Stereo sub bass myth or reality?

[herki the cat]

People are told that bass is omnidirectional so it doesn't matter where you put the sub woofer. I totally disagree with that!But most people don't have $$$ or the floor space . jcrobso

herki's two cents:
Mono bass below 100Hz traditionally happens at the LP record mastering stag by eliminating the "vertical component" of the 45/45 degree stereo modulation to reduce the groove modulation width. This procedure is required in order to achieve a full 17 minuets of program per side of the 12 inch LP record.

I don't think digital recording has this problem since the pulse track width is very narrow, & the available recording time per side of digital recordings is more than adequate, especially for classical music.

Recorded bass acoustic image retrieval, as the listener moves away from the speakers, has more to do with the struggle between the modest, home-accoustical environment, low frequency modes ringing excessively during the short duration time of the recorded bass signal components.

Recorded bass-image reproduction requires a superb room equivalent to the mastering engneer's room.
I just any other way .

[Ruediger]

People are told that bass is omnidirectional so it doesn't matter where you put the sub woofer. I totally disagree with that!

In a room the placement determines which room modes get excited, and how much. So the placement determines how much bass You hear at which frequency.

But You should not be able to determine where the sub is located.

Unless the crossover frequency is too high and/or the sub produces heavy distortions (harmonics at higher frequencies).

Ruediger

[herki the cat]

In a room the placement determines which room modes get excited, and how much. So the placement determines how much bass You hear at which frequency.

But You should not be able to determine where the sub is located.

Unless the crossover frequency is too high and/or the sub produces heavy distortions (harmonics at higher frequencies).

Ruediger

herki:
Bass imaging also depends on the "group Delay" quality of the loud speakers, which is not snake oil, but simply the quality of phase linearity & phase disrortion in all signal transmission media such as sound, light, & video which was carefully addressed by RCA, Ampex, & the rest of the TV Broadcast industry more than 50 years ago at the beginning of TV Broadcasting, especially in the Color TV Broadcast Studio Recorders.

This includes low frquency loud speakers which are inherently very poor, not to mention speaker cables. Yes Verginia, speaker wires of excellent entry-level performance quality are available in the price range of $50 to $100 from MIT Inc. who own all of the important cable patents in the world . Take care, there are many junk quality cables out there dressed up in gorgous plastic jackets with fantastic claims.

JBL already has already addressed group delay in the new superb studio monitor speaker performance specifications, and they have published the results.

Some ten years ago I heard an excellent speaker system at the "Overature Audio" dealer in Wilmington, Delaware driven by a $100,000 Single Ended " Audio Note Inc.," Amplifier of a Double Bass That sounded precisely like that musician was standing three feet from me. It could not sound more real from a live performer. You could hear the sound coming from each individual finger & string including the original recorded live room reverberation sound components generated by the musician in the recording studio. Since i was listening in the near field of that speaker, there was no listening room reverberation sound to contend with.

Simply stated__ Excellent Natural Original Musician's Bass Sound requires retrieving all the original recording environment sound components intact , aka studio reverberation sound with excellent phase linearity and very low phase distortion all the way to your ears.

[JBL 4645]

People are told that bass is omnidirectional so it doesn't matter where you put the sub woofer. I totally disagree with that!

I agree it is omni directional.

But depending on how well its balanced over the sofa area (from side to middle to the other side on the sofa) while turning your head around on some low, sine wave tones, the frequency becomes undone as uniform tone it tends to wonder forwards because its slightly greater a few inches forward depending on frequency and that tends to give it.

Listen on headphones and the tone is stable it doesn't wonder all over the place with dips peaks and nulls.

But most people don't have $$$ or the floor space to multiple subs and they just do with what they have. Did I mention that I hate HTIB!!!

Yes your right, most don’t, have the room to swing a cat around, no offence Sooty.

The only costly part is the amplifiers because you can’t do it with single amp and EQ each sub. Well maybe not impossible, just a bit of waste of time, you want do right.

