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Thread: Project M2 DIY Thread

  1. #751
    Senior Member Odd's Avatar
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    Which mic do you use?
    If you use UMIK 1 from minidsp, you can download a calibration file from minidsp.

    minidsp
    43XX (2235-2123-2450-2405-CC 3155)5235-4412-4406-4401-L250-18Ti-L40-S109 Aquarius lV-C38 (030) 305P MkII

  2. #752
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    Quote Originally Posted by Odd View Post
    Which mic do you use?
    If you use UMIK 1 from minidsp, you can download a calibration file from minidsp.

    minidsp
    Sorry, I forgot to comment on the mic and calibration file. Yes, I'm using Umik-1 with calibration-file. What I don't understand/have equipment for is how to measure pre-amp output. I'm contemplating on getting some Crowns to fiddle with due to some gain issues with my current Ncore 400's with 13 dB gain. Anyone know how the sound quality of Crown Cdi 2/600 or 4/1200 is compared to Ncore?

  3. #753
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    Well, I have a Crown 4/1200 CDi Drivecore incoming, so I guess I'll answer my own questions
    The most interesting part will be the fan noise and white noise along with the differences with standard settings compared to my own DLCP-settings.

    Why did I buy the Crown instead of a soundcard to measure the output of DLCP? Because I'm stupid and ran into some gain-related issues with my Ncore 400's with 13 dB gain. Not enough voltage from the DLCP out to reach more than 15 watts of power at that gain setting, so solve all problems in one smack with a Crown? Remains to be seen.


  4. #754
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    Okay, first impressions of the Crown CDi 4/1200 DriveCore BL is the following;

    1. Way too much hiss for my comfort. 4 meters away with gain settings at the lowest (26 dB) and one speaker connected is very audible.

    2. I struggled for a long time to figure out how to load the M2-file into the Audio Architect software, but turns out that the new DriveCore-line already has plenty of speaker pre-sets in the amplifier ready to be selected through both Audio Architect or from the front panel on the amplifier.

    3. For the life of me I can't figure out how the input/output should be routed and amplifier set-up. First I sent the signals as left-right with 4 channels out from pre-amp (full-range signals on all) to the 4 inputs on the Crown. Routed the corresponding inputs to proper outputs and everything seemed fine and dandy with the crossover and M2 settings loaded in the proper channels, but the bass level was a full 15-20 dB louder than the tweeter.
    Even with -45 dB on Crown outputs and -60 dB on pre-amp out there was 85-90 db in the bass while the tweeter was 65 or so. And to make my head spin some more, the tweeter output was falling about 10 dB making me assume something's off with my configuration of the amplifier.

    I then tried to combine input 1 & 2 (left full range signal on both from pre) and 3 & 4 (right full range on both from pre) in the Crown with the link setting, but that took away the crossover and sent full range signal to the tweeter only - even though the schematics make it look like everything is okay.
    Thankfully I'm careful enough to play a tone generator at 400 hz to check which drivers are playing, so no damage (i hope).

    But I'm deadly scared to fiddle more because these amplifiers will kill my ears if I connect something wrong or try to upload some setting that fails, making the preset revert to default and suddenly full-range signals at max volume pops out.

    Whatever happened to a basic instruction saying "put that wire here & and that wire there, push that knob and you're done!"?


    Oh, and I suppose many will be curious about the fan noise. Well, I'm no fan of that noise, if that make sense. It's not very loud or particularly offensive, but it's certainly audible from 4 meters and you will notice it. Less offensive than the tweeter hiss, but I think I will try to swap the fan with some Noctua pc-fan or something if possible (?)

    Any tips or help will be greatly appreciated!

  5. #755
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    Another look and careful reading of the manual has given me new hope. I can now see, thanks to the brilliant input lights on the Crown, that there's something wrong with the Hypex DLCP.

    Channel 3 (input on Crown) is way louder than the others regardless of what output channel on DLCP I use. Will check wiring on the DLCP board, connections and XLR cable and see if we can sort it out. In worst case I have another DLCP module laying around here somewhere..

  6. #756
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    Hope for success severely smashed to bits
    While I found some wire-malfunction in the DLCP, the JBL M2 settings included in the Crown CDi Drivecore results in a 20-30 dB too hot bass and a falling tweeter level by about 10 dB from 1-20 khz - although flat and nice. Measured 1 meter in front of tweeter.

    I don't understand what's wrong. I also don't understand why setting the outputs to -45 dB on Crown and about -75 db on the Hypex DLCP results in a SPL level of 90 dB below 100 hz with one speaker playing - on the lowest gain setting available at +26 dBU in the Crown.

    Starting to think that these Crown-stuffs could be the absolute worst pieces of shit an audiophile can place in his system. Turning off the pre-amp before the Crown resulted in a 100 dB-ish bass thump I've never experienced before, with the volume level at -45 in the Crown.
    Some DC-offset perhaps? I may need to look into switching out the pre-amp. Or the Crown. Or both.

    Maybe someone can recommend me a nice set of head-sets?

  7. #757
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    Just in case people are interested, here's a sweep of both drivers + combined measured from 1 meter to illustrate what happens with the Crown built-in M2 settings;

    Name:  Crown.jpg
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  8. #758
    Senior Member Ian Mackenzie's Avatar
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    Have you considered the Dirac Minidsp ?

