E30 Zone

Nearley set up my sound system but have just tried to wire the sub to the amp but cannot figure which lead to use,

I thought it would have been rca, but they dont seem to fit into the sub.

What cable do I need?

The sub is a JBL.

Rkive wrote:Nearley set up my sound system but have just tried to wire the sub to the amp but cannot figure which lead to use,

I thought it would have been rca, but they dont seem to fit into the sub.

What cable do I need?

The sub is a JBL.

Sub - amp uses speaker cable!
Fatter the better I believe.

Not correct eko. If it is to fat it will lose sound/power. Common install problem...


Rca from head to amp and cable from amp to sub...

You can use oxygen free speaker cable which is better than usual cable, and theres different awg's so get one that you think suits you sub and amp, as in power wise...

Well the amp wiring kit came with some speaker cable and it is about twice maybe three times the thickness of the usual thin speaker cable.

Would this be ok to go from sub to amp?

zaust wrote:Not correct eko. If it is to fat it will lose sound/power. Common install problem...

Sorry, but that's total rubbish.

Heyho

Well the amp wiring kit came with some speaker cable and it is about twice maybe three times the thickness of the usual thin speaker cable.

Would it be ok for sub 2 amp?

Heyho wrote:

zaust wrote:Not correct eko. If it is to fat it will lose sound/power. Common install problem...

Sorry, but that's total rubbish.

Please inlighten me...

Heyho wrote:

zaust wrote:Not correct eko. If it is to fat it will lose sound/power. Common install problem...

Sorry, but that's total rubbish.

i take it you dont know that Marc has worked on some of the best ICE show cars to be built on the show scence then,

and again,

Well the amp wiring kit came with some speaker cable and it is about twice maybe three times the thickness of the usual thin speaker cable.

Would it be ok for sub 2 amp?

it will be fine

Rkive wrote:and again,

Well the amp wiring kit came with some speaker cable and it is about twice maybe three times the thickness of the usual thin speaker cable.

Would it be ok for sub 2 amp?

Ive used the cable from the kit and it works fine. It all depends how good you want your system to be. Its quite fat cable aswell, the best way is to try it and see what you think.

Peter

Rkive wrote:and again,

Well the amp wiring kit came with some speaker cable and it is about twice maybe three times the thickness of the usual thin speaker cable.

Would it be ok for sub 2 amp?

Sorry fella. This thread went off track a bit.. Most kit's will be fine.

No worries mate, just wanted to make sure it was ok.

i think Heyho is implying that a thicker wire will have a lower resistance (or actually impedance) per metre and thus a lower loss per metre therefore transfering more power from amp to speaker, so in this case i do agree a thicker cable will be better than a thinner cable assuming construction of the cable is the same, in fact the ideal speaker cable would be a very thin tape as this has the lowest impedance and thus lowest loss, but the low cross sectional area would not be suitable for carrying large currents and it would be difficult to route round the car....... discuss

Some sence. Yes ribbon wire is the ideal, But correct no bend's so rellay rules car's out for fitting. Back to the oversized cable though. When the resistance gets too high or thw wire is to big/fat. First there is power lost in the wire and the speaker will not play as loud. As the resistance in line with the speaker increases, it makes the amplifier look more like a power station. This means the speaker frequency response will tend to follow the rise and fall of its impedance. The greater the impedance variation, the more noticeable the response changes will be. If the speaker has constant impedance versus frequency, the only change will be reduced output.

So there.. lol

Right so I have the correct cable, but how do I connect the cable to the sub?

There doesnt seem there is an obvious way, sorry for my lack of knowledge.

should just be some screw on connections on the sub, the anp will prob have some little plates with screws to clamp down the cable ends.

post up some pics we'll let you know.





one thing to check, if you have a front battery, make sure you use a rubber grommet where the power cable passes thru
the bulkhead, dont want it arcing on the car and catching fire.

On the sub are screw caps, and a little plastic piece inside, just wondering if it goes it how it will be held in.

zaust wrote:When the resistance gets too high or thw wire is to big/fat. First there is power lost in the wire and the speaker will not play as loud. As the resistance in line with the speaker increases, it makes the amplifier look more like a power station. This means the speaker frequency response will tend to follow the rise and fall of its impedance. The greater the impedance variation, the more noticeable the response changes will be. If the speaker has constant impedance versus frequency, the only change will be reduced output.

So there.. lol

I think you need to go back and read ohms law again

You can't really go too big or fat with speaker cable (or any cable for that matter). You can however go too thin. If the wire is too thin, it will not be able to pass enough current, and will get hot. If you take it to the extreme, it will act like a fuse, and simply burn out.

You will only see power loss in the speaker cables if they are too small, or if you have crappy connections.

Ian.

On the sub are screw caps, and a little plastic piece inside, just wondering if it goes it how it will be held in.

I think the connection is XLR, so how would I fit the lead into it.

Rkive wrote:On the sub are screw caps, and a little plastic piece inside, just wondering if it goes it how it will be held in.

Is this an enclosed sub (in a box) or a free air sub (not in box) we are talking about.

If enclosed, the box should have a connector on the side like this (bottom right):



The sub should have a connector something like this (left hand side):



Hope this helps, if not, please post a pic up of what you have.

I forgot to mention, on the box connectors, some look like you push 2 plugs in the top (which you can) but you can also unscrew them to reveal a hole to put standard wire through, then put the wire in and tighten.

ian332isport wrote:
I think you need to go back and read ohms law again

You can't really go too big or fat with speaker cable (or any cable for that matter). You can however go too thin. If the wire is too thin, it will not be able to pass enough current, and will get hot. If you take it to the extreme, it will act like a fuse, and simply burn out.

You will only see power loss in the speaker cables if they are too small, or if you have crappy connections.

Ian.

At last, somebody talking sense!

The only thing you really need to worry about is that the speaker cable is big enough - you will only encounter problems if the CSA of the cable is too small for the amount of current you're trying to pass through it.

I am aware of the behaviour of speakers, and their tendancy for the impedance to change with regard to frequency, but this has no bearing on the cable. The rest of the explanation didn't make a great deal of sense - sorry.

Rkive - the cable supplied with the kit will be fine I'm sure.

Right cool,

Does anyone also know about the lead that connects somewhere like the ignition so that the amp powers up when the car is started?

Rkive wrote:Right cool,

Does anyone also know about the lead that connects somewhere like the ignition so that the amp powers up when the car is started?

You need to take the blue 'remote' wire from your head-unit. That is the connection you use to tell your amp when to switch on and off.

ian332isport wrote:

zaust wrote:When the resistance gets too high or thw wire is to big/fat. First there is power lost in the wire and the speaker will not play as loud. As the resistance in line with the speaker increases, it makes the amplifier look more like a power station. This means the speaker frequency response will tend to follow the rise and fall of its impedance. The greater the impedance variation, the more noticeable the response changes will be. If the speaker has constant impedance versus frequency, the only change will be reduced output.

So there.. lol

I think you need to go back and read ohms law again

You can't really go too big or fat with speaker cable (or any cable for that matter). You can however go too thin. If the wire is too thin, it will not be able to pass enough current, and will get hot. If you take it to the extreme, it will act like a fuse, and simply burn out.

You will only see power loss in the speaker cables if they are too small, or if you have crappy connections.

Ian.

It's not just ohm's law in the case of a speaker...
Check it out again.
I will dig the formula out of my desk when I get to work in the morning..
I argued against what I'm now saying and I was proved wrong. lol

I also agree its not as simple as V=IR as we are into AC and what more AC across a wide range of frequencies where we take into account the skin effect and the resultant changes in the cable effective resistence due to the higher current density at the surface of the conductor, the way round this of course is to use Litz wire (which is effectively a multicore cable with each core insulated, thus the skin effect is lessened) and even to a lesser degree multi strand cables where the air gap between adjacent uninsulated cores assists in the lessening of the skin effect.... but in this particular thread Rkive is asking about a sub connection where we can really assume he is feeding a speaker from an amp with some sort of frequency filter, thus we can only apply his questions to the lower frequency signals and in this case i am afraid V-IR is a more valid equasion than the complicated equasions for higher frequency signals (including capacitance per metre C/m-1, inductance per metre H/m-1, angular frequency 2pi x f, etc etc), thus a thicker wire will be better as the effective resistance per metre is inversely proportional to the cross sectional area of the cable, and you do agree that less resistence between speaker and power source will result in less losses!!!

so yes use as thick a wire as practical, and if possible a multi strand wire and the one thing that no one has seemed to touch upon and what will definately have the biggest effect on power loss..... keep it as short as possible, so fit the amp right next to the speaker. Its also worth noting that twisting the pairs of wires will also lessen the effective impednace and thus result in a better signal transfer.

as for your wire from head unit to amp, that is only a voltage signal to turn the amp on, you can use any insulated wire. wire the size is irrelevant.

the other wires are you RCA lead i.e that brings the sound signal from head unit to amp, get the best quality ones you can afford, same with the power leads to supply the amp, try to use the biggest wire you can find as if the amp draws a lot of current the wire will bget hot and could burn out if its too small.

