Thank you mbrennwa, do you have some recommendation for DSP alternativs? I dont want to go all passiv. I listen 90-95% digital and atm building my own streamer based on a Raspberry Pi. I heard sth about Acourate but didnt dived into it yet.
Was your experience made with the miniDSP HD or the newer Flex?
Was your experience made with the miniDSP HD or the newer Flex?
Camilla dsp on a raspberry pi, personally i use https://www.avsforum.com/threads/diying-a-dsp-processor-engine-solution.2626985/page-33#replies with a windows computer. Minidsp flex is fine but limited in fir taps.
Sorry, can't help much. All I know that my older miniDSP is convenient to adjust filters etc., but does not sound very nice.
Hey, just a short post with some pictures. Just to prove this is not another dead project 
Like I said, will take some months to finish.
First front starts to look like something, some small adjustments needed. I will make large holes/matrix in it, so it's not as thick. Baffle will be arround 44mm or around 1 3/4 inches. Than I will glue the single boards to together, sand them a little and use some 2k polyester to fill gapes at the edges, give the MDF outside more stability and a better surface for painting.
The PTT10s I ordered December last year should be arrive mid-end January.
Like I said, will take some months to finish.First front starts to look like something, some small adjustments needed. I will make large holes/matrix in it, so it's not as thick. Baffle will be arround 44mm or around 1 3/4 inches. Than I will glue the single boards to together, sand them a little and use some 2k polyester to fill gapes at the edges, give the MDF outside more stability and a better surface for painting.
The PTT10s I ordered December last year should be arrive mid-end January.
Attachments
when you say 2k polyester your talking about filler is that right ? I've had good success sealing the cut edge of mdf with 3 or more coats of good pva prior to painting . you might still need a bit of filler of course but it stops it being soooooo absorbent so gives you a much better surface to fill and paint . looking like a really interesting design what are you going to cut the holes for the drivers with do you have a circle jig ? also hoe did you cut that shape please ?
Hi,
no, some filler will be used later on. Prior to painting.
I googled the correct word for it: The 2k polyester is a putty from Presto. Very strong stuff I used before in my car and has no problem to resist vibrations. I sticks to metall and wood with no problem and even after 7 years of driving my last car, there was no way to get the stuff off the car. (I tried to reuse some fittings). Can be sanded very smooth also.
I have a router jig for the circles.
no, some filler will be used later on. Prior to painting.
I googled the correct word for it: The 2k polyester is a putty from Presto. Very strong stuff I used before in my car and has no problem to resist vibrations. I sticks to metall and wood with no problem and even after 7 years of driving my last car, there was no way to get the stuff off the car. (I tried to reuse some fittings). Can be sanded very smooth also.
I have a router jig for the circles.
Regarding miniDSP: My experience is that the company has gone long ways from being mini to being serious DSP.
From the experience of several people I can say that the new Flex Series is not just well DSP capable but also employs much more decent AD and DA conversion than in the past.
For what it's worth: You may want to look for miniDSP Flex series reviews on Audio Science Review and as you're from Germany anyway, look at the german reviews on diy-hifi-forum.eu. If you don't seem to find the stuff, please send me a private conversation.
Regards,
Winfried
From the experience of several people I can say that the new Flex Series is not just well DSP capable but also employs much more decent AD and DA conversion than in the past.
For what it's worth: You may want to look for miniDSP Flex series reviews on Audio Science Review and as you're from Germany anyway, look at the german reviews on diy-hifi-forum.eu. If you don't seem to find the stuff, please send me a private conversation.
Regards,
Winfried
Can you explain why do you want to use of the Purify 10", given it will cover a specific bandwidth from 20Hz (?) to 540Hz?
As you don't seem to have size constraints, you could use a bigger driver (15") that would be much more efficient than the Purify, while being much cheaper, and requiring much less voltage.
The purify drivers combine lower extension with extended bandwidth, with very low IMD, but for the specific bandwidth you are considering, they may not be the best tool for the job.
I haven't model them, but i assume that something like the BMS 15N850 would beat the Purify 10" in all metrics if only considering 20Hz (?) to 540Hz.
As you don't seem to have size constraints, you could use a bigger driver (15") that would be much more efficient than the Purify, while being much cheaper, and requiring much less voltage.
The purify drivers combine lower extension with extended bandwidth, with very low IMD, but for the specific bandwidth you are considering, they may not be the best tool for the job.
