I had the idea to combine the mid range and tweeter section of the Philharmonic BMR towers with an Eminence 15 woofer in an open baffle. Raal tweeter and BMRs would be in a MTM configuration like in the tower. I've built crossovers but always from kits or circuits that were pre-designed but never my own. I need A LOT of help figuring out what to do here? I have an inquiry out to Philharmonic Audio to see if they'll share some info with me or sell me x-overs but I've not heard back. I'm thinking I want to x-over to the Raal at around 3K hz (as specified in the Philharmonic BMRs) and a x-over to the Alpha15 at around 500-600hz. The Philharmonic towers use a 4th order Linkowitz-Riley x-over between the tweeter and the BMRs and a second order Linkowitz-Riley to the woofer. Ive heard that the x-over point on the Alpha 15 should be set much lower to get a higher actual crossover i.e. 100hz would give a x-over at 700hz for example. Not sure what I'd need to achieve a smooth transition between the Alpha 15 and the BMRs. Any help and advice (including you are in way over your head) is welcome. Thanks
Does this mean the T and M section will be radiating forward and the 15" will be open at the back?
I was planning on the whole thing being dipole, all on one baffle. Wings on the back side of the baffle only on the woofer
Well, it's possible that you're in over your head. 😀
Designing a 3 way open baffle speaker with a passive crossover from scratch is not a small task.
If this is your first build, you might consider building an exisitng design. There are some around that use the Eminence woofer (or similar) and a small wide band driver - which is pretty much your plan, if we leave aside the Raal tweeter, which is not a dipole tweeter anyway.
See here:
and here:
http://www.quarter-wave.com/OBs/OB_Theory.html
You could always experiment with adding a tweeter later.
Designing a 3 way open baffle speaker with a passive crossover from scratch is not a small task.
If this is your first build, you might consider building an exisitng design. There are some around that use the Eminence woofer (or similar) and a small wide band driver - which is pretty much your plan, if we leave aside the Raal tweeter, which is not a dipole tweeter anyway.
See here:
and here:
http://www.quarter-wave.com/OBs/OB_Theory.html
You could always experiment with adding a tweeter later.
Last edited:
thanks guys, this is exactly what I needed to hear. I built an open baffle using Martin King's design on quarter-wave.com using the the Alpha 15 with a Tang Band 2145. It sounds really great but it beams and doesn't have great off-axis response. I was looking to make something with wider dispersion. I'm happy to duplicate that design but would love to try and improve upon my first build
Ok, now I see. You could try adding a tweeter to your existing speakers? (Or even try a rear tweeter, since I don't think there'll be much rear output from the whizzer on the 2145.)
ianbo, that's a good idea! I've been toying with the idea of adding a rear facing tweeter to my existing speakers. Do you have a recommendation? However, I've already done a lot of the woodworking to create new OB speakers. I was thinking about using the full range LGK from GR research. It's a 3 inch speaker. Maybe it would suffer less beaming? I tried the Fostex 103En and I didn't really like the sound. Imaging was good but midrange sounded anemic. Also the planar magnetic tweeter from GR research looks interesting for adding to the full range. Again, maybe I'm getting in over my head. Just trying to expand my knowledge and improve on the sound
Full range drivers in general just narrow a lot, that's just a limitation of trying to get a large cone to play high. You're going to run into this even on smaller drivers, it will just occur higher up than your Tang Band. Adding a tweeter would not be that difficult of a task and would likely improve the speakers sound. Filters will need to be designed of course.
For possible OB tweeters, see this thread too: https://www.diyaudio.com/community/threads/options-for-dipole-highs-tpl-vs.409147/