Subwoofer question

[thz71]

Ok ive got a couple questions. First off i have a 4 channel amp that i just bought its 75 watts rms per channels 240 watts x2 bridged. So in theory i need 2 240 watt rms subs? I had one and hooked it up brigged and it blew the sub so ive been looking for 2 new ones what do you reccomend? Also the dual voice coil confuses me if it has 2 4 ohm voice coils does that mean i have to hook up both voice coils? Thanks in advance!!

 

[dave_erald]

Look up Crutchfield.com They have a tech portion designed to match subs with amps based on ratings, ohms, amps regardless of what manufacturer. I would look there first.

Sent from my HTC 8X using Tapatalk

 

[96Z71ECSB]

I take it your bridging a 4 channel amp to use as a two channel amp? Then you are amplifying one sub per channel?
Yes. You need a subs that can handle 240 watts rms or more.

Dual voice coil subs are exactly as you described. Each voice coil is usually 4 ohm but they do make some with 8 ohm voice coils.
The voice coils are usually wired in parallel (+ to+,- to -) which will create a 2 ohm load on your amp. Your amp must be able to handle the lower impedance (2 ohm) or it will fry in a hurry.
You can also power each voice coil independently.

As far as recommendations, I would stick with the more well known brands.
Look for one (or two) that can handle the power and still fit in your enclosure.

Good luck.

 

[thz71]

I take it your bridging a 4 channel amp to use as a two channel amp? Then you are amplifying one sub per channel?
Yes. You need a subs that can handle 240 watts rms or more.

Dual voice coil subs are exactly as you described. Each voice coil is usually 4 ohm but they do make some with 8 ohm voice coils.
The voice coils are usually wired in parallel (+ to+,- to -) which will create a 2 ohm load on your amp. Your amp must be able to handle the lower impedance (2 ohm) or it will fry in a hurry.
You can also power each voice coil independently.

As far as recommendations, I would stick with the more well known brands.
Look for one (or two) that can handle the power and still fit in your enclosure.

Good luck.

Thanks man thats a lot of help so if i got a sub with 4 ohm dvc id have to wire one bridged channel to one side and the other bridged channel to the other side of the sub?

 

[df2x4]

Thanks man thats a lot of help so if i got a sub with 4 ohm dvc id have to wire one bridged channel to one side and the other bridged channel to the other side of the sub?

Noooo don't do that unless you're running a mono signal to both sides of that amp from the head unit. Running left and right signals to the same sub on different voice coils will fry things pretty fast. If you run a single sub I'd really recommend something besides a 4 channel amp, I've never really seen that work out right. You can get by with a 2 channel bridged on a single sub. Rockford Fosgate's wiring diagrams are a decent tool for reference if you're not too familiar with impedance, etc.

http://www.rockfordfosgate.com/rftech/woofer_wizard.asp

Can you give us the make and model of your amp? Those power specs seem a little strange to me. Not sure how they went from 75x4 to 240x2 unless they rated those at different impedance.

EDIT - Also as far as the impedance ratings (Ohms) you should really pick what subs you need based on what output impedance your amp is capable of and how you're going to wire everything up. For instance, a single sub with two 2Ohm voice coils can be wired up to present a 2Ohm load or an 8Ohm load depending on how you hook everything up and what your amp is capable of. Dual 4Ohm coils have different possible combinations, and combining multiple woofers of the same type can give you even more options. Lower impedance generally means more power when the amp stays the same, but if you wire your subs up to present a 2Ohm load and your amp is only capable of a 4Ohm load, you're going to fry that amp.

Good luck! Designing the stereo in my reg. cab was one of the most fun projects I've ever done.

 

[df2x4]

Because I'm bored and find this stuff way too fascinating, here's an example of how much you can change your power output of your amp just by changing the impedance of your speakers. Most amps won't go down nearly this low without melting, this one was designed as a "cheater amp" for stereo competitions because it was rated at 25x2 at a 4 ohm load but would actually do down low enough to push around 800w. I have a couple of these specific ones, they're pretty wild.

http://www.youtube.com/watch?v=F70Q-lltORE

 

[thz71]

http://www.crutchfield.com/p_777M4075/Sound-Ordnance-M-4075.html?tp=115

Thanks for all the help guys heres the am i bought it to act as a 2 channel amp to use with 2 subs so im thinking 2 svc subs now

 

[df2x4]

Yeah that would probably be the easiest considering the amp. One thing to consider, if your head unit has the ability to combine the left and right sub outputs so that both RCAs carry the same mono signal, that would be best. You can run two subs like that in stereo but the slight differences between the left and right channels playing will cancel out some of your bass. Some 2 channel amps have a mono switch on the amp itself to accomplish this but I don't believe your 4 channel does. It might not be super noticeable but I definitely noticed an improvement going to a mono setup.

 

[thz71]

Thanks man i might just buy a different amp and use this one to run 4 6x9s or somthin lol

 

[df2x4]

No problem, honestly that's probably the best idea. I just looked at it again and it doesn't have a low pass filter for subs on one of the sets of channels so the only way you could use it effectively as you're wanting to would be to turn all the bass boost off and set both crossovers to full, and then tune frequencies accordingly through a nice head unit. You could make it work but it's probably more trouble than it's worth.