I haven't model them, but i assume that something like the BMS 15N850 would beat the Purify 10" in all metrics if only considering 20Hz (?) to 540Hz.
@Lukerhunter - - what is the angle between the front baffle and the beveled sides, particularly around the tweeter? From the images, it looks like it is greater than 45 degrees...
Hallo wgh52, I didnt thought on come back on this topic. But after the sugestions from the others, I checkt the reviews about the Minidsp Flex again and looked at the threads about camilla dsp and others. I dont know excactly where it was (I think camilla) where even the author stated, that the new Flex is so good, that you should use it right away if you are into 2-4 ways. So I think I will go with it. But as said, I will use Hypex Fusion to start and build some custom amps. Will take a long time anyways.
Hi neo, size matters. Not that much that I would go with 6,5" woofers, but not to a point, where I would like to have a 15-21 inches. If you look at the picture of my room, you can see, that there are windows. The room is also used for Home Cinema/Office and the 130" screen dropps right between the speakers, so it covers the windows. So the space between the speakers is limited and to place the speakers closer to the corner would be also limited and counter productive. Hugh speakers would also drag to much attention in my opinion if watching movies. I think 10" is the sweetspot for size to me. 10inch seems to me as ideal for directivity matching at around 500 hz. For the given Xmax, the achived distortion and for an active system with a closed enclosure, the PTT10 fits perfectly.
Hi hifijim, the baffle is exactly 45°. I know from https://heissmann-acoustics.de/en/schraege-fasen/ that the ideal would be 25-35° but I already had a hugh 45° router bit to make the baffle that way.
Hi neo, size matters. Not that much that I would go with 6,5" woofers, but not to a point, where I would like to have a 15-21 inches. If you look at the picture of my room, you can see, that there are windows. The room is also used for Home Cinema/Office and the 130" screen dropps right between the speakers, so it covers the windows. So the space between the speakers is limited and to place the speakers closer to the corner would be also limited and counter productive. Hugh speakers would also drag to much attention in my opinion if watching movies. I think 10" is the sweetspot for size to me. 10inch seems to me as ideal for directivity matching at around 500 hz. For the given Xmax, the achived distortion and for an active system with a closed enclosure, the PTT10 fits perfectly.
Hi hifijim, the baffle is exactly 45°. I know from https://heissmann-acoustics.de/en/schraege-fasen/ that the ideal would be 25-35° but I already had a hugh 45° router bit to make the baffle that way.
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Hey! Late to the party but will give you my opinion. I'm pretty experienced with the Bliesma drivers ... you can write a pm for a detailed conversation (in German ;-))
To your project.
Why not use a Hypex plate amp for your project? Especially with digital input they sound fantastic! And you get a perfect clean signal with no noise and a huge dynamic range - definitely better as your planed amping. Cheaper and more easy to implement.
I would prefer a full digital crossover to be able to time align the individual speakers. This is a great benefit, I would not give that away. But still do the passive filter for the resonance of the midrange.
I'm not a friend of wide mid/tweeter spacings. My speaker designs must also work at close listening distances but also at large distance I prefer a stable horizontal distribution. The wide spacing comes from steering a lobe at the ceiling reflection for AVERAGE angles - but you produce a huge null and bad frequency response in between. Your soud will be good at your exact listening position but for different positions, when moving in the room you can get big errors. So while there is a reason to do so - I don't. I'm a friend of coax and point source, that works better for me.
Edit: You can cross the tweeter lower, esp with a full active crossover. You can experiment but I prefer a low as possible crossover to get a better "point source" behaviour.
You put the lf driver closer in your latest design? Do you have a sketch?
I like to use sheep wool for dampening closed volumes - just start with a medium density and have a few measurements if more or less is needed.
Baffle - you can round your 45° edge to have a better transition. I normall use big roundings, biggest router is 31mm radius.
Great project - best material available so you need to get all the details right to bring them to fill potential!
Why not use a Hypex plate amp for your project? Especially with digital input they sound fantastic! And you get a perfect clean signal with no noise and a huge dynamic range - definitely better as your planed amping. Cheaper and more easy to implement.
I would prefer a full digital crossover to be able to time align the individual speakers. This is a great benefit, I would not give that away. But still do the passive filter for the resonance of the midrange.
