This is Geert Meddens' Contrapunct dipole subwoofer crossover.
http://www.meddens.eu/audio/images/sub63_scheme_v2.jpg
http://www.meddens.eu/audio/images/sub63_scheme_v2.jpg
Geert Meddens circuit has a nice twist since it is a Chebyshev filter in the HP for the Subwoofer with approx 3 dB gain around 20 Hz before it falls of steeper than usual. I think the crossower frequency is -3dB at 16 Hz.
So if you go analogue this is a nice alternative to MT-Audio.
In the digital domain you can do lot of magic of course.
So if you go analogue this is a nice alternative to MT-Audio.
In the digital domain you can do lot of magic of course.
Even though I always say a system today without a DSP is just plain crazy.... at the very least, you could use something as easily adjusted as Behringer DCX2496 to mock-up by hearing tests the slopes and points, and delays, and EQ, and......
and then attempt by duplication to buy and certify and test (and then expensively try to modify and re-modify) the components in your final system.*
B.
*of just leave the DSP in place
This makes no sense to me: "high pass in the subwoofer"? To pass low frequencies to the subs need a low-pass filter.
Open baffle needs 6dB/Octave boost: if you crossover at 100 then 6dB boost means four times the power at 50 Hz. Eight times the power at 25 Hz. Sixteen times the power at 12Hz.
I do not see why the uneven response of Chebyshev filters are unpopular in LF audio. Speaker impedance varies with a lot with frequency, as does Chebychev filters.
The high pass filter for the dipole subwoofer is a susonic filter.
You need to limit the energy in the very low octave to protect the subwoofer.
You also introduce a lot of distortion since as you already realized, the amount of power that is feed to the subwoofer close to 20Hz is huge.
You need to limit the energy in the very low octave to protect the subwoofer.
You also introduce a lot of distortion since as you already realized, the amount of power that is feed to the subwoofer close to 20Hz is huge.
I know this post is old, but it's what comes up in a search for MT Audio Design XO-2001 now that the company website is gone. Does anyone have the specs on the power supply for the MT Audio Design XO-2001 crossover? Someone offered me one without a power supply. I just acquired Gradient sub-woofers to go with my Quad ESL63s and I'm running them with a Behringer digital crossover. It seems like the MT crossover and the Gradient box are more elegant solutions. The Behringer requires 4 balanced output cables or adapters. Thanks if anyone is listening.
All Op-Amps is fed by +/- 12 volts from 7812/7912 regulators, so you need to feed the voltage regulators with +/- 18 volts.
The current is very low 12 OpAmps in total and each taking maximum 8mA gives you approx 100mA.
So 300mA should be "high end extra super margin".
The current is very low 12 OpAmps in total and each taking maximum 8mA gives you approx 100mA.
So 300mA should be "high end extra super margin".
Thank you very much! So something like this? Seems like higher voltage brings higher amps along in generic wall warts.
- US Adapter,Input Voltage : AC 100-240V,50-60Hz (Worldwide AC Input)
- Output : 18V 1.5A/1500mA Max (Also Compatible with 1000mA or lower device)
I recently acquired the Gradient subs to add to my Quads and it was supplied with a Behringer DCX2496 instead of any other crossover. By a stroke of luck (I think) somehow I'm awaiting shipment of an original Gradient box AND an MT -XO2001. I thought the Quad/Gradient sounded spectacular when set up with a crossover of 109hz (it skips 110hz). I tried some higher crossovers and the sound got muddier as it went higher. I know that there's a 'cult of Walker' that trusts the original Quad designs over improvements so I think I'll trust that crossover of 100-110 for now. Didn't the Gradients get the Quad stamp of approval?
Hooray. Pretty simple, eh.
No other sensible way to manage a sub with adequately steep slopes to keep low notes out of the mid-range speakers.
B.
My MT Audio Design XO2001 crossover just came back from being tested and checked out at a repair shop. The technician discovered a detached ground wire that was causing hum, and now it's operating properly. I have to say that compared to the Behringer crossover, the sound in the highs is clearer and sounds more like the Quads without the subs. Setting the bass level will take some experimentation, but it's soooooo easy to adjust.
