# i wanna go All Active x-overs



## yelis300 (Nov 9, 2010)

what the best way to do this? right now i have 2 and 3 ways in my setup, fronts being TMM-port M and center MTM. So ive got 11 total speakers to x-over in the front. would i need to get several of the behringer dcx2496's to do this? what other options are there? :huh:


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## hgoed (Mar 22, 2010)

Take a look at miniDSP. I haven't used it, but I've read of lots of people who are experimenting with their offerings and very satisfied.

http://www.minidsp.com/


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## yelis300 (Nov 9, 2010)

those look interesting, how would one implement those, connection wise? i was thinking of actually crossing over each driver versus each channel. is that possible with these, assuming all the necessary connections are there?

i wanna do some diy speakers and set them up that way if i can. then i can just pick whatever drivers i want, put them in the appropriate size cabinet, and tweak to perfection.

im looking for a single driver with a near flat response in the range of 80hz to 10khz-15khz, the only ones ive seen capable of going that low and high are the planar/ribbon type that magnepan uses, but i havent been looking very long yet.


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## yelis300 (Nov 9, 2010)

actually i havent seen any graphs on those, i have just been going by the stated frequency response.

really, i could look for a nice midbass (80-200hz) and do some electrostatics with them too.


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## hgoed (Mar 22, 2010)

Well, I have some suggestions, but realize I'm a newbie too...just one who is pretty good at research.

The MiniDSP units were originally designed to act as an active crossover. The EQ features were added later. Depending on your source, there are many different options for how to build the crossover. I'd been wanting to do a DSP crossover since the early 90s, and this is the first product I've found where I wouldn't have to breathe lead fumes to make practical (meaning I didn't want to solder bare chips to a custom board etc...).

I've been looking at some full range drivers, which seem to be able to cover the mid and high frequencies quite well, without the need for the downsides of a crossover. Another benefit is that the overall box size ends up smaller, which is great for surrounds. Check out Mark Audio--I've been looking at their Alpair 10.2, but have bought some of the cheaper CHR70 to experiment with. All of his drivers have an excellent reputation with FR fanatics.

A lot of what you're planning seems very similar to my interests. What kind of source/interface do you plan on using? I'll share what I know and I don't mind if you think or tell me I'm full of it.


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## yelis300 (Nov 9, 2010)

honestly, i dont know what kind of source i can use, but i want to use it just for my HT, watching movies and the like from my BlueRay Player/AVR. nothing else really. And if i can figure out if these minidsp's can do what i want, which is to be able to crossover each individual driver rather than the whole 3 way speaker, then (if i can find one) start building some fronts,center and surrounds so that all the drivers are the same, and all crossed at the same point. then probably only 2 subs for everything under 80hz. that would be my idea of a perfect system.

i did more reading on these from another site and i think they can do what i want. has something to do with biquad? and cascading filters? being able to change slopes?

but im a newb so i dont understand alot of whats there.

im gonna look at those drivers u mentioned, ive got lots to read and learn.


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## hgoed (Mar 22, 2010)

The reason I asked about the source was only so that I could offer suggestions about interface. I'm assuming you have HDMI or SPDIF, or did you want to use analog (RCA)? I sometimes delve into the absurd, so I was looking at feeding a MiniAMP with I2S as I'm pretty sure those guys are developing an amp with more power than 20W and I can pull those signals off of just about anything.

The crossovers can be set up any way you want--by driver, channel or whatever. You seem to be talking about wanting to power each driver with it's own amp. That can be done, but try to figure out what exactly you're trying to accomplish first, because depending on the drivers you use and how they're wired, you can change how the "speaker" reacts to the power supplied...total impedence, current, blah blah. Just try to figure out why you're stuck on powering the M and M drivers separately.


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## hgoed (Mar 22, 2010)

I forgot to mention: for HT it seems there is a variety of tastes. You need to decide how much impact and volume you like. For impact/dynamics you need cone area and amp power. That, generally, costs space and (which nobody seems to consider) ongoing electricity. If you've got a smallish room, you can get away with smaller drivers and maybe even fewer drivers, can often control the room modes better and I think it would be easier to control imaging.


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## yelis300 (Nov 9, 2010)

well id be using spdif and/or rca for sources. i want lots of impact and dynamics, shooting for reference level 75db with the utmost clarity and still have some headroom to work with. i realize the in room db levels will be much more but thats what im shooting for. i already have 3 xpa 3's for power, so if i can use those for power with the minidsp units then thats what ill do. the reason i wanted each driver powered separately is for the simplicity of building standard rectangular cabinets and put in a single driver that covers basically the entire frequency range except 80hz and below. then it would be very simple for me to realtime analyze them and make the corrections. i could make the same exact box and use the same exact driver. then i wouldnt need to make a passive x-over, which i dont know how to do. i would need a larger miniamp like u said thou to make that work. 20x2 is not enough. ideally i would have amp power rms thats double the speaker rms.

but u said the minidsp can do what i want it to, so ill hold on to my current speakers for now and get those tweaked with the minidsp's.

those were some incredible looking drivers from mark audio, and they were really reasonably priced too. i may have to get a few of those here soon.


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## GranteedEV (Aug 8, 2010)

Hi.

DCX or MiniDSP are both excellent devices, and I'm also interested in active crossovers by Hypex, Rane, Tact, DBX, Dolby Lake.

