Welcome! Need support, you got it. Or share your ideas and experiences.
I took your recommendation seriously @Roger Gustavsson. Rather then go to all the expense of upgrading the existing crossovers I will go active. I ordered a Nelson Pass designed DIY active crossover. He calls it the DIY active 6-24.
It is a 2-way complete stereo crossover which has 6, 12, 18 and
24 dB/octave slopes and filter poles independently adjustable over a
6:1 frequency range.n You are probably familiar with it.
I built one of Wayne Colburn's Pass Pearl II phono preamplifiers and am very pleased with the results so I will have a go at this.
I may start with a DBX Venu360 to narrow down where to start with the 6-24.
I am looking for suggestions for crossover freqs and slopes for bass and mid. It will be a two-way active for the mid-bass and a passive for the mid-tweeter. The mids will be B&G RD75's.
Do you have a way match the output levels of the Maggie bass panels and the B&G RD75's ?
There are pots in the active crossover to adjust levels. Once levels have been establish you can replace the pots with resistors.
As the power supply is single ended, I think there must be DC-blocking capacitors on in- and outputs. I häve the matched set of J113 and resistors.
All kinds of slope with 6-12-18-34 dB/octave can be set. The levels of the low and high pass can also be set, there is no gain above unity.
I have to attenuate the GRS NEO8's I am using by quite a lot to level match them to the Maggie panels and OB/Dipole subs.
Don't know how efficient the RD75's are though.
The RD's don't have neodynium magnets like the Neo X's.
Here is the sensitivity chart for the RD75's.
This is at 1 meter. My listening position is at 4.5 meters.
Great idea, Steve - this will make your T-IVas sound a lot better. A further improvement could probably be had by redeveloping your mid/ribbon passive XOs with better-quality components.
I suggest you stick with the stock 18dB bass LP and 12dB mid HP slopes ... but with modified roll-off frequencies:
* bass LP @260Hz
* mid HP @530Hz.
1. you will need to put some gain on the mid HP output of the active XO
2. and use an attenuating resistor on the ribbon ... say, 1.5 ohms.
Well, I have two kits of that First Watt/Pass 6-24 crossover, still unused. What I do not like is the electrolytic capacitors on in- and output, at least not on the high frequency section. I recommend replacing the trimpots with resistors when the final crossover points are set. Some audiodesigners like to keep the series resistance below 15 kOhm, to achieve lower noise. That will force you to increase the values of the capacitors in some cases. As this a fully adjustable crossover, there is room for experimentation.
There was an interesting story on the BG RD75 many years ago:
Get busy and build one @Roger Gustavsson so you can clue me in. LOL
Do you prefer another type of capacitor to electrolytic or no capacitor at all?
Are you going to use 2SK170 or LSK170 JFET's instead of J113's? (The parts list says J114 but Nelson's notes say J113.)
I ordered a kit.
Electrolytics in series with the signal is not what I want, at least not if it to tranfer high frequency signals. I think they cannot be dismissed as the power supply is single ended. It is possible to use film capacitors, maybe like Wima MKS 02 (0.68µF, if that is enough) at the inputs and with some tricks Wima MKS 2 (10µF) at the outputs? My boards came with J113 and bias resistors selected for them, I will not use 2SK170 or LSK170. Well, I have not even decided to use this crossover yet.
Somewhere along the way most recorded music has probably passed through some electrolytic coupling capacitors. :) In fact, probably quite a few. :)
Post a Message!
This post is made possible by the generous support of people like you and our sponsors: