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thin tower speaker design

I am planning to build 2 speakers that are thin tall deep towers looking physically like NHt's 3.3 or 2.5.

The Side facing woofer is a 12" Audio Concepts DV12. The Front drivers are a 6" 18W8546 ScanSpeak and a 1" 9900 ScanSpeak tweeter. Before I start I must warn that my post is long and since I do not have regular email access I would appreciate it if I am emailed at navin@vsnl.com.

I have the following requirements:
1. As high efficiency as possible
2. Use for Home Theater as well as Stereo
3. Resonable Power handling (100-150W rms)

I hope to use the 12" to compensate for the difraction loss of the 18W8546. Difraction loss is a loss (claimed to be 6db) of low frequencies based on the width of the cabinet (in this case 8" or 20cm). This is better described at http://www.trueaudio.com/st_diff1.htm.
Hence to compensate for Difraction loss most 6" 2 way spekaers employ either a 2nd 6" covering only the lower frequencies or reduce the
upper frequencies to make the speaker sound better balanced.

Not having a 2nd 6" I hope to use the output of the 12" but dont know if this make sense as the 12" will be quite some distance from the 1st 6" and the frequencies that are compensated for are from 100-1800Hz. The 12" might not be able to reproduce 1800 Hz accurately and in any case 2 drivers reprducing the midrange but being far apart might create problems (lobing, delay, etc.). Any advise would be welcome.

Also to increase power handling it makes sense to roll of the low frequencies to the 6". Power handling for this driver is not limited by it's thermal limits but by it's physical excursion limits. Hence the saame power being supplied to the 12" and 6" operating in parallel at low frequencies (below 100Hz) can stress the 6" while not even exciting the 12". However to employ a low frequency high pass crossover using passive crossovers is a challenge. Again I welcome any advise on this front.

Lastly given the physical constructon of a 8" wide, 44" high, 30" deep tower will be difraction loss be 4db since the only edges are 2 sides (4" from center of woofer) and the top (10" from center of woofer) or more? I assume this because it commonly held that difraction compensation for a 6" 2 way is about 6db-8db. However 6" 2way monitors
have 3 edges close the the woofer (4" from center of woofer) and a 4th edge about 10" from center of woofer.

So there you have it, can one use a side facing 12" for difraction compensation?, Can one increase th power handling of a 6" using passive crossovers?, and what it the difraction compensation for a 6" on a thin, deep, tower cabinet?.

Regards
Navin


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Topic - thin tower speaker design - Navin 23:19:48 01/02/02 (0)


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