Pure Audio Project upgrades and tweaks

Starting this thread to discuss Pure Audio Project open baffle speakers, upgrades and tweaks. @Kingrex - if you have had both the horns and Coax10, I would be interested in hearing how they compare. And I copied your earlier post below.

What cables upgrades did you use? And can you share a picture of where you located the crossover? Is it attached to something else, or sitting on the floor? I was wondering about the height of the midrange/tweeter and if I should rake the front up. My system will be the Trio15 Coax10, Playback Designs MPS-8 source and Pass Int-25 amp. I'm still waiting for my walnut baffles to ship from RJ Millworkers.

You have to get the updated speaker cables. Its critical.

And , you have to separate the crossover from the frame. Again critical.

If the crossover is touching the frame, the music is very smeared from the intense physical vibration.

If you use stock, instead of upgraded cables, you loose life, air and bass. Less coherent.

The speaker is very good with these tweeks. You don't need to futz with any caps or reaistors with the Coax crossover.

You need to be patient. They take 500 hours like any speaker to break in. 2000 or a year to really be there. I actually put my coax in the basement connected to a class D amp and laptop for week and let it rip sitting on the floor. I would go dowm 3 or 4 times a day to switxh the album and volume.

Also, mine sit on a 9 inch tall very heavy block of wood that sits on fiberglass insulation. A rug would also work. Massive improvement in bass. Just shocking. And, it raises the center of the coax much closer to ear height. Otherwise its too low and like sitting in a balcony.

The fabric over the top keeps the sun from striking the driver. That is all its for.

 

New layout:
View attachment 130071

I'll move the sub to the back wall, and the Passlabs will move closer to my desk. I have a rack arriving next week, to house the DAVE, Moon amp and Paul Pang switch. I like the Passlabs sideways TBH, they are very well built. Downside is I have speaker cables down the middle of the rug.
I can live with that. Must ensure the dogs don't come in wet and do a shake down!!!

2 large indoor plants in the back corners, curtains - done. ~The system is sounding really nice, will hook up the Passlabs end next week. They are warmer and weightier mids, amazing bass control and detail. They get warm, but not unmanageable.

The quintets look great in your room… really nice and integrated Legolas. My favourite thing with the pureaudioprojects is even with the huge ability to trim and refine they don’t point you into being hung up in an endless analytical loop… their characteristic default is into drawing you back into the music.

 

 

So some more tweaks.
I fitted 3 x Path Audio resistors in the wire wound resistor positions. And left the 2 Mundorf flat resistors as is.

Listening to the Quintet15s last night, it is quite a big change. More energy up top, and more detail in the mids as well. This suits my room and my front end, so very happy with the result. I could also happily live with them as stock I must point out, it is all about personal tastes and music preferences.

 

I have 2 x Duelund Bypass caps to try next, so will report back in 2 weeks after this tweak has settled a bit. The Quintet15s are very uncoloured IMO, the gap between tracks of different music types and recordings is huge, unlike some of my previous speakers. The complete absence of box colouration helps of course, and the reduced room nodes / interaction with my room as open backed.

I also have amazing bass detail and depth, something that seems to worry those thinking about OB but worried about a lack of deep bass and lower energy. TBH I am amazed how good the bass is, really fast and detailed, no bloat, and seemlessly blends / keeps up with the Coax 10 and also it's Compression driver.

 

So some more tweaks.
I fitted 3 x Path Audio resistors in the wire wound resistor positions. And left the 2 Mundorf flat resistors as is.

Listening to the Quintet15s last night, it is quite a big change. More energy up top, and more detail in the mids as well. This suits my room and my front end, so very happy with the result. I could also happily live with them as stock I must point out, it is all about personal tastes and music preferences.

View attachment 131582

Could I ask what are the values you used for the resistors? I was just searching Path Audio and found this forum and appreciate your insight as you sound like where I was wanting to go as well. Have had my duet 15's for a bout a year and have Pass 260.8s driving them. Did you upgrade the Air Core Inductor too?

 

It greatly depends on which mid / treble drivers you have. If the Coax, then similar to mine. If not, then a different crossover completely.

The Coax crossover is forth order and very complex. The Voxativ crossovers much simpler, so easier to mod if you wanted to try that.

I am probably going to end up with one resistor value change only, and most changed to Path Audio. The rest of the parts will probably stay stock.

I have fitted 2 x Duelund bypass to the smallest caps on the mid and treble circuit, and will report back how that sounds. I am aiming for a bit more treble sparkle. I have left one speaker without them, so I can tell how it changes. One step at a time is key, or you can come unstuck pretty quickly.

