Questionwell, your calculation is a little off. The wattage per channel basically does double when cuting the ohms in half so an amp capable of 100x2@4ohms will roughly double to 200x2 when running at 2 ohms IF IT SUPPORTS running a 2 ohm load. BUT when you bridge the amp the minimum stable ohms that the amp can support goes up by a factor of 2 as well. so if the amp only supports 2 ohms in STEREO mode it will only support 4 ohms in BRIDGED mode. if the amp supports 4 ohms in stereo mode, it will only support 8 ohms in bridged mode. if you reverse engineer that, for the amp to support a 2 ohm load in BRIDGED mode it would have to be 1 ohm stable in STEREO mode. make sense? so when an amp is rated for 200x2 @2ohms it's correct that it says 400x1 @4ohms and yes it would put out roughly 800x1 at 2 ohms IF its stable at 2 ohms bridged or 1 ohm stereo but most amps arent. the other thing to remember is that the lowwer number ohms means a higher load on the amplifier, meaning it has to work harder. this usually means it will run hotter, distort more, be less efficient etc. most amps will not exactly double when the ohms are cut in half in fact most amps are rated as something like:
180x2 @4 ohms
230x2 @2 ohms
460x1 @4 ohms
a cheap amp will barely make any more power when dropping ohms but a good amp will come very close to doubling when droping ohms. its sometimes a good sign of a cheap or good amp as long as the figures are reliable.
as for running the speakers, you divide the power between the speakers, in the case of this amplifier again:
180x2 @4 ohms
230x2 @2 ohms
460x1 @4 ohms
if you put 1 set of 4 ohm speaker on this amp (1 left, 1 right, in stereo mode) the amp will put out 180x2 @4 ohms so each speaker will get 180 watts.
if you put 2 sets of 4 ohm speaker on the same amp (2 lefts in parallel, 2 rights in parallel. then the amp will put out its rated 230x2 @2 ohms so you divide each channel's power going to the speakers so each spaker will get 115 watts (230 watts divided by the 2 speakers on the left and 230 divided by the 2 speakers on the right)
as for the sub, there's alot of factors, the brand definatly has alot to do with it but believe it or not you can blow a sub with too little power just as easily as you can blow a sub with too much power. this is because a small amp when turned up will do something called "clip" which is very damaging to a speaker. the bigger amp will clip at a higher volume so you are less likely to turn it up that high and make it clip. this clipping sounds like distortion to your ear, so the basic rule of thumb is match the amp to the sub, if the sub is rated for 500 watts RMS, get an amp rated for 500 watts RMS. You should always listen for distortion since clipping will kill a sub no matter how small or large your amp is. The box the sub is in has alot to do with it as well. if the box is a small sealed box you can run a little higher watts, if the box is a large ported box you can go a little lowwer wattage but it depends on the port frequency then. its complicated, so really stick to the basic rule of matching the RMS power.
Great talking with you and let me know if I can be of more help. please feel free to write back if I need to clear anything up there.
hey thanx a million for that mate its taken me ages to get those answers by the way thanx once more for the fast reply. just one thing more if that sweet man, i had been running a dvc sub in parallel on a 2 channel amp being bridged (both rockford) correct me if im wrong but i considered the amp to be running at 2ohms bridged, you mentioned that when bridged most amps are 4ohm stable does that mean i was straining my amp the whole time or? plus since i sold may stereo and am now planning to get back into it i still have the same sub and im planning on buying another amp to run it but im not really seeing amps that have a 2ohm rating when bridged (because im planning on bridging and parallel running the sub) should i keep looking for ones that do handle 2ohms bridged or can u make most amps run at 2ohms bridged with out to much trouble (i take it thats not a good idea) or should i just run it at 8ohms which i would like to avoid. another 2 quick questions you dont have to answer if you dont want. im thinking of running 3 quite full loaded amps 1 for speakers 2 for 1 sub each should i be putting in a second battery and what not or could 2 capacitor be sufficient. and where did you get all you’ll knowledge from just playin with it and looking into it or is there another more comprehensive source. thanx mate
AnswerI'd be happy to recomend you an amp or 2 and let you know if you were straining your old amp but you never told me the make and model of the sub you were running, or what the ohms of the coils were. if it was a dual 8 ohm sub then putting it in paralell would turn it into a 4 ohm mono load which would be fine for most amps to run in bridged mode. but if it was a dual 4 ohm sub then that would require an amp that was 1 ohm stable in stereo and 2 ohm stable in bridged which you're right, isnt too common.
let me know what sub we're talking about here and I'll match you up a great amp. you know you dont have to go with a 2 channel amp and bridge it, you can get a mono amp that's made to run 2 ohms OR (if the sub is a dual 4 ohm sub) put the coils in series for an 8 ohm load and use a 2 channel amp in bridged mode. this will run the amp the same wattage as a 4 ohm stereo load. The advantage of doing it this way is that the amplifier will run cooler and the sound will be cleaner.
as for the 3 amps and wether you need a 2nd battery or caps, it's all a matter of how much current it all draws and how good your alterator is and what gauge of wire you run. etc. How about we plan something out together, top to bottom, I'd be happy to do that for you.
Just let me know what your intrests are (in music), your box building abilities (experience if you've built them before) what vehicle you have, and of course your budget and I'll put something together for you. sound like fun? as for the exeperience I was into electronics long before I was into audio, so I learned all about electricity (amps, ohms, volts, powerfactor, phase, etc) I was also into physics and math so when I discovered audio it all came together and made sense I guess. I built alot of stuff that sucked and wasted alot of money and time but in doing so I learned ALOT and mostly through trial and error, and research on my own and from others I've honed my skills a bit. that's about it. Thanks for asking!
If you're seriously interested in designing a system send me a private message (with the answers to the questions I gave above) and your personal email address and we'll work together on it.
Hope to hear from you soon.
