Hello
I have a FAST setup with a set of FF85WK's...right now I am using a minidsp between my pre and amps set up for 250hz...but I was wondering if I could just use a simple cap setup on the Fostex's instead??
This would be used for when I go back to my integrated (preamp outputs but no main in's for the loop)...
I would want them cut off below 250hz like I have it now...thinking a 50-70uF cap should do the trick...yes no??
Thanks!!!
I have a FAST setup with a set of FF85WK's...right now I am using a minidsp between my pre and amps set up for 250hz...but I was wondering if I could just use a simple cap setup on the Fostex's instead??
This would be used for when I go back to my integrated (preamp outputs but no main in's for the loop)...
I would want them cut off below 250hz like I have it now...thinking a 50-70uF cap should do the trick...yes no??
Thanks!!!
What box is it in? There's a very good chance there's a large impedance peak around 100hz give or take. So, no, a single cap won't work. You'll want an LCR impedance flattening circuit or go second order.
If the impedance peak is very mild, you could possibly get away with it.
Oh and ya, the cost won't be cheap.
If the impedance peak is very mild, you could possibly get away with it.
Oh and ya, the cost won't be cheap.
I am doing that now but I would like to bring back in my Electrocompaniet amp...unfortunately it only has preamp outputs...
That and I was considering a tube build...a Get*Set*Go or a Budgie or something like...maybe with those I can do a preamp-out\main-in setup to be used with the minidsp...
Right now I brought out my little ASL EL84 pre along with my Virtue Audio tripath amp to run the 85's...I have a Parasound for the bottom end that does a good enough job...
All that gets to be too much cabling and gear...would like to simplify things a bit!!
That and I was considering a tube build...a Get*Set*Go or a Budgie or something like...maybe with those I can do a preamp-out\main-in setup to be used with the minidsp...
Right now I brought out my little ASL EL84 pre along with my Virtue Audio tripath amp to run the 85's...I have a Parasound for the bottom end that does a good enough job...
All that gets to be too much cabling and gear...would like to simplify things a bit!!
Passive is certainly simpler. But costly. What woofer are you using? I've done a few passive FASTs and they have all ended up in the same ball park of second order on both drivers with the polarity reversed. About 4mH and 50uF on the woofer and 30uF and 3mH on the full ranger. Or there abouts.
where have I heard that before?
while I've not done it myself, I understand 2nd order are achievable with PLLXO
xrk971, He's trying to get away from pre-amp (active) XO'ers. Passive is the only way for him to use the amp he's interested in using.
I've never done analog active (how I called it before hearing of PLLXO) but I've done it with DSP active. With DSP I usually shoot for 4th order. But I understand a lot of guys like to stay low order, even first order. Which begs the question, why isn't second order preferred to first order. You have more phase roll, but it's actually in phase while the first order XO is not. (Just a side thought).
I've never done analog active (how I called it before hearing of PLLXO) but I've done it with DSP active. With DSP I usually shoot for 4th order. But I understand a lot of guys like to stay low order, even first order. Which begs the question, why isn't second order preferred to first order. You have more phase roll, but it's actually in phase while the first order XO is not. (Just a side thought).
where have I heard that before?
while I've not done it myself, I understand 2nd order are achievable with PLLXO
I have never done it before either but looking into it seriously. I just calculated a 2.5k crossover for a bi amp with 60 kohm impedance. I modeled it in Tina (spice) and it looks pretty good. Here is link to analysis and gain plots. Yes, -12 dB 2nd order is achievable but you have -6dB hit from preamp outputs. Ok if you drive with headphone line out.
http://www.diyaudio.com/forums/class-d/237086-tpa3116d2-amp-39.html#post3646203
I priced the parts on Digikey at $4 without pots and $8 with two pots. The amps will cost $34 a pair.
Last edited:
Tux,
This is passive - no op amps involved. It just sits between preamp and power amp. See my analysis on previous post link.
Do you think?? I don't have the schematics but I would like to hear what you're thoughts are!!
That's active IMO. The XO actively manipulates the frequency response. After the amps, it passively does the job.
Actually I'm only trying to get away from active on the Fostex side...or the high pass side...for the moment
I still would like to use the minidsp for the bottom end (SEAS CA22RNX's)...this way I can adjust levels easier to blend in better...
I was thinking it would be pretty simple...a first order cap...now possibly a second order circuit in the range of a 40uF\10mH from my calcs...or a line level which I have no idea how to calculate and if those values need to change if that amp changes...
Stupid reasons...my pre only has one input...the E is a nice amp that works well with the Fostex's...I could always buy a different preamp
Basically you would trace the circuit (you already have a pre-out to get you a starting point), cut the trace on the board, connect the power amp side to a set of RCAs.
A schema might help, board layout would make things easier.
dave
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.