I just got an Infinity 10" sub and want to know which way it should face in the trunk. I would search but it is not available at this time. I would like to know the pro's and con's of each since I only want to mount it in the trunk once. I plan on mounting it as close to the back seat as possibe to maximize trunk space.
Thanks for any advice in this matter.
Marc

 

facing the sub to the seats usually sounds tighter and less boomy. facing the sub into the trunk produces higher SPL. best bet is to try both sub placement positions and see which one you like best.

 

Actually, sub frequencies are omni-directional. It should not matter, as long as the box is properly built, when it comes to sound. The exeption to the rule is when you install in a car with a hatchback. In that situation, rear facing subs sound better because they bounce sound waves off the hatchback window back forward essentially making the sub sound louder.

As far as looks go, it is all a matter of preference. If you have a sub that has a cool magnet structure, face it back. If your cone is cooler, facing forward. It's your choice.

Here's mine:

http://www.clublexus.com/gallery/sho...cat=500&page=1

 

but when i faced my sub towards the cabin...the bass sounded tighter

 

it does make a difference.

 

Ok fellas, I'll bite....

Why does it make a difference?

 

im no audio expert but when i installed mine and my friends system we turned our boxes around to see which sounded best and the subs facing the trunk gave the optimum sound to our ears.

 

Boundry effects can give you up to 6db SPL gains by facing the sub towards the back of the trunk.

 

So to dumb it down for us common folk , does that mean it will be louder facing aft towards the trunk door?

 

Ok....

Boundry effects are dependant on the placement of the sub in respect to resistive boundries. Proper loading in a vehicle can yeild as much as a +6db increase in acoustic power. This benefit is limited to frequencies where the distance from the driver to the boundry is less than 1/10th of a wavelength.

So, put a sub in the back facing the trunk. The sub is appx 2.5' from the back of the vehicle. Frequencies that are in the 25' (2.5' = 1/10th of 25') radius level will receive a bass boost of +3db or more. For reference, 20hz waves are 56.6' and 100hz waves are 11.32' in length (propagation). A 25' wave is probably in the 55hz range which is where you would receive the boost.

Due to loading characteristics, the sub will be able to "breathe" easier facing the open space of the trunk which will allow for a better use of mechanical energy than the restrictive confines of facing it towards the seat.

So, in essence, facing the sub towards the seats will increase the high-end of the bass frequencies making the sub more "punchy" whereas facing the sub towards the rear will increase lower-end frequency response and higher SPL.

 

That's exactly what I was thinking

 

LOL

U asked for it

 

Great write up!

The only thing that would possibly make this not work is inability for that wavelength to penetrate thru the back seat into the car's cabin. In other words, does this formula work if the frequencies have to travel thru a restrictive area such as the back seat?

The only reason I say this is because it has been my experience that the above mentioned "formula" does in fact work (this is what I was referring to in layman's terms when I said it worked in hatchback cars) but only when it is bounced off a rear surface such as a hatchback and bounced forward un-restrained. I also found the same when the rear seats can be dropped and you have pretty much a straight shot into the trunk from the cabin. I have not really heard a big sound difference otherwise when fired thru a port in the deck or arm rest.

 

The problem with a car environment is that frequencies in that range or lower are more-or-less felt than heard since the waves propagate out so far the lower the frequency. That's why you can hear sub-bass in your house (shaking your windows) via cars passing by. You will primarily feel the force of the pressure than hear the actual full frequency. Utilizing proper loading simply increases the sound pressure that is felt, tho not necessarily heard...

 

waht about my car...i plan on facing the subs toward the seats...but when you fold my armrest down it goes right into the backseat...i made a hole...how will that work

 

That is the same setup I will be implementing in a few weeks. There is no problem with the sub facing the back of the seat and firing through the arm rest (in the down position). You simply won't get the SPL boost you would receive with the sub facing the back.