When I converted from stereo to 5.0 surround I didn't use a sub. Since my mains are JBL loaded "K" horns and my surrounds are JBL88 novas I run them all as full range, only the center is setup as small.
I do like hearing bass from the rear channels when it's in the soundtrack, instead of coming from a front sub.

And (stereo surrounds) is stereo also so stereo sub bass for the surrounds! Yeah, but rarely does the surrounds go down to 20Hz very rare. But you might as well have matching subs all around the room?

Stack them up on top of each other so the lows on the floor cover a few db greater and the one above covers the tones in some parts marginally different and the sub on top of that, same again. Maybe direct forward facing subs standing 5 feet high so when your standing up the tone is at ear level in kinder way.

So that’s 5 subs standing up (you know the 12” cube box size) unless the box the a bit larger, might be 15” so three at the most, for each side of the rear.

The ideal would be that all of the speakers would be full range with a sub.
How many times has JBL4645 show us low bass in the center and rear channels, that just gets shoved to the one lonely sub.

You mean the frequency waterfall graphs.

And the person set his sub behind the couch it becomes useless.
Oh well, so much for my rant!

Well only useless at certain frequencies and the sub as to be resting tightly against the spine on the centre back of the sofa, (otherwise it won’t vibrate as much with less power!)

Other tones will be diminished and would need to be boasted up a bit (a few db).

And, Who says that that sub as to be visible? Why not cut holes in the floor or place a new flooring down with holes cut to fit multiples of 12” and keep them flush with the flooring and place metal grill over them.

Underneath might have to be cleaned out and skimmed and carpeted or absorbent underneath. I would imagine a wondrous loving feeling vibration and the subs facing upwards might have different tonal sound?

Yeah I’ve seen the Donna sub bass made out of bricks and placed in the cellar, with flooring covering it, very impressive.

http://www.royaldevice.com/custom.htm

[JBL 4645]

In a room the placement determines which room modes get excited, and how much. So the placement determines how much bass You hear at which frequency.

But You should not be able to determine where the sub is located.

Unless the crossover frequency is too high and/or the sub produces heavy distortions (harmonics at higher frequencies).

Ruediger

Like standing seating in the middle the tone at certain frequency/frequencies will sound less than they do around the sides in room.

Each room is a real pig’s ear, to sort out.

Only if it’s played that loud! Yeah I’ve heard it doesn’t sound nice.

When, I travel on the bus once in while, the humming low end engine sound is uniform up and down the length of the bus. Now play a single tone in the home from one location and the tone wonders up and down depending on the frequency.

Playing a sine wave 20Hz and walking around the room and the rooms length, the 20Hz only varied -2db to 2db.

Playing 30Hz again walking around the tone dropped down at the front by many db but was greater at the back of the room to a few feet forwards.

Playing 40Hz the tone is fine at the back and partly forwards from the back wall towards the centre/middle of the room the tone drops down and its greater at the front.

Playing 50Hz the tone wonders down in the centre/middle of the room and its greater at the front and rear.

Playing 60Hz the tone wonders up and down its greater at the front and around some areas of the rear but in the middle it’s a bit of an issue and tones where they sound weak leads one to turning up the level and reducing the amps headroom, well in my opinion yes.

So subs all around and played at different levels or EQ for different levels so the tone has less tenancy to wonder, up and down.

The tones at 20Hz may only sound good enough with the sub placed to the furthest distance from the seating or against the wall where it seems greater.

20Hz towards the back of the room tends to be less (I’ve had the sub placed at the back before.) Least in the middle the further corner distance to sofa is within the 20Hz, I’m not moving humping the JBL sub around at this time.

Near towards the door which is open its not as great.

In fact the 20Hz sounds deeper in the bathroom great if you’re playing with toy submarine in the bath. seriously (the tone is ear bending in the bathroom) due to wavelength of the tone.

If I close the door in the bathroom the tone vanishes!

The same tone can’t make it around living room into the bedroom, other tones yes. Same goes for the kitchen and in the middle of the hallway between the living room and bathroom the tone is like in large dip.

