Subwoofer to fix natural roll-off vs to boost all-around bass?

Niber

Standard Member
Around the web (and in my amp manual) I'm told that the ideal subwoofer settings (for stereo music) is to find set the subwoofer to only pickup sound where the speakers roll off. I've tried this and I don't like it:
1) If my sub only starts with freq below 50hz (the rolloff of my speakers), it's not very utilized in most songs. Then the songs turns really boring, I can no longer feel the 808/bassline.
2) so you might think, well THEN if you want more bass you can turn up the bass EQ/boost in the amp. But at the max of 10+db, that's not enough bass.
3) ..and what's worse, that kind of bass boost feels boomy. When I turn up the volume on the sub I'm loving the sound, but turning up the amp bass boost I hate that sound. My theory is that the amp is boosting too high freq of base, tho the manual says "+/- 10dB @ 100Hz" which does sound about right, but I don't know how wide that freq range is.

So in other words, I'm told that the sub should be for fixing the flaws of the speakers, whereas I use the sub for a completely different case, which is something like 120hz and max sub volume.

Song example: at 0:29 in this Avril song the bass line kicks in. On a subwoofer at 160hz this sounds great. But if I turn the sub down to 50hz and instead use the bass boost on the amp to hear that bassline, it sounds super boomy.

Gear:
*2x KEF Q950
*Cambridge ARX100
*1x SVS SB1000 subwoofer
Room: 40sq meters

I used to think that this method of "using the sub to boost all bass" was a necessary evil on low-end system, but if I ever buy a more proper system then you don't need it. But the gear above is my new setup and I find I still need the subwoofer to carry the song.
 

Khazul

Well-known Member
At 50Hz the sub will be quite active usually, however what also often happens is unless the sub is in phase with the main speaker at you listening position, then you may find it is partially cancelling a narrow frequency range (and may be reinforcing others) so you can up with less base above the roll off.

When you change the sub frequency to 160Hz, then likely a different frequency band is getting some partial cancellation and quite likely it is less noticeable.

Try different sub different locations for the sub if you can and try reverse the phase if possible.

BTW - I have a sub that basically just fills in under my main speakers, so my crossover frequency is at 40Hz. It did take quite a bit of fiddling with c/o freq, level and phase and doing measurements using a measuring mic and REW app to get it right.
 
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gava

Well-known Member
Note that you don't have to set the sub crossover at 50Hz, chances are that the speakers aren't really producing very much down there anyway. Try a crossover at 70, 80 or 100Hz. You do sound like you like your bass. From 80Hz down there is very little directional information, which is why it's used as the default crossover frequency. The advantage also is that you will then be likely tightening up the mid-bass on the mains because you are working the mid-woofers less hard, and also you will be giving the amp more headroom.

If you don't have a decent DSP solution in place then I would certainly experiment with using the high level inputs, you should find it easier to blend the signals then. REL has some good youtube videos how to go about this and the principles are equally applicable to your sub. Using high level would also allow you to add a second sub quite easily.

You can then easily use the subs to augment the main speakers and probably get slightly improved time alignment too. There is a lot of back and forth just tweaking the crossover and volume depending on the track you are playing, but over a period of a couple of weeks you will find the right crossover point and sub volume for your general tastes.
 
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Paul7777x

Distinguished Member
You should benefit form using the speaker level inputs on your sub instead of the sub out.

Especially if you’re going to use the sub so high.

The sub out will be summing the bass to mono, which wouldn’t be much of a concern at very low frequencies but certainly will be at 160hz.

Have you a photo of your set up?
 

noiseboy72

Distinguished Member
Just also bear in mind that speaker manufacturers lie a bit, so the "44Hz-28kHz (±3dB)" claim may not be that accurate. You may well find that at the critical 60-90Hz region, the level is still quite a bit down.

It's worth checking that your listening position is not in something of a null, and you are losing some of the critical frequencies due to phase cancellation. Search for "Sub Crawl" for how to locate the optimum position for the sub within your room.

As Prince would have told you, the key bass "punch" frequency is 80Hz. This is what our ears interpret as bass slam, kick, whatever you want to call it. Many mini systems and bluetooth speakers are engineered to have a peak at this frequency to trick the ear into thinking they have plenty of bass, when actually, there's virtually nothing going on lower down. The Linn Kan / LS3/5A is another speaker that uses this trick.

If you want an example of this, then Sk8er Boi by Avril Lavigne has a little easter egg in terms of low bass during the opening section. Try playing the track and see if you can hear the low frequency explosions. Many systems simply can't reproduce it without a decent sub. I'm sat here listening in my office on a pair of £100 JVC active speakers and although they sound reasonably rich and deep, the explosion is totally absent. If I were to play this on my main system, it would be clear as day.

I would not use any form of bass boost, but try a sub roll off at about 120Hz, as this is the limit of source localisation in a typical domestic system. (IE: You will not hear which speaker is creating the bass below this frequency.) Turn up the sub and play with the phase control so that the sub can be heard to be adding energy and getting a bit boomy. Then, back off the sub until you don't think you can hear it any more. Let your ears get accustomed to the sound, then turn the sub off and you will instantly notice the difference. Turn it back on and the sound will start to sound bigger and with more bass, without sounding over blown. You can always give it an extra click or 2 if you feel it needs it.
 

Niber

Standard Member
Just also bear in mind that speaker manufacturers lie a bit, so the "44Hz-28kHz (±3dB)" claim may not be that accurate. You may well find that at the critical 60-90Hz region, the level is still quite a bit down.

It's worth checking that your listening position is not in something of a null, and you are losing some of the critical frequencies due to phase cancellation. Search for "Sub Crawl" for how to locate the optimum position for the sub within your room.

As Prince would have told you, the key bass "punch" frequency is 80Hz. This is what our ears interpret as bass slam, kick, whatever you want to call it. Many mini systems and bluetooth speakers are engineered to have a peak at this frequency to trick the ear into thinking they have plenty of bass, when actually, there's virtually nothing going on lower down. The Linn Kan / LS3/5A is another speaker that uses this trick.

If you want an example of this, then Sk8er Boi by Avril Lavigne has a little easter egg in terms of low bass during the opening section. Try playing the track and see if you can hear the low frequency explosions. Many systems simply can't reproduce it without a decent sub. I'm sat here listening in my office on a pair of £100 JVC active speakers and although they sound reasonably rich and deep, the explosion is totally absent. If I were to play this on my main system, it would be clear as day.

I would not use any form of bass boost, but try a sub roll off at about 120Hz, as this is the limit of source localisation in a typical domestic system. (IE: You will not hear which speaker is creating the bass below this frequency.) Turn up the sub and play with the phase control so that the sub can be heard to be adding energy and getting a bit boomy. Then, back off the sub until you don't think you can hear it any more. Let your ears get accustomed to the sound, then turn the sub off and you will instantly notice the difference. Turn it back on and the sound will start to sound bigger and with more bass, without sounding over blown. You can always give it an extra click or 2 if you feel it needs it.
I couldn't hear any explosion sound either on my system, I assume you mean when the spray cans are dropped in the beginning intro
 

Niber

Standard Member
Note that you don't have to set the sub crossover at 50Hz, chances are that the speakers aren't really producing very much down there anyway. Try a crossover at 70, 80 or 100Hz. You do sound like you like your bass. From 80Hz down there is very little directional information, which is why it's used as the default crossover frequency. The advantage also is that you will then be likely tightening up the mid-bass on the mains because you are working the mid-woofers less hard, and also you will be giving the amp more headroom.

If you don't have a decent DSP solution in place then I would certainly experiment with using the high level inputs, you should find it easier to blend the signals then. REL has some good youtube videos how to go about this and the principles are equally applicable to your sub. Using high level would also allow you to add a second sub quite easily.

You can then easily use the subs to augment the main speakers and probably get slightly improved time alignment too. There is a lot of back and forth just tweaking the crossover and volume depending on the track you are playing, but over a period of a couple of weeks you will find the right crossover point and sub volume for your general tastes.
I'm not sure what you mean, the Cambridge AXR100 doesn't have any sort of bass management, so the sub frequency settings doesn't releave the speakers.
And the SB1000 sub only has high-level IN, not out, so I guess that means that it too doesn't have any bass management, it cannot limit the deep frequencies from reaching the speakers.
 

