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

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rwortman

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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.
More informative? I guess. Ultimately I am going to be sitting in one spot. What it sounds like somewhere else doesn’t change what I hear. If I am not using those other measurements to make EQ decisions, what are they good for? If I am using them, then I must be deviating from whatever my ideal curve is at the listening position. Look, I have done this both ways. For live sound reinforcement in a large room, I take multiple measurements to get an EQ compromise. Then I play music I am familiar with and walk all around the room. The goal is as good as possible sound for everyone. In my home room, the goal is to get it as close to perfect as possible for just me. What’s going on a few feet away doesn’t matter. If my head has moved two feet, I fell out of my chair. Wavelength at 100hz is nearly 12 feet. Bass nulls are not going to be inches apart, or even two feet apart.
 

Prana Ferox

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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).

This isn't quite right. More specifically:

Speakers can be damaged thermally or mechanically. To damage them thermally you need to overdrive them, usually for extended periods of time. The limiting component can vary (woofer, tweeter, crossover) but generally this limit is pretty high and you generally have to be audibly abusing the speaker (and/or clipping the amp) to get there. In general this is a drunken-party problem. This is why speaker manufacturers can usually spec pretty ridiculous power ratings for their speakers without worry.

Mechanical damage is another matter. A ported speaker's power handling curve slopes downward below tuning frequency and overpowering it can audibly bang moving parts of the driver against fixed parts, or damage the coil. You may get audible distortion before you hit a mechanical limit - but if you have a subwoofer playing much louder in that frequency range (which is kind of the point), you may not hear it. The wattage (voltage, really, this isn't an over-time thing) to cause damage can be far, far below the speaker's power rating. You can also put an impressive amount of power into a driver at low frequency without realizing it simply because these lower frequencies are harder to hear. That's why those infrasonic / rumble filters exist, because a cruddy 12" can actually cause damage. Sealed speakers don't unload the same but given enough voltage you can still damage them.

This is all volume knob dependent and if you never crank it you may never reach a power handling limit, but generally adding subwoofers is not the action of the listener who likes it quiet. Thus, if you high pass your mains, odds are you can play your mains and your sub louder, without breaking something.
 

TheBatsEar

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This is all volume knob dependent and if you never crank it you may never reach a power handling limit, but generally adding subwoofers is not the action of the listener who likes it quiet.
I agree with everything you wrote, but this. If you take music serious, chances are you want to scrape every last obscure wave of those CDs. My Focal 826V are pretty much full size, yet their F6 is only 37Hz. I say almost everyone needs a sub, they just don't know it yet.

Thus, if you high pass your mains, odds are you can play your mains and your sub louder, without breaking something.
No doubt, high pass helps with that.
 
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rwortman

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This is all volume knob dependent and if you never crank it you may never reach a power handling limit, but generally adding subwoofers is not the action of the listener who likes it quiet. Thus, if you high pass your mains, odds are you can play your mains and your sub louder, without breaking something.
True enough. My post was not aimed at speaker survival for headbangers. It addressed whether one can achieve good main/sub sound without a crossover in your amp/preamp. I can already achieve completely ridiculous SPL out of my main speakers. I never assumed that the main use of a sub was to play everything louder. I am not really convinced that it is.
 

ernestcarl

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In my home room, the goal is to get it as close to perfect as possible for just me.

It seems you have already achieved the goal you set out to accomplish, other than the upgrade that's yet to come. I'm glad to hear that.

Do you mind at least showing us what "close to perfect" looks like?
 

Actungz

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I thought bass management meant/included applying EQ to the bass region as well, since low frequencies interact with the room much more and EQing down the peaks can prevent the bass from sounding muddy.

Let’s just say you had a large boost at 50hz from your sub and full range speakers, wouldn’t you want to bass manage that?
 
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rwortman

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I thought bass management meant/included applying EQ to the bass region as well, since low frequencies interact with the room much more and EQing down the peaks can prevent the bass from sounding muddy.

Let’s just say you had a large boost at 50hz from your sub and full range speakers, wouldn’t you want to bass manage that?
The original question was whether you need a two way crossover in a preamp or integrated amp to get good performamce from a sub. Crossover and EQ are related but not the same. Bass management in most preamps and integrateds simply means either a low pass for the sub which is absolutely not needed because the sub has one and maybe a high pass for the mains which can be handy, but isn’t mandatory. Even in an AVR bass management does not mean EQ, thats a different function.
 
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Spkrdctr

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Basically no, you do not need Bass Management. Just add a sub to your stereo speakers and adjust your sub accordingly with its onboard capabilities. Quite a few posts were generated though. Let us know what sub you end up with. Thanks!
 