[herki the cat]

Like standing seating in the middle, the tone at certain frequencies will sound less than they do around the sides in a room. Each room is a real pig’s ear, to sort out. Only if it’s played that loud! Yeah I’ve heard it doesn’t sound nice. play a single tone in the home from one location and the tone wonders up and down depending on the frequency. Playing 50Hz, the tone wonders down in the centre/middle of the room and it is greater at the front and rear with ubs all around played at different levels, the tone has less tenancy to wonder, up and down...etc... JBL 4645

herki's two cents:
Well ok, I , except that real bass stereo reproduction requires the technology to retrieve all the orignal recording studio reverberation sound components__ free of " phase shift distortion plus excellent phase shift linearity" collectively known as "Group Delay." BTW, bass loud speakers inherently have pitifully very poor Group Delay capability. Group Delay is not Snake Oil. Good frequency response of bass loud speakers is a given.

JBL engineering people are well aware of Group Delay & have addressed the problem in JBL'S preminium monitors. The bass imaging you would percieve standing precisely at the position of a recording-studio stereo microphone facing the recording artist depends on the system Group Delay. Sound from artists located away from the microphone will contain a higher ratio of room reverberation-to-direct sound from the artist.

However in most cases it is very difficult to achieve a good loudness balance amongst several artists, and the recording engineer will use multiple microphones, each microphone close-spaced to each artist, and the engineer will ride gain on each artist's microphone. In this case, usually there is very little room sound collected from that studio room, and modern machine-generated reverberation is mixed in prior to the mastering procedure.

The resulting image is not very good. There are many propriatary tricks used in recording studios. Generally, simply stretching out the the intended make-up reverberation sound duration with delays does produce a very nice tone. A little bit of this goes a long way & usually the wrong way, and the live-directional quality of the image is not there.

Phase distortion and phase non-linearity takes its toll.

You can go to Wikipedia Free Dictionary and learn all about Group Delay in low frequency speakers....Highly recommended.

[Allanvh5150]

I find that the main issue with dertermining if sub bass is directional or not is the fact that the speed of sound is far from constant. Test a sub in an anechoic chamber and you can see the group delay and so on. Put the sub into a room and you have the sub bass coming at you direct from the cone at the speed of sound but you also have it comming at you through the walls and floor where it will reach you about 5 times faster than from he cone. Hence it is near impossible to tell where sub frequncies are coming from.

Allan.

[JBL 4645]

herki

Wow not much there to read.
http://en.wikipedia.org/wiki/Group_d...nd_phase_delay

So in nutshell the tones mentioned
Frequency (Threshold)

500 Hz (3.2 ms)

1 kHz (2 ms)

2 kHz (1 ms)

4 kHz (1.5 ms)

8 kHz (2 ms)

How is it corrected what product is going to correct the, delay after or before, arriving at the ear.

[JBL 4645]

I find that the main issue with dertermining if sub bass is directional or not is the fact that the speed of sound is far from constant. Test a sub in an anechoic chamber and you can see the group delay and so on. Put the sub into a room and you have the sub bass coming at you direct from the cone at the speed of sound but you also have it comming at you through the walls and floor where it will reach you about 5 times faster than from he cone. Hence it is near impossible to tell where sub frequncies are coming from.

Allan.

From the cone you say. What about having the subs sealed inside box and port hole facing the sides of the listeners ears. noticed that the tone producing from the vented box when stuffed up lowers the SPL db as well other issues like cone movement.

But lets not worry the tone coming from the port has different tone and higher pitched lows don’t blow out wads of air turbulence which mostly starts from 0Hz to about 60Hz where it starts dropping away.

Also the tones will blow a wind like sound around the ears but not enough and not even natural enough like in the real world with soft summer breeze blowing against your skin at all angles.

