Subwoofer install question - tire holder removal

[Johntee540]

The key is you have to remove the Ski Bag Pass thru in order to get the bass from the trunk into the cabin. Otherwise you are wasting your money.

I built a cabinet that houses 2 12" Alpine R12 Subs facing forward. I cut holes in the metal behind the rear seat as well as took out the SKI Pass through. The Subs fire into the cabin through the rear seats. Works great - JT

[Mobius]

The key is you have to remove the Ski Bag Pass thru in order to get the bass from the trunk into the cabin. Otherwise you are wasting your money.

Absolutely not true. Though there is a lot of insulation between the cabin and the trunk behind the seats, there is very little through the rear deck. I have a pair of 10" Kicker Competitions in a bandpass box and they're only marginally quieter in my trunk than in the open trunk area of my friend's wagon. Bass is really tough to muffle. The E34 trunk does a very poor job of it; despite the many layers of insulation. There is little reason to remove the ski pass-thru, unless you actually want to pass things through it (which would be nice).

If you're running smaller subs and you're trying to get some midbass out of them, then you're going to run into insulation issues. The rear deck is practically transparent to anything below 100hz.

I built a cabinet that houses 2 12" Alpine R12 Subs facing forward. I cut holes in the metal behind the rear seat as well as took out the SKI Pass through. The Subs fire into the cabin through the rear seats. Works great - JT

This is a less-than-optimal setup. Though it makes logical sense that you'd want the sub ports facing the sound stage, the opposite is often true. It depends entirely on the accoustics of the car. In the case of the E34, there is a very obvious decrease in sub volume when I turn my box around so it fires forward. It can be very beneficial to utilize the trunk as a sort of 'secondary enclosure'.

[Incantation]

I have had a different experience. I have found the e34 trunk to be extremely restrictive letting bass through, so much in fact, that even after removing the ski-pass, firewall insulation, and also custom building a back/seat mount for amps out of 3/4 mdf, you can still hear more bass in the car if you open the trunk and allow the sound to come from outside the vehicle. I had the same setup in my acura legend and the bass pounded far harder through the back seat.

e34 trunk muffles everything.

[Mobius]

e34 trunk muffles everything.

Huh. Really don't know how you can come to that conclusion. My subs are only even getting about 100w a piece.

This box is much louder in this car than in my previous car (Volvo 240!) which had no trunk insulation to speak of (and a ski pass-thru, even). It's still being powered by the same amp.

Really, though - it's crucial that the subs fire towards the rear. There is a night and day difference in sound output when you turn them around. It's very tempting to think that firing them at the 'audience' is the best method, but that is not the case.

[rockyfeller]

I agree with Mobius. There are 2 way subs will sound good in a sedan....if you have fold down seats, like some other cars, if you place the box all the way to the rear of the car facing forward you will get phenomenal sound. Otherwise with cars without fold-down seats of at least with the ski-pass through like our E34s defintely a rear facing enclosure will yield the best results. Remember bass is low-frequency and you don't "hear" it from the front of the speaker. 90% of bass comes from the back of the woofer and out the ports. Once this resonates throughout the trunk the bass sounds wicked. Try it both ways if you don't believe me...I did.

[Johntee540]

That's interesting. This was a professional setup. They do the local Ferrari shops installs. Brian Mitchell's New Ferrari was in getting his usual A/V set up installed.

The Ports are also vented forward through one of the holes in the completely solid steel panel that BMW puts between the seats and Cabin.

There is this one legendary e34 on the IASCA Pro Series Stereo Circuit I had seen years ago - and this was the set up it had. This particular car is available to be seen on CarDomain if you search on 1994 540.

Based on a 2 hour commute (my Ear Dyno) and having done 6 of these types of systems in the past with IASCA contest winning Audio Techs whom I trust - I respecfully disagree.

Unless you open the sound passage from the trunk to the cabin you have no where for the low frequency a sub produces to travel. In otherwords you have nice eye candy for your trunk but no sound quality. My set-up can break up any Kidney stones you have using sonic waves if you are sitting in the back seat. - JT

[Mobius]

That's interesting. This was a professional setup. They do the local Ferrari shops installs. Brian Mitchell's New Ferrari was in getting his usual A/V set up installed.

