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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Gordon Brinton on January 30, 2018, 05:23:40 PM
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At many of my typical bar gigs, I generally put my mixer rack right next to the stage and behind a FOH speaker stack. Because it is close to a stack, I sometimes use a 10 ft. XLR cable to feed the near stack and a 50 ft. cable to feed the far away stack. (They are powered speakers with built-in dsp, so just one full-range cable goes to each stack.)
Do you think that the difference in resistance between the two lengths is enough to notice any difference in sound or level from one side to the other? I do have several 50 ft. cables, but am usually too busy/hurried to dig them out.
During shows, I have noticed some slight differences between the two stacks, but I always thought that was caused by the proximity of walls and furniture or the speakers themselves being imperfect.
Should I make the effort to use a 50 footer on both sides just to balance things up?
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No
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There will be no noticeable difference.
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Definitely no. Especially not with line level audio. It would need to be more like thousands of feet before you would notice a difference.
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No
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no, and even with an passive PA i wouldn't think there will be a difference
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no, and even with an passive PA i wouldn't think there will be a difference
Which would not be noticable in a typical bar gig, over the noise of punters and given the poor acoustics in most such venues.
Just don't worry about it....
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Which would not be noticable in a typical bar gig, over the noise of punters and given the poor acoustics in most such venues.
Just don't worry about it....
Science trivia: How fast does the wave travel and what is the wavelength? Feel free to use the frequency of your local service.
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We haven't answered this question for at least several years...
Short answer is NO.
JR
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no, and even with an passive PA i wouldn't think there will be a difference
Not until the cable length difference becomes greater. And then it's not a time difference, it's a level/frequency response difference.
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Long answer: nooooooooooooooo.......
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Not until the cable length difference becomes greater. And then it's not a time difference, it's a level/frequency response difference.
Even though most here say the cabling issue is not a problem, in a lot of venues, one sub does sound punchier than the other. When I take a moment to stand in front of each one and listen carefully, they both sound good, but one sub seems to have more life than the other. They are identical and, as far as I can tell, set up the same. I guess they just sound slightly different for some other reason.
Recently, I did mark the one that sounded weaker with gaff tape and then tested them at home the next day. They both sounded identical in my work shop. Go figure. (Hence the questions here about cable length.)
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Even though most here say the cabling issue is not a problem, in a lot of venues, one sub does sound punchier than the other. When I take a moment to stand in front of each one and listen carefully, they both sound good, but one sub seems to have more life than the other. They are identical and, as far as I can tell, set up the same. I guess they just sound slightly different for some other reason.
Recently, I did mark the one that sounded weaker with gaff tape and then tested them at home the next day. They both sounded identical in my work shop. Go figure. (Hence the questions here about cable length.)
All speakers, especially subs, are affected by the walls, floor and ceiling. Also, the distance between the subs.
All of it.
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No on cables.
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If you were on passive subs and one side had a 100' 18ga cable and the other had a 10', 8ga cable I'd say yeah, it makes a difference... but in your example the answer is No. Nyet. Nada. Zip.
I believe Rob Spence has identified the most likely culprit - reflections. I found out how much relatively small objects can screw up dual channel FFT measurements by trying to measure and compare full range loudspeakers. Moving them around the shop (the changing geometry) meant that the same box would not measure the same upon repeating the measurement.
And if it measures differently it probably auditions differently as well.
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If you're interested in some of the theory behind 10' vs 50' of line-level audio cable not making an audible difference, here's a RaneNote (http://www.rane.com/note126.html) that goes into some detail about what long cables do to line-level audio.
-Russ
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It's too bad this thread was such a tempest of disagreement. Might be a LAB record.
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Recently, I did mark the one that sounded weaker with gaff tape and then tested them at home the next day. They both sounded identical in my work shop. Go figure. (Hence the questions here about cable length.)
With different length cables? Prove the point and connect all the xlr cables you have together on one sub. Then swap subs and cables.
One alternative question. Are you running stereo subs, or mono?
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1)Even though most here say the cabling issue is not a problem, in a lot of venues, one sub does sound punchier than the other.
2)They are identical and, as far as I can tell, set up the same.
3)I guess they just sound slightly different for some other reason.
4)Recently, I did mark the one that sounded weaker with gaff tape and then tested them at home the next day. They both sounded identical in my work shop. Go figure. (Hence the questions here about cable length.)
Gordon,
1) The length of the XLR cable between 10' & 50' should make no difference assuming they are low resistance, not corroded junk.
That said, the powered subs are powered from two different AC cables and no mention has been made of them. Those cables, and the wire in the circuit they are connected to can make a big difference.
2) Did you use the same circuit and AC cord length and AWG for both sides?
3) Both room acoustics and different voltage drop on either sub are likely reasons.
4) I would figure, given the subs sounded identical in a controlled environment, the power voltage level, as well as room differences are the differences you heard on the gigs.
I have measured as much as 6 dB SPL less sub output simply due to "brown-out", voltage drop.
