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Thread: XBL^2 hype, so what’s the disadvantages

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    Noob JCsAudio's Avatar
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    XBL^2 hype, so what’s the disadvantages

    Ok, I get this marketing thing from Adire Audio praising the advantages of XBL^2 technology and how great it is. It goes on to list all the advantages compared to other technologies including underhung motors which I have with my SD3-10 and indeed it is a very low distortion design. I’m not so sure there is an advantage by comparison to my AudioFrog GB12 which I think is an overhung design with nice copper shorting rings to keep inductance in check.

    So there must be shortcomings too because with speaker design there is always a trade off like efficiency for example vs bandwidth. I hear that XBL motors aren’t very efficient and consume lots of power to get the same SPL compared to designs like the AF. So this is an advanced discussion about subwoofer motor design that I hope someone can intelligently discuss and support and I thought this forum needs some good topics/discussion too.

    Another thing I don’t get is they say it’s cheaper to manufacture an XBL motor because of the shorter top plate and coil but why isn’t that reflected in the price or is it? I’m guessing the AFGB series costs much more to make if anything just because of the added copper shorting rings.

    Thoughts?

    https://www.adireaudio.com/wp-conten...Tech-Intro.pdf
    Mazda CX5 AF GB10, AF GB25, AF GB60, JL VX800/8i, AF GB12 sealed, Mmats M1400.1

    Ford F150
    AF GB10, AF GB25, JLC5, JL twk88/Pioneer D8604, Mosconi Pico, JBL Club 5501, Sundown SD3-10 ported @ 30 Hz

    Sienna
    AF GB15, Audiofrog GS690, JL twk88/Pioneer D9500F, JBL GTX500, Alpine SWS10 ported @ 31 Hz

    https://www.diymobileaudio.com/threa.../#post-5608901






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    Re: XBL^2 hype, so what’s the disadvantages

    I would get another Brahma in a heartbeat and yeah on having more power.

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    BURNED OUT Hillbilly SQ's Avatar
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    Re: XBL^2 hype, so what’s the disadvantages

    The downfall I've heard time and time again with XBL subs is they don't distort like a traditional sub. This can make you want more when it's indeed there in pressure but not so much is perceived sound. I'm personally not really a fan of XBL subs for this reason because they always just sound anemic to me. I'm sure I'd grow to prefer that sound over time once I got used to it but I have two perfectly fine subs here to switch between that aren't XBL but still sound pretty good. I might try a Brahma one day but it's at the very bottom of my "upgrade" list.
    They might say "don't try this at home" but nothing about not trying it at your friend's house.

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    Re: XBL^2 hype, so what’s the disadvantages

    The extended magnetic field isn't free, that is the downside. And reducing the field density (aka B aka Tesla aka Gauss) reduced Qes thus Qts aka the respons turns to sh*#. For a given total magnetic field strength, you can only get so much extra Xmax, aka you can only stretch it out so much (as in having a long magnetic gap) before the peak "BL value" starts to drop. You need more "magnet" to compensate (if the steel isn't already saturated). If you don't add more magnetic field lines aka flux , Qts suffers horribly at the hand of reduced B (flux density, which technically reduces Qes, the main component of Qts) because you don't have enough flux density. But in reality it's a balancing act, because the shorter coil allows for tighter gap tolerances which increases B using the same flux. The whole "cheaper" thing is more in reference to underhung designs. The paper states, "and uses a much shorter top plate than the underhung unit (which greatly reduces the production cost)." Try find the calculate the top-plate thickness for a subwoofer with a 1.1" coil and 28mm of Xmax, and let me know what you get. (hint: it's redonkulous)




    XBL^2 Primer

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    Wave Shepherd - aka Jazzi Justin Zazzi's Avatar
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    Re: XBL^2 hype, so what’s the disadvantages

    The immediate downside is generally lower BL strength overall like Oscar mentions. A lower BL strength by itself would increase the Qes (decrease damping) and it would also lower voltage and power sensitivity making the speaker less efficient and generally run hotter for a similar acoustic output.

    The voice coil is generally much more compact than a similar overhung design so the moving mass decreases too which would offset some of the increase in Qes. One way to get some BL strength back is a higher grade magnet or switching to a neodymium magnet which is popular however a neo magnet design usually costs more than a ferrite magnet design, so that's another downside.

    I also like Hillbilly SQ's comment about "distortion sounds loud" so sometimes a low distortion speaker won't sound as loud as another. This might be easier to deal with in midrange frequencies where we are more sensitive to distortion than subwoofer frequencies.

