Has anyone seen a downward firing OB woofer? After some searching I can't seem to fan any examples and I'm wondering if there is a reason that's above my honestly limited technical understanding. I have some 6 and 8 inch IB suitable woofers laying around and it gave me an idea for a small FAST / WAW OB system using a downward firing LF driver as a "sub" in an H or U configuration. I thought on a hard surface like a hardwood floor or desk you would get get better output and extension from the smaller driver, which could be nice in a small room or near field scenario. It would also keep the whole array shorter in height.
Am I smoking crack? You can be honest 🙂
Am I smoking crack? You can be honest 🙂
Nelson Pass developed an open baffle (one fullranger) with a downfiring woofer (Eminence Deltamax?) in a slot at the bottom. Search around the Pass forum or just Google it.
That slot loaded design looks pretty ingenious, I have no idea how to go about calculating a slot loaded open baffle. My experience with designing and building boxes is just sealed and single reflex ported by plugging T/S into online calculators. What kind of calculator would you use for a SLOB design? Looks like a typical slot load is modeled as a 4th order bandpass, but would that account correctly for the Open Baffle element?
Last edited:
Here is what I would suggest:
You will need to figure out the effects of the baffle for the upper driver (NP used a fullranger). There is a program called 'The Edge' that is very useful for these kind of simulations. Make sure to check the box for "open baffle". Use the driver Sd to determine its equivalent diameter, and enter the dims for the baffle and location of the driver. It's more or less intuitive. Then you move the "mic" icon around to see how the response changes at different angles. There is an icon above the plot that lets you "freeze" the current curve. Do this multiple times as you move off axis and you will get an idea about the response pattern.
Then you need to decide where to cross over the woofer. It's difficult to model this, but you could try using HornResp. Otherwise I would just take NP's lead, buy the same driver, and then do some measurements to see where it should be crossed over. There might be some info on this already in the thread I linked to above.
@Charlie
Thanks. I'll check that out. After a couple more hours of looking around I found "slot area is approximately 1/3 to 1/4 of the driver total Sd, depending of xmax of the speaker", "Driver total SD would mean all of the drivers sharing the same air space. If you have a 10" speaker with 340cm2 of SD, then you need 85-170 cm2. If you put a 2nd 10" woofer in the same cabinet, you would need to double that area." Seems legit, but a little loosy-goosy. It would be interesting to test this against the software results you mention. I am working with an 8 inch speaker and going to mack things up in xps foam so it wouldn't be the end if I did a couple variations and test FR between.
Thanks. I'll check that out. After a couple more hours of looking around I found "slot area is approximately 1/3 to 1/4 of the driver total Sd, depending of xmax of the speaker", "Driver total SD would mean all of the drivers sharing the same air space. If you have a 10" speaker with 340cm2 of SD, then you need 85-170 cm2. If you put a 2nd 10" woofer in the same cabinet, you would need to double that area." Seems legit, but a little loosy-goosy. It would be interesting to test this against the software results you mention. I am working with an 8 inch speaker and going to mack things up in xps foam so it wouldn't be the end if I did a couple variations and test FR between.