The main reason I'm not facing the sub towards the rear is to limit the amount of trunk vibrations. The least amount of "panel singing" I have, the better. I don't want to put Dynamat all over the trunk if I can help it.

 

www.installer.com/tech/aiming.html

 

Nice find!!

Anybody wanna change their mind now????

 

Pretty much the same as I've been stating other than the option of sub in back of trunk facing backward which happens to make the trunk worthless.

Good 'ole Eddie Runner. I still remember him rambling on RAC back in the days...

 

Actually, what that link was saying totally contradicts what you are saying about "boundries".

I have a fully functional trunk and have the subs facing backwards (magnet out).

 

Mine are in the floor, I can't really get anything out of the explanation. Doh

 

Doesn't matter for me lol

 

Eddie is primarily talking about sound wave destructive vs. constructive interference which is caused by sub positioning.

 

WHAAA? Please pass the good ganja your smoking this way!!!

The article is titled "woofer box aiming". How'd you get to destructive vs. constructive interference out of an article titled "woofer box aiming"???

 

Well I guess the only way I will find out for sure is to move my subwoofer around after it warms up a little bit here in Mass. I installed mine facing the rear seats and am happy with the bass output. I wasn't looking for a loud wake up the neiborhood boom, just some nice low end to compliment my Infinity Kappas up front.
Thanks for all the input on this topic.
Marc

 

First of all, I truly respect Eddie Runner. And yes, he is still around on RAC. He knows way more about car audio than I do. However...there are plenty of other people that also happen to know more about me on RAC that disagree with Eddie from time to time.

So.

Let me say that the only true way to find out what way a speaker box sounds better is to put it in the car and move it around until you get the results you like best. Our benefit is that since we all have the same car (within reason) then the results will be biased only by our selection of subwoofer, box, and install. My box with a single JL 10W6 sits in the driver-side corner of the trunk pointing to the right towards the passenger-side. Not as loud as I like, but very musical.

I strongly believe that no back seat is going to keep the bass out of the passenger compartment. It'll go right through it. Vent hole in the package shelf or not.

I also strongly believe that more bass is not necessarily better. My goal is to have the bass blend in perfectly with my front soundstage and sound the way it's supposed to sound...not boomy, distorted, but natural. Just because the bass is louder with the box facing this way or that doesn't mean it'll sound better.

It's extremely complicated and a never-ending debate among the experts. I say we just all use trial-and-error and find what we like.

I would personally like to hear from people that have their boxes facing into the back seats with the front of the box sealed off from the rest of the trunk. I am planning an aperiodic enclosure as we speak wth two Soundstream EXACT10s. I plan on sealing off the entire trunk from the cabin. From what I've heard, it will result is amazing SQ, with the sacfice of decreased SPL. Which suits me just fine. I definitely plan on posting the results when I'm finished.

Tony

 

Oh yeah...if you look at page 2 of Eddie's tests (his actual test results in a Deodge Neon, Chevy Tahoe, and new Beetle) you will notice that the largest difference in volume is in the 50-60Hz range when the box is facing the rear of the car. The BIG difference comes after 100Hz. When the box is front facing, response above 100Hz drops off considerably more than the rear facing box. I don't know about you, but none of my sub system have ever played as high as 100Hz. I usually low pass my sub(s) at 70-80Hz.

If you want that volume increase in 50-60dB (rap music, boom, thump) then you may like the box facing the rear of the car. If you want a smoother frequency response, try facing it towards the front.

Of course, the rear facing box does play louder accross the band, but the 50-60Hz range is probably why it sounds louder to most people.

Tony

 

anyone have thoughts about facing them up? Just asking because with my new huge two 12'' box, thats the only way I can get the box to fit in the trunk which makes them fire up into the rear deck.

 

I got some of that really GOOD ganja!!! Want some????

