The big advantage over a subwoofer is that the crossover can be higher as we know we are colocating the bass module with the monitor. Subwoofers are great and all, but conceptually serve a rather different role.
How do you like the Kairos/Adelphos? Always wanted to build one.SB makes some killer, sanely priced drivers. Not a lot of first hand experience except for building a J. Bagby design using Sartori 7" midbass + ring tweeter. Very, very nice using either passive XO or my digital ones using brick wall slopes. Both Jeff and Troel among many others have make very popular designs using them as I am sure you're aware. Sounds like a very interesting project. I am sorely tempted to try something similar with my monitors as I'm migrating platforms from 6 ch dig out to 8 and have the option finally--but I'm looking at a grand for the midbass units (Scandanavian sourced so high ouch factor) + new cabs. If you do spring, hope you'll post a build thread.
Jeff Bagby suggested the use of the SDX10 or a large SB woofer to form the basis of his bass module for his bookshelf speakers. The thing these drivers have in common is that they have considerable bass output with extended midrange (relatively speaking).
As a DIYer, I have a lot of speaker ideas, but what they all have in common and need is strong bass and mid-bass. If you look at all the innovative speakers at ASR, they differ in dispersion from schroeder/300hz or so on up. Below that it's all about bass output and extension.
My thinking recently is to build something like Bagby's bass module which can act as a stand for a variety of mid-treble modules on top, which I can swap out as I see fit. Some may need only sub-bass augmentation while some may need mid-bass. I'm working on a little omni speaker. I have a conventional stand mount with a waveguide. Maybe one day I'll make a dipole! All these things are easier if I have access to a 3' pedastal with incredible bass and mid-bass output.
Another thing that's nice about a bass module is that it makes it so much easier to move a speaker around. I'll never again build a dual 8" speaker with a mid and a tweeter all in one box. It's just a total nightmare to move and even work on.
As far as driver manufacturers, SB Acoustics and Dayton Audio are far and away the best value. There are a handful of other high-value drivers from Peerless, Scanspeak and others, but SB and Dayton are your best bet for almost everything.
Now, if I can offer a comment on the original directiva. What is it that makes that speaker work so well? It isn't the active topology, since we have seen passive crossovers can achieve the same transfer functions at reasonable cost. It isn't the bass extension, which is good, but not better than a tower speaker with similar footprint. It's the smoothness of the directivity, which is mostly accomplished by the DXT tweeter, a now very old design, and to a lesser extent, the smoothness of the purifi top octave.
I would recommend sticking with the DXT. Short of 3d printing a waveguide or using the new SB Beryllium unit ($$) it is the best way to get stellar off axis performance.
I have a 300mm cubed 3d printer if you want to experiment with waveguides. 8 inch two way?If I may add: for a larger more capable speaker it would be nice to see something that holds its pattern control down to at least 500Hz. As good as the directiva is, it (and practically all 'narrower' models) doesn't hold its pattern down very low. For longer listening distances, in my opinion, holding pattern control down to a lower frequency is benificial. Recent objective tests (not by myself) confirm this.
I have a 300mm cubed 3d printer if you want to experiment with waveguides. 8 inch two way?
Ah clever.That's pretty cool! But it's easiest to control the pattern control down that low through using a wider baffle - hency my ATC style speaker suggestion a couple of posts up.
Ah clever.
Troels' PMS speaker with SB drivers and better DI? That could be sweet.
Wide baffles also make passive network designs easier.
Have you done any measurements on wide baffles? How wide do you need to get for pattern control down low?
If we did a mini PMS and use a bass module, am pretty sure @ctrl already has done something like that…
Can we do a cardioid this time? Its the only thing that has the potential to top the spinorama.
Was in my plan to control the hiss anyway…I'd very much consider doing an active/passive hybrid if the design allows for it, which I believe it does, for reasons posted already.
Was on my bucket list until I found out how much open space the LX521 needs.
Not sure how much community interest there is either…
Maybe time for a poll.
In a 3 way with a competent midrange it's possibly to give cardioid behaviour in a resistance cabinet, it would basically be the same effect as a wide baffle, but in a narrow style cabinet. One could do that to 300-400Hz and let a bass driver take over from there down low.
By competent you mean high excursion?
And a cardioid would require dsp to work, wouldn't it?
I think we should list and order priorities and requirements here. This helps me create limitations and goals.
The project is called Directiva, so let’s start with
1) Directivity
-Should have uniform directivity for EQ, spatial effects, and off-axis listening.
2) Low distortion
-The most noticeable issue in any speaker is when it distorts. It can’t be EQd away and it can’t really be made up for passively.
3) Flat response
-A flat frequency response is essential to applying the speaker to a variety of applications. This isn’t strictly a theater or music hall speaker (unless we choose for it to be).
4) Wide parts availability
-Parts should be easy to source from a variety of locations across the globe. Our circumstances have led to supply chain issues, materials shortages, and technology oriented redesigns. We should make an effort to remain accessible.
5) Footprint
-I would like it if the size of the Directiva remain non prohibitive. The R1 has a nice shape to it. It could be a tower, but an oversized bookshelf could do nicely.
6) Cost
-This has to be determined by the community. I can’t afford to ‘play’ with a $500 speaker. I’m probably never even going to build the R1 because I have similarly performing bookshelves I’m happy with. I’d love to have an experimental and inexpensive build, or a high quality “halo” build that won’t need replacing at any point.
7) Range
-How deep will this go? Is it intended as a full range speaker or are we only going to a decent place for crossing with a sub? Those 8” Dayton’s are no joke, but may need stacking to truly be considered a acceptable sub-bass. Definitely good for the money, though. I’d be happy owning a design that utilizes those woofers.
I’d really like to know what everyone’s priorities are here. I haven’t even covered some very essential parts, like build complexity and SPL goals. What’s the intended use for a speaker like this? What’s our thesis? R1 is about proving the capability of the 6.5” long throw driver. What are we going to prove this time?