I was experimenting with a 6th order bandpass system, when using those chambers sizes,
chamber 1 : 2cuFt fB: 19hz
chamber 2 : 0.2 cuFt fB: 500hz
Using a Max pentivent pv-1030 10" driver
I got the same results in phase response and impedance responce when using the same driver in a vented box
the only thing is a spike at 500 hz with the bandpass, but the woofer will have a 100 hz LP filter so im avoiding that.
Even the f3's are about the same, the bandpass one is 1 hz lower at -3dB
The only different thing between the vented design and the bandpass one is.. about 6db more at 2.83 volts, about everywhere.
and 6 dB is alot..... that makes it 102 dB at 27 hz, the vented box is 95.8 dB at same frequency.
I was curious about 2 things, is it ok to use a so high second chamber tuning fB?
and is it ok to use such a small second chamber size?
chamber 1 : 2cuFt fB: 19hz
chamber 2 : 0.2 cuFt fB: 500hz
Using a Max pentivent pv-1030 10" driver
I got the same results in phase response and impedance responce when using the same driver in a vented box
the only thing is a spike at 500 hz with the bandpass, but the woofer will have a 100 hz LP filter so im avoiding that.
Even the f3's are about the same, the bandpass one is 1 hz lower at -3dB
The only different thing between the vented design and the bandpass one is.. about 6db more at 2.83 volts, about everywhere.
and 6 dB is alot..... that makes it 102 dB at 27 hz, the vented box is 95.8 dB at same frequency.
I was curious about 2 things, is it ok to use a so high second chamber tuning fB?
and is it ok to use such a small second chamber size?
I tried that woofer in WinISD and got very similar results for each enclosure.
Isn't this the woofer that different programs gave you different readings for SPL? One program gave you 6 dB higher than another, even though both were modeling identical boxes.
Something is incomplete about these numbers, they don't add up. Programs take some numbers and compute others from those according to a formula. I think these numbers are contradictory. I think that is what the programs are reacting to.
Maybe your program, having problems dealing with contradictory numbers, simply "flipped" SPL ratings from one enclosure to another.
At any rate, here is what WinISD gives for the 6 th order bandpass and a vented box, 2 cubic feet, tuned to 19 Hz.
The 6th order bandpass is in red.
The vented box is in blue.
Isn't this the woofer that different programs gave you different readings for SPL? One program gave you 6 dB higher than another, even though both were modeling identical boxes.
Something is incomplete about these numbers, they don't add up. Programs take some numbers and compute others from those according to a formula. I think these numbers are contradictory. I think that is what the programs are reacting to.
Maybe your program, having problems dealing with contradictory numbers, simply "flipped" SPL ratings from one enclosure to another.
At any rate, here is what WinISD gives for the 6 th order bandpass and a vented box, 2 cubic feet, tuned to 19 Hz.
The 6th order bandpass is in red.
The vented box is in blue.
Attachments
WinISD has one nifty feature that can make life easy for you, or work against you. That is the feature where by clicking on the measurement, you can change from liters to cubic feet, from centimeters to inches, etc.
When you input your numbers for the driver, be certain that you use the right units. I think I might have added the 8 ohms for Z.
I decided to model the 8 ohms version-same numbers as the 4 ohms.
Below is a shot of the numbers I filled in.
Oops! I didn't get the whole box. Oh well, the section where the numbers are put in is all there on the screen.
When you input your numbers for the driver, be certain that you use the right units. I think I might have added the 8 ohms for Z.
I decided to model the 8 ohms version-same numbers as the 4 ohms.
Below is a shot of the numbers I filled in.
Oops! I didn't get the whole box. Oh well, the section where the numbers are put in is all there on the screen.
Attachments
Anybody who wants to join this discussion should get some background on obtaining Ilianh's difficulties getting SPL ratings for this woofer in this thread:
http://www.diyaudio.com/forums/showthread.php?threadid=9805&highlight=pentivent
And for the specs, just go here and then click on "Max Pentivent Specs". The 1030 is the speaker in question.
http://www.maxspeakers.net/products/pentivent/
http://www.diyaudio.com/forums/showthread.php?threadid=9805&highlight=pentivent
And for the specs, just go here and then click on "Max Pentivent Specs". The 1030 is the speaker in question.
http://www.maxspeakers.net/products/pentivent/
You might have to use a Passive Radiator to tune the 0.2 cu ft box. Pioneer sold a really cheap passive radiator-like under $10-that was just a round piece of foam with a surround. You can cut a round piece of foam yourself, if you just want to experiment, and place a loosely attached piece of Saran wrap as a suround.