But lets be honest after all the technical ballacks above, and unless you are going for sonic perfection just use whatever wires you hane been given with your amp.... the deisgn of your sub enclosure will have the biggest effect on sound quality for a fixed set up.

discuss.....


mrlee

mrLEE, you are absolutely correct that there is a lot more to electrical cables than just ohms law - much of which I have long since forgotten.

What I am fairly sure of, however, is that capacitance, inductance and the skin effect of cables does not even come into play when considering the frequency range and cable lengths involved in car audio.

Lenght's and widths are the same calculation, I have been looking but can't find them...aaagghhh.
I will because I need them...

Heho, capacitance, inductance, resistance, make up the Impedance. Which are reactive load's are found in the speaker's x-over's and amp's. It's the transfer of the Ώ(Impedance) and Watt's and where there is an optimum W/L for them. Ie when does it start to disapate.

The wave resistance, or impedance, is an important cable parameter calculated from the ratio of inductivity to capacity. It is specified in units of Ohm (W). If the devices and the wave resistance of the cable do not match, reflections occur.


Still discuss.

Boxes are a whole book on there own. lol

as the impedance (Z=R + jX) of a cable is made up of the vector sum of the real (R) and imaginary (Reactance) componants, the capacitive effect of the cable will have an effect.

the real problem is matching the source impedance with the load impadence thus avoiding reflections and attempting to make the source impednace equal to the load impdedance (to allow maximum power transfer from source to load) and as the cable will be ''seen'' as part of the load impedance then we should attempt to have the lowest cable impedance as possible. but i will also agree that on such a short length the cable impednace will ne almost negligable when compared to the internal impedance of the speaker itself, so yes the capacitive effects of a cable will come into effect but you are proabaly right in saying it has no real practical effect on such a short length of cable.

The skin effect does have an impact but only really at high frequencies (and the effect is quite significant at frequencies approaching 25-30kHz), but as i said to the layman in a noisy car it would not be noticable.

blah blah blah boring!!!

mrlee

mrLEE30 wrote: The skin effect does have an impact but only really at high frequencies (and the effect is quite significant at frequencies approaching 25-30kHz), but as i said to the layman in a noisy car it would not be noticable.

blah blah blah boring!!!

mrlee

I'm not saying that skin effect doesn't exist, only that it is a myth that it would produce an audible effect. I do have a loose grip on the basics, and I am aware that it is really only a problem in single core conductors, so multi-strand speaker cable will not be affected to such a degree - particularly when you consider that a small percentage of adults are able to hear right up to the 20khz threshold, with the rest having to be content with about 16khz or so.

There are countless parameters which can be measured, but how many actually have any effect in the real world? Far better to concentrate on getting the basics right.

Back on topic, I was merely stating to the OP that using speaker wire with a CSA exceeding that which is required will not do any harm, or have a detrimental affect on the sound of his system.

Cheers, Paul.

lol. sorry, i had to after reading almost 2 pages of that!

comprising the last almost 2 pages means that Rkives(charles') wires should be fine for what he is looking to use them for.

Back on topic, I was merely stating to the OP that using speaker wire with a CSA exceeding that which is required will not do any harm, or have a detrimental affect on the sound of his system.

Yes i agreed!!!

lol. sorry, i had to after reading almost 2 pages of that!

comprising the last almost 2 pages means that Rkives(charles') wires should be fine for what he is looking to use them for.

yes i agreed with this too!!!

i think most of what was said (well what i said) was tongue in cheek anyway, no it will have no real effect and yes he can use 2500mm2 220kV.Cu.XLPE.Pb.LLDPE cable if he can find it, alternatively he can happily use the cable provided (which i also suggested much earlier in the thread!!!)

discuss