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-   -   Alpair 10.1 in a car - enclosure design... (http://www.diyaudio.com/forums/full-range/214042-alpair-10-1-car-enclosure-design.html)

stochastic 7th June 2012 07:17 PM

Alpair 10.1 in a car - enclosure design...
 
Hi, I'm in the slow process of building a car audio system in my new car. I've already built a diffuser into the headliner (doesn't look all that pretty, but doesn't look horrible). I've got a CSS SDX10 sub that'll go into a sealed (I'm pretty sure) enclosure in the rear, and I've got a pair of Mark Audio Alpair 10.1's that I plan on putting in the corners where the dash meet the windshield. I'll probably be crossing the speakers over around 100Hz so low frequency extension on the Alpairs isn't needed - but if I can get the extension then maybe I won't high-pass the Alpairs.

My question is on the enclosure design for the Alpairs - I have nothing built yet so all is flexible.

My current plan (based on the limited space I have) is to create a fiberglass enclosure for each speaker that runs slightly up the a-pillar (about 12" or so) and also runs along the dash just under the windshield. The dash portion of the enclosure will be about 3" wide by about 1-2" tall. It will have either a crescent moon or an eye cross-sectional shape to it and will be about 23" long. I think the general cross-sectional volume of the a-pillar enclosure portion will be in the same ballpark as the dash portion. Directly behind the speaker itself will have a larger volume as it will be mounted on an angle in the corner.

Should I design this as a sealed enclosure or put open holes at the center of the car where the two boxes meet to turn the enclosure into a TL? If it's a TL, should I direct the ports with an angle toward any given direction? Will a center porting of these enclosures loose stereo imaging? Do I even need an enclosure this large if I'm high-passing the speakers at 100Hz - would just the a-pillar portion of the enclosure suffice?

Any other ideas on my design? Am I setup for failure or success? And yes, I know a car is a poor acoustic environment for audio reproduction, but I'm enjoying this project and the challenges that it includes.

gafhenderson 7th June 2012 08:04 PM

i put my MA chr-70.3's into small reflex boxes mounted on my cars rear shelf. they do a pretty decent job in a crappy environment.

chrisb 7th June 2012 09:45 PM

Mark should probably address this, but I'd be really careful ( as in wouldn't even thinking about) running any lightweight metal cone drivers in an auto or boat system. CHP or EL70, or Fostex FFxxxWKs, sure - even then I'd want to XO them above 150-200 HZ and tread carefully with the volume control.

stochastic 7th June 2012 10:28 PM

Quote:

Originally Posted by chrisb (Post 3051629)
Mark should probably address this, but I'd be really careful ( as in wouldn't even thinking about) running any lightweight metal cone drivers in an auto or boat system. CHP or EL70, or Fostex FFxxxWKs, sure - even then I'd want to XO them above 150-200 HZ and tread carefully with the volume control.


Care to explain why? (consider me a newb to the DIY scene)

chris661 7th June 2012 10:39 PM

The metal cones are very very thin, so can be easily damaged where a paper or poly cone might shrug off any accidental collisions.

That said, the comments about crossover points say he's on about too much LF energy getting to the drivers. I don't think that'll be a problem, and I'd expect a 100Hz XO (so the subwoofer's position isn't obvious when you hear it) would be fine: the fact that you're wanting to use MA drivers says to me you're looking for more quality of sound than being able to do hair tricks.

Chris

planet10 7th June 2012 10:49 PM

1 Attachment(s)
10.1 should be more robust than 10.2 in this environ, i'd build a sealed cabinet and try to get the acoustic roll-off to as close to the intended XO as possible (3-6 litre).

dave

stochastic 7th June 2012 11:02 PM

Thanks Dave.

Chris I sort of doubt that I'll have any accidental collisions with them on the dash behind grill covers. Anything is possible I guess, but I got a good enough deal on them from Bob at CSS (his old stock, mismatched colors) that should anything happen I'll not be too heartbroken. Still sad, just not heartbroken.

So is sealed the obvious and simple choice then? No high-pass filter?

planet10 7th June 2012 11:06 PM

I'd still put a 1st order hi-pass on them (PLLXO -- a single cap per channel on the input of the A10's amplifier).

dave

stochastic 7th June 2012 11:15 PM

My amp (Memphis ST1300D) has an optional 18db sloped high-pass on those channels. I'll probably just use that unless there's any reason not to (phase coherence?).

Edit: I'm also going to be running a Rockford Fosgate 3sixty.2 digital signal processor that will digitally EQ everything, so maybe I've already waved goodbye to phase coherence?? Like I said, I'm slightly new to the DIY scene - loving it though.

planet10 7th June 2012 11:28 PM

Then i'd go that route...

dave


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