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IIIa Frankenpan Active X-Over points?

74.76.6.170

computerman

I did some searching for crossover points for my "Frankenpan" IIIa maggies. The panels were recently custom rebuilt by Magenpan using the same foil for the mids that they use on their 20.7's. At lest that is what they told me. It was recommended by Roger. It is foil, 0.001"x0.1. They did a beautiful job replacing all mylar. They look like new. I have been experimenting with levels and crossover points, based on what I have found from my search and what Satie recommended in my previous post. I am a bit puzzled by one set of crossover points that were recommended. They are as follows:

In Reply to: IIIA ideal crossover points triamping active posted by Mike D on May 31, 2012 at 11:20:47:

Hi Mike,

Yes, I am still using those "crossover points" but my slopes are not 24dB.

But I am keen to try what I think Satie uses, and a Pom called "Davy", which is (all -3dB points):
* 18dB LP @ 240Hz on the bass
* 6dB HP @ 550Hz on the mid
* 6dB LP @ 3,800Hz on the mid, and
* 6dB HP @ 5,400Hz for the ribbon.

Could someone please further explain how I could achieve these settings? My IIIa's are tri-amped. I am using a DCX2496 for the active crossover, so I believe these settings, are achievable, but not quite sure how. Could someone possibly elaborate on the above? Right now my settings are as follows:
I am using 40Hz on the bass end, 337 between bass and mid, 2.68 between mid and tweeter and 20.0 at the high end. All are L-R with 24db slope. How would I change my settings to achieve the above? I would love to experiment. The beauty of the DCX is that it can be done at low volume in real time. Once one is satisfied they are easy to save. Once i have the crossover points to my liking, I would love to experiment with the delay and eq settings. I may in the future, build some passive crossovers based on the best configuration. I also have some Tympani 1-D's that will be in the picture after I move which will be in about a month. In the interim, I would love to get the IIIa's tweaked and enjoy them for the month, plus break them in. I am impressed by the foil mids. They are crisp and clear. Any comments or advice would be greatly appreciated.

Follow Ups:

RE: IIIa Frankenpan Active X-Over points? - Tidycat1 22:57:40 03/05/15 (0)
Using 6db/oct and 24db/octave slopes yield the least amount of phase shift.12 and 18 db slopes will require experimenting with the polarity of the driver.
You are looking for an averaged flat frequency response.The crossover point may not be the same between two drivers.
My conversations with Kent@Pass Labs has been instructional,regarding the use of the XVR-1.
My system uses 6db HP at 107HZ and 24db LP at 75Hz.Using the high Q and the adjustability of this function has been educational.Off point-my apologies,but wasn't the XVR-1 designed for use with the Maggies??
Tom:cat
RE: IIIa Frankenpan Active X-Over points? - neolith 18:54:43 02/23/15 (0)
From my experience and what others have posted, 4th order L-R crossovers are not the best choice for Maggies in general and IIIa's in particular.
The stock crossover points are:
Woofer LP: 3rd order Butterworth at 330 Hz
Tweeter HP: 2nd order @ 1740 hz. The Q is 0.42 which is actually flatter than a 2nd order L-R (Q=0.5) but with your active xo, L-R is as close as you will get.
The mid HP is 2nd order @ 350 Hz and again the Q is ~0.42.
The mid LP is 2nd order @ 2300 Hz and is a Bessel (Q=0.57)
Crossover points are 370 Hz (down ~6 dB) and 3000 Hz (down ~8db which reflect the effect of the 1 ohm series resistor).
Since your IIIa's have been modified, you probably will want to fine tune the crossovers.
Hope that helps.
�

�

Edits: 02/23/15
RE: IIIa Frankenpan Active X-Over points? - Davey 07:48:24 02/23/15 (12)
You have to "unlink" adjacent crossover filter sections in the DCX2496 to achieve non-textbook crossovers. If you don't....for example....changing the low-pass frequency of the woofer will automatically change the high-pass filter of the midrange. You can do this via the front panel controls, however all settings with the DCX2496 are much easier adjusted via the software remote utility via the serial connection of the DCX.
I don't know how good/valid those settings are from Davy/Satie, but they can easily be input to the DCX2496. Many possibilities to get things screwed up with polarities, delays, etc, etc, so be fully sure you understand what you're doing. If something doesn't sound right it's not the DCX's fault. :)
Dave.

