Hi all, I have finally gotten my 2 Mark Audio Alpair 7P's (paper cone) in use. I decided on the Fostex P1000-BH (back-loaded horn) boxes available from Madisound. The mounting hole had to be enlarged and I had to add 1/2 inch thick cork between the driver and the baffle board for spacing. There is an internal board just a few inches behind the baffle so I had to also remove the 7P "extra" magnet (the cup/cap with the driver label just pulls off; no glue, just magnetic).
Give these drivers 100's of hours of break-in; they just keep getting better and better! My 60 year old hearing requires a tweeter at the top octave so I'm trying out the AC GS3Si ribbons; 2nd order at 10KHz. I have a coil on the 7P's; custom wound 14AWG 0.16 mH that works very well. According to Planet 10 and others, the 7P's have trouble in the top octave (even after extensive break-in). I found this to be true also; some harshness and graininess definitely above 8 to10Khz. I am quite happy with these, the sound quality is very "realistic". Oh, to only have a few hundred grand to play around with!?
Regards!
Give these drivers 100's of hours of break-in; they just keep getting better and better! My 60 year old hearing requires a tweeter at the top octave so I'm trying out the AC GS3Si ribbons; 2nd order at 10KHz. I have a coil on the 7P's; custom wound 14AWG 0.16 mH that works very well. According to Planet 10 and others, the 7P's have trouble in the top octave (even after extensive break-in). I found this to be true also; some harshness and graininess definitely above 8 to10Khz. I am quite happy with these, the sound quality is very "realistic". Oh, to only have a few hundred grand to play around with!?
Regards!
If you get to the point that you're interested, there are much better enclosures for the A7P - including the FH3, a Pensil, and at least one or two small - almost desk-top sized vented boxes.
Incorporating a small dome tweeter in any of those would be relatively simple, but the GS3 ribbon is a bit larger, and would require some extra fiddly work - certainly in the case of the FH3.
Incorporating a small dome tweeter in any of those would be relatively simple, but the GS3 ribbon is a bit larger, and would require some extra fiddly work - certainly in the case of the FH3.
Last edited:
Latest tweaks: I have upgraded and modified my crossovers. I'm now using a Solen Hepa-Litz 12 AWG inductor with a Superior-Z capacitor in a 2nd order lowpass. Also, I am now using an Audyn copper foil capacitor with a custom inductor in the tweeter circuit. I am sticking with the Fostex boxes for now but may upgrade to the FH3 at some later date. The Hepa-Litz inductor and Copper foil capacitor DO make a difference; I am now noticing more inner detail in some recordings I've been familier with for over 40 years! So, regardless of your design, I DO recommend these Solen and Audyn parts if you want to get the last little bit of refinement. Obviously, the drivers must be capable to begin with, you wouldn't want these expensive parts on just any ordinary driver but the Alpair7P and the G3Si ARE very capable and worth the extra costs!
My hearing drops off like a rock above 10KHz so the tweeter is for me. The Alpair 7P has some graininess or grit in the top octave so I needed to low pass that as well. I am using separate woofers with a separate (variable gain) amplifier. The Fostex box cut-off with the 7P is about 125Hz. For those interested, the low-pass is a 0.16 mH coil with a 0.82 uF cap. To my ears, this preserves the very best of the 7P yet removes the top octave grunginess. So, if you use the 7P yourself, I highly recommend you play around with different filtering of the top octave; it needs treatment but obviously individual preferences and opinions will vary!
Final??? tweaks: I have tried MANY different crossover types and frequencies; with and without a Zobel. I think I have my final configuration. On the Alpair 7P, I am using the Hepa-Litz 0.16 mH coil with 1.33 uF total capacitance and NO Zobel. This gives an electrical X/O at about 11KHz. This capacitance is made up of a Standard-Z of 0.82 uF + Audyn double/MKP of 0.15 uF + Clarity Cap ESA of 0.33 uF. Obviously, one would just use a 1.0 uF bypassed by 0.33 uF but I was experimenting with the parts I already had on hand. There is a definite difference in how "clean" the highest frequencies sound now; pianos, violins, etc. sound very real; zero harshness or glare. The ESA bypass proved to be the icing on the cake. No other capacitor brand or value (that I tried) "cleaned up" the signal as well; lesser caps. just made the problem worse. Believe it or not, the Zobel made things worse as well. This is where laboratory grade test equipment would come in handy. Back before I retired, I had access to all kinds of gear including impedance analyzers, spectrum analyzers, frequency synthesizers, etc.