    Used correctly itís a good option for an all digital signal chain.

    My other point is that getting a two diy loudspeaker to sound right is not to be assumed a walk in the park compared to a 3 way. Subtle variations in the response that effect your perception of tonal balance are not the loudspeaker alone but the surrounding environment. Particularly a horn with such a wide off axis response.

    Back to Dirac measurements are based on a number of different mic locations around the listening position. Once Dirac does itís thing you can upload the EQ curve and save several curves it you decide to edit them.

    I hope this is of some use.

  9. #759
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    Thank you for ending my monologue!

    I do actually have Minidsp DDRC-22D Dirac (all digital box), but before you use room correction you need to have the rest of the chain in order. Otherwise you'll suddenly eat 20-30 dB off of the headroom when the correction tries to bring everything back into tune.
    Yesterday I called Harman support and think I ended up somewhere in India. I could barely understand a single word that was spoken and the connection was very bad, so I hung up. I have received answer on mail from some gentleman with the name Dustin that offers to log on to my computer/Audio Architect and help me out, so perhaps that will be the answer.

    I gave up with the included settings and manually adjusted in every setting provided by POS in his document and *poof* went all problems. Suddenly I was back to business with the same sweet sound I had fiddled myself to with the Hypex DLCP and Ncore amps. I checked the tweeter response of the Crown-settings against the Rephase/minidsp result I got from POS's manual and it matches up to a tee.

    This process also fixed the gain chain issues and removed the insane amounts of hiss from the tweeters, so now it's not so bad anymore. By the time I had set this up it was past midnight, so couldn't play anything at normal spl and can't really say how it sounds compared to the Ncore-setup until later.

  10. #760
    Senior Member Ian Mackenzie's Avatar
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    Well thatís good and your persistence has paid off.

    I meant that Dirac might help fine tune the response.

    At some point (delayed with Covid 19) l will offer an analogue active crossover with a plug in card for the diy M2 people with some fine adjustments so those with different drivers can tweak it.

    No noise from fans and no learning complex Dsp settings and certainly a very good option for diy.

    That is likely in early 2021.

  11. #761
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    Bracing

    I am prepping for my eventual M2-style build (modest variations to the factory made versions).

    I noticed on the photos inside the factory versions, the bracing shelves appear to be MDF and about either 3/4 or 1 inch thick. In past builds I have either used 1x2 or 1x4 fir or sometimes 3/4 ply. My thinking was the MDF would not be strong enough. Let me be clear, I am only asking about this for the bracing (please let's not go into an endless MDF vs Plywood debate).

    For those of you who have done the M2 builds (or similar), what was your choice on the bracing? Did any of you regret using MDF. IOW, if you had to do it all over again .... ?

    Thanks, -Tom

  12. #762
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    Quote Originally Posted by withTarragon View Post
    I am prepping for my eventual M2-style build (modest variations to the factory made versions).

    I noticed on the photos inside the factory versions, the bracing shelves appear to be MDF and about either 3/4 or 1 inch thick. In past builds I have either used 1x2 or 1x4 fir or sometimes 3/4 ply. My thinking was the MDF would not be strong enough. Let me be clear, I am only asking about this for the bracing (please let's not go into an endless MDF vs Plywood debate).

    For those of you who have done the M2 builds (or similar), what was your choice on the bracing? Did any of you regret using MDF. IOW, if you had to do it all over again .... ?

    Thanks, -Tom
    I’ve made 8 JBL M2 clones thus far, 3 in MDF the remainder in Birch Plywood. In every case the bracing was 3/4 MDF and cabinets were 1” thick. I think what you make the bracing out of is just down to personal choice but 3/4” MDF is certainly going to be strong enough for this type of cabinet. Yes I would still use 3/4” MDF if I were to do it again.

  13. #763
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    Quote Originally Posted by lesliew View Post
    Iíve made 8 JBL M2 clones thus far, 3 in MDF the remainder in Birch Plywood. In every case the bracing was 3/4 MDF and cabinets were 1Ē thick. I think what you make the bracing out of is just down to personal choice but 3/4Ē MDF is certainly going to be strong enough for this type of cabinet. Yes I would still use 3/4Ē MDF if I were to do it again.
    Interesting! Any difference noticed with the cabinet in MDF vs ply?

  14. #764
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    Quote Originally Posted by tommytoa View Post
    Interesting! Any difference noticed with the cabinet in MDF vs ply?
    No audible differences that Iíve noticed, I did all the cabinets on a CNC machine so the biggest difference for me was the amount of dust involved. I do prefer the ply just because I think it makes a stronger cabinet. I posted quite a few pictures around here somewhere. 😁

  15. #765
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    Quote Originally Posted by lesliew View Post
    No audible differences that Iíve noticed, I did all the cabinets on a CNC machine so the biggest difference for me was the amount of dust involved. I do prefer the ply just because I think it makes a stronger cabinet. I posted quite a few pictures around here somewhere. 😁
    Thank you for answering!

    Do you by any chance have some frequency response measurements from any of the speakers measured relatively near-field? I'm just interested to see if there's any difference between cabinets with rounded edges and the rounded lower lip below the woofer and the simpler constructions without those details.

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