Yet another stereo system question

[Fat Chance]

Ok, so you have an amp That is rate at, lets say 75 watts X 4 channels @ 4 ohm load (RMS), and 150X4 @ 2 Ohms. Now you get to Ohms by running 2 4 Ohm SCV speakers in parallel per channel, correct?? ...and does each speaker see 150 watts, or does each channel split the power, thus each speaker seeing 75 watts RMS?? :rolleyes:
Thx!!!
Scott

[rivercrazy]

If you were talking about a 2 channel amp, this is all doable (i.e. two 4 ohm speakers per channel wired in parallel). And when an amp sees a 2 ohm versus 4 ohm load it puts out almost 2X the power. If you had two 4 ohm speakers wired in parallel, the power is split equally between the two. For example if you had a 2 channel amp that puts out 2 x 100 at 4 ohms it would put out 100 to each speaker. If you had it wired 2 ohm to two 4 ohm speakers (per channel stereo), the amp would put out about 200 watts to each channel so each speaker sees 100 watts.
But on a 4 channel you cannot. The ohm load would be below 2 ohm and I don't know of many amps out there that can either handle that ohm load or have dual power supplies internally.
[ May 21, 2003, 06:27 PM: Message edited by: rivercrazy ]

[Havasu Hangin']

If each speaker is 4 ohms, then one speaker per channel is a 4 ohm load.
75 x 4 = 300 watts
If you have 8 speakers, and wire two 4 ohm speakers in parallel for each channel, then that is a 2 ohm load in the amp.
150 x 4 = 600 watts.
Because the amp is "seeing" less resistance, the output has doubled. The "ohm load" on the amp is like the throttle plates on a carb...less resistance means more power output. The key is not to cook (overrev) the amp...some amps can handle lower ohm loads better than others.
In parallel, if each speaker is rated the same resistance, they split the output. So in each of the above situations, the speaker will "see" 75 watts.
Did I confuse you enough?

[Fat Chance]

I have a couple 4 channel amps, most recently a new Kicker...and they refer to amp 1 (2 channels) and amp 2 (2 channels) and they claim is is totally 2 ohm stable...so don't you just double the load on each channel with 4 ohm speakers to getchya 2 ohms?

[Fat Chance]

Thanks HH, perfectly clear. Thats what I assumed.
I have 8 4 ohm speakers wired in parallel to 4 channels, and I wasn't sure each speaker was see'n 150W or 75W...Thanks for clear'n that up.
Scott
[ May 21, 2003, 09:15 PM: Message edited by: Fat Chance ]

[mbrown2]

rivercrazy:
But on a 4 channel you cannot. The ohm load would be below 2 ohm and I don't know of many amps out there that can either handle that ohm load or have dual power supplies internally. There are some amps that can do this; like the Xtant 604; 75x4 @ 4ohms, 150x4 @ 2ohms

[Havasu Hangin']

Fat Chance:
...so don't you just double the load on each channel with 4 ohm speakers to getchya 2 ohms? Yes...if they are 4 ohm speakers.
But what if one speaker is 8 ohm (Speaker A) and one is 4 ohm (Speaker B)?
In parallel (each speaker recieves the same voltage)
(Speaker A x Speaker B)/(Speaker A + Speaker B)
8 x 4 = 32 divided by 8 + 4 = 12
2.666 load on the amp
In series, the speaker share the same voltage, you just add the resistance.
My math is a little rusty...

[Frosty_pop]

Keep in mind that the lower you bridge down your speakers for more volume...the more distortion you will get your sound will be. IE: those punk kids in their "racing" rice rockets, who bridge down cheap amps to get more sound.... sounds like real loud shit.....
[ May 21, 2003, 07:37 PM: Message edited by: Frosty_pop ]

[BlownHowardCat]

Not to mention that the amps will run hotter and maybe shorten the life span of the amp....I run live sound for bands and all my amps are 2 ohm stable but i never run them lower than 4 ohms I ran a couple of them at 2 ohms in a pinch a few times and you could actually feel that they were running hotter than usual. I realize theres a difference between pro audio and car/boat stuff but I think the idea is the same.BTW I'm running sound for the Mighty Mighty Bosstones tomorrow if you remember them.I'm going to be runnig 12,125 watts for the front of house spkrs. can ya feel the power ? Just my .02 cents
Kenny

[Havasu Hangin']

Well...I'm not as hip on equipment these days as I used to be, but an exception would be JL Audio amps (http://www.jlaudio.com/amps/4504.html), which have the same output at 1.5 to 4 ohms. Good stuff.
BTW...it's debatable, but most audiophiles agree that .20% THD and below can't be heard by the human ear....let alone in a boat, that has no accoustics.
Most of the loud, cheap systems I've seen have distortion caused by amps clipping with the gains turned up ('cause they couldn't afford the bigger "bling bling" amp), not a lower ohm load, which will instantly melt poor quality equipment.
My 1200 watt class D sub amp is very happy at 1 ohm mono...so times are a changin'...
[ May 21, 2003, 08:18 PM: Message edited by: Havasu Hangin' ]

[77charger]

mbrown2:
rivercrazy:
But on a 4 channel you cannot. The ohm load would be below 2 ohm and I don't know of many amps out there that can either handle that ohm load or have dual power supplies internally. There are some amps that can do this; like the Xtant 604; 75x4 @ 4ohms, 150x4 @ 2ohms And i have one :) :) (thanks roz)I run 4 6x9s off the front channels and a sub bridged on the rear channels

