Author Topic: Help with understanding an amplifier (Read 4937 times)

SmootH · « **on:** Jun 26, 2003, 10:28AM »

hey everyone, just wondering, with power ratings on amps, wat does it mean when it says 1 x 200w at 4 ohms and 1 x 400w at 2 ohms, ive put amps into cars before and done it all myself, but have never understood all the detail.
Also anyone help me out pls, im looking to find 2 new amps or one single, preferably 2 to run 2 soundstream spl 12" subs, anyone know of a good amp, they are 300w peak, im guessing in rms.

cheers:)

aussie-gli · « **Reply #1 on:** Jun 26, 2003, 02:53PM »

What they mean by that is the load you are connecting to the amp. Eg, you might bridge two channels to run a sub, If you look at your speaker you'll find it's 4 ohm... so you are connecting a 4 ohm load to the amp... If the amp is 2 ohm stable, it means you can increase the load on the amp to 2 ohms, (lower resistance means increased load).... so, if you connect 2 subs in parrallel, you'll achieve a load of 2 ohms. So twice the sound out of the same amp!!

Remember back to year 11 physics...

Resistors in series Rtotoal = R1 + R2 ....+ Rn

Resistors in parrallel 1/Rtotal = 1/R1 + 1/R2 ..., +1/Rn

So for two subs connected in parrallel:

1/Rtotal = 1/4 + 1/4
1/Rtotal = 2/4
1/Rtotal = 1/2
Rtotal = 2 Ohms

So if your amp is 1 x 400w at 2 ohms you can run the two 12" subs off it...

SmootH · « **Reply #2 on:** Jun 27, 2003, 02:15PM »

im sorry buddy, but not all that makes sense to me, ands its very hard for me to remember back to school lol, ok
basically, im not getting enough out of the amp im running and i want to get possibly 2 single amps to run either sub, so, if i went the coustic way with amps, say a 1 x 400 watt amp either sub, would i have a problem, the subs are 300watts peak each, or could u reccommend something that would run these, something decent but not overly expensive.

Thanks for your time, appreciate it!!!

Tim-E · « **Reply #3 on:** Jun 27, 2003, 06:43PM »

i somehow passed physics in high school but i am not even going to attempt to understand what u just said aussie.

the theory behind audio components goes 100% completely over my head

BlakeyBoyR · « **Reply #4 on:** Jun 30, 2003, 02:17AM »

Its all dutch to me mate ! I dont get it either :/

aussie-gli · « **Reply #5 on:** Jun 30, 2003, 10:40AM »

Quote from: SmootH on Jun 27, 2003, 02:15PM

i want to get possibly 2 single amps to run either sub, so, if i went the coustic way with amps, say a 1 x 400 watt amp either sub, would i have a problem, the subs are 300watts peak each

You don't need 2 amps to run 2 subs. You could use a 2 channel amp (1 channel per sub OR bridged at 2 ohm), or you could get a 4 channel amp.

Eg, here are the specs for the 4X100Wrms Jaycar Amp

Specifications:
- Power/channel @ 4 ohms 100WRMS x 4
- Power/channel @ 2 ohms 150WRMS x 4
- Power/channel bridged @ 4 ohms 300WRMS x 2

Lets say u used the amp above, you would use two bridged channels running at four ohms to run the 2 subs. In the case of this amp, you'd end up with 300WRMS per sub.

James · « **Reply #6 on:** Jun 30, 2003, 09:50PM »

or u could also use a single monobloc sub amp

it would of course depend how many ohms ur subs are though...

SmootH · « **Reply #7 on:** Jul 1, 2003, 02:14AM »

im getting there
thanks 4 the help guys

cheers:)

James · « **Reply #8 on:** Jul 1, 2003, 10:49PM »

okay, as u add subs to ur amp, u alter the resistance (measured in ohms).

for example, one 4ohm sub is giving 4ohms of resistance. so the lower the resistance, the more power the amp is putting out. this is why u see and amp giving 500wrms at 4ohm and 800wrms or so at 2 ohm

less resistance equals more power. that is the important thing to understand.

if you add another sub so that you have TWO 4 ohm subs, then the resistance is halved presenting the amp with a total load of 2 ohms. so if the amp runs 800wrms at 2 ohm, then each sub is getting 400wrms.

that is assuming the subs are wire in parrallel. meaning that both the +'s on the subs connect to the +'s on your amp.

hope it sorta clears things up for you champ. let us know if u need any more explaining

ZEXTCY · « **Reply #9 on:** Jul 3, 2003, 08:46PM »

just don`t do what i did and bridge an amp down to 1/2 ohm
worked well for lil while but in the end got fried BIGTIME

BlakeyBoyR · « **Reply #10 on:** Jul 6, 2003, 05:30PM »

So why dont people just run at 2ohms all the time ? What happens to the amp if you do ?

