Modular Active Crossover Boards in development

[Deward Hastings]

Re: Modular Active Crossover Boards in development

But if you want to build a basic 2-way speaker, it is really overkill.

Yes . . . and at some price point it devolves back to "passive" and just using the amps in the HT receiver. Where the "transitions" occur is continuously evolving, what with "active" crossovers and excellent amplifiers becoming ever less expensive . . .

[jpomann]

Re: Modular Active Crossover Boards in development

These sell at about $110 for one board and one software package for it. If you want to install one in each speaker cabinet you need to buy TWO. A stereo pair of my main board and filter board should come in below the cost of ONE of the MiniDSP boards.

-Charlie

What do you estimate the the total cost would be for your kit, for a 2-ch 3-way system, including boards, components, and all pots? (minus power supply, connectors, chassis, etc.)?

JP

[Æ]

Re: Modular Active Crossover Boards in development

I'm definitely curious and probably interested. I'll be watching. Thanks

[penngray]

Re: Modular Active Crossover Boards in development

The MiniDSP does seems like a new roll-your-own DBX2496. It's a very interesting product, really. But if you want to build a basic 2-way speaker, it is really overkill.

-Charlie

The miniDSP, DCX are only overkill if you enjoy building passive XOs.


btw, Great thread its great to read about new active crossover options. If your price point is true then you can put me down as a buyer too :D

[mzisserson]

Re: Modular Active Crossover Boards in development

. It looks like the active crossover is finally becoming cheap-and-easy enough (along with low-cost high quality Class D amps) to see significant adoption . . . a good thing for "quality" audio . . .

That is the key. I am as geeky as the next guy, but from what I have seen of active x-overs, they take WAY too long to tune in properly, then if you move your speaker 1" you are screwed.

This is a great concept, affordable (I assume) and fun for a DIY-er, not convinced a consumer will prefer over plug & play, but I would love to get one, build a passive x-over, and A/B.

[penngray]

Re: Modular Active Crossover Boards in development

I think that the competition is the MiniDSP boards. These sell at about $110 for one board and one software package for it. If you want to install one in each speaker cabinet you need to buy TWO. A stereo pair of my main board and filter board should come in below the cost of ONE of the MiniDSP boards.

-Charlie

Remember MiniDSP offers a finished solution. $170 gets you a nice little black box, RCA input/outputs, USB powered solution shipped with your choice of downloadable apps. I own 3 of those MiniDSPs already, best EQ out there for subwoofers IMO and most powerful sub $300 choice for 2-way XOs (cascading filters, 96dB slopes....any transfer function you want).

IMO, no one is installing MiniDSPs on the back of speakers unless they have plate amps there.

MiniDSPs are sitting hidden in audio equipment racks.

I guess I might not be buying, In not interested in soldering anything every again in my life time.

[penngray]

Re: Modular Active Crossover Boards in development

That is the key. I am as geeky as the next guy, but from what I have seen of active x-overs, they take WAY too long to tune in properly, then if you move your speaker 1" you are screwed.

This is a great concept, affordable (I assume) and fun for a DIY-er, not convinced a consumer will prefer over plug & play, but I would love to get one, build a passive x-over, and A/B.

You build a passive XO for your speaker and its 100% set, you have to place your speaker at an optimal location in room and you have ZERO tweaking abilities to solve room issues. You also are stuck with XO parts. We can constantly build and tweak, build again and reuse these great devices.

Active XOs are superior to passive designs in so many ways. See Elliot, Linkwitz, etc weblinks for that.

IMO, this is never about the average consumer. They will buy crap speakers and never know anything about audio science and most of them still think BOSE is a great audio product. I think we can just ignore those consumers ;)

[Jed K.]

Re: Modular Active Crossover Boards in development

Click Here to view the Attachment: MODULAR CROSSOVER OVERVIEW.pdf


.

Awesome work! I've got a few ideas on how I can use this product. Thank you for your efforts.

Jed

[Deward Hastings]

Re: Modular Active Crossover Boards in development

from what I have seen of active x-overs, they take WAY too long to tune in properly,

? ? ? It is *far* easier to "tune in" an active crossover (than a passive) . . . and far easier to implement changes in the "built" design. With the digital ones you press a few buttons or keys on the computer, with Charlie's you turn a few trimpots. That sure beats breaking out the Weller and the LCR meter to "trim" inductors and caps. And "design" goes faster too . . . I don't understand why so many people ignore the *active crossover simulator* on the *right* side of the PCD spreadsheet . . . you should try it. Just enter the slopes and crossover frequencys, and the correct delay for acoustic offset, and see how much *better* the curves look than those you got after fighting driver impedance all evening on the "passive" side. And you can still add a couple passive components (if you want) to trim the driver response[s] and make the textbook curves of the active crossover work even better . . .).

then if you move your speaker 1" you are screwed.

Active crossovers are no more sensitive to placement than passive . . . where did you get that idea? What is position dependent is diffraction effects, and you cannot correct those with *any* crossover (or "equalizer"), active or passive (except at one location . . . all but useless for a HT "listening area" or for anyone but the lonely bachelor who listens to his stereo with his head in a vice . . .

[dlr]

Re: Modular Active Crossover Boards in development

Hey All,

I am currently developing modular active crossover PCBs that have baffle step, fully parametric EQ, and make it possible to create a wide variety of crossover functionalities/topologies. Basically, it's all the goodies that you need to construct a serious crossover for your 2-way, 3-way, 4-way speaker or subwoofer system!

