digital crossover implementation

[speakerdesign]

I want to go down the digital active crossover route but i keep coming up against problems which has prevented me and probably others from succeeding.

There are very few devices on the market. The only two are basically the behringer and the mini dsp.

The behringer is difficult to use if you have home level amps. The minidsp isnt getting many raving reviews so I am suspecting that it isnt that good.

And there is the problem of adjusting the overall volume. Plus with all the different stages, there is the problem of incorrect gain structure which gives you plenty of hiss and noise. I have been there done that.

Most studio monitors use an active crossover though.

So what is the best way for me to do this?

[Beau]

Re: digital crossover implementation

There are a few other options.

You might want to look at dbx. They have a product that is (allegedly) superior to the Behringer DCX2496 Ultradrive Pro Digital 24-Bit/96 kHz Loudspeaker Management System & Crossover ( http://www.parts-express.com/dbx-dri...ystem--246-171 ), and they have another that is comparable to the Behringer CX3400 Super-X Pro Crossover 3-Way/4-Way ( http://www.parts-express.com/dbx-234...only)--246-107 ).

[Wolf]

Re: digital crossover implementation

I want to go down the digital active crossover route but i keep coming up against problems which has prevented me and probably others from succeeding.

There are very few devices on the market. The only two are basically the behringer and the mini dsp.

The behringer is difficult to use if you have home level amps. The minidsp isnt getting many raving reviews so I am suspecting that it isnt that good.

And there is the problem of adjusting the overall volume. Plus with all the different stages, there is the problem of incorrect gain structure which gives you plenty of hiss and noise. I have been there done that.

Most studio monitors use an active crossover though.

So what is the best way for me to do this?

The listed units you mentioned are the only 'cheapish' ways to do it. Studio style pro gear can cost $4k, and do it too.

Later,
Wolf

[fpitas]

Re: digital crossover implementation

A friend uses a Steinberg UR824 USB DAC with his PC running JRiver for the crossover and EQ functions. Excellent SQ.

[ErinH]

Re: digital crossover implementation

First off, the miniDSP is a great unit with numerous rave reviews.

If you are looking for other options, look at the Rane RPM26Z. It can handle both pro and consumer level inputs (by handle, I mean it doesn't need to be fed an insidious amount of voltage to get juices flowing). It's a 2-channel in, 3-channel out. So, perfect for a 3-way active system (or a 2-way + dual subs). This is what I use for my 3-way towers. You can pick them up on eBay for the price of about $300-400 used.

[evilskillit]

Re: digital crossover implementation

The minidsp isnt getting many raving reviews so I am suspecting that it isnt that good.

That seems like a bit of an assumption? I haven't heard any complaints about the MiniDSP or any measurements showing that it has any problems. Linkwitz seems to think they're good enough for his active speakers as his new LXmini uses the MiniDSP for it's active crossover.
http://www.linkwitzlab.com/LXmini/Di....htm#reference
http://www.linkwitzlab.com/LX521/DSP_challenge.htm

There was someone who posted here that made a product that was basically the same thing as the MiniDSP but made by him instead, a competitor if you will. I can't remember the name of that product unfortunately but that one would be another option.

[asmd]

Re: digital crossover implementation

The only problem i have had with the minidsp is that the volume control occasionally disables itself and i have to USB back in to reenable it.
Workaround? i just wired in a pot into the input. Walah... analog volume control that wont ever cut out.

I do wish someone made one with a TI chip that has look ahead function and volume dependant dynamic EQ.. that would be just awesome.

Yamaha did it the analog way back when in the higher end CR series receivers form the 70s. a 10 step loudness knob with two whole pages dedicated on how to use it properly.

[speakerdesign]

Re: digital crossover implementation

That seems like a bit of an assumption? I haven't heard any complaints about the MiniDSP or any measurements showing that it has any problems. Linkwitz seems to think they're good enough for his active speakers as his new LXmini uses the MiniDSP for it's active crossover.
http://www.linkwitzlab.com/LXmini/Di....htm#reference
http://www.linkwitzlab.com/LX521/DSP_challenge.htm

There was someone who posted here that made a product that was basically the same thing as the MiniDSP but made by him instead, a competitor if you will. I can't remember the name of that product unfortunately but that one would be another option.

I have read about excessive noise, average quality dac and gain structure issues with the mini dsp.

This is basically the problem. It happens even with dacs. If you dont use the right dac, you will get noise and hiss and lack of dynamics. Its a compatibility issue. I cany afford to risk buying thee minidsp only to discover it doesnt work well with my dac or power amps.

Then there is the issue of volume control. Ideally you want a device which simultaneously controls the volume of 4 channels. They arent easy to find are they? This would be the ideal way of doing it though after feeding the minidsp with a fullrange signal either digitally or analogue. If you try to control the volume at the inpt then you get gain structure problems.

So those are the obstacles. And many of the crossovers are not compatible with consumer levels you would need step down transformer or something. Which gets costly.

And i cant afford to buy all of these bits and pieces only to discover it doesnt quite work as planned.

I bought the behringer crossover and it simply didnt work as planned. For obvious reasons.

[speakerdesign]

Re: digital crossover implementation

The only problem i have had with the minidsp is that the volume control occasionally disables itself and i have to USB back in to reenable it.
Workaround? i just wired in a pot into the input. Walah... analog volume control that wont ever cut out.

I do wish someone made one with a TI chip that has look ahead function and volume dependant dynamic EQ.. that would be just awesome.

Yamaha did it the analog way back when in the higher end CR series receivers form the 70s. a 10 step loudness knob with two whole pages dedicated on how to use it properly.

how are you using the minidsp?

the other complaint i have read with minidsp is that it accepts either 0.7 or 2v input which seems fine, but the output is fixed at 0.7volts which some say isnt enough to drive the power amp.

Also how are you controlling the volume? The volume control should always be done at the output to maximise the gain structure. Which presents a problem because you need a 4 channel volume control pot. Most preamps are simply two channel. If you used two preamps you would have to adjust the relative volume between tweeter and woofer each time you changed volume.

[marscoast]

Re: digital crossover implementation

I've been using a minidsp 2x8 for almost 2 years and it sounds pretty good to me. I did have some problems with digi-fp board (digital I/O) that I got with the unit. After a few rounds of talks with tech support they sent me a replacement - no problems since.

The outputs on the 2x8 are pretty flexible:
RCA Output: 2Vrms (8 dBu) in unbalanced mode
Phoenix terminal : 4Vrms (14 dBu) unbalanced OR 8Vrms (20dBu) balanced

Now multi-channel volume control... yes, it's a PIA. My solution is a 7.1 receiver with multi-channel inputs. I picked up a refurbished HK AVR for ~$350 that now serves as a 7-channel amp with ONE volume knob.

[colofan]

Re: digital crossover implementation

I have used both the DBX unit :
http://dbxpro.com/en-US/products/driverack-pa

It is a good unit though a bit limited since you can't hook up a computer and mess with the filters. It is designed as a auto setup and go. You can adjust crossover points and type of filter as well as delay times. They have pricer models where you can get the full blown computer modeling.

I also bought a unit for my 4-way system.

http://sound4us.elementfx.com/

It has more controls but not at the level of mini-dsp.

Just depends on your desire on how much DIY you want to do.

TI makes evaluation boards that you can write your own code if you want. Too much work for me i would rahter be building and designing more speaker enclosures with my time.

Way back in the day I have built from scratch based on Linkwitz filter articles a custom analog design (the 4-way replaces that). Interesting to do 20 years ago but not for me anymore.

[natehansen66]

Re: digital crossover implementation

Geddes and John Kreskovsky also use miniDSP.

I'll second the guy who said J River and a PC..... I've been doing that for a couple years and it's absolutely solid. The nice thing is you get to choose your own DAC (multichannel of course). Volume control can be done in the software without any sq degradation as long as good gain structure in maintained.

[Bob Brines]

Re: digital crossover implementation

Take a look at the nanoDIGI. It is a bit of overkill, because it is 2 x 8. Of course, that will allow a four-way stereo crossover. It avoids two issues with the miniDSP: It is digital in, SP DIF, and digital out again SP DIF. The miniDSP is analog in and has an ADC on the input. The output of the nanoDIGI SP DIF, So you will have to supply your own DAC's of whatever quality you can afford.

Bob

[ErinH]

Re: digital crossover implementation

If you want multiple channels of DSP, then the Rane RPM88 is an option. 8 channel in, 8 channel out. Again, works with consumer level input and pro level input. And as with the RPM26Z, I use the RPM88 in my home setup as well. I use the 26z for active 3-way as mentioned above, and the RPM88 controls center, surround, and sub processing.

The Rane has a separate volume controller you can use for it if you want/like the volume knob.
http://www.bhphotovideo.com/c/produc...te_Volume.html


You can download the Rane DragNet software for free and toy with it. It's not very intuitive, depending on your background, but it's quick to pick up once you get used to it.

The RPM88 used prices range anywhere from $500 (VERY rarely) to $900. There's a couple on eBay now but the price is a tad high for me. If you aren't in a rush, then keep it on your eBay watch list and you'll be able to get one for around $600 or so as they pop up at this price every couple months or so.


I've used dBx, minidsp, and behringer. I prefer the Rane for bang for buck. Spec wise (link), it's killer.

[ErinH]

Re: digital crossover implementation

if the miniDSP doesn't tickle your fancy, what about a car audio DSP? The modern ones are no slouches by ANY means. The feature LR, BW, and Variable Q type crossover filters in addition to time delay and tons of EQ.
They take low level type inputs and most will provide 4vRMS signal out unbalanced.

I use this one in my car and I've actually considered using it at home as well. A simple wall-wart for 12v adaptation and you're good.
http://www.crutchfield.com/p_975HELIXDS/Helix-DSP.html

If you wanted something like that, you could go with an authorized dealer and get a lower price or simply buy one used.