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Multi-Way Conventional loudspeakers with crossovers

Precision Devices 18" for bottom of 3 way?
Precision Devices 18" for bottom of 3 way?
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Old 10th February 2019, 01:37 PM   #11
mortron is offline mortron  Canada
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I wouldn't use it above 300hz. Slopes... 12... 24db... Depends on what sounds best
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Old 10th February 2019, 03:26 PM   #12
Think is offline Think  Netherlands
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Precision Devices 18" for bottom of 3 way?
Good specs for what use? Don't forget that an 18" won't be able to produce much off axis mids, so is IMO limited to bass use. Making a 2 way out of it will be an expensive lesson because it will result in a horrible sounding speaker with a huge off axis mids dip.

Many small subwoofer/bass drivers in separate boxes also sound better then 1 big one due to placement options.
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Old 10th February 2019, 08:30 PM   #13
John Busch is offline John Busch  United States
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Default Heresy I'll tell ya, Heresey!!

Just for fun... You can build a surprisingly competent 18" two way suitable for domestic use using an 18" and dome tweeter. Know eyes are rolling... but it has been done. As a demo - think piece, I designed such a crazy thing for a DIY get together in the S.F. CA area sometime around 2000 or so. I named the thing "The Jokes".

As always, it comes down to good basic engineering. I will admit, the result was far from practical for most users. The major part of this unique contraption was driver choice.

The 18" was a medium Xmax paper cone pro PA driver built for Wright Brothers Sound by Eminence. Happened to have 4 left over from a big pro sound project. It was intended as a high output mid woofer for vocals. Light cone, 2.5" 4 layer voice coil. 80 oz vented magnet. Low QTS. Very low FS (18 - 20 Hz) Cone profiled for max possible dispersion. So it was quite reasonable off axis up to about 750 Hz or so.

Enter a special dome tweeter... the venerable Scan-Speak D3806/820000. This wonderful creation has been in continuous production for over 4 decades!! Not very many drivers can qualify there! 1.5" treated silk dome with a HUGE (SD) motor with a LOT of copper. Can play nicely down to 1,200 Hz assuming a correct 2nd order Butterworth (electrical) 3rd order acoustic crossover.

The D3806 ran flat out. On a larger baffle with a bit of recess it is about 91 dbw. The 18 was in a heavy stuffed 5 cu. ft. sealed box that provided a QTC of about .65. Add a healthy baffle step correction circuit and a 2nd order Butterworth low pass (electrical) at the right frequency and you have a flat output from around 38 Hz up to just over 18Khz. Vocals were wonderful. Imaged quite well. Power response was quite nice. Big and ugly, but did sing. What I remember most about this design was how effortless it was. Kind of like a BIG OB. Know it really surprised a lot of people. OK, I'm done!
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Old 11th February 2019, 11:54 PM   #14
mortron is offline mortron  Canada
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Thanks for the reply John! Those sound awesome. I wish I could hear all the mad creations out there. Especially many of yours.

I am really having trouble trying to decide on how to go with my project. I want to use large drivers in a 3 way, and am not sure how to decide which drivers to use. It's tough.
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