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This is very interesting subject.

I expect that tghe new Midbass horns will have somewhere 108dB sensitively anechoicly.  The driver is 99dB and the hyperbolic curve has much more EQ then Tractrix and that is more important the EQ that work much closer to the horn rate (if the horn is properly designed). So, I hope the horns will gain approximately 8dB-9dB. Then they get something from the room at Midbass region. Would it be another 8 db up or doe no one can say now. so, if everything  goes as I planed then the new Midbass channels will have sensitivity as the rest of Macondo. Now, how to drive the midbass?

My initial sentiment was to use the current Melquiades bass Channels. It will have most possible enough gain and power – a full 6C33C at 50W of plate dissipation.  I have this amp in my 6-CH assembly and then why do not use it? Sure I would need to modify the crossover and it is VERY comfortable to do. Take a look at the Melquiades bass (channel A on the top of the circuit)

http://www.romythecat.com/Site_Images/6-Chennal_Melquiades_DSET_Amplifier_Rev3.jpg

Currently it has just one cap to ground. Ironically it is very sophisticated crossover. A cap to ground can write low-pass filter only after a resistor. The resistor 30K in this configuration serves a combined duty:

1)     Maintain the input impedance for the bass channel

2)     Serves as base resistance for the filter

3)     Generate bias offset for the driver tube

Currently it runs 78Hz first order. It is not a big deal to move it up. I hope that I will be able to use the first order in there with Midbass Channel but it most likely will not be so. If I need to go in there with higher order filter than it will be so. Then there is a subject of the high pass filter. I know that people do not do it and no one talk about it but I also know that people are deaf Morons – I am not. As I told many times the un-used bass mast be removed from LF horn. What is the point to make the driver cone to excurt more than the horn’s mouth can pass? So, most likely the channel will have some kind of 25-35Hz filter, just under the horn’s natural roll off. In Melquiades’ case it will be very easy by changing capacitor between the stages – a perfect spot for high-path filter.

Still, there is something that make me feel “not perfect” for this channel when I think about the Melquiades bass channels. This is primary due to the current output transformer that I use in Melquiades for bass. The Melquiades bass channels were design to use with open-bottom type LF. It has enormous transformer with ultra low DCR and huge inductance. It has the most insane bass transformer you ever see for 6C33C. It has 7.5Hz frequency response. Mind you there are zillion idiots out there who claim that their not DSET output transformers work at 2Hz or 10Hz. This is all BS as none of them does measurement at full power. My persistent position is that any frequency response with OPT MUST be quoted only at full power. So, the Melquiades bass channels have now 7.5Hz  at 22W and gaped up to 450mA – you can imagine the construction of this transformer.  This transformer was one of the most important contributor to the truly pronominal bass I got in the old room.

Now, the funny thing is that this pronominal transformer might not be the best bet to drive my midbass horns. Here are the things that I have problems with: fixes ratio, use of M6 steel. I would like to have more flexibility with loading the new Midbass Channel and I would like to have much faster core. I guess I would need to get another much smaller transformer for the Melquiades bass channels….

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