# Reverse Driver?



## mgboy (Jan 17, 2007)

I've seen a couple subwoofer systems where the drivers were facing into the enclosure and wondered why. Wouldn't that not work as well? I think someone on here has a avatar with 4 woofers facing in and I just thought that was odd. Are there any dis/advantages? Does it sound the same? What about freq. response? I'm curious, and an amatuer.


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## Darren (Apr 20, 2006)

You are probably looking at an IB subwoofer, the attic is the box so the drivers are actually facing into the room down the throat of the manifold. I don't believe the performance would be different either way though on a box sub.


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## Rodny Alvarez (Apr 25, 2006)

We do the subs like that en car stereos and there is no difference in sound, a lot of subs look good from the back so is just for show, another thing is the some subs are real deep and some times you don't have the room for the magnet so inverting the sub you don't need but a few inches of depth, and don't forget the sub needs to be wire out of phase!!! :bigsmile:


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## mgboy (Jan 17, 2007)

Well, I was looking at your avatar Darren, but now that I've looked at what it actually is, I realise that is not what I was thinking of.

I think Rodny got it. I've seen it on some car setups, that's where I originally saw it, since then I've seen HT subs with the drivers facing in. So I guess space and aesthetics are the only reasons. I still can't see how that wouldn't affect the sound though.


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## Chrisbee (Apr 20, 2006)

mgboy said:


> I still can't see how that wouldn't affect the sound though.


With subwoofers only very low frequencies are involved. The driver is basically just pumping air in and out. 

At these very long wavelengths there are no reflection resonances within the basket. Particularly as most subs use an 80Hz crossover which blocks higher frequencies from being played by the large cone of the sub. 

Provided the basket isn't tightly closed (and none are) the air movement is unaffected by reversal of the driver in a sub.

With midrange units and cone tweeters the cone faces the listener to avoid odd responses from reflections within the basket. 

The upper frequencies narrow the active cone area with rising frequency by utilising localised cone break-up centred more and more on the dust cap. 

If the magnet faced the listener then these higher frequencies would be blocked.

The cone cannot possibly vibrate as a whole at frequencies beyond a certain range no matter how stiff you make it. Which is why dome tweeters have largely taken over from the earlier cones. It was realised that only the dust cap operated at very high frequencies.


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## Guest (Jan 31, 2007)

for car audio i have been taught there is a db of loss so to speak b/c the interferance of the sound wave being chopped up, but nothing really noticable. in my theatre system i have two shivas reversed for that tiny bit of air space. the problems i have are vent pole noises and some tinsel clap noise which i dont belive i would hear from the front. the other this i might mention is when u have 4 subs in a car b/c u can hear everything so loud and close it is better to wire two in and two magnet out to have the mechanicle noise out of phase from eachother. personaly i perfer cone out with my sealed box b/c how smooth it sound.


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## Peter De Smidt (Dec 22, 2006)

Supposedly, if you have two drivers mounted close enough together, one mounted "in" and one "out, and they're wired out of phase, then distortion will be lower. Since drivers aren't symmetrical, movement one way will not be exactly the same as movement the other way. The idea is that since one driver is moving towards the magnet while the other one is moving away, that those parts of the signal that are not the same in both woofers will be attenuated, although I'm not sure why. It'd be interesting to see actual distortion numbers of both setups with the same drivers.


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