Passive 3-way Dipole

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hello Folks, I've been out of the mix here for a few years for a number of reasons and I'm ready to tackle a new project.

With any project, if you are going to enlist the help of others, you want to get them up to speed on your design goals, desired outcome, etc. So I'm going to spend a little time and explain what I've listened to and what I like and what I'm trying to achieve. When I was new in the audio hobby, I heard a set of Martin Logan's. At the time, this was the most amazing thing I'd ever heard. I've subsequently had a set in my house for a while and loved them, but there are things that they don't do well. Rock music, for example.

From there I tried to build a set of speakers that captured that amazing open sound, while correcting some of the flaws and being able to reproduce pretty much everything. It took a few years, and I've designed and built a few sets of speakers since then; line arrays, simple two ways, a three way. About 9 or 10 years ago, I built some pretty amazing (to me) speakers that seem to do a pretty good job of doing everything I wanted. This was a 2-way that paired a large AMT tweeter with a pair of RS-225s in a solid box with a modified elliptical high slope crossover. I really like the sound of these. So much that the temp crossovers I build are still alligator clipped together. I didn't expect these to last this long, but I love the way they sound. Then I really started listening to drum music and I found something else that didn't get reproduced to my satisfaction.

Around then I stumbled into another set of crazy speakers, Hartley Concertmasters with those big huge 24" woofers. These had another trait that I coveted, they accurately reproduced the sound of a big drum. Of course, the high end was nothing like a dipole electrostat or AMT. Then there was the issue of trying to fit two dresser-sized speakers in the living room. I played with sticking an active crossover in place and just putting an AMT on top of the Hartleys. If I had the room, that would have been perfect right there. So, this is the sound I am attempting to replicate. AMT tweeter, 10" dipole midrange and 24" dipole woofer (quasi-cardoid is probably more accurate, it's an open backed box stuffed with some stuffing).

Next design goal, it can't be that darn big! I want these things to look fairly reasonable. For reference, Jamo 909s could be reasonable. I know they're big, but not Concertmaster big. I'd also like them to be at least pleasant to look at. I know we tend to be function over form types, but I'd like to pay at least a little attention to form. I've seen a couple nice designs that put everything on a surfboard shaped baffle. I think that's fair, perhaps with a shallow u-frame behind the woofers.

Now I know what I want it to sound like, what I want it to look like. I can also tell you I'd really like to stay passive. Adding lots of low end EQ and active crossovers is more complicated than I'm really interested in. Mostly because I've heard it done passively and I think I can duplicate that. Also, that's a lot of extra stuff that I think is unnecessary. I'm shooting for a fairly high efficiency design, at least with the tweeter and midrange, so accurately matching woofers at that efficiency might be difficult. I may entertain a line-level crossover between the woofers and the top end. Though, I'd prefer that be passive too. I have a set of crossover kits I bought on a group buy off here back then that I could probably use for this, I don't ever remember the specs, but I think they were analog active, yeah maybe I'll use those. I know, I'm waffling here. That's the reason I'm posting a design thread.

I mentioned efficiency earlier. I appreciate the benefits of a high-efficiency system. AMT tweeters are veryefficient, and I'd like to try to mate an efficient mid or mids up to that. I like my big Heils, but they don't look great mounted to a baffle, yes you can do it, no I don't like the way it looks. This is where my form gets in the way of my function. Until recently, I didn't think I could afford what I wanted which is one reason why this project stayed on hold for so long. Just now I've got a couple Beyma TPL150s I got a good deal on. I've heard a few different AMTs, they all share characteristics I like. I haven't had a chance to listen to these yet, but I trust they will do what I want them to. So, unless they do something horrible, I've got my tweeters.

A little while ago I picked up a couple of what I'm hoping will be my ideal woofer, AE Dipole 15s. I've got 2, I imagine I'm going to need 4 total, but I need to put these things on a baffle and listen to them before I get two more. I used a set of TD12s in a 3 way I built a while back, I know Lambda woofers sound good. So again, I think I'm in the right ballpark.

I'm not really sure what I want to do for midranges. I'd like to stay 3-way, and I'd like them to be efficient. I was originally holding out for a Dipole8 midrange from AE, but I've been holding for a couple years. I know John stays pretty busy, so his R&D time is minimal, but I think it's time I want to push forward without them. I've got a couple PHL 1120s and B&C 8PS21s that were original thoughts for this. I've thought about some others like 18Sound 8NMB420, BMS 8N515, using a pair of AE Dipole 6s per side, a BG Neo10 (though I don't think the neo10 will meet the visual aesthetic I'm looking for). This is probably the biggest spot where I'm looking for input. The pair of 6s vs a single 8 is probably my biggest conundrum.

Other than that, I think I need to get in the garage and start cutting MDF.

Please feel free to chime in. It's about to get dusty around here.

- JohnL
Considering the size of your drivers and CO point, I would stick to just one driver for mids.
If you do so, matching efficiency of TPL and mid will be a problem. You will either need to pad down TPL or use another tweeter.
Bass efficiency will also be a problem below dipole roll-off. So you might indeed need two AE dipole 15" per side.
When all things considered (cost of multiple woofers, dipole roll-off, baffle-step, efficiency matching), full active/DSP is probably the best solution (and perhaps the only acceptable solution).
I started a passive OB project but had to switch to active myself.
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.