My thoughts on the 'ski pass' subwoofer box

[Langertown]

I've gone through a few iterations on my speaker system on my E36 over the years. I'd like to share my thoughts on where I got to where I am now, maybe it will save you some time and money.

One thing I hate about reviewing speakers is you have no idea about the other person's tastes or experiences. For all you know, I have no ears at all and only feel vibration, or maybe you are reading this and you prefer your music all tweeter. To baseline where I am at, my home stereo is a Primaluna dialogue with a pair of Goldenear Triton twos, fed by a Simaudio moon 280D DSD. If you are interested, you can read more about that setup here
https://www.stereophile.com/content/...ated-amplifier

So, moderately high end. I've also spent enough time in fancy hifi shops to hear some extremely good stereos.

I only say this to demonstrate I'm not 12 years old with ipod headphones as a reference.

Now, my intention has never been to get to that level in my car. For one, the convertible is just way too loud and rattly. Plus I want to be able to get a set of golf clubs in the trunk, so I need my trunk. An E36 Convertible is just not the environment for it. That said, there is no reason we can't make something decent, which was my starting point.

For this post, I want to speak to a project which is recommended a lot here in this forum. Which is the ski pass box detailed in this thread
https://www.bimmerforums.com/forum/s...rtible-Sub-Box

Bianca98 was a big inspiration to me to take on that project and I had a ton of fun with it. I ran that sub for a number of years and just recently upgraded.

So let's get to the heart of it. With all respect to those who have come before me, I don't think that the ski pass sub is an ideal solution. The reason really comes down to the physics of it.



if you use the recommended drivers, which is an alpine 8 in an approximately 0.21 cubic feet box, you wind up with a sub that is peaky around 80hz and cannot play low notes. I modeled the box in winisd and I am sorry to say I lost the file, but from memory you wind up with a response curve something like this.


The response curve is something that is very difficult to tune around, you can't just boost the lowest notes because the box can't physically do it. What this means is that you get a lot of bass, but you don't get good deep bass. You'll also find that some bass notes are just way too loud, but not in a good way.

So, after using this for a few years and also experimenting with polyfil and additional bracing, I wasnt happy. I made the decision to upgrade. Now, one thing that has been really cool in car stereos is that manufactures have been working on very small enclosures for years now. What I eventually decided on was a JL audio microsub.
http://www.jlaudio.ca/cp108lg-w3v3-c...-systems-93133


What I found is that these will fit perfectly in the space under the convertible top. So, I lose 11 inches of trunk space, but I can pretty much still use it for everything I used it for beforehand. Importantly, this thing plays low, loud and deep. One thing that I never liked about the ski pass sub is that top down on the highway, you couldn't hear it. This thing is much more powerful. It will rattle the windows. it will require dynamat, it sounds much bigger than it is. If you haven't heard one of these, go to a car audio shop and have a listen. They are way louder than you are expecting, I guarantee.



So, if you are looking for a pretty good stereo without giving up your trunk, I would recommend this. Instead of making a ski pass box, get yourself one of these off of craigslist or something. You can find them for pretty cheap used.

I also upgraded my deck to a pioneer 80prs and amp to a JL XD600/6v2. Don't forget about the source, it all makes a difference.

[verobeach97]

thanks for sharing! I have ski pass box/8" alpine... and you're absolutely right - there is no sweet spot with it. i have to tinker with equalizer settings for different tunes, whether roof or windows are up or down. it looks great, but it's not great sound. i think i will give this a try and report

[BKKBeemer]

Good post - always good to hear about different opinions and different solutions.

I had a ski-pass box at first, and really wasn't impressed - I had to drive it so hard to get decent low-end that the speaker didn't last long.

I then built a box using the dimensions that Trayson posted, but while he has 2x12 subs I just have 1x10 (firing upwards, towards the cabin - almost through the ski-pass) - it kicks, but takes up too much space.



(Correct me if I'm wrong, but) I am sure that I read that the direction of the sound waves affects the frequencies and how they project into the cabin, and that tests suggest 'rear-firing' subs have the best response.

I'm going to re-think my setup a little later in the year and would quite likely go for a smaller ported box, and plan on experimenting a bit with sound directions.