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.

 

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?

Well, I know your speakers i have something similar here, but it's completely DIY.
Yes, a tube amplifier reacts more to changing the bass coil because the ratio of amplifier output impedance to speaker impedance is lower than with a transistor amp.
With a tube amplifier, it always helps to keep the resistance between the amp and speaker low in the bass range, e.g. cable cross-section and coil in the xover.
The only negative thing that can happen is that the bass sounds too thin.
But it's usually just an adjustment period when listening.
The advantages of dynamics and precision outweigh the disadvantages very quickly.
I use my bass active, the advantage is unmistakable, and I would never switch back to passive in my open baffle.

 

Interesting. But without seeing the actual PCB, or a schematic, you can't know how the circuit is configured. The crossover is a custom 4th order, so quite complex. I prefer to stay on the stock values to avoid sonic degradation. I also not keen to risk bass sounding thin.

Your DIY OBs look nice. Where is the mid/ treble drivers? Or are they full range drivers? If yes, your crossover will be really simple (ideal).

Crossovers IMO can be the most complex part of a speaker, and without lengthy testing and measurements it is possible to really screw up the sonic performance.

 

Interesting. But without seeing the actual PCB, or a schematic, you can't know how the circuit is configured. The crossover is a custom 4th order, so quite complex. I prefer to stay on the stock values to avoid sonic degradation. I also not keen to risk bass sounding thin.

Your DIY OBs look nice. Where is the mid/ treble drivers? Or are they full range drivers? If yes, your crossover will be really simple (ideal).

Crossovers IMO can be the most complex part of a speaker, and without lengthy testing and measurements it is possible to really screw up the sonic performance.

It's ok your decison have fun with your speaker.
My openbaffle is 15"coax only xover for compression driver fullrange with a tube amp.
the 15" woofer underneath is driven actively by a studio amp with internal xover to realize 30hz in my room.
P.S
Your bass xover 12db scroll the homepage to the part xover trust me 12mH+ 82uf the rest for mid+high 24db

 

Ok so you were guessing. Understood.
The problem with DIY and tweaking ourselves is the rewards can be great, but mistakes can end up being costly in parts that don't work as expected in the circuit we are using. I know the Coax crossover that PAP uses took many hours of testing, and was the hardest one they have done so far to realise. We just don't have the resources to do that.

So in your case, I suspect your crossover is quite simple, and easier to achieve, having only the comp drivers in the Coax to control, roll off the driver, and bring in the CD at maybe 3-4K?

 

Well, I know your speakers i have something similar here, but it's completely DIY.
Yes, a tube amplifier reacts more to changing the bass coil because the ratio of amplifier output impedance to speaker impedance is lower than with a transistor amp.
With a tube amplifier, it always helps to keep the resistance between the amp and speaker low in the bass range, e.g. cable cross-section and coil in the xover.
The only negative thing that can happen is that the bass sounds too thin.
But it's usually just an adjustment period when listening.
The advantages of dynamics and precision outweigh the disadvantages very quickly.
I use my bass active, the advantage is unmistakable, and I would never switch back to passive in my open baffle.View attachment 137129

What do you use for a bass amp? and crossover? Did you start with active DSP. Then get a active analog unit? That is what I was considering.

 

What do you use for a bass amp? and crossover? Did you start with active DSP. Then get a active analog unit? That is what I was considering.

No dsp i don't like it.
Yamaha p 3500s amp int xover 12db from 25hz-150hz adjustable.
The yamaha have no high damping factor the bass sounds not dry more full tone i love that cheap thing.
Backside amp

 

It's ok your decison have fun with your speaker.
My openbaffle is 15"coax only xover for compression driver fullrange with a tube amp.
the 15" woofer underneath is driven actively by a studio amp with internal xover to realize 30hz in my room.
P.S
Your bass xover 12db scroll the homepage to the part xover trust me 12mH+ 82uf the rest for mid+high 24db

I think ALL caps and resistors in a passive crossover are in the signal path, and do / will affect the sound. After all, everything in the crossover is the signal from the amp going through it. In an amplifier you have power supplies and other aspects, then a final gain stage, where caps will be in the signal path.

In your bi-amping, the amp you use for the bass needs to be excellent quality, to compete (IMO) with a good power amp driving both bass and mids and highs. But you do have more control over the setting I admit, at least rapid changes. I am tweaking parts and it is a slower process.

I can imagine SS on the bass drivers, and tube on the Coax would be a very nice solution, pending phase shift, time delay and levels matching.

 

Ok so you were guessing. Understood.
The problem with DIY and tweaking ourselves is the rewards can be great, but mistakes can end up being costly in parts that don't work as expected in the circuit we are using. I know the Coax crossover that PAP uses took many hours of testing, and was the hardest one they have done so far to realise. We just don't have the resources to do that.

So in your case, I suspect your crossover is quite simple, and easier to achieve, having only the comp drivers in the Coax to control, roll off the driver, and bring in the CD at maybe 3-4K?

I don't need to guess, I have been building speakers myself for over 20 years, from horns, full-range speakers, 2-3 way loudspeakers and open baffle.
It's OK if you don't trust me.
My speaker is a full dipole, the horn driver is open at the back (lower distortion, flatter frequency response) more 3D sound. The bass drivers are magnetically weakened to achieve a higher QTS value and play deeper in the bass range. Horn driver is 12db at 2.5khz. The active bass run 30- 80hz 12db.

 

Respect for your DIY work. But I defer to this subject:

So IMO all parts can have an effect on the final sound in a crossover.
I would point out a crossover can be (IMO) one the weakest parts in a loudspeaker, based on budget constraints, and the fact it is hidden from view. I respect the brands that show the crossover in their websites (example Sonus Faber). I have over the years always upgraded or tweaked the crossovers in speakers I bought.