|15th October 2018, 04:29 PM||#211|
Join Date: Mar 2009
Again a long story, I did some analysis of the DI of both midrange and tweeter in the Monkey Box, both drivers without waveguide.
At first the comparison the DI of both drivers on infinite baffle and in the Monkey cabinet.
In the plots the most smooth DI is on infinite baffle.
DI midrange in cabinet and on infinite baffle.JPG
DI tweeter in cabinet and on infinite baffle.JPG
For the midrange the DI in the cabinet is mapping on the infinite baffle DI (= no impact of cabinet) down to 1kHz and below 1 kHz the DI in the cabinet becomes higher due to the bafflestep of the cabinet. Applying a waveguide to it (like with the Volt VM752), probably the irregularity around 1.8 kHz will become better, and the DI will become a little higher above 1kHz. But the bafflestep boost below 1 kHz will not be changed by a waveguide.
For the tweeter the DI in the cabinet is mapping on the infinite baffle DI down to 3kHz. Below 3 kHz the DI in the cabinet has a dip at 2.5 kHz. This dip is related to the tweeter distance from the top of the cabinet, which is now 9 cm. Below 1 kHz the DI becomes higher also due to the bafflestep, just like the midrange. Applying a waveguide to the tweeter, probably the dip around 2.5 kHz will disappear. The bafflestep boost below 1 kHz also will not change. Above 3 kHz the DI will become higher.
By increasing the tweeter distance from top to 15 cm, the DI dip appears at a lower frequency, see in the plot below. Maybe a better match with the midrange can be obtained for a more flat combined DI with X-over.
tweeter 15 cm from top
DI tweeter in cabinet 15 cm from top and on infinite baffle.JPG
Looking to the combined DI with LR4 filter at 2500 Hz without waveguides.
DI combined LR4 2500 Hz.JPG
Adding a waveguide to the tweeter the dip at 2500Hz will be better. The dip around 1 kHz, I am afraid it will not disappear by a midrange waveguide like implemented in the Volt VM752, we have to check that with measurements on the Volt driver.
Applying the tweeter waveguide will increase the DI above a few kHz and decreasing the global power of the tweeter. I am afraid that maybe that power loss is not so good in combination with a 3 inch midrange. In combination with a larger midrange, it is different, now I have some doubts about the tweeter waveguide. I think we can evaluate that with IEC tests and simulating the global power of the design.
|15th October 2018, 05:20 PM||#212|
Join Date: Mar 2005
Location: Zurich, Switzerland
Paul... This good stuff!
I guess we will have to see what the measurements say. In particular I believe the VM752 starts beaming quite a bit earlier than what Leap predicts for a conventional 3" driver. My goal would be to match the tweeter dispersion to that of the mid at xover, and have smooth dispersion above that.
|16th October 2018, 06:19 AM||#213|
Join Date: Sep 2009
Location: Grua, ten minute walk from 60.258792, 10.664731
Looking forward to impressions of build quality on the drivers involved, as well as the results from measurements.
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