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.
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Directiva r2 project: market requirements gathering
- Thread starter Rick Sykora
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Maybe a passive/active hybrid? Three way with a passive crossover bedween mid (dome/cone?) and tweeter and and a DSP crossover between mid and woofer. This way it can be powered by quite a few plate amps or a miniDSP 2x4. Something like a better ATC50 or 100. There's also the advantage of a high-pass filter on the woofer and limiter options. Not to mention built-in room EQ for the bass.
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JRS
Major Contributor
Jeff's notion was among several influences that led to my current system which is 3-way, the midbass and tweeter housed in a 0.75 cu ft enclosure and separate bass modules. When I designed the bass units, I took an either/or approach as I wasn't sure if I might later use them as true subs, and modify the monitor into a 2.5 system with an f3 in the 45-50 range. So I looked for a wide range 15" driver that could be driven hard with EQ to obtain flat response high output into the 20's in a relatively large room (should I move into a larger space). I looked long and hard at a variety of SB and Dayton woofers before buying Acoustic Elegance 15H's. They were pricier than I had planned, but easily rationalized as woofers that would never need to be upgraded, were wideband (some being used as studio monitors well North of 500Hz), and could absorb huge amounts of power. The one problem was the cabinet requirements are large. I settled on a flat pack 3 cu ft. The alignment was QB3 with an f3 of around 40, to which a Linkwitz type filter was added bringing the f3 to 31Hz (not looking for special effects). The woofers are XO'ed at 275hz.
As for as WAF, not a consideration as these were to be located in a family room/AV room. If I were to change anything, I'd make them deeper and taller--on top of the speakers they are a few inches too low, fixable with feet. But I just as soon they be isolated and so the monitors are on stands.
One thing I noticed about Jeff's design is that he chooses to have the woofer on the high side of the enclosure, whereas I took the opposite approach in an effort to avoid floor bounce, and I can align the drivers electronically. I might try in the future to point the woofers sideways, and make them deeper and narrower if I like the sound more, and put the monitors on top for a better aesthetic.
Anyway, I think this is an interesting approach. It adds quite a bit of flexibility--building monitor sized speakers is a helluva lot easier than actual 3 way cabs, so if I get bored or say jump on with this project, I'm in a position to do so and use the others as bookshelfs +/- small sub for a second setup.
As for as WAF, not a consideration as these were to be located in a family room/AV room. If I were to change anything, I'd make them deeper and taller--on top of the speakers they are a few inches too low, fixable with feet. But I just as soon they be isolated and so the monitors are on stands.
One thing I noticed about Jeff's design is that he chooses to have the woofer on the high side of the enclosure, whereas I took the opposite approach in an effort to avoid floor bounce, and I can align the drivers electronically. I might try in the future to point the woofers sideways, and make them deeper and narrower if I like the sound more, and put the monitors on top for a better aesthetic.
Anyway, I think this is an interesting approach. It adds quite a bit of flexibility--building monitor sized speakers is a helluva lot easier than actual 3 way cabs, so if I get bored or say jump on with this project, I'm in a position to do so and use the others as bookshelfs +/- small sub for a second setup.
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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 ($$) it is the best way to get stellar off axis performance.
As a DIYer, I have a lot of speaker ideas, but what they all have in common and need is strong bass and mid-bass. If you look at all the innovative speakers at ASR, they differ in dispersion from schroeder/300hz or so on up. Below that it's all about bass output and extension.
My thinking recently is to build something like Bagby's bass module which can act as a stand for a variety of mid-treble modules on top, which I can swap out as I see fit. Some may need only sub-bass augmentation while some may need mid-bass. I'm working on a little omni speaker. I have a conventional stand mount with a waveguide. Maybe one day I'll make a dipole! All these things are easier if I have access to a 3' pedastal with incredible bass and mid-bass output.
Another thing that's nice about a bass module is that it makes it so much easier to move a speaker around. I'll never again build a dual 8" speaker with a mid and a tweeter all in one box. It's just a total nightmare to move and even work on.
As far as driver manufacturers, SB Acoustics and Dayton Audio are far and away the best value. There are a handful of other high-value drivers from Peerless, Scanspeak and others, but SB and Dayton are your best bet for almost everything.
Now, if I can offer a comment on the original directiva. What is it that makes that speaker work so well? It isn't the active topology, since we have seen passive crossovers can achieve the same transfer functions at reasonable cost. It isn't the bass extension, which is good, but not better than a tower speaker with similar footprint. It's the smoothness of the directivity, which is mostly accomplished by the DXT tweeter, a now very old design, and to a lesser extent, the smoothness of the purifi top octave.
I would recommend sticking with the DXT. Short of 3d printing a waveguide or using the new SB Beryllium unit ($$) it is the best way to get stellar off axis performance.
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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.
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?
OP
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Member ctrl could simulate this with certainty. In my practical 'experience' around 12" baffle width is a good compromise between pattern control and bulkiness. The Genelec 1032A I own have such a baffle and have quite decent pattern control.
Wider is better of course, but few people would want it in their living room.
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?
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?
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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.
OP
- Thread Starter
- #55
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.
OP
- Thread Starter
- #56
Was in my plan to control the hiss anyway…
From the posts, seems need to work on what before how though.
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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. The downside is it will take a lot of work to really fine tune a passive cardioid system.
By competent you mean high excursion?
And a cardioid would require dsp to work, wouldn't it?
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Sufficient excursion/power handling although if only used down to 300-400Hz it should be doable. In this configuration no dsp would be needed. In case of a hybrid one could use dsp as a highpass and shelving, but no dsp is needed for the cardioid effect. See my 'big 2-way' thread in the DIY section.
OP
- Thread Starter
- #60
While most of what you state above is all well and good, the part about the r1 and the Purifi woofer is not accurate. It was more about seeing what could potentially be done using smart people and the Klippel. The Purifi woofer was secondary - maybe tertiary.
Since I have had this conversation offline a couple of times already, thought would take time to set expectations. While this effort is based on community input, but the smaller team decides the design tradeoffs. At this risk of repeating myself, speaker requirements are about what it will be. The design determines how to meet the requirements.
If you want to participate on the design team, please PM me with why you want to be involved and what your key competencies are. Thanks!
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