[ekovalsky]

I want to bypass the passive high pass filter and L-pad on the planar magnetic drivers.  From my interpretation of the crossover layout, I need to remove the wire connecting the (+) binding post to the capacitor block and replace with the wire coming from the low pass filter coil (currently attached to the  output flag of the L-pad).  It looks like the ground wire coming from the drivers already goes directly to the binding post, after a pit stop on the GND flag of the L-pad.

Big B or John C or anyone else ... is this correct ?  If so it should be easy to make the modification and also to reverse.

High pass filter will be implemented via the TacT RCS, which will also perform the attenuation now done by the L-pad.  I will continue to use the passive 1st order low pass filter on the planars, along with the 2nd order high pass on the  tweeter -- at least until I get another amp.

Reason for doing this -- I have noticed a big sonic improvement when moving the bass-mid crossover frequency up to 275hz from 166hz (or whatever the factory setting is) and changing to 4th order slopes.  So I want the 2nd order factory crossover out of the way.   I need to attenuate the mid/high output to match the bass section, and might as well have the TacT do that (since that is what it does best) instead of the L-pad.

[JoshK]

Here is an idea I have for my RM40's that I will share with you and any others.  Take it for what it is worth.   I am looking to install an 8 pole speakon connector in the back of my cabinet near the binding posts.  This will create one sealed up hole in the cabinet that wasn't there before but very simple mod to do and easy to make it look professional.

With the 8 pole speakon in place all driver circuits can be connected to the speakon directly and then move the entire crossover circuit outside of the speaker cabinet to a nice enclosure (probably make it out of cherry wood or veneered to match speakers), think Tyler Acoustics outboard passive networks.  The crossover network with have binding posts on the input and then a hardwired cable cluster with an 8 pole matching speakon (female) connector that will attach to the cabinet.  Actually in my case since I do the cable construction myself, I will likely make the input to the crossover box an 8 pole speakon itself too so that going fully active is as easy and removing the intermittantly connected passive network and hooking up appropriate active xo and amps to the corresponding cable.  

Anyway, something to think about and wouldn't be very difficult to do.

[John Casler]

 Big B or John C or anyone else ... is this correct ? If so it should be easy to make the modification and also to reverse. ...

That is beyond my scope.  Big B, will have to "instruct" on mods, especially to the circuitry.

[ekovalsky]

Well, I didn't wait for the professor's words of advice, but yes what I described did the trick.  Took about 15 minutes per side to do.



I re-configured the TacT with crossover set at 24dB/octave @ 240hz for high pass to mid and low pass to bass.  Didn't have much time to listen after remeasuring frequency response and delays but initial impressions are very favorable.  The passive low pass to the mids and high pass to the tweeter are still being used.  

This was easy to do and, perhaps more important, easy to reverse.  Tyson's idea is very good, I wish all speakers had binding posts connecting directly to the drivers with the passive network in an external enclosure -- that provides the maximum flexibility.

[Bingenito]

I use speakons in my arrays and might suggest that you consider 2- 4 pole connectors. Trying to fit a heavy gauge wire in the strain relief for an 8 pole could be challenging.

For example my subs are wired with shotgun runs of Canare 4s11 which takes up 1 4 pole. The other 4 pole is a biwire setup for ribbons and mid-bass.

Just something to think about. The speakons are very good connectors and they keep the look clean so you do not have 12 wires hanging off the back of the speaker.

[woodsyi]

Ekovalsky,

I use an active anolog crossover, and I low pass woofers at 300 Hz and 200Hz highpass for the ribbons at 24 dB/octave on my RM40.  I sometimes want to bring in more midwoofer for better integration (vocal music) but can't do it using 4th order.  With TacT, can you try setting the woofers with 2nd or 3rd order slope and set it to roll off around 500 Hz and correct for phase? On RM40s I understand the mega woofer rolls off around 100Hz and mid woofer around 600 Hz.  I think Brian's passive does this but active biamping makes ribbons much clearer and purer and I don't want to give that up.

[ekovalsky]

Ekovalsky,

I use an active anolog crossover, and I low pass woofers at 300 Hz and 200Hz highpass for the ribbons at 24 dB/octave on my RM40.  I sometimes want to bring in more midwoofer for better integration (vocal music) but can't do it using 4th order.  With TacT, can you try setting the woofers with 2nd or 3rd order slope and set it to roll off around 500 Hz and correct for phase? On RM40s I understand the mega woofer rolls off around 100Hz and mid woofer around 600 Hz.  I think Brian's passive does  ...

