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Speaker builders - how about this one?

Discussion in 'Amps and Cabs [BG]' started by Wes Whitmore, Oct 28, 2003.


  1. Wes Whitmore

    Wes Whitmore Supporting Member

    Mar 10, 2003
    Columbus, OH
    I have been busy, and haven't had the time to mess around with this design much, but has anyone designed a cab for 2 DVC JL 8w3-D4 speakers yet? I have had these subs in the garage just waiting for a good home. I just ran them in Winisd, and I came up with the following.

    2.8ft3 internal for both drivers w a single 4" x 10.625" port. This was the big optimal calculation.

    Please give it a try in your program of choice and let me know what you think. Tweak it to your liking and return the results. I might add a tweeter, I might not. I don't need a xover because I will biamp off of my GK RB1001. Freq response looks super flat. 5k would be great for me. I usually kill the tweeter anyhow. Delay is 10Ms @ 40Hz. Output is super flat at around 113 dB (400 watts) for a wide bandwidth. It looks to have a F3 of 27Hz, which seems exceptionally low. I really just want to use it as a great little portable cab (Not that 3 ft is small). Give it a try and let me know what you think.

    JL 8w3-D4 T/S
    FS 35.3 Hz
    QTS .480
    Qes .516
    Qms 6.850
    Vas .79 ft3
    Xmax .390 in
    Efficency 84.6 dB
    Sd 33.2 in2
    Re 6.56 ohm in series
    Znom Dual 4 ohm
    Pt 125 RMS

    Wes
     
  2. cjgallen

    cjgallen

    Oct 19, 2001
    eek

    Yeah, the response is nice and flat, but you gotta put a WHOLE LOTTA POWER to them, and they can only handle 125W RMS.

    As a bass cab, eh. Might make a decent car woofer though.
     
  3. Wes Whitmore

    Wes Whitmore Supporting Member

    Mar 10, 2003
    Columbus, OH
    It is a car woofer, but I have been running well over 200 watts a piece in them for a long time. With two of them, and over 400+ watts, it should do better than on paper. Two of these hit 139 dB in a car with under 250 watts rms, so I should be able to get 110 dB or so in room with my GK1001RB head. They won't be super loud, but hopefully they will get some great extension.
     
  4. I have these worked out already in my spread sheet. They won't hit more than 105 dB at full power, so use is very limited.
     
  5. Yup, get ready for a big disappointment. 84.6 dB requires 30 times the power of any average 100 dB 2x10. If you need 100 watts to bring the 100 dB cab to life (which isn't far fetched), you'd need 3,000 watts for the sub (which is pretty insane).

    One of my setups consists of 2 1x12 subs with nearly 93 dB efficiency and I'm always struggling with 320 watts into them. Low end beyond belief, but they hardly cut it.

    As for bass extension, any other cab will blow this sub away. I have used my rig as a sub once under a small PA, on full power in the 30-80 Hz range exclusively, and it "got by".
     
  6. Wes Whitmore

    Wes Whitmore Supporting Member

    Mar 10, 2003
    Columbus, OH
    Oh well, I guess I will put them back in the car where they belong. JL has always had low eficiency ratings, and they are usually louder than other car subs. They even try to justify the low numbers on their site. Oh well. I guess I might just get a delta 12 or just get a ACME B1 then.
    Thanks,
    Wse
     
  7. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    In one of the chapters in Vance Dickason's book, he conducted an experiment to see how a speaker would behave in the relatively confined acoustic space of a car. The outcome was impedance and excursion were the same as in free-air, but frequency response changed significantly. At lower frequencies, the enclosuer was up to 6dB louder. That's a lot of apparent extra SPL.

    Also was 139dB measured with the whole stystem running, or just the sub on it's own? Turn off all the other speakers and Bgavins 105dB is looking closer to the mark.
     