Niber

Standard Member
You should benefit form using the speaker level inputs on your sub instead of the sub out.

Especially if you’re going to use the sub so high.

The sub out will be summing the bass to mono, which wouldn’t be much of a concern at very low frequencies but certainly will be at 160hz.

Have you a photo of your set up?
Cool, I'll be doing that then (you might have seen my separate thread about that).
I'm currently renovating my studio room, so I just have my setup in the living room right now to test things out so I know how to make the room, So the setup is very ugly right now, and both the subs and speakers are so near me that I'm definitely risking phase issues
 

noiseboy72

Distinguished Member
I couldn't hear any explosion sound either on my system, I assume you mean when the spray cans are dropped in the beginning intro
I'm not sure if a Youtube video is your best music source for this! You can certainly hear it even on the low resolution Spotify stream. Listen at the end of the drum phrases after the initial guitar riff and just as the vocals start.

Despite this being a truly average track in all other respects, it's a good one for tripping up the audiophiles who don't think that subs can add anything to their floor standing stereo systems!
 

Flobs

Active Member
I would start with speaker placement. My thinking is that you have your stereo speakers positioned to boost bass and not giving them breathing space. For example perhaps you have even placed one of your speakers where the sub should be. Of course if this is the case you'd have quite nasty muddled sound so see if by moving your stereo speakers around they give clearer sound with greater precission and clarity (sound faster).

Would help if you could post some pictures and a diagram with some simple measures (room length width and height, speaker positions from side and back/front wall (wall behind speakers).

I have little experience with subs I've got acheap thing plugged to my tv and get reasonable results with it and did have a 5.1 system once, the sub did it's job in 5.1 but in 2.1 was disagreeable at higher volumes as my front speakers were not well positioned in that set up (for films it was ok boomy and fun)).
 

Flobs

Active Member
it's a good one for tripping up the audiophiles who don't think that subs can add anything to their floor standing stereo systems!
I think there are some speakers that adding a sub might be a silly idea, I haven't the experience to say for sure, but some PMC's, Spendors, Proacs and Neats and my dream speaker the Davis Karla go soo low that adding a sub would appear to just be an idea to muddle and mess up the sound.
Otherwise yes I'm getting some speakers that go down to 40Hz +/- 1.5 or 3dBs or what ever. I'll see if I feel they would benifit from a sub (I think they will). It's ineresting how different speakers sound what I have at the moment suddenly cut off on Sk8ter boi and you know your missing something where as another pair I have there's a more gradual drop off and if you haven't heard that track through some PMC 25 24i's or with a sub you wouldn't know any better. (particularly if you have said speakers set too close to the wall behind them).
 

gava

Well-known Member
I'm not sure what you mean, the Cambridge AXR100 doesn't have any sort of bass management, so the sub frequency settings doesn't releave the speakers.
And the SB1000 sub only has high-level IN, not out, so I guess that means that it too doesn't have any bass management, it cannot limit the deep frequencies from reaching the speakers.

Yikes. You are correct. I wasn't even aware that such a thing existed.

Sub out on the AXR100 has a 200Hz low pass filter so you need to blend everything on the sub. Hmm, that really makes it a moot point whether you use the high level/speaker inputs on the sub then. You could use them if you got an extra sub.

I guess you will have to do as much as you can with speaker/sub positioning then.

Also I suppose you could try to use the tone controls to turn your bass down a bit and let the sub take more of the overall responsibility for bass.
 

Niber

Standard Member
Yikes. You are correct. I wasn't even aware that such a thing existed.

Sub out on the AXR100 has a 200Hz low pass filter so you need to blend everything on the sub. Hmm, that really makes it a moot point whether you use the high level/speaker inputs on the sub then. You could use them if you got an extra sub.

I guess you will have to do as much as you can with speaker/sub positioning then.

Also I suppose you could try to use the tone controls to turn your bass down a bit and let the sub take more of the overall responsibility for bass.
It's weird, it must be a stereo-hifi thing, because yesterday I decided I've had it with the Cambridge Audio (I really don't like this brand for many reasons) so I ordered a Rotel RA-1572MKII to replace it. Quite a bit more expensive so should be a bump up in quality, however even the Rotel also doesn't have bass management which is a little ridiculous.
 

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