Woodsyi,

After some experimentation, the best sound I have achieved is with a 24dB/octave low pass filter on the bass at 300hz and 36dB/octave high pass filter on the midrange at 250hz.  The 10" woofer of the RM/X (Misco OC10W-A, probably the same unit in the RM-40) starts dropping off naturally above 350hz.  Don't expect much from it at 500hz.

I hear absolutely no ringing of the planar drivers with the steep crossover slope.  In fact, relieved of an octave of extension on the bottom they sound more dynamic and faster.  And more transparent with the passive parts and L-pad out of circuit.  The sacrifice I make is ultimate volume, since the TacT is performing a lot of attenuation of the midrange, and to a lesser degree the treble, to match sensitivity of the woofer section.  But since I don't listen at stupid levels (like I heard last year in the VMPS room at CES) , this is a non-issue for me.  I still have plenty of headroom at levels I consider to be very loud.  And because of the clever design of the TacT -- using 24 bit shifting and output level control via rail voltage manipulation -- no resolution is lost.

Before having the TacT I never realized how important time delay is.   I am using a 1.34 msec delay on the closer mid/treble, 0.9 msec delay on closer bass, and 0.42 - 0.44 msec delays between the bass and mid/treble.  With the delays set correctly, and the channel balance perfectly set at ALL frequencies with the TacT, the speakers completely disappear into a huge soundstage with razor sharp imaging and the bass just sounds right.  With the delays improperly set the bass becomes more "one note" and sounds disjointed from the rest of the music.  

My room layout is below, I have separate TacT presets (correction & delays) for each chair.  As you can see each listening position is off axis from each speaker by the same amount.  Speakers themselves are symmetric within the room, and the room itself is sealed and symmetric both in dimensions and room treatments.  Obviously one speaker is a bit closer to each listening position, hence the need for L/R delays.  The delay between the bass and mid/treble section on each side is related to physical distances separating the drivers and also the remaining passive crossover elements (coil on the mids and 2nd order high pass on the tweeter).

[woodsyi]

Ekovalsky,

Thanks for the feed back.  I have been thinking of raising the HP on the ribbons, but unlike your DSP unit I have to order a frequency module.   I envy the phase correction capability of TacT and DEQX, but I am not giving up on my 2000 + vinyls.  I will do the best I can do with room treatment, speaker placement and using quality analog equipment to get the best sound for me.  I may periodically ask you for an opinion on x-over settings.  Thanks again.

[ekovalsky]

Ekovalsky,

Thanks for the feed back.  I have been thinking of raising the HP on the ribbons, but unlike your DSP unit I have to order a frequency module.   I envy the phase correction capability of TacT and DEQX, but I am not giving up on my 2000 + vinyls.  I will do the best I can do with room treatment, speaker placement and using quality analog equipment to get the best sound for me.  I may periodically ask you for an opinion on x-over settings.  Thanks again.

Woodsyi,

It takes about 30 seconds to program new crossover settings, so if you want me to test a new combination let me know.

The TacT comes with a large number of crossover files, 1st through 10th order up to 385hz or so at 5hz intervals.  I also have a little program that can generate new files for any frequency or slope, i.e 84dB/octave @ 257hz.  Pretty neat!

[JoshK]

No offense woodsyi but I think you are making too much of the extra A/D and D/A conversion.  Yes it isn't theoretically perfect but from what I have heard before with it being done the downside can be totally worth the upshot of better integration, etc.

[woodsyi]

Josh,

No offense taken.  What I have read on this forum so far have been from DSP users who are using digital source only -- even converting to digital amps to stay in the digital domain as long as possible.  Until I hear from more people who have been using tubed pre and tubed amps with TT set up who have converted to DSP processing, I will stay put.  Please do post all your findings.  I am learning a lot from the posts.

Another thing is I need to get my room set up (I haven't implemented all of Ethans traps yet) and tested before I can make a fair assessment of where I am and where I want to go with my audio needs!

[James Romeyn]

Eric
Consistent with you preferring to move the RMX bass-mid XO up from 166 to 280Hz: my three front RM30Cs, two rear Dipole Surrounds & Sunfire True Subwoofer Sig EQ sounds far better with all satellite spkr channels high-pass crossed at about 80Hz (vs. fullrange).  My speculation is that the RM30Cs 6.5s & even the planar-magnetic mids are stressed less, equalling lower THD & better sound.  

The XO is in the preamp-processor, not increasing the conversion processes.  The HP XO on the satellite channels also allows greater effect of the digital room EQ in the subwoofer.