Walling off blazer, ported or 4th bandpass?

[///M5 2,833]

If your definition of quality is a flatter response then yes it is a very lost cause.

Your perception of the bandpass vs ported isn't correct, there is something in your memory confusing it or possibly your current box is all wrong. Considering you feel the box "peaks" at 40-50hz I would suggest that it isn't ported to 30hz like you think it is, not even close actually.

[95Honda 486]

The peak will almost always be in the same general range in vehicle when you don't change box size or woofers. Tuning at 30Hz just lowers the overall system efficiency and extend the low end cutoff. The high tuning just exaggerates the peak(s) in the vehicle. You van easily see this when you model a 4th order ported box and change tuning, there still always is a funny shape to the curve that follows the same general area. The overall peak changes, but there is still alot of energy in the same region, this is just amplified in a car environment.

A 4th order bandpass is potentially more efficient than a 4th order ported box, if it has less bandwidth. In other words, if you are more efficient with the 4th order bandpass, you have a narrower pass-band than the standard 4th order ported alignment, this is physics, no way getting around it. This is not a good attribute for sound quality.

Until you start dealing with horns, don't even bother with talking about the differences of matching driver to air impedance in the car environment.

The questions you asking are above the help you are trying to get. You seem like you already have your mind made up.

Bottom line is, depending on alignment, all 3 enclosures can have ruler flat response (anechoic). The major different between the 3 will be: efficiency, bandwidth, group delay and size. But I think you already understand all this.

[creyc 1]

Thanks 95Honda, I think you're right. And I'm not intentionally being obtuse about the type of enclosure I want to build, it's just my previous experiences which turned out well with bandpass boxes.

Here's a calculated approximation of the setup in my old truck cabin:

Gray is ported

Blue bandpass

Yellow sealed

As predicted, the bandpass enclosure turned out excellent. Later on I had Pete K. design me something for the same application and he came up with another 4th order bandpass which worked nearly as well with just one subwoofer. I suppose this is why I continually patronize these enclosures, for me they have worked, although I don't completely know WHY.

[95Honda 486]

Are you using an pre-programmed cabin gain estimation, or did someone make measurements with a reference source?

The only reason I ask is because it looks like the vehicle has falling response in the 50Hz region (most obvious with the sealed box curve) which is odd. But you never know, there can be all kinds of nulls in there.

For the bandpass to have a flat response in car and the ported and sealed to have falling 50Hz+ response would tell me the bandpass has a rising response from the lower F3 on up.... This may be desireable in your truck and that is why you like the sound.

I have done alot of bandpass boxes. Some for home audio, some for car. I have had mixed experiences, but liked the way the home ones turned out more of the time.... Maybe because the home environment was less augmenting....

[///M5 2,833]

If you are using measured gain, it is even more curious that you felt a peak at 40-50hz. Obviously it could be your car's peak, but from those curves it isn't your subs.

[Cheesemind 0]

Wow, all this is WAY over my head... But very interesting...

[mlstrass 1]

what type of music do you mostly listen to?

I did a temp wall in my car a few months ago. 4 15's in 12cubes @ 40Hz (AQ subs) and it did pretty well. Box was too small, so it peaked rather high on the TL, upper 40's, but sounded solid on music and was insanely loud. Kick drums would BEAT you in the chest.

I've read numerous times that the mids should handle kick drums, but most of the rock I listen to it's coming from the subs. I HP my mids @ 63Hz and LP the subs the same.

4 15's walled off with enough power will have a TON of impact. I would assume SQ isn't a major concern, but you should be able to make it sound pretty decent if the box size/tuning is correct and then some EQ'ing after the fact.

[creyc 1]

Right, it's not in any way a SQ setup (in a car whats the point anyways, I've got home systems for that) but I want it to slam and sound clean.

I want to be reasonably flat from the lows in chopped and screwed songs, up to the higher bass in some rock rock songs and electronic music. I usually cross my subs over at 63-70Hz so this would probably be the upper limit for desired response.

[mlstrass 1]

I'd do a ported wall tuned around 30-32Hz and be prepared to smile a lot and go deaf...