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Thread: Project M2 DIY Thread

  1. #766
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    Just want to update my struggles with getting the Crown Cdi 4/1200 BL to work properly with the inbuilt M2 preset.
    Loading the files from Audio Architect doesn't work due to some error in the FIR settings when going that route. Manually selecting the M2 preset from the front panel of the amplifier works just fine.

    If you ever try to get this stuff to work through Audio Architect, make sure the speakers are disconnected from the amp. It may look like everything is okay, but the only way to find out is to run a signal through the amp and monitor the inputs and outputs through AA.
    If there's severe clipping with low level signal there's something fishy in the FIR filters (hidden).
    If the speakers are connected at this point you'll have about 127 dB of noise coming through the speakers...

    In Audio Architect you can hold Alt and double-click the Crown-brand in the left hand bottom corner in the speaker channel dsp-screen to open up the FIR section and have a look there.

    I can confirm that the Crown preset is an exact match to the rephase settings provided by POS in his document, so you don't need BSS or Crown to get the M2 settings correct. But the Crown sounds really good and you have 8 PEQ filters per channel available after M2 preset is activated for room correction if needed.

    Oh, and you don't need anything more than a stereo-dac/pre if you go for 4 channel Crown. You can route the left and right channel out to 4 channels in the Crown, so there's that.

  2. #767
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    2452H-SL on M2 horn

    did someone created a crossover to EQ the 2452H-SL on M2 horn?
    I plan to use them crossed at 700Hz with 2226h

    Can someone help me

  3. #768
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    18sound 4015 Beryllium

    Hi there, good people!

    In the search for 2451 with aquaplas or Truextent beryllium I was offered a set of brand new 18sound Nd4015 beryllium drivers at a good price that I couldn't refuse.
    There's not been much discussion about this driver in the M2 horn, so I thought I should share my thoughts and measurements on it. I've not yet experimented much or found the settings in terms of crossovers, slopes, delay or EQ, but I have measured the raw response on the M2 horn.

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  4. #769
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    The measurement is taken in-room at 1 meter distance from the tweeter and gated around 3,6 ms if I recall. 400 hz steep crossover.

    Initial impression is that the driver sounds way smoother than the D2430k but with more "attack" and sting in transients. There was always this harshness with the D2 that I couldn't get rid of no matter how much I tried with EQ. An annoying amount of sibilance with not enough body and weight, very possibly because of the strained performance below 1500 hz.
    Straight off the bat I could hear a remarkable difference in those two areas with the 4015Be (truextent membranes I suppose) but I haven't had time to adjust in a decent balance in the frequency response due to waiting for L-pad and protection caps. I'll update as we go along.

    I have some questions, though;

    - How low should I/can I cross the tweeter? I asked 18sound directly because they recommend 900 hz crossover. They said that recommendation is based on the professional area with the nominal power rating stated as 140w nominal.
    Lowering to 700 hz would be no problem but would lower the nominal power rating to around half, or 70w.
    I'm not sure what that means in practical terms. With EQ to flatten the response I suppose you lower the efficiency to around the same as the reference point, say 700 hz in the raw response, and need to calculate spl per watt based on that?

    If I assume something like 100 dB sensitivity after EQ I would be able to reach 110 dB peaks at 12 feet with 70 watt without destroying stuff? Calculator here; https://myhometheater.homestead.com/splcalculator.html

    - Advice on how to determine crossover slopes and timing? It's really difficult to get good and accurate measurements in the 700 hz area in-room and it's a real struggle to drag the speakers somewhere outside to measure.

    - Experiences with high vs low crossover with truextent in terms of sound quality? To my ears it sounds like the 4015be sounds clearer and more dynamic above 650 hz than the 2216nd woofer does. Might be delusional, but that's my initial impression.

  5. #770
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    - Advice on how to determine crossover slopes and timing? It's really difficult to get good and accurate measurements in the 700 hz area in-room and it's a real struggle to drag the speakers somewhere outside to measure.
    What do the ungated responses look like. If you gate @ 3.6 msec you don't have enough resolution to see what the actual roll-off looks like. You really need to be an octave below. When I did my passive version I had a very hard time getting good measurements in room but after several tries I was able to. I ended up going to a different room and did a diagonal measurement in room on the 2216nd. I used 18dB in a passive set-up. I would go even order L/R in an active if I had a choice that summed properly. Use the same time offset as the original if you kept the baffle set-up the same.

    Rob
    "I could be arguing in my spare time"

  6. #771
    Junior Member Bassdabob's Avatar
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    This Thread!

    Hello Gents!

    many thanks for the big amount of informations and measurements in this thread.

    I really learned a lot about D2,M2 and other drivers here.

    Those M2s look awesome!

    Did anybody use their clone M2s with an 4x3500 and the "original" settings for XOver, PEQs and FIR?
    Are those avaiable at least?
    CROWN+JBL+18SOUND = Fun

  7. #772
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    Hi Tommy,

    It’s not so much the thermal power rating but the thd at the bottom end of the horns range that matters. That said if you are not using your clone at punishing sound levels it should be fine.

    A more scientific approach would be to use REW or other measurement set up to measure thd of the native horn driver using several power levels.

    You can do this with a high quality mic.

    Then work out your proposed crossover slope to work with the woofer.

    Aim for a 700 hertz acoustic point.

    In more detail you can add a series RC network like Jbl did. This will protect your driver from loud power up and power down clicks. It will also form a passive high pass filter. Run an impedance curve and using a series RC and adjust the C value for a 12 dB per octave acoustic butterworth response on the horn. Then you can add a 12 Butterworth crossover slope. The combined slope will sum to 24 db LR. Set the woofer up for an acoustic 24 dB LR response after EQ the driver for a linear response. Then adjust the woofer crossover point until you have a uniform notch with a electrical negative phase on the woofer.

    Test the THD again on the horn at the same power levels as before.

    If the horn is providing an acoustic loading (on a baffle) this will help control the driver diaphragm excursion XMax. As the diaphragm moves beyond the linear range of the driver BL curve in the magnetic gap the distortion will rise. This is more important as the crossover point is moved closer to the cut off frequency of the horn where the acoustic loading stops. The crossover slope will reduce the diaphragm excursion.

    If your active crossover has the adjustment try 36 dB per octave on the woofer and 24 dB per octave on the horn and again check the thd. The 3rd harmonic is one to what as this is more sensitive to your hearing.

    The above procedure will give you an objective indication of the best compromise for crossover point versus thd.

  8. #773
    Junior Member Bassdabob's Avatar
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    Quote Originally Posted by tommytoa View Post
    The measurement is taken in-room at 1 meter distance from the tweeter and gated around 3,6 ms if I recall. 400 hz steep crossover.

    Initial impression is that the driver sounds way smoother than the D2430k but with more "attack" and sting in transients. There was always this harshness with the D2 that I couldn't get rid of no matter how much I tried with EQ. An annoying amount of sibilance with not enough body and weight, very possibly because of the strained performance below 1500 hz.
    Straight off the bat I could hear a remarkable difference in those two areas with the 4015Be (truextent membranes I suppose) but I haven't had time to adjust in a decent balance in the frequency response due to waiting for L-pad and protection caps. I'll update as we go along.

    I have some questions, though;

    - How low should I/can I cross the tweeter? I asked 18sound directly because they recommend 900 hz crossover. They said that recommendation is based on the professional area with the nominal power rating stated as 140w nominal.
    Lowering to 700 hz would be no problem but would lower the nominal power rating to around half, or 70w.
    I'm not sure what that means in practical terms. With EQ to flatten the response I suppose you lower the efficiency to around the same as the reference point, say 700 hz in the raw response, and need to calculate spl per watt based on that?

    If I assume something like 100 dB sensitivity after EQ I would be able to reach 110 dB peaks at 12 feet with 70 watt without destroying stuff? Calculator here; https://myhometheater.homestead.com/splcalculator.html

    - Advice on how to determine crossover slopes and timing? It's really difficult to get good and accurate measurements in the 700 hz area in-room and it's a real struggle to drag the speakers somewhere outside to measure.

