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No Sawdust, but Metal Shavings

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  • No Sawdust, but Metal Shavings

    Unfortunately, I have no cab build to share this season, but I am working on a speaker-related project: DSP crossover replacing passives. The DSP is implemented on a small computer, using all open-source, freely available software, including an excellent design tool written by charlielaub. Details on the software are here, with more info on my particular project starting in post #22:

    http://techtalk.parts-express.com/fo...d-ladspa-acd-l

    I recently got this gear into a chassis...actually back into it, as it is re-used from a prior project. But I needed a new front panel as some of the prior controls are obsolete. So I was able to get a blank front panel from the manufacturer, Par-metal:

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    I drilled holes for a momentary power switch and green LED with titanium stepped bits. I only have a small fanless computer board, SSD hard drive and sound card to house in the chassis (power supply is an external laptop-type), so probably more room than I need, but I like the idea of re-using stuff. Anyway here is the result:

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    Actually, it is more than just DSP. The unit also accepts analog input. There is also a digital music player called MPD (Music Player Daemon) as well. The music files are stored separately on a Network Attached Storage device, connected via Wifi. I'm able to control the unit from PCs, Macs, iPhone and Android devices. For day-to-day listening, I use an old Barnes and Noble Nook Color, running a version of Android called Cyanogenmod CM7. There's is a nice MPD client called Mupeace that I like (and there are similar clients for all the other platforms I mentioned):

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    I also need to login to the machine and start the process that handles the DSP crossover function. For this I use ConnectBot on Android. It looks a bit 'techy', but for the curious here is what it looks like:

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    So everything works really well and sounds great, but I'm not done yet! I want to take new measurements of the drivers and begin to play with different XO's, e.g. steeper filters, and see how that sounds. So that will be my speaker fun for this year

  • #2
    Wish I could audition your setup.

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    • #3
      Very nice looking project John, if you don't mind me asking what was the budget.

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      • #4
        Thanks Mike and Alan. This didn't cost me much at all since I reused an old computer and chassis and sourced new components second hand. But to to give an idea if starting from scratch:

        $120 - Computer board similar to one I used (Intel DGSE945JT no longer available; Logic Supply suggests a Mitac PD11TI board). A cheaper option would be to use a Raspberry Pi. I think charlielaub has gone this route.

        $60 - Asus Xonar D2 7.1 sound card. I chose a PCI interface because I wanted to put the sound card and computer board in the same chassis. A newer USB unit would cost about $90. BTW I am very pleased with the SQ of this card, both the analog conversion to digital and vice-versa.

        $12 - SSD hard drive, no need for more than 16GB capacity.

        $30 - RAM memory, Wifi adapter, power supply and misc hardware.
        Last edited by jclin4; 05-04-2017, 01:49 PM.

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        • #5
          I forgot to add, one of the largest outlays for anyone going to active XO's will be multichannel amplification. As you know, sky can be the limit, but AVR/HTR's can be a low cost option. I picked up a Marantz SR4600 for $85 (Craigslist) and was pleasantly surprised with its SQ.

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          • #6
            Open the box. Let's see the insides! Sent from my XT1575 using Tapatalk
            Isn't it about time we started answering rhetorical questions?

            Paul Carmody's DIY Audio Projects
            Twitter: @undefinition1

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            • #7
              A fair request and easy enough to cater to. Not much to see, but the computer board, sound card and SSD. The board and the card are connected via a PCI-to-PCI extension cable (the ribbon cable in the pic). This allows the card to be oriented in the same plane as the computer (not perpendicular), and placed easily in available space within the chassis. Neither the sound card nor SSD had through holes which I could use to screw them down to the bottom panel. My solution? Electrical tape, hehe...

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              • #8
                i love it!

                your thread made me think of this i found a while back
                http://www.instructables.com/id/Rasp...in-Crossover-/

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                • #9
                  The chassis looks great and your budget is quite sensible. Looking forward to hearing more about the experience once you play with the myriad variables and get some more listening time. I'm doing something similar in trying to convert my system to digital filters, although you're way ahead of me already.

                  Any reason you couldn't make ecasound start up in the background whenever the computer boots? I imagine you will be stopping/restarting it a lot, but when you're not in one of those phases, it's nice to just flip the power on and start the music.

                  I'd be curious to hear what you think if you're able to do any amplifier experimentation, like patching in an existing stereo amplifier for one of the filter sections. I remember that when I first started using active crossovers, the sound didn't seem to be as sensitive to the quality of the amplifiers. So it may be that a low cost receiver is closer to the optimum for one of these setups.

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                  • #10
                    Pretty cool.

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                    • #11
                      Originally posted by Mike E View Post
                      i love it!

                      your thread made me think of this i found a while back
                      http://www.instructables.com/id/Rasp...in-Crossover-/
                      Thanks, Mike. Yes, I've used that site as a reference to get my system up and running. Here's another one I found really useful. It's clearly written and understandable, and so helped in convincing myself that I could make this work, despite not knowing much about linux:

                      http://rtaylor.sites.tru.ca/2013/06/...oftware-howto/

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                      • #12
                        Originally posted by Michael P View Post

                        Any reason you couldn't make ecasound start up in the background whenever the computer boots? I imagine you will be stopping/restarting it a lot, but when you're not in one of those phases, it's nice to just flip the power on and start the music.
                        That's a great idea, but might not work (at least easily) in my case because of multiple music sources. For MPD playback, I have MPD configured to send output to a loopback (virtual) card, and one of two available devices on loopback. Then the ecasound command takes input from the other device on this loopback "card".

                        For analog playback, ecasound takes input from a real card, D2 in my case. So I have a different script for each scenario. I save some typing by giving them short names, but I do have to log in.

                        It would be nice to have an Android or iOS app, that automatically logs in with stored credentials when opened, then allows you to press buttons to run the appropriate script...but that's dream-ware for now.

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                        • #13
                          Originally posted by jclin4 View Post
                          Neither the sound card nor SSD had through holes which I could use to screw them down to the bottom panel. My solution? Electrical tape, hehe...
                          How about using velcro, double-sided tape, hot glue, or even contact cement to secure them? All of them would allow you to remove the units if needed. The velcro would be especially handy.

                          GeeDeeEmm

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                          • #14
                            Originally posted by gdmoore28
                            How about using velcro, double-sided tape, hot glue, or even contact cement to secure them? All of them would allow you to remove the units if needed. The velcro would be especially handy. GeeDeeEmm
                            This is what I wanted to use. When the chassis was used in a prior project, I used 3M double sided tape to secure a large Meanwell power supply and Sure amp board. Worked well and I thought I still had some on hand but I couldn't find it. But I like your Velcro idea better and will take up your suggestion.

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                            • #15
                              Originally posted by Michael P View Post
                              I remember that when I first started using active crossovers, the sound didn't seem to be as sensitive to the quality of the amplifiers. So it may be that a low cost receiver is closer to the optimum for one of these setups.
                              This is an interesting phenomenon. Maybe one way to think about it is what we are asking each channel of amplification to do in a passive vs active scenario. For passives, each channel has to amplify a full range of frequencies (at certain points in time, not all the time), drive multiple drivers simultaneously, with passive network between the amplifier and the speakers.

                              For active XOs, each channel just amplifies a limited range of frequencies for just a single driver; no caps, coils or resistors in between.

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