Because that matters... how?

The Ports are also vented forward through one of the holes in the completely solid steel panel that BMW puts between the seats and Cabin.

Completely solid - yep. It's also completely impossible for sound to move through "completely solid" objects. I mean, when I close the door to my room, I can just crank up my stereo as loud as I want and nobody can hear it.

I wish.

Bass frequencies are the LEAST restricted by objects in their path. There's a reason you can hear the kid in the Civic thumping from a block away, through three insulated walls and into your bedroom at 3 in the morning. However, you can't hear any sort of midrange or high frequency sound until you're in close proximity to the source of the sound.

I'll say it again: It is very hard to stop bass from penetrating things. There are some not-so- physics formulas that will relate sound velocity with material elasticiy and density. Not surprisingly, thin-gauge sheet steel is almost completely transparent to frequencies below 100hz.

I only wish the science of acoustics was simple enough to say "hey, you point the bass port at you and you get the most sound" - but it is abolutely not that simple, and that statement is absolutely not true.

Regardless of how hermetically sealed you think the BMW trunk is, I assure you it is barely sealed at all. If you wish to disagree with that, you are welcome to. It seems, though, that you're only talking about your own experience with having someone else install a system in your car, and have never actually played around with a freestanding box in your trunk yourself.

If you live anywhere near NW Washington State, you're more than welcome to drop by and hear just how "little" bass manages to escape the precisely engineered acoustic confines of my trunk. I think you'd be shocked.

There is this one legendary e34 on the IASCA Pro Series Stereo Circuit I had seen years ago - and this was the set up it had. This particular car is available to be seen on CarDomain if you search on 1994 540.

Great. There was also a guy with a E34 525 who won IASCA trophies for mounting subs in his front fenders so he could listen to his Disney music in the most pleasing way possible (I'm not even joking).

If you want to push past, I don't know, say 140dB - then I can see the argument for needing some sort of method for increased airflow between the cabin and the trunk. There's no point of 140dB unless you're trying to win SPL competitions, so I think it's out of the scope of this discussion.

Based on a 2 hour commute (my Ear Dyno) and having done 6 of these types of systems in the past with IASCA contest winning Audio Techs whom I trust - I respecfully disagree.

That's wonderful. You never say you've ever actually tried to mount a sub in the 'sealed' trunk, though. That's what I'm arguing here.

Unless you open the sound passage from the trunk to the cabin you have no where for the low frequency a sub produces to travel. In otherwords you have nice eye candy for your trunk but no sound quality. My set-up can break up any Kidney stones you have using sonic waves if you are sitting in the back seat.

Again, thanks for the posturing - it's nice and all. But you're still wrong. Bass doesn't need a 'passage' to move in, and the E34 trunk is nowhere near sealed enough to need any sort of pressure-equalization ports to the passenger cabin unless you're really pushing some high SPL.

This prevents any air pressure movement from the trunk to the cabin. Thus defeating the purpose of the sub. I am not using a Bandpass Box. I had a custom enclosure built that is ported forward into the cabin. The Subs also face forward.

From your earlier description, it sounds like you are using a bandpass box? Then again, it was a vague description.

Again, to everyone else in this thread: Based on my experience with my car, punching out the ski pass-thru is completely unnecessary. Your mileage may absolutely vary; but before you go punching a hole there - try experimenting with the placement of the sub in your trunk. Just turning it around makes a LOT of difference.

Oh yeah, and if this is all eye candy, as you say, John - why does my box look like I stole it from a Civic? Sub-Tek.. haha.. I've had it and the amp since I was 16.

[Johntee540]

I especially like the picture of sound traveling across the curature of the earth. Look - I have thought and experiences on this subject. You seem to have different thoughts and experiences. We seem to disagree.

I am traveling to Seattle the week of Dec 13-16 and would love to see your set-up. Staying in Bellevue.