  8. Wes Whitmore

    Wes Whitmore Supporting Member

    Mar 10, 2003
    Columbus, OH
    No, it was in a hatchback with some bass CD playing through pretty much just the subs. Cabin gain is a very good thing when it comes to subwoofers in a car. They have single 15s that hit over 146dB now.
    Wes
     
  9. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    hmmm.....Something tells me they are using a different dB weighting. 120dB is the pain threshold from memory. 130 dB is twice as loud as 120 dB. 140dB is twice as loud as 130dB. 146 dB would make a human head explode.
     
  10. Yup, but you don't actually think they run the car rig that loud when they're in the car, do you? They take the stereo's remote and back off, then set loose the beast (or beats..!)

    It's about SPL contests. The only important thing is to go as loud as possible and to make the rig itself look as nice as possible. Not my thing though, though I have about 240 watts clean RMS power available in my car. The amp is under the back seat.
     
  11. hi,
    i know a guy who hit 153 db in his car, and he was sitting in the drivers seat...
    the thing is that it was at around 50Hz..our ears are not as sensative to sub and really high frequancies...but 153 Db at say 500 Hz would deffenatly make your head explode
     
  12. Wes Whitmore

    Wes Whitmore Supporting Member

    Mar 10, 2003
    Columbus, OH
    It is definately all low bass material (under 100Hz). Usually bass sweeps down to 20 Hz or so. It is an A weighted SPL meter. I was into car audio pretty heavy growing up, and came up with some pretty radical boxes that really cranked out the bass. Now, things are even louder. It used to take 4 15" subs with 1200 watts to get 145 dB in a car. Now it can be done with just one 1200 watt sub. But yea, it is loud, and I can't sit in the 150 dB vehicles, but many people can. The highs are generally only around 125 dB or so before the start clipping. There is no way to make the highend keep up with a wall of subs anyways. It's all relative. The work record is well over 176 dB now. That's intense. People control that remotely, of course.
    Wes
     
  13. WOW! That translates to 4 MW (yes MEGAWATTS) in a free field situation with a 100 dB sensitive loudspeaker. With a car sub of 85 dB, it would be about 1.21 GW (Remember Back to the future?? "How could I be so careless!")

    All theory of course.
     
  14. Wes Whitmore

    Wes Whitmore Supporting Member

    Mar 10, 2003
    Columbus, OH
    Its like 40,000 watts and 24 subs. I am not with it much more. Back to the future is right...
     
  15. rossco

    rossco Unregistered

    Mar 8, 2003
    Think the word 'car' was the give away in this one ;)
     
  16. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    According to the audiologist that made my special earplugs for me (there's a hint in there people), Mid and high frequencies at high SPL do indeed hurt but it's the low frequencies that do the permanent damage to your hearing.
     
  17. Wes Whitmore

    Wes Whitmore Supporting Member

    Mar 10, 2003
    Columbus, OH
    I guess it is a good thing I didn't get into SPL much. Regardless, I guess cabin gain helped out a lot. I just figured I could get 115 db out of it, according to WINISD. I guess that someware might be a little off anyhow.
    Later,
    Wes
     
  18. geshel

    geshel

    Oct 2, 2001
    Seattle
    Well - the thing is, that the behavior of the sound waves is completely different inside the car than they would be in free field. SPL is measured via pressure - and pressurizing an enclosed space like a car is a whole other thing than creating a freely travelling wave with a certain peak pressure. Even if the car has open windows etc, at bass the wavelength is much larger than the openings so it's still very much a pressure system.
     
  19. Turue of course, but I was only letting my mind run free... about how that kind of SPL translates to a free field situation

    The 176 dB level was obtained with 40,000 watts over 24 drivers. That's not far from 4 MW; only 20 dB, which is the small-room gain you mentioned

    Makes you wonder what SPL levels are measured inside a cabinet. I'd say it could go far over 200 dB.
     
  20. < melt >

    Remember the inverse square law... they probably measure these fantastic dB levels at 1" from the cone. Inside an automobile cabin with multiple subs is the same as being inside the enclosure.