I've done it. Looks like hell, but it functions.
Make sure it is Saran Wrap, not any other brand of plastic wrap. Saran, and only Saran, is PVC-you can use vinyl glues on it and it will work fine. Poly wrap-most every brand except Saran-is essentially ungluable.
If it tunes out nicely, you can send away for speaker surround kits and attach the foam more professionally. If it doesn't work out right, then you saved the $20 for a speaker surround kit.
I've done it. Looks like hell, but it functions.
Make sure it is Saran Wrap, not any other brand of plastic wrap. Saran, and only Saran, is PVC-you can use vinyl glues on it and it will work fine. Poly wrap-most every brand except Saran-is essentially ungluable.
If it tunes out nicely, you can send away for speaker surround kits and attach the foam more professionally. If it doesn't work out right, then you saved the $20 for a speaker surround kit.
Well, the tuning at 500hz aint THAT important, i get same results with anywhere from 150 hz to infinity, so i have place for error..
I was thinking doing all this into a sonotube.
for less that 10$ for the completed project.. (ehe, im cheap)
a sonotube is 5$ and i got the mdf needed, and ports....
and as i know myself, I'll do the project to work with a active subwoofer amp with mixers/phase inverters/active filters/gain and the main amp that I made.
then see how if it works... and dissasemble it all... to try to make something else out of those things.
I rarely do a project that I intend in keeping.
so esthetics aint that important..
Theres only one thing I'm worried about, the group delay and phase plot show me differet stuff in winisd than in the pro alpha, and i dont think that what i see as a group delay or phase plot is too good. Vented looks a bit better/smoother.
Thanks for the help
I was thinking doing all this into a sonotube.
for less that 10$ for the completed project.. (ehe, im cheap)
a sonotube is 5$ and i got the mdf needed, and ports....
and as i know myself, I'll do the project to work with a active subwoofer amp with mixers/phase inverters/active filters/gain and the main amp that I made.
then see how if it works... and dissasemble it all... to try to make something else out of those things.
I rarely do a project that I intend in keeping.
so esthetics aint that important..
Theres only one thing I'm worried about, the group delay and phase plot show me differet stuff in winisd than in the pro alpha, and i dont think that what i see as a group delay or phase plot is too good. Vented looks a bit better/smoother.
Thanks for the help
Well, a Sonotube would be made to order for something like this.
I just asked about the vent because I plugged some vent lengths into WinISD to tune a .2 cu ft box and got nothing. Thought maybe it was undoable. Hence, the PR talk. But .2 cu ft with 150 Hz is definitely doable.
I wouod say the higher the frequency you can tune it, the better. The crossover will have an easier time eliminating the peak the higher it is.
By the way, I located a spreadsheet for % efficiency to SPL conversion. Your specs say that the Max Pentivent is 0.4% efficient, but gives no SPL rating. According to John Murphy, a physicist and writer on audio topics, that corresponds to an SPL rating of 88.1 @ 1W/1M. Here is the link:
http://www.trueaudio.com/basslist.htm
Just click on the SPL-% Spreadsheet link.
Sounds a little simplistic to me, but I'll let some of this forum's engineers tell me if they agree. If they say it is good, I will post the list in it's own thread.
Remember, the rating is for one watt. So if you have a 4 ohm driver, sending 2.83 Volts to it-the normal voltage level speakers are tested on-will give the 4 ohm speaker 2 watts, not one. This will result in an SPL 3 dB higher than the 1 Watt rating.
Speakers are normally tested at 2.83Volts because that is one watt for an 8 ohm speaker.
I just asked about the vent because I plugged some vent lengths into WinISD to tune a .2 cu ft box and got nothing. Thought maybe it was undoable. Hence, the PR talk. But .2 cu ft with 150 Hz is definitely doable.
I wouod say the higher the frequency you can tune it, the better. The crossover will have an easier time eliminating the peak the higher it is.
By the way, I located a spreadsheet for % efficiency to SPL conversion. Your specs say that the Max Pentivent is 0.4% efficient, but gives no SPL rating. According to John Murphy, a physicist and writer on audio topics, that corresponds to an SPL rating of 88.1 @ 1W/1M. Here is the link:
http://www.trueaudio.com/basslist.htm
Just click on the SPL-% Spreadsheet link.
