Hi there - I was kicking around the idea of making a Pure Audio Project (PAP) clone using an 8" full range with 2 15" woofers...but the x-over had me ruffled. I've never built a speaker or cross over and wasn't sure I wanted to tackle it. Plus I'm not completely convinced a FR will give me the top end I want so I was thinking of adding a tweeter/super tweeter of some kind. I was also thinking about trying to add Dirac room correction to my system. Then recently I've been reading about how far class D amps have come, and maybe thinking of trying something in that vein. Enter miniDSP's new FlexHTX; eight channel dsp with Dirac built in--talk about flexibility. So, and bear with me here....consider an active three way PAP clone using the FlexHTX as the cross over. Drivers would be two Bianco 15" drivers, a Tang Band W8 full range driver in the middle, and some sort of AMT or Ribbon tweeter mounted next to the full range, NEO 3 for example or Mundorf ($$). Amplification would come from two three channel Purifi based class D amps like Buckeye or one of the other similar ones out there. I'd run the woofers up to 400hz, the tang band from 400-8k or so and the tweeter from 8k up. With the functionality of the Flex I can do all the x-over work digitally, time alignment etc and room correction. I'd still have two channels in the x-over left over for subs if needed. I'm confident I can build the open baffle.
What do you all think of this idea? I don't love being bound to using the miniDSP's DACs...but to be honest DACs are all getting pretty damn good and the idea of getting the cross over "right" plus the in-room correction probably makes up for whatever shortcomings the onboard DACs might have.
What am I looking for? Big, open sound, excellent imagine, dynamics, clarity. Music is a wide range but mostly country rock (Grateful Dead, Bill Strings) and 80s rock and small group be-bop jazz. Really looking for that big immersive soundstage I hear people describe from open baffles without giving up the dynamic impact of high sensitivity speakers.
I'd have to liquidate most of the existing rig to fund something like this, and I don't love putting pre/dac/x-over all in one box but maybe that's the ludite in me. I keep reading/hearing great things about the clarity and transparency of these class D amps and seriously considering taking the plunge in this direction. Tell me what you think!
What do you all think of this idea? I don't love being bound to using the miniDSP's DACs...but to be honest DACs are all getting pretty damn good and the idea of getting the cross over "right" plus the in-room correction probably makes up for whatever shortcomings the onboard DACs might have.
What am I looking for? Big, open sound, excellent imagine, dynamics, clarity. Music is a wide range but mostly country rock (Grateful Dead, Bill Strings) and 80s rock and small group be-bop jazz. Really looking for that big immersive soundstage I hear people describe from open baffles without giving up the dynamic impact of high sensitivity speakers.
I'd have to liquidate most of the existing rig to fund something like this, and I don't love putting pre/dac/x-over all in one box but maybe that's the ludite in me. I keep reading/hearing great things about the clarity and transparency of these class D amps and seriously considering taking the plunge in this direction. Tell me what you think!
I not want to frighten you but I see significant problem in OB speakers like PAP or other who have fullrange speaker on relatively large baffle. How they handle dipole peaks and minimums in 400Hz to 4 kHz range what this kind of baffle creates?
Example of simulation can be seen here https://www.diyaudio.com/community/threads/open-baffle-construction-newbie.389548/post-7667979
Example of simulation can be seen here https://www.diyaudio.com/community/threads/open-baffle-construction-newbie.389548/post-7667979
I would recommend the minidsp flex 8 for your project, it has a noiseless DAC, the noisefloor is lower than the minidsp SHD which I also own. Can't compare with the mniidsp 2x4 first hand, but looking at the figures, I'm pretty safe to write that the flex8 performs way better than these.
Thanks all, the Flex8 and the FlexHTX I think are largely the same except the HTX offers balanced outputs. My thinking in using the full range is to avoid having a cross over in the mid-band. So I can run the tang band 400-8k or so, but still add in the top end with the tweeter.
edit: for those in favor of coax vs wideband...any recommendations for a coax that will work in an open baffle?
edit: for those in favor of coax vs wideband...any recommendations for a coax that will work in an open baffle?
Thanks for those recommendations Perry! Can you provide a little detail on how you used them and what plusses/minuses you think each offers? In terms of horizontal dispersion, did you have issues with using the 12" or 15"? I'm guessing all of them perform better in that respect than the wideband. I'm moving away perhaps from the WFW alignment of the PAP clone...maybe CWW would be better with this approach, and get the tweeter more at ear level.
All have good dispersion, much better than a FR driver, you can check these articles for the polar patterns:
1) Bitches Brew 15CXN88
2) Live Edge Dipoles 5208
3) Faital dipoles 12HX230
http://www.tinyurl.com/dipoleplans
More designs at https://perrymarshall.info/speakers/
1) Bitches Brew 15CXN88
2) Live Edge Dipoles 5208
3) Faital dipoles 12HX230
http://www.tinyurl.com/dipoleplans
More designs at https://perrymarshall.info/speakers/
Smanz - thanks, but I'm trying not to have a PC in the chain.
