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What tweeters?

Discussion in 'd.i.y.' started by Robert M, Feb 12, 2018.

  1. Robert M

    Robert M pfm Member

    I'm looking too make a DIY pair of speakers, I've got two volt b2500.1 drivers and I'm looking for suitable tweeters, I don't have lots to spend and I'm clueless at how to start making a crossover.

    Any help welcomed.
  2. Tony L

    Tony L Administrator

    Is that the one people used with the wonderful Decca Kelly ribbon tweeter to make the ‘Deccavolt’. If so that is what you want to do!
  3. demotivated

    demotivated pfm Member

    Just had a revise at the volt site. The 2500.1 is really a 3 way reflex, as it's 39Hz free air to about 1k, so not a closed box bass. They have always done a 2500.4 which has a clever cambric surround, flat into mid, and big throw. I imagine Volt specs are more reliable/realistic than most manufacturers. Win ISD says a 30 litre box tuned to 28 Hz for a domestic room bass curve goes down to 30Hz. It will be about 84dB SPL by the time you have rolled off above 300Hz and added 1 ohm series resistance for a beefy bass inductor/cables etc. Volt make the highest power transformer frame inductors, but I don't know who retail them. Falcon/Wilmslow sites just have the conventional domestic ferrite types. These are great for mid and treble eg 2 way, but the big transformer cores have much more headroom for bass filters. Tell us if you find them retail.
  4. demotivated

    demotivated pfm Member

    If you want a 2 way, I would investigate a wideband driver to cover mid/top. Maybe one of Stefan's Mark audio drivers 10/11cm in it's own box?
    Or the Bose replacement drivers that blue aran sell. These can do interesting things like a verical line array as they are just 1 ohm drivers.
  5. awkwardbydesign

    awkwardbydesign Officially Awesome

    Or a 2" Jordan, if you can find one. They will cross over down to 100Hz! But for power handling, higher is better of course.
  6. fatmarley

    fatmarley Registered User

    Passive crossover design takes time, money and patience. It took me a couple of years to get my first design somewhere near where I was happy. I should really go back to It because I'm sure with my added knowledge I could make them even better.

    The best way to design a passive speaker Is to model a box In software (WinISD Is popular) - Build the box and take frequency response measurements of the Individual drivers with a calibrated microphone - Take Impedance measurements of the drivers In the box and Import Into speaker design software.

    Active should be a lot easier but It's something that doesn't Interest me - I like the challenge of passive.

    Probably the safest bet and definitely the quickest/cheapest option would be to find a existing design that uses those drivers.
  7. orangeart

    orangeart KJF Audio Ltd.

    I get more and more customers doing this now, lots of golf are experimenting with a smaller wide band driver which go high very easily and are extremely fast in the midrange in a small (often sealed) box and them handing off to a woofer at 250Hz or so.

    Good driver that one although very difficult to find these days. The logical successor is the Alpair 5. Mark worked the JX 92 while he worked for Ted and the Alpair 5 is really an evolution of the tech. It's good out to 25KHz, much more excursion, MUCH lighter cone, no rear suspension. Well worth using anywhere you need a midrange/ tweeter that is happy to go pretty low too. It's my favourite driver at the moment, I use them in my little Frugel-Horn Lite kit which is good to 70Hz in room.
  8. Robert M

    Robert M pfm Member

    This looks like a long difficult road ahead.
  9. fatmarley

    fatmarley Registered User

  10. orangeart

    orangeart KJF Audio Ltd.

    It is, but hugely rewarding, it's often worth a hybrid approach, doing an active version with some cheap amps and a simple digital active XO to tune by ear with your chosen drivers and then at least you've an idea of what passive crossover you need to build, that way you can at least listen while you learn how to design a crossover.
    Robert M likes this.
  11. hp1

    hp1 pfm Member

    You could use those volts in a half active half passive 3 way system,ie active bass lp and lower mid upward s hp with passive mid lp and treble hp.

    that should get round most of the band pass pit falls and keep your sanity something like intact .
  12. demotivated

    demotivated pfm Member

    Yes, that would simplify some problems. The mid driver, bass rolloff [HP] is the most problematic in a passive 3 way. You want to use the driver down to it's lowest cutoff, but then you have the extra mechanical roll off that all drivers have at their low end so with the electrical filter it ends up a steep cutoff. Then you want to set the gain with resistance, but this screws up the low end mid damping, so you need a bigger mid box. It is actually easier to adjust the level down in a passive if the mid is over 6dB more SPL than the bass driver - less side effect.
  13. Robert M

    Robert M pfm Member

  14. fatmarley

    fatmarley Registered User

    The mid would work, but being fussy I'd worry about that dip centred at 1.5khz on the Volt. I'd personally be looking at crossing 500hz of lower with a bigger driver. Although I've never done It, I've heard people say that crossing a small mid driver, to a big one, at a low frequency sounds odd, so at 500hz I'd be looking at something around 5 or 6" (just to be on the safe side). I'm sure other will disagree with this but I have noticed It done with a few well respected speaker designers.

    The FaitalPro 5FE120 Is cheap and Is supposed to sound excellent. Just a shame It's so ugly.
  15. demotivated

    demotivated pfm Member

    I was just going to say the same, but I went off to find out what a d80 was. It looks like 8 inch bass not 10 and they use a pair of mid domes which might help the lower end. That mid dome looks great, but I would want an 8inch bass that was flat to 2kHz and no suprises higher up. The attractiveness of domes, apart from looking cool, is the built in back box which means simpler construction. Back boxes are a pain ITA unless you have easy woodworking tech. You generally want them to hang off the baffle which makes a big wobble mode, or stretch front to back which means you have to figure out how to airtight seal between 2 sides and it takes up total box volume.
    A manufacturer can stretch drivers to their full range to save cost because they can tweak problems when they research a design. A DIYer should really use a generous overlap of driver range so you can use simple xovers and get a more effortless sound than budget speakers. That 5" above seems just right and will only need about 4 litres of box.
    fatmarley likes this.

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