'Neodymium' Lightweight Magnet

Discussion in 'Amps and Cabs [BG]' started by fourstring44, Sep 11, 2003.

  1. fourstring44


    Jul 22, 2003
    St. Louis
    Hi all,
    I'm in the process of shopping for speakers for a 2X12 bassman CAB and was curious if anyone had anything good or bad to say about these speakers. I really want something light to haul and the specs on these look pretty good to my untrained eye.
    Thanks, Curt

    Genuine Eminence

    DELTA LITE 2512 - 12" WOOFER






    Item Price: $139.99


    Delta Lite 2512

    Nominal Basket Diameter
    12" / 304.8mm

    8 ohms

    RMS Power Rating
    300 Watts

    Frequency Response
    45Hz - 3.5kHz

    Voice Coil Diameter
    2.5" / 63.5mm

    Max. Crossover Frequency

    Shipping Weight 8lbs./ 3.62kg.

    Mounting Information

    Overall Diameter
    12.38" / 314.3mm

    Bolt Circle Diameter
    11.62" / 295.15mm

    Baffle Cutout Diameter
    11.04" / 280.4mm

    No. Of Mounting Holes

    Mounting Hole Diameter
    0.275" / 7mm

    Overall Depth
    6.05" / 153.56mm

    Magnet Weight
    7 oz.

    Thiele-Small Parameters

    Resonant Frequency (fs)
    42.13 Hz

    Impedance (Re)
    5.21 ohms

    Coil Inductance (Le) 0.71mH
    Electromagnetic Q (Qes)

    Mechanical Q (Qms)

    Total Q (Qts)

    Compliance Equivalent Vol. (Vas)
    154.52 Liters/5.5cu. ft.

    Voice Coil Overhang (Xmax)

    Surface Area of Cone (Sd) .053236m2
    BL Product (BL) 11.33 T-M
    Peak Diaphragm Displacement Volume(Vd) 154.4cc
    Impedance @ Resonance (Zmax) 58.45 ohms

  2. I have both cataloged in my spread sheet. Both will do the job well compared to other Eminence drivers of the same size. Well suited for 4-string bass.

    The 12" Deltalite requires a substantial cabinet of 3.15 to 3.75 cubic feet internal volume for correct tuning. The 10" requires much less at 1.28 to 1.39 cubic feet.

    Overall these are nice drivers. The only downside to any of the neo drivers is they will NOT tolerate over heating. It destroys the magnetic motor.

    I like the 10" a lot, especially for a light weight design. The 12" is out in my book, due to the excessive cabinet volume required for correct tuning. You could stuff it into a smaller cab, and get the response problems inherent in this practice. IMO, the Omega Pro 12 is a much better choice for a small cabinet 12" driver.
  3. fourstring44


    Jul 22, 2003
    St. Louis
    Thank you! It sounds like the 12" may give me problems since I"ll be using using a CAB not very well suited for bass to begin with. BUT, it sure looks apealing, because of the weight. After 30 plus years of moving heavy gear, I have just about run out of gas:)
  4. ebozzz

    ebozzz Supporting Member

    May 17, 2001
    Denver, Colorado
    I've been wanting to ask this question for a while now. Maybe it's silly but here goes. Do the neodymium magnets affect tone any differently than standard magnets?
  5. No, I can't think of any scientific reason why. The magnet supplies the magnetic field for the coil to operate in. The design of the flux gap is the same, only the magnet is smaller and lighter in weight.

    Bruce, I don't have to tell you this but here goes nothing: the heat problems should be accounted for by the designer of the driver when measuring specs. If a driver is spec'd for a specific thermal power, I don't expect it to overheat when used below the maximum power, just like a "normal" dirver.

    This should, in no way, affect anyone's choice in magnetic material.
  6. barroso


    Aug 16, 2000
    i have a 2x10 cab with neodymium.

    super light and great tone for me-
  7. ebozzz

    ebozzz Supporting Member

    May 17, 2001
    Denver, Colorado
    Thank you Joris! ;)
  8. thumbtrap


    Jun 26, 2003
    Eminence has the same cautions on their pages about the drivers. Perhaps one difference is that if you blow a traditional speaker you can recone it till the cows come home. But with Neodymium you can indeed cook the magnet, resulting in a rather large and expensive paper weight.

    It seems this problem could be avoided with a thermal fuse or circuit breaker. The drivers are already expensive - and folks will pay for the weight premium - so it's not like a couple bucks will kill the design.
  9. I stand corrected. That makes sense - I didn't look at it that way, you don't assume a driver's gonna blow, so I didn't assume it matters much. But if it does blow, you better not blow the whole thing.

