98 replies to this topic

[Banned.ScrewYouTeam.inc]

that has no relevance to what we are discussing.

[Luke352]

that has no relevance to what we are discussing.

What doesn't?

[~thematt~]

That Basil guy (Carni5064), seems like a clever kid.

[br85]

you are doubling the power too.

It's not an issue though because when the signal is put through one input channel, it's still only half of what level the signal will be when the signal is put through BOTH input channels. Therefore, that part of it REALLY doesn't matter.

if you're running two woofers in parallel, you're doubling the cone area, and power, over running a single woofer off the same amp, because you're halving the impedance, and ANY music that has ANY differences between left and right channels at bass frequencies will.

You're failing to take into account the relative difference though. Take a simple scenario where a 20hz signal at 1v runs through a single input (say left channel), followed by a 20hz 1v signal through BOTH inputs:

In stereo mode (1 woofer playing each channel), the first note will be played through a single woofer, at say 80db. The second note will be played through both left and right woofers, at 86db. (assuming perfect phase coherence.) This is the way it's MEANT to be played back (although, like i've said, find a recording where this is an issue). The difference between the first and second signal is 6db.

In bridged mono mode (both woofers playing both channels), the first signal will be played through both woofers, at 86db (+3db for doubling of cone area playing the signal, +3db because you've hooked the woofers up in parallel), the second signal will be played through both woofers also, but at 89db since the power has doubled from 1v on one input to 1v on EACH input (total 2v, doubling of power adds 3db). The difference between the first and second signals is 3db.

the solution is to run a bridged 2 channel amp to a single sub, running stereo, or run separate channels to each sub.

Que?

Edited by br85, 13 September 2010 - 09:57 PM.

[Banned.ScrewYouTeam.inc]

[quote name='br85' date='13 September 2010 - 09:26 PM' timestamp='1284378971' post='1202589']
It's not an issue though because when the signal is put through one input channel, it's still only half of what level the signal will be when the signal is put through BOTH input channels. Therefore, that part of it REALLY doesn't matter.

no, thats the thing... IT ISN"T!

thats my whole point!

go out to your car, play a 50Hz tone, fade from left to right, as if there were bass in the music through only one channel, the level won't change, but it should be 6dB down when faded fully left, or right!

this is the point I've been trying to make all along.

[broadz]

It sounds like all you are describing is simple RCA voltage increasing/decreasing from having one RCA at 5 volts to having two RCA's at 5 volts each. The additional voltage will give more gain and therefore be louder as described.

Nothing really to do with stereo.

[Banned.ScrewYouTeam.inc]

it doesn't give any gain. Thats the whole point. The two monoblocks i've looked at basically connect the left and right rca channels in parallel. This doesn't give a voltage increase.

[Marc ♫]

Step outside and breathe some fresh air VLOUD.

[Banned.ScrewYouTeam.inc]

i stepped outside and listened to my car stereo and found that fading to the left or right didn't drop 6db off the bass like it should to be true to source,

[br85]

no, thats the thing... IT ISN"T!

thats my whole point!

go out to your car, play a 50Hz tone, fade from left to right, as if there were bass in the music through only one channel, the level won't change, but it should be 6dB down when faded fully left, or right!

I can't "fade" per se with my headunit, but if I turn off the left channel, I lose 3db of sub bass and 4-5db of everything else. Get a better HU or amplifier, whichever is causing dramas.


Seriously 2db @ sub bass frequencies is harder to pick than you'd think. The vibration is definitely stronger, but your ears aren't very sensitive to it. 1db difference @ 5Khz is more obvious than 4db difference @ 50hz, so I seriously don't care. Also, just one example of a song where this is an issue and I might give it some more thought.

[ss-rotel]

ok, one thing i think needs to be touched on, and i REALLY didn't read EVERYTHING in each post so dont flame me, but you need to think about harmonics, standing waves, wave fronts, and phase/harmonic distortion.

you're running 2 subs, and you wonder why it sounds loader/better? chance are you've landed on a harmonic peak @ the driving possition. ... so @ a specific freq, 2x in phase sound waves, combine, forming a crest. envision the ripples in a pond. with the right setup, you can get a crest to peak in certain possitions in a car.
(a car is the WORST place to build a stereo. lots of odd panels, reflectin and obsorbing sound waves, stuff like that.)

