Subwoofer question

 

New member
Username: Alex_5

Post Number: 1
Registered: Jul-10
So i currently have two pair polk db6501 component system in my vw hooked up to an alpine mrp-f450 4 channel amp, each speaker hooked up to each channel. I am in the process of adding a subwoofer, preferably a shallow 10'' sub. So i talked to crutchfield and they recommed the an alpine 2ohm dual voice coil sub. My question is can i run the 4 speakers and the sub in this 4 channel amp or would i need to buy another amp?

Here are the specs for the polk db6501 component speakers:
Driver Complement
Mid/Woofer 1 - 6-1/2" Diameter (16.51cm)
Polymer/Mica Composite cone with rubber surround
Tweeter 1 - 1" Diameter (2.54cm)
Silk/Polymer Composite dome
Electrical
Overall Frequency Response 35Hz-23kHz
Nominal Impedance 4 ohms
Power Handling (continuous) 100 w
Power Handling (peak) 300 w
Efficiency 92 dB

Heres the specs for the alpine mrp-f450:

4-channel car amplifier
70 watts RMS x 4 at 4 ohms (100 watts RMS x 4 at 2 ohms)
200 watts RMS x 2 bridged output at 4 ohms (4-ohm stable in bridged mode)
2-, 3-, or 4-channel output
variable high-pass/low-pass filters (50-400 Hz, 12 dB/octave)
tuned Bass EQ (12 dB bass boost at 50 Hz for channels 3 & 4)
subsonic filter (15 Hz, 24 dB/octave for channels 3 & 4)
MOSFET power supply
CEA-2006 compliant
STAR Topology (minimizes internal noise and prevents ground interference)
speaker- and preamp-level inputs
preamp outputs
gold-plated screw terminals
fuse rating: 25A x 2
8-gauge power and ground leads recommended -- wiring and hardware not included with amplifier
13-1/4"W x 2-3/8"H x 9-9/16"D
 

Silver Member
Username: Quirky

San Antonio, Texas

Post Number: 449
Registered: Feb-07
You would most definitely need to buy another amp if you would like to run a sub.

What vehicle are you installing this into;is there a reason you are looking for 'shallow' subs? and what is your total budget?
 

New member
Username: Alex_5

Post Number: 2
Registered: Jul-10
i will be running this on a jetta 2003 and the reason for the shallow sub is becasue i will be making a custom stealth box.

Also the guys over at crutchfield told me that i could run the sub if i bridged the speakers, but since i am not a audio guy i don't understand much of how these works
 

Silver Member
Username: 420pimp2

Baltimore Atlantic Ci..., MD, NJ

Post Number: 972
Registered: Jan-06
Yo guy!You will need a mono amp for your sub. You can use the 4 way but in its pointless. Dont listen to those jackasses there. Ecoustics help this man. peace and bump__ line _______________

(:Yayo
 

Silver Member
Username: Quirky

San Antonio, Texas

Post Number: 451
Registered: Feb-07
There are many reasons why you do not want to do that. One reason- subs are made for the lower frequencies where as the other components (door speakers) are made for higher frequencies. If your running from one amp you would not be able to cater to both the lows and highs. This has to do with the built in cross over. You don't want your subs to sound like your highs do you? That also would mean you would have no control in tuning your amp for your sub.

You bough the amp for your components- use it for what it was meant for rather than trying to ghetto rig it. Your components are already going to be a slightly underpowered with that amp considering their recommended power is at 100wrms and your amp will give them 70wrms if those specs are correct.
 

Silver Member
Username: Gcs8

Atlanta, Ga

Post Number: 717
Registered: Sep-09
not quite ben, its a 2/3/4 channel amp witch means theres 2 sets of EQ's one for the front channel and one for the rear channel, witch also means they should have a high pass, low pass and full settings for each eq. now he could do what crutch field said but he would lose power to his back speakers (witch you don't really need any way.) but a real class D amp is going to be better all around then his 4 channel class A/B amp.

also you don't need to match power perfectly on door speakers, as when you turn the vol down the power to the speakers is less so full vol may be 70 watts from the amp and normal vol would be ~35 watts so as long as his speakers can keep up with his sub stage the power he has is fine.
 

New member
Username: Alex_5

Post Number: 3
Registered: Jul-10
ok so lets say i buy a class d amp, wouldn't that drain too much power and ultimately hurt my alternator?

what amp would be best with any of these shallow subwoofers:
alpine sws-1023d, alpine sws-1043d or the kenwood kfc-xw1000f.
 

Silver Member
Username: Gcs8

Atlanta, Ga

Post Number: 718
Registered: Sep-09
not sure who you are getting your info from but a class A/B amp pushing a sub is only 50% eff where as a class D amp is ~80% eff sooo, no sub amps draw more beacouse they are more power full but you would be surprised what you can do with 400-500 watts on a sub.
 

Silver Member
Username: Quirky

San Antonio, Texas

Post Number: 452
Registered: Feb-07
Good point deathoob. That definitely slipped my mind and thanks for correcting me. With a high pass low pass setting, crossover, and gain for both the rear and front channels as silly as it sounds its possible.

Regardless, you would still want to run a sub off another amp just so you can sufficiently power both the components and sub properly.

You will be fine putting another amp on your electrical system. Anything under ~1000wrms is not going to put damaging levels of strain on your alternator.

btw deathoob I don't understand what you mean by "no sub amps draw more because they are more power full". Efficiency is one thing, but one amp with the same efficiency as another may draw more power because it is made to produce more power for the sub.
 

Silver Member
Username: Gcs8

Atlanta, Ga

Post Number: 722
Registered: Sep-09
what i was trying to say is that the sub stage will mull more power when it is pushing the sub hard, glass wolf would explain this better i am having trouble putting this in to text.
 

Silver Member
Username: Cwruck

Post Number: 335
Registered: Feb-10
you could just be better off running your front 2 speakers off the alpine and bridging the last 2 channels to a sub. or if you decide to run all 4 speakers off that amp and get another amp for the sub you can do that, but that current 4 channel amp can draw quite a bit of current, and adding another amp can and will easily start to dim your headlights, meaning your alt is failing.
if you stay around 400-500 watts on a class d amp you will be fine, but if your trying to do like 800 its not going to work.
sub amps are much more efficient, and will draw far less current that an a/b amp.
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