Can someone come up with the inductance , capacitance and dc resistance of a VERY highly regarded speaker cable that others say makes a huge difference to the sound. Values for a typical length of cable -- 10 feet ?
We can then use a VERY short speaker cable from the amp to the speakers. Say 1 or 2 feet. Then add that R , L and C and see if the sound changes the same way as the original cable.
Does this make any sense ?
That's it. Its 11.40pm and I'm crashing out for the night.
Edit: Just saw your post John. Yes you are probably right. But it would be interesting to do some tests. So we have to check for
1. Frequency response changes
2. Imaging changes
3. Transient performance (?) -- e.g. percussion.
Do we add anything else?
We can then use a VERY short speaker cable from the amp to the speakers. Say 1 or 2 feet. Then add that R , L and C and see if the sound changes the same way as the original cable.
Does this make any sense ?
That's it. Its 11.40pm and I'm crashing out for the night.
Edit: Just saw your post John. Yes you are probably right. But it would be interesting to do some tests. So we have to check for
1. Frequency response changes
2. Imaging changes
3. Transient performance (?) -- e.g. percussion.
Do we add anything else?
ron.eddy said:Makes sense. After all, the cables still have L, C, and R paramters, no matter how small compared to wavelength they are.
My next question would be, do different circuit traces (more copper weight, better separation from other signal conducting paths, etc...) have an effect on the audio? As I said, I have no opinion either way on cables and I maintain that, but if one were to look at the traces on the circuit board would we not find the same effects on audio in many areas of the signal? And so what if the traces are only a foot long total (signal path) they should still matter, right?
It is admittedly hard for me to concentrate on cables as a sore spot in the chain when the circuits are sitting there on their FR4 material with no shielding (other than (maybe) a metal case around the whole thing). How short does it have to be of a run for nothing to matter as far as the audible difference? Would a 6" cable made of anything perform just as good as an expensive 6" cable? How about 3" or maybe a circuit board trace of 2"? My point in this is that there is no point - there is no one place where all of this could ever stop. For every one thing you could say for cables and how they may degrade the signals, you could say something about the rest of the circuit based on that.
This is a fun thread to have once in a while, no doubt about it, but it is also frustrating in that there will be no resolve to it. Whether cables make a difference or not makes little difference to the main fact that we are all crazy (in a good DIY audio sort of way
- I do realize this post does not solve or help to solve any of the questions, but I hope it makes everyone feel a little better about this impossible argument we have gotten ourselves into, hehe.
- Ron
Agreed, these are the fun threads.
At audio, nah.. unless the trace width produces too much cap for the circuit, or couples the trace to sumptin nefarious.
Far too many people change something, hear a diff, and attribute the diff to what they wanted to change. Correlation perhaps, but certainly not causation. It gets kinda sticky making sure you change only that which you want to test.
Kinda like waving your hand over a 100 megohm impedance input and saying it's your aura that affects the circuit..instead of body capacitance or triboelectric charge generation..
Cheers, John
Hi Ron,
From experience, trace routes and thickness / weight do make a difference. I don't think the route the speaker cables take make a difference within reason.
I think what you are saying is that you have to make sure the effect (whatever it may be) has a high enough magnitude to have an affect on the system. Otherwise, don't worry about it.
The trick is to define the variable and properly test it so you can quantify it. But isn't that the rub?
-Chris
From experience, trace routes and thickness / weight do make a difference. I don't think the route the speaker cables take make a difference within reason.
I think what you are saying is that you have to make sure the effect (whatever it may be) has a high enough magnitude to have an affect on the system.
Otherwise, don't worry about it.The trick is to define the variable and properly test it so you can quantify it. But isn't that the rub?
-Chris
Hi Ashok,
For your test I think the source and load will have to be characterized. That will give you an idea whether the cable's characteristics are swamped out by the rest of the circuit. This may help to explain what results you get and how it may apply to a different system.
-Chris
(My this thread is busy)
For your test I think the source and load will have to be characterized. That will give you an idea whether the cable's characteristics are swamped out by the rest of the circuit. This may help to explain what results you get and how it may apply to a different system.