There isn’t one film I’ve heard or felt where it has wind like breeze effect that presses on me, gently, softly and smoothly. I think that is one thing for film can’t do, instead they give us “Twister” (1996) with loud effects and even the loud effects that pressed on your body, but didn’t feel real enough with softer wind sound effects, or what is on the soundtrack that, creates creditable realism (at any level), oh it was exciting it its day.

Music doesn’t really blow on your body and you go to live orchestra its mostly vibrations you might feel but strings horns and tympani doesn’t blow on your body like a…

What’s the name of that instrument called wood wind? That’s pipe yeah, so if, one was standing in front of it would you not feel some blowing like air from the tubes end?

I know that is an unusual place to listen to it from, a flute that would blow a wind like sound. There are just some things that blow on you, LOL LOL and some that don’t, oh, no that come out right. Blow on you. LOL

I haven’t yet tried with the spectrumlab to measure wind what frequency is gently wind breeze? Wait a second! I’m going to try a basic experiment by blowing on the SPL db metre and measure the frequency that will give me some idea.

[JBL 4645]

That didn’t take much to blow on the SPL db metre. I had the range set to 100dbc. It would uncomfortable if you did that down someone’s ear, and expect to get punched in the face for everything there is an opposite reaction.

Nice and warm in the 50Hz to 75Hz range blowing vertically

The horizontally graph not as much then again blowing against a microphone creates a rumble rustle like, horrible sound normally.

Anyway it was just test to satisfy my curiosity.

Blowing on my hand at different distances and you soon run out of steam to produce a natural tone like in real life. I doubt that rotary sub bass can do that without producing some audible motor sound/noise after all its just a fan, and fans produce motor noise, wind produces what it has done for billions of years a natural all around blowing effect.

For a sub to produce a blowing air like sound that sounds real, I don’t think its possible it would take so many subs and I doubt Danley could do it at natural levels.

Now if I hold a DVD case in front my month and blow the air is bounced off and I feel it on the chest and that sounds or if I stuck ear plugs in my ears…lets try that!

Now I can hear the blowing sound without the ear plugs that sounds (narrow).

Umm interesting! It sounds even more narrower and sounds central to my nose or (in-head sound).

Wow I’m out of breath now. LOL I need a cream soda! Ahhh yes that hits the spot!

In have pc fan in the cupboard and small DC voltage regulator I’m going to try another test with spectrumlab.

I can hear the tinnitus hissy sound I’ve had it all day long! I had lapse from it, (early yesterday).

[JBL 4645]

Now that is with the SPL db set at 80dbc with the fan at 12volt speed and held above the SPL db by 8 inches, I moved the fan around the SPL db from horizontal to vertical.

Even with ear plugs I can still hear it at 12 inches away the motor noise that is.

The wind like sound, I feel it, I can hear a wind low end very gently.

Remove the ear plug and held in same position the wind blowing down the ear feels (mildly) uncomfortable.

Small pc fan running at 12 volt speed blowing on the SPL db metre! Now that is quite some low for small pc fan, if only I more of them!

I tried the fan resting underneath the sofa foot, not much I could sense (just tiny motion) Now if I remove a few blades I would be able to feel a vibration.

I have another pc fan around somewhere that has a few blades broken off that will produce a low end vibration.

A little pink in the 42.5Hz range.

[JBL 4645]

Found this rather interesting a bit hard to grasp. Meditate on it I will. Yeah I’ll read this though a few times it looks interesting.

Subject: Discussion of Group Delay in Loudspeakers
http://www.trueaudio.com/post_010.htm

[JBL 4645]

Just give, me the answer to it like how does one measure the (group delay) and what is used to tame it, to control it, that’s all, just a simple answer.

It’s hot and it’s too early in the morning to read, white papers.

I would soon touch cheap loudspeaker cables even if I was millionaire I’d still buy cheap cable.

If I thought I could rub Vaseline on sting I’d use that to power the loudspeakers.

