LEFT and RIGHT subs ?

[Steve W]

I want to run 2 subs off of 1 amp.

The amp has the usual (for low-price ones, that is) left and right /
+ and - 'speaker outs'.

Can I run 1 sub as LEFT and 1 sub as RIGHT, or, should subs always be MONO/Bridged ?

(If so how/can I run 2 off the 1 sub ?)

Steve.

[Flavio]

Wire the subs in parallel (+ to + and - to -) or in series (+ to - and the remaining + and - to the amp) and then connect them to the amplifier. Depending on the impedance of the subwoofers and the stability of the amplifier you have to choose parallel or series.

Flavio

[Digsy]

Steve,

If I'm reading your post right you have two separate outputs (L and R) that you want to use to drive two subs?

I'm not audiophile, but I thikn bass is non-directional so you might argue that driving one sub off each channel whould make no difference (especially if you mount the subs close together).

If you want to bridge the output stages of the L and R channels together then you need Mr. Harwood!

I know that if you want to drive multiple speakers from one channel, the total impedance of the speakers must be the same (or very close to) that of the output stage, which is usually 4 ohms for ICE.

Rt = total impedance
R1 = impedance of speaker 1
R2 = impedance of speaker 2

For speakers in parallel, Rt = 1/ (1/R1 + 1/R2)
i.e. two 8 ohm speakers in parallel gives a total of 4 ohms.

For speakers in series, Rt = R1 + R2
i.e. two 2 ohm speakers in series gives 4 ohms.

[Steve W]

I'm gonna' make my own box and either put 1 x 12"/15" in which
case I'll just use the 'Bridged' terminals (as I had it in RS).:thumbs:

OR, I'll use a PAIR of 8"/10", THEN I'll need to drive 'em both with 1 amp (can't be arsed with another amp, more wires)

SO, just in case, I was gonna' wire 1 left / 1 right (if ohms suit ?)
[yeah, I know you only need Mono, but it was for 'ease' !)
OR, as I said, does it NEED to be bridged (for ohms) in which case,
is it/can I, parallel/series AND HOW THE HELL DO I WIRE 'EM UP
(amp-, 1-, 1+, 2-, 2+, amp+) ?
(all -ve together, all +ve together) ?
:stupid:

I did/passed Physics 'O'-level but electrical circuitry STILL left me
cold (brrrgghhhh!):(

Steve-the-wanna-be-nerd. :p

[Digsy]

Steve,

It'ld be easier if you could tell us what the impedance of the output stage of your amp is: Both the left and right channels, and the "bridged" terminals, if it has them. It must be in the blurb somewhere, or maybe even written on the amp itself.

If not, and you want to go for simplicity, I'd bet that its 4 ohms. The impedance of the speakers will be written on the back of the coil. If thats 4 ohms too, then just wire each sub to each channel like you might a normal speaker. If not then post all the values here and we can work out an arrangement that will give 4 ohms total.

Whether or not the left and right channels really need to be bridged to deliver the right power level into a single sub is another question. :cool:

[Steve W]

Sorry Darren.....told you I'm a doofas when it comes to this...

I KNOW WHAT I WANT, but, NOT HOW TO GET IT.

Leaflet in amp box says:

Stereo Mode : 2-4 Ohms
Bridged Mode : 4-8 Ohms

RMS @ 4 Ohms : 85 W x 2
RMS @ 2 Ohms : 125 W x 2

Max Power (sorry!) : 300 W x 2 (I know that bit's not wortha t**s)

WOS ALL DAT MEAN DEN ? ?

[Digsy]

This is as good an explanation as I can offer (where's Matt H when you need him most????)

Stereo Mode : 2-4 Ohms
Bridged Mode : 4-8 Ohms

This is telling you the impedance of the speaker (or speakers) that you should connect to ecah channel. When operating in stereo (L & R channels seperately) you can safely connect speakers with 2 to 4 ohms impedance. In bridged mode (single channel) this doubles to 4-8 ohms. I don't know why it doubles, but its the impedance you need to know.

RMS @ 4 Ohms : 85 W x 2
RMS @ 2 Ohms : 125 W x 2

The power ratings telll you how much ooomph goes into each speaker, depending on what impedance it is. Strange that it doesn't say what the power rating is in bridged mode. I suppose it might be 170W RMS into 4 ohms. Note that the higher the impedance the lower the power.

ANYWAY, you know the acceptable impedances for both 2 and 1 channel operation, so you can either run in two-channel mode with a 4 ohm speaker on each channel, or in bridged mode with either 2x 4 ohm speakers wired in SERIES to give a total of 8 ohms, or a single 4 ohm speaker (bridged mode can handle 4 to 8 ohms).

Another possibility would be to find two 8 ohm speakers and wire them in parallel to give a total impedance of 4 ohms, and use this in bridged mode. This might be the best option because your amp seems to deliver more power into a lower impedance, and you want to run 2 subs.

I have no idea how to wire the two channels together to bridge the amp, though.

[Steve W]

You really must have SAT and typed for ages there Darren...

Cheers Mate :thumbs:

Yes, that's getting a lot clearer now, as I said, HATE THE OHMS

BUSINESS ! but think I'm getting it (well...enough! :conf: )

Thanks, Steve.

[HedgehogSandwich adi]

Theres no reason why you cant wire them up as seperate channels, or wire them up as bridged set as Darren suggests. The only issue will be is the fact that you will be putting both channels into one enclosure.

You wont notice the followng in a car set up, but its worth bearing in mind.

99% of the time most low frequency signals are panned dead center, so you'll have no problem with both channels in one enclosure as the action of the drivers will be the same..

In some cases though (most noticeably with non-dance music, live jazz recordings, acoustic sessions etc) low frequencies are panned hard left or hard right, or somewhere inbetween (not necessarily what you'd call 'bass' frequencies, but anything up to 500 hz *will* be reproduced through your sub, despite what you think and *will* be present in the L and R channel at seperate times).

Obviously this is no good for 2 channels in one enclosure set up. It wont be noticeable though but its worth bearing in mind.

[Steve W]

SO,

IF I end up going the LEFT & RIGHT 'stereo' route it might
be best to divide the enclosure down the centre just in case
they 'interfere' with each other ? ?

--------------------------------------------

I may leave the amp I've got with the Box/Sub I've already got
and give that to my Dad/Sister (seems a shame to waste the box,
it's a perfectly matched set-up - well, in MY humble opinion).

AND, buy a nice new one with just a TIDGE more power and capable
of this '4,3,2' channel lark.....then I can mess about to my
hearts content ! ! (and even run MORE speakers off it - the boot
will be full ! !)

I'm getting into this 'SUB'-thing - I'll be blowing me back window
out in no time ! (?):(

[HedgehogSandwich adi]

Originally posted by Steve W
SO,

IF I end up going the LEFT & RIGHT 'stereo' route it might
be best to divide the enclosure down the centre just in case
they 'interfere' with each other ? ?



yes...although even with a divider they will still interfere with each other to a degree. Wood is one of the next best transmitters of sound after air, although mainly with the higher frequencies.

In a car setup though you wont notice, and i'm not sure what most car audiophiles would say..but from an acoustic point of view two channels in one enclosure is not a good combination.

[Steve W]

Cheers for the info Mr.Hog-Butty (friendly alteration !)

I'll let you know how it goes.......... OR DOESN'T ? ?


Steve-indecisive-W.