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Adding a horn?

Discussion in 'Amps and Cabs [BG]' started by Mykk, Feb 6, 2013.

  1. Hey guys,

    A few questions regarding adding a horn to a cab.

    The cab has two 8ohm speakers in parallel, the high frequency roll off from the speakers is around 3K5.

    The cab is 4ohms, the readily available crossovers and horns are rated at 8ohm. (I'm looking at the Eminence line of HF products)

    Is it best to run a 2-way crossover and split the signal to the woofers and the horn. Or can I keep the speakers full range and just wire a L-pad, High pass and horn in parallel?

    How is the HF impedance going to effect the total impedance of the cab?

    The cab currently has two 500w woofers, the crossovers I'm finding are in the 400w, horns in the 80-100w range, and L-pad at 100w. All of this seems like a mismatch, unless someone could shed some light on the parts I'd need to finish the project.

    What I'd like is a 2-way or high pass 3k5 crossover point, L-pad, and horn that will work in a 4ohm 1000watt cab.

    Thanks for you help TB, yet again. Cheers ~Mykk
  2. bumps
  3. Look Here:
    then here:

    This is a basic introduction and plans for an easy high quality DIY crossover resource and parts supplier. Any questions you may have along the way in the design process some here at TB can comment on, plus Parts Express has its own design forum for help. This is the easiest and cheapest way to get a high power 2 way or high pass crossover at 3,500hz.

    I personally recommend 12db/octave designs for most musical instrument speakers.
  4. This coil:
    and this capacitor:
    or any with similar values will make a 12db/octave high pass crossover at 3,500hz for the horn. Note that the cap is a 8.2 where the calculator specified an 8.039. You have to get as close as you can but it is often not possible to get exactly the right size. Also all caps have a range that they will operate within and are virtually never the exact value (such as +20/-10%) so get as close as possible. There is a 8.0uf cap here: http://www.parts-express.com/pe/showdetl.cfm?partnumber=027-884 but it is very expensive (so-called audiophile quality, not worth the high price IMO...) so I recommend finding a nice 8.2uf value and making the thing yourself. If you can't solder get a friend that can to help.
  5. The L pad is a bit more difficult (costly) for a 300 watt plus crossover, consider a multi-position switch to drop the sensitivity in steps by adding an increasing resistor network to quiet the horn when needed. This is very workable and much cheaper. Again IMO design for 3db steps per switch position.
  6. Another good crossover resource:

    Use the speaker attenuation program to design the step down switch for the horn. It will provide the correct resister values for it to work correctly.
  7. Thank you Bassmeknik,

    Could I get away with wiring a 8ohm high pass & horn & 100w L-pad in parallel to my woofers?
  8. I like your step down idea.
  9. IMO the horn will not likely see 100 watts as it is crossed over at such a high frequency (3,500hz) so a 100 watt L pad should work. I'm not sure about the impedance mis-match (using an 8 ohm horn with a 4 ohm woofer section). Perhaps another TBer will come along with experience here. I calculate the difference in sensitivity between the woofers and the tweeters and create fixed attenuation that will give as close to flat response at the crossover point as possible. Then control the highs with the treble control on my amp for my DIY monitor wedges and PA tops, I am not a fan of using horns or tweeter/midrange drivers in my stage bass rig so I don't use L pads in anything... I design my crossovers for as close to a seamless transition from woofers to tweeters as possible. There is considerable differing opinion on this subject and I am not college educated here just a dedicated DIYer so be prepared for different opinions when researching this subject. I just took it all in and charted my own course, that is my crossovers are more Hi-Fi in design in that I won't cut corners to save money by using 6db/octave designs and I never run a high pass on a tweeter without the corresponding low pass on the woofer(s) like MOST cheap MI speakers I have had the pleasure of repairing... I make no apologies for myself just after 45 years of doing this as a hobby I am not an expert, just a motivated bassist that took acoustics and the physics of sound reinforcement as a hobby at the age of 10 when I first picked up a guitar and kept learning as much as I could.

    My favorite book on the subject is a very complete volume on all aspects of sound reinforcement and will take some time to read but is a magnificent resource for all who own and operate musical instrument gear: http://www.musiciansfriend.com/book...orcement-handbook-second-edition?src=3WWRWXGP

    Costs a bit at $35 but it is very thorough and will be used for many years to come.
  10. will33


    May 22, 2006
    The 100 watt horn driver and l-pad will be fine. There just isn't that much content/energy in the upper frequencies, the majority of power demand is in the lows.

    FWIW, most bass cabs just use a 50 or 100 watt tweeter and highpass only filter. The woofers are run fullrange and are losing response by the time the tweeter picks it up. Your cab will still be a nominal 4 ohm cab. The tweeter won't really affect the impedance in any meaningful way as the woofers impedance is rising quite high up there anyway.

    bassmekinik has you covered here.
  11. Bassmeknik, thank you. You don't need to justify yourself to me. I trust you, and your years of experience. I appreciate the links, I'll order my parts from there once I'm comfortable on my parts selection.

    Will33, thank you too. That is very helpful and the info I needed to move forward on my project.