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I am not completely thrilled with TwoGoodEars new crossover.

http://vinylsavor.blogspot.com/2012/01/making-of-line-level-crossover.html

First of all , Stephano has a preamp with tube out stage.  The guy in his post says that the line stage has low output impedance but I did not see the line-stages with single out tube to have output impedance low enough to drive 4 passive filters, 100-300R is not low enough, at least if Stephano goes for full ULF and very peaky about getting max dynamics.

The Stephano crossover as I hope is active and it has a buffer stage after filters. So, the filters are passive with buffers. This is kosher but the question is what the buffers are? The quality of the buffers is VERY important in this situation but the best would be not to have the active buffers and to have the crossovers line-level passive. For sure in that case the filter shall sit at the amp input – so bye-bye the sexy box with 4 filters and bye-bye the internet pictures. If Stephano crossover has no buffer stage after filters (and I do not see it on the picture) then how they regulate 12dB gain after the filters. If they do it with the rotary switches that switch the autoformers taps then it is possible but I personally do not buy it. I had a lot of debates in past with people about the autoformer volume attenuation and I am not exactly a huge fun of them. Yes, they can attenuate but they do not drive load as good as other methods. If they use the autoformer attenuation then the filters drive the cable to power amp via the autoformer – this is very far from optimum situation in my view.

What I would like to see, from a perspective of ultimate organization, is the very same filters but sitting right at the Stephano’s power amp imputes, or even preferably in the power amps. There are absolutely no needs for the filter to drive any load and there is no need to be in a separate centralized box.

From a larger perspective I am not sure if the line-level filtration will be reasonably in a long run in Stephano’s case. He use Goto drivers that have notoriously low power handling and there are a lot of people out there who did burn out Gotos, particularly HF and MF. With SS, direct-coupled amps that Stephano uses and line-level filtration the vulnerable Goto drivers will beleft with no protection at all. Stephano has to be VERY careful to use his playback in this configuration and I do not know if it will be practicable.

Anyhow, they are the thoughts at the top of my head. BTW, pay attention what they did – they model the filters via digital crossovers and then replace them with analog filters. This is right direction to go. For sure to change anything from this point will be a main pain in ass but it comes with the territory.

My main interest in the whole project is to see how they implement the MF high-pass filter. I have a feeling that they use a cap but I would like do not see a cap in there. I question the need to use the low-pass filter on the MF channel. Why would one need it and why we do not let the MF to decay naturally? I do not argue this as it would need to know the character of Goto MF driver at very top but I wonder of Goto MF has any own problem at 10-12K the force Stephano to roll off the driver with coil and do not let it to roll off naturally. Stephano uses long Goto MF horns hat do the HF roll off, so why he need to an electrical roll off? For sure I would like to see what they did with HF high-pass filter, is it C filter or RL filter? I hope it is RL but then what base impedance the use?

Anyhow, it is a good project but I might be not the “perfect” project from APPLIED perspective.

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