Constant directivity 2-way à la Geddes

[q3cpma]

>personal crossover software and waveguided loudspeaker
Now you only need to make your own drivers, amplifiers and room correction software!

 

[ctrl]

are there any realistic 'driver based' cardioid designs that doesn't involve a dipole and an omni-directional speaker?

It depends on your own expectations and how far down you want the "cardioid-like" frequency range to go.

If, for example, the control of the radiation pattern is desired only down to 400-500Hz, then this can be realized directly via the cabinet shape.

 

[Zvu]

....Note that the real mid-band sensitivity is more like 96-97dB/2.83V@1m. Eminence computes the average over the "usable frequency range", so in this case the Deltalite's rising response inflates the figure.

Make that 2Pi sensitivity. After baffle step correction what you are left with is about 92dB. Not saying that this is lousy, very few loudspeakers are true 92dB at 1W and 1m distance.

I achieved great results with 2512 in 120 liter ported enclosure with DE250-8 compression driver.

 

[Jim Matthews]

.
(Re: Deltalite 2512)

It requires a little massaging above 800Hz, but this is easy to do with DSP. If using a passive crossover a different driver may be a better choice. Note that the real mid-band sensitivity is more like 96-97dB/2.83V@1m. Eminence computes the average over the "usable frequency range", so in this case the Deltalite's rising response inflates the figure.

It's $150 per each in the USA. What midbass driver would you suggest in its place?

Crossed over at 12 dB/octave 1500 hZ it sounds fine. I had mine in a tapered 1/4 wave (TQWT) cabinet because they're easy to make.
Perhaps that augmented the low end response.

It still needed a sub.

When decommissioned, I could still reuse most of the plywood.

 

[bmc0]

>personal crossover software and waveguided loudspeaker
Now you only need to make your own drivers, amplifiers and room correction software!

I haven't made any raw drivers, but I do (manual) room correction with my DSP software, which has full parametric EQ and FIR capabilities. I also designed and built a 4-channel poweramp to use with these speakers (see attached pictures). It uses the LM3886 chip, but is a bit different than most chip amps in that it has balanced inputs. The LM3886 is configured as a difference amp with NE5532 input buffers (basic instrumentation amp topology). Full KiCad design files, including gerbers are available here.

Make that 2Pi sensitivity.

Yes, half space (2pi) is how drive unit sensitivity is usually specified.

What midbass driver would you suggest in its place?

I don't know for sure since I haven't seen many good 3rd-party measurements of drivers of this type. One of the Kapplites may be slightly better. B&C has some good offerings too, but they tend to be a bit expensive (in the US, at least).

Here's a raw ground-plane measurement I did of the Deltalite in-box (1/48 oct smoothing):

 

[Jim Matthews]

I haven't made any raw drivers, but I do (manual) room correction with my DSP software, which has full parametric EQ and FIR capabilities. I also designed and built a 4-channel poweramp to use with these speakers (see attached pictures). It uses the LM3886 chip, but is a bit different than most chip amps in that it has balanced inputs.

Very tidy amp.