I'm not a friend of wide mid/tweeter spacings. My speaker designs must also work at close listening distances but also at large distance I prefer a stable horizontal distribution. The wide spacing comes from steering a lobe at the ceiling reflection for AVERAGE angles - but you produce a huge null and bad frequency response in between. Your soud will be good at your exact listening position but for different positions, when moving in the room you can get big errors. So while there is a reason to do so - I don't. I'm a friend of coax and point source, that works better for me.
Edit: You can cross the tweeter lower, esp with a full active crossover. You can experiment but I prefer a low as possible crossover to get a better "point source" behaviour.
You put the lf driver closer in your latest design? Do you have a sketch?
I like to use sheep wool for dampening closed volumes - just start with a medium density and have a few measurements if more or less is needed.
Baffle - you can round your 45° edge to have a better transition. I normall use big roundings, biggest router is 31mm radius.
Great project - best material available so you need to get all the details right to bring them to fill potential!
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Hi IamJF,
I will use a Hypex Fusion / Plate Amp. My current speakers run on them and Im happy with it. The Minidsp Flex Eight is something for the future to have fun with building some tubeamps and testing different stuff. But not now. Maybe at the end of this year or even later. If I dont like it, I dont think I will lose a lot of money selling it. I do a lot of "kleinanzeigen" buying and selling used stuff.
Full digital crossover is set. Hybrid was a early thought but I wont do it.
I ordered some cheaper parts for notchfilter to test. I just found one example on diyaudio with twin notchfilter for the M74B. But at least in VituixCad I could achieve similar results with just one notch filter. I will test it. What are your thoughts on one or two notch filters?
Im settled on closer spacing, also makes the speaker smaller, lighter and easier to build. I posted a picture out of sketchup earlier this thread or what do you mean?
What do you recommend as a crossoverpoint for the tweeter? To me it was recommended not to go lower than 2,5khz with the T25B.
The sheepwool you mention just arrived today Also used some sheepwool in my last speaker and will do it here also.
The baffleedges will be a little bit more rounded as I will sand by hand. But not much. The front will also be covered with 4mm sheep felt (German: Filz). As Rockport or Wilson Audio have done it before (the darker part at the front if you look at the pictures). I think this will also help a little with diffrection? But to tell the truth: I mostly do it as I like the look.
I will use a Hypex Fusion / Plate Amp. My current speakers run on them and Im happy with it. The Minidsp Flex Eight is something for the future to have fun with building some tubeamps and testing different stuff. But not now. Maybe at the end of this year or even later. If I dont like it, I dont think I will lose a lot of money selling it. I do a lot of "kleinanzeigen" buying and selling used stuff.
Full digital crossover is set. Hybrid was a early thought but I wont do it.
I ordered some cheaper parts for notchfilter to test. I just found one example on diyaudio with twin notchfilter for the M74B. But at least in VituixCad I could achieve similar results with just one notch filter. I will test it. What are your thoughts on one or two notch filters?
Im settled on closer spacing, also makes the speaker smaller, lighter and easier to build. I posted a picture out of sketchup earlier this thread or what do you mean?
What do you recommend as a crossoverpoint for the tweeter? To me it was recommended not to go lower than 2,5khz with the T25B.
The sheepwool you mention just arrived today
Also used some sheepwool in my last speaker and will do it here also.The baffleedges will be a little bit more rounded as I will sand by hand. But not much. The front will also be covered with 4mm sheep felt (German: Filz). As Rockport or Wilson Audio have done it before (the darker part at the front if you look at the pictures). I think this will also help a little with diffrection? But to tell the truth: I mostly do it as I like the look.
Ok that is good. It looked like 60+ degrees in the images.
As @IamJF mentioned, if you can blend the sharp 45 degree edge by sanding, you will reduce diffraction, and every little bit helps. If you can create a 20 - 30 degree transition bevel, perhaps 20 mm wide, this would be ideal. Very low diffraction leads to better imaging and 3D spaciousness.
Overall I like the potential of your project. You are using expensive components, so you owe it to the integrity of your project to go slow, plan everything carefully, and maximize the performance of every aspect. Do a lot of simulation, and do not get too committed to a particular look or aesthetic at this point. Once you have a good simulation, you can work on making it look good later. Hypex amps are a very good choice.
