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

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  1. #1
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    Gains at difent power amplifiers and diferent sinsivity at speakers

    HI,
    Please help me

    this will be my first attempt to biamp this speakers

    dbx electronic crossover 223s
    hafler dh110 preamp
    bgw 750 amp (230rms 8 ohm) gain knobs at amp
    hafler dh220 (100-120rms 8ohm) external volume control to change gain if needed buy dbx crossover have gain input and ouput

    4530 clone baffle
    18"electro voice evm18b series 2 woofer ,repaired hand made coil 16ohm no idea on sensivity
    2446j driver 16ohm original diapragm- 2350 horn
    3105 crossover 075 tweeter new not original diapragms 16 ohm

    electronic crossover frecuency cross - I supose 500hz but I open to any advice

    2446j
    Sensitivity: 111 dB SPL, 1 W @ 1 m on-axis on hornē118 dB SPL, 1 mW on plane-wave tubeģ

    evm18b original sensivity at 8 ohm was EVM-18B was 8ohm with a sensitivity of 99db(1w/1m) rated @ 400/800/1600 (im not sure)

    im lost here, I need help , a baseline ?

    I want to buy an usb micophone to use the rew program for some tools to help with this task.

    I supose with unknown info this is difficult
    only info that I have is for the driver 2446j 16ohm with 100rms 8ohm amplifier,

    thanks in advance for your help

  2. #2
    Senior Member RMC's Avatar
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    Eduardo,

    Quickly.

    Your amps are 8 ohm and drivers 16 ohm so