amps and speakers

i have this headunit that says it sends 40X4 on the faceplate. does this mean it sends 40 Watts for each speaker no matter what? is there a way to send less watts? cause the front speakers can only hold 2-20W RMS. the peak power handling is 80 watts. if i just use these speakers, will i blow them?

the 40X4 power rating is referring to peak power. your headunit prolly puts out around 20-22 watts RMS. those speakers should be fine.

if i get an amp that says 150X2 RMS. that means its going to run at 150 constant power right? if it just says 150X2 then thats just peak power?

if the amp says 150 X 2 it means 150 max. They always give you Peak power, even though RMS is the more important one.

if i have substhat can handle 600W max, and the rated input power is 150W, will i be going under the rated input power if i use that 150X2? i want to get the most out of my subs.

Well, you'd be under the max wattage they can hold, but they will stilll work. the only way to increase the watts goin to them is to get another amp.

"if i get an amp that says 150X2 RMS."

if it says RMS then it's RMS. and if it's x 2, then one would assume 150 RMS per channel, thus, 300 watts RMS of power.

if it says 150 X 2 RMS then yeah, thats 300 total RMS power. but if that were true, the amp would be over 1000 watts max power. Usually, when you see amps out there, they always show you peak power in big letters, and its usually a round number, like, 300 watt. To find RMS power, you put peak power through some wacky equation I can't tihnk of at the top of my head. like my head unit is 50 watt peak power, and on the head unit, it says, "50X4" but the actual RMS power is 22 watts per channel

I hope I dont get chewed out by any audiophiles for this.


To get a rough estimation of RMS power, its usuially 2/3 of the peak.

Example. A deck with 45x4 power is going to be around 30x4 RMS


Remember this is just a rough estimation that I just use when shopping for an amp and they usuially just say the peak power on them. If there are no sales persons around its close enough just to figure 2/3 as the RMS power.

Hope it helps.

I would say less than 2/3. more like 1/2 or lower.

Yes, usually %50 or lower.

Example: 300watt max power
would be: 150watt RMS power Typically

Though the less quality of the amp, the more the percentage goes up!

Um, if memory serves me right, the RMS power of an amp is a direct funtion of its efficiency. Take for instance my MTX 500D can produce a maximum power output of (75 amps x 14.4 V) 1080 watts. With a 91 % efficiency it puts out a real 984 watts of power. The rest is wasted as heat. Now the real trick is finding out its efficiency rating.

Originally posted by lloyd_nickens
Um, if memory serves me right, the RMS power of an amp is a direct funtion of its efficiency. Now the real trick is finding out its efficiency rating.

Yes, you are right. I just posted before because depending on the product, it can be hard to find the efficiency rating, so I figured some other way would be ok even tho its less accurate.

Just go with a Class D amp :D
anyway guys
IMHO there are not many cases that you will over power a speaker
in fact in most cases it is "underpowering" which will cause a speaker to give up.
as for worrying that too much power could be going into a speaker...well don't look at the power that they "claimed" can handle...most of the times they are unaccurate.
Just run as much clean power into it as you can...you WILL know when you are over powering a speaker... if so..you can always turn the gain down
and i would say it is still better than underpowering hence distorting the speaker

:)

well basically i want to get the best out of my speakers without blowing them. but just say your peak power on the amp is over the maximum wattage the subs can handle, it will blow if i turn it up too much right? wouldnt it be safer if i kept the peak power of the amp right at the maximum power of the subs? for example...

here is my subs...
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1288338321

and here is an amp i want...
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1296687752

and basically ill be running only about 75X2 RMS wattage? can i get a bigger amp without chance of blowing it?

Okay, get the biggest amp you can afford. That way when it is tuned to your system you can use the gain as a rca voltage matcher (like it was meant for) not as a volume control. When your amp can produce more power than your subs are supposed to be able to handle you find yourself not having to turn your radio up as loud to get the same amount of bass. And please get a class D amp. your electrical system will thank you for it.

how can you tell if its a Class D amp or not? and basically, the more power the amp puts out, the less ill have to turn it up. what kind of amp would you recommend? something thats affordable and yet powerful. something around 600-800 watt amp.

there aren't too many class D amps out there in the market yet i think
if i was to go class D rockford's Class BD would be my ultimate choice

how can you tell if its a Class D amp or not?

well you can't really "tell" if an amp is Class D or not by just looking at it...unless you are an Electrical Engineer :p
but if you have a chance to see one i am sure you it will be written somewhere in the mannual or something
Class D amps are monoblocks and can only run subs(low freq)

and basically, the more power the amp puts out, the less ill have to turn it up

yes in a way...but the main reason behind this is so you can keep the gain settings on your amp as low as possible to achieve the same SPL or power output you could say.... say if you have a 500rms amp, and a crappy 1 -2V rca head unit..if you want to run ALL that 500rms into a sub...you will have to turn the gain right up...and most possibly your volume control too....and hell....you wouldn't want this...you will pick up so much hissing noise

what kind of amp would you recommend? something thats affordable and yet powerful. something around 600-800 watt amp.

this is very subjective... and it depends on the price range
you after a 2 channel amp? or a 4 channel? what is the amp going to be running...are you after the perfect SQ or horrible SPL.. blah blah blah...you really need to take these into account b4 any decisions could be made

but just remember one thing
dont buy crappy brands ... they often overrrate their power by quite a fair bit while good brands tend to underrate their power, also they wouldn't last

I personally is a big fan of Phoenix Gold (http://www.phoenixgold.com)

Originally posted by pche059


yes in a way...but the main reason behind this is so you can keep the gain settings on your amp as low as possible to achieve the same SPL or power output you could say.... say if you have a 500rms amp, and a crappy 1 -2V rca head unit..if you want to run ALL that 500rms into a sub...you will have to turn the gain right up...and most possibly your volume control too....and hell....you wouldn't want this...you will pick up so much hissing noise

this is very subjective... and it depends on the price range
you after a 2 channel amp? or a 4 channel? what is the amp going to be running...are you after the perfect SQ or horrible SPL.. blah blah blah...you really need to take these into account b4 any decisions could be made


gain, as in how much power goes into something? 2 channel and 4 channel means how many different things its powering right? if i just want to power 2 subs, i would want a 2 channel? if i was say, powering 2 subs and 2 speakers, id want a 4 channel? SQ and SPL, what do each stand for, SQ i figure is Sound Quality, SPL is Sound Power Load?

Um, as I said b4 gain is not a form of volume control. It allows you to match the voltage that the head puts out at a given volume to the optimal input of the amp. That is why the more power your amp has the less you have to turn the volume up. The best bang for the buck is MTX class D. The amp that I have (its equal is this years 6500D) puts out around 984 watts of power. I have one Diamond Audio M5 series 12 in a ported box. It gets really loud. The neat thing is the sub is rated for 500 watts of power. When I get a musical spike it can get up to 1300 watts of power. (The amp will pull more amps than the fuse is rated at if it needs the power. If it pulls double the fuse rating the the fuses blow) I get all that from a lowly 250 watt rms rated amp. :D Rockford does the same thing but they are way more expensive, and if you don't get the power series you are wasting money. ;)

hmm i think that MTX Amp sounds too much than my subs can handle. my subs are rated at 150W RMS. would an 800W class D amp be sufficient? or does class D only come in higher wattage?

as i said before don't worry about having too much power
it works like this
the power from the amp is like the power from your engine
you can have a 1000hp in hand...but it doesn't mean that you will have to run your car at 1000hp all the time...
it just means that it will be there when you need it.....
it's a lot easier for an engine that is built for 1000hp to make 200hp than a engine that is built for 200hp to make 200hp...and it is impossible for an engine that is built for 190 hp to make 200hp

see my point here?
get a good amp now...
so later if you need more power (eg if you wanna up grade your subs) you don't need to buy a new engine (amp)

ya i understand, good analogy :D but 980W RMS? :eek: that sounds like i wont even have to turn it a nitch to even get power. wouldnt mind, but knowing me, i have a habit of turning it really loud even though its already deafening. i want something more toned down, but with power like an 800 watt amp. isnt Kenwood one of the top leading brands of amps? well not compared to audiobanh or others like that, but it does pack a punch? :confused:

Personally, I would get a 1 channel class D amp and run it in parallel.
I say 1 channel because some are stable at 2 ohms and sometimes 1 ohms.
I would recomment the JBL 1200 amp.
It puts out good clean power, doesnt suck too much power, but maybe is too much power for your tastes. I would recommend either looking at some that everyone else recommended or go with something like the RF bd1000.1 which is what I have or maybe a 800.2 amp.

is it possible to run a 1 channel amp and just bridge the subs? would it sound better or worse than a 2 channel amp? did you mean wire them in series, not parallel? higher resistance causes more static right?

is it possible to run a 1 channel amp and just bridge the subs?

hehe 1 channel amp is called a monoblock
these amps are built only for subs, and what's so special about them?
they can usually handle ultra low impedence
you can often run 4 4ohm subs in parallel (the amp will see it as a one ohm load) and it will still continue to "double" the power (i know i am getting into something new here, just apply the fomulae V= IR , where V is constant, when R (impedence) decreases, I (current) increases. P=VI, V is constant, when I (Current) increases , total power increases)
and this is why you should buy amps that can handle the low impedence

would it sound better or worse than a 2 channel amp?

well for a sub i don't think there will be too much if any difference, in order to make a sub sound good all you will need is a good powerfull amp, good subs and definitely a good box for the subs. :D aye...


btw SQ is the abbreviation of Sound Quality and SPL is Sound Pressure Level (DB drag measurement unit)
:D

Originally posted by pche059


hehe 1 channel amp is called a monoblock
these amps are built only for subs, and what's so special about them?
they can usually handle ultra low impedence
you can often run 4 4ohm subs in parallel (the amp will see it as a one ohm load) and it will still continue to "double" the power (i know i am getting into something new here, just apply the fomulae V= IR , where V is constant, when R (impedence) decreases, I (current) increases. P=VI, V is constant, when I (Current) increases , total power increases)
and this is why you should buy amps that can handle the low impedence


hm that is strange, the higher the impedence, the higher the power? just learned that equation, V=IR, today in auto :D but if you think about it practically, lower the resistance, higher the power flow, this is stumping? how can you run a monoblock parallel? dont you mean series?

hm that is strange, the higher the impedence, the higher the power?

i don't think i ever said that...and no that is not true

just learned that equation, V=IR, today in auto but if you think about it practically, lower the resistance, higher the power flow, this is stumping?

ok..you are right here. Since V= IR , and voltage is the power supply to the amp, it is a constant figure. ok...do some maths here.... because V is constant, if R(impedence) decreases, the I (current) will have to increase to keep that V a constant. And this is the same that if impedence goes up, then the current will reduce to keep the V constant.

So you are right, lower the resistance, then higher the power flow ( in this case power flow is the current)

ok why does more current make more power? you use this formulae here P = VI, where P = power, V = voltage and I = current.
As i said before, voltage is constant, you cannot change it, so if the I (current) value goes up, so would the power P.

Is it better now?

how can you run a monoblock parallel? dont you mean series?

hm....you run your subs in series...you will increase your impedence
so no i didn't mean series

of coz you can still run a monoblock parallel,
a monoblock still has one +ve and one -ve terminal,
just connect the +ve sides of the subs to the +ve output of the amp and connect the -ve sides of the subs to the -ve output of the amp

there you go :D

is it safe to run a monoblock in parallel? i know the amp wasnt meant for that. and that in a sense would lower the impedence? ok im getting this now :D finally! :p thanks for the explaining.

