A-pillar tweets

Thanks,
Collyn and Lex

Just to give you a bit of detail to what I am working with. I am working on my 2001 PT Cruiser. The stock door locations will take a 6.5 woofer and there is a cut out in the dash for a 4 inch mid.

I have a Focal 165w3 3-way set and need to figure out where to mount all of the speakers. I am going to put the 6 in the door and I wanted to put the 4 in the top corner of the dash and the tweet in the a-pillar.

On the a-pillar ther is enough space to flush mount the tweet faceing the center of the dash with a slight angle towards the glass, and there is another mounting spot that will have the tweet aimed directly at the listener(drivers tweet facing the driver & passenger tweet facing the passenger).

I am really just wanting to know if I should put my front stage in these areas or if I should just go with having an experienced shop build me some comp worthy kicks.

What do you guys think?.

[Scott Buwalda]

Everything written here is spot on the money. I can barely think of many things to add. But knowing me, I'll sure try.

First of all, in the PT, do NOT aim those tweeters at your ears, or the opposite seated passenger's ears. The beauty of car audio speakers is that, more times than not, they are designed to work optimally off-axis. Compare for a moment the waterfall plot of a high quality car tweeter at 0 degrees, 30 degrees, and 60 degrees off axis. Often, the very best car audio tweeters will have a negligible difference in frequency response between the three degrees of axes in the critical bands of their operation (up to around 12 or 14 KHz). The only frequency range that can *sometimes* suffer slightly is the very highest treble when a speaker is placed off axis. This is not that big of a deal, as there's not much going on in most recordings above the -3 dB down point of most tweeters (especially metal domed ones)...typically 16 KHz and above. Not only that, but this is nothing a little EQ'ing wouldn't fix if you're trying to pass an RTA test with said tweeters.

As a real-world example, I am currently using MB Quart QSD series tweeters in the pillars of my competition car. These are well damped metal dome tweeters that work extremely well off axis. Currently, my equalization for the tweeters is as follows (it just so happens I brought my tune it to work this morning to type it as a reference for me at finals):

Left:

6.3 KHz = +1 dB
8 KHz = -1 dB
10 KHz = 0 dB
12.5 KHz = 0 dB
16 KHz = -1 dB
20 KHz = -1 dB

Right:

6.3 KHz = 0 dB
8 KHz = 0 dB
10 KHz = +1 dB
12.5 KHz = 0 dB
16 KHz = 0 dB
20 KHz = 0 dB

As you can see from the above, the pillar-mounted tweeters in the Expert 240SX are seeing no ill effects to the tunability of the car for sound quality operation by being relatively off axis to the listener's ears.

To make pillar tweeters work, they have to be crossed over higher than the magic number: 5 KHz. You cross your pillar tweeters over lower than 5 KHz, and you'll probably have split images, near side bias, etc. Mine are at 6.3 KHz. The ultimate song to use is by Dire Straights, "Calling Elvis." I think the album is "On Every Street." The lead's voice is recorded hot at around 5 KHz. With improperly crossed pillar tweeters, you'll hear the funamental image at the center of the car, and the near-sibilance overtones of his voice in each pillar. It's quite freaky hearing his voice in three different places.

And of course, your mid needs to play to 5 KHz or above, without cone breakup, to be effective. Many ask me why I have motorized the kick panel speakers in my car. If they were used as midbass drivers only, this would have been wholly unnecessary. But they're not. They're playing 6 full octaves of music. Short of three octaves on the low side, which are being faithfully reproduced by the 12" sub in my dash, and two octaves on the high side, which are being faithfully reproduced by the pillar tweeters, my midrange speakers are the closest you could possibly come to single point sourcing. The true luxury is having a digital processor where you can turn speakers on and off (I use the Japanese Domestic Market Carrozzeria RS-P70xII, the only one in the western hemisphere, far as I can tell). I have listened for HOURS with just tweeters playing. They are dialed in. 6.3 KHz is the magic frequency in my car, with a relatively steep slope. There are very little imaging cues from the tweeters in this pass band (other than when a tamborine or cymbal is far left or far right). There's DEFINITELY no vocal imaging from the tweeters. That's why they work.

