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Benefit of an electronic cross over?

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#1
I have two magneplanar 3.7i speakers and am considering adding a pair of subwoofers as the room is large and the sound seems to be weak at the low end. Although the subs I am considering have low pass filters that are adjustable (JL Fathomf112 v2 12, Rel s/5 or s/3, Rythmik F12), I wonder if there is any benefit to limiting the frequencies going to the main speakers. As such, an electronic crossover would need to be interposed between the preamp and the amp. JL audio CR-1, Pass Labs XVR-1 are some of the boxes I have seen. But I don't want to add more boxes to the audio chain if the benefit is not audible. What opinions have any of you about this?
 

RayDunzl

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#2
My Cheezewoofer Wattless subs (four now) are lazily stacked next to my mains and duplicate the low end, so no separating the 12" sealed in the speakers with the 15" ported subs.

90dB main, add first sub and adjust to 93dB, then add the second sub and adjust it to obtain 94.7dB at the listening position.

The mains are too much in the bass in this room by themselves, even with the -4dB cut on the speaker applied, so room correction cuts the trio even more on each side.

The result is lowered distortion in the bottom, 2% or less measured in a sweep, except around 50Hz where I have a room phase anomaly.

I've considered separating things with another miniDSP, maybe next year (it isn't far away today), but am pleased enough with the result right now.

Bass is distinct as to simultaneous bass sources - string bass, bass guitar, low drums, wel differentiated.

I'm not a head banger - 105dBZ peaks are generally enough. 117dBz musical peak has been measured, but that was a brief episode of "too much".

I correct for flat (to the consternation of the folks with WDD*, but the result suits me and the only other person that gets into it here.

However, he has an old active crossover that he resurrected from The Shed Where the Past Is Buried and will bring it over next week for measurement and test, so, who knows what will come of that exercise. He says it is quiet, beyond that, don't know.

upload_2016-12-31_16-47-35.png


*WDD - Wide Dispersion Disorder
 
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DonH56

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#3
I would not run the Maggies full-range. Large bass signals cause them to distort heavily and their limited excursion limits SPL down where it is really needed. I have rolled off mine since my first pair of MG-I's nearly thirty years ago. The times I have had to drive them full range I have always gone back to adding a sub and crossover, or at least rolling them off on the low end. IME/IMO it really cleans up the entire spectrum by taking the load off the panels and using a good sub.

I have used a variety and passive crossovers in the past, commercial consumer (ARC, Bryston, several less expensive that nevertheless sounded fine to me) and pro (dbx, Rane, couple of others I've forgotten), and a number of DIY versions (active and passive).

There are a myriad of crossovers available from <$100 to >$10,000 USD (the more expensive add many more features and usually include room correction and such).
  • There are inexpensive in-line versions for $10 or so available from a number of places (Amazon, Monoprice, Parts Express). I have no experience with them; I usually rolled my own when going passive.
  • miniDSP makes an inexpensive DSP-based solution, e.g. https://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4 It has a lot of giod feedback but I have not personally used one.
  • dbx makes an inexpensive professional crossover that works well and is <$200 for the two-way version (223xs). http://www.sweetwater.com/c445--dbx--PA_Crossovers I used some flavor of them for ages and until recently used a 223xs provided by a fellow WBF member. They also make more expensive DSP-based processors (DriveRack line) that can be used as crossovers (Roger Sanders currently uses a dbx unit with his ESLs).
  • Marchand Electronics ( http://www.marchandelec.com/xovers.html ) makes some good passive and active crossovers.
  • Bryston makes a nice one (be sure to get the SUB version): http://bryston.com/products/other/10B-SUB.html
  • DEQx, Trinnov, etc. offer processors that can be used as crossovers (and a whole lot more); I have no experience with them.
I have no experience with the JL or the Pass Labs. The little dbx units have been my "go to" crossovers for an inexpensive analog solution that sounds good and is easy to use.

FWIW I am running Rythmik F12's with my Maggies now. My DIY sub of ages ago was a servo sub similar to Brian's (Rythmik's) design, and Brian and I have similar day jobs, so it was a natural fit.