I have designed the circuit boards and sent them out for prototyping. Hopefully I will have everything tested and checked out by the end of JAN. Once all the kinks are worked out, I plan to offer these as kits of PCBs plus parts. Some assembly required.

For now, click on the link below to get an overview of how they work, and what they can do.

-Charlie


Click Here to view the Attachment: MODULAR CROSSOVER OVERVIEW.pdf


.

Interesting. One question I have is the baffle step section with the shelving filter. It appears to be a single section per system rather than a section per driver. Am I reading that correctly? For multi-way systems (as in 3-way or more), this could be an issue depending on the design, primarily for dipole systems where you'd want this separate for the woofer and midrange at a minimum.

dlr

[charlielaub]

Re: Modular Active Crossover Boards in development

Interesting. One question I have is the baffle step section with the shelving filter. It appears to be a single section per system rather than a section per driver. Am I reading that correctly? For multi-way systems (as in 3-way or more), this could be an issue depending on the design, primarily for dipole systems where you'd want this separate for the woofer and midrange at a minimum.

dlr

dlr-

Thanks for asking the question relating to OB loudspeakers. First, you are correct - there is a single section for baffle step compensation on the main board. When I designed the signal flow in the crossovers I had "box" loudspeakers in mind primarily, and only realized the use of the first-order shelving filter for open-baffle speakers later. If you want to use the baffle step compensation for open-baffle loudspeakers then you might indeed need to use one "main board" per open-backed driver, but that would also permit EQ dedicated to that driver (alone). It's more complicated and expensive on account of the additional board, but you can choose to go that route if you so desire because the design is modular.

With that in mind, I believe that only one first order shelving stage plus EQ is needed for the typical "box" loudspeaker. The baffle step is primarily dependent on the smallest dimension of the front baffle (typically width) and this is usually the same for all drivers, thus the basic shelving-filter baffle step correction is roughly the same for all drivers.

Think of a 3-way system as a baffle-step compensated 2-way system plus a subwoofer driver near the floor. The driver near the floor is getting boundary reinforcement that increases gain and the response will be relatively flat until the floor bounce kicks in - let's say this is at 300Hz. If you cross over to the sub from the baffle compensated 2-way at around 100-150Hz, you can avoid this region. This is where you want to cross over a lot of subwoofer drivers anyway. This leads to an incremental speaker build that one can easily do with the modular crossover boards - start with an inexpensive 2-way monitor and then later add a "base" containing a subwoofer driver located near the floor and on which will rest the original 2-way speaker. The crossover for the 2-way can remain the same, and an additional filter board will provide the extra stage(s) required to construct the crossover to the subwoofer. The DIYer can start with a simple build and later expand it without having to redo anything. Another approach would be to add on the modular crossovers to a small passive 2-way (like the NCDIY2010 project that I, Mark K, Jeff Bagby, and others developed) in order to add a subwoofer, since an electronic crossover in the 100Hz region offers many advantages compared to a passive one.

-Charlie

[charlielaub]

Re: Modular Active Crossover Boards in development

What do you estimate the the total cost would be for your kit, for a 2-ch 3-way system, including boards, components, and all pots? (minus power supply, connectors, chassis, etc.)?

JP

Well, although I am not really ready to set prices since I am still finalizing the designs, I can probably give you a ballpark figure within +/-20%...

The most basic 3-way system, with two main boards and two filter boards, with all parts and including dual-mono regulated power supplies (but not the transformer for the PS) is in the range of, let's say, $80 total. I think. It partially depends on how many people express interest in buying them...

-Charlie

[dlr]

Re: Modular Active Crossover Boards in development

dlr-

Thanks for asking the question relating to OB loudspeakers. First, you are correct - there is a single section for baffle step compensation on the main board. When I designed the signal flow in the crossovers I had "box" loudspeakers in mind primarily, and only realized the use of the first-order shelving filter for open-baffle speakers later. If you want to use the baffle step compensation for open-baffle loudspeakers then you might indeed need to use one "main board" per open-backed driver, but that would also permit EQ dedicated to that driver (alone). It's more complicated and expensive on account of the additional board, but you can choose to go that route if you so desire because the design is modular.

I like the modularity, that does provide good options. Around your ballpark price, it looks very promising.

dlr

[bvn]

Re: Modular Active Crossover Boards in development

How can an active XO "screw" you?. It's phasor neutral. Shelving and roll off is another matter.
---
I notice that the design is unbalanced. So are you thinking RCA -10dBv line reference. Then no CMR or ground lift, implying that the sources and sinks are co-located, with multiple, long run, low Z power the speakers? Which in turn, implies "near field". Or, am I missing something?
---
Also I see, that you have an interesting opportunity to determine the price point:-)
---
Re Aram Bose. I am always impressed with how his company's designs manage to get 10 lbs of xxxx into a 5 lb. bag (really, no joke).

[charlielaub]

Re: Modular Active Crossover Boards in development

I notice that the design is unbalanced. So are you thinking RCA -10dBv line reference. Then no CMR or ground lift, implying that the sources and sinks are co-located, with multiple, long run, low Z power the speakers? Which in turn, implies "near field". Or, am I missing something?

If a balanced input/output it to your liking, then it's easy to throw one of these (or similar IC) at the front/back end, on a separate board?
http://focus.ti.com/lit/ds/symlink/ina134.pdf
http://focus.ti.com/lit/ds/symlink/drv134.pdf

The former is like $4 I think and the latter about twice that.

-Charlie