This is for good preparation for the Mk2.

I've got a new car - a limousine. I bought a 5 channel amplifier (4 speakers in the front, 2 speakers in the back and one sub)
Everything is ready connected and I think it'll do fine with the Mk2 (currently there's only a factory tape deck mounted). I know the quality is not very good - especially the bass is not as good as it should and hopefully it'll be better with the Mk2.

But nonetheless I've got a problem with my Subwoofer.
I had the same sub in my old car which was a hatchback. And it's sound was great. Enough power.
But now in the limousine the sub is in the back of the car, separated from the passenger's space.
If the volume is a little louder you can hear the bass but not as loud as it has been in the old car. If you open the pack door (for the luggage, where the sub is you hear it very loud. So the back is just pretty good isolated agains noise (and sound also).
What could I do to make the bass' sound better without changing the car too much (to not loose the warranty)?

(I've already posted this kind of question in the General BBS. So Tony please forgive me for asking again. Noone had an answer which was really satifying till now.)



TeeMcBee

What could I do to make the bass' sound better without changing the car too much (to not lose the warranty)?
get a bigger sub


as you expand the space you need more power to fill it. would your home stereo be sufficient at the super bowl? they use massive power and broadcast systems because of the amount of air they have to move.
Your hatchback was considerably less volume than the limo (lucky for some!!) and the smaller (?) sub was enough. there is probably some equation like square the volume and cube the power or something. Any pro-audio PA guys out there?

____________________________
Murray

Sorry for not responding before now - did get your mail, but I've been seriously busy.

A few things to try:-

First off, trying wiring the sub 180 degrees out of phase with the rest of the system, ie. reverse it's polarity.
If that doesn't work, trying firing the sub towards the back of the boot (assuming it's not already). This is a good idea in general anyway, as you increase the path length to the listener, resulting in lower wave propogation. f that doesn't work, try positioning the sub so it's about 30-60cm from, and firing directly at the corner of the boot compartment.

If none of the above has any major effect, then you're going to have to somehow increase the airflow between the boot and the passenger compartment. If there's a 'ski hatch' option on your model, but not one fitted, then quite often there'll be a metal panel that you can remove in the centre of the back seat (behind the seat squab) without effecting structural strength. Failing that, about the only other option is to somehow cut ports through the rear shelf, then cover them with acoustically transparent cloth so they're not visible.

With the latter physical alterations to the vehicle, there is a slight danger you'll increase the amount of road noise entering the passenger compartment, but it shouldn't be too significant, and could probably overcome by a layer of Dynamat or similar applied to the boot floor.

Dominic

Cambridge Car Audio
http://www.cambscaraudio.co.uk

Now there's a damn good set of suggestions. You guys know your stuff there.

May I also add that some subwoofer amplifiers come with a polarity reversal switch so you don't necessarily have to touch the wiring.

___________
Tony Fabris

...get a bigger sub

I don't think that's the answer. Tee's problem is that the subwoofer is mounted in a separate compartment, sealed off from the passenger compartment, with no common air pathway.

All he can do with his sub is vibrate the bulkhead separating the passenger compartment from the trunk or boot, so that in turn the bulkhead will try and vibrate the air in the passenger compartment to produce sound. As this bulkhead is no doubt sound-deadening by design, it is not surprising that the performance of his subwoofer is disappointing. Even if he put a bigger sub and a bigger amp back there and got the decibels he wants, the frequencies produced by this second-generation sound would be greatly shifted towards the low end -- all tonality would be lost and all he would hear would be thump-thump-thump from the drums.

Dominic is right -- the only solution I can see that is likely to work is to open an air path from the trunk/boot to the passenger compartment, or else relocate the subwoofer into the passenger compartment.

tanstaafl.


"There Ain't No Such Thing As A Free Lunch"

Thanks a lot for all your help!

I think the bigger sub is no solution, too - like tanstaafl said.
I already thought about a way how to place the sub so that it can fire directly to the back of the boot.
Another problem I have is that there is a metal panel under the boot (parcel shelf). But there are some holes (for the standard-speakers) in it. I'll first try it that way. But I'll have to change the sub's chassis because it is to large to "stand" under the boot. Maybe I'll build a new one instead of destroying the old one.

When I'm finished I'll report you! Thanks again!

TeeMcBee

Another problem I have is that there is a metal panel under the boot parcel shelf). But there are some holes (for the standard-speakers) in it. I'll first try it that way

What kind of box dor you have the sub in? if it was something like a band pass box the options are better. Maybe you could get a suitable box (crutchfield?) and take a flexible pipe from the open port to neatly into the rear shelf holes. It could be installed well and unobtrusively.
This would possibly affect the tuning of the box but give you a great increase in sound.

____________________________
Murray

I already thought about that (flexible pipe). And I think I'll gonna try. I'll build the box for the sub by myself cause then I can vary the Size. And It's not too expensive (need the money for the Mk2 you know ;-).
The old box is a Bassreflex box (also self-build).

Give me a few days - I'll try.

TeeMcBee

Hi!

I'm back again with news. I've build a new sub.
I bought a new speaker - a 12" (30cm) Dragster and build a new box for that sub. It's a bassband box. well calculated to give the best power with a quite small box (It's only 40 cm x 41.5 cm x 40.2 cm)

The cost of the box was only about $12 plus $10 for a carpet ( to make it look like a good sub ) plus some hours of work + a few screws and a little silicone.

I have it now on the same place as my old sub was but it sounds a lot better.

TeeMcBee

I have it now on the same place as my old sub was but it sounds a lot better.

Are you saying that it is still isolated from the passenger compartment, i.e., no direct air connection from speaker to passengers? If so, I think you can get even more improvement by opening up some sort of air passageway...

tanstaafl.

"There Ain't No Such Thing As A Free Lunch"

Speaking of that, anybody know of any web sites with plans for (or discussions of making) band pass boxes? I am contemplating getting one for my Jeep Wrangler. It needs to be small and kind of oddly shaped so I would probably end up making it myself.

Thanks,
Mike

I've gone to a professional car-audio installer and he calculated me a bassband - box for the speaker I bought there without paying something extra.

There are several programs out on the net for calculating the sizes of hifi-speakers you could look there.
You have to know some parameters of the speaker you are using then you can calculate a box for yourself.

Or you go to a good hifi-studio and talk to some people - maybe someone is known in calculating speakers. You'll get a good sound out of custom-boxes

TeeMcBee

I've tried both - separated in the boot and taking away the back-seats to have one room and I noticed that there's not a too big difference with this new sub (there was a difference with the old sub - don't ask me why!)

In the backseats there is a possibility to open a hole to put some skiers through.
Do you know the design of a bandbass-box? the speaker is IN the box, not visible on the outside. There is only one (or in my case 2) holes with a Tube coming out of the box. I'll place the box so that the tubes coming out of the box point directly to the hole in the backseat. And I'll cover this hole with a thin, carpet which lets the sound through it. (Maybe I'll have to build another box to fit my car well and to not loose too much place of the boot with the same volume but different sizes in length and width).

There are only two problems left:

1. If I have the volume at a quite high level my amp seems to have not enough power - maybe I'll add a second amp just for the sub.

2. I listen to my music from tape and don't have a Mk2 yet!! (that's the worst problem! Low quality, High noise, No search via Index or name,... you all know the disadvantages of a tapedeck)

Having Reg# 948 I hope to be invited soon.

TeeMcBee

Thanks for the link. I have built a couple of basic boxes before, but bandpass is new to me. I was hoping someone could point me to a site with some theory and maybe sample designs? Non-Windows software would also be of interest.

I expected tfabris to provide me at least a half a dozen links by now ;-)
Tony are you out there?

-Mike

If I have the volume at a quite high level my amp seems to have not enough power

Careful, too little capacity is the perfect way to blow up a speaker.

Henno
ex 00120

That's the reason for me to find a fitting amp for the sub (and getting best possible sound of course)

TeeMcBee

Wanna links?

General infomation you can find here. I searched with www.altavista.com for bandbass. Or try something like +speaker +build . Many good German sites there but I don't know if this helps you. I'm sure there are some good english sites, too.

An example where you can see what it looks like.

Good luck in studying

TeeMcBee

I expected tfabris to provide me at least a half a dozen links by now ;-) Tony are you out there?

Yeah, I just never built my own subwoofer box before, and I've never built a bandpass box. All I've done is purchased a pre-built box from Crutchfield and screwed a subwoofer into it. Since I was just relying on the charts in their catalog, I really don't know anything about calculating box volume (I just know it's important to get it right).

I will say that I had a friend who built a rather nifty custom subwoofer box for the trunk of his Renault. It had (as Doug suggested elsewhere) channeled ports which ran into the passenger cabin under the back seat. It was pretty awesome. The problem was that it was made of particle board, so when he got a water leak in his trunk, all his work turned into mush.

___________
Tony Fabris

After some experimenting around and trying some differend Sub-Boxes if finally came to the point that my 5channel amp simply doesn't have enough power to drive the sub clean.

So I tried some amps and finally got a high-quality 4 channel amp. Now 2 channels are driving all speakers (1 channel left rear+front/1 channel right rear+front) and 2 channels bridged drive the sub. I've now mounted the sub-chassis into a closed box. I was told that it has the cleanest sound (but not less preasure than a bassreflex or bandpass).

I'm really happy with that solution - even though I can't change rear and front separately now - it sounds really good and clean now.

TeeMcBee
Got my Mk2! # 080000143