California Dreaming

I have a question about mounting the subwoofers with the magnet side showing. I thought that subwoofers needs a percise amount of volume in their enclosure to make the proper sound. And then there are subwoofers like audiobahn that have designs on the magnetic side for display. Would mounting the subwoofer with the magnetic side showing distort the sound? Or could it possibly vary depending on the brand? I attached a picture if anyone doesn't know what type of mounting I am describing. Thanks in advance for your help.

Phiber Optik

iTrader: (2)

depending on the woofer sometimes you can hear mechanical noise, but usually that's only if your very close.

California Dreaming

But if thats the issue, why do they tell you how much space to mount it in if it doesn't need to be mounted in a box?

David Beale

A speaker emits sound from both sides of the cone. If you allowed the two sides of sound to add together it would cancel (one side has rising pressure when the other side has falling pressure). So, the object of an "enclosure" is to do one of two things - it either absorbs one sides energy, allowing the other side to be heard (as in a sealed box), or it converts the sound from one side to the same phase as the other side (such as a "transmission line" enclosure). A sub-woofer in a car has to absorb the sound from one side as the car isn't big enough for a transmission line to phase shift it.

The only difference from one side to the other in a speaker would be the directionality pattern. This doesn't really matter in a sub-woofer, as the wavelengths are measured in 10s of feet, and the car is much smaller than that. If one side of a sub is emitting noise, that means there is something wrong with it.

So the answer to your question is, basically it doesn't matter which way it's mounted - subject to the manufacturers requirements. Some speakers may degrade in sunlight, for example.

California Dreaming

I also have a speaker question, would there be any problem with the sound if I fabricated a box that fits flush with the space behind the seats and mounted the speakers as well as the subwoofers there? I know the location of the subwoofer doesn't make too much of a difference but I do not know if the same goes for the speakers. The speakers I am looking at are too large for the origional space on the door panals and I have seen what I am considering doing done in other cars before but I don't know what the sound quality would be. I think it would be alright but maybe someone else would know better than I would. Just to make sure we're all on the same page this is the location I am referring to:



Also, once I change the sound system, what would you recommend I do with the spaces where the origional speakers were mounted? I was thinking I could have them covered with something such as a thick layer of fiberglass and re-upholster them. Any better ideas?

DamonB

David Beale covered it all but I'll just add that when speaking of enclosure volume for a given driver you're talking about the volume of air the enclosure holds. So actual enclosure volume would be the volume of air required + the volume of the motor and basket assembly on the driver. When you mount the driver with the basket inside the enclosure you need a larger enclosure since the magnet and cone assembly take up volume inside the enclosure. If you mount the driver with the basket externally you don't have to allow for this difference in volume but then you have this big basket sticking out.

I don't ever mount the driver externally unless I'm building isobaric enclosures, then it's really convenient.

David Beale

Having the speakers behind your head can be a problem. The brain perceives sound coming from behind differently than sound from the front. I think you should choose speakers that fit in the stock location - you have the largest box (compared to the Bose boxes I have), so you can get a fairly large speaker in it. The RX-7 is so small it doesn't take much of a speaker to "fill it up" with sound. The sub would be fine back there. I would leave the stock grills in place. It would probably look better that way unless they are badly scratched. You can buy new stock grills as well. I have seen several people, pros and amateurs, box off the hatch area and install the sub there. Some mount the sub(s) facing the rear glass, some mount them on the removeable panel (replaced with wood), facing the passengers.

Thanks, Damonb, but I didn't discuss "tuning" the enclosure, so I didn't cover it all. Tuning can get rather technical, so I'd rather not get into it. If you don't know how to do it, you can go two ways. Most people just build the enclosure and enjoy whatever they end up with. Some will tune the enclosure, or will hire someone who know how, to get the very best sound. I'm not sure there would be a very large difference between the two, in such a small space (interior of an RX-7).

California Dreaming

DamonB- Thanks for the information, for practicality I will most likely mount the subs with the basket on the inside so I can avoid running into any problems with the sound.

David- It isn't a big deal for me to find speakers of another size to accomidate the existing speaker mount location especially if it will benifit the sound. Now if the speakers are a bit too deep for the existing location will there be any space for me to expand the mount without running into the inner door mechanics?

David Beale

I'm not sure about the non-Bose box. I was able to extend the Bose box 1/2" as I recall, further into the door. Just pull off the door panel and have a look. You should roll the window all the way down before pulling the panel.

Another tip - try to reuse the "door connector" wires the current speaker uses. It's a bit "Mickey Mouse" having wires that don't go through the door connector.

Also, replace the plastic once you are done. I used 6 mil plastic - it's cheap insurance against water damage. Clean out the door drain holes as well when you're in there.

California Dreaming

Great, thanks alot.

potatochobit

iTrader: (1)

subwoofers are non directional

Venom2U

That depends on what frequency you are talking about. When you get up to 50-60hz or above then it is very directional.