15 inch Cabinet Design??

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Chicho

Member
2007-08-30 5:17 am
  • #1
    Hello fellow helpers….Well I hope.

    I have had this 15 inch for some time and I have some time to build a cabinet for this unit, I’m a cabinet maker by trade so I think I could do a good job on this unit.

    Speaker specs,
    D=320
    Re=3.6
    Fs=22.05
    Qms-2.68
    Qes=0.77
    Qts=0.60
    Vas=294.35
    Bl=10.15


    But I need the electronic brains in the design of the box.
    I have punched the specs into UniBox and on a vented arrangement of 100L I’m getting an Fb of 16Hz and F3 31Hz..does this sound ok??

    I really don’t want to go much bigger then 100L.

    Thanks in advance.
     
    GM

    GM

    Member
    2003-06-18 1:15 am
    Chamblee, Ga.
  • #2
    Greets!

    Not really, but then it doesn't look any better in 100 L sealed since it wants around 500 L. Even aperiodic ideally needs to be = Vas, so for 100 L and go low the only way I know to do it is sealed with EQ such as a Linkwitz-Riley Transform (LRT). Unless it's a high excursion/power driver though, it won't play very loud down low without distorting due to the low effective efficiency.

    GM
     
    N

    nunayafb

    Member
    2005-08-17 11:05 pm
  • #8
    U-frame is an open baffle arrangement, read the linkwitz website, or search for U and H frames and you will get everything you need to make a decision.
    I have not braced it yet as I am planning on placing sonotube inside. Stuffing, have not experimented with it yet but I'm sure it will provide some benefits. To clarify, the sub that I am using is going to be part of 4-way towers where each tower has one of these subs. I haven't completed it yet so it is neither aesthetically nor acoustically finished (not stuffed/braced, painted)

    -J
     
    V

    vasyachkin

    Disabled Account
    2007-12-31 1:16 am
  • #9
    actually his 15" is probably not intended for anything at all

    have you ever considered that it was intended to look like a speaker so somebody would buy it ? this is the exact way 90% of car speakers are "designed"

    you still could use that 15" in an aperiodic box ... it would even work ... i would not bother to actually build a box for such a woofer though

    the 12" seems alright on the other hand ... you could build a normal vented subwoofer out of it.
     
    N

    nunayafb

    Member
    2005-08-17 11:05 pm
  • #10
    actually his 15" is probably not intended for anything at all
    Click to expand...
    How do you know? What are you basing this on? Do you even know the significance of Qts, Fs, Vas? Every post I have seen you make involves you trash talking something audio related. All opinions are welcome on this forum however if they are not based on any demonstrated experience or knowledge they wont carry any weight.
    You have very strong opinions, that's fine. But people are going to start asking you to back them up, many here have varying combinations of theoretical studies and hands on experience and when they provide input they back it up with one or both.


    .have you ever considered that it was intended to look like a speaker so somebody would buy it ? this is the exact way 90% of car speakers are "designed"
    Click to expand...

    Hmmm, interesting it looks like a speaker, sounds like a speaker and plugs in like a speaker, what a scam they got going. Do you "design" car speakers for a living? If you knew how car speakers were designed you wouldn't be saying that 90% stuff, 90% of car subs have low Qts and a significantly higher fs.


    i would not bother to actually build a box for such a woofer though
    Click to expand...
    I am curious why, is it based on years of experience? Could you tell us what is specifically wrong with it?


    the 12" seems alright on the other hand ... you could build a normal vented subwoofer out of it.
    Click to expand...
    Funny, the 12" is a typical automotive sub, it would be a distant second choice for me if the above speakers are the only option. I am curious what you mean by "normal" sub, is there something wrong with the other options presented?
     