Hope this helps....

Scott

PS: And like Mike, I would be more than happy to demonstrate this phenomenon at the IASCA finals. I'll lower the x-over frequency on the tweeters, and you can make up your own mind. The goal is to not "hear" the tweeters. The goal is to hear treble.

I am not at home so I can't read the specs for the crossove network for my Focal 165V3 (is kept calling them 165W3), but most likley I will need to creat a custom crossover network for my set if I plan on putting the tweet in the a-pillar. Unless Focal has crossed the tweeter over higher than 5Khz.

If that is the case then I would have to find some one far far away to build it(cause I don't trust anyone in NM.). Or, go to a shop that could build me a set of kicks that look as well as sound comp. worthy.

You've got a fleet load of McIntoshes laying around the garage, why not go active with really steep slopes?

Scott, how exactly are your tweeters mounted? I'm sorry if I missed anything other than "off axis" in your post......are they completely flat to the panel? Any angle at all? If so in any particular direction?

What would be the immediate problem with focusing the tweeters at the near passenger? (Drivers side firing more towards driver - passenger side firing more towards passenger)

Thanks in advance.

I couldn't have asked it better myself.

Lakersfan,

If I were to do it all active what Xover could handle all 6 channels? I'm not sure my Macs have a 5k xover point.

Hey Scott,

You think I could take a few moments of your time Friday b4 finals to listen to my car and help me get the image better from both seats?

Originally posted by BMW323&PTC:
I couldn't have asked it better myself.

Lakersfan,

If I were to do it all active what Xover could handle all 6 channels? I'm not sure my Macs have a 5k xover point.

AudioControl 6XS?

If I ever get the money for another amp, I'm just going to cascade 24XS's. I like the idea of having the variable phase control to make sure there are no cancellation or peaks in the response.

Most of the time reversing the polarity over-shoots the sweet spot for the center a little, or atleast it seems that way to me.

[ October 10, 2002, 12:51 AM: Message edited by: HiTec ]

[Scott Buwalda]

Hey guys:

First off, the best way to think about how to mount and aim the tweeters is to consider the windshield your wave guide. Yup, everyone has wave guides in their car! LOL Use it to your advantage. Don't aim tweeters straight at the windshield, and don't aim them too far away from your windshield. I like to use the term "coincidental." It's basically an additive effect that you're looking for.

In my car, I found that aiming the tweeter drivers straight at each other, with only a very minor pitch toward the windshield was the right way to go. There's about a 10 degree usable area there by which pillars will sound great. In my car, for all intensive purposes, the tweeters are almost 90 degrees perpendicular to the windshield. With the slight pitch toward the windshield, I might say closer to 88 degrees perpendicular. An easy way to set a baseline is to get a very small wood worker's square (less than an foot long). Start the aiming process for pillar tweeters by placing the square against the windshield glass, and then arranging the tweeter cup so that it is completely perpendicular to the edge of the glass (not necessarily a foot out into the middle of the glass, because all windshields curve out). Then from there, you can start fine tuning about 5 degrees in either direction.

Any more on axis (toward your ears) will create localization, even at the higher crossover frequencies. It will also cause near side bias (see my explanation up above about how good car tweeter's have great off-axis response).

Any more off axis (pointing AT the windshield), and you'll have terrible early reflections off of the glass.

And to Jayson- I would be more than willing to help you, but unfortunately I am being judged Friday. I will be in town Wednesday night, and be around all day Thursday doing my cleaning routine. If you want to come search me down at the downtown Hampton Inn, I can throw a few minutes your way...but Friday's bad for me...last minute preps, pulling into the venue and setup, and etc. Complicating the matter is my parents want to see what this car audio competition thing is all about. Heck, I've only been doing it actively since 1991, and as a hobbiest since 1987. Maybe they see the writing on the wall? [img]graemlins/idea.gif[/img]

Scott