I have not listened to them , and are afraid to enquire about the price,
but my efforts to reverse engineer an affordable DIY version has brought me to the pi site (here to stay!)

Anyway despite my divergence from the original plan, ( I will probably build a pi 8) I am curious about the designers using the TAD TD4001 sans horn flare.

Has any pi constructors tried this?
Is this common or uncommon practice?
Does this practice only apply to the TAD TD4001?

Opinions welcome.

http://www.deepaudio.net/html/product_info.htm

Other interesting construction details include aluminium / MDF sandwhich panels with minimum bracing or damping.

Has anybody experimented with laminated / composite sandwich panels?

Cheers,
Paul.

• http://www.deepaudio.net/html/product_info.htm

As for models of π Speakers, there are three basic types.

The one π and two π speakers have a direct radiating cone woofer and dome tweeter. The tweeter is designed with a wide surround and is capable of relatively high excursion, making a first-order crossover possible. The woofer becomes increasingly directional as frequency goes up, but the crossover range is very wide because of the use of a first-order crossover. So there isn't an abrupt change in directionality due to the fact that the woofer and tweeter share a wide common band.

Three π and four π loudspeakers use DI matching between the cone woofer and horn loaded tweeter. Crossover is done where the woofer directionality narrows to match that of the horn tweeter. This prevents a sudden change in in directionality because the woofer and tweeter are about the same at the crossover point.

The five, six and seven π loudspeakers use the room's corner to confine woofer radiation to the 90° wall angle. This is matched by the midrange and tweeter directionality, since both also use 90° flares.

You might want to ask them what they've done to address these issues in their application. Maybe they did some excursion measurements during R&D and found the limits of a TAD 4001 when used without a horn. It would be interesting to know what frequency and power causes the diaphragm to move too far in that application, and whether the coil moves out of the gap, the surround fails or the diaphragm hits the phase plug when the excursion limit is exceeded. You sure don't want to shatter one of those beryllium diaphragms.

The Deep Audio loudspeaker has some things in common with one π and two π speakers, and other things in common with three π and four π speakers. I imagine it sounds good, but I am concerned about their choice to omit the horn. I cannot help wonder about it, and can only assume they have derated the device appropriately and made it work for them in that fashion as a dome tweeter.

At its simplest level, a horn is a way of pointing the sound. Instead of wasting energy sending sound out to the sides and the rear, a horn directs sound into the room, where it is needed. This not only helps focus the sound making it more powerful on-axis, but it also reduces reflections. If directionality is matched throughout the audio band, then the reverberent field is made uniform too. So really, using a horn to point the sound where it is wanted is a good application of a very simple and useful acoustic device.

Basically what I'm saying is that I can't see any reason to forego the use of a horn on a compression driver. High frequency horns are simple and effective acoustic devices, they aren't terribly large and they have no downside I can see. To omit the horn is to use the compression driver in a mode it wasn't designed for, and throws away the advantage of controlled directivity. It also requires increased excursion from a device that was intended for limited excursion.

Just my 2 cents worth!

Ron

They have also voiced the cross-over for the speaker be used only with a direct on axis listening position, so that's what they like as well.

Wayne, I appreciate your explanation, my curiosity has been satisfied for now.
Thanks,

Paul.

Regards,

Greg Jensen

• Basshorn or Transmission Line

On the other hand, measurements of appropriately sized horns show no response ripples, provided the frequency is high enough that the horn is of wavelength dimensions. For the TAD4001, a large horn is not required to avoid pipe modes because of the frequencies involved.