Eddies research revolved around an issue where opening the hatch of a vehicle made bass better, so he decided to experiment with sub placement in that vehicle. His research showed that in certain locations, he was receiving a cancellation effect. This is known as "destructive interferance" where the waves are 180deg out of phase, thus causing cancellation at the effected frequencies. His first illustration shows this effect. His other illustrations show him moving the box to locations where he ended up with "constructive interferance" where the traveling waves, which are the same frequency, interact and are "in phase".

The above is completely different than loading characteristics which include boundry effects, propagation vs. modulation and speaker coupling characteristics if sub pairs are being utilized.

 

i got that and an amp for $99.00 from Best Buy... But I think I am going to sell the amp, because I heard it sucks... heh.

Atleast somebody else had the thought in their mind that it was a bandpass box...

 

You guys are close, but you're not there yet. The box, ultimately, makes the difference. There are so many design choices available, but I will just talk about simple sealed boxes for now. The frequency response and SPL are all determined from the size of the box relative to the power you are running to it. Once you have determined what you are going to build, and what frequency response you are desiring, then comes the transfer function of the vehicle. You will also come into designing for distance of the wave travelled to find out what the resonant frequency of the system will be, so that the box can be properly tuned to the same frequency (for SPL), or tuned to a different frequency for sound quality. Some of the key factors are first in asthetics, what do you want it to look like? Do you need room for golf clubs, or would you just like to try to squeeze 4 15" subs in the trunk? With firing the subs forward, you need to build a bigger box. It will lower the tuning frequency, so it will sound fuller. You also must seal it off from the trunk. If the box is just sitting there firing forward it will sound like crap. If you build a nice baffle to seal off the sub to the ski hole, It will sound great. If you have a car where the seat folds down...5th gen...you guys are the lucky ones. You will sound better firing backwards every time. But with 4th gen, there is too much metal to get the air moving into the cabin. I have 2 12's firing into the ski hole with a big box, and only 300 watts and it rocks. I built a box for 96MADMAX with 4 10's firing forward, and it rocks, a little harder to design and seal off. But you should hear 4 10's with 1600 watts RMS....OUCH. The bottom line is that there is more in the design of a subwoofer "system" than just putting it in the trunk and hooking it up. The box must be built for the sub at a specific power level. If you figure out where you want your subs to sit in the car, measure how far the cone is from where the dash meets the windshield. If the subs are firing backwards, you must measure to the trunk, and then forward to add the distance of the reflected wave. once you have this measurement you can find the resonant frequency by dividing the distance by the speed of sound (1320ft per second). Then with the Thiele small parameters you can design a box that is tuned to match the frequency you came up with to build the best sounding box for the design and placement you have selected. The things to remember are the subs out there today claim small box usage, and they will work, but take a 12 that will work in .75 cubes, and put it in 1.5 cubes, and it will blow your mind. I built a system in an Explorer a few years back with 4 JL Audio 12w4's in 8 cubic feet, with a 1400 watt PPI amp. It qualified for the IASCA World Finals doing 158.4db. Three weks before finals he went to another shop, bought 4 15's and another PPI 1400 watt amp, and with their design was only doing 156.2db. $7000 later with poor design was more than 2db below where he was with half the power and smaller subs. Good Luck I hope this gives you something to think about.

 

Actually, with the origional question being "which way to face my sub", we were on track as this was a positioning question instead of an all-out installation question.

I definately agree with your statements except the utilization of a larger box for front-firing configurations. I have seen this done on numerous occasions and the end result has always been a loose sub and eventual sub failure from over powering.

Unfortunately, anything technical discussed in this thread will not be understood by most of the viewers nor do they really care, so, the simple answer is to build a test box and move the sub around until it sounds good to them.....

 

Oh yes. This is why I am choosing an aperiodic design. All the benefits of a large box in a very small enclosure. Only drawback is reduced SPL. Which is fine with me.

Tony

 

I tend to stick with my "tried and true" JL 12w6. Relatively small box (1.25cf) and great sound qualities.