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Thread: Ideal parameters for midbass drivers? Qts, Fs, etc

  1. #11
    Senior Member cvjoint's Avatar
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    Model that driver against the B&C I recommended you. You'll be impressed how well the latter will do. A couple of days ago I was second guessing my choice, namely I thought the CSS SDX7 might give a bit more low end grunt. It turns out the B&C would own it down to 80hz :headbang:. Also, the BC speakers rate depth as bottom mount so it's under 3".

  2. #12
    Founding Member earthtodan's Avatar
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    If I could play them down to 63 Hz I'd be happy. Loud is subjective, I consider myself pure SQ but there are those moments when you want to crank it, and it still has to work.

    Anyway, I haven't ordered anything yet. Here is another woofer I'm considering that has higher sensitivity, plus it's cheap. However I've seen it described as having "dry" bass, which is something I don't want.

    Znom 8 ohm Re 5.8 ohm Le 1.3 mH fs 52.3 Hz Qms 2.79 Qes 0.50 Qts 0.43 Mms 17.7 g Cms 0.52 mm/N Sd 134 cm2 BL 8.2 N/A Vas 13.0 ltrs Xmax 5.5 mm peak Voice Coil 33 mm Sensitivity 2.83V / 1m 87.5 dB

  3. #13
    Founding Member earthtodan's Avatar
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    Quote Originally Posted by cvjoint View Post
    Model that driver against the B&C I recommended you. You'll be impressed how well the latter will do. A couple of days ago I was second guessing my choice, namely I thought the CSS SDX7 might give a bit more low end grunt. It turns out the B&C would own it down to 80hz :headbang:. Also, the BC speakers rate depth as bottom mount so it's under 3".
    I took a look at those too. I'm tempted to just try everything and place a huge speaker order, review them all and then sell most of them (or hoard them). I'm already heavily invested in car audio, so what's another $700 or so on midbasses?

  4. #14
    Senior Member cvjoint's Avatar
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    Loud can be measured objectively, pretty much every facet of it. SQ is nothing more than maximizing SPL for a target THD. You could also play any driver down to 63hz, even a tweeter. So what does this all add up to? Pick a driver that gets you the most output 63hz and up to your tweeter xover without going over xmax and voicecoil thermal ratings. With this one line method you won't have to worry about dry bass and all that other verbiage. Of course the parameters have to be legit for the simulations to materialize, even more reason to go with a B&C, we have some splendid Klippel reports on them.

  5. #15
    Member Candisa's Avatar
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    earthtodan: I'd prefer the previous driver, not because of the 10% higher x-max, but because of the lower Fs and lower Qts: You don't need extra power to raise the Fs and/or Qts, but if you want to make a driver sound like one with a lower Fs and/or Qts, you'll have to give it extra power, losing the 'benefit' of that 1.5dB more sensitivity and risking a burned voice-coil...

    Isabelle

  6. #16
    Senior Member cvjoint's Avatar
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    Quote Originally Posted by earthtodan View Post
    I took a look at those too. I'm tempted to just try everything and place a huge speaker order, review them all and then sell most of them (or hoard them). I'm already heavily invested in car audio, so what's another $700 or so on midbasses?
    It's an option, but ultimately imo too expensive and not necessarily all that useful. You would have to mount them equally well, design the baffle, bolt it down etc. Even if all the work is equally good amongst the drivers you will still have to rely on your ears as an instrument. Then there are drivers that can sound better with a little EQ. and well that can take loads of time to get right. Some aspects of speaker performance, such as non-linear distortion requires long term auditioning. In the end, a few simulations are free and might give better results. I do have to agree with you that there isn't nearly enough 3rd party testing on drivers, but there is enough to give you a few options. Some sites, such as Zaphs posts only positive reviews, if it's not tested odds are...

  7. #17
    Tester Extraordinaire ErinH's Avatar
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    I wouldn't concern myself so much in what MFG specs state. I'm not saying they're useless, but I wouldn't consider them gospel. Do your best to test the drivers in the installed location and measure the t/s parameters there. You may be shocked to find that the reason you bought the driver changed dramatically when you put them in (insert install location here).

    Again:
    Dayton Audio WT3 Woofer Tester
    or
    aRTA + this jig

    Probably the best audio purchase you'll make next to an RTA. You're talking about spending hundreds on drivers???? Spend $100 on this and take out some of the guesswork!
    No more guessing as to what the installed parameters are. You now KNOW. And you can get an idea of what you like based on the real INSTALLED parameters.
    There are many more uses for this thing than simply getting t/s specs, too. It really can help you take your install/system up another notch or two (or five).

