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Unit Used to Measure Frequency Response?

Discussion in 'Amps and Cabs [BG]' started by Freakin Idiot, Sep 5, 2005.

  1. What is it that people use to measure the frequency response of an amp? I'm assuming you can start out with a microphone, coupled with some sort of way to analyze it, but can this be done with just one unit? Or is it a computer program?

    I'm very curious because my dad's going to give me some stereo speakers and the ones I have now are crappy KLH speakers. They have a wooden cabinet though and might be suitable for a portable bass rig if I swap the drivers and get a good crossover. They have a 10 and a 6 inch speaker in them and have a vintage look what with the twine-like speaker covers. And then there's the matter of the horn, but that's a different story...
  2. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    You can use a Real Time Analyzer (RTA for short) along with a calibrated microphone.

    RTA's are useless for testing the response of a cab/speaker unless you use a CD with Pink Noise to put through the system.
  3. Where would I find these items?
  4. Tash


    Feb 13, 2005
    Bel Air Maryland
    Wouldn't a tone generator pushing a single frequency sine wav work also?
  5. It would work. It would just take you a while to cover the audible frequency range. With pink noise & the wonders of modern technology... you can do it all at once.

    As for where you obtain a sound analyzer... you could purchase your own (Type 1 Sound Analyzers like the Bruel & Kjaer 2260 run at about US$20,000 :eyebrow: ). Or hire one (around $300/hr is the going rate here in New Zealand...)...

    Or you could get yourself a cheap mic, download a signal generator off the net, play it through your cab, record using the sound card on your computer and use the FFT function in something like CoolEdit...
  6. Holy crap! Then how am I supposed to know what driver and midrange to get for these cabinets? Do I just give the dimensions?
  7. Do a search here for "cabinet design" or similar, and you'll get some idea of what is involved. It is discussed quite a bit...
  8. Yeah. I'm seeing lots of good stuff, but these cabinets are exceptionally small. 12" wide 8.5" deep, 23" tall.

    I also made a mistake on the speaker size. The largest one is 8".

    This is quickly starting to become the subject of another thread. But before this thread gets lost, do guys think its possible to get a decent sound out of these given their size?

  9. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    You can get CD's of Pink Noise that are specifically made for this kind of testing. You should be able to buy one for about $10.

    For other kinds of RTA's, there are quite a few that are software based that you can run on your PC. Just add a calibrated mic and your set.
  10. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    In your bedroom yes. For gigs, no.
  11. Since your are posting to this thread, I assume you have a computer, and probably a sound card.

    TrueRTA makes a nice software package for Windows. Price is Free to $99, depending on the features you want. The free version will probably do what you need. The free version comes with a pink noise generator.

    Behringer makes a measurement mic for cheap. It does a reasonably good job and is fairly accurate. It is a bit noisy, but big deal.
  12. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Short answer: No. But then again, define "decent."
  13. Something that sounds better than my way-too-portable Ibanez 20 watt practice amp. I recall seeing (and playing) an AccuGroove with something like an 8 and two 6 inch speakers with a tweeter at my other music store. Sounded pretty good for it's size...but then again it's AccuGroove. It's actually still sitting there for a few hundred bucks.
  14. Monomer


    Jul 22, 2005

    you can also make your own measurment mic setup, for around $20 and some time.

    and you wouldnt need the B*.
  15. I use an active Rane measurement mic.

    The requestor was looking for cheap, hence the B-word. I own no B-word equipment.
  16. By the way...they're unported...