Sounds a little simplistic to me, but I'll let some of this forum's engineers tell me if they agree. If they say it is good, I will post the list in it's own thread.
Remember, the rating is for one watt. So if you have a 4 ohm driver, sending 2.83 Volts to it-the normal voltage level speakers are tested on-will give the 4 ohm speaker 2 watts, not one. This will result in an SPL 3 dB higher than the 1 Watt rating.
Speakers are normally tested at 2.83Volts because that is one watt for an 8 ohm speaker.
Ilianh said:
No, acording to the chart, the woofer is 88.1 @ 1W/1M, which is perfectly average.
However, if you use the 4 ohm version, when manufactuers test the speaker, they run 2.83 Vots through it. If you run 2.83 Volts through the 4 ohm version of this speaker, you will get 91.1 dB. That is because you will be running two watts, not one watt, through it.
These numbers are calculated through Thiele-Small parameters. Assuming the parameters are reasonably accurate, this is what it is supposed to be. Little tricks of measurement do not enter into the picture at all.
I'll be honest, I have some doubts about this chart. I'll Email some engineer members to check to make sure that it really is this easy. I saw a couple of long, long equations once with a lot of parameters as variables, so I figured this thing is complicated. But if the chart is indeed accurate, then that is your SPL number.
yhea... still didnt calibrate evrything.. but i'll work on that.
one thing im worried about is the room, I cant measure evrything outside... its cold out there
and i got no laptop...
I dont have an anechoic (spelled right?) room :\
thx for all the help
I start college monday (around 40 hours classes / week) i wont have much time to work on stuff... so im trying to use this last week end to test stuff for experience
one thing im worried about is the room, I cant measure evrything outside... its cold out there
and i got no laptop...I dont have an anechoic (spelled right?) room :\
thx for all the help
I start college monday (around 40 hours classes / week)
i wont have much time to work on stuff... so im trying to use this last week end to test stuff for experienceAdire Audio has this paper on their tech site for calculating SPL using Fs, Vas, and Qes.
SPL Calculation
Pete
SPL Calculation
Pete
Thanks, Pete, for that page and the general info!
However beneficial Pete's information will be to us in the long run, it definitely throws a monkey wrench into the calculations for this particular woofer.
Fs = 19
Vas = 130 L
Qes = 0.37
Max Pentivent claims a reference efficiency of .4%. Kelticwizard, (who will never[/] be confused with Mathwizard), calculates the reference efficiency as .23%. Unless I made a mistake, we are in trouble already.
Converting .23% to SPL yields the number 85.6 dB @ 1W/1M. Pretty much the number Ilianh specified as being "not too good". Oh well.
The contradictions in the chart supplying the Thiele-Small parameters would indicate that this woofer needs measuring by the owner with Speaker Workshop. I myself haven't learned how to use that program, but Ilianh has.
They say it is a good idea to break in the woofer before measuring.
However beneficial Pete's information will be to us in the long run, it definitely throws a monkey wrench into the calculations for this particular woofer.
Fs = 19
Vas = 130 L
Qes = 0.37
Max Pentivent claims a reference efficiency of .4%. Kelticwizard, (who will never[/] be confused with Mathwizard), calculates the reference efficiency as .23%. Unless I made a mistake, we are in trouble already.
Converting .23% to SPL yields the number 85.6 dB @ 1W/1M. Pretty much the number Ilianh specified as being "not too good". Oh well.
The contradictions in the chart supplying the Thiele-Small parameters would indicate that this woofer needs measuring by the owner with Speaker Workshop. I myself haven't learned how to use that program, but Ilianh has.
They say it is a good idea to break in the woofer before measuring.
I came to that same conclusion, 0.23% (isnt too good...)
yhea, I'll measure the woofer, and I'll post the specs.
That Max company has some better series, I should check em out one day, the professional series has some stuff thats worth having a look at, but they have a "comming soon.." on their web page.
Anyway.. Thanks to you all for the great help
yhea, I'll measure the woofer, and I'll post the specs.
That Max company has some better series, I should check em out one day, the professional series has some stuff thats worth having a look at, but they have a "comming soon.." on their web page.
Anyway.. Thanks to you all for the great help
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