Designing my first open baffle, questions.

[O_ROD]

Hey guys, I'm going to be making my first open baffle speakers and need a few pointers. First, how big does the baffle have to be to sperate the front and rear waves so no cancellation results? This is the woofer I'm going to use since i already have them:

Nominal Impedance:........................................ ...........8 ohms
Frequency Response:......................................... 30 Hz - 2500 Hz
Free Air Resonance (Fs) Frequency:....................................30 Hz
Infinite Baffle Resonance Frequency:..................................29 Hz
Piston Area (SD):............................................. ....0.0360 m2
Rated Power Input - Nominal:.......................................... .50 W
RMS Thermal Power Limit (PMAX):.......................................100 W
Flux Density (BL):............................................. .....8.27 TM
DC Voice Coil Resistance (RE, ohms):...............................6.6 ohms
Voice Coil Inductance (LVC at 1 kHz):...............................1.13 mH
SPL:.............................................. ........87 +/- 2 dB/1W/1m
Moving Mass (Mms):............................................ ......35.19 g
Electrical Q Factor (QES):............................................ .0.61
Mechanical Q Factor (QMS):............................................ ..4.6
Total Q Factor:........................................... .............0.54
Equivalent Acoustic Volume (VAS):...................................181.2 I
Mechanical Suspension Compliance (CMS, UM/N):...................963.17 UM/N
Mechanical Mass of Cone Assembly and Free Air Load:.................35.19 g
Mechanical Mass of Cone Assembly Only:..............................31.14 g
Peak-to-Peak (maximum) Linear Excursion:............................2.25 mm
Cutout:........................................... .....9 1/4 Inches/23.5 cm
Depth:............................................ ....3 15/16 Inches/9.8 cm
Power Handling:......................................... .......50 Watts RMS
Magnet Weight:........................................... ...........11.6 oz
Speaker Weight:........................................... ..........42.4 oz

A tweeter will accompany it crossed over at 3000hz. I plan on using the woofer fullrange a la Epicure E100's.

[454Casull]

An open baffle with no cancellation is an infinite baffle.

[auplater]

Well.. to start, regardless of the woofer specs, you'd want (from an overly simplistic perspective) at least 1/2 wavelength width at the lowest frequency you want to not suffer cancellation.

87 db +/- and 50 watts RMS doesn't sound like a good combination for very loud open baffle, though...

You might want to <google> baffle width / cancellation and read up abit...

[owdi]

I used The Edge to design my current OB project. So far acoustic measurements seem to line up with modeled response.

http://www.tolvan.com/edge/help.htm

Dan

[Paul W]

9" woofer cutout with 1mm xmax? You may want to Google for Linkwitz spl-max spreadsheet before cutting wood.

SL provides excellent reading on his site.

[O_ROD]

That linkwitz site is quite amazing. Alot of information. I ran the spl-max spreadsheet and there doesn't seem to be much bass at all below 75hz. For fun I created an OB for the speaker and ran some music through it. I loved the sound it created, very open and accurate, but the SPL wasn't there in my large living room. In the computer room, which is much smaller, it produced a very nice sound and tolerable spl levels. I'll be going back to the drawing board...