Speaker radiating

Jonhny · 18th July 2008, 06:23 PM

I have been looking through the forum trying to find info regarding speakers radiating into a car. I am trying to figure out if a woofer radiating freely mounted in a wall (box behind wall - hole in the wall) ,in this case the wall between passenger and luggage compartment, would sound better and be louder than focusing the woofers and port through a 20x30cm hole in the wall (mount woofer in luggage compartment). The reason for not just trying is that cutting a couple of 10" holes in the wall of the car isnt my first choice, especially if it doesnt work well. So, I am trying to get an idea of what the difference between the two methods would be. However I feel like a blind man in a laser-show right now.
2x10" woofers in a ported enclosure. Right now the enclosure is sitting in the trunk sounding so so. Any thoughts?

jol50 · 18th July 2008, 08:27 PM

Some cars have lots of insulation for noise from trunk, and can cut your bass a lot. You can remove some, or if you have stock speaker locations just open them up and put a grill on them. I would think you will get maximum output with the drivers visible/mounted in the passenger area though. Sometimes in the trunk it can mute the subs a little and they sound better at cost of output. For example you don't hear any cone noise or vibration, it essentially cuts the LP down a little more. Also try moving the box in trunk, I tend to like box facing back at rear of trunk...luggage area? We say trunk here, if that is what you mean.

Jonhny · 18th July 2008, 08:43 PM

Quote:

Originally posted by jol50
I would think you will get maximum output with the drivers visible/mounted in the passenger area though.

Does anyone have an explanation to why this would be? I get the feeling that you are right, but would like to know how it works.

Anyone knowledgable in physics?

Clipped · 19th July 2008, 03:36 AM

the sub wont have to penetrate the wall, and lose output in the process.

i had a bmw e30 with a metal wall between the backseat and trunk.

the best arrangement for these kinds of obstructions are to mount the subs in the rear deck from under, sealing it off very well, and raising the crossover point a bit...

or use a bandpass box and simply port through the existing rear speaker holes.

jol50 · 19th July 2008, 04:03 AM

I have run a pile of IB systems....no box. You certainly get more when the sub is visible in passenger area. I had one car with two 10" in rear deck and two more into seatback. I took foam out for those, most of it. I could hook one or other set up to see what it did and indeed the seat set put out a little less, were muffled, but that was good thing for them IMO since they were rolling off anyway. With both sets on it was great. I have four 12s into my seat now just to make sure, but found it is overkill for what I need.

There is one aspect of sound/radio waves/light that people often do not realize. If you take an emitter of one of them and think of it as a pie (or maybe pizza) how close do you have to be to take up 25% slice of it? Very close. If you move back not that far note how you are now maybe 2% of the circle? You lose a lot right close to it because it is radiating in many directions, so just being close to it lets you absorb much more energy. Now figure your trunk is going to absorb all kinds of energy because the panel the sound has to go through to get to you is only getting part of the total output of the sub. The only thing that helps is that sub frequency has a much easier time traveling through and around things than say light does. If you take a tweeter for example, it plays to you nearly via line of sight and reflection and much lower output otherwise...because high frequency is much more directional. So you can get away with it using a low frequency, but you still lose some.

Jonhny · 19th July 2008, 07:00 AM

Thanks guys, loved the pie analogy

I will try to put a box in the backseat and measure/listen.

If it works I will consider making holes for the woofers through the wall. Then I would also have to convert the rear seat to a folding one. Otherwise it muffles all high frequencies (60-100).

I cant put woofers firing up the rear deck, anything visible will get the car stolen.

jol50 · 19th July 2008, 03:31 PM

My four 12s play through the seat, the foam cushion, and they work fine. I can hardly hear any difference with seat out. I removed the trunk panel they had in there and made a baffle of 3/4 braced ply. Also adjusted the seat so there is a little gap at top of less than inch, if someone sits there it flexes back otherwise there is a little opening. I guess it depends on how the seat is made.

Sub frequencies can go around corners, but at least you get the idea of how loss happens.