Nizzan · « **Reply #11 on:** Jul 6, 2003, 09:52PM »

ahh becoz the amp gets mega hot!

theres little resistance of the charge going thru, so the flow is faster in a way. Its too fast if the amp cant handle it and so it can fry!

James · « **Reply #12 on:** Jul 7, 2003, 11:13PM »

depends on ur amp though

see monobloc sub amps will usually run best at 2 or 1 ohm

my alpine amp runs down to 0.32ohm i think it says

thats pretty crazy!

most amps will run at 2ohm but it is generally a case of getting it all wired to run that way

BlakeyBoyR · « **Reply #13 on:** Jul 8, 2003, 02:54AM »

So its simply a matter of trying to keep the amp cool when its running at 2ohm ?

weasel · « **Reply #14 on:** Jul 8, 2003, 06:08PM »

Pretty much BlakeyBoy but theres no real need to worry about it, if the amp is designed to run at 2 ohm then the manufacturers would have tested it all out before putting it on the shelves well they should have anyway (hence why alot of amps have fans in them now)
And it'll be mounted in your car so the air temp isn't gonna be too hot while you're listening to it, even if it's mounted in the boot there is still alot of airflow through your boot and this air will be the cold air that rushes against your car as you drive.

Also another reason why ppl don't run at 2 ohms is that with lower quality subs i.e. single voice coil (as compared to the equvalent sub in dual*format) the bass can become dirty sounding as there is not enough resistance to filter out some of the line noise and interference.

so it basically depends what you want LOUD bass (2 ohm) or Quality bass (4 ohm)

me personally i have my two duals running at 2 ohm so i get a little less quality than what i would in 4 ohm (it wouldn't be any less than what a single would be at 4 ohm) but i get a shitload more volume out of them than i would in 4 ohm

hope thats helped and not made things worse

cheers >weasel<

*Dual voice coil subs

James · « **Reply #15 on:** Jul 8, 2003, 10:02PM »

spot on weasel, that is why i am looking at an extremely efficient 4ohm sub

i have my eyes on a focal utopia

weasel · « **Reply #16 on:** Jul 8, 2003, 11:47PM »

Ok time for a public whipping..... I've never even heard of the Focal range

i assume from how everyone keeps raving about them that they are and awesome speaker but where do you guys find the stuff, i just want to listen to some of the gear so i can understand what you are all on about

cheers >weasel<

BlakeyBoyR · « **Reply #17 on:** Jul 9, 2003, 02:46AM »

Focal from what I know are very very expensive ! And thanks for the explanations guys you rock

fmx_rider · « **Reply #18 on:** Jul 9, 2003, 11:26AM »

Focal, like most of the brands (eg alpine, JL) have a range to suit most peoples budget...I like their polyglass (I think from memory) range splits-about $350 to $450 last time I was looking....but the utopia range is the top at more than $800. The utopia subs are expensive as they are focals best, think about $1100 for the 13 inch model (not 100% sure though).

Most decent amps (not budget bargains) are stable at 2 ohm, many quality or sub-only amps are stable to 1ohm or less. Two channels on my amp run 2 speakers at 2 ohm, while the other two channels are bridged for the sub at 4ohm, worked fine for about 3 years now.

James · « **Reply #19 on:** Jul 9, 2003, 07:05PM »

i first heard focal gear at northfeild, when i bought my current stereo. they sound absolutly wicked. as fmx_rider said, they make both high end (utopia) and budget (polyflex???) gear. i have listened to a freinds 3 way polyglass splits (mid range quality i think) and they are some of the nicest sounding speakers i have ever heard! that is what helped influence my decision to save for utopia 3 way splits ($1400!!!!) and the focal uptopia subs reputation is outstanding, although i intend to hear one before purchasing

due to there $1350 price tag for the 13" version! but yeah, u can get focal splits for around $499, so they are not ONLY high budget gear

BlakeyBoyR · « **Reply #20 on:** Jul 11, 2003, 01:40AM »

Whoa, to me $500 isnt cheap dude

James · « **Reply #21 on:** Jul 12, 2003, 12:15PM »

hehe, but compared to $1340

or even close to $4000 for the alpine F1 3 ways. yeah it isnt cheap but it will sound alot better than say clarion 2 ways for the same price. no offence to anyone with clarion splits

Author Topic: Help with understanding an amplifier (Read 4937 times)

BlakeyBoyR

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