Subwoofer position: Facing Up or Back?
 

As I continue my resurrection of my FD, I am ready to start installing the new simple audio system. As part of that install, I am putting a single 8" sub in the hatch area of the car. This leads me to the following question: Does a sub in this car sound better facing up or facing back?

Here's some pics to help see what I mean.
Sub Facing Up
Sub Facing Back

Please note that the cover will be remodified to fit the installation and will have acoustically transparent covering above the subwoofer but the sub will not be visible from outside the car.

Thanks for your help!

Since lows are non-directional and Highs are, it's always best to aim a sub away from the listener. This way, the distorting highs that make through filters, will not affect the sound, since they cannot be heard if facing away. But the full sound of the non-directional lows, can be heard from any position. So the reason for aiming it away, has nothing to actually do with the actual sounds that you want from the sub, but more the sound you DON'T want from the sub.

Actually, lows ARE directional. Particularly in a car setting. The intensity of the sound wave at the listener will vary depending on the position of the speaker.

Having it face up will probably cause less standing waves, but back would probably create a bit more sound level. I'd just put the sub in a cheap box and try different positions before building your final box.

Blake

Thanks Str8Down.

The sub will get a low passed signal at 80Hz using a 24dB slope. I am hard pressed to note directionality of any sub 80Hz signals, but, as you mention, this is not a brick wall filter and some very low volume 100Hz notes might be heard?

My primary concern with the upward sub is one of vibrating the hatch glass and the resonances produced by that?

Blake,
I agree with regard to pressure waves produced by subs, but, since I am not looking for alot of thump, just flat, bottom fill down to say 35Hz, I am hoping that not much of a pressure wave will exist?

Since I really don't want the corner loaded type increases in SPL, sounds like upward might be best.

As for trying out different positions, that won't be possible since the install of the primary speakers and head unit is being done by a shop and the Sub/amp/fuse block needs to already be in place when I drop off the car.

Facing down.http://www.cardomain.com/memberpage/542356/2

You have common misconceptions regarding acoustics.

1. Very low frequencies ARE non-directional, ESPECIALLY in a car setting.

2. Standing waves do not occur in a vehicle, at least not in the lower frequencies where they would normally be a concern. In almost any car, and certainly in an RX-7, you are in a pressure zone below 100 Hz. That means that the entire air volume in the car changes pressure as a single unit. A standing wave cannot occur in this situation.

If low frequencies are non-directional, how come different positioning of subwoofers change the SPL in relation to a single point? To me that indicates directionality.

Blake

That has to do soley with reflection. By aiming it in different directions, you may get different reflection based on what the sound is bouncing off of. In the FD, I would be willing to bet anything, that reflection would make no difference in SPL. In a Lincoln Navigator, yes, FD, no.

SPL at what frequency? Having a sub point directly at you may result in higher SPL than having the sub point away from you solely due to the higher frequencies coming from the sub.

There are also many other factors, such as any barriers the soundwave has to travel through, etc. But I guarantee you that at very low frequencies, a typical sub is almost completely non-directional. Multiple subwoofers mounted closely together CAN produce a directional sound field, depending on many other factors.

I think they sound about the same but you can feel it more if you have then facing back I'd face them back personally.

According to Eddie Runner's sub position based mic'd recordings, he says the best SQ spot for any sub is facing backward, within 3 feet of the rear of the trunk or hatch.

I guess I'm gonna aim it backwards.....

My JL Audio 10" sub is on a 45 degree angle which ultimately parallels the rear hatch glass. The custom box utilizes the space underneath the rear strut bar and the woofer face extends out flush w/ the strut bar. Sounds great w/ no rattling. Powerd by a new punch 75 X 2 bridged mono.

My Basslink fires up. I never tried it the other way because it wouldn't fit that way. It sounds good the way it is.

http://www.alantripp.com/basslink.jpg

What is a basslink? Is it a sealed box sub?