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If you look at the distortion of speakers, most have 10 times more below 80hz. If you remove those freq. you remove that distortion. (a sub should have less distortion below 80hz than the mains). So HPF on the mains will reduce distortion, (not just doppler),and will greatly ease the load on the amp (lots of power below 80hz).
 
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rwortman

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If you look at the distortion of speakers, most have 10 times more below 80hz. If you remove those freq. you remove that distortion. (a sub should have less distortion below 80hz than the mains). So HPF on the mains will reduce distortion, (not just doppler),and will greatly ease the load on the amp (lots of power below 80hz).
That’s all true. However, if you like the sound of your speakers before you add the sub, this distortion in the low bass must not really be that audible.
 

waynel

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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.
Most small speakers are ported and while the amplitude of the bass may roll off smoothly , in general the phase does not. Therefore the main speakers will be changing phase relative the the subs in the region of overlap and this will cause an uneven combined amplitude response . This is the main reason bass management is needed. If you measure you should be able to see this effect and while it’s possible to partially correct this with dsp , I have found it much easier to achieve a smooth bass response when starting with a proper crossover.
 

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That’s all true. However, if you like the sound of your speakers before you add the sub, this distortion in the low bass must not really be that audible.
The problem is not with the low bass distortion. The problem is with the (intermodulation) distortions of the mid/lower-mid/upper-bass riding on the low bass that requires high excursions from the driver.

Distortions skyrocket with driver excursions (see Klippel nonlinearity poster, link below). The 250 Hz part of the signal distorts a lot more if it is produced when the cone is near +xmax or -xmax, if it is riding on top of a large amplitude 40 Hz component. Without having to reproduce low bass which demands high excursions, the driver can reproduce much cleaner mid/lower-mid/upper-bass.
 
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rwortman

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Most small speakers are ported and while the amplitude of the bass may roll off smoothly , in general the phase does not. Therefore the main speakers will be changing phase relative the the subs in the region of overlap and this will cause an uneven combined amplitude response . This is the main reason bass management is needed. If you measure you should be able to see this effect and while it’s possible to partially correct this with dsp , I have found it much easier to achieve a smooth bass response when starting with a proper crossover.
I am not sure this is true. The phase of the actual woofer doesn’t change, the output of the port does and its phase is frequency dependent. At what point does this phase top changing? Are you saying you high pass the main speakers at a point where the port has no output? In any case I didn’t say having a two way crossover wasn’t easier, just not mandatory. i.e If you are eyeballing a preamp or integrated that doesn’t have an HPF you don’t need to let that stop you from buying it.
 

waynel

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I am not sure this is true. The phase of the actual woofer doesn’t change, the output of the port does and its phase is frequency dependent. At what point does this phase top changing? Are you saying you high pass the main speakers at a point where the port has no output? In any case I didn’t say having a two way crossover wasn’t easier, just not mandatory. i.e If you are eyeballing a preamp or integrated that doesn’t have an HPF you don’t need to let that stop you from buying it.
It’s true and easily measurable. I recommend ideally setting the crossover point to an octave above the natural roll off or as high as possible without the sub being noticeable (I use 80 hz for all my systems .
 
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rwortman

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The problem is not with the low bass distortion. The problem is with the (intermodulation) distortions of the mid/lower-mid/upper-bass riding on the low bass that requires high excursions from the driver.

Distortions skyrocket with driver excursions (see Klippel nonlinearity poster, link below). The 250 Hz part of the signal distorts a lot more if it is produced when the cone is near +xmax or -xmax, if it is riding on top of a large amplitude 40 Hz component. Without having to reproduce low bass which demands high excursions, the driver can reproduce much cleaner mid/lower-mid/upper-bass.
Once again, these distortions don’t occur because you bought a subwoofer. They are cooked into the design of the speakers. If this distortion was a big problem, why are so many people enthralled with the sound of two way monitors? Yes, high passing your main speakers will probably effect the distortion profile. But if you already like the way they sound it can’t be that big of an audible problem, If you are adding the sub to a system with three way mains, even less of s problem.
 
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rwortman

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It’s true and easily measurable. I recommend ideally setting the crossover point to an octave above the natural roll off or as high as possible without the sub being noticeable (I use 80 hz for all my systems .
So your port isn’t putting out any output above 80hz?
 

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Once again, these distortions don’t occur because you bought a subwoofer. They are cooked into the design of the speakers. If this distortion was a big problem, why are so many people enthralled with the sound of two way monitors? Yes, high passing your main speakers will probably effect the distortion profile. But if you already like the way they sound it can’t be that big of an audible problem, If you are adding the sub to a system with three way mains, even less of s problem.
Perhaps they don't know any better.
 

NTK

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Really? People like the sound of two way monitors because of ignorance.
One of the slides from Dr Griesinger.

griesinger.png
 
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