Ohm's

[Roper]

i have done a little search but cant the answer i'm looking for.
pred_vtr will probs know this. :P :y:

anyway, when looking at the specs of speakers, amp, subs etc, they talk about ohms, i know it the measuement of resistance, but how do you change the ohms of a system, if this is possible?? :panic: :panic:

because e.g. an amp can produce

180 watts RMS x 2 channels at 4 ohms
300 watts RMS x 2 channels at 2 ohms
600W RMS bridged mono @4ohms
Ratings at 14.4V supply.

how do you change the ohms?:panic:

thanks lee.

[reevesy_vtr]

it is all down to how you wire the speaker. it nothing to do with the amp.

[Predator_R32]

have a look on the rockford fosgate site for some diagrams of wiring up subs in different ohms

[djrem]

the direct link if your still looking:
http://www.rockfordfosgate.com/rftech/woofer_wizard.asp

[Predator_R32]

i know about wiring subs up but with justspeakers/components im not entirely sure, all i know is its all about how you wire them up

[CSVTR]

If you want to read up a bit on the basics of car audio this site may be of some use to you:

Basic Car Audio Electronics (http://www.bcae1.com/)

Now onto your question, single voice coil speakers have a fixed ohm configuration. Most components speakers will be 4 ohm, some are 2 ohm like the RE Audio XXX (http://www.reaudio.com/components.html) mids. Subs however come in all sorts of different impedances. SVC (single voice coil) and DVC (dual voice coil), these can come in 4, 2, 1, and even .5 ohm, the load that an amp delivers is only adjustable by the configuration of the speakers.

The link below is to a wiring diagram, have a play around with the options available and you will get a brief idea of how impedances work:

Wiring Wizard (http://www.rockfordfosgate.com/rftech/woofer_wizard.asp)

For example, if you have 1 (4 ohm) sub, then the amp will show a 4 ohm load, pretty self explanitory. If you have 2 (4 ohm) subs, connected to a 1 channel (mono) amp then impedance is either halfed or double (depending on how it is wired), the above link will show you how to wire a sub to either half or double the impedance, so it either becomes a 2ohm or 8 ohm load that the amp shows.

http://www.rockfordfosgate.com/rftech/woofer_wizard/2_4ohmSVC_2ohm.gif
http://www.rockfordfosgate.com/rftech/woofer_wizard/2_4ohmSVC_8ohm.gif

It's the same if you have 2 (2 ohm, 1 ohm ) subs etc. As i'm sure you can now work out, if you were to have 4 (4 ohm) subs, the impedance would either be quatered or equal the orignal impedance (which would be 4 ohm). So it would show either a 1 ohm or 4 ohm load. The lower the impedance the more power can be produced.

http://www.rockfordfosgate.com/rftech/woofer_wizard/4_4ohmSVC_1ohm.gif
http://www.rockfordfosgate.com/rftech/woofer_wizard/4_4ohmSVC_4ohm.gif

Now when working with DVC subs it becomes what looks to be more tricky. But really wiring a DVC sub upto an amp is the same as wiring 2 of the same sub up to an amp. If the sub is DVC with a 4 ohm impedance, when wired, the amp will show again, 2 or 8 ohm.

http://www.rockfordfosgate.com/rftech/woofer_wizard/1_4ohmDVC_2ohm.gif
http://www.rockfordfosgate.com/rftech/woofer_wizard/1_4ohmDVC_8ohm.gif

Component speakers are exactly the same, but they will only come in SVC. So a 2 ohm speaker will show 2 ohm, and 4 ohm will show 4 ohm etc...

So to finish up, going by the amp that you have posted the specs for. If you have 2 subs that were SVC 2 ohm, you could wire 1 to each channel of the amp, and each channel would produce 300w. If the subs were 4 ohm and you wired them exactly the same each channel would produce 180w. Multi channel amps like the one you given the specs for work in exactly the same way. Just imagine each channel is the same as a single channel on a Mono amp.

Understanding impedances involves quite a bit of reading, another site that would be a good idea for you to check is Talk Audio (http://www.talkaudio.co.uk/vbb/index.php?). Use the search and search for "impedances". If you still can't make head or tails of it all make a post and you'll have some very experienced and pleasant members help you out.