But I believe you asked "What is the best?". The "best" is likely none of the above. It is, in my opinion, probably a DEQX HDP-3

http://www.deqx.com/products7.php

It is, in many respects, insanely powerful in its ability to integrate drivers into a cohesive loudspeaker. It is capable of making the absolute best loudspeakers in the world, plain and simple. 300db/octave crossovers with finite impulse response / absolute control over phase, the ability to get your frequency response down to a 1db window, and an included calibrated microphone with which to help design crossovers. Here is an article on it by Vance Dickason (of Voice Coil, also wrote the very informative "Loudspeaker Design Cookbook", and has designed some great speakers in the past)

http://www.deqx.com/assets/voicoil_review_feb2005.pdf

The tradeoff? It's very expensive. I can't imagine a full surround system using DEQX because of that. I can however imagine getting one DEQX HDP-Express (which costs less than the HDP-3 and has almost the same functionality) to cross over your main Left/Right speakers, a miniDSP to handle the center, and the hypex plate amps to handle surrounds. That would be my approach if I could afford it. I'm definitely a fan of miniDSP and how they cater to the DIYer rather than the pro audio segment.


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## yelis300 (Nov 9, 2010)

that thing looks insane, it is a bit pricey, but not totally out of reach. put some money away this year til next tax time, then use some or all of ur refund and walla. lol, im already trying to figure out how to get one. considering what it could do for a system it might be worth its weight in gold. get one of those, get some good quality drivers, then sit back and enjoy the show, or musical bliss if thats what ur into. what specs (t/s parameters) would you look for in a driver if you were gonna use this deqx hdp-3, since it can take care of virtually all of the weaknesses in a loudspeaker? would it just be a matter of the design of the enclosure?

forgot to add, the deqx site says that u could use one just for the fronts, and that they will become so cohesive that u wont even need a center channel anymore. it would create a phantom center channel. i dont know where i was going with that, it just sounded really cool to me.


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## GranteedEV (Aug 8, 2010)

yelis300 said:


> get one of those, get some good quality drivers, then sit back and enjoy the show, or musical bliss if thats what ur into.


As with any DIY Speaker, you still need great fundamental understanding and diligence to get it perfect. It's a powerful, powerful tool, but even the best tool is worthless if not used well.



> what specs (t/s parameters) would you look for in a driver if you were gonna use this deqx hdp-3


T/S parameters are not the way to put together a speaker. They make decent guidelines for a rough idea, but you need measurements, of things that a TS parameter cannot show. The most useful T/S parameter is Fs - resonant frequency. You need to make sure you are crossing over a good octave above fs, especially for tweeters. 

I don't mind recommending you some drivers but I get the feeling you've yet got some learning to do.



> t can take care of virtually all of the weaknesses in a loudspeaker?


Whoa! It can vastly _minimize_ the issues of _crossovers_. Loudspeakers have many, many weaknesses that you need to understand and address, that a DEQX won't "take care of"... Stored energy, power output, distortion, control of directionality etc are still things that contribute to the overall speaker.



> would it just be a matter of the design of the enclosure?


Not at all. Speaker design is sufficiently complex if you've never done it before! I highly recommend reading some books on audio reproduction and speaker design. Definitely read the works of guys like Floyd Toole, Earl Geddes, Vance Dickason, Ray Alden, Seigfried Linkwitz, Rod Elliot, and many others. On the bright side, it's a lot easier to fix "messing up" an active speaker than "messing up" a passive one. 



> forgot to add, the deqx site says that u could use one just for the fronts, and that they will become so cohesive that u wont even need a center channel anymore. it would create a phantom center channel. i dont know where i was going with that, it just sounded really cool to me.


A good phantom center channel is excellent. However if you listen to recordings with discrete center channels, it may still be worthwhile to do a center. Not necessarily immediately, but eventually. My center channel will probably use a Seas or B&C Coaxial driver.


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## yelis300 (Nov 9, 2010)

i definitely have alot of reading to do. i got on this active crossover kick because a few weeks back i read some thread basically saying that passive crossovers can really hold back alot of potential if they're not designed properly. i was really anxious to diy myself some speakers, but realized i would never be able to design a good crossover for it. my next thought was to get something that could do it for me, the closest thing i could think of was to go active, then i'd be much closer to my goal of some great sounding diy's. But there's alot i still need to learn before i can even go the active route. i just ask alot of questions to help me determine the best road to take to ultimately reach my goal.

are there any recommended books particularly suited for a beginner like myself u could recommend? especially in the designing of crossovers? Ive seen a few pages from "loudspeaker design cookbook" and it looked too advanced for me to be reading at this stage.


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## GranteedEV (Aug 8, 2010)

Ray Alden's book is probably an "easy" place to get started.

http://www.amazon.com/Speaker-Building-201-Comprehensive-Course/dp/1882580451

Although my advice is to build a passive 2-way based on someone's design on your own. That should really give you a better place to get started as it's a bit more "hands-on". It will give you a reference for what a great speaker should sound like, so you can try and "do better". You can eventually use it as a surround speaker. My suggestion would probably be an ER18DXT

But if you're serious about loudspeaker design, then as "complex" as that Loudspeaker Design Cookbook might seem, it's really the right level of "difficulty" to be approaching this with! But we can leave all that sort of discussion to another thread in the DIY speakers forum :neener: as the main focus here is that the DEQX is a very good tool but it's not "Speaker Building for Dummies". And remember, the HDP-express has much of the same functionality for less cost.


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