Last thing i am curious about is an argument i had with someone about spl, and moving air.
A guy was claiming that sealed, and ported boxes both move the same amount of air.
I was thinking that ported boxes move more, and that the rear wave from the port contributed that more air. Wether the port is playing a tone at the tunning frequency, or a little higher splitting output between the driver, i was thinking that the reason ported boxes produce more spl is because the subwoofer cone and the ports radiation equates to more air being moved. Or if you are playing a tone at tunning you can add alot of power and excite the port more causing more air to be moved?
So this is the last thing i need help with. Does more air displacement give more spl? Or like you said with mutual coupling i guess they work together? But if this is true what exactly creates more SPL, the energy of a wave? Is this the amplitude? i am a little lost with it and i am interested in SPL competition aswell.
A guy was claiming that sealed, and ported boxes both move the same amount of air.
I was thinking that ported boxes move more, and that the rear wave from the port contributed that more air. Wether the port is playing a tone at the tunning frequency, or a little higher splitting output between the driver, i was thinking that the reason ported boxes produce more spl is because the subwoofer cone and the ports radiation equates to more air being moved. Or if you are playing a tone at tunning you can add alot of power and excite the port more causing more air to be moved?
So this is the last thing i need help with. Does more air displacement give more spl? Or like you said with mutual coupling i guess they work together? But if this is true what exactly creates more SPL, the energy of a wave? Is this the amplitude? i am a little lost with it and i am interested in SPL competition aswell.
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Vented.......
Hi Huricaine,
Maybe this link will help, see "phase inverter":
Loudspeakers tutorial | University of Salford
Regards,
Hi Huricaine,
Maybe this link will help, see "phase inverter":
Loudspeakers tutorial | University of Salford
Regards,
Thanks tb46, i already knew that information, but i was just wondering how the constructive addition of the ports output increased spl? I know identical waves will be louder but why is it an increased amplitude like construction in standing waves?(without the rest).
The thing i really want to know is: If why dosn't increasing amplitide change frequency? Isn't it related?
The thing i really want to know is: If why dosn't increasing amplitide change frequency? Isn't it related?
Hi Huricaine,
Amplitude is amount or distance of the back and forth motion, e.g.: moving from peak to peak. Frequency is the rate at which this motion is happening, irregardless of how much the cone moves (how often per second it moves, e.g.: from peak to same peak), as long as it moves. No motion, no frequency, that's about the degree to which those two are related.
Regards,
Amplitude is amount or distance of the back and forth motion, e.g.: moving from peak to peak. Frequency is the rate at which this motion is happening, irregardless of how much the cone moves (how often per second it moves, e.g.: from peak to same peak), as long as it moves. No motion, no frequency, that's about the degree to which those two are related.
Regards,
Hi Huricaine,
"...cone travel distance is related to amplitude..."
Yes, provided there is no interference between front and back radiation. For a given driver, enclosure and environment you'll need more cone travel distance (amplitude) to get more SPL (also amplitude), it is the amount of air displaced that results in the pressure changes.
Regards,
"...cone travel distance is related to amplitude..."
Yes, provided there is no interference between front and back radiation. For a given driver, enclosure and environment you'll need more cone travel distance (amplitude) to get more SPL (also amplitude), it is the amount of air displaced that results in the pressure changes.
Regards,
wow that summedup what i was wondering for a while.
So, at higher frequencies you will have standing waves and the cone dosn't travel as far(i knew for a while already)and i assume that to get high spl for these frequencies you need an efficient driver that can move with more force? Or accerate faster?
For low frequencies in the cabin-gain area i will need displacement for higher amplitude probly because it means that i can move more air at the same frequency than a driver with less potential to displace air.
Okay so with a ported box, a person i was arguing with was claiming that they displace the same air then a sealed box, true? I can see his point because as you get closer to tunning the front of the subwoofer cone does less, so the port proprtionally puts out more... Or can it be that the port is just more efficient and can do more? I remember reading that ports have no displacement limits so i figure the more energy you can create like from power, the more displacement?
So, at higher frequencies you will have standing waves and the cone dosn't travel as far(i knew for a while already)and i assume that to get high spl for these frequencies you need an efficient driver that can move with more force? Or accerate faster?
For low frequencies in the cabin-gain area i will need displacement for higher amplitude probly because it means that i can move more air at the same frequency than a driver with less potential to displace air.
Okay so with a ported box, a person i was arguing with was claiming that they displace the same air then a sealed box, true? I can see his point because as you get closer to tunning the front of the subwoofer cone does less, so the port proprtionally puts out more... Or can it be that the port is just more efficient and can do more? I remember reading that ports have no displacement limits so i figure the more energy you can create like from power, the more displacement?
