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Old 26th February 2010, 02:12 PM   #1
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Default Acceptable loss in cables for pro-audio use

I came across some ( loudspeaker ) cable loss charts for pro-audio and noticed that the chart was based on 0.05dB insertion loss . Is this typical or can one tolerate more loss ? Like say 0.5dB or even 1 dB( in the cable)? At 115dB spl this should be inaudible. Right ?
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Old 26th February 2010, 02:35 PM   #2
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1 dB is a lot of power!
If your amp is PA amp is putting out 1000 Watts, then 200 of those Watts are just heating the speaker cable.
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Old 26th February 2010, 02:43 PM   #3
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I agree that it's a lot of loss. But the cable is long and per meter loss might be low. However what matters is if one can 'hear' a noticeable loss compared to a direct connection ( very short cable). I'm assuming that there is no loss at the speaker due to cable inductance/capacitance at HF.
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Old 26th February 2010, 03:17 PM   #4
AndrewT is offline AndrewT  Scotland
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-0.05dB is ~1% loss.
That implies the cable resistance is dissipating 1% of the speaker power.
This then implies that the cable resistance is ~Speaker impedance / 100.

A 4ohm speaker driven from an amp with 0r01 output impedance will sound different if 0r01 cables are swapped for 0r04 cables.

For a 1dB loss the cable resistance ~1r03. The sound of the speakers will be transformed if the 0r01 cable is swapped to 1r cable.
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Old 26th February 2010, 03:57 PM   #5
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While Andrew's post is correct, it's not one of his most coherent and he lives in GB!

What you are in effect doing, is putting a 1 Ohm resistor in series with a 4 Ohm speaker. Because the speaker is not 4 Ohms at all frequencies, the frequency response will very with changes in the speaker impedance. This is the same thing as using a SET (Single Ended Triode) amplifier.
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Old 26th February 2010, 04:28 PM   #6
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Let's not get into trivial calculation of cable resistance etc.

The question is ' can you hear a 0.5db or 1dB drop in volume when playing at 115 dB spl '?
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Old 26th February 2010, 04:37 PM   #7
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by ashok View Post
Let's not get into trivial calculation of cable resistance etc.

The question is ' can you hear a 0.5db or 1dB drop in volume when playing at 115 dB spl '?

methinks the flapping sound of ruptured eardrums might mask some of the theoretical loss


but seriously, 115dB is pretty fracking loud, and no doubt many systems would be exhibiting dynamic compression on both ends of the cable - rendering the question moot?
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Old 26th February 2010, 05:11 PM   #8
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[QUOTE=chrisb;2100049]methinks the flapping sound of ruptured eardrums might mask some of the theoretical loss

..That's a good one.
Well at 110dB at one meter from the speakers...OK ! SPL at about 10 meters will be much less !
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Old 26th February 2010, 08:29 PM   #9
Glowbug is offline Glowbug  United States
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Quote:
The question is ' can you hear a 0.5db or 1dB drop in volume when playing at 115 dB spl '?
You couldn't hear that regardless of SPL
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Old 26th February 2010, 09:49 PM   #10
Eva is offline Eva  Spain
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A 1dB or 0.5dB drop in volume at all frequencies is hard to notice, however, +/-0.5dB changes in tonal balance due to different attenuations at different frequencies (due to uneven impedance of real speakers) are more noticeable, particularly at high SPL.

Imagine a speaker system with 4 ohm bass driver (going to 2.5 ohm at some frequencies) and 16 ohm compression tweeter (going to 20-30 ohm in the top and bottom ends)...
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Last edited by Eva; 26th February 2010 at 09:51 PM.
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