@rauliruegas The thing to remember is the NATURE of the bass. Planar open baffle style bass is different in terms of attack, harmonics, and decay than conventional woofers. Even if they are in sealed boxes and servo controlled. The higher you bring the crossover the greater the risk of hearing the difference in the nature of the speakers and subwoofers.
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Dear @neonknight : Even that what you posted makes sense and is what we normally think things are that you really don't know till you test it.
@mijostyn , owns the top SoundLabs and runs with subs crossing at 100hz and using a high pass filter at more or less same frequency. I f he want it he can chime here about with first hand experiences that I have too but not in my system.
Sorry, but that is not true. ESLs will move their diaphragms in an attempt to make bass and if you take a very near field measurement they would seem to be very accurate... until you move away from the speaker. Because they are dipoles there are interference effects that cause amplitude issues and wors, the longer excursions of the diaphragm Doppler distort everything else the speaker is doing. Not only this but the longer excursions severely limit headroom because the diaphragm has a very limited space to operate in, about +- 3 mm.
I cross at 100 hz because this takes all the long excursion frequencies away from the ESL increasing headroom and lowering distortion. My subwoofers are passive and use Corian layered with MDF for their enclosures. They are stiffer and heavier than any commercial 12" subwoofer. With digital bass management you can not identify the subwoofers and these are not as good as I had hoped. The next model is almost finished and will be a big improvement. I have been experimenting with subwoofers under ESLs since 1979.
Given your assessment I have to assume that either your Velodynes resonate unacceptably or there is something wrong with the Trinnov's programming. To crossover at 100 Hz you have to use a very steep slope, at least 48 dB/oct and it should be Linkwitz-Riley. I do not remember if the Trinnov can do this. All I can say was when I reviewed the Amethyst several years back I was disappointed in the flexibility of the bass management. Having said this, the only commercial subwoofers that are reasonably accurate are the Magico Q series subs. They are very expensive and HUGE. The best subwoofers otherwise are the Martin Logan Balanced Force series subs. They resonate less because the two drivers opposed each other canceling Newtonian forces. The Magicos do this also and there are two Balanced Force KEF subwoofers that are smaller than the MLs. I know you would be happier with the MLs under your ESLs. I will review the Amethyst's bass management and get back as to what I think would be the best way to set it up. If it can not due 48 dB/oct then you have to cross lower. You do not want the subwoofer getting into your midrange. At 24 dB/oct 80 Hz is pushing it. My old TacT 2.2X could do 80 dB/oct in 1 Hz increments from 20 to 320 Hz. And, you could change it on the fly. There is one simple test. Turn the main amp off and listen only to the subwoofer which are going to sound really bizarre. This is normal. You should not hear any voice coming through. If you do you either have to increase the slope, lower the crossover point or both.
@mijostyn The Amethyst can do 48 dB per octave. I have to read the manual to find that menu.
Interesting point about diaphragm excursion and unintended effects. Very reasonable points.
Next weekend I will experiment with higher crossover points. I will look at 80 and 100 Hz. I can create curves for both and select between them.
Excellent. Remember, any change you make will require taking new room control measurements. You will need to do this for both crossover points then you store both of them in presets.(I think?) This is a PITA but it is the nature of the beast and will take up the better part of a Saturday morning.
Once you have it set up. Turn up the volume and see how loud you can go before clipping. Check to see if you can hear voice coming through. You should notice a big improvement. The subwoofers should be located between the ESLs. If the subs are still obvious than the issue is with the subwoofers. Make sure all the subs extra functions are bypassed. If you can't bypass the low pass filter in the subs turn them all the way up. By 1990 or so I had become so frustrated with commercial subwoofers I started making them myself and I am on the 4th version. The problem is that is is extremely hard to keep subwoofer enclosures from becoming musical instruments. Turn the volume up with a bass heavy piece and put you hand on a subwoofer enclosure. It will be vibrating more or less at different locations. It will also be shaking a little in reaction to the speaker cones movement. With the ideal enclosure you should feel absolutely nothing, no shaking and no resonance. It turns out this is a very tall order. Mass alone will not stop it although it helps. Using opposing drivers to cancel forces helps a lot but is not enough. The enclosure has to be so stiff that any resonance is at a frequency way above the subs passband so the driver can not excite it. This is a lot tougher than you would suspect. Magico does it by using a heavily braced Aluminum enclosure. Not very elegant, but it works.
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