Open baffle 2.5way with .5 speakers angled 90*

[GuyPanico]

My newbie question of the moment...

Would this design be feasable. This is just an idea. It doesn't necessarily meet any design requirements I have.

It would be active and biamped. However, the .5 array would have a passive 1st order xover. Since the mids, and thier .5 friends are 90* apart, would the 1st order xover on the .5's put them into the same phase?

[bjorno]

Hi, Here are some observations that I think can be made based on the UFO array configuration:

The frontal sound-smear will rely on inter driver horizontal c-c distances and the phantoms possible minimum width (if stereo placed) created with this array will be at least as wide as the baffle and totally blurred.

See the correct configuration that minimizes array stereo phantoms:

http://www.diyaudio.com/forums/showt...27#post1209527

Driver (lo to high frequency partitions always < about 1.5 KHz = W-T angle) azimuth angles for minimizing blur depending on the listener head shadowing effect, at the right upper corner of the picture, see:

http://www.diyaudio.com/forums/showt...28#post1209528

The horizontal MAA will be very diffuse and wide for this UFO array but smallest if the outer row has the LP filter connected.

Vertical MAA depends on .5 driver c-c and the crossover frequency that is minimized if crossed over estimated lower than 0.91 x lambda with a very steep filter than can be relaxed to 2:nd order filter if crossed over at 0.91/lambda/2,see:

http://www.diyaudio.com/forums/showt...00#post1215500

The T driver c-c if more than 1.5 “ will place this array in the category: low performer, this because the secondary lobes occurs to early, in my opinion.

For this proposed array it would be also safe to cross over from M to the W drivers at a frequency at 344/(4 x (M-W c-c)) or lower, as this would sharpen up the phantoms at least 50 %.

The driver off axis performance is very important because the front interference is spread 90 degrees apart but the rear is crossed 90 degrees inwards causing the breakpoint to be chosen at a low frequency below about 500 Hz for a system with 4” drivers (both M and W), (if 6” 4” / 6” x 500 <= 333 Hz) and the crossover point to the T driver not over 1500 Hz (for 6” drivers <= 1000 Hz) for this case if the sweet spot should be suitable and include more than one person.

See the picture where the c-c distance and a M-T-M configuration for a column of 8 4” drivers are shown.

Observe: this array shows no tilting but the UFO array would have + or – 15 degree horizontal tilting depending on which driver is the .5 column in the array.

Much more could be said about this odd array, in my opinion, there are more drawbacks with this configuration than advantages for a line array set-up.

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[wigginjs]

Guy:

What software did you use to generate that image?


bjorno:

What software did you use to generate those images?

[bjorno]

Hi mOtion,

Read post # 741 from this thread for an answer:

http://www.diyaudio.com/forums/showt...99#post1209499

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[GuyPanico]

The 4" mids have a vertical c-c of 5", and the tweeters a vertical c-c of 1.4". Crossover point would be at 2700hz (24dB). I'm not sure how to measure horizontal spacing. Should I fallow the baffle, or make a direct line from driver to driver? If I fallow the baffle, mid-to-woofer is 7" or 4.9" respectively. Tweeter-to-mid is about 3.25". Crossover point for the woofer is unknown.

I came up with this shape after playing with the angles of my current U baffle array. I found that if I toe them out signifigantly, the size of the sound increased and bass was improved. However imaging was degraged. With the above baffle, tweeters will still face forward but mids are angled.

Could you explain 'phantoms' a little bit?

m0tion: I used Google Sketchup. Nice free bit of software so long as you dont need tons of features.

[bjorno]

Hi,

I'm not sure how to measure horizontal spacing

I always use the 4.9” distance; this because the most important is from the listening point of view, the minimum sighted c-c distance.

I found that if I toe them out significantly, the size of the sound increased and bass was improved. However imaging was degraded.

Exactly what I suspected too.

Could you explain 'phantoms' a little bit?

Im not sure what you want me to explain, but the Phantoms I refer to is point source Phantoms in the first case, so I ask you again to narrow your question about Phantoms that I think for good arrays outperform most legacy 2 speaker set-ups, (now extending to the more wider and general concept where phantom imaging also is focused).

Read the text in the picture I think will help you to use the same foundation and ‘language’ we can agree upon:

http://www.prosoundweb.com/recording...h2/ch2_1.shtml

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