That would be my thought as well. Who knows what math determines that chart in SoundEasy, it could be wrong for all I know. It's the only software I know of that will plot the cabinet pressure though. One of these days I might connect a pressure sensor to a cabinet and see for myself just to confirm the above graph, I should be able to whip that up with some spare parts from work.
Had to google kPA to get an idea of the pressure. 1 kPa is approximately the pressure exerted by a 10-g mass resting on a 1-cm2 area. Or 1 kPA = 0.145038 PSI.
I believe that SoundEasy plot to be correct. I think there would still be high pressure in the box, but it is increasingly out of phase with the driver cone motion at decreasing frequency.
It is out of phase, the port becomes a hole offering no resistance to the speaker, hence no way for the speaker to create pressure. Like a cylinder with no spark plug in it.
@ugly_woofer said:
I like the steep crossover slopes Bill, nicely done.
Thanks, Nick. I kept the cost down by using Daytons I-core's and NPE's on the woofer branch. It is sounding pretty good so far and the tweeters seems to be able to handle the power when I crank them up into the 90dB+ range. I'll run some 95dB distortion plots and post them later.
Sorry for the delay in collecting and posting this data. I decided to take the Zonkers to SDC and see how they do in the Dayton category. Since I am crossing at 910Hz to a one inch dome tweeter, the judges will most certainly ask me if I have any HD measurements. I was always meaning to run up some HD plots, but then covid hit and I forgot all about it. So here they are. Taken this morning with OmniMic at a distance of 1 meter on tweeter axis at a 95dB playback level.
95dB is a fairly high level for just one speaker at a distance of 1 meter. So, analyzing the crossover regions 2nd and 3rd harmonics, I think I am in good shape. Group delay doubles for an 8th order xover, but I don't think most people can hear group delay.
500Hz 2nd: -47dB or 0.4% 3rd: -47dB or 0.4%
600Hz 2nd: -55dB or 0.15% 3rd: -43dB or 0.7%
700Hz 2nd: -55dB or 0.15% 3rd: -44dB or 0.6%
800Hz 2nd: -62dB or <.1% 3rd: -48dB or 0.4%
900Hz 2nd: -51dB or 0.3% 3rd: -51dB or 0.3%
1kHz 2nd: -50dB or 0.3% 3rd: -60dB or 0.1%
Comments
The same 60L cabinet and driver and 100W power, simply ported vs sealed.
You'd think the pressure below the tuned frequency would drop off as there's no loading below it in the ported box.
That would be my thought as well. Who knows what math determines that chart in SoundEasy, it could be wrong for all I know. It's the only software I know of that will plot the cabinet pressure though. One of these days I might connect a pressure sensor to a cabinet and see for myself just to confirm the above graph, I should be able to whip that up with some spare parts from work.
Had to google kPA to get an idea of the pressure. 1 kPa is approximately the pressure exerted by a 10-g mass resting on a 1-cm2 area. Or 1 kPA = 0.145038 PSI.
I believe that SoundEasy plot to be correct. I think there would still be high pressure in the box, but it is increasingly out of phase with the driver cone motion at decreasing frequency.
It is out of phase, the port becomes a hole offering no resistance to the speaker, hence no way for the speaker to create pressure. Like a cylinder with no spark plug in it.
Sorry for the delay in collecting and posting this data. I decided to take the Zonkers to SDC and see how they do in the Dayton category. Since I am crossing at 910Hz to a one inch dome tweeter, the judges will most certainly ask me if I have any HD measurements. I was always meaning to run up some HD plots, but then covid hit and I forgot all about it. So here they are. Taken this morning with OmniMic at a distance of 1 meter on tweeter axis at a 95dB playback level.
95dB is a fairly high level for just one speaker at a distance of 1 meter. So, analyzing the crossover regions 2nd and 3rd harmonics, I think I am in good shape. Group delay doubles for an 8th order xover, but I don't think most people can hear group delay.
500Hz 2nd: -47dB or 0.4% 3rd: -47dB or 0.4%
600Hz 2nd: -55dB or 0.15% 3rd: -43dB or 0.7%
700Hz 2nd: -55dB or 0.15% 3rd: -44dB or 0.6%
800Hz 2nd: -62dB or <.1% 3rd: -48dB or 0.4%
900Hz 2nd: -51dB or 0.3% 3rd: -51dB or 0.3%
1kHz 2nd: -50dB or 0.3% 3rd: -60dB or 0.1%