[ROZ]

Havasu Hangin':
Well...I'm not as hip on equipment these days as I used to be, but an exception would be JL Audio amps (http://www.jlaudio.com/amps/4504.html), which have the same output at 1.5 to 4 ohms. Good stuff.
BTW...it's debatable, but most audiophiles agree that .20% THD and below can't be heard by the human ear....let alone in a boat, that has no accoustics.
Most of the loud, cheap systems I've seen have distortion caused by amps clipping with the gains turned up ('cause they couldn't afford the bigger "bling bling" amp), not a lower ohm load, which will instantly melt poor quality equipment.
My 1200 watt class D sub amp is very happy at 1 ohm mono...so times are a changin'... Yup, the only thing that changes the output of the JL amps is the voltage and your fuse size. Minimum you'll see is the rated power. smile_sp
HH, you have a couple seasons at 1 ohm, don't you? :cool:
Yes Sir, times are a changin...Now if you can only get that Tom Brown to..... :rolleyes:
Kicker rates their amps at 14.4, so you'll see less power at 12v....And they are 2ohm stable. The 1200.1 is 1 ohm stable. I know a guy with one running a pair of 10l7's in his tundra. It's rocked for 2 years without a hitch..
[ May 21, 2003, 08:55 PM: Message edited by: ROZ ]

[TroubIeOnWater]

Havasu Hangin':
Well...I'm not as hip on equipment these days as I used to be, but an exception would be JL Audio amps (http://www.jlaudio.com/amps/4504.html), which have the same output at 1.5 to 4 ohms. Good stuff.
BTW...it's debatable, but most audiophiles agree that .20% THD and below can't be heard by the human ear....let alone in a boat, that has no accoustics.
Most of the loud, cheap systems I've seen have distortion caused by amps clipping with the gains turned up ('cause they couldn't afford the bigger "bling bling" amp), not a lower ohm load, which will instantly melt poor quality equipment.
My 1200 watt class D sub amp is very happy at 1 ohm mono...so times are a changin'... How did you get a 1 ohm load out of a mono block amp? 2 ohm woofers paralleled or something?
Also I always see people forgetting to add something into the equation when doing systems. When you bridge an amp you cut the resistance in half. So whatever you have at the woofers is cut in half on a bridged amp unless it is a mono block.
For Example. I have a dual 4 ohm voice coil Memphis audio 12 in my rig. I have it paralleled to run at 2 ohms. If I were to put that on a standard two channel amp the amp would actually see 1 ohm and over heat. I am running a Class D mono block amp so the cut in half principal doesnt apply and the amp is operating at 2 ohm's.
And just for refference for those who need visual aid i will do a diagram as best as i can to explain parallel wiring.
Here we have 8 ohm woofers. Paralleled
8ohm 8ohm
Speak1 Speak2
+ - + -
l l l l
l l _ l _l
l______l l
l l
l l <----4 ohm
+ -
Bridged Stereo Amp
2 ohm load
I dunno if this makes sense but it is the best I can do with l's and + and - signs

[Fat Chance]

I see alot of amps rate at 14.4...how may more 6V batteries do I gotta buy!!! :D
Is 14.4 typical for competition? What's the dealio?

[TroubIeOnWater]

Fat Chance:
I see alot of amps rate at 14.4...how may more 6V batteries do I gotta buy!!! :D
Is 14.4 typical for competition? What's the dealio? When your car is reving or boat for that matter the alternator is allowing the battery to put a current stronger then 12 volts more like 14.4 volts. Fosgate use to actually rate their amps at 16 volts but your will very rarely ever see that much voltage.
And as far as the diagram i did goes just ignore it it looked good when i was making it but something is ****ed in the way this system spaced out letters and ****ed it all up.

[Fat Chance]

If you go to Audiobahn (http://www.audiobahn.com) and click on tech support (as I recall), they have a bunch of diagrams on wiring schematics for just about any combo, series, parallel, 2 ohm, 4 ohm, etc. not a plug for audiobahn, just a helpful site.
[ May 21, 2003, 09:28 PM: Message edited by: Fat Chance ]

[rivercrazy]

The quickest way Ive seen to melt an amp is to hook up 8 4ohm speakers to a 4 channel amp. A 4 channel amp already runs hot at 4 ohm. Double the speakers and the risk of melt down increases substantially.
One way of getting a 1 ohm load on a sub amp is to hook up four 4ohm subwoofers wired in parallel. I know a few guys runing this set up (including me) and my class D amp never even runs hot.
[ May 21, 2003, 09:32 PM: Message edited by: rivercrazy ]

[Fat Chance]

I've run my Kenwood 4 Channel 2 seasons, and at volume it would get hot as a piston...but it also relied on passive cooling. It would also go into thermal shut down after 30 or 40 minutes if you ran it high volume. I'm thinking this new Kicker, with active cooling and 2 ohm stability will work a little better.

[Havasu Hangin']

TroubIeOnWater:
How did you get a 1 ohm load out of a mono block amp?Four 4-ohm subs.
TroubIeOnWater:
Fosgate use to actually rate their amps at 16 volts but your will very rarely ever see that much voltage.Maybe they expect you to buy those 16volt batteries?
[ May 22, 2003, 04:46 AM: Message edited by: Havasu Hangin' ]