Obviously, the other side of the coin, you can tune in harmic troughs, almost like having a speaker out of phase.

Personally, out of all the cars i've had, my N14 puslar had the best accoustics, and my current 2005 Jazz has the worst. I've spent more on this car's audio then any other car i've owned to get the same results. (and there's been a few)

a REALLY neat trick in SPL is to focus the crest in the area that the mic is placed, (last time i did this, it was in the middle of the dash, about 4inchs above it), and you can gain multiple DB. by ear, one nite @ a SPL comp, i gained almost an extra 5db in a mates system, by changing the possition of one of his subs. Enough to win the nite anyway.

I think this is what Vloud is experiencing, not that his system's subs are playing in stereo.


The ear shouldn't be able to locate were sub base frequensies are. you can detect amplitude, so you'll be able to work out were it's coming from, cos it's louder over there. to a point. @ a certain DB, you dont some much hear, but fell the sound


Also, using time alignment, you can delay the sound wave from the front drivers to reach you @ the same time as the subwoofer's wave front, and you can get the illusion that the subs @ the front of the car.

the perfect system should only "miss" the subwoofer once it's turned off, not sound like there's a subwoofer

[br85]

you dont some much hear, but fell the sound

Thank you so much for my new signature. Love it.

[SQXPRT]

...Also, just one example of a song where this is an issue and I might give it some more thought.

Colours (Flying - Alpine Track 6)
Anything with a double bass
anything with a tight kick drum

[Banned.ScrewYouTeam.inc]

I can't "fade" per se with my headunit, but if I turn off the left channel, I lose 3db of sub bass and 4-5db of everything else. Get a better HU or amplifier, whichever is causing dramas.

how can you not fade and what amplifier are you running?

[~Spyne~]

eclipse cd7200 won't fade in 3-way mode
though you can adjust the gain on individual channels

[br85]

how can you not fade and what amplifier are you running?

I'm running 3 DPX2251 amps (2 channels on each sub, 1 channel on each midbass) and a JL 300/4 on the mids/highs.

I've also discovered today that I can fade on my P90 headunit but it's exactly the same as if I drop one channel out.

Colours (Flying - Alpine Track 6)
Anything with a double bass
anything with a tight kick drum

Why are tight kick drums or double basses more likely to be in a single (left or right) channel than anything else?

[Banned.ScrewYouTeam.inc]

I'm running 3 DPX2251 amps (2 channels on each sub, 1 channel on each midbass) and a JL 300/4 on the mids/highs.

I've also discovered today that I can fade on my P90 headunit but it's exactly the same as if I drop one channel out.

ah, I was talking about monoblocks here...

your results have proven exactly what I said, that you need to run separate channels to each sub, either as a multiple channel amp, or multiple monoblocks.

I dont know of any monoblock that will combine the signal in any way that will result in the outcome you've found.

[tornaido_3927]

i'm just wondering how you are 'seeing' that the subbass channels in your music are recorded in separate left/right?
if you're looking at a cd track on audacity or some other software, all you're seeing is the left and right channel of the whole recording...

Not sure what you mean by the whole recording, but I use Wavepad which shows me a FFT of the track/s.

FWIW I've attached an image of FFTs of 3 songs, seems like music with more "real" instruments has separate L/R bass (except when they have a bass sweep or something similar edited in) whereas pop music and music with synthetic bass lines are totally mono.

Muzzy I'm pretty sure you have probably experimented more with this than I have but I have had a little toy around with my subs running in two separate channels, with separate channels of amplification. I can also notice a difference and I do enjoy the sound moreso Makes me glad I also ended up with a HXD2 to play with!
And I am not talking about it just being louder because of a crest or peak in the response.

Also, ss-rotel, I don't think you're discussing the same thing we are here, regardless of where a sub is placed or whatever, or even if there is only one sub, the fact that it is only playing one channel of information makes a difference.........................To me

Might be worth noting, I am not talking about actual stereo subbass, rather 2 channel subbass, and I am not talking about being able to localize where the sub/s are either.

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[SQXPRT]

Why are tight kick drums or double basses more likely to be in a single (left or right) channel than anything else?

In a "standard" jazz band (as per my article) the double bass is often back and to the right of centre stage (stage left), and the drums back left or centre.
Some tracks, such as "Sweet Georgia Brown" from "The Ultimate Demonstration Disc" has 2 drum kits and two basses, one "set" either side at stage rear.

