Bass: the final frontier?

[StanleyB]

Is the reproduction of low bass digital audio signals still left to be conquered? The reason I ask this is because of some observations I stumbled upon by accident. Maybe it was more a case of not having paid particular attention to them previously. Let me outline the case.

For those of us with an amplifier with inbuilt phono preamp and subsonic filter, it's not uncommon that we would flick the subsonic switch when the bass starts ringing or becomes boomy. More often than not, we would assume it is signal feedback that is upsetting the cartridge to speaker path. I know from the aftermarket phono preamps that I have had a look at that the subsonic filter is already inside the phono amp stage signal path, and fixed. i.e. you can't switch it in or out.

In the case of digitized audio files subsonic filters are not used (but not necessarily not required. That's another point for discussion I would say.), thus allowing for your equipment to go down as low as it technically can.
But one observation that I did make, which subsequently became more obvious when other people also mentioned it in passing was the question of bass reproduction. And in particular the reproduction from subwoofers, directly powered or not. I noticed that no matter whose place I visited, if they had a subwoofer in their system and switched on, the subwoofer seemed a bit out of pace with the bass from the other speakers. This situation got even worse if the source/amp/speakers and source material had a good attacking style/capability.

My own NS1000M has a -3dB drop off in bass below 40Hz (if I remember the specs correctly), so I use a subwoofer to augment anything lower in the audio spectrum. It can't however keep up with the pace of the NS1000M.
I also have a pair of Thiel CS2.2. These have a passive radiator. The passive action of the radiator is also not capable of keeping up with the bass of the active bass speaker right above it. On searching the net I did come across an article where the reviewer of a CS2.2 also made mention of this fact.

However! When I played the track from "Pete Namlook - The Flight" I noticed something else. The subwoofer did not seem to exhibit any noticeable slow pace in its reproduction.
I have been trying to analyze the ins and outs of that, and the reason for it. My conclusion so far is because the track has so little in terms of high frequency notes and is not very attacking in style, the subwoofer is capable of keeping up with the pace of the music.

But things do not stop there.
When trying out a couple of amps, and using just the NS100M ( in order to eliminate the problems with the passive radiators form the CS2.2), the faster amps were able to produce a far better sound from bass heavy audio files, even if most or all of the low bass was not clearly audible or of a similar playback level through the speakers when comparing signals via a simple spectrum analyzer.

This has got me thinking about whether bass speakers and subwoofers designs have kept pace (sic) with the quality and speed of the bass that started appearing with the advent of digital audio. In the old analogue equipment days that kind of bass was not a regular feature found cut onto vinyl. One reason was obviously the damage that it could inflict on cartridges and the grooves of a vinyl record.

What do you guys think?

[Reffc]

Hi Stanley

I think you may be confusing things using phrases such as "faster" amps and comparing digital V's analogue for bass performance.

The reason that many subs in systems seem to lag behind has more to do with phase alignment and the power being fed to them. Low notes take a lot of current. Your observation regarding fast and slow amps or speakers with "pace and attack" has little to do with the bass being somehow left behind. It comes down to an amplifier's ability to control the bass and this is everything to do with the quality of regulated power supplies, damping factors and overall power to drive the bass, be that a subwoofer or two channel stereo.

Where subs are added its usually beneficial to bi-amp so that the sub has its own power source.

Room treatment also counts for some of what you say. Subs or ordinary speakers placed too close to walls, especially with no acoustic treatment, couple to the walls and the result can be bass-boom which can muddy the bass notes and make them appear to lag behind everything else.

As far as analogue goes, there's no reason whatsoever that a good cartridge cannot plumb to 20 Hz or lower. A decent turntable, properly set up run through a quality phonostage should have no problems whatsoever delivering clean bass down to 20Hz. If it can't and there's distortion then chances are its one or a combination of things like poor cart/arm match (compliance matching issues), poor cart alignment, or something wrong with the phonostage.

Before drawing conclusions though, its best to first check that your amplifier has the control and damping factor to manage low bass control and extension (speaker/amp match), that you're not coupling speakers to the walls by having them too close (acoustic treatment and bass traps help enormously), and that for analogue, you have an appropriate cart/arm match and a decent phonostage. With those things in place, much of what you say should cease to become an issue.