-Chris
(My this thread is busy)
poobah said:
Over at AH, Gene D measured a bunch, in that shootoff style article. At my insistence, he went out to a Mhz, as I am interested in localization theory which requires time resolution down to 2 uSec or so. I tried for higher, but he reached the limit of the equip.
Some of the vendors can't accurately measure their product, inductance measurement at the nanohenry level is beyond most.
If they do, multiply their L times their C, L in nH per foot, C in pf per foot....if that product is below 1034, then the info given is inaccurate, they just broke the speed of light. The number should be EDC times 1034, EDC typically between 2.5 and about 7.
Cheers, John
ashok said:
I do not expect FR differences. Nor , at first level, transients...gotta qualify that one, however.
Localization...that is what I'd look at.
Parameters:
1. A transient signal rich in harmonics, like a cowbell. Record it to both channels, with the right channel advanced 100 microseconds in front of the left.
2. Record the right channel .1 dB louder than the left, for that cowbell.
You have just placed the cowbell at a distance of 100 inches from you, and 20 inches off axis to the right. (don't use a pan control for this, or I'll hafta smack you
pan pots are the scourge of the audio industry.Now, put another, different transient signal dead center..zero time diff, zero amplitude diff. This puts that sound directly on axis. If it is the same general amplitude as the cowbell, it will seem to be 100 inches away also.
3. Put a 50 hz loud bass signal into one channel only, then the other, then simultaneous.
Listen for blurring or fuzzyness of the bell image on the right. If the bass is too much in the way, you may hafta disable the woofs and sub dummy loads for the woof vc's. Ya gotta pull the power through the cable..
It'll also be dependent on the resistance of the wire, as it takes some power to invoke the sin squared distortion inherent when splitting the spectra out at the load. Speaker crossovers...sheesh..another rant..
I can go much further, but go to sleep!!!!!!!!!!!
Oh, speaker placement makes a diff, but that needs further work on my part. Sorry bout that.
Cheers, John
analog_sa said:
I must elaborate..
My test description is entirely speaker cable..not ic. Sorry bout that.
Ic's are a whole other ballgame. My test will only be applicable once the lumped elements within the ic's have been considered, and normal rolloff or lack thereof, is considered.
To test IC's, first you need an amp that does not have coupling to ic shield ground currents.
I have not seen anyone test for that. Ground loop hum is a big indicator this exists.
I'm going through this with my audiophile friend at the moment. He claims he can here the differences in ic's, so we are investigating his system for loop coupling first..
Cheers, John
analog_sa said:
Using the mains ground is not a requirement. The ground loop doesn't have to be hard, course some reactance would help, now wouldn't it?
Don't neglect to remember that the loop sensitivity is proportional to the intercepted magnetic slew rate, ie proportional to both frequency and current. Supply haversines and coupled audio can be rather daunting to eliminate from pickup. The main issue with detection is masking of any effect by the musical content. A really bad loop gives itself away by virtue of either hum, or noise pickup. One which is not so bad, will not be so kind.Balanced certainly helps a whole lot. But is the amp balanced in regard to grounding current? If you toss current into the grounding pin of the xlr, from 20 hz to 20 khz, through to the power cord ground (or capacitively, to the hot/neutral pair), does the amp completely reject it? Not the same test as a common mode voltage test.
I proposed over on AR coupla years ago, testing an amp for ground loop sensitivity. procedure, parts..setup..to no avail..maybe here?
Cheers, John
analog_sa said:
Your killin me..
I'm just about to embark on a b'day vaca, no time to really get into it..
here's the jpeg I posted back in march of 2004.
Please forgive the rudimentary quality of my chicken scratches..
It shows the power cord loop, the ground loop (either hard or soft), how the power cord haversines will couple to the ground loop (or, any mag field in the area for that matter), and one of the ways the chassis current from the gorund loop can get into the input wiring. Since we are talking about currents and magnetic fields, I invoke faraday's law of induction to develop the relationship. To keep it simple, I just used constants of proportionality rather than attempting to calculate the actual numbers. The effort was to determine the frequency dependence of the effect.