The majority of class D amps are monoblock and they are generally designed to run low impedences. And in order to get those low impedences you would have to either buy a one or two ohm sub and run it by itself (yeah right, unless you have orion hcca which has dual 2 ohm coils), or you could buy a bunch of 3, 4, or 8 ohm woofers and wire them in parallel to get 2 or 1 ohms. Oh yeah and one last thing, if you want an amp that doubles output at lower impedences get one with an unregulated power supply. They are the ones that usually double output when given a low impedence. You should go to SoundDomain.com (http://forum.sounddomain.com) and read a few of the post. Its really enlightening stuff. :D

my subs are single 4-layer 4-ohm voice coils so if i wire mine parallel to a monoblock, it will go down to 2 ohms?

Yes, 2 ohms.
Monoblocks are made specifically for subs, therefor are made for low impedence.
Make sure before you buy them though, that they can handle a 2ohm load or possibly even a 1 ohm load.

well after thinking about it for a while, i think im going with the MTX Thunder Class D 6500D amp. how would i go about making it 14.4 V? i see there is a power rating for both 12 and 14.4 volts. im going to wire it parallel to my subs to lower it to 2 ohms.

how would i go about making it 14.4 V?

:) this is a whole new thing you are getting into here
i don't think you can quite reach 14.4V even with the engine running
more like 13.8V

keeping a constant voltage supply is a very hard thing to do especially when you are running high power amps.
first of all, you will need a good battery. Then you will need to run some thick as cable to your amp....4 guage cable is a must in most application. this will prevent the voltage drop through the power cable.
then if your battery is located quite far away from your amps, then it pays to put some capacitors in the system. At least 1 Farad per 1000rms of output power you have.

having a good electrical system will help your audio gears perform heaps better.

hmm, most capacitators hold 1 farad right? 1 farad = 1000 W of capacity?

hmm, most capacitators hold 1 farad right? 1 farad = 1000 W of capacity?

yea most car audio capacitors are 1 farad.
and 1 farad is good for 1000w

so if you are running 4 500rms subs off 1 2000rms amp or 2 1000rms amps
then you will need a good 2 farad of capacitors

To run a true 14.5 volts you would need a new alternator. Otherwise you would be running anywhere from 13.5 to 14 volts. But don't worry about that. Music playes at different impedences. So your amp would only pull what it needed to make the proper amount of power. Usually the lower the impedence the easier it is to make power. Also it usually helps to see if you can find an amplifiers Reative RMS rating. I have 2 MTX RFL's and 2 PH-D2's sitting in my room waiting to be installed in a colt. The Reative RMS rating for that amp is 2K watts, but the resistive rating is much lower. Usually amp companies will give you the resistive reading and not the reactive one, even though speakers are reactive loads not resistive.

i just want to clarify something. the RMS wattage is taken AFTER the efficiency business.

if your amp has an efficiency of 50%, and is 500 watts RMS, then you get 500 RMS going to the speakers... that would mean that 1000 watts must go in the amp.

and there really is no "equation" to calulate RMS. they just measure the output of the amp at full power... the lowest number they get is RMS, the highest they get is peak.

the thing about watts... dont be fooled... just because it can pump out that much power, doesnt mean it is actual music. above 1% THD (total harmonic distortion), distortion becomes audible. a QUALITY amp will express Peak/RMS at 1% THD... but the cheaper amps are expressed by allowing sometimes as much as 10% THD... thats not music. be careful to note the THD at the claimed wattages.

if you want a true sub, check this guy out.

www.hsuresearch.com

they make home theather subs, but manufacture a sub for automotive sub as well. Talk about response 16 - 100 hz is super low, my Klipsch 200W home theater sub doesnt even go this low! Read their reviews and about the man Dr. Hsu and youll see why these are so bad ass. Plus their reasonable ($109 @ + shipping) and gives you Amp Wattage recomendations there as well.

Pat

just because a speaker's response is low doesn't mean it'll play that low. usually that is a function of the box and it's tuning frequency. cip the Infinity KAppa Perfect 12.1 freq res is from 18-200 hz, but when put in the right box the freq of loudest output (something like 118 db) is 12 hz! add vehicle response and it puts out in the high 120's....