[StanleyB]

Did I mention my turntable at any point :scratch:?

[Reffc]

Did I mention my turntable at any point :scratch:?

err

"we would assume it is signal feedback that is upsetting the cartridge to speaker path. I know from the aftermarket phono preamps that I have had a look at that the subsonic filter is already inside the phono amp stage signal path, and fixed. i.e. you can't switch it in or out. "

Don't think I pointed a finger to your personal TT set up, just addressed the comments you made.

[MartinT]

I used to run a pair of JM Lab Mezzo Utopias (medium floor-standing speakers with an 11" sandwich woofer) together with a REL Studio II (twin 10" Volt woofers). This combination went seriously deep and sounded pretty harmonious but the bass wasn't particularly fast. It sounded fantastic with classical music but very slightly ponderous with rock music.

My current setup uses Usher Be-20 large floorstanders with twin 11" Eton drivers and no subwoofer. Although their ability to go deep is no better or worse than the REL sub, they do sound considerably faster with more impact with both rock and classical music.

So I guess I'm agreeing with you that subs can be a problem to integrate with the main speakers for best bass performance.

[Stratmangler]

Toppsy's Edingdales do bass and are remarkably fast.
This is down to them being two way speakers, with the four main drivers being series/parallel wired.

[anthonyTD]

I think Paul has made some realy good points,
I used to build sound systems for cars many years ago, and we used to split the frequencies up into three stages, ie; high, middle and bass, all active with their own individual active cross-over networks, and as paul has explained, it is/was very difficult to intergrate the low bass frequencies with the rest due partly to the enviroment [cars are not paticularly audio friendly] and also mainly down to the current availability to produce the energy needed, of course things have moved on considerably since i last did anything in car systems, but i think my point is still valid, i too have heard systems in other peoples home's that use sub bass systems of mediocre quality, and i can identify the subs within the music as like Stan has pointed out, Also, the bass is set up in a lot of these systems that use subs in such a way that the bass is always way too prominent and therefore unatural to listen to for any length of time, for me anyway.
A...

[electric beach]

the bass is set up in a lot of these systems that use subs in such a way that the bass is always way too prominent and therefore unatural to listen to for any length of time, for me anyway.
A...

I had read advice/ experience that horn loaded wide range drivers need the sub crossed over high, about 100-120. I worked with this and tuned the cabinet damping accordingly, but despite using DSP I was constantly revising ther sub's volume for the varying amount of bass on different recordings and music types. I then reduced the crossover filter to about 60-70 and retuned the cabinets, since when I've hardly touched it. Much easier and better integration and Valerie commented "now everything sounds good", meaning not only recordings that suited the sub volume at that time. The DSP is still doing it's magic on the room modes and acoustic bass has become a living, breathing, tonally rich and fascinating instrument, while Rock has bass that is driving the pace. There are a few albums where the bass seems overblown but I think that's where it's been artificially boosted in the upper bass intentionally for commercial reasons.

[anthonyTD]

I had read advice/ experience that horn loaded wide range drivers need the sub crossed over high, about 100-120. I worked with this and tuned the cabinet damping accordingly, but despite using DSP I was constantly revising ther sub's volume for the varying amount of bass on different recordings and music types. I then reduced the crossover filter to about 60-70 and retuned the cabinets, since when I've hardly touched it. Much easier and better integration and Valerie commented "now everything sounds good", meaning not only recordings that suited the sub volume at that time. The DSP is still doing it's magic on the room modes and acoustic bass has become a living, breathing, tonally rich and fascinating instrument, while Rock has bass that is driving the pace. There are a few albums where the bass seems overblown but I think that's where it's been artificially boosted in the upper bass intentionally for commercial reasons.

Thats interesting Steve,
And i am absolutely sure that well designed/sorted active subs can work when intergrated properly, you seem to have found a satifactory way of getting the best out those in your system, and thats always good to hear.:)
Anthony,TD...

[DSJR]

I don't mean to create waves here, but as far as vinyl is concerned, many "commercial grade" LP's have the bass mono'd and rolled away below 30Hz or so, especially the DMM cuts which sacrifice bass extension and level to get a better treble clarity..

As for bass quality in general, I feel currently that what "we" regard as trouser-flapping bass is actually 60Hz to say 120Hz, since very deep bass below 40Hz is felt rather than heard, if you see what I mean.

