posted
First off I have my trunk most of the way sealed off from the rest of my car. My subs and port facing the wall that seals it. Leaving a good 6-7 inches for the air to travel.
I hit an astounding 154.2 with my two mass 12's. @ 62 hz. After the fact I went to leave and saw that one of my rear doors was not tightly shut. Thus leading me to beleive that possibly the same affect as opening a window.
Question. What causes cancelation, and is there anything I can do to help stop it and still stay in SS 1-2 NW.
and is the resonant frequency teh best freq to cut down on cancellation??
Sorry so many questions, but kinda confused Kevon
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Clarion Pro audio DRZ715 JL 6.5 components crossfire 602 for components 2 12inch Audiomobile MASS subs 5 CU FT box 106 sq inches of port tuned to 51 HZ 2 Cadence A7HC's 2 optima red tops 160 amp Ohio Gen. Alt. 1/0 all the way around.
posted
Cancellation comes from the sound having more than one path. Say at some freq the wavelength is 10ft. Now say you have a speaker producing that frequency and there is two paths to your ear. One is 10ft long, the other is 5ft long. the sound taking the 5ft path will be 180degress out of phase with the sound taking the 10ft path. The end result is the sound cancles itself out. You can demonstrate this very easy. Just take two speakers (subs) and play one frequency. wire one backwords and the other one regular. Now they will produce sound 180degress out of phase with eachother. watch how much the subs move, and how little sound they produce.
------------------ 2-DD 9512's 2-2000X's (for now) 8.0ft^3 box in a civic trunk One big ass port ?????dB's
It's not the size of your woofer, It's the size of the waves your woofer makes!
Posts: 1259 | From: Fullerton. CA ,USA | Registered: Oct 1999
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posted
I get it it. So possibly what I'm experiancing is not cancellation.
So now what?
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Clarion Pro audio DRZ715 JL 6.5 components crossfire 602 for components 2 12inch Audiomobile MASS subs 5 CU FT box 106 sq inches of port tuned to 58 HZ 2 Cadence A7HC's 2 optima red tops 160 amp Ohio Gen. Alt. 1/0 all the way around.
So your subs and your ports are facing towards the back of the seats? Personally, I would port it up through the rear deck. Try messing with the tuning frequency, perhaps put some damping material in the doors. I think those are the two simplest things you can do without making some magor changes.
Adam
------------------ 4 DD9915s, a shredder for each... perhaps when I win the lottery?
posted
Actually I have no rear seats anymore. The box and subs are in the cabin facing the rear. (where the seat was) The trunk is sealed off. ie. subs firing against a solid wall. I'm still trying to figure out why its louder with the windows down. Is it cancellation? I wouldn't think so after reading about it, but who knows?
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Clarion Pro audio DRZ715 JL 6.5 components crossfire 602 for components 2 12inch Audiomobile MASS subs 5 CU FT box 106 sq inches of port tuned to 58 HZ 2 Cadence A7HC's 2 optima red tops 160 amp Ohio Gen. Alt. 1/0 all the way around.
Most systems are louder with the doors open or windows down.
Its hard to say exaclty what it is. Im sure its more than one thing. the air is a lot stiffer as the subs see it with the windows up. that is one major difference. Another difference is the transfer function of the car changes.So your peak could change. I dont know anything about your subs, but when I went to DD's I stoped gaining anything when the windows are down. some subs can just handle being loaded down better than others.
------------------ 2-DD 9512's 2-2000X's (for now) 8.0ft^3 box in a civic trunk One big ass port ?????dB's
It's not the size of your woofer, It's the size of the waves your woofer makes!
Posts: 1259 | From: Fullerton. CA ,USA | Registered: Oct 1999
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posted
Some subs have trouble fully compressing the air in the cabin when the windows are down, so they don't really reach their full potential. Roll down the windows and they can do a better job much of the time, despite pressure loss through the windows.
Adam
------------------ 4 DD9915s, a shredder for each... perhaps when I win the lottery?
posted
I get it. So possibly I could give them more. I notice that with the door open I can't turn it up as loud, so maybe I'll try an extra notch or two. To see if they can take it.
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Clarion Pro audio DRZ715 JL 6.5 components crossfire 602 for components 2 12inch Audiomobile MASS subs 5 CU FT box 106 sq inches of port tuned to 58 HZ 2 Cadence A7HC's 2 optima red tops 160 amp Ohio Gen. Alt. 1/0 all the way around.
posted
I seriously doubt the validity of any argument here. As for opening a window. Think of an open window as a port in a bandpass box. Do you think opening a window is gonna make the sub louder due to pressure when it's stuck in a tiny sealed box.
As for cancellation. Yes, cancellation is when waves are out of phase. Just beacuse one wave travels a different distance(whether it be half or whatever) doesn't mean they'll be out of phase, wavelength(dependant upon frequency and medium) is critical in finding nodes.
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Posts: 768 | From: Ottawa, On, Canada | Registered: May 2000
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Just beacuse one wave travels a different distance(whether it be half or whatever) doesn't mean they'll be out of phase,
If there are two paths from a source to point A, and there is half a wavelength difference between the two paths. when the waves reach point A cancellation will occur.
quote:Originally posted by emu: wavelength(dependant upon frequency and medium) is critical in finding nodes.
Nodes Move
------------------ 2-DD 9512's 2-2000X's (for now) 8.0ft^3 box in a civic trunk One big ass port ?????dB's
It's not the size of your woofer, It's the size of the waves your woofer makes!
Posts: 1259 | From: Fullerton. CA ,USA | Registered: Oct 1999
| IP: Logged |
posted
Higher frequencies do play louder when a window or door is open. Lower freq's will play LOUDER when the vehicle is sealed. Want proof? Take a sub in a box, place it in a large plywood box about 4x8 in size, with one side hinged. Next, place an SPL mic connected to a meter in the box, play a 25hz tone (or whatever you want, say, lower than 60hz) with the "Door" open, and record the SPL. Next, close the "door" and record that reading. You will see a higher number with the door CLOSED as opposed to open. Now, do the same with a higher tone and see what happens. It's physics at work.
------------------ Ron Hawkins
Sometimes the majority only means that all the fools are on the same side.
Everyday I beat my own previous record for number of consecutive days I've stayed alive
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