CORRECTION. I am using a Superior-Z NOT Standard-Z capacitor; sorry, coffee deprived mistake!
latest updates: I have been listening to a great deal of violin recordings lately. On the highest notes; extended harmonics and overtones were being distorted (sounding like a blown tweeter or similar). I took the tweeters out of the circuit but no change so I decided there had to be some kind of minor break-up mode going into excitation within the Alpair 7P. Has anyone else experienced this? I'm guessing the little peak at around 8KHz may be the culprit!? Does anyone with the PLANET 10 Enabled 7P's experience this??? My guess is that their cone treatments would dampen this "mode" down quite a bit. I modified my mounting; extending the frame further out from the main baffle by adding a second thickness of 1/2 in. cork. I added some foam internally just behind the driver to try to minimize internal reflections. Finally; I lowered my crossover to the 7P, raised the crossover to the G3Si ribbon but going with a single capacitor here. The tweeter is now crossed first order at about 17.5 KHz with no L-Pad attenuation. Things are sounding better now BUT, those nasty violin harmonics and overtones are still there! If you don't listen to a lot of violin music, you may NEVER? notice the harshness and distortion I'm getting. I am curious; is anyone else noticing these effects?
Sorry, no photos. Eventually, I may put my 7P's in a more conventional 3-way design and then just buy a matched pair of the Planet 10 Enabled units. I'm also hoping MA will come out with a Generation 2 7P that has a more refined top end.
As I said before, it's only the highest violin harmonics and overtones that I notice this "distortion" on; 99% of everything else is very good!
We have one long term set of A7PeN. They at 1st exhibited some of the HF ringing issue but after very extended break-in it seems to have (mostly) gone away.
I have talked to Mark about what i think os causing this issue and our disapointment with the voicing not having the same kind of relation to the metal cone as the other papers vrs their metal counterparts.
dave
Thanks for the info! My 7P's are straight from Madisound; I wanted to experiment with them; at first, only one driver. I have had them a year now and listen to them almost daily so they have thousands of hours on them. I am doing a custom X/O with now 0.18 mH and 1.8 uF with a custom value Zobel: 7.5 Ohms in series with 0.82 uF. Larger values of inductance roll-off the highs too much (piano overtones become dull) and values less than about 0.14 mH don't roll-off the highs enough for my listening tastes. I thought about doping the dust cap and a few areas of the cone with rubber glue thinking that might dampen the "ringing" as you call it. Can you actually measure the frequency or frequencies that seem to have the most of this "peakiness"? What is the main culprit? Cone, spider, dust cap, surround? Thanks again for the info.
Be careful about using rubber glue on the cone… not something i have tried. I do use Zig 2-way glue on the Fostex drivers on whizzer edges and surround-cone interface. Mark Audios don’t have the same kind of surround/cone interface.
Contact be by email and we can talk approaches.
It should be noted that only some people are sensitive to these kinds of hi-Q resonance issues.
dave
Contact be by email and we can talk approaches.
It should be noted that only some people are sensitive to these kinds of hi-Q resonance issues.
dave
Hi and thanks. I, of course, already thought of a much lower crossover but that defeats my goal here on this design. I am 61 now and my hearing drops off like a rock above about 10KHz so I need a "boost" here. My goal was to use a fullrange driver with as a wide-of-band as possible; using a high sensitivity tweeter above 10KHz and a helper woofer below 100Hz. I have done many other designs in the past 45+ years and always preffered the sound of a 3-way over a 2-way. I almost always try to avoid a crossover in the range of 2KHz to 4KHz; most of my 3-ways had the midrange cover 400 Hz to 4 Khz, many even out to 5KHz or higher. My next step may be to put a small glue spot or self adhesive "felt" pad on the dust cap only. I also thought of doing spirals of glue on the cone similar to the cut and glue method used on the Revelators. Overall, I am quite pleased with the Alpair 7P sound "quality".
Thanks Dave! I will probably take you up on this and I don't mind experimenting on my own either. I am a retired Engineer and former musician. I frequent small jazz clubs from time to time and also go to see symphony orchestras. I am very keen on accuracy and mostly prefer acoustic only instruments; no microphones, amplifiers, speakers, etc. I enjoy rock music also but these days most of my at-home listening is to Baroque chamber music and some jazz. This is why I chose a fullrange design, trying to avoid any phase shifts (crossovers) from about 100Hz to 10KHz. Getting the full range of a musical instrument with all harmonics and overtones from one driver makes sense to me. It also rarely ever turns out "perfect"; no such thing as perfect recording and re-production!
I have an alternative suggestion that might be completely useless if 1) you cannot get Monacor drivers or 2) if you are committed to using the Alpairs.
But just look up the Monacor msh 115* and look at the frequency respose. It is ideally suited to your requirements (does have limited loudness)
I used this driver open, full range with a planar tweeter coming in at 10k, for a friend who is a violinist, and he loves it.
*(Note, NOT the sph 115, or the msh 115HQ)
Thanks! I have had my eyes on the Monacors for quite some time now BUT, I cannot find anyone in North America that ever stocks them. I have considered going for Lowthers or other high end units but can't really justify the extreme expense. So, if your friend is a violinist and loves them, that means there are probably no weird break-up modes, major peaks or dips and that they must be fairly smooth, flat and accurate. Is this how you would describe the Monacors???
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.