Note that the overall coupling from the powercord current to the input current is proportional to frequency squared.. If you are hearing, while coupling to external stray fields is simply proportional to frequency, leaving out the middle man, so to speak.
So even if you don't hear the 60 hz fundamental of the amp's power draw, the sensitivity to the first power harmonic of a haversine, which is 180 hz, is 9 times that of 60 hz, and the second power harmonic of 300 hz (haversines are odd order harmonics) is 25 times more sensitive.
Here at work, the building PA input ground loop is so bad, that the hum that we hear is directly proportional to the power level of the anouncement, it sounds like somebody built a circuit that reads the audio power level, and amplitude modulates the hum and injects it into the audiostream..(actually, that's exactly what it is..
Oh, almost forgot..note that the effect includes the total loop resistance in the denominator.. That predicts that the level is dependent on the shield size, the outlet contact resistance, the line cord ground guage..
This diagram is a predictor, and should be tested for overall level of effect.. Oh, it also provides allowance for pushing the amp without the source of the push getting involved with the ground loop we are trying to look for. It also allows measurement of audio signals getting into the line cord. Kind of a generic test. In a hurry, otherwise I'd try to find the other scans.
I'm off to vaca, till the 12th..
Cheers, John
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jneutron said:
I do not expect FR differences. Nor , at first level, transients...gotta qualify that one, however.
Localization...that is what I'd look at.
Parameters:
1. A transient signal rich in harmonics, like a cowbell. Record it to both channels, with the right channel advanced 100 microseconds in front of the left.
2. Record the right channel .1 dB louder than the left, for that cowbell.
You have just placed the cowbell at a distance of 100 inches from you, and 20 inches off axis to the right. (don't use a pan control for this, or I'll hafta smack you
If only it would be that simple.
Let's say you have 2 speakers in the standard equilateral triangle setup and your ears are about 6 inches apart.
Consider the moment when the sound reaches the right ear 0.
About 220 ms later the same signal travelling around the head and upper torso considerably changed in FR response reaches the left ear. Atteanuation is minimal in the LF, but can be 6-10 dB in the HF.
The same happens with the signal from the left channel. The direct signal reaches the ear at 100 ms and the HRTF modified the right at 320 ms.
The LF signals are recombined at both ears, mostly preserving the ILD , but generating about 6-10 dB ILD at HF, which is not in the original stereo signal. ITD is all mixed up with the double arrival. It is is perceived in the HF as a strong early reflection that is delayed by over 200 microseconds and so is will not merge well with the direct sound. While this not usually audible as changes in pitch or overtones, this combing causes level changes that generate ILDs at some frequencies but not others so that an instrument can appear to be moving for some notes.
This combing also mimics pinna direction finding patterns further confusing localization.
Of course pinna direction finding patterns will still tell your brain that you are listening to 2 seperate sources several feet apart, not a single source at 20 deg.
As I stated origionally, this does not account for our ears, it is only the ideal best situation. Testing for degradation of capability vs frequency and directivity will only reduce the overall capability. Understanding the concepts is the primary goal here, for me.fcserei said:If only it would be that simple.
Your numbers seem suspect, the 220 mSec especially..are you missing a decimal point somewhere
When I get back, I'll ask you to post your math. At 300 meters per second, that seems like an awfully long path transit time..Even Nordmark talked about 600 hz. You're talkin, what.. five hz?
Gotta go, man I hate it when the threads are interesting and I gotta bolt..
I look forward to furtherance..
Cheers, John
Sorry you are right, 220 usec.
IMHO there is no use to speak about ideal best situation if realistics sound localization is the target.
For ITD ald LTD tests headphone is the best, but nobody ever accused headphone listening to be realistic ( unless it is binaural recorded with HRTF matching the listener's - but even in that case sall head movements can ruin the experience)
IMHO there is no use to speak about ideal best situation if realistics sound localization is the target.
For ITD ald LTD tests headphone is the best, but nobody ever accused headphone listening to be realistic ( unless it is binaural recorded with HRTF matching the listener's - but even in that case sall head movements can ruin the experience)
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