    *I sound like a dayton dealer *
    Your ears: The best tools you have... and they're free, too!

  8. #18
    Founding Member earthtodan's Avatar
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    Quote Originally Posted by cvjoint View Post
    SQ is nothing more than maximizing SPL for a target THD.
    I think that's overly simplistic, but let's suppose it's true. THD isn't usually published. However, it is probably responsible for subjective qualities like "dry." We can't extrapolate distortion from the T/S parameters or WinISD frequency response predictions. So I have to take into account people's subjective impressions. Speaking of going by parameters, the B&C speaker has an Fs of 68 hz. Doesn't that sound high?

    Here are a few other drivers I'm considering. So far still keeping it brand-free:

    Option C:

    Power handling: 60 watts RMS/90 watts max
    VCdia: 1.5"
    Le: 0.51 mH
    Impedance: 4 ohms
    Re: 2.9 ohms
    Frequency range: 40-2,200 Hz
    Fs: 40 Hz
    SPL: 91 dB 2.83V/1m, 88 dB 1W/1m
    Vas: 0.86 cu. ft.
    Qms: 2.66
    Qes: 0.62
    Qts: 0.50
    Xmax: 6 mm
    Dimensions: A: 7-1/8", B: 5-3/4", C: 3".

    Option D:

    Sensitivity 2.83V/1M 87dB
    Free air resonance Fs 27.5 Hz
    DC resistance 5.8 ohm
    V.C. inductance 0.35 mH
    Power 70W
    Effective cone area 150 cm2
    V.C. diameter 38 mm
    VC height -
    Air gap -

    Lin. & max. excursion 6.5 / 11 mm
    Air gap flux density -
    Force factor BL Product 6.7 Tm
    Moving mass incl. air 15.5 g
    Net weight 1.75 kg
    Vas 61 ltrs
    Qms 5.0
    Qes 0.39
    Qts 0.36

    Outside diameter: 182mm
    Cut out: 156mm
    Depth: 77mm
    25.4mm = 1" = 2.54cm

  9. #19
    Founding Member earthtodan's Avatar
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    Quote Originally Posted by ErinH View Post
    I wouldn't concern myself so much in what MFG specs state. I'm not saying they're useless, but I wouldn't consider them gospel. Do your best to test the drivers in the installed location and measure the t/s parameters there. You may be shocked to find that the reason you bought the driver changed dramatically when you put them in (insert install location here).

    Again:
    Dayton Audio WT3 Woofer Tester
    or
    aRTA + this jig

    Probably the best audio purchase you'll make next to an RTA. You're talking about spending hundreds on drivers???? Spend $100 on this and take out some of the guesswork!
    No more guessing as to what the installed parameters are. You now KNOW. And you can get an idea of what you like based on the real INSTALLED parameters.
    There are many more uses for this thing than simply getting t/s specs, too. It really can help you take your install/system up another notch or two (or five).

    *I sound like a dayton dealer *
    *Added to wish list on PE.*

    Please help me understand how I can use this to tune my system after everything is chosen and installed.

  10. #20
    Senior Member cvjoint's Avatar
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    Quote Originally Posted by earthtodan View Post
    I think that's overly simplistic, but let's suppose it's true. THD isn't usually published. However, it is probably responsible for subjective qualities like "dry." We can't extrapolate distortion from the T/S parameters or WinISD frequency response predictions. So I have to take into account people's subjective impressions. Speaking of going by parameters, the B&C speaker has an Fs of 68 hz. Doesn't that sound high?
    As far as a proper link between SPL and perception of quality I think it's simple and truthful. Like you mention, figuring out what the SPL and THD would be in a given application is the challenge. With the scientific approach, despite data scarcity at least you converge on the proper solution given enough research. With subjective reviews you can read however many reviews you want, there is almost no common ground, even dry means different things to different people. I like product reviews when I get to hear about reliability and see some menu features for example but I easily skip the verbose sound quality assessment. I feel dumber reading it to be honest.

    But you can extrapolate lots of distortion information from parameters. It may be as simple as knowing that if you apply 10 watts over the rated power compression will set in. You can simulate a driver in IB and look at it's excursion vs. frequency at continuous rated power. You can get a group delay plot, check for kinks in the frequency response etc. Ultimately Erin might give us some unique test results. I'm a big fan of Augerpro's test site that provides xmax and IMD measurements. He covers both methods recommended by W. Klippel.

    An FS of 68 by itself tells me very little. Throw the whole driver in WinISD and lets see what the options are.

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