FWIWFM - Don
 

RayDunzl

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#4
My buddy with the crossover has Martin Logan CLS - so the same low frequencies from a panel trouble that DonH56 mentions, ameliorated with some Rythmik F12G's, but he hasn't tried the crossover yet since he just remembered he had it (or whatever).
 

RayDunzl

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#5
Is this low distortion for 95dB cheap bass?

I don't know. Straighten me out.

upload_2016-12-31_17-5-40.png
 

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DonH56

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#6
Yes, but you knew that...
 
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#7
thank you for your feedback.
@DonH56
I have looked at the minidsp but am concerned about the a/d and d/a conversion as well injecting more noise into the signal (another noisy power supply). If I want room correction, would't I be better off doing it in the pc where I play my music from? (using Dirac, acourate or something like that)

The dbx and the bryston units seem more along the line of what i need. I don't understand what the different bryston options offer tho. Specifically, what's the benefit of Linkewitz Riley and using resistor boards?
 

DonH56

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#8
The miniDSP has been used by quite a few folk who seem to like it and have not complained about noise or distortion. It does require a bit if technical acumen to program, however. Running Dirac Live from your PC would be a great solution, natch.

Linkwitz-Riley is a commonly-used crossover topology comprised of cascaded second-order Butterworth stages. In non-techie speak, it provides high roll-off (usually 24 dB/octave) and flat response across the crossover region with good time- and frequency-domain response. See e.g. https://en.wikipedia.org/wiki/Linkwitz–Riley_filter

The boards provide different crossover frequencies and slopes as well as different filter designs (Linkwitz-Riley is one). The boards create fixed filters, so no pots to get dirty or noisy, but also means you have to change them if you decide to tweak things later. And, once the pots on the dbx are set, they won't be noisy. The Bryston is a very nice unit, but at 10x the cost of the dbx, I'd try the dbx and see how you like it.

One thing (among others) that I like about Rythmik is their continuous phase control. That really helps in these situations where you need to adjust phase to account for physical and electrical changes in phase (time/distance) between the subs and mains but don't have an AVR or other room correction system to do it for you.
 

amirm

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#9
If I want room correction, would't I be better off doing it in the pc where I play my music from? (using Dirac, acourate or something like that)
You would but then the output from the computer will be multi-channel to accommodate sub output.
 
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#12
...The little dbx units have been my "go to" crossovers for an inexpensive analog solution that sounds good and is easy to use.

FWIW I am running Rythmik F12's with my Maggies now. My DIY sub of ages ago was a servo sub similar to Brian's (Rythmik's) design, and Brian and I have similar day jobs, so it was a natural fit.

FWIWFM - Don
I was looking at these analog only units but their crossover freqs are kind of limited. The venu360 has a lot more control offered. I am concerned tho about the A/D, DSP, D/A. Everybody makes a big deal out of the different DACS. And how they 'alter' the sound. I would not want to put a device in between the dac and the speakers that degrades the sound. Obviously, I am just an amateur and I do not have access to infinite hardware or money to try a bunch of stuff.

The miniDSP has been used by quite a few folk who seem to like it and have not complained about noise or distortion. It does require a bit if technical acumen to program, however. Running Dirac Live from your PC would be a great solution, natch..
but then how could I separate the bass frequencies out of the pc to send to the subs? The closest I can imagine is using a lynx22 card in the pc and using the multichannel output of acourate to do the crossover and send the appropriate frequencies to different outputs. But then the D/A is being done on the card. Not so good.


I'd try the dbx and see how you like it.

One thing (among others) that I like about Rythmik is their continuous phase control. That really helps in these situations where you need to adjust phase to account for physical and electrical changes in phase (time/distance) between the subs and mains but don't have an AVR or other room correction system to do it for you.
which dbx have you tried (and liked)? And the bit about continuous phase control- if the sub is in the back of the room, the mains need to be delayed. The phase control only delays the sub. If you get the 370PEQ amp with the F12, it has more crossover options such as high pass frequency to the mainsetc, but there is no timing adjustment for the mains.
 