Late to the party, but I recently got a pair of Gradient subs sans the xover filter unit.
I tried the MT website for info on the XO2002 but the site appears down/closed.
Anybody can help me out with frequency response graphs of the filter and/or schematics?
Jan
I tried the MT website for info on the XO2002 but the site appears down/closed.
Anybody can help me out with frequency response graphs of the filter and/or schematics?
Jan
Jan
You don’t want the original Gradient crossover. It was 3rd order in the bass and 2nd order in the treble, a real mess. Crossover frequency was 115Hz. What you want is described above: 4th order Linkwitz-Riley at 115Hz or wherever you like, plus a baffle correction. Easily done with a MiniDSP.
I do have a Gradient crossover if anyone wants it.
You don’t want the original Gradient crossover. It was 3rd order in the bass and 2nd order in the treble, a real mess. Crossover frequency was 115Hz. What you want is described above: 4th order Linkwitz-Riley at 115Hz or wherever you like, plus a baffle correction. Easily done with a MiniDSP.
I do have a Gradient crossover if anyone wants it.
I felt the Quad ESL 63 had a bit too high Q resonant frequency of around 50 Hz, so I built a sealed subwoofer under each speaker with a 10" SLS peerless driver with an F3 at ~50Hz. I set things up initially with a 2nd order adjustable crossover and listening by ear, and balancing volume with a measurement microphone.
I felt that the range of 150 Hz was highest frequency for good enough integration and a large bass improvement and dynamics, and 100 Hz was the lowest frequency to get real benefits in for volume / dynamics while better integration. So a range of half an octave for a good compromise.
I settled on 120 Hz 4th order crossover to sealed subs for my ESL63. I am very happy with the combination.
If I was to do it again I would have learnt from the KEF 104/2 I recently repaired, and gone for two 8" drivers again in a sealed enclosure on opposite sides for the subwoofer, connected with steel rods to avoid exciting resonances outside the speaker enclosure.
I might one day experiment with a Ripol/Dipole bass but as I do like loud bass heavy music on occasion, and dont have space for Electrostatics and Dipoles and a subwoofer as well, I am not in a hurry.
I felt that the range of 150 Hz was highest frequency for good enough integration and a large bass improvement and dynamics, and 100 Hz was the lowest frequency to get real benefits in for volume / dynamics while better integration. So a range of half an octave for a good compromise.
I settled on 120 Hz 4th order crossover to sealed subs for my ESL63. I am very happy with the combination.
If I was to do it again I would have learnt from the KEF 104/2 I recently repaired, and gone for two 8" drivers again in a sealed enclosure on opposite sides for the subwoofer, connected with steel rods to avoid exciting resonances outside the speaker enclosure.
I might one day experiment with a Ripol/Dipole bass but as I do like loud bass heavy music on occasion, and dont have space for Electrostatics and Dipoles and a subwoofer as well, I am not in a hurry.
MTAudio also have an all pass filter with a potentiometer, helping you to get perfect phase integration between woofer and ESL (X model)
The way it is done is like follows.
Play a 100Hz tone in one channel, reverse the polarity of the sub now you shall adjust the level and the phase until you hear a minimum of sound. You will get a cancellation of the sound when adjusted right. Place your head or microphone close to the listening position. When you move your head up and down you will hear a difference of sound pressure.
Now switch back the polarity on the subwoofer and you are ready to go.
Then you can do some fine tuning after your taste (increasing the bass maybe).
The way it is done is like follows.
Play a 100Hz tone in one channel, reverse the polarity of the sub now you shall adjust the level and the phase until you hear a minimum of sound. You will get a cancellation of the sound when adjusted right. Place your head or microphone close to the listening position. When you move your head up and down you will hear a difference of sound pressure.
Now switch back the polarity on the subwoofer and you are ready to go.
Then you can do some fine tuning after your taste (increasing the bass maybe).