[Matt VIP]

I have never been to a jazz band and seen two drum kits and two bass players, let alone at opposite sides of the stage...

why would they do that for a recording?

[SQXPRT]

why would they do that for a recording?

It's a "play-off" I guess?

very dynamic

[br85]

More to the point, who listens to that stuff in their car anyway?

There are SO many phase and time problems in bass reproduction in a car that this entire thread is next to pointless.

You know when you see your rear vision mirror shake that your roof, windscreen and mirror itself are all playing sub-bass, and RETARDEDLY late, right?

You know that very rarely do you have enough midbass output capability to keep up with a sub at the crossover point, right?

You know that a pressure zone like a car has a snowflake's chance of accurately reproducing low bass, right?

Bigger fish to fry, honestly.

[SQXPRT]

br85

I don't think you've heard a good sounding car system.

Most of us who compete in MEASQ, IASCA, EMMA, etc. have these problems, and we find ways to minimise the audible effects of the problems.
Rather than just getting on the internet and complaining about "how hard it is to do a car stereo", we just keep working at it until we're happy or bored.

You're right though, a car will never be a lounge room or a stadium hall, but we know that. It's not a telephone box either.
There is a whole branch of acoustics dedicated to "small listening rooms", and ways to combat the inherent problems that are presented, and ways to improve system design accordingly.

Methinks it's time to go grow a couple and do something.

(no offence intended, but I try to make a point)

Edited by Pulse-R, 18 September 2010 - 12:08 AM.

[Luke352]

br85

I don't think you've heard a good sounding car system.

Most of us who compete in MEASQ, IASCA, EMMA, etc. have these problems, and we find ways to minimise the audible effects of the problems.
Rather than just getting on the internet and complaining about "how hard it is to do a car stereo", we just keep working at it until we're happy or bored.

I've judged Jeff's (br85) car several times now and it has never left me dissapointed and he also tries many things that most people (myself included) put in the too hard basket. So I don't think this is a case of it being too hard for him too try, if Jeff could see the benefit or the physics saying there will be any difference he'd try it.

[muzzy66]

There is a potential 3db in efficiency gain in running a mono signal to 2 woofers (not 6db, to get the 6db figure you need to double the power as well) when it's only meant to be playing though 1. Name an example of some program material this is going to be a problem with, though.

I was going to say this also - same power, but doubling of cone area should provide a 3dB gain.

I have found this to be the case with my own playings around - when switching from mono to stereo setting (using a single woofer) I have had to increase gain on the sub by +3.5dB to get subbass level back up to where it was. I defiantely haven't had to increase it by +6dB, that would be extremely overpowering.

Note that this is also with a single sub running - add a second sub and I'd most likely gain about 3dB, which should about neutralise the difference.

P.s.
From what I can see, people here are talking about running a stereo signal into a pair of subs, but then running them off a single channel amp (monoblock) and wiring them in parallel - what the heck would be the point of this??

The whole idea of stereo is that the left and right speaker recieve different information to one another. What's the point in running a stereo setting if you are still sending the same output signal to both woofers? I'm of the impression that the only possible way to benefit from stereo with multiple woofers would be if you actually have two different speakers with each recieving an unique/individual input (L and R respectively) from a multi-channel amp.

[~thematt~]

I'm of the impression that the only possible way to benefit from stereo with multiple woofers would be if you actually have two different speakers with each recieving an unique/individual input (L and R respectively) from a multi-channel amp.

You really dont pay any attention to anything other people have said, do you?

"You cant learn anything by talking, sometimes you just need to listen"

[SQXPRT]

I've judged Jeff's (br85) car several times now and it has never left me dissapointed and he also tries many things that most people (myself included) put in the too hard basket. So I don't think this is a case of it being too hard for him too try, if Jeff could see the benefit or the physics saying there will be any difference he'd try it.

fair point.

but sometimes physics is only 1/4 of the answer.

there's also psychoacoustic, physiological and behavioural contexts.

i.e. people with thicker legs block the sound from low-mounted speakers, but may be used to that from their own experience.

[Banned.ScrewYouTeam.inc]

give up "thematt"

when people make reference to "stereo" in this thread, they aren't talking about a stereoscopic effect, they are talking about differences in left and right channels,

if you haven't worked that out yet, then it seems you're the one paying no attention.