Hurricane,
Amplitude and frequency are just technical words for "how much" and "how often". When it comes to standing waves people are usually talking about room acoustics rather than the speaker. These standing waves are usually significant at lower and sometimes mid frequencies.
For your ported argument, I would suggest you use one of the simple graphic box size programs. You choose a woofer and put in the basic parameters. Set it to closed then set it to ported. You'll want to compare the cone displacement plot in both, and the frequency response plot will tell you the sound pressure for each and also the bass extension.
Amplitude and frequency are just technical words for "how much" and "how often". When it comes to standing waves people are usually talking about room acoustics rather than the speaker. These standing waves are usually significant at lower and sometimes mid frequencies.
For your ported argument, I would suggest you use one of the simple graphic box size programs. You choose a woofer and put in the basic parameters. Set it to closed then set it to ported. You'll want to compare the cone displacement plot in both, and the frequency response plot will tell you the sound pressure for each and also the bass extension.
Hi Huricane,
Post #27: "...ported box, a person i was arguing with..."
In a ported box you have two sound sources, the driver's cone, and the port opening (another way to think of them would be two drivers in two sealed boxes with independent amplifiers, and some means of altering the phase of one of the amplifier input signals in the same fashion the box and port in a bass reflex enclosure alter the phase of the rear radiation of the BR driver). When the sound coming from both sources is in phase they add (and you get more than from one), when the sound coming from both sources is 180 degrees out of phase they cancel (and you get very little), naturally there are stages in between.
The port and the internal volume of the enclosure form a resonant system, it takes very little input to get this system to resonate, also at that frequency the pressure changes inside the box reduce the motion of the cone to almost nothing, this reduces the driver impedance the amplifier sees at this frequency, and the amplifier can deliver more current to the driver. You would normally think that more power into the driver means more cone motion, but the phase inverter action of the enclosure port combination loads the cone down so much, that this cannot happen; the additional power goes into the air in the enclosure, and is then coupled through the port to the listening environment.
There is a wealth of good information on this subject, and it depends on how deep you want to go to further your understanding. AllenB's advice to try some "...simple graphic box size program..." should be helpful. In Hornresp David McBean gives you an neat way of looking at the different outputs while changing the variables (box size, port area, port length) in the Direct Radiator Loudspeaker Wizard. If you haven't messed with Hornresp yet, do yourself a favor, and give it a try.
Regards,
Post #27: "...ported box, a person i was arguing with..."
In a ported box you have two sound sources, the driver's cone, and the port opening (another way to think of them would be two drivers in two sealed boxes with independent amplifiers, and some means of altering the phase of one of the amplifier input signals in the same fashion the box and port in a bass reflex enclosure alter the phase of the rear radiation of the BR driver). When the sound coming from both sources is in phase they add (and you get more than from one), when the sound coming from both sources is 180 degrees out of phase they cancel (and you get very little), naturally there are stages in between.
The port and the internal volume of the enclosure form a resonant system, it takes very little input to get this system to resonate, also at that frequency the pressure changes inside the box reduce the motion of the cone to almost nothing, this reduces the driver impedance the amplifier sees at this frequency, and the amplifier can deliver more current to the driver. You would normally think that more power into the driver means more cone motion, but the phase inverter action of the enclosure port combination loads the cone down so much, that this cannot happen; the additional power goes into the air in the enclosure, and is then coupled through the port to the listening environment.
There is a wealth of good information on this subject, and it depends on how deep you want to go to further your understanding. AllenB's advice to try some "...simple graphic box size program..." should be helpful. In Hornresp David McBean gives you an neat way of looking at the different outputs while changing the variables (box size, port area, port length) in the Direct Radiator Loudspeaker Wizard. If you haven't messed with Hornresp yet, do yourself a favor, and give it a try.
Regards,
I know exactly What you mean I learned about it months ago. I just wanted to know if you consider a ported box to displace more air then ported? While at tunning you can add alot of power and I figure this goes into greater air displacement? Also when above tunning the port and sub are like 2 I know, so does this possibly mean more displacement?
Like I asked before if amplitude was equal to displacement, and a ported box creates more spl/amplitude then it could be said to displace more air then a sealed box subwoofer that does not produce as much spl?
Like I asked before if amplitude was equal to displacement, and a ported box creates more spl/amplitude then it could be said to displace more air then a sealed box subwoofer that does not produce as much spl?
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