July 16, 2010
Open baffle made easy
Here is a simple path to open baffle bliss. You could put this together in a weekend and see if open baffle is for you.
1. First start with either a full range driver or a conventional passive 2 way with a tweeter and mid.
The full range driver can appeal with it's simplicity, although finding the right driver with the right trade offs can be challenging. You want one with a reasonably flat response, top end extension, reasonable xmax and good efficiency.
Some of the Mark Audio drivers at Darcher Audio are worth considering. As shown above.
You might also consider CSS:
Want something exotic? Try this - Tang Band's take on an efficient fullranger. To get an efficient fullranger means a larger cone that now requires a whizzer cone to keep the top end extension. This one is 95 db efficient! It also has a nice flat response and decent xmax. The only issue is that the response slopes up so without EQ it will sound a little forward. If you follow my suggestion that follows and run an active crossover then that is easily fixed. Here it is:
You could also substitute a passive 2 way here, with many designs available on the internet. In keeping with the easy approach, go with an existing design. Check out the usual suspects like Zaph Audio, Tony Gee's Humble Home Made hifi and Troels Gravesen. I'm being lazy here and not hotlinking these, but simply Google them and you'll be there in 5 seconds.
2. Make the baffle about 400mm wide with 100mm folded back wings
That's a decent compromise of extension and modest size.
The dipole roll off can be estimated by adding a first order high pass at fequal to the response in a sealed box.
fequal = 58/D where D is half the baffle width plus the wing depth (in this case 0.3m)
fequal = 193 Hz
A typical 6.5" midbass with an fs of 40 Hz will be -3db @ 80 Hz when sealed.
3. Add a woofer - 12" or 15"
You have a wide baffle, why not use it?
4. Add a digital active xo like DCX or MiniDSP and cross around 300 - 400 Hz so there is no dipole rolloff to compensate for
And there you have a simple open baffle speaker - time to listen to music!
Want to see something like this I've put together? Here is a version I put together out of scraps:
Quick 'n dirty OB >
Check out the options for active crossovers. Behringer DCX is a popular choice, but MiniDSP is a new low cost simple solution that is purpose-designed for diyers. Read more about active options >
Posted by Paul Spencer