[herki the cat]

herki, Wow not much there to read. For what its worth,
http://en.wikipedia.org/wiki/group delay & phase_delay?......How is it corrected; what product is going to correct the delay after or before arriving at the ear.

herki: (up grade of the post)

Scrole down & navigate into the various white papers by audio professionals who understand low frequency speakers, " phase shift distortion & phase none-linearity" aka: the context of "Group Delay" deep down in the Wikipedia profile on Group Delay. Read and study this stuff carefully.

There is no way to correct damaged Sound Group Delay after the fact; it is much easier to prevent this problem, at least in speaker cables & interconnets by proper design than it is dealing with the complicated low frequency speaker issue compounded by speaker enclosure artifacts.

With listening room acoustic artifacts, Group Delay becomes extremely complicated if not impossible to manage. Room acoustic design is critical, and well supported in this industry.

Group Delay damage results in changing the velocity of sound propogation of electrical signals and light waves in a manner proportional to spectrum pitch or frequency.

This is the case, be it via a cable, or a speaker, or via air, or motion in water, or any other medium including sound through a, 2 x 4 chunk of lumber, or a railroad steel rail, & especially, light waves passing through any medium with non-parrallel boundary surfaces, like a prisim or a lense where you can push the Group Delay around to your heart's content.
JBL 4645

I did not invent speaker cables, and I am not pushing speaker cables or MIT Interface Technologies. Cables are not for everybody. They do not fix anything except transmission of the audio signal. Every thing else in the system has be first class electronics.

For those who are interested in cables, MR Bruce Brisson, CEO of MIT Interface Technologies owns 100% of the worlds most Imortant Cable Patents, and he uses a Special HP Inc., Spectrum Analyser that reads propogation velocity __the heart of the Group Delay issue__in electrical hardware from vertually DC out to 1,000 Mhz & especially-well from 1Hz to 100,000 Hz for audio. MIT Inc., is capable seeing electrical function in their product design with incredible ease.

We had these instruments in RCA Camden, Nj. With this instrument & a professional microphone, you can tell what the low frequency speakers or any part of the system is doing. This instrument is a companion adjunt to the General Radio inc "Tone Burst Generator" Technology addressed in an other "herki the cat" post.

For what its worth, Mr Brisson describes in his patents with great detail, why the aweful, High Frequency Noise, & Phase Distortion & Phase None-Linearity of ordinary lamp-cord speaker wire and other conductors physically happen to sound like Gruesome, Cheap Transistor Amplifier Distortion.

Simply stated, "phase distortion & phase none-linearity occurs in any conductor including heavy guage, low resistance, configurations due to the fact "that as the audio signal frequency "decends in frequency," the magnetic field surrounding the conductor moves in towards the center of the conductor in a manner "inversly proportional to frequency of the signal." This function is not the common "skin effect" of Radio Frequency Transmission and Litz wire does nothing to fix the audio problem.

Perhaps a flexible hollow pipe? Almost, but not good enough for the long haul. Polk Inc.,originally had a plastic pipe with both "send and recieve polarity conductors" criss-crossing each other which did present considerable improvement, but it suffered from extremely high capacitance and amplifier instability.

Brisson's cable approach began with a "wire construction" around an insulaton material core, using multiple pitched, spiral-wraped windings of various guage copper wires in a group like a conentric overlayed assembly of door springs of progressively increaseing number of winding turns. This resulted in a cable construction of multiple paralleled
inductors each with consecutive increasing inductive reactance value according to wire gauge and winding turns to progressively delay the audio signal in a manner inversely prortional to frequency down to at least 100 Hz presenting considerable quality down through the entire critical mid bass spectrum.

Brisson has invented additional patented technology to function from 100Hz down to 10 Hz.

For readers who are interested, Mr. Brisson teaches in his patents how his cables are engineered and built with enough detail you can duplicate his product construction.

Very good entry level cables priced $50 to $100, and very low cost DIY-MIT Kitsare sold in the HI End Audio stores.

[JBL 4645]

The white paper link epic fail to open up on the pdf file, Now I’m really pissed off!

No just a simple answer to the solution I don’t want yellow pages that is one mile thick! Just a simple layman’s answer, so I can get on with it.