Edits: 02/23/15 02/23/15
- RE: IIIa Frankenpan Active X-Over points? - computerman 14:29:43 02/23/15 (11)
  Thank you Davey as that seems to make sense now. I would assume that there would be no "holes" to worry about as the slope is so low that they would blend in to each other. Is that correct? Just one more question, and that is what does it mean by "(all -3db points)"? I do have the software for configuring the DCX, and a serial/USB connection that works just fine. It is on my Windows PC, but would prefer to use a Mac if you know of any software that would work on the Mac.
  - RE: IIIa Frankenpan Active X-Over points? - Davey 05:51:13 02/24/15 (10)
    When you alter crossover settings from textbook settings, you certainly will create holes in the response.....but in the electrical summation of the slopes, not necessarily in the acoustic response. Nearly all speaker systems (Maggies too) use non-textbook electrical responses to create proper acoustic crossovers. This is the essence of crossover design....but it's not fully appreciated by many users.
    
    -3db simply means that's the frequency at which that electrical filter rolls off to -3db from the passband response. It's confusing though when programming DSP units because different crossover alignments designate different cutoff points depending upon their type. Butterworth crossovers have adjacent filters equal at -3db, Linkwitz-Riley crossovers have adjacent filters equal at -6db, etc, etc.
    
    Cheers,
    
    Dave.
    - RE: IIIa Frankenpan Active X-Over points? - computerman 09:10:38 02/27/15 (9)
      Thanks first for the posts. I presently set the crossover points to unlinked and as neolith suggested as the stock crossover points. If they need tweaking, I will experiment with them. Once I am satisfied with them, I will try exploring the DCX further and learn more about delay, time alignment etc. I studied this in the past when I was thinking of going to a full computer based crossover system, but it has been a while, so i need to brush up. This forum is a great place to learn things. I am very impressed with the level of knowledge of "inmates" and hope to be in a position to contribute more myself as I learn. I do have a Behringer mic for calibration so I will give that a try as soon as time permits and report back.
      I also run a business which keeps me real busy so I cannot get back here as often as I would like, so please forgive delays in responses from me if that matters at all. I just learned that my new apartment is ready and inspected. I have been waiting patiently for this as it means that I will have a much more spacious area to use for the Maggies. It will not be a dedicated listening room, but it will be quite an improvement. The room is approximately 14' by 13' 6". The Maggies and equipment will be on the 14' wall. There will be very little furniture in the room and it will be placed against the far wall facing the Maggies. Hope it all works out well. The apartment walls are sound proofed so I do not have to worry about disturbing the neighbors. They did an awesome job with the construction. They included ethernet cabling in the walls as well. As an IT Consultant/Network Analyst, that means a lot to me.
      - RE: IIIa Frankenpan Active X-Over points? - Roger Gustavsson 05:09:22 02/28/15 (8)
        
        In Reply to: RE: IIIa Frankenpan Active X-Over points? posted by computerman on February 27, 2015 at 09:10:38
        
        Just a little warning for the Behringer microphone, it really need to be calibrated.
        
        http://www.cross-spectrum.com/audio/newgifs/ecm8000_frequency_response_large.jpg
        
        https://www.hifi-selbstbau.de/images/stories/Messraum/MicCal1000/MicCal_ECM8000a125.png
        
        https://www.hifi-selbstbau.de/images/stories/Messraum/MicCal1000/MicCal_ECM8000b129.png
        
        RE: IIIa Frankenpan Active X-Over points? - computerman 14:02:12 03/02/15 (6)
        
        In Reply to: RE: IIIa Frankenpan Active X-Over points? posted by Roger Gustavsson on February 28, 2015 at 05:09:22
        
        I have read that it is difficult to get this mic calibrated, and that it is best done by a company that specializes in calibration, is that true, or could one just use REW to do the calibration?
        
        RE: IIIa Frankenpan Active X-Over points? - Roger Gustavsson 22:30:54 03/02/15 (5)
        
        In Reply to: RE: IIIa Frankenpan Active X-Over points? posted by computerman on March 02, 2015 at 14:02:12
        
        Not sure if Cross Spectrum will do a calibration but they do sell calibrated microphones.
        http://cross-spectrum.com/measurement/calibrated_umik.html
        http://cross-spectrum.com/measurement/calibrated_umm6.html
        miniDSP directly from the manufactor:
        http://www.minidsp.com/products/acoustic-measurement/umik-1
        I like the ones connecting through USB, no need for an additional preamp.
        Measuring techniques need to be studied too! A microphone need to be understood, it is not as sofisticated as our ears (+brain).
        
