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Port placement directly behind the sub

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Topic review
   

Expand view Topic review: Port placement directly behind the sub

by GlassWolf » Sun May 02, 2010 11:58 am

honestly, when I ran the Festiva's two CV 12" subs on the Orion 280GX ported, I never had an infrasonic filter of them, and they never unloaded on me, and I hit some hellishly low notes on that setup. Low enough that I couldn't hear any sound from the stereo, but the steering wheel would be vibrating about 1-2" like a blur. (Floyd's DSotM heartbeat, and KLF's White Room CD were the two that were the worst.) So yeah, I was driving 160 watts RMS per sub, on subs rated for 250 watts continuous (125W per coil)

It's a lot to do with the entire setup really. Hard to use blanket statements for some things.

by Bwcad1 » Sat May 01, 2010 8:41 pm

GlassWolf wrote:boxes aren't large enough to really worry abour cancellation, and the port being opposite the sub is fine. It's not really about the wave direction so much as restriction of airflow to affect damping of cone movement.
What you do want, is half the diameter of the driver's cone between either end of the port and any obstructions.

In short on cancellation, the old argument is to angle the side of the box opposite that of the driver(s) to avoid waveform cancellation. The reality of the situation is that the box isn't big enough to even affect a harmonic of the frequencies generated by a subwoofer, so it's essentially a moot point, and just done to make a box fit in a given location now, or to appease people who don't really understand acoustics.
Exactly. Even the loading issue only comes into account when running high power around the limits of the mechanical suspension. The suspension of a driver should dampen any side loading until you start reaching the mechanical limits of that suspension.

by GlassWolf » Sat May 01, 2010 6:07 pm

boxes aren't large enough to really worry abour cancellation, and the port being opposite the sub is fine. It's not really about the wave direction so much as restriction of airflow to affect damping of cone movement.
What you do want, is half the diameter of the driver's cone between either end of the port and any obstructions.

In short on cancellation, the old argument is to angle the side of the box opposite that of the driver(s) to avoid waveform cancellation. The reality of the situation is that the box isn't big enough to even affect a harmonic of the frequencies generated by a subwoofer, so it's essentially a moot point, and just done to make a box fit in a given location now, or to appease people who don't really understand acoustics.

by Tim » Sat May 01, 2010 2:52 pm

colemanyoungerinalaska wrote:i wanna here what you have to say about standing waves and cancellation

seeing as how I will understand approximatley half of what you say anyway.....yeah sure im up for hearing what you have to say about it.

Tim

by colemanyoungerinalaska » Sat May 01, 2010 11:48 am

Bwcad1 wrote:im not going to get started on standing waves and cancellation here because there are to many people that will argue with me about it, i always thought the same thing but obviously i was wrong. I can go snap a couple pictures of my infiity's and JBL's with rear ports.

but when you think about it just because a port is directly behind the sub doesn't mean its gonna unload. the port diameter would have to be larger than the magnet assembly and at least half way up the cone. The spl guys are running this is fact by the way. 16000 to a pair of 12's directly in front of a 6in or bigger aero.

i wanna here what you have to say about standing waves and cancellation

by Tim » Mon Jul 27, 2009 3:48 pm

scotts1000rr wrote:Aren't we all?

nah dude he said ported "to" the rear, not ported "in" the rear..LOL

AHAHAHAHAHAHAHAHAH i crack myself up, i really just dont know what I would do without my humor...

"Lord I apologize and be with the starving pigmies down in new guinea"
LOL

tim

by audiobass10 » Sun Jul 26, 2009 11:04 pm

colemanyoungerinalaska wrote:the seats fold down
should work well then.

by colemanyoungerinalaska » Sun Jul 26, 2009 10:46 pm

the seats fold down

by colemanyoungerinalaska » Sun Jul 26, 2009 3:45 pm

audiobass10 wrote:Should be fine. its only 1.5 cubes so worse comes to worse u can rebuild pretty easily if it doesn't meet your expectations. Do your seats fold down or do you have a ski hole?
yeah it wont take that long to redo i think it took an hour and half to make including beer breaks

by scotts1000rr » Sun Jul 26, 2009 1:07 pm

NorthQuad wrote:I'm ported to the rear.
Aren't we all?

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