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In Reply to: RE: Foil Project for IIIa's posted by computerman on February 01, 2012 at 18:14:33
I am sure that between Davy and myself and Neolith and DR we can help you with PLLXO calculations and fit your amps with what you need.
Follow Ups:
Satie and everyone. It is about that time to begin constructing the PLLXO. I was wondering a couple of things. How do I determine the XO points? How many binding posts do I need for the XO box? I am purchasing 3 surface mount binding posts for each speaker which will be wired directly; one to the tweeter, one to the mids and one to the bass with 12 AWG hookup wire. That way I can connect directly to each if necessary. I thought I would connect to these from the PLLXO in the box. Remember we are going to incorporate the 1-D's into the mix. Any help would sure be appreciated. Thanks!!
There seems to be a misunderstanding here, the PLLXO is at line level between the preamp and the amp, parallel to your active XO.
The passive XO components for speaker level go between the amps and the speakers.
The XO freq. are given in Neolith's spreadsheet for original XO slopes and corner freq I would suggest you start with balancing the 3a's with your active XO and 3 amps connecting directly to the individual drivers. Set the XO for 500hz bass-mid, and 2.5 or 3khz mid treble - for starters, measure and adjust levels to get a flat FR and then tune to favor your ear. You will need to shift the XO points around and listen to each driver alone too so you can decide which driver you want to cover which portion of the freq spectrum, you may not want to repeat the magnepan choices.
You can hook up your T-1D panels instead of the 3a bass panels since that is what you had in mind.
You need to have an idea of what placement you want based on prior experience with the T-1D..
Satie - I do understand that the PLLXO goes between the amps and the speakers. I will have a good sized XO box on the back of each speaker. What I was thinking of doing was to put the passive XO in the box. If I am using the PLLXO for the mids and tweeters, and using the active TDM for the bass panels on the 1-D's, then I would need two binding posts for each IIIa panel (plus and minus) on the XO box going in and two for each panel going out from the PLLXO to the surface mount posts on the IIIa. The surface mount posts would be connected to each panel via 12 gauge hookup wire. As I would need a direct connection to determine the XO points, and I may want to use the Behringer in the future, I would have the connections to do so. I am assuming that I am going to use the TDM XO for the bass panels, and the PLLXO for the mids and tweeter. Does all this sound correct? Do you have any alternative suggestions?
Another question I have is on the back of the Rotel 1077 amp, there is one RCA connecter for each input rather than two. Do they use a special cable? I have never seen an amp like this before. Thanks Again!!
You got it upside down.
The PLLXO does NOT go between amp and speakers.
The PLLXO is at line level (preamp level) and goes in between the preamps and the power amp.
The power amps connect directly to the speaker drivers via the binding posts. The whole idea of active XO/multiamping is to get rid of the inductors and capacitors between the amps and the speaker drivers.
The active XO and the PLLXO run in parallel from the preamp output. You either have an extra output pair of RCAs or you use a Y splitter. The PLLXO runs in parallel to the active XO.
At this point, you want to use only the active XO to determine XO points
- run the treble out from your XO to the amps driving the IIIa tweeter
- the midrange output from your XO to the amps driving the IIIa midrange
- the bass out from the XO to the big amps for the T-1d bass/midbass panels.
You don't use the tweeter panel from the T-1d.
The Rotel is a multichannel amp, it has one RCA per channel, a stereo amp has 2 channels and the same 1 RCA per channel. There is a + and - post for each channel output on the Rotel.
Remember to check that the Rotel can actually drive your 2 ohm tweeter - otherwise use the 1 ohm resistor.
Once you have determined where you want your XO points to be, we can work out the PLLXO that will work for that.
send me an email and we can discuss the details of your setup without hogging the forum's bandwidth.
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