Sal1950

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#13
I was looking at these analog only units but their crossover freqs are kind of limited. The venu360 has a lot more control offered. I am concerned tho about the A/D, DSP, D/A. Everybody makes a big deal out of the different DACS. And how they 'alter' the sound. I would not want to put a device in between the dac and the speakers that degrades the sound. Obviously, I am just an amateur and I do not have access to infinite hardware or money to try a bunch of stuff.
If your worried about a single AD/DA conversion take Blumleim 88 test and judge for yourself.
Poll has been closed and answer is in the posts so don't read down into the thread till done.
http://audiosciencereview.com/forum...dac-loop-vs-the-original-can-you-hear-it.448/
 

RayDunzl

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#14
What defines an "active" crossover?

Opamps?

Or digital?
 

RayDunzl

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#15
This old 1981 crossover mentioned in post #2 above:





We played with it, and decided it passes the BTN* test:

upload_2017-1-12_16-40-45.png


The rise around the cross frequency is related to a previously mysterious knob on it marked "Depth", that spreads out or bunches up the area around the cross, like this:

upload_2017-1-12_16-50-45.png


He'll use it with his Martin Logan CLS and Rythmik subs.

*Better than nothing
 
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RayDunzl

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#16
Yes, but you knew that...
Sometimes what I "know" is wrong. I'm not averse to expert opinions.

I'll take yours as an affirmation, thank you.
 

Fitzcaraldo215

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#17
What defines an "active" crossover?

Opamps?

Or digital?
Ray - the essence of active crossovers are that they work with signal at line level rather than at amplified speaker level signal. Ergo, they are powered by their own "active" power supply rather than passively crossing over amplified speaker level signal via high power level inductors, capacitors and resistors. Ergo #2, actives must always be followed by an amp, one for each divided frequency range post xover.

No, actives need not be digital, and they existed long before digital audio as purely analog designs. But, common sense and price/performance makes the choice of digital DSP a no brainer today, except among a vanishing few snooty, reactionary and elitist examples still using analog.
 

RayDunzl

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#18
Ray - the essence of active crossovers are that they work with signal at line level
A passive crossover can do that.

Resistor, inductor, capacitor.

No "active" parts. No external power.

Maybe just another case of something being misnamed.

Carry on.
 
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DonH56

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#19
@skypickle -- See post #3 in this thread. I have a dbx 223x (or 223xs, forgot if black or silver faceplate). It is a professional active analog crossover with TRS balanced I/O -- I use TRS to XLR adapters with it, going XLR into my amplifiers. I have also just gone single-ended with a TS to RCA cable, not a lot of difference that I can tell. I have little experience with Marchand but the stuff I have seen is very well-built. I have never tried a miniDSP, always meant to, but a lot of folk are happy with them. As has been noted, most people cannot hear multiple A/D/A conversions in the signal chain; most converters these days are very quiet and clean.

@RayDunzl -- Until the whole AVR "passive-biamp" scheme/scam, to me a passive crossover was just that, no active devices, a line or speaker level RLC network. The balanced versions I built usually included bifilar chokes or transformers to provide (maintain) some common-mode rejection. An active crossover was always line-level and included active devices (transistors, tubes, op-amps -- had 'em all at one time or another). DSP-based crossovers I consider active (really active ;) ). These days I would choose active, analog or DSP, to get higher-order slopes and essentially no source/load impedance interaction.
 

Fitzcaraldo215

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#20
A passive crossover can do that.

Resistor, inductor, capacitor.

No "active" parts. No external power.

Maybe just another case of something being misnamed.

Carry on.
Possibly. But, check out the parallel with passive preamps vs. active. Same difference. Passives might be theoretically capable, but without the buffering of powered, active circuitry which is more complex and sophisticated, they are not necessarily happy interfacing to any and all components or to interconnects of varying characteristics or length.

I still maintain that active or passive is simply a question of whether or not the device needs to plug into house current or not. You are overthinking it.
 
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