The reason I mention the shop and their expertise is for legitamacy. It is the best shop in DC and they consistently build IASCA Contest winners. Several Washington Redskins; Philadelphia Eagles and even NY Giant Players travel there to have their rides done. It may not matter to you - but these guys are not stoners playing with Car Audio in a casual manner. That was the point I was trying to make

You are very knowlegeable about this topic. You have strong views. Again - I disagree and thats cool. Where did you get that you are stealing Subs from a civic? I dont understand this one.

I have done several systems prior to this. I am particularly happy with the way this one turned out. This is the first system I have done- yes its only a month old - where once I am finished I would not change a thing. Most of my other Systems have been done in Landcrusiers; 4Runners with Open cabins and a lot of air to move to make sound. So yes I have never done a system in a trunk before - I am relying on professionals advice and expertise in this area. That's why you hire professionals. BTW - I had been planning this system for over a year - this story of opening the cabin to the trunk was a consistent theme at all the shops I spoke to and even on the AudioPhile Board here at Roadfly. The results I got compared to the system in my current Landcruiser is night and day.

So if you are up to it - I would love to hear your system if you are anywhere near Seattle the week of 12/13. We can meet have a coffee - listen to some good blues on your rig and compare notes about Sound. I would love to be schooled. - JT

[AZ_Jason_S]

Technically, I think in most cases the sub should face rearward and the box should be at the back of the trunk. Reason, reflected waves positively reinforce the speaker waves with minimal cancellation.

Now my opinion of the e34, it sucks for bass. I have a sealed box with an Image Dynamics 10 pushed with 300 watts of PPI Art Series power. I do have the ski-hole punched out. But my system is almost a 1 note system. Why? Because the trunk is like a vault and the ski-hole is a port. Now, my sealed box turns into a big ****in bandpass box. I don't like it. Every car stereo "expert" I talk to tells me BMW's and Mercedes are the most difficult vehicles to get quality bass from. Sure, I can get alot of bass up front through the ski-hole, but it comes in a narrow band.

The reason I am ranting about this is because I just tore my car apart to look for another solution. My next plan is to try the sub IB in the ski-hole since its rated for IB.

Johntee540 lets see some pics of that setup.

I especially like the picture of sound traveling across the curature of the earth. Look - I have thought and experiences on this subject. You seem to have different thoughts and experiences. We seem to disagree.

I am traveling to Seattle the week of Dec 13-16 and would love to see your set-up. Staying in Bellevue.

The reason I mention the shop and their expertise is for legitamacy. It is the best shop in DC and they consistently build IASCA Contest winners. Several Washington Redskins; Philadelphia Eagles and even NY Giant Players travel there to have their rides done. It may not matter to you - but these guys are not stoners playing with Car Audio in a casual manner. That was the point I was trying to make

You are very knowlegeable about this topic. You have strong views. Again - I disagree and thats cool. Where did you get that you are stealing Subs from a civic? I dont understand this one.

I have done several systems prior to this. I am particularly happy with the way this one turned out. This is the first system I have done- yes its only a month old - where once I am finished I would not change a thing. Most of my other Systems have been done in Landcrusiers; 4Runners with Open cabins and a lot of air to move to make sound. So yes I have never done a system in a trunk before - I am relying on professionals advice and expertise in this area. That's why you hire professionals. BTW - I had been planning this system for over a year - this story of opening the cabin to the trunk was a consistent theme at all the shops I spoke to and even on the AudioPhile Board here at Roadfly. The results I got compared to the system in my current Landcruiser is night and day.

So if you are up to it - I would love to hear your system if you are anywhere near Seattle the week of 12/13. We can meet have a coffee - listen to some good blues on your rig and compare notes about Sound. I would love to be schooled. - JT

[Johntee540]

Funny - I just bought my first Digital Cam yesterday. I am finally going to do the CarDomain thing. I am taking pics of the New Tranny / New Suspension/ New Brake System Process that is going on down at the shop to post there. When I get the car back home and off the lift I will post the picks of the install. And I will ask if my installer will entertain Email inquiries about e34 installs. - JT