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PostPosted: 06 Aug 2017, 10:00 
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Location: Winnipeg, CANADA
In the photos below is a pair of open baffle speakers that I just recently constructed for the Audio Nirvana Classic 8 fullrange speaker drivers. I'm actually working on a bass reflex box for these Classic 8 speaker drivers and these open baffles panels were constructed using what cutoffs that had remained from the plywood sheet.

Attachment:
Open-Baffle-Plywood-Pieces.jpg

The plywood is 3/4 inch (19 mm) thick multiplex (11 ply) birch. The price is right at $40 (Canadian) per 4' x 8' (1.2 x 2.4 m) sheet (purchased from Rona). The birch plywood is fairly void free, but the outer veneers are paper thin. This birch plywood is not the superior quality of a true Baltic birch plywood, but it is very good value IMO at this cost.

There is nothing fancy going on with the construction of these open baffle speakers. The dimensions were largely predicated by the sizes of the plywood cuttoffs and that they would be sitting on a near 24 inch (600 mm) wide H-Frame open baffle. I'll measure the exact dimensions of the open baffles and post them in a separate photo for those interested. To construct the open baffle speakers, the plywood pieces were simply butted together and glued in place. The glued butt joints will provide more than adequate strength for this open baffle speaker application.

Attachment:
Audio-Nirvana-Classic8-Open-Baffle-Speakers.jpg

The open baffles for the Audio Nirvana Classic 8 drivers will sit atop an H-Frame open baffle housing an 18-inch Goldwood GW-1858 woofer driver. These sturdy H-Frames were constructed by Keith Chappel of Kickwood Audio and are built up from two laminated sheets of 18 mm baltic birch plywood, using rabbeted joinery and bracing which also supports and restrains the motor of the 18-inch Goldwood bass driver.

Attachment:
Open-Baffle-Speakers-Audio-Nirvana-Classic8-Goldwood-GW-1858-back.jpg

And here are the open baffle speakers setup in the listening room and configured using active crossover and bi-amplification.

I'm out of time for now but I will add more info soon.

Attachment:
Open-Baffle-Speakers-Audio-Nirvana-Classic8-Goldwood-GW-1858.jpg

Cheers


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PostPosted: 06 Aug 2017, 11:54 
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Very nice, and time aligned to.


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PostPosted: 07 Aug 2017, 09:04 
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Thanks Laurie. They are virtually time aligned, off by about only 15 mm (1/2") with how I set them up. The baffle wings are only about 5.5" wide and I was worried that this short length would result in the open baffle speakers being tipsy. I was aiming for about 8 inches, but limited by the sizes of the plywood cutoffs and trying to time align the drivers as much as possible I went with 5.5" and that seems to be enough provided you take time to square it all up nice. Open baffle wings less than 5" might begin to become problematic.

The 2 piece open baffle speakers are big and clunky, but they are nice as you have the ability to physically position and aim the high frequency drivers independent of the bass drivers.

Today I should get a chance to set the crossover point with a microphone. It's always interesting to see how close I came in dialing in the crossover by ear.

Cheers

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PostPosted: 10 Aug 2017, 21:59 
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After proper speaker placement using a mic I managed to get a pretty good in-room response using a crossover point of 175 Hz and a 4dB slope. The measured loudspeaker response is below.

Attachment:
AN-Classic8-GW-1858-inroom-frequency-response.png


So far, I am really pleased with the results from this speaker combo.

Cheers


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PostPosted: 01 Sep 2017, 22:33 
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To try an extend the high frequency response of this open baffle speaker out further I decided to try and integrate a Radio Shack horn super tweeter. As descrived previously, the crossover is an active two-way setup for the bass and fullrange drivers and for the tweeters I am tapping off of the fullrange driver and using a simple passive 1st order crossover (just a cap).
Attachment:
Open-Baffle-Audio-Nirvana-Classic8-Goldwood-GW-1858-Horn-Super-Tweeter.jpg

The horn super tweeters add that little bit of air and sparkle above 12kHz. This ended up with a pretty good extended 3-way response with only 2-way crossover bi-amplification.


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