Perry - I've been reading up on the other thread on the BB and I'm going to pursue that design I think! It looks like exactly what I had in mind, only better than what I was thinking. I'll probably use some sort of butcher block for the panels vs the live edge design...or maybe just build in plywood to start.
If you were doing it over....would you tri-amp and use full DSP for the cross overs or stick with the hybrid passive DSP-two way design? I'll probably go for the miniDSP FlexHTX which will give me the balanced outputs and enough channels to also add subs later if needed.
Perry - I've been reading up on the other thread on the BB and I'm going to pursue that design I think! It looks like exactly what I had in mind, only better than what I was thinking. I'll probably use some sort of butcher block for the panels vs the live edge design...or maybe just build in plywood to start.
If you were doing it over....would you tri-amp and use full DSP for the cross overs or stick with the hybrid passive DSP-two way design? I'll probably go for the miniDSP FlexHTX which will give me the balanced outputs and enough channels to also add subs later if needed.
It's up to you as a matter of how complex you want to go. I think technically the triamp option is better but it's more complex, more moving parts, and the biamp version with LC passive xover does work really well. If you're a purist go-for-broke guy, then the triamp probably is more appealing. I definitely recommend the FLEX over the 2x4HD.
Thanks again Perry. I just ordered wood for baffles; found a supplier on Ebay that had 2" table tops in close to the correct size, 24" wide but it shouldn't make a crushing difference I hope I'm excited about this project! I'll probably stick with the 2-way for now but it will take me some time to get all the parts going.
@perrymarshall : Perry, the BB uses 3 x 15” drivers. How significant do you think using 3 drivers of the same size was in maintaining a consistent radiation pattern across the full FR ? Contrast that with your live edge dipoles which used the 8” Radian + an 18” woofer . . .
I've been doing ABEC sims of coax/OB designs stimulated by Perry's work, but which hopefully soon will lead to my own design. From this, I would say you can achieve constant directivity either way. Consider though that in the BB, the coax plays 100 Hz++ and the 15OB350s are essentially subwoofers. The challenge is maintaining the dipole characteristic as you up in frequency. Given that, tapering the baffle and driver diameter as you go up make sense. What I found with the 15" coax was that its midwoofer had already started to beam at XO to the tweeter. This had the effect of bending the dipole side nulls forward which, while not a classic dipole response, might be helpful in room. My current favorite has an 8" coax above a single 15OB350 with a down firing shallow mount 12" sub firing through a floor level slot in the front baffle. The hole in the baffle below the coax is key to maintaining constant vertical directivity. Without it, the asymmetry between baffle width above and below the coax driver shifts the beam out of the horizontal plane ito varying degrees with frequency.
Here is a link to my simulation thread
dipole simulation thread
Here is a link to my simulation thread
dipole simulation thread
@nc535 has this nailed. His simulations are beautiful. He's right, you can go either way. With experiments and measurements, the BB's come out the best. The Live Edge Dipoles have a smidgen too little beaming in the 1-2.5KHz range because of the wide baffle and the smaller size of the 8" coax. The BB's gradually get a little narrow in radiation pattern as frequency goes up, as nc535 says.
@perrymarshall - my BB project is coming together! I'm waiting on one backordered 15OB350, but have all the other drivers. Two quick questions:
Minidsp - the Flex HTX I was considering does not support FIR filters, I confirmed this with Minidsp. They said because it is eight channel it would take too much processor power to run FIR filters over all the channels; I am only going to be using stereo so I think I will continue with a Flex 8. I was drawn to the balanced HTX unit as I prefer balanced connections but such is life. I assume you would see the FIR filter capability as a positive of the Flex 8 over the HTX in this application?
Passive components - noob question but for the passives in the crossover...I understand the schematic in the build notes, but for example on the resisters do I need to worry about rated watts, do I just use through hole mount/surface mount components? I've never built a x-over before, so I'm not familiar with what I need beyond reading the values in the schematic (e.g. I see an 8 ohm resister, but is that a 3W, 5W, 50W etc?). Do you have any preferences for the passives in general?
Thanks again for all the support and guidance, it will be a couple weeks yet before I have the drivers but then it shouldn't take too long to put this together. Can't wait.
Minidsp - the Flex HTX I was considering does not support FIR filters, I confirmed this with Minidsp. They said because it is eight channel it would take too much processor power to run FIR filters over all the channels; I am only going to be using stereo so I think I will continue with a Flex 8. I was drawn to the balanced HTX unit as I prefer balanced connections but such is life. I assume you would see the FIR filter capability as a positive of the Flex 8 over the HTX in this application?
Passive components - noob question but for the passives in the crossover...I understand the schematic in the build notes, but for example on the resisters do I need to worry about rated watts, do I just use through hole mount/surface mount components? I've never built a x-over before, so I'm not familiar with what I need beyond reading the values in the schematic (e.g. I see an 8 ohm resister, but is that a 3W, 5W, 50W etc?). Do you have any preferences for the passives in general?
Thanks again for all the support and guidance, it will be a couple weeks yet before I have the drivers but then it shouldn't take too long to put this together. Can't wait.