This speaker cable loss calculator simply tells you how much resistance is in your speaker cables and what decibel(dB) and power losses are attributed to your speaker cable. It also calculates the effective damping factor.
This speaker cable loss calculator is designed for low impedance systems – like Hi-Fi, home theatre and other music systems. Low impedance is a term used to refer for systems where the amplifiers are designed for speakers which have a nominal impedance of 2 to 16 ohms. High impedance systems are commonly called 70 volt or 100 volt systems, and are used mostly in commercial installations requiring more than 2 speakers connected to each amplifier. This calculator can be used to calculate speaker cable loss on high impedance systems.
Like all my calculators, simply input the required information in the white cells.
Units of Measure
First up, select the units of measure. Either “Metres & mm²” or “Feet & AWG” can be selected by clicking on the white cell and selecting from the drop down options. Most countries use metric, meaning the cable lengths are measured in metres, and the cable size is in mm². For countries not using metric, select “Feet & AWG” – the cable lengths will be in feet and cable size will be the AWG gauge number.
Cable Length and Size
Then the next two cells to fill in are the cable length and the cable size:
- Cable length refers to the length of the cable from the amplifier terminals to the speaker terminals.
- Cable size refers to the thickness of the speaker cable. What you enter here depends on the units of measure you chose.
| Metres & mm² | Feet & AWG |
|---|---|
| Enter the Cross Sectional Area (c.s.a.) of the cable in mm² (Eg. 0.75mm² )  | Enter the AWG gauge number (Eg. #18 gauge)  |
Specified Speaker Impedance
Speaker impedance is the impedance stated on the back of the speaker or in the speaker’s manual. It should be specified in ohms (the symbol for ohms is “Ω”). It is normally 4Ω, 6Ω or 8Ω.
Calculated Cable Losses
Once the above values are entered, you can see the calculated results in the box labelled “Calculated Cable Losses”. Here you will see the total resistance of the cable, and the resulting decibel (dB) reduction in power reaching the speaker due to the cable loss.
For many people, that is sufficient information. For example if you just want to know if your cable losses are greater or less than say 0.5dB, then you have that information.
However, if you want to know more about how the cable affects your amplifier and speaker system, then you can add in your amplifier specifications.
Amplifier Specifications
- Specified amplifier power should be in the amplifier’s manual or specifications. Keep in mind that some manufacturers only state their absolute maximum power ratings, which are generally not sustainable for longer periods of listening or are come with considerable distortion. I advise you use the most conservative ratings, which should be stated as “Average Continuous Power”, “Continuous Power” or “RMS Power”. A major Hi-Fi manufacturer shows the following in their specifications:
Here they use “Rated Output Power” for their conservative ratings. Notice the THD (Total Harmonic Distortion) is very low (0.07%), unlike their stated maximum power which has 10% THD!
Note that all power output ratings of an amplifier are at a specified impedance. For best results in the calculator, use the stated output power at the impedance closest to your speaker’s impedance. For example, if you have an 8 ohm speaker connected to the amplifier, using the specification above, enter “90” for the stated output power, and “8” for the load impedance.
If the specifications only have a power rating at one stated impedance (Eg: 100 watts @ 4 ohms), use that specified output power and that specified load impedance.
Damping factor should be another listing in the specifications of the amplifier. If it is, and it is something you are concerned about, then also enter the stated amplifier damping factor in the white cell.
If you can’t find the damping factor, or it is of no or little interest to you, then it doesn’t matter.
Calculated Damping Factor & Maximum Power
This box uses a simple diagram to display the maximum power output of the amplifier, the maximum power loss in the cable, and the resulting maximum power reaching the speaker. Note, these values are based on the amplifier running at the specified maximum continuous power.
The calculated damping factor is also displayed in this box.
Note: the calculator is best viewed in landscape mode on phones and small screens
| Download Calculator as Excel File |
Prices in US$ |
What do the results mean?
While the results of the above speaker cable loss calculator are theoretically correct, how they are interpreted will depend on which school of thought you subscribe to, how good you think your ears are and how much you care.
Some people suggest the cable losses should be less than 0.3dB. Others say anything less than 0.5dB is not discernible. Others say that if you don’t run the system at maximum power, then simply adjust the amplifier volume control to the level you want and you don’t need to worry about any losses.
Then there is the damping factor to consider (or not). If you’re unaware of damping factor (DF), then there are myriads of articles about it, and just as many suggestions as to what value you should aim for.
Basically, the effective DF indicates the ability of the amplifier to control the speaker’s movement (especially any overshoot). It mainly concerns the low frequencies, and a low DF can result in the some of the low frequencies (like a kick drum) sounding a bit soft or “muddy”.
Some people suggest the effective damping factor should be above 100. Others suggest 50 is good to aim for, and others suggest 10-25 is acceptable. Other people don’t care. It is mostly regarded that the higher the effective DF the better.
The effective DF is mostly determined by the cable resistance and the speaker impedance. An 8 ohm speaker will almost double the effective DF compared to a 4 ohm speaker. Decreasing the cable loss (by using a thicker and/or shorter cable) will increase the effective DF.
Summary
Speaker cable loss is something to be considered, along with many other factors like speaker impedance, sensitivity, power rating and frequency range, amplifier power, and budget.
A thicker speaker cable will decrease the cable loss, increase the damping factor, and increase the cost.
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