posted
What is the average burp lenght and what time works best for db drag? What is about right 1 to 3 second? What is the maxium time per burp? Do u need to adjusted burp length for different freq? What is everybody opions on importance of quick burps?
Thanks, Brian
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This is definately a good question.. So long as the burp lasts long enough to include enough wavelength percentage to reach the microphone, I suppose the rest (energy lost into the cabin, amplifier reserve exhaustion, transistor heat, etc) is splitting hairs.
Hmm.. Dank- Here is a question. When a soundwave's source ceases motion, the wave loses energy proportional to how much force it exerts on the medium and its boundaries, right?
So, does a soundwave, being non-self-propagating, lose more energy into the surroundings when the source is immediately stopped, when the source continues, or is there no difference?
ShadowStar
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Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
Heres my take on things, I have not tested anything related to this question. hmmm. But I would have to guess 1-2 sec is good for any system to make a good reading before the impedence rises from heat. Also the surface charge of the batteries is long gone after 2 seconds of burping. Most woofers out there in the lanes that are pushed BEYOND their limits are destroyed in the first three seconds, usually mechanical problems.
Hmm.. Dank- Here is a question. When a soundwave's source ceases motion, the wave loses energy proportional to how much force it exerts on the medium and its boundaries, right?
So, does a soundwave, being non-self-propagating, lose more energy into the surroundings when the source is immediately stopped, when the source continues, or is there no difference?
ShadowStar
I don’t think you can think of a soundwave as a wave. You have to think of the whole system. You have a mass oscillating in the shape of a diaphragm in a chamber, separated by a baffle. When the mass stops oscillating the pressure stops oscillating or at least comes to a stop quickly. My guess is that the energy lost into the surroundings is largely a function of the amplitude of the pressure oscillations but not necessarily linear with respect to amplitude. There are certain requirements for an oscillation to take place, (mass spring combo, LC circuit, ect..) all of which can be modeled by the same math equation. Air by itself does not have these properties to sustain an oscillation once started. So to answer your question, if the source stops quickly, the energy lost in the surroundings should decrease quickly.
------------------ 2-DD 9512's 2-2000X's (for now) 8.0ft^3 box in a civic trunk One big ass port ?????dB's
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Posts: 1259 | From: Fullerton. CA ,USA | Registered: Oct 1999
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posted
As far as I have learned it depends on sampling rate of meter. Average sampling times varies somewhere from 0.1 - 0.5 sec. SPL meters for competition are set so they stay at highest number from readings, but they are recording in average time intervals. I don't know how is that on TP meter, on Linar X you can change that, but I can look for data of Audiocontrol if you like.
So lets take worst example 0.5 sec: at 0.0 meter starts to work, at 0.25 you start your system, but meter shows average of 1/2 time not playing and 1/2 playing, from 0.5 to 1.0 sec meter shows highest score, from that time on you are probably loosing score because your batteries are draining, coils are getting hotter... But meter will stay at highest score.
So I think, that 1-2 sec can be enough time. Everything else is just waist of energy and possibility to destroy subs.
posted
I have never seen the score go up once it has registered on the meter. Like once you see it register, then switch off??? I think thats very quick.
I have seen it go up on second or third or third burps though.
posted
what if you created a track that made the woofer go through one complete stroke at a time instead of a continous sweep? what about the timing between strokes? hmm, no pun intended.
Posts: 736 | From: Albertville MN USA | Registered: Mar 2000
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posted
no no.... cause a 1hz tone would mean it takes one whole second for the speaker to move out and back in....
Posts: 736 | From: Albertville MN USA | Registered: Mar 2000
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posted
The best way is to use single frequency (if you know your tone). Sweeps are robbing your power. Sweeps are OK if you don't know exactly what frequency to play. If you know your frequency, result will be better than with sweep! And only with bass CD with music is possible to have better result at sec 10 or... but then again bass CDs have too much extra frequencies, that are also draining your power supply.
With test tone is enough to go over two cycles of sampling frequency. I don't see any reason why should be result better after couple of seconds.
posted
Sorry, sweep in freq was not what I meant. I meant instead of using time use the number of cycles and time between those cycles. You could do single or double cycles from whatever your freq is. Just because the speaker only moves once or twice a second doesn't mean that is 1 or 2hz it means that you did not complete the wave cycle for the whole second (which is what I meant by sweep). Maybe doing some timing between the waves could help in building up so they hit the mic at the same time and add to the amplitude rather than possibly causing cancelation. Maybe I am just blowing smoke. Just an idea.
Posts: 736 | From: Albertville MN USA | Registered: Mar 2000
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posted
Shadow, I’m thinking of a car at low frequencies. Echoes are usually higher in frequency, and are in a place where the distances are great. The lowest frequency that echoes that I can think of is thunder, but that’s thunder. In a car the dimensions are so small, there’s no where for the wave to travel. It’s all just one system.
I think this question could get extremely involved with respect to physics before an exact answer could be decided. What I think of is in a car you have a partially sealed, lossy cabin. There is no way an oscillation could continue on its own for more than a few milliseconds which I would think would be mostly due to the cabin walls mass continuing to oscillate and compress/decompress the cabin.
------------------ 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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