18th July 2008, 06:23 PM	#1
Jonhny diyAudio Member Join Date: Mar 2005 Location: Sweden	Speaker radiating I have been looking through the forum trying to find info regarding speakers radiating into a car. I am trying to figure out if a woofer radiating freely mounted in a wall (box behind wall - hole in the wall) ,in this case the wall between passenger and luggage compartment, would sound better and be louder than focusing the woofers and port through a 20x30cm hole in the wall (mount woofer in luggage compartment). The reason for not just trying is that cutting a couple of 10" holes in the wall of the car isnt my first choice, especially if it doesnt work well. So, I am trying to get an idea of what the difference between the two methods would be. However I feel like a blind man in a laser-show right now. 2x10" woofers in a ported enclosure. Right now the enclosure is sitting in the trunk sounding so so. Any thoughts?

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18th July 2008, 08:27 PM	#2
jol50 diyAudio Member Join Date: Nov 2007	Some cars have lots of insulation for noise from trunk, and can cut your bass a lot. You can remove some, or if you have stock speaker locations just open them up and put a grill on them. I would think you will get maximum output with the drivers visible/mounted in the passenger area though. Sometimes in the trunk it can mute the subs a little and they sound better at cost of output. For example you don't hear any cone noise or vibration, it essentially cuts the LP down a little more. Also try moving the box in trunk, I tend to like box facing back at rear of trunk...luggage area? We say trunk here, if that is what you mean.

19th July 2008, 03:36 AM	#4
Clipped diyAudio Member Join Date: Mar 2005 Location: home	the sub wont have to penetrate the wall, and lose output in the process. i had a bmw e30 with a metal wall between the backseat and trunk. the best arrangement for these kinds of obstructions are to mount the subs in the rear deck from under, sealing it off very well, and raising the crossover point a bit... or use a bandpass box and simply port through the existing rear speaker holes.

19th July 2008, 04:03 AM	#5
jol50 diyAudio Member Join Date: Nov 2007	I have run a pile of IB systems....no box. You certainly get more when the sub is visible in passenger area. I had one car with two 10" in rear deck and two more into seatback. I took foam out for those, most of it. I could hook one or other set up to see what it did and indeed the seat set put out a little less, were muffled, but that was good thing for them IMO since they were rolling off anyway. With both sets on it was great. I have four 12s into my seat now just to make sure, but found it is overkill for what I need. There is one aspect of sound/radio waves/light that people often do not realize. If you take an emitter of one of them and think of it as a pie (or maybe pizza) how close do you have to be to take up 25% slice of it? Very close. If you move back not that far note how you are now maybe 2% of the circle? You lose a lot right close to it because it is radiating in many directions, so just being close to it lets you absorb much more energy. Now figure your trunk is going to absorb all kinds of energy because the panel the sound has to go through to get to you is only getting part of the total output of the sub. The only thing that helps is that sub frequency has a much easier time traveling through and around things than say light does. If you take a tweeter for example, it plays to you nearly via line of sight and reflection and much lower output otherwise...because high frequency is much more directional. So you can get away with it using a low frequency, but you still lose some.

19th July 2008, 07:00 AM	#6
Jonhny diyAudio Member Join Date: Mar 2005 Location: Sweden	Thanks guys, loved the pie analogy I will try to put a box in the backseat and measure/listen. If it works I will consider making holes for the woofers through the wall. Then I would also have to convert the rear seat to a folding one. Otherwise it muffles all high frequencies (60-100). I cant put woofers firing up the rear deck, anything visible will get the car stolen.

19th July 2008, 03:31 PM	#7
jol50 diyAudio Member Join Date: Nov 2007	My four 12s play through the seat, the foam cushion, and they work fine. I can hardly hear any difference with seat out. I removed the trunk panel they had in there and made a baffle of 3/4 braced ply. Also adjusted the seat so there is a little gap at top of less than inch, if someone sits there it flexes back otherwise there is a little opening. I guess it depends on how the seat is made. Sub frequencies can go around corners, but at least you get the idea of how loss happens.

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