[SQXPRT]

on the topic of the seeming 3dB loss when switching to stereo mode, some amplifiers automatically have 1/2 the output in stereo mode, as they are running common mode (2-channels) instead of differential mode (bridged) on the input circuit.. this is a design 'anomaly' in the amplifier's input stage.

[muzzy66]

FWIW I've attached an image of FFTs of 3 songs, seems like music with more "real" instruments has separate L/R bass (except when they have a bass sweep or something similar edited in) whereas pop music and music with synthetic bass lines are totally mono.

This is actually pretty interesting, because this is the same conclusion I came to myself from subjective listening as well. Some songs I can hear the difference more then others, and it tends to be the 'real' music in which it's most noticable.

Muzzy I'm pretty sure you have probably experimented more with this than I have but I have had a little toy around with my subs running in two separate channels, with separate channels of amplification. I can also notice a difference and I do enjoy the sound moreso Makes me glad I also ended up with a HXD2 to play with!
And I am not talking about it just being louder because of a crest or peak in the response.

Good that another person has noticed this

As everyone here would know by now I am no non-believer when it comes to theory. Hell, every system or system change I've developed over the last 4 or 5 years have been planned almost purely via theory. Still, when push comes to shove I do like to do some real world listening as well just to make sure that theory did work...in the inperfect world we live in, there are never guarantees.

I think that one issue here is that most (if not all) of the people here who are arguing that you can't hear the difference have never actually bothered to try it for themselves. I get the impression that they look at the theory and say "this is BS, law of physics X proves that this won't make a diffefence" and so rather then try it for themselves they shrug it off as pointless and argue to the death about it with anyone who tries to suggest otherwise.

I'm a theory person, and in theory it really shouldn't sound better - but I've played with it here and there on different system configurations, in different cars (the mx5, and the laser before it) and in all cases I have found that I was able to hear a difference, and that I did prefer it when set to stereo.
If others have tried it and not heard a diffeence, then that's fine. Maybe their systems aren't revealing enough to notice, maybe their mind isn't as focussed to listening, maybe my rickety 20 year old cars have just produced more rattles and reflctions then other cars and that has exchagerated the results...I don't know why it is, but I can hear the difference. A relatively subtle different mind you, but still noticable enough to make it worth my time.
[/img]

More to the point, who listens to that stuff in their car anyway?

Nice concept there - don't bother changing a system to make it more accurate, just avoid any listening material that might bring out the flaws...because what you don't know can't hurt you, right?

There are SO many phase and time problems in bass reproduction in a car that this entire thread is next to pointless.

Bigger fish to fry, honestly.

Again, great concept - a car environment is flawed, so don't bother.

I find it difficult to understand why someone like yourself could hapilly try to push/convince others to demolish half of their dashboards to built rediculous looking (also vision blocking and potentially illegal) waveguides for the sake of (imo probably minor) sonic gains, yet something as simple as adding a second sub and flicking the 'stereo' switch gets thrown into the "too hard" basket.

You are willing to go through ludicrous amounts of effort for a moderate potential improvement, but then you aren't willing to put in comparatively minimal effort to even try something which might bring a potential (if subtle) improvment.

Doesn't phase me, just a little surprised coming from a person who always seems willing to try anything in the name of sonic gain.

You know that very rarely do you have enough midbass output capability to keep up with a sub at the crossover point, right?

I find that the car's noise floor is the biggest issue here - especially in my case. Car off it's not a problem, but when im driving I need to turn up the system to quite significant volumes in order for the midbass not to be covered by road noise and blend properly with the sub.

br85

I don't think you've heard a good sounding car system.

In all honesty, I don't think I ever really have either.

Ok, to be fair I have heard a couple that were quite good, but none of the systems I've heard to this day (my own included) have ever really reached the potential that I believe exists in a car environment. There have been one or two that stood out to being quite good, but still not quite there...and the vast majority have just been way too flawed to really impress me.

I've been chasing my tail experimenting with different setups for eyons now for exactly this reason - I don't feel satisfied producing a completed install with my name on it until I am confident that the end result is truly exception, and without a doubt the best I can produce. With each experiment I get one step closer to greatness in individual aspects of car sound, but I've yet to produce something that can capture that type of greatness across the entire spectrum.

Don't get greatness confused with perfection - perfection is unachievable, greatness is the best of what is achievable.