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Thread: Gains at difent power amplifiers and diferent sinsivity at speakers

  1. #16
    Senior Member
    Join Date
    Apr 2016
    I have used some practices similar to what's been described in this thread. I think my initial introduction was a "Gain Staging" document from Rane.

    To this day, I still find gain staging to be the most confusing thing. I cannot explain it to someone because I am not confident in my understanding.

    If you set the levels by ear... Does the balance stay consistent as one rides the input volume up and down, or would it change as you changed the output going into your crossover then amps? Is a voltage measurement the most accurate way to measure the outputs from the channels? And I've read people who say leave amp gains maxed, some others do not.

    Is there a hard and fast rulebook to go by for gain staging that answers all this? Or is it too gear dependent to be that simple?

  2. #17
    Junior Member johnmgoss's Avatar
    Join Date
    Aug 2021
    Thanks for this post mortron! The content is very valuable.

  3. #18
    Senior Member
    Join Date
    Aug 2017
    Averaging on an SPL meter would by definition be an average over time and will not provide information about the levels of other frequencies than the frequency or combination of frequencies that provide the highest sound pressure level. Assuming a fairly linear over time transducer as most loudspeakers are you could measure pink noise from a speaker driver for 24 hours and still have no more useful information about the spectral balance of the passband than if you measured for a few seconds. In terms of assessing the relative drive levels of different crossover bands in a multi amp sound system even a cheap smart phone RTA will provide more useful information than an expensive SPL meter. An even better solution is a transfer function measurement system for which even free software like OpenSoundMeter or REW are the bare minimum that anyone rolling their own speaker system and electronic crossover should invest in. The only expense there is a mic preamp audio interface and a measurement mic both of which can be had for under $100 and provide far better tools than JBLs best engineers had access to until the 1990s.

    Quote Originally Posted by RMC View Post
    RE An SPL Meter will tell you how loud the loudest sound is not the overall level of the passband in question.

    Its more nuanced than that, having two SLMs and one RTA. SLM is certainly not an RTA giving instantly level per frequencies, though you could do it on a number of spot frequencies with SLM, just longer.

    In peak mode you get the loudest, user choice, however set in average mode the SLM provides the average sound level readings, which reduces the influence of some peak in response. What i would call the "sustained level". Therefore you get a good idea of the overall level of the passband in question...

  4. #19
    Join Date
    Apr 2021
    At last some days free, I can continue with this project

    thanks for your help and patience

    I sold the dbx 223 and I bought a dbx pa2 (I love it).

    I never received the capacitors that I bought for mid-hi crossover🤦*♂️(3105)
    The capacitors are not cheap and I wondering with this money bought a small 40w amp for tweeters and convert this system to triamp 3 way speaker instead of 3 way biamp passive crossover at mid -hi

    also need help with new baseline for frecuency at croos over

    18” woofer 30- 500 ?
    2446j 500-10,000 ?
    075 7000-18000 ?

    thanks in advance

  5. #20
    Senior Member RMC's Avatar
    Join Date
    Feb 2017

    Looks like a plan to me.

    However i would use the 18" to 600hz since it remains or so within the 6db directivity index of the woofer. Then 2446 from 600hz to 5-6 khz so that you can have some overlap on each side of the latter crossover frequency with the tweeter. Therefore the 075 would cover 5-6khz and up.

    This is based on 2446 response seen, as well as assuming crossover slopes of at least 12db/oct.

  6. #21
    Senior Member
    Join Date
    Apr 2003
    Covington, Ohio
    Actually you may want to try under lapping the crossover frequencies some, that will help with the phase response and frequency response around the crossover point.

    Keep in mind the crossover frequency and acoustic crossover frequency are rarely the same.
    Depending on how you balance the levels say between the woofer and the 2446 with a electronic
    crossover frequency of 600hz the acoustic crossover point could be upwards to 1000hz.

  7. #22
    Senior Member
    Join Date
    Apr 2003
    Covington, Ohio
    Here's a link to a post I made about acoustic crossovers.

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