[James Romeyn]

Concave quad full range array for a satellite speaker above 130 Hz.  Below image portrays four 1” beryllium dome tweeters with central phase plug, James Loudspeaker 75” tall in-wall model 812BE:


Please share any opinions.  I'm considering four 2” (5.8cm) square full-range sealed Balanced Mode Radiators arrayed similar to the tweeters above.  Centered among the four 2” full range drivers is a planar tweeter (H x W: 3.4 x 2.1”) with a special waveguide producing a hemispherical radiation pattern in the horizontal plane.
6 kHz crossover between the 2” BMR and the tweeter. 
   




 

[JLM]

BMR = Jordan flexing aluminum drivers, right?

Like the unity design (waveguide for controlled directivity).

In my ideal world the crossovers would be 80 and 10,000 Hz with a 94 dB/w/m efficiency at 8 ohms.  And the whole thing would cost next to nothing and fit on a dinner plate.

Would you offer subwoofers (swarm) to go with it?

[James Romeyn]

BMR = Jordan flexing aluminum drivers, right?

Like the unity design (waveguide for controlled directivity).

In my ideal world the crossovers would be 80 and 10,000 Hz with a 94 dB/w/m efficiency at 8 ohms.  And the whole thing would cost next to nothing and fit on a dinner plate.

Would you offer subwoofers (swarm) to go with it?

Re. the 2": I can't hear them till Parts Express sells out the first version of HiWave's Balanced Mode Radiator, allowing them to move on to the updated/improved "A" version.  Drop me an email and I'll forward the "A" data sheet.  They're only about $15ea.  FR almost ruler flat (per specs, my friend says the BL and FR look faked/too good to be true) 140-16k Hz.

They are sealed-back.  They look cool and should mount easy.  Stereophile had good reports on even the first version in some production speakers in Europe.  I'm unsure of maximum acoustic output vs. my current single Dynaudio Esotec 170mm 17WLQ.  Four 2" = 89 dB, but I'd use two monitors per channel employing Toole's latest ambiance array theories (images by next week) yielding about 91 dB/channel overall.  (Eight per speaker would get to your 94 dB spec, but requires two of my chosen tweeters and I know of no suitable siting method for 8x 2"/2x tweeters.)   

I prefer to cross subs much higher than the norm (over 100 Hz) to extend the mode-flattening effects (bass mode effects up to 150-200 Hz). 

Definitely yes on the subs!  My thinking: start with distributed array which can cross above 100 Hz, then the ideal 2-way to match.   

[walkern]

Your application of the 2" BMRs may not require the addition of a tweeter or super tweeter, so my first suggestion would be to try it without.  I've listened to the Cambridge Audio BMR based Minx speakers and they have decent extension in the treble.

And I don't know about the upgraded or updated BRM units, but the current models are not sealed behind the driver (even though they look like it in the photos, and one 'designer' on P.E.s website says they are).  I bought 8 of the little buggers to play with, and am going to try a modest OB line with a sub kicking in where ever they roll off (guessing about 120hz to 150hz).  If that doesn't pan out maybe I'll try your arrangement.  Thanks for the idea!

Neil

[James Romeyn]

walkern,
If you have a preferred retail source for the Cambridge Audio Minx in the USA, please forward, email or PM is fine. 

Curious what was the associated gear you heard with the Cambridge Minx.  I'm very glad you mentioned this because I was not sure who used the 2" BMR.  Compared to your expectations, how would you qualify the performance? 

Please keep us posted on your progress.  "A" version a bit smoother than the earlier model.  140-15kHz +0/-4 dB centered @ 4500 Hz!  Mighty impressive!  Dips are more tolerable than bumps in FR curves.  4500 Hz is the perfect place for this soft-edged dip, right where you'd least tolerate a bump.  Regarding the benefit of adding a tweeter...my sub is conservatively rated to 113 dB @ 20 Hz and successfully flattens bass modes.  It's the kind of system that might benefit more than average with high frequency extension up to at least 20 kHz.  The tweeter is small enough (about 3x2") that it will barely increase the 2" spacing more than if the tweeter is omitted.   

The proposed planar tweeter has a 2-piece foam waveguide to approximate a hemispherical radiation patter in the horizontal plane.  So I'm considering direct-coupling both vertical 2" to boost HF dispersion in the vertical plane, where planar tweeters lack.     I really appreciate you mentioning the 2" are open back and not sealed.  IIRC a PX tech said he had it in his hands and it was sealed.     "A" version data sheet:     


Only between 130 Hz-2 kHz, how does maximum acoustic power compare, four 5.8cm square fullrange drivers vs. one Dynaudio 17WLQ 17cm Esotec midbass?  Both drivers are reasonably flat to 2 kHz.  Specs below:       

Le, Inductance, mH   
5.8cm square: 0.137 +/-10%         
17cm round: 0.19 @ 10kHz 

BL, Force factor, Tm
5.8cm square: 3.87
17cm round: 6.0 

Fs, Resonance frequency, Hz
5.8cm square: 148 +/-20%
17cm round: 40 

Drv, Voice coil diameter, mm
5.8cm square: 25.4
17cm round: 75 

Mms, Moving mass, g
5.8cm square: 1.68
17cm round: 15 

Cms, Compliance, mm N-1
5.8cm square: 0.70
17cm round: N/A 

Rms, Suspension Loss, Ns m-1
5.8cm square: 0.49
17cm round: N/A 

Xmax, Maximum coil excursion p-p, mm
5.8cm square: 7.0
17cm round: 17.0 

Sd, Effective piston area, cm-square
5.8cm square: 17.2 (x4 = 69)
17cm round: 120 

VAS, Equivalent volume,  L
5.8cm square: 0.29
17cm round: 22 

Qms, Mechanical quality factor, Qms
5.8 square: 3.18
17cm round: 1.8 

Qes, Electrical quality factor, Qes
5.8cm square: 0.83
17cm round: 0.5 

Qts, Total quality factor, Qts
5.8cm square: 0.66
17cm round: 0.4 

Sens, Sensitivity, dB/W/M
5.8cm square: 83 (x4 = 89)
17cm round: 86 

Continuous power handling, (weighted pink noise),   W
5.8cm square: 12 (TBC)
17cm round: >130 (IEC) 

Burst power handling, (weighted pink noise), W
5.8cm square:    >24 (TBC)
17cm round: >1000 (10ms)