    - Experiences with high vs low crossover with truextent in terms of sound quality? To my ears it sounds like the 4015be sounds clearer and more dynamic above 650 hz than the 2216nd woofer does. Might be delusional, but that's my initial impression.
    From my personal experience the compression rate between the driver area and the throat makes a big difference. 4 inch drivers tend to have more body and punch then the smaller 3inch oder even dual ring versions that have a better top end. There is no perfect driver. Only for the desired usage you are aiming for you can choose a good compromise. right now i am using the 2435 in 2,5meters listening distance. before i had the 2451SL that had exactly what you might miss now below 1,5k but the missing detail above 8k i did not perfectly like. It really depends on your final listening levels. In addition to that a more soft amp can do some magic here (e.g. D75)
    CROWN+JBL+18SOUND = Fun

  9. #774
    Senior Member DogBox's Avatar
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    Anyone Try This At Home..?

    Ian said:"The above procedure will give you an objective indication of the best compromise.." spoken like a true politician.

    I was wondering if anyone had thought to build your basic M2 box: same size, M2 waveguide at the top, two ports down the bottom but a -1, 2216Nd instead of

    the straight non-aquaplased one and made up a non biased crossover as per JBL 4367 to see how well things sound?

    The 2216Nd-1 and crossover should be pretty close and one would think the top-end shouldn't need too much configuring although very different from the 4367

    horn that it uses... Don't get me wrong - I have nothing against the DSP set-up, and I plan to build mine that way, but DIY what it is, got me to thinking "How far

    apart are the two ideas, on paper, at least?? I thought 4313B gave Scott [srm51555] a head start when he was contemplating an analog crossover..


    I nearly bought a pair of the '-1' woofers until I was brought back to reality to use all M2 design parts and parameters First - then go playing around if

    that was what I wanted.. Just wondered "just how close would it be...?"
    (yes, this kind of thinking has got me in trouble before but what the heck!)

    Kind Regards,
    Steve

    ...
    Last edited by DogBox; 06-16-2021 at 04:49 AM. Reason: spacing

  10. #775
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    Hi Steve,

    Funny 😄,

    The compromise is crossover point versus distortion.

    Greg Timber’s posted some of this on a discussion about the 4367 in comparison to the earlier systems. Everything about loudspeaker designs is how best to balance compromises.

    If you take a shoe box loudspeaker there are a number of compromises such as efficiency and low frequency response which are obviously accepted

    A large loudspeaker will be less compromised in the above area but there will be trade offs that need to be weighed up in terms of the decisions made on other aspects of the performance. Invariably cost, aesthetics will impact on what might be an ideal design. An ideal design might never sell because it requires full active amplification and might look really weird.

    In diy we don’t have those restrictions. But it does not mean you can go Willy Nilly through a catalog and build a contraption.

    The consumer or product loudspeaker manufacturer has resources and capabilities that the diy loudspeakers guy doesn’t. So the diy guy clones a Jbl design. Good Call. But on occasions some variations are considered. That has to be investigated with more than opinions if you want the result to be good as opposed to worse or different.

    It’s this situation l was referring to in my earlier post.

    It’s very easy to be eager and try other things. An analogy is driving up a gravel road through a desert. You decide to go off the gravel road without a map, compass or a GPS. Surrounded by terrain that all looks the same it’s relatively easy to loose your way.

    So you buy a GPS and figure how to use it. Then you realise you don’t really have any 4WD driving skills or recovery equipment and you get bogged. The tow truck eventually comes and pulls you out but the likely hood is you will keep getting struck.

    Sound familiar.

  11. #776
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    Hi guys, I'm sorry for the delayed response!

    Thank you guys for answering, it's certainly not easy when in-room to create measurements sufficiently good enough below 1000 hz to give meaningful insights about what, how, where and why to do what. I haven't had a lot of time lately to explore too much, so I quickly ended up with the standard M2 settings for the woofer through the built-in presets in Crown and the same crossover slope with the ND4015BE as the original D2430k as measured by myself in-room from 1 meter.

    The actual crossover-point and electrical slope needed to be different to match the slope with the D2, as expected due to no passive filter and different roll-off, but I figured it was the easiest place to start until I have the protection cap in place.