        Edits: 03/02/15
        
        RE: IIIa Frankenpan Active X-Over points? - computerman 06:58:36 03/03/15 (4)
        
        In Reply to: RE: IIIa Frankenpan Active X-Over points? posted by Roger Gustavsson on March 02, 2015 at 22:30:54
        
        I ordered a MiniDSP. I think that the USB connection is definitely a plus, and it is calibrated. Not bad for under $100. I just hope it performs as well as the reviews say. Do you have any experience with this mic? I could use it on my iPad as well. Shouldn't the Behringer be able to be used for the Auto-Align" feature in the DCX? Or does it also have to be calibrated for this use as well?
        
        RE: IIIa Frankenpan Active X-Over points? - Roger Gustavsson 10:05:10 03/03/15 (3)
        
        In Reply to: RE: IIIa Frankenpan Active X-Over points? posted by computerman on March 03, 2015 at 06:58:36
        
        No, I have no experience of the miniDSP UMIK. Auto-align is often a bad idea. Can you chose a target curve? If not, it is really a bad idea. A straight line (a linear response) is not what is wanted, more a tilted curve dropping towards higher frequencies. A microphone cannot separate direct and refected sounds as our ear and brain can.
        
        RE: IIIa Frankenpan Active X-Over points? - computerman 15:09:44 03/04/15 (1)
        
        In Reply to: RE: IIIa Frankenpan Active X-Over points? posted by Roger Gustavsson on March 03, 2015 at 10:05:10
        
        Roger would you know what the phase of each of the drivers should be in relation to one another?
        
        RE: IIIa Frankenpan Active X-Over points? - Roger Gustavsson 23:03:47 03/04/15 (0)
        
        In Reply to: RE: IIIa Frankenpan Active X-Over points? posted by computerman on March 04, 2015 at 15:09:44
        
        The phasing of the drivers depends on the order of the filters. For instance, if you change from first to second order, phase need to be changed too. In the end, you need to measure the frequency response of the speaker. The crossover will also influence the dispersion charateristics of the speaker. There will be a main direction of "throw" from the speaker depending of the chosen crossover/phasing. Yes, this is complex....
        
        Can you find the original phasing of the drivers? Think you need to start from there. Maybe some guys can run simulations on some crossovers? A good start is to measure the frequency response of each driver without crossover. A warning, it is easy to damage the ribbon tweeter that way. Maybe a large capacitor in series with it gives some protection?
        
        RE: IIIa Frankenpan Active X-Over points? - computerman 14:41:40 03/03/15 (0)
        
        In Reply to: RE: IIIa Frankenpan Active X-Over points? posted by Roger Gustavsson on March 03, 2015 at 10:05:10
        
        I would have to do more reading on the auto alignment to see if a target curve can be done with the DCX2496. I do not recall seeing anything referring to this but I will check further. Thanks for the advice.
        
        RE: IIIa Frankenpan Active X-Over points? - computerman 09:07:55 02/28/15 (0)
        
        In Reply to: RE: IIIa Frankenpan Active X-Over points? posted by Roger Gustavsson on February 28, 2015 at 05:09:22
        
        Roger what do you think of the crossover points I am using? Also thanks so much for your guidance in the choosing of the correct foil for the mids. Magnepan was very cooperative and installed as you suggested. Awesome sound so far. They used the same foil you are using for your T-IV build as far as I know, I did not measure it. I would love to be able to hear your T-IV's once finished. I just entered the crossover values, suggested by neolith, and I heard an immediate improvement. I do not have the T-1 D's in the picture yet, and will not until I move. I also have a sub which is an AR with Sunfire amp, crossing that over via the Sunfire TGP-5 Pre/Pro at 50 Hz, and using it's LFE input with speaker size set to large which means the signal is available at all times to the sub with an additional "Enhanced Bass" setting in the TGP-5. I think it might be a good addition with the IIIa's by themselves, but will take it out of the picture when I add the T-1D's.

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