    V

    vasyachkin

    Disabled Account
    2007-12-31 1:16 am
  • #11
    normal box means extension to approximately 40hz but not lower and enclosure size just large enough to reach that low but not bigger.

    if your box ends up being 10 cubic feet with extension down to 20hz you messed up ... because it would have been more economical to EQ that bottom octave that doesnt even have any energy in it than to waste half of your room on signal that isnt even there.

    i think my understanding of audio technology is sufficient to hold the opinions that i express.

    nunayafb said:
    Could you tell us what is specifically wrong with it?
    Click to expand...

    yes. not enough BL. BL^2/Re should be proportional to cone surface area but its much cheaper to use the same motor on every driver from 10" to 18" and thats how you end up with big, cheap drivers that are unusable.

    in practice a 15" driver needs at least a 3" voice coil to get the right BL and still have some Xmax but a 3" VC is something you have to pay for and people dont like to pay.
     
    MJL21193

    MJL21193

    Disabled Account
    2007-03-10 1:20 am
  • #12
    I have to go along with vasyachkin, some of these drivers are just made to look impressive.
    The Bl figure is very low for a 15" driver - I have 2 cheap, but good performing MJ-18 drivers that have a 3" voice coil, 8 lb magnet and a force factor (Bl) of 25, Qts = .35.

    Higher Qts usually means a weak motor, not well suited to a sub.
     
    J

    judtoff

    Member
    2005-07-08 2:25 am
    Bradfort
  • #13
    Hmm I would take the 12 over the 15 any day. The 15 has a very weak motor, and a pretty high qts. It seems like it would only be good in large sealed boxes.

    I disagree about the whole 3" coil being needed for 15s. Hell I have an 18 with a 2.5" coil, and it sounds great, has a good BL(22.1) and lots of xmax(22mm). No doubt larger coils help, but they don't define what a good sub is.
     
    V

    vasyachkin

    Disabled Account
    2007-12-31 1:16 am
  • #14
    judtoff said:
    I disagree about the whole 3" coil being needed for 15s. Hell I have an 18 with a 2.5" coil, and it sounds great, has a good BL(22.1) and lots of xmax(22mm). No doubt larger coils help, but they don't define what a good sub is.
    Click to expand...

    well if its a sub it can get higher BL with a smaller voice coil by using thicker wire and/or taller gap. if its a woofer it needs for the voice coil to stay reasonably light so it will lose some BL on that. with aluminum VC you will lose even more BL for some additional extension in the higher frequencies. also you will need a slightly larger diamater VC if you go with a T-shaped pole piece etc.

    when i said 3" i had a fairly balanced driver in mind but i suppose you can do with a bit less with some tradeoffs.
     
    C

    Chicho

    Member
    2007-08-30 5:17 am
  • #15
    Relax guys...relax.....

    Ok so it seems like the 15 might be used for a coffee table..might put the coffee in it!!

    Ok, If I have to work with the 12, what would a good design look like?

    funny how that 15 is no good, it's magnet is about 200mm in dia and has a 76.1mm coil
     
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    nunayafb

    Member
    2005-08-17 11:05 pm
  • #16
    What do you guys think BL has do with this? Fs, Qts and Vas determine the box requirements.

    Qts is a measure of the total damping of the driver, and doesn't mean weak motor. And a weak motor is a relative term, the strength of the motor is only important when compared to the weight of the moving mass, and only for efficiency. Not for control. (F=MA)

    I also have an 18" with a 2.5" VC, it is by far the best sub I have ever owned. The 12" with the 3" VC is garbage by all standards in comparison to the 18", even with double the power handling and Xmax.

    Chico don't assume the 15 is no good, it is designed for OB/IB- which is my preference for a speaker along with many other people.
    I was serious when I said I had a similar driver in a U-frame, if I had those drivers that 15" would get mounted first.

    well if its a sub it can get higher BL with a smaller voice coil by using thicker wire and/or taller gap. if its a woofer it needs for the voice coil to stay reasonably light so it will lose some BL on that. with aluminum VC you will lose even more BL for some additional extension in the higher frequencies. also you will need a slightly larger diamater VC if you go with a T-shaped pole piece etc.
    Click to expand...
    WHAT!:confused:


    some of these drivers are just made to look impressive
    Click to expand...
    ...BL of 25... and sometimes marketing numbers are thrown around to sound impressive.
    I am getting the impression you guys look at BL as the holy grail of subs, am I wrong?
     
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