amplifier and subwoofer confusion

[[email protected]]

I am still new to the car audio area, and I have a few problems
deciding what to buy for a car.

Im looking arround crutchfield.com and other websites at different
subwoofers and amplifiers; and I really dont know what to buy.
I look at all the figures and numbers and with all the FAQ'S and other
guides it still doesnt help me unsterstand what I need to look for.
When im looking for subwoofers, I was told to get a higher RMS rating,
and dual or quad voice coils if possible. Then they told me I needed to
get subwoofers that I can bridge or link together to try and get 2 or 4
ohms. But as I read all this stuff I really get confused because im not
really sure what does what. Then I look for an amp and I see 100w x2 at
4 or 50w x4 at 4 and I dont understand what i should be looking for
and how to match what I want.

I want some subwoofers (doesnt matter what kind or size) that can
really thump hard and give good deep bass; and im also looking for an
amp to use for it. I would like someone to explain to me how to find
the subs I want and the amp to use to power the subs; and explain to me
the differences in the power rating, ohms, bridgeing, subs with dual
voice coils, and what the RMS rateing has to do with the subs and if
the RMS has anything to do with the quality of the subs.

[D.Kreft]

On Jan 15, 1:48 pm, " > wrote:

> When im looking for subwoofers, I was told to get a higher RMS rating,
> and dual or quad voice coils if possible.

Multi-VC drivers do nothing more than give you more options for wiring.
There is nothing inherently special about them other than that. Don't
let that concern you.

> Then they told me I needed to
> get subwoofers that I can bridge or link together to try and get 2 or 4
> ohms.

This depends upon the amp you choose.

> But as I read all this stuff I really get confused because im not
> really sure what does what. Then I look for an amp and I see 100w x2 at
> 4 or 50w x4 at 4 and I dont understand what i should be looking for
> and how to match what I want.

What else is in your car? Are you starting from scratch? If you're
starting from ground zero, a single four-channel amplifier (say 50W x 4
@ 4 Ohms) would be a really good start. Such a setup would give you a
really good amount of power and having it under one heatsink makes for
a cheaper and simplier installation. With such an amp, you can wire-up
your front and rear speakers to one pair of channels on your amp, and
then wire-up your sub(s) to the back two channels.

But all this is really hand-wavy without being given some idea of what
your budgetary constraints are, what kind of car this is, and how much
space you're willing to give up for a subwoofer enclosure.

> I want some subwoofers (doesnt matter what kind or size) that can
> really thump hard and give good deep bass; and im also looking for an
> amp to use for it.

What does "thump hard" and "good, deep bass" mean? Listing some of your
favorite CDs would be helpful.

> I would like someone to explain to me how to find
> the subs I want and the amp to use to power the subs; and explain to me
> the differences in the power rating, ohms, bridgeing, subs with dual
> voice coils, and what the RMS rateing has to do with the subs and if
> the RMS has anything to do with the quality of the subs.

You usually start with money...we can make all sorts of recommendations
about what to buy for $10,000, but if you have a budget of $500, it's
going to be a waste of time to go through the effort, ya know?

Some of your questions can be directly or indirectly answered by
various FAQs and tutorials online.
I highly recommend the JL Audio tutorials, found at
http://mobile.jlaudio.com/support_pages.php?page_id=127 .

It also sounds like you need to find a decent install shop in your neck
of the woods and pick someone's brain there. Educating yourself about
car audio soley through USENET posts is a very inefficient way to go
about it.

-dan

[[email protected]]

That website helped me understand the wireing for DVC subs and how to
wire them to get 2 and 1 ohm loads, but im still not getting the
information i want.

Im not buying anything yet, and im not worried about price, but i want
to know how to select the right sub-amp combination.

I listen to a lot of trance/techno/electronic and also rap and rock. I
already know which speakers im going to buy. but im not worried about
speakers right now, im just trying to find out which amp to get for
which subs, but i dont know wich subs to buy.

What i need to find out is what the RMS ratting means and how im
suppose to get the combination for sub and amp combination. So if you
could give me a explaination or a website i can go to it would be
great.

Ive looked for the information through google and have not found
anthing that can help me.

