I have built some MLTLs based on the Martin King's MLTL project 4 http://www.quarter-wave.com/Project04/Project04.html to listen to my Lowther PM6A's to run them in as part of my learning. I did not build the correction circuits that Martin designed so they are just plugged straight into the amp.
I've taken some (uncontrolled) measurements at the port and driver to look at responses and by all accounts the response looks good.
By all physical outward appearances they look the same however when I measure the output at the port the SPL is very similar put the phase is quite different as shown in the second attachment. I'm not sure how much this would affect the listening based on the actual measurements at 3m in the room (last Pic) The measurements were made using a calibrated UMIK-1 microphone with REW.
Essentially I'm just playing around to understand the tools and speaker responses etc so not sure if the measurements 'mean' anything but I am just comparing the two speakers, placed in the same place in the room one after the other in the same nearfield manner - i.e. very close to the baffle at the port and the driver. The stuffing in the speakers was measured out according to the plans - however may have moved a bit.
In attachement 3 you can see the top lines are the measurements at the driver and the bottom 2 at the port - and the SPL looks very similar (the speakers probably only have 20 hours on them at the moment)
If I look at the phase measured at the driver for both drivers (attachment 4 and 5) it looks similar to approx 500 hz
When I sum the driver and port values for the left it looks fine (attachment 6) however the Right (attachment 7) has a significant drop at around 90 Hz which from basic Physics 100 wave theory I thought could be because they are out of phase and cancelling each other which is why I looked into the phase.
Measured at 3m away - no room correction (or taking into account room gain etc) probably with reflections everywhere but trying to measure under the same situation with microphone and speakers in the same place - the response looks very similar.
Can someone please help me understand what is happening here - is it something to do with the stuffing, the drivers? I may yet when I have some time swap the drivers to the different enclosures to see if that could be impacting anything.
anyway back to listening
Thanks,
Todd
I've taken some (uncontrolled) measurements at the port and driver to look at responses and by all accounts the response looks good.
By all physical outward appearances they look the same however when I measure the output at the port the SPL is very similar put the phase is quite different as shown in the second attachment. I'm not sure how much this would affect the listening based on the actual measurements at 3m in the room (last Pic) The measurements were made using a calibrated UMIK-1 microphone with REW.
Essentially I'm just playing around to understand the tools and speaker responses etc so not sure if the measurements 'mean' anything but I am just comparing the two speakers, placed in the same place in the room one after the other in the same nearfield manner - i.e. very close to the baffle at the port and the driver. The stuffing in the speakers was measured out according to the plans - however may have moved a bit.
In attachement 3 you can see the top lines are the measurements at the driver and the bottom 2 at the port - and the SPL looks very similar (the speakers probably only have 20 hours on them at the moment)
If I look at the phase measured at the driver for both drivers (attachment 4 and 5) it looks similar to approx 500 hz
When I sum the driver and port values for the left it looks fine (attachment 6) however the Right (attachment 7) has a significant drop at around 90 Hz which from basic Physics 100 wave theory I thought could be because they are out of phase and cancelling each other which is why I looked into the phase.
Measured at 3m away - no room correction (or taking into account room gain etc) probably with reflections everywhere but trying to measure under the same situation with microphone and speakers in the same place - the response looks very similar.
Can someone please help me understand what is happening here - is it something to do with the stuffing, the drivers? I may yet when I have some time swap the drivers to the different enclosures to see if that could be impacting anything.
anyway back to listening
Thanks,
Todd
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