In the case of subs, I'm well out of date on this, but one thing I can still say - there are "subs" and there are SUBS... One type is basically a low frequency boom-box with no definition at all. REL made these at one time, usually the cheaper ones although a £3K KEF Reference cupboard sized thing we tried some years ago now was truly horrendous on a musical signal/synth bass etc...

Interestingly, the best "sounding" subs weren't necessarily the biggest ones, many, such as the two smallest M&K ones from yesteryear in very old fashioned looking boxes (one was model "somethingorother 70" as I recall) actually did a fantastic job on music, gently augmenting the lowest notes but never dominating or slowing them down with time-delay or phase issues - trying to describe what we hear is fraught with danger and easy to mis-interpret, as Marco and I have found often ;)

You know, and don't beat me up here, one of the better modern subs could well be the AVI one. The bass driver is a 10" with huge throw and magnet, driven by a powerful amp claimed to be around 200W or so (so over 100W in everyone elses power terms :eyebrows:). It's fully adjustable for rolloff and level and the huge magnet should give excellent control and damping. The box looks similar to other subs I've seen (possibly a modern REL one) and apparently LS Designs in Sth Wales make part or most of it, as well as the REL models I understand.

One final thing about subs - USE TWO!!!!! I was brought to believe that two sources of low bass actually drives room modes better and more evenly, but more importantly, two wired in proper stereo, and even set very low, can reproduce reverb and acoustic better than one alone, which can cancel out certain aspects of "air and space" in a well recorded venue. That's from a recording engineer pal of mine, by the way.

Hope this helps a bit and doesn't ruffle any feathers :)

[anthonyTD]

I don't mean to create waves here, but as far as vinyl is concerned, many "commercial grade" LP's have the bass mono'd and rolled away below 30Hz or so, especially the DMM cuts which sacrifice bass extension and level to get a better treble clarity..


As for bass quality in general, I feel currently that what "we" regard as trouser-flapping bass is actually 60Hz to say 120Hz, since very deep bass below 40Hz is felt rather than heard, if you see what I mean.

In the case of subs, I'm well out of date on this, but one thing I can still say - there are "subs" and there are SUBS... One type is basically a low frequency boom-box with no definition at all.
REL made these at one time, usually the cheaper ones although a £3K KEF Reference cupboard sized thing we tried some years ago now was truly horrendous on a musical signal/synth bass etc...

Interestingly, the best "sounding" subs weren't necessarily the biggest ones, many, such as the two smallest M&K ones from yesteryear in very old fashioned looking boxes (one was model "somethingorother 70" as I recall) actually did a fantastic job on music, gently augmenting the lowest notes but never dominating or slowing them down with time-delay or phase issues - trying to describe what we hear is fraught with danger and easy to mis-interpret, as Marco and I have found often ;)

You know, and don't beat me up here, one of the better modern subs could well be the AVI one. The bass driver is a 10" with huge throw and magnet, driven by a powerful amp claimed to be around 200W or so (so over 100W in everyone elses power terms :eyebrows:). It's fully adjustable for rolloff and level and the huge magnet should give excellent control and damping. The box looks similar to other subs I've seen (possibly a modern REL one) and apparently LS Designs in Sth Wales make part or most of it, as well as the REL models I understand.


One final thing about subs - USE TWO!!!!! I was brought to believe that two sources of low bass actually drives room modes better and more evenly, but more importantly, two wired in proper stereo, and even set very low, can reproduce reverb and acoustic better than one alone, which can cancel out certain aspects of "air and space" in a well recorded venue. That's from a recording engineer pal of mine, by the way.

Hope this helps a bit and doesn't ruffle any feathers :)

Totaly agree with the hilighted parts Dave.
Anthony,TD...

[John]

When setting up I would use fast tabla combined with drums and deep bass I would first adjust phase then xover to work well using active bass, having DSP allows me to taylor the sound a bit further so far I am liking the results

[Reid Malenfant]

The problem is down to the speakers being used - simple as!

With a sealed box there is very little group delay between upper bass notes & bass notes below where the system response is rolloing off. If you happened to add a Linkwitz/Riley transform any remaining (which is tiny with a sealed box) group delay would vanish.