    I did a very in-depth comparison between the Audiofrog GB60 (overhung voice coil) and the Stereo Integrity MkII (XLB2) woofers and the report can be downloaded from my dropbox, below. Many of the effects mentioned above can be seen in the analysis between the two motor designs.

    ---> https://www.dropbox.com/s/x151rliohp...02.11.pdf?dl=0 <---
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    Noob JCsAudio's Avatar
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    Re: XBL^2 hype, so what’s the disadvantages

    Nice! Thank you for that article and detailed explanation Oscar. I’m going to read all of that when I have more time later on.

    I’ve read that article Justin when you posted it on DIYMA but I’m going to read it again because there is a lot of great information there.

    I know what Hillbilly is referring to as I’ve experienced a decent amount of subwoofer drivers now. First time I played the Sundown SD3 (underhung motor) back to back with my SA12 (overhung motor) I noticed the lower distortion from the SD3 and so did my brother-in-law. Same thing when I played my SA12 back to back with my AF GB12. With the GB12 I notice more pressure than sound and with the SA12 I notice or perceive more loudness. By comparison the GB12 doesn’t seem as loud as the SA12 and part of that is the power difference but I do notice the SA12 just has more distortion in general. If I didn’t play them back to back in the same vehicle within a minute of each other than I may not have noticed as much difference. If anyone ever has the opportunity to do this than it’s kind of cool to experience assuming one appreciates that sort of thing.

    I read these arguments made by mostly one certain member on DIYMA that people cannot detect distortion in subwoofers and I just don’t completely buy it. I agree it’s not easy to detect but in an A vs B test within a minute it’s very apparent to me. I even notice a difference between my Alpine subwoofers and others which are also underhung designs. So the XBL motor design I can assume is very similar sounding to an underhung motor design which to me is a good thing?
    Mazda CX5 AF GB10, AF GB25, AF GB60, JL VX800/8i, AF GB12 sealed, Mmats M1400.1

    Ford F150
    AF GB10, AF GB25, JLC5, JL twk88/Pioneer D8604, Mosconi Pico, JBL Club 5501, Sundown SD3-10 ported @ 30 Hz

    Sienna
    AF GB15, Audiofrog GS690, JL twk88/Pioneer D9500F, JBL GTX500, Alpine SWS10 ported @ 31 Hz

    https://www.diymobileaudio.com/threa.../#post-5608901






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    Noob Lanson's Avatar
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    Re: XBL^2 hype, so what’s the disadvantages

    The main thing that is compromised is efficiency. That's your give and take for the improved bandwidth and box size requirements (all else equal.)
    XBL^2 has a different BL curve as was mentioned. It is very flat, so distortion caused by BL variance is very low. Suspension, then, has to be up to snuff. I find XBL designs must be very well engineered to take advantage of the innovative motor.

    XBL^2 also can be used on midranges and tweeters. My current tweeters are KAXBLWTWT's which are mouthful to say, have fantastic sound quality and can dig very deep. They give up efficiency but then again, a tweeter doesn't need to be very efficient so it works here. The enhanced bandwidth is very usable and while REW's distortion plotting isn't the most accurate (in a car anyway), the results are measurably good, and it sounds great to the ear even at cross points in the 1500-1800hz range.

    I personally like XBL woofers, but I would say that LMS woofers take the absolute cake. I'm not sure what designers even use LMS anymore, but for LFE subs or for a sub of moderate size (like a 10) to play down like a 15 (albeit at a lower SPL), it is quite a lot of fun.

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    Re: XBL^2 hype, so what’s the disadvantages

    Just so you know efficiency is overated when talking about subwoofers...

    I remember Jacob Fuller (Sundown) describing what the impact it does on low frequencies.
    To summarize, high efficiency = less lows // low efficiency = more lows (keeping enclosure and parameters the same between the subs)

    Kelvin

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    Re: XBL^2 hype, so what’s the disadvantages

    Ohh, forgot to say that due to the very low distortion of XBL^2 motors, bottoming out is relatively more dangerous because in most common subwoofer topology, you can hear the distortion going up before it bottoms out - not so with XBL^2

    I say this but I'm using an XBL^2 sub and never heard it - I like bass but am not a basshead

    Kelvin

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    Re: XBL^2 hype, so what’s the disadvantages

    Quote Originally Posted by subwoofery View Post
    Just so you know efficiency is overated when talking about subwoofers...

    I remember Jacob Fuller (Sundown) describing what the impact it does on low frequencies.
    To summarize, high efficiency = less lows // low efficiency = more lows (keeping enclosure and parameters the same between the subs)

    Kelvin
    Disagree 100% i will never use less than 90db sensitivity subs or a box for that matter, ever again. Don't care what burp sub company salesman has to say.

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