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Jims 3 way speaker build

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  • johnny5jz
    commented on 's reply
    These look far better than your previous measurements. Your impedance plot also looks so much better. You can move your tuning up by shortening your port, but it isn't necessary. How does it sound now that your box is sealed up?

  • Chris Roemer
    replied
    Your box is GOOD (this isn't rocket science - after all). An error of a Hz or 2 in tuning, or having the volume off by 10% just won't make a ton of difference.

    Still, this "low Q" woofer isn't really suited to strong "deep" bass (like 30Hz), but 40Hz should absolutely be no problem.
    If you can find a 30 or 32Hz test tone, your woofer shouldn't be moving much, but your port output should definitely blow your incense out, or "fan" it into brilliance! Even though you're -5dB down by then (compared to 50), it's still your port tuning freq.

    Leave a comment:


  • jimbones
    replied
    Here is the Fr of the woofer alone (no XO) and Port.
    Attached Files

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  • jimbones
    replied
    All, I resealed the cabinets and I do notice that the peaks in the zma are now even and the Fb is 32 hz.
    Attached Files

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  • jimbones
    commented on 's reply
    Will do. one question, when you referenced an earlier zma graph, are you saying that was fine and about as good as I could expect. Once I seal up the second cabinet and retake zma and Fr of speaker and port we can see where the new baseline is. Thanks for your help.

  • jimbones
    replied
    Chris Roemer sorry I didnt answer your question. I did not do y own TS measurements. I did a rub and buzz before installing and the zma once in the box. Current ID is 4 inch length is 10.25 inch.

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  • DeZZar
    commented on 's reply
    https://techtalk.parts-express.com/f...07#post1493007

    Looked like you were very close to 32hz back here.....but we need to re-baseline with the sealed up leaks etc...

  • DeZZar
    replied
    The sweet spot for this driver is 32hz tuning in 2.5cu.ft.(70L) for an f3 around 34-35hz.

    According to winISD modelling it'll take bags of power in this configuration and should be capable of producing near on 114db prior to baffle step without getting anywhere near its mechanical limit. It'll handle its thermal limit (200W) all way down to 25Hz in this kind of box. At 91db sensitivity to boot I'd say its a pretty good candidate for strong bass performance.

    jimbones the last impedance sweep you took showed your tuning was right on 30hz (your system impedance) and another prior to that showed closer to ~32hz. But you've since stated you found leaks - which can play havoc with trying to get tuning right.

    Once you have completely sealed up every single leak (including around driver frame and port) can you re-take the impedance sweep (preferably without any crossover parts connected) and re-measure the frequency nearfield for port and woofer and upload (again, without any crossover parts connected). Oh and put all the foam/padding etc you plan on using in place as well.

    Even for the nearfield measurements get the speaker away from all boundaries as far as you can and at least up on a chair away from the floor.

    Leave a comment:


  • Chris Roemer
    replied
    So, let's say your box's interior woofer volume is 2.75cu.ft.
    Exactly what is the current ID and length of your port?
    If you can measure impedance (ARTA, or DATS?), you should SEE your tuning freq. (the center of the "valley" between the peaks).

    Also, IMO, you have a "low Q" (Qes/Qts) woofer, which are not associated with strong bass.

    Leave a comment:


  • jimbones
    commented on 's reply
    Oh and one thing I forgot, I noticed that there is hardly any air coming out the port (or the velocity is so low) I even put a lit incense stick in front of the port to see what happens to the smoke trail and nada nothing. unaffected. That seems strange

  • jimbones
    commented on 's reply
    Chris it is lean below 50 hz. There seems to be little low bass (30-40hz). I say hump because at 65 hz it gets louder relative to the lower bass region so it sounds a bit boomy. I believe I am close. Some music sounds OK its just not optimal. Any other ideas? Could I be overpowering the room?

  • a4eaudio
    commented on 's reply
    WinISD has always given me impressively accurate results.

  • Chris Roemer
    replied
    Did you measure the T/S parms of your woofer yourself (or just going by mfr's claims)?
    Something seems wonky w/Speakerbuilder 2.0.
    A certain (interior) volume box needs a certain length/dia port to be tuned properly (i.e., the driver doesn't alter the box tuning).
    A 4"id port tube needs to be about 11" long to tune a 2.75cf box to near 30Hz.
    Using SB's specs (Qts=0.28, Fs=22, Vas=7.24cu.ft.), a 30Hz tuning for THAT box looks OK (F3 in the mid 30s). It surely does NOT have a "hump" in it. If anything, it looks a bit "lean".

    Leave a comment:


  • jimbones
    replied
    johnny5jz I calculate my net interior volume to be 2.7-2.8 cu ft. I will try the tuning. thanks

    Leave a comment:


  • johnny5jz
    commented on 's reply
    Your woofer measurement looks like a box that is too small tuned too high. Your box size seems right, but if your tuning is too high, it would look like what you are seeing. Going with a longer port will drop your tuning and should even out the response.
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