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Amp & Subwoofer Questions...

C

chiwawa626

Lifer
Can someone explain how to choose an amp and what things mean? The two subs im getting are Infinity Kappa Perfect 10.1 Subs, 350watts RMS, and 1400 Peak, and they run at 4ohms. Now to choose a correct sub what the heck do i do? Im guessing i get a sub that runss 700watts rms (350+350) @ 4ohms? Whats this stuff when i look at an amp and it says 300w x 2 or 300 x 1...what does all that mean? And whats it mean to bridge an amp?
 
300x2 = How many watts, how many channels. ie...300 watts per channel. 300x1 = 300 watts, 1 channel. Generally, with anything but subs you use 1 channel per speaker or component set. With subs, that all goes out and you usually use 1 channel for all subs (It depends though)
Bridging is essentially combining the output of both channels...ie...Our 2 channel amp becomes a 1 channel amp with more power.

So, for 2 subs you would want either a 2 channel amp, 1 channel for each sub, or a 2 channel amp that can be bridged into 1 channel, or a 1 channel amp. The easiest for wiring would be a mono / bridged configuration and parallel the voice coils. That would give you a 2 ohm load, I think every amp under the sun can run that.
 
Wait so if i wire 2 subs togahter that are 4 ohms, that turns into 2 ohms? huh

So if a sub is 300 x 2 i can bridge the channels and now its a 600 x 1 where i can hookup both subs togather and each one on there gets about 300?
 
Oh boy....
Ok, you have two wiring options. Series and Parallel. Series, add the resistance..ie...4+4 = 8 ohms. Parallel (For your applicaiton) halve it..4/2 = 2 ohms.

You can run an amp as you stated, but keep in mind, usually sub amps with a x1 rating are at 1 ohm. Not always, but alot of times thats the case. You'd be good with an amp that does around 600 watts at 2 ohms. Its no worse to underpower subs (ie..using an amp with less power then what the sub can handle) as it is to overpower them (Using an amp that puts out more power then rated). However! In your case, I would recommend using an amp with a touch too much power. Alot of times, people with amps that dont push their subs hard enough for them end up cranking gains and boosts way up and run the amp into clipping. Clipping is bad. Really bad. Think of it as head room, your subs will start complaining from too much power before you clip on an amp that can supply the power wihtout clipping.

SQ is sound quality..ie...to sound good. SPL is Sound Pressure Level....ie...One goal, to get as loud as you can and damn how it sounds.

Now, the pwoer ratings on subs are alwasy to be taken with a grain of salt. Install can really screw with sub power ratings. Sealed box, just give'm 350 and be happy. Ported gets a bit funky. Above tuning frequency, you can run around the rated power. At tuning frequency, you can give'm 2, 3 even 4 or more times the rated power for short periods of time without undue concern, provided you know when they've had enough. Below tuning frequency and power handling drops FAST because the sub unloads from the box...ie...2, 3 or even 4 times LESS then rated power could still be too much, depending how far below tuning you go.

Are you doing the install, or is a audio shop?
 
Originally posted by: chiwawa626
Wait so if i wire 2 subs togahter that are 4 ohms, that turns into 2 ohms? huh

So if a sub is 300 x 2 i can bridge the channels and now its a 600 x 1 where i can hookup both subs togather and each one on there gets about 300?
Click to expand...

if you wire speakers in parallel, then the resistance (ohms) is cut in half. that's why if you wire two 4 ohm speakers that way, the amp sees a 2 ohm load. if you were to wire them in series, the amp would see an 8 ohm load. for solid state amps (which includes all car audio amps), the amp will make double the power every time you halve the load. so if you see an amp that is advertised as 200 watts @ 4 ohms, it will make 400 watts @ 2 ohm, or 100 watts @ 8 ohm. So obviously, having a smaller load is better if you want to be loud. The problem is some amps are only "stable" down to a certain load before they start overheating and stuff. Almost all car audio amps can handle as few as 2 ohms these days, and a few can go all the way down to 1 ohm... In your case, if you wire the speakers in parallel (you should), you will be presenting a 2 ohm load to the amp, so for power ratings, compare what the amps make at 2 ohm.

as far as i know, you are correct in your assumption about bridging the amp. The amp would push 600 watts, and each speaker would have to deal with 300 watts of that. you should know that unless you really want to peel the paint off your car and have your ears bleed, you'll never need anywhere near that much power. if you're using a headunit to power the rest of the speakers, my opinion is that anything over 200 watts total is complete overkill if you want the system to sound balanced. otherwise you're wasting money on headroom you can't use. now, if you want to blast the whole neighborhood, by all means, get an amp that can push 350 watts to each speaker. it's all about personal taste.
 
Thanks for the help dude, that really cleared sum stuff up for me 🙂

Well im waiting on the subs to come in by mail, lookin around for an amp rite now and a box i guess. If possible I'd like to install myself since im a do-it-yourself kinda person (just need to spend some time reading up on this stuff).

Hmm another question Boxes, where should i buy one from, are all boxes created equaly?
 
I just finished installing my sub/amp combo today in fact. Do you think 1600 watts is too much?
Naaaw..... 😀

As an add-on, some (although far and few between) amps put out the same power no matter the resistance seen by the amp...JL Audio is one such beast that does this....
 
Yummy 🙂

One more question, can anyone reccomend me some good amps for decent prices? Im not to woried about brand names or what not, i just need reliablity and quality.
 
Originally posted by: chiwawa626
Thanks for the help dude, that really cleared sum stuff up for me 🙂

Well im waiting on the subs to come in by mail, lookin around for an amp rite now and a box i guess. If possible I'd like to install myself since im a do-it-yourself kinda person (just need to spend some time reading up on this stuff).

Hmm another question Boxes, where should i buy one from, are all boxes created equaly?
Click to expand...

Nope. Unfortunately, most pre fab boxes are pretty plain and IMO dont use thick enough wood. But then again, most pre fabs arent meant for 1600 watt monster subs, hence me building my own. Whatever you do, DONT GET A BANDPASS!! Prefab bandpasses arnt worth diddly. Bandpass boxes designed specifically for the particular sub in qeustion are alright though.
As for wheer to get them, i really dont know about that one. Installing is fairly easy, I assume you have a car? Pull up the carpet and if your lucky you'll have a capped drain plug on the floor. If you do, its simple as pie to run the wire. If not, no biggie, just drill a hole. My drain plug was on the floor, half way between the pedals and the front of the seat on the driver side. Popped out the rubber cap, cut a hole in the middle (It became my grommet) and ran the wire from the battery, down trhough the tire well, along the bottom, up through the hole and into the trunk. My backseat has 2 clips, one on either side. Push the bottom of the seat in kinda hard and it pops loose.
Check here for wire sizes and power handling

You could probably get by with 8, but 4 is ideal. Dont use Monster Cable!! Its insanely overpriced. Dont use Dynamat!! It too is insanely overpriced. And ALWAYS ALWAYS fuse the power wire!!


EDIT...
To make it simple, one of the best bang for the buck amps you can buy is a JBL. You simply wont go wrong with them. Sure, theres amps with better options, and amps slightly cheaper that are as good, but on the whole JBL is the amp to buy if your on a budget.
 
Hmm so its just as bad to over power then to under power, so should i be looking for a 700-800 watt amp for 2 350watt subs? I was lookin at the jbl bp600.1, but anyone have any other suggestions? How are alpine amps they seem to be decently priced on ebay...also should i stay away from ebay and just buy from an authorized retailer?
 
Under power is good
over power blows them
under powering blowing them is a myth, try to blow you subs with a walkman

none of it really matters
You really can't tell the difference between 3 watts and 300 watts
 
Originally posted by: glen
Under power is good
over power blows them
under powering blowing them is a myth, try to blow you subs with a walkman

none of it really matters
You really can't tell the difference between 3 watts and 300 watts
Click to expand...

I read underpowering still hurts them through distortion or clipping or something and heat....is that true atleast?
 
You don't have to have an amp that makes what the subs can handle at the max, but it's good to havea little overhead. BTW, amps don't put out their full power until volume control is highest (and sometimes not then).
 
Originally posted by: chiwawa626
Originally posted by: glen
Under power is good
over power blows them
under powering blowing them is a myth, try to blow you subs with a walkman

none of it really matters
You really can't tell the difference between 3 watts and 300 watts
Click to expand...

I read underpowering still hurts them through distortion or clipping or something and heat....is that true atleast?
Click to expand...
Completely untrue, but a commonly believed "Urban Ledgend."


 
its very true...you will do more damage underpowering subs...if the amp is too big you can always turn the gain down (please note gain IS NOT a volume knob)...so may I recomend a nice 2500 watt class d amp?
 
You can "underpower" or "overpower" them. Its not the size of the amp that hurts them, its how the amp is used. A underpowered amp in the hands of a normal listener is more dangerous due to the fact they may want to turn everything up. once the amp clips, then you have serious problems. On the other hand, an amp with more power then the subs can handle generally wont be pushed into clipping.
So, if your easy on the gains, either amp is fine. If your a basshead like me, a amp underrated for the subs will do more damage. A n amp is capable of producing up to twice its rated power if you clip it. Thus, our 300 watt sub with a 200 watt amp would suddenly get 400 watts of power if we clipped the amp (Worst case). Its not the clipped signal that hurts the sub. Only 2 things blow subs. Too much power and too much heat. But, the extra power from the clipped amp is what blows the speaker.
So, you can take a 200 watt amp, and create a extremely clipped signal using some program, and play it at normal listening just fine. our subs dont see a clipped signal per se, they simply see a audio signal and play it. But, if we create a clean sine and clip the amp, the sub still sees a simple audio signal, but the harmonics introduced from the clipping cause the sub to see more power then it can handle. Thus, to keep it simple, clipping blows subs. (Not by the harmonics, but by the extra power and heat generated)
 
I'm not technical enough to accurately describe it. i know HOW it works, I just cant EXPLAIN it well.
Go here
That is one of the best forums I have found for car audio. Alot of people who frequent them are VERY knowledgable, ranging from IASCA winners to EE's who design speakers. Granted, theres your run of the mill asshats, but on the whole its a really good forum. Check in RC Archives, RC on AUdio and General Audio. Do some searches on clipping (Try the archives for that) Or search for anything else you may be interested on. Browse around, its an excellent audio forum.
 
underpowered amps don't clip and magically get more powerful and blow speakers
it is a myth
lots of people believe it, but it is simply not true
 
Originally posted by: glen
underpowered amps don't clip and magically get more powerful and blow speakers
it is a myth
lots of people believe it, but it is simply not true
Click to expand...

Look into a Fourier Analysis then get back to me.
Amps DO clip, clipping DOES increase the power the speaker sees.

Ok, well, I guess I need clarification on your statement.

You say: "underpowered amps don't clip"

Is this assuming gains are set right? If yes, then your right, amps dont clip. The problem is using a smaller amp opens up the potential (moreso then an amp too big) for someone to crank the gains up beyond what they should be, thus clipping the amp.
 
myth
I have heard it from lots of so called "knowledgeble people" but it remains untrue
and trust me, I have heard all the so called explainations, most are comical
it is a myth that has been around for at least 25 years
it is simply not true
 
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