Your baffle layout will determine more than 75% of your directivity performance. Baffle height, width, driver position, and driver spacing are key factors in the Directivity Index. I have found that a midrange-tweeter spacing of 1.2 x wavelength-of-crossover results in a good DI curve through the crossover region. When the DI curve is good, it makes everything else go more smoothly. A flat or gently rising DI curve makes a speaker easier to position in the room, and less sensitive to the treble balance in various recordings.
Hi Luke, a couple of things come to mind:
--I would remove the suspended mass unless you want to make it a serious part of the project, taking care to control the damping and ensure it doesn't add its own reverb to the sound. Eg, you could suspend the mass on guitar strings, and soft felt dampers press against them. I'm not sure if MDF is such a good material for installing tuning pegs, never mind the sound of distributed damping that it already offers.
--I would start with a simpler 'hybrid' crossover design: 1st or 2nd order passive filters that focus on raising the out-of-band impedance, where the speaker impedance starts to increase at high frequencies due to stray inductance. Do that for all 3 drivers. Then correct the frequency response with active filters, progressively refining it until you can say it's good enough, or the cost adding yet another IIR filter stage (unwanted noise, etc) is higher than the improvement it offers. Similarly, with FIR filters it's easy to do too much at once, and not so easy to restrict the processing to only fix what needs fixing.
--I would remove the suspended mass unless you want to make it a serious part of the project, taking care to control the damping and ensure it doesn't add its own reverb to the sound. Eg, you could suspend the mass on guitar strings, and soft felt dampers press against them. I'm not sure if MDF is such a good material for installing tuning pegs, never mind the sound of distributed damping that it already offers.
--I would start with a simpler 'hybrid' crossover design: 1st or 2nd order passive filters that focus on raising the out-of-band impedance, where the speaker impedance starts to increase at high frequencies due to stray inductance. Do that for all 3 drivers. Then correct the frequency response with active filters, progressively refining it until you can say it's good enough, or the cost adding yet another IIR filter stage (unwanted noise, etc) is higher than the improvement it offers. Similarly, with FIR filters it's easy to do too much at once, and not so easy to restrict the processing to only fix what needs fixing.
Hi hifijim, I will try to make a roundover to the 45°. Like earlier said, was my starting point the 1.2 ctc spacing. But the most people seems to prefer closer ctc spacing. And closer seems to work better for me in VituixCad. I must studie your old threads, where you mention it. I think I will maybe build the second front larger with 1.2 spacing and test both.
Hi abstract, the tuned mass damper is out of consideration for now. Maybe a futher project. But like you said, it would take to much time for testing and tweaking for now. For the suspention part there are very small adjustable oil dampers for modell cars/rc cars. I just used some to built a car for my nephew. They dont make noise and can be adjustet very easily.
The Hybrid Crossover is no point anymore.
Hi abstract, the tuned mass damper is out of consideration for now. Maybe a futher project. But like you said, it would take to much time for testing and tweaking for now. For the suspention part there are very small adjustable oil dampers for modell cars/rc cars. I just used some to built a car for my nephew. They dont make noise and can be adjustet very easily.
The Hybrid Crossover is no point anymore.
Hi again @Lukerhunter,
and thanks for seriously considering my proposal
For what it's worth let me briefly share my current DSP Set-up: Basically I'm using 3 openDRC "Kits", one each located at each speaker, modified to employ I²S connected Stereo DACs to form a 4-Way Speaker, does driver corrections and x-over. One openDRC is planned for FIR pre-processing and room mode treatment which then drives the two others via BNC SPDIF. This project progresses slowly, as I'm building boxes as well...
So, if you consider to avoid multiple ADDA conversion (which I do) maybe my approach is inspiring
Best Regards,
Winfried
PS: My phono set up ist the only source being AD converted, all other sources are digital anyways.
and thanks for seriously considering my proposal
For what it's worth let me briefly share my current DSP Set-up: Basically I'm using 3 openDRC "Kits", one each located at each speaker, modified to employ I²S connected Stereo DACs to form a 4-Way Speaker, does driver corrections and x-over. One openDRC is planned for FIR pre-processing and room mode treatment which then drives the two others via BNC SPDIF. This project progresses slowly, as I'm building boxes as well...
So, if you consider to avoid multiple ADDA conversion (which I do) maybe my approach is inspiring
Best Regards,
Winfried
PS: My phono set up ist the only source being AD converted, all other sources are digital anyways.