo, that moving a few feet has no effect on standing waves, etc.) , the proof of the pudding is do you like the results? It almost sounds like you're trying to convince everybody else that you're right and that they're wrong, a fools errand if there ever was one.
 
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rwortman

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While I disagree with almost everything you say (e.g. distortion from running small speakers doesn't matter, that it's not a good idea to use an AV receiver for stereo, that moving a few feet has no effect on standing waves, etc.) , the proof of the pudding is do you like the results? It almost sounds like you're trying to convince everybody else that you're right and that they're wrong, a fools errand if there ever was one.
Most proponents of small monitors love the way they sound. Desiring some more low end would be nice and adding a subwoofer to provide it does not transform them into bad sounding speakers in need of high pass filtering to improve them.

I did not say it wasn‘t a good idea to use an AVR for stereo (although measurements published on this forum might suggest it). I said that since my post was about whether one needed “bass management“ in a stereo integrated amp or preamp if one was planning to use a subwoofer, one should reasonably assume I was not talking about an AVR.

I also never said moving a few feet had no effect on standing waves. I said moving a few inches did cause a significant change in measured or perceived bass standing waves and therefore bass can be effectively equalized for a single listening position. It is not possible for me to miss my chair by a few feet and still be sitting in it.
 
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rwortman

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I guess it all depends on your opinion. I'm not convinced that the woofers in the mains won't start outputting some audible distortion. I also am a big fan of DSP and IMHO for optimal stereo sound in basically any room one will need access to DSP so that means an AVR or something like a miniDSP SHD.
Distortion in the mains will be whatever it was before the subwoofer was introduced to the system. How are the mains going to start distorting more because they noticed another speaker in the room? P.S. The post was about integrating a subwoofer and whether a high pass filter was necessary. It expressed no opinion on the efficacy of EQ to tune a complete system to room it’s in.
 
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