    But thermal protection is always a good idea when working in the kilowatt range ;) I wonder how many professional cabs have this. None of the non-pro cabs I've seen have it.

    BTW I salvaged some Neodymium from hard disk pickup motors. It's really unbelievable how strong these 1-inch magnets are. Makes me wonder about Nd speaker magnets.
  10. ebozzz

    ebozzz Supporting Member

    May 17, 2001
    Denver, Colorado
    That's the exact reason why I was questioning how they affect performance. They are supposed to be much stronger than standard magnets.
  11. The Eminence neo drivers have a shorter magnetic gap than their conventional drivers.

    The BL factor (magnetic motor strength) is pretty low at 10.6, but this is only part of the story. The BL factor is calculated by the amount of work the magentic motor will do. The work is the combined mass of the cone and its associated air load (Mms).

    A ratio of BL:MMS is an arbitrary number that shows the strength:mass ratio of a given driver. The Deltalite 2510 falls very close to a Delta 10a. The Carvin PS10 is a bit weaker, and the JBL E110/Delta 10b are stronger. All are at the top end of the scale. All the other Eminence drivers are weaker using this comparision. I expect this, as the smaller drivers have a higher BL:MMS ratio than do the large cone drivers.

    The 2510 is an appealing driver because of its tuning, F3, box volume, and response bewteen 43 and 89 Hz. I think it would make a tasty, light weight 1x10 that does the job for a 4-string.
  12. geshel


    Oct 2, 2001
    Actually, Joris, I'm pretty sure the layout of the magnet and pole pieces is different in Nd speakers than ferrite ones. Because the magnet is much smaller, the best layout isn't the same as the typical ferrite one (of a wide, thin donut magnet). The ones I've seen (not the Eminences, admittedly) have had the magnet within the voice-coil diameter, actually.

    I'm not saying that this will necessarily change the sound - but it has the potential to.

    Here's a random Nd woofer pic I pulled off of the web:

  13. geshel


    Oct 2, 2001
    Ah, here's a pic of a Deltalite 10

  14. barroso


    Aug 16, 2000
    here's a pic of the 10" B&C Neodymium woofer which my Markbass traveler 102 cab is equippeed with:


    and here's the cab:

  15. geshel


    Oct 2, 2001
    Those things are incredible! And dangerous :eek:

    It's also great how tightly controlled the fields are. They don't have much pull to the edges, and almost none at all to the back (must be mu-metal plates they're mounted on), but get them face-to-face, and watch out! When they are stuck face to face, you can hold the pair up to a monitor screen and it shows hardly any distortion. Do that with one by itself, and - well, no, don't do that!
  16. Petebass


    Dec 22, 2002
    QLD Australia
    The re-cone kit for the P.Audio Neodymium speakers come with the entire magnet assembly. Now I know why.
  17. What I would like to know is what happens if they put a normal-sized neodymium magnet in a driver. I think we could get rid of the loud/low/small trade-off. It would be a $2000 driver though....

    Imagine this: a 100 oz Neodymium magnet. It'll probably draw the iron atoms from your blood!
  18. fretlessrock

    fretlessrock Supporting Member

    Aug 8, 2002
    I've been using an Ampeg Portabass PB210H for a while and it has been a gret sounding and performing cab. I understand the concern over thermal issues, but it would be good to get a feeling for what it would take to reach these temps during normal use, within the rating of the driver. In a 4-Ohm 2x10 or 2x12 you are splitting the power between the drivers, and in the case of the Eminence Deltalite 2512 and 2510 the rating is 300W. A pair can dissipate 600W within the rating.

    So while Bruce is doing you a service by bringing it up, he isn't saying how the problem might arise. I think that the prudent way to present that data is to tell you to hang on to your warranty and be careful if you think that you will be near the rated max for these drivers.

    Like all new technologies you take a bit of a risk as an early-adopter. I originally wanted to refit my Flite 110's with the Eminence Deltalites but I think that they might blow away in a stiff breeze!
  19. thumbtrap


    Jun 26, 2003
    I agree - I wouldn't let the thermal thing dissuade me from buying them. Especially now that Petebass tells us the magnets come with the recone kit (though it seems to me it'd be more economical to separate the two). Lighter weight speakers are worth something,aren't they?
  20. Petebass


    Dec 22, 2002
    QLD Australia
    I don't know if that applies to other brands though. Might be a good idea to check.