    I'm going on vacation for a month now, so any updates will have to wait, but at least I took a distortion measurement with the 4015be.
    LR 36 dB @ 600hz measured at 96 dB @ 1 meter;

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  12. #777
    Senior Member DogBox's Avatar
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    Very Familiar!

    Quote Originally Posted by Ian Mackenzie View Post
    Hi Steve,

    Funny 😄,

    The compromise is crossover point versus distortion. [That's what I thought you were on about..]

    Greg TimberÂ’s posted some of this on a discussion about the 4367 in comparison to the earlier systems. Everything about loudspeaker designs is how best to balance

    compromises. ]If he's willing - so am I!]

    In diy we donÂ’t have those restrictions. But it does not mean you can go Willy Nilly through a catalog and build a contraption.[That silly, I ain't..]

    The consumer or product loudspeaker manufacturer has resources and capabilities that the diy loudspeakers guy doesnÂ’t.[Why i'm still into DIY, and flatter makers by

    copying their wonderful work- within limits..]

    ItÂ’s very easy to be eager and try other things.[And Yes!]......itÂ’s relatively easy to loose your way. [Unless you bring a mate who's got a GPS!]

    Sound familiar.
    Hi Ian,
    Yep! sounds VERY familiar indeed. And I can see that DSP and the proven package of the M2/BSS/Crown IS as has been said "A game-changer". I'm not

    trying to get back in the ARK, just trying to see what sort of a design might be had with the new drivers? Not trying to build a better 4367 - just a different one

    using M2 parts to make an analogue type of m2?? Maybe I can't see that the idea stinks..

    Also, while having a real close look at the Technical Manual exploded view, it looks as though the drawer has put in a gasket-type-washer between the D2 and the

    mounting flange... The person doing the Parts listing hasn't given it a number but the person doing the drawing actually saw it, so put it in...??

    If you follow the line from where it says Washer (10) 843-01100-07 - that line goes right to it but we know its refering to Flat Washers for the Horn Screws.

    See where I mean?

    Maybe after I get my M2 up and running I might build a crossover - for science sake, and have a play around with my new Sonarworks SoundID test microphone..

    Kind Regards,
    Steve
    ...

  13. #778
    Senior Member srm51555's Avatar
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    Quote Originally Posted by DogBox View Post
    ....I thought 4313B gave Scott [srm51555] a head start when he was contemplating an analog crossover.. …...
    EarlK was the one who gave me the great starting point that I still have plans on trying this summer.

    Thanks,
    Scott

  14. #779
    Senior Member DogBox's Avatar
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    Analogue DIY

    Quote Originally Posted by srm51555 View Post
    EarlK was the one who gave me the great starting point that I still have plans on trying this summer.

    Thanks,
    Scott
    Hi Scott,

    Yes I remember the schematics he drew for you but I also remember Giskard telling you about: The quick fix was to change R9 to 10 ohms; a 30 ohm rheostat

    before C7 and set to 20 ohms.. Post#226 [sorry, I haven't learn't the trick of making that number a Link]

    I'm not sure if that was leaving the 2216 as is per M2 or changing it to the -1 ala 4367. I'm sure once this got going, using the 2450SL might be a real

    chance in the HF position. Putting my meagre finances into this build doesn't leave much room for a proper computer program to work out the proper values, etc.

    The cost of the basic crossover - less biasing (although I got plenty of the right Diodes:1N4935) won't be too bad as long as the exchange rate for the aussie $

    doesn't change like it always seems to do when projects like this come along...

    How were you thinking of tackling it Scott? I learnt so much from your build and this Thread! Really Grateful!!!

    Kind Regards,
    DogBox [Steve]
    ...

  15. #780
    Senior Member srm51555's Avatar
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    Hi Steve,

    Sorry my mind was on the 2451's that are currently installed, not the D2's I used to have in them. My plan was to keep the 2216nd full active and run the top passive. I can't believe it's been 4 years since those post, maybe it's time to do some work on this.

    What driver are you planning to run with the waveguide?

    Thanks,
    Scott

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