Midrange compression driver development

Have you measured the driver without the horn? The TS Parameters indicate an Le of 0.15

In free air you should be able to make it to around -3dB @ 6.1 kHz with a 0 dB starting point @ 1.03 kHz without the need of a Phase Plug. B&C TS Parameters in terms of 1 watt, 1 meter is lower than the advertised specifications once calculated. B&C states 100 dB sensitivity 1 watt, 1 meter whereas, calculation brings forth 94.66 dB @ 1 watt, 1 meter.

Best Regards,

You have obviously spent a lot of time on the initial design and analysis of the phase plug, but then seem to have just given up and slapped it on to the back of a wooden horn, with no consideration as to how they couple.

From the photos, there appears to be a relatively large discontinuity in cross sectional area from the phase plug exit and the throat of the main horn. Such discontinuities are not conducive of a smooth or optimum response.

One of the benefits of using a phase plug is that it reduces the volume of the cavity between the diaphragm and the horn throat. This cavity behaves as an acoustic reactance acting as a shunt capacitance across the throat. However, it may be useful to measure the response of the driver horn combo without a phase plug to get a base line response.

In his 1978 paper on phase plugs, Henricksen noted that circumferential phase plugs produced a notchy response compared to radial slit phase plugs. It might be worth experimenting with that type of design. If I remember correctly EAW used a form of radial slit phase plug to couple cone drive units to mid-range horns in some of their designs.

VECTORDJ wrote: Turbosound wrote an AES Paper that talked about Cone Mid Horns....Speaker Builder Mag had a paper on Cone Mid Horns....Checkout Funktion One designs....As You found getting above 2K flat is Black Magic....Good Luck with Your Project.

Elliot Thompson wrote: Have you measured the driver without the horn?

to me it is clear that i loose a lot of spl in the higher frequencies because of the nearly constant directivity if my horn. The driver alone measures more hf, but its directivity also becomes very narrow, while my horn disperses the sound pressure over a larger radiation angle. That is also the reason for my whole Phaseplug Design. I need more output at the higher frequencies to then disperse it over a greater angle.

snowflake wrote: you aren't trying to get very wide bandwidth out of this - can you not do better just using a front chamber to couple to the horn...

 
No i can't since i would not get the desired directivity with the hornthroat = SD. But by reducing the throat area till its small enough for the directivity and "hf"-SPL, i get problems because of the pathlength differences and throatchamber volume.

fudge22 wrote: You have obviously spent a lot of time on the initial design and analysis of the phase plug, but then seem to have just given up and slapped it on to the back of a wooden horn, with no consideration as to how they couple.

fudge22 wrote: From the photos, there appears to be a relatively large discontinuity in cross sectional area from the phase plug exit and the throat of the main horn. Such discontinuities are not conducive of a smooth or optimum response.

I think the photos are misleading then. The only real discontinuity is the change from a round throat to a square horn. This change is made less drastic by the triangles in the corners. But i also did a measurement without those triangles and even that had no significant effect on the response. 

fudge22 wrote: One of the benefits of using a phase plug is that it reduces the volume of the cavity between the diaphragm and the horn throat. This cavity behaves as an acoustic reactance acting as a shunt capacitance across the throat. However, it may be useful to measure the response of the driver horn combo without a phase plug to get a base line response.

The last measurement of my initial post shows exactly that :)

fudge22 wrote: In his 1978 paper on phase plugs, Henricksen noted that circumferential phase plugs produced a notchy response compared to radial slit phase plugs. It might be worth experimenting with that type of design. If I remember correctly EAW used a form of radial slit phase plug to couple cone drive units to mid-range horns in some of their designs.

madboffin wrote: One thing to check for, as you tidy up the design, is resonances in the component parts of the phase plug i.e. the cone and the ring. They can sometimes cause suckouts and an uneven frequency response. The technical way to do this is with an accelerometer (vibration pickup) but you can do a basic check for any serious resonances by holding a finger on the relevant part while doing a frequency sweep, which will indicate if further investigation is required.

Thanks for the tip! I will try if i can feel anything...but with double ear-protection...this thing is LOUD with even the slightest input :D

RoadRunnersDust wrote: What cone-plug distance have you used?