Any reflex speaker has a hell of a lot of group delay, this gets worse with high Q enclosures & it also worsens the deeper the enclosure is tuned to in the audio band.

What group delay does is effectively delay the starting & stopping of a deep bass waveform in comparison to an upper bass waveform. So the two are out of time & things appear to be so & if you like it sounds slow when delivering deep bass.

The amplifier will only affect the damping applied to the driver, though it will tend to make matters sound worse than they really are if it has loose cotrol of the bass cone & voicecoil.

The NS1000M will sound fast as it has bugger all group delay.

Get yourself a free program called winISD & try it out for yourself. Model the NS1000M bass driver (if you need the specs I have them as I measured them many moons ago) & drop it into a sealed box & a reflex & look at the difference. Don't forget it's a low Q driver, which should give any amp better control as well.

The only solution with a reflex speaker is to tune it so low that in the audio band there is no more real group delay than with a sealed box. That involves tuning to about 10 - 12Hz though.

An ABR is similar, though unlike a reflex port there is a second mechanical resonance to take into account. No-one apears to have sussed out how to get the same performance as a reflex but with an ABR. Well I'll tell you - you need to make an ABR with an incredibly low free air resonance & a very high compliance equivalent volume.

If you do that then the mechanical resonances of the ABR can be discounted, simply because they are so far below the tuned frequency in the enclosure (rather than just under it) that it'll behave just like a reflex & the ABR will start & stop with far less overhang due to interference from mechanical resonances...


That's it, I have said my bit :)

[MartinT]

I don't mean to create waves here

:rfl:

[f1eng]

I don't mean to create waves here, but as far as vinyl is concerned, many "commercial grade" LP's have the bass mono'd and rolled away below 30Hz or so, especially the DMM cuts which sacrifice bass extension and level to get a better treble clarity..

As for bass quality in general, I feel currently that what "we" regard as trouser-flapping bass is actually 60Hz to say 120Hz, since very deep bass below 40Hz is felt rather than heard, if you see what I mean.


It is not only commercial grade LPs that have bass mono'd it is a requirement of the lp stereo system. Since each channel is cut at 45 degrees a bass signal in only one channel would soon results in the cutter leaving the surface of the laquer, so can't be done. Mono bass is inherent in the lp system.

Also I don't agree with you as to where bass starts to be felt rather than heard. The lowest note on our piano (a Steinway model B) is 29.13 Hz and is easily heard and not yet felt. The local church organ goes to 16 Hz, I believe, and that can not be heard (by me) but can be felt, so IME the transition is likely to be nearer 20 to 25 Hz than 40Hz. It is true the lowest note on a standard 4 string Bass guitar is 40 Hz though.
Accurate bass is very difficult to achieve, but worth it IMO, I have put a lot of effort into it here! The speakers make a big difference but good speakers only need to be slightly out of the ideal position in the room for it all to go wrong. There is no way of avoiding this, though room treatment can help damp the room modes it is better to position the speakers to minimise exciting them. The overiding factor is the position of the speaker in the room, and the optimum depends on the type of speaker ie a dipole like an electrostatic drives the room differently to a cone in a box.
The listening position also effects the bass quite a lot.
There are specialists who can model a room and predict good starting points to place speakers.

[Reid Malenfant]

Ok, time to illustrate my point with a few known drivers :)

Yellow trace = Yamaha NS1000M driver in a stock 50L closed box.

Red trace = Yamaha NS1000M driver in a 99L -6dB extended bass shelf bass reflex alignment.

Purple trace = Yamaha NS1000M driver in 24.1L QB3 bass reflex alignment.

Green trace = Tannoy Monitor Gold 15" in a 100L closed box.

Light blue trace = Tannoy MG 15" in a 197.7L -6dB extended bass shelf bass reflex alignment.

Dark blue trace = Tannoy MG 15" in a 47.1L QB3 bass reflex alignment.

Gold Trace = CSS SDX15 in a 150L 11Hz tuned bass reflex.



As you can see with the first graph which is of group delay, the sealed boxes have the least amount of group delay. Next up are the small QB3 bass reflex enclosures which tend to have a low enclosure Q. Put the same drivers into EBS6 enclosures which have a much higher Q & the group delay increases markedly, but only at deep bass frequencies. So it sounds disjointed & maybe out of time with the upper bass. Or as Stan says, slow...