[[email protected]]

RMS power is the true powerhandling or output of a subwoofer/amplifier.
You want to match up the subwoofer's RMS to the amplifier's RMS (for
example, a 300 watt RMS @ 4 ohms amplifier for a 300w RMS single 4-ohm
subwoofer is the proper match up). You can go over this power handling
if you know how to set amplifiers properly so they don't put out their
maximum power ( e.g. 400w RMS amp on a 300w RMS sub) but it's not
reccomended unless you really know what you're doing. Otherwise, stick
with matching them up as closely as possible, and make sure you match
the ohms up right, and you're pretty much set.

check these sites:
<a href="http://www.woofersetc.com">www.woofersetc.com</a> <br>
<a href="http://www.crutchfield.com">www.crutchfield.com<br>
www.circuitcity.com</a><br>
<a
href="http://www.imagedynamicsstore.com">www.imagedynamicsstore.com</a>







On Jan 15, 1:48 pm, " > wrote:
> I am still new to the car audio area, and I have a few problems
> deciding what to buy for a car.
>
> Im looking arround crutchfield.com and other websites at different
> subwoofers and amplifiers; and I really dont know what to buy.
> I look at all the figures and numbers and with all the FAQ'S and other
> guides it still doesnt help me unsterstand what I need to look for.
> When im looking for subwoofers, I was told to get a higher RMS rating,
> and dual or quad voice coils if possible. Then they told me I needed to
> get subwoofers that I can bridge or link together to try and get 2 or 4
> ohms. But as I read all this stuff I really get confused because im not
> really sure what does what. Then I look for an amp and I see 100w x2 at
> 4 or 50w x4 at 4 and I dont understand what i should be looking for
> and how to match what I want.
>
> I want some subwoofers (doesnt matter what kind or size) that can
> really thump hard and give good deep bass; and im also looking for an
> amp to use for it. I would like someone to explain to me how to find
> the subs I want and the amp to use to power the subs; and explain to me
> the differences in the power rating, ohms, bridgeing, subs with dual
> voice coils, and what the RMS rateing has to do with the subs and if
> the RMS has anything to do with the quality of the subs.

[[email protected]]

RMS power is the true powerhandling or output of a subwoofer/amplifier.
You want to match up the subwoofer's RMS to the amplifier's RMS (for
example, a 300 watt RMS @ 4 ohms amplifier for a 300w RMS single 4-ohm
subwoofer is the proper match up). You can go over this power handling
if you know how to set amplifiers properly so they don't put out their
maximum power ( e.g. 400w RMS amp on a 300w RMS sub) but it's not
reccomended unless you really know what you're doing. Otherwise, stick
with matching them up as closely as possible, and make sure you match
the ohms up right, and you're pretty much set. Are you looking for some
brand reccomendations?

www.crutchfield.com
www.woofersetc.com
www.circuitcity.com
www.imagedynamicsstore.com --- for a good list of subwoofer boxes and
genuine ID subs





On Jan 15, 1:48 pm, " > wrote:
> I am still new to the car audio area, and I have a few problems
> deciding what to buy for a car.
>
> Im looking arround crutchfield.com and other websites at different
> subwoofers and amplifiers; and I really dont know what to buy.
> I look at all the figures and numbers and with all the FAQ'S and other
> guides it still doesnt help me unsterstand what I need to look for.
> When im looking for subwoofers, I was told to get a higher RMS rating,
> and dual or quad voice coils if possible. Then they told me I needed to
> get subwoofers that I can bridge or link together to try and get 2 or 4
> ohms. But as I read all this stuff I really get confused because im not
> really sure what does what. Then I look for an amp and I see 100w x2 at
> 4 or 50w x4 at 4 and I dont understand what i should be looking for
> and how to match what I want.
>
> I want some subwoofers (doesnt matter what kind or size) that can
> really thump hard and give good deep bass; and im also looking for an
> amp to use for it. I would like someone to explain to me how to find
> the subs I want and the amp to use to power the subs; and explain to me
> the differences in the power rating, ohms, bridgeing, subs with dual
> voice coils, and what the RMS rateing has to do with the subs and if
> the RMS has anything to do with the quality of the subs.

[[email protected]]

Thanks, that answers more of my questions. Its hard to describe what I
am really looking for in a system. I want loud and audible bass and i
know thats tough to find and it takes some money to get that, but
ultimately thats what I want to get for a car. I already know I will be
getting Infinity speakers (Kapa's) cuz I installed some into my friends
car and they sound like a dream; but for the sub and amp im not sure
what to get.

My newest question is about impedance:
Does the lower impedance give better sound quality and/or power
changes?





I keep reading though RAC but i cant find the answers to any of my
questions.

[D.Kreft]

On Jan 15, 7:50 pm, " > wrote:

> My newest question is about impedance:
> Does the lower impedance give better sound quality and/or power
> changes?

Impedance, measured in Ohms, is nothing more than the resistance to
alternating current. It has absolutely nothing to do with sound
quality.

However, the equation for determining power is P = V^2/R, so for any
given voltage V, the lower the resistance R, the more power you will
dissipate (which also means you'll be drawing more current). As
resistance goes down, power output of amplifiers typically goes up (to
a point). This is why you typically see specs like "50W x 2 @ 4 Ohms,
100W x 2 @ 2 Ohms", which is to say, in English, that "this amp will
produce 50 Watts in each of two channels if you put a 4 Ohm load on
each channel; or 100 Watts in each of two channels if you put a 2 Ohm
load on each channel."

You can always put a higher load on an amp without fear of damaging
it--the amp will simply not push as much current through it, and thus
the amp will run cooler and the system will be quieter. However, you
have to be careful about using a lower impedance...if your load is too
small, your amp will spit out more current than its output transistors
can handle and it'll likely let the "magic smoke" out of various
components inside the amp. If you have a hard time remembering this,
just think of which is bad:

1) touching your speaker wires together at full volume (dead
short), or

2) having nothing hooked-up to your speaker wires at full volume
(infinite load, or "open circuit")

Assuming a transistor-based amp, #1 is really bad (unless the amp has
the short-circuit protection) and #2 is perfectly fine.

For more on impedance, resistance and power, see the Wikipedia entry on
Ohm's law:

http://en.wikipedia.org/wiki/Ohm%27s_law

-dan
>
> I keep reading though RAC but i cant find the answers to any of my
> questions.

[[email protected]]

what i ment was does haveing lower impedance to the speaker ie giving
more power make the speaker preform better then haveing higher
impedance.

[D.Kreft]

On Jan 16, 3:55 pm, " > wrote:

> what i ment was does haveing lower impedance to the speaker ie giving
> more power make the speaker preform better then haveing higher
> impedance.

At the risk of sounding a bit pedantic, I want to clarify something
here...

A speaker *has* an impedance--it is a characteristic of the speaker--it
is not something sent *to* the speaker. Current is sent to a speaker.

With that out of the way, the direct answer to your question is
"yes...sorta."

As a simple matter of Ohms law, power is calculated as the square of
the voltage applied to the load divided by the resistance of the load:

P = V^2 / R

So, if the voltage (V) you apply to a load with resistance R is kept
constant, then it follows that the smaller R gets, the bigger P gets.
Conversely, if you increase R, P will get smaller. Take a concrete
example:

Let V = 10 Volts
Let R1 = 4 Ohms
Let R2 = 2 Ohms

For R1:

P = 100 / 4 = 25 Watts

For R2:

P = 100 / 2 = 50 Watts

Now, the reason I say "sorta" is because you have combined objective
terms like "power" and "resistance" with objective terms like "perform
better". Whether 50 Watts applied to any given speaker will perform
"better" than 25 Watts applied to the same speaker is dependent upon
too many variables such as the rated power handling of the speaker, how
much distortion is created by the amplifier's circuitry at each power
level, personal preference, etc., etc., etc.

NOW, with some qualifications, I can answer this more definitively:

ASSUMING the same total harmonic distortion between the two
applied powers, and
ASSUMING that both power levels do not exceed the manufacturer's
recommended power ratings for
the speaker, and
ASSUMING that all else is equal between the two applied powers
(bandwidth, etc.)

THEN.... yes, 50 Watts will perform "better" than 25 Watts.

But you're also discounting what makes the amplifier happy. A
low-impedance load will almost certainly make your amplifier run hotter
and with greater amounts of harmonic distortion as well as shorten the
life expectancy of your amplifier. So in that regard, I would say that
as a whole, an amp-speaker system will perform "better" with a higher
impedance load.

I'm sure that's more information than you were looking for, but this is
stuff you need to know so you don't get suckered by people throwing
half-truths or bald-faced lies your way.

-dan

[[email protected]]

Ok, new question.

When choosing a sub, does it matter if I choose a sub with 50-200 RMS
or 300 RMS if the rest of the subs specs are roughly the same?

[D.Kreft]

On Jan 17, 1:00 pm, " > wrote:

> When choosing a sub, does it matter if I choose a sub with 50-200 RMS
> or 300 RMS if the rest of the subs specs are roughly the same?

Define "roughly the same".

Thiele/Small specs do not a subwoofer make--they will not tell you how
well a subwoofer sounds; they tell you only how the loudspeaker will
behave (from an electrical and mechanical point of view). It's quite
possible to have two different speakers with identical specs that don't
sound anything alike. It's also quite possible to have two equally
well-made subs with *apparently* similar specs sound very different as
well.

As a newbie, you can pretty much throw the specs out the window. The
only real driver spec you need to concern yourself with is the the
driver's conservatively-rated power handling. My recommendation to you
would be to listen to as many subs from as many different manufacturers
in similar situations (power, enclosure size, enclosure type, etc.) and
pick the one that fits your ears and your budget the best. Unless you
really know what you're doing, then putting too much emphasis on specs
is likely going to leave you with lots of numbers to brag about, but a
system that is less than fun to listen to.

-dan

[[email protected]]

Alright, thanks for the help guys. I will post later if i need any
help.

-newbie out

[[email protected]]

Ok, 1 new questions:

If i am going to get 2x 10" subwoofers 50-400 RMS do I need to get a
amp that is 400x1@2ohms, 800 RMSx1@2ohms, or 400x2@2ohms?

[[email protected]]

taking into count the 70% those are the max numbers for the amp i can
get.

[mfreak]

wrote:
> Ok, 1 new questions:
>
> If i am going to get 2x 10" subwoofers 50-400 RMS do I need to get a
> amp that is 400x1@2ohms, 800 RMSx1@2ohms, or 400x2@2ohms?

You still need to know the impedance of the subs.

The likeliest scenario: Is each 10" sub 400 RMS at 4 ohms? Then you
can wire them in parallel, and you get a single 2 ohm load, and you
need 800 RMS, so the answer is 800 RMSx1@2ohms. Or you can run each
sub off it's own channel with an amp that does 400RMSx2@4ohms. This
would probably be a much more expensive amp, since it needs to be
stronger to push the same power through double the impedance..

Is each 10" sub 8 ohms? Then wire em in parallel for a single 4 ohm
load, then get an amp that does 800RMSx1@4ohms. They don't make amps
that push 2 channels at 8 ohms, so a 2-channel amp isn't a good option
for you there, your subs will get a LOT less power than the amp is
rated for. You'd be wasting a lot of the amp's capacity

Is each 10" sub 400 RMS at 2 ohms? Then you need 400 RMSx2@2ohms, or
if you can find a 1ohm stable amp, you could wire the subs in parallel,
creating a single 1 ohm load, and run 800RMSx1@1ohm.

[[email protected]]

Well, its 50-400 RMS 4OHM DVC so i can wire the dvc's in seriese and
the subs in parallel to get a 4OHM impedance. But what i was asking was
if i needed to get a 400 or 800 RMS amp; and you answered yes.

Thanks for the help.

[mfreak]

wrote:
> Well, its 50-400 RMS 4OHM DVC so i can wire the dvc's in seriese and
> the subs in parallel to get a 4OHM impedance. But what i was asking was
> if i needed to get a 400 or 800 RMS amp; and you answered yes.
>
> Thanks for the help.

Sorry, I missed the part where you said they were 4ohm DVC.. So you
can make 1 4ohm load or 2 2ohm loads. The subs need 400rms each
regardless. So you need an amp that does 800x1@4 or 400x2@2.

[KU40]

or 800 @ 1 ohm. which may be cheaper and easier to find.


--
KU40