Cheers,
Art
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Yes, it makes a difference, but only to those with "Golden Ears". Find someone with a $100,000.00+ home stereo and he will be able to hear it! Unfortunately, though this reply is somewhat in jest, I'm not really kidding.
I won't be able to hear the difference.
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Yes. It does. Ask the guys at D&B.
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If you want a definitive answer, take a signal and split it into 2. Run them on 2 same length cables, invert the polarity on one of them then sum them together. Look at a trace on smaart or other software and you should have full cancellation (no signal), adjust until you do as this will be your control. Then swap one of the cables for as long of a cable as you want. Any difference in signal between the two (phase or amplitude) will present itself in the trace.
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how far does electricity travel per millisecond? Depends on resistance, but probably 40-140 miles per ms... So, I could run a cable to disneyland and back for one subwoofer and it would be delayed 2ms. Dang, I'd have to move that sub forward 2 feet... 8)
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Yes. It does. Ask the guys at D&B.
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Obviously you've asked them. What's the/your answer, or are you trolling.
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Yes. It does. Ask the guys at D&B.
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I though D&B systems only utilized passive speakers.
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I though D&B systems only utilized passive speakers.
I believe the J-Sub is active, but I can't imagine a speaker that's only spec'ed up to 100Hz could possibly be affected by mic cable capacitive losses (unless you're literally driving 40+ mile runs of the stuff)...
-Russ
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I believe the J-Sub is active...
I haven't used that model, but the site specs indicate passive.
http://www.dbaudio.com/en/systems/category/series/detail/loudspeakers/j-series/j-subwoofer.html#ssch-db-systems-product-data-24 (http://www.dbaudio.com/en/systems/category/series/detail/loudspeakers/j-series/j-subwoofer.html#ssch-db-systems-product-data-24)
The whole D&B system concept built around passive cabs powered by theirs amps with built-in model-specific DSP. I've never seen or heard of an active model. Disclaimer - I'm not a D&B guru.
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how far does electricity travel per millisecond? Depends on resistance, but probably 40-140 miles per ms... So, I could run a cable to disneyland and back for one subwoofer and it would be delayed 2ms. Dang, I'd have to move that sub forward 2 feet... 8)
The way it was explained to this young puke back in the 70's was...
Imagine a hose, 1000 feet long, 3/4" ID, filled end to end with 3/4"marbles. push a new marble in one end, and at the same time, one will pop out the other end.
In effect, the speed of electrons in instantaneous, as when one is missing, another one gets sucked in to replace it.
Chris.
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The way it was explained to this young puke back in the 70's was...
Imagine a hose, 1000 feet long, 3/4" ID, filled end to end with 3/4"marbles. push a new marble in one end, and at the same time, one will pop out the other end.
In effect, the speed of electrons in instantaneous, as when one is missing, another one gets sucked in to replace it.
Chris.
That's pretty much it.
Voltages move at the speed of light.
Marbles in a hose will actually move quite a lot slower, but the analogy holds.
Chris
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As has been suggested - electron drift - the movement of a particular ‘marble’ through the hose does happen, but very slowly. It is the marbles pushing on each other that happens at a significant fraction of the speed of light, but not actually at the speed of light (the dielectric material around the conductor affects this), but even in the worst case, it’s many orders of magnitude faster than the speed of sound in air, and therefore irrelevant.
Long cables can sound different than shorter cables for other reasons, though; how much of an impact this has depends on the application and length difference.
- Cable capacitance acts as a low-pass filter, so over long distances high-frequency response is lost. In mic-level situations, the length where this gets to be problematic is in the hundreds of feet, not the tens of feet, and it can easily be compensated for with a simple high-boost filter.
- Cable resistance can be a factor as power is lost over the length of the cable. If one speaker’s cable’s loop resistance was .1 ohm and the other’s was 1 ohm (extremely long or very small wire) driving 4 ohm speaker loads you might notice the difference, but I bet it would take more of a disparity than you would think before it became noticeable.
- Cable resistance also reduces damping factor, which in extreme cases can be audible.
All that said, other than in highly-controlled listening environments or extreme cases, these are non-factors, and the answer to the OP’s question is still ‘no’ for a typical lounge-level situation.
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answer is still NO...
JR
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I haven't used that model, but the site specs indicate passive.
Yup, you're right. I read "actively driven" in the description and assumed that meant "has an amplifier built in", which it looks like it doesn't. I am also not a D&B guru, clearly (although I too was surprised by my mistaken take on the J-Sub; I couldn't imagine D&B making an active product, and I guess my imagination is better than my reading skills...).
-Russ
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Yup, you're right. I read "actively driven" in the description and assumed that meant "has an amplifier built in", which it looks like it doesn't. I am also not a D&B guru, clearly (although I too was surprised by my mistaken take on the J-Sub; I couldn't imagine D&B making an active product, and I guess my imagination is better than my reading skills...).
-Russ
Yeah, a d&b speaker with an amplifier built into it is kinda like a gas-powered Tesla. I'm sure they Could do it, but it's basically goes against a fundamental system design decision.