With that 11Hz tuned SDX the group delay in the audio band is lower than just about everything except the closed boxes. This is simply because the effects of the port don't start coming in until around double the port frequency or about 22Hz. So it will sound like a sealed box in the audio band.

Admittedly there is quite a bit of group delay at about 10Hz, but you're only going to feel that anyway. The important bit is what you can hear :)

Group delay. The left hand columb of the graph is delay in milliseconds.

http://i939.photobucket.com/albums/ad240/speakermark/subwoofer/groupdelay.jpg

Transfer function magnitude.

http://i939.photobucket.com/albums/ad240/speakermark/subwoofer/transferfunctionmagnitude.jpg

Maximum sound pressure level for one driver in the enclosures used above.

http://i939.photobucket.com/albums/ad240/speakermark/subwoofer/maximumspl.jpg

[StanleyB]

Those are some interesting graphs. I am not into speaker building anymore, but the modelling software does look good.

[DSJR]

Also I don't agree with you as to where bass starts to be felt rather than heard.

No probs, but please remember that a piano tone is FULL of harmonics, so the lowest note you hear may well be the harmonics primarily I think. maybe those old big IMF's I revered back in the day were playing 20Hz or below on the DSOTM master copy we had :lol:

Try this link to some sub tests -

http://www.hometheatershack.com/forums/subwoofer-tests-archived/6015-index-subwoofer-tests-manufacturer-model.html

I appreciate the tests were done outdoors and a room will significantly alter the plots, but what concerns me on many of the subs I've looked at here, is that the high-pass filtering does seem too gentle and there seems to be a noticable output at 100Hz which "could" explain the issues Stan is having with his NS1000's. Maybe if he organised a steeper rollout on the sub?

[StanleyB]

I appreciate the tests were done outdoors and a room will significantly alter the plots, but what concerns me on many of the subs I've looked at here, is that the high-pass filtering does seem too gentle and there seems to be a noticable output at 100Hz which "could" explain the issues Stan is having with his NS1000's. Maybe if he organised a steeper rollout on the sub?
I am not having any issues with my NS1000's :). I merely used them as a reference example in the thread.

[Clive]

I appreciate the tests were done outdoors and a room will significantly alter the plots, but what concerns me on many of the subs I've looked at here, is that the high-pass filtering does seem too gentle and there seems to be a noticable output at 100Hz which "could" explain the issues Stan is having with his NS1000's. Maybe if he organised a steeper rollout on the sub?
Many subs have a gentle roll-off, without the mains on you can usually picky some vocals from the subs.....

There are 2 reasons for their being setup this way:

1) typically gentle filters ring less

2) integration issues are reduced

12db/octave roll-off is quite common followed I believe by 18db. DSP driven filters tend to offer 12db and 24 db - maybe DSP filters ring less?

[DSJR]

I was thinking of Stan's comments about his subs "slowing" the bass of his Yamaha's down, that's all. An active high pass shouldn't "ring" either methinks.

[f1eng]

No probs, but please remember that a piano tone is FULL of harmonics, so the lowest note you hear may well be the harmonics primarily I think. maybe those old big IMF's I revered back in the day were playing 20Hz or below on the DSOTM master copy we had :lol:


I had to wait for my wife to finish playing it :-) but I just played the lowest octaves on the piano to see if the fundamental seems less loud as frequency goes down. As you say there are a lot of harmonics, as with most percussion instruments, but I would say subjectively that I am hearing the fundamental down to the 29Hz.
Interesting reading about the subs. I bust a gut getting my speakers positioned such that the bass FR was fairly even. I don't have the heart to spend all that time/effort integrating a sub too.

The -3dB point of my speakers is 26Hz and in room the FR is good down to 20Hz (the lowest tone on my test disc) so a sub won't add much.

[electric beach]

By happy coincidence or lucky intuition - it's certainly not technical knowledge :lol: - it's piano that I've mainly used as the final arbiter to judge when the sub settings sound right, not an electric or acoustic bass line.

[MartinT]

The -3dB point of my speakers is 26Hz and in room the FR is good down to 20Hz (the lowest tone on my test disc) so a sub won't add much.

My in-room response is flat down to 18Hz, explaining why I sold my REL sub on.