Overall though, the Path Audio resistors are faster, more transparent than the stock ones, if that is your aim. The parts are very good on the crossover, and make many speaker brands bow in shame IMO. I have seen some which are simply junk TBH, hidden, but just awful quality. So good on PAP for using top parts!

I am in flux as my system is being reconfigured, and my Pass XA60.8s are still not run in yet. I am getting close, and will report back here.

I have 2 options with my Passlabs, run the Chord DAVE direct, or use a Moon preamp I have here, or get a tubed preamp (to be decided). I am hoping DAVE direct works well - we shall see (hear).

I have a feeling the Moon 600i Integrated I was using is smoothing things over a bit, possibly.

 

Yeah, I have the coax.It does look like my Air Coil is .27 ohm and 6.8mH I attached a picture of my stock crossover. I was looking at the upper end as well. I ordered Neotech 28awg occ silver wire for the tweeter, will report back my findings.

Your description of the Path Audio resistors is exactly what I was looking for when I looked into them so hope to pick those up once I see what the silver cable does.

I did create a separate plinth for the Xover and integrated some Iso feet, that stock plinth setup is the only thing I was not crazy about.

 

I instslled a Jensen aircore choke. Solid wire. 14 awg. I have to look up the model. It was about $70 per choke. Bass is much more open and accurate. Fast and natural. Seems to have a lot more energy and air in the midrange. I think Zeev was going for something a little more relaxed. The aircore grabs your attention more as your hearing details.

 

Interesting.
Have you a pic?

 

2 x 000-0040: 6.8mH Jantzen Air Core Wire Coil AWG14, 1.6mm diameter wire - £142.38 (£71.19 each)

I bought these from Hifi Collective.
They are heavy. I have my crossover on a stand behind the speaker. I inserted a wooden dowel into the stand and placed the choke over it.

At the Pacific Audio Fest there was a guy with a open baffle speaker. My friend Bob shot a long video of the product that went onto Audiophile Junkie. Anyhow, the guy is using the baffle as a choke ring over the drivers. This got me thinking. When I put the aircore choke in, my speakers got a little forward. If your using PASS amps or other SS you might have no issue at all with this. Some are saying they are looking for exactly this response. I have a very articulate transformer coupled differential design PP KT88 amp with about 40 watts. It is far far more detailed than my Dartzeel could even imagine approaching. Anyhow, this all made the midrange just a little hot for me.
Back to this other open baffle. It made me assess choking my coax. Just as an experiment, I used toilet tissue paper and ran a strip across the top and bottom of the 10" coax. It actually worked very well to ever so slightly tame the mid frequency. I had it vertically too but that was too much.

I was actually shocked how a single square of TP over the concentric horn tweeter was way too much. Even surrounding the paper mid range was too much. A small amount on the top and bottom was just enough.

What I'm saying is, before you go tearing your crossover apart changing resistors, think about using very subtle damping material to control any excessive midforwardness you might hear from an air core choke.

 

Interesting. In my case I am after a bit more treble up top, mids and bass are fine.

 

2 x 000-0040: 6.8mH Jantzen Air Core Wire Coil AWG14, 1.6mm diameter wire - £142.38 (£71.19 each)

I bought these from Hifi Collective.
They are heavy. I have my crossover on a stand behind the speaker. I inserted a wooden dowel into the stand and placed the choke over it.

At the Pacific Audio Fest there was a guy with a open baffle speaker. My friend Bob shot a long video of the product that went onto Audiophile Junkie. Anyhow, the guy is using the baffle as a choke ring over the drivers. This got me thinking. When I put the aircore choke in, my speakers got a little forward. If your using PASS amps or other SS you might have no issue at all with this. Some are saying they are looking for exactly this response. I have a very articulate transformer coupled differential design PP KT88 amp with about 40 watts. It is far far more detailed than my Dartzeel could even imagine approaching. Anyhow, this all made the midrange just a little hot for me.
Back to this other open baffle. It made me assess choking my coax. Just as an experiment, I used toilet tissue paper and ran a strip across the top and bottom of the 10" coax. It actually worked very well to ever so slightly tame the mid frequency. I had it vertically too but that was too much.

I was actually shocked how a single square of TP over the concentric horn tweeter was way too much. Even surrounding the paper mid range was too much. A small amount on the top and bottom was just enough.

What I'm saying is, before you go tearing your crossover apart changing resistors, think about using very subtle damping material to control any excessive midforwardness you might hear from an air core choke.

Take care on the Jantzen, they look to be higher ohms rating than the Mundorf. I have no idea how that affects things.

 

Take care on the Jantzen, they look to be higher ohms rating than the Mundorf. I have no idea how that affects things.

How do you think that impacts the circuit? How would I, Take Care? If the resistance through the inductor is higher, what would need to be adjusted in the circuit to correct for it? Thanks

 

How do you think that impacts the circuit? How would I, Take Care? If the resistance through the inductor is higher, what would need to be adjusted in the circuit to correct for it? Thanks

I am putting it out there. I have no idea. 1 ohm maybe the difference. So I am totally guessing it may attenuate the bass?
I can't do this mod as I have no room for the bigger inductor.

 

I remember asking 2 people and they both said, close enough, give it a try. Its not a lot of $$$$ for what you will hear. Whether its correct in someone elses system will vary. I like it enough to work with it and keep moving forward. There might well be another air core inductor out there that is better.

 

Yes I agree with you. I know of other flat coils, but are huge and very expensive. I think you have done the right thing.

Once I get my resistor tweaks done, I will change the 82uF cap to Clarity Cap, which is £40 each, so not too expensive. Maybe look at then 2.2uF on the CD circuit for a different brand, lets see. There is a 2uF V-Cap which would be very transparent. 60mm x 30mm diameter, so bit bigger, and not 2.2uF, so would alter the circuit, maybe too much?

 

So I got my system back up with the Passlabs XA60.8s and DAVE Dac direct, no preamp. I am finally getting superb levels of treble details, and generally everything is faster and more energy. Maybe my Moon Integrated was slowing things down and a bit dark? In my previous system and Horn speakers, it was fine. The Quintet15 Coax maybe is a bit polite, and needs more energy up top from the source?

So now I have the burn in of the amps, DAC, and to some extent the Quintet15s. Then I can do some more tweaking. Right now it is really close to my ideal, probably 95% there.

I will order the Clarity Cap 82uFs next week, and another pair of Duelund bypass caps as I only did the right channel so far.

 

So things are getting really good on the Quintet15 Coax. The DAVE direct is a LOT more transparent than via my Moon preamp. I will experiment a bit more with minor tweaks to the frequency balance, look to try lowering the upper treble energy a bit.




As stock



With Path Audio resistors and 2 x Duelund bypass caps.

I have all the Mundorf Mox (green) resistors replaced with Path Audio, which are more transparent. I altered the 15 ohm resistor to 24 ohm before, to bring up the treble gain a bit. I will try reverting that back to 15 ohms, see how that affects things.



My plan is then to replace the 2.2uF Mundorf Silver/Gold Oil cap on the Compression driver circuit with a 2.2uF Jensen Copper foil cap. I can mount it underneath the crossover. This should further smooth / warm up the treble regions slightly, will know once I get them.



Lastly I want to replace the 82uF Mundorf budget cap on the bass section, with a better 82uF Clarity cap.

The sound I am getting right now is really close to my ideal. I think the above parts will further close the remaining gap, and not cost too much doing that. Note I will not have changed any values of the parts, so as not to upset the circuit balance / FR curves / impedance curve.

 

I would recommend changing the 12mH coil of the 12db xover. The 82uf would only make sense if there was an electrolytic capacitor there.
The capacitor is not in the direct signal path but rather parallel to the two bass drivers. The sound signature is weak compared to the coil.

Mundorf MCoil FERON CFN Null-Ohm · Kupferfolie (verbacken), 94

Die Null-Ohm-Spule (NOS) aus Kupferfolie kombiniert auf klanglich eindrucksvolle Weise die Wiedergabetreue der äußerst niederohmigen Feron-NOS-Kerne mit der

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This coil halves the ohmic resistance, which means you get more control with the amplifier over the bass driver.
The second advantage is that you get more resolution in the bass range.
Whether you like this later is of course a matter of taste, the bass becomes more dynamic and more precise.
you want your compression driver smoother with fuller tone without losing resolution. Audyn True Copper is expensive but there is hardly anything better.

Intertechnik ATC/2.20/630

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Interesting, thank you. How do you know the precise layout of the crossover without de-engineering it?

I was advised the 82uF is draining the bass out of band to earth, and affects the sound of the mid driver as well which has no limit to its lower bass.

Thank you for the recommendation of the coil, which is rated at 0.39 ohms. I am nervous changing that spec as it may affect the design of the crossover too much? That may affect tubes amps negatively, more than an SS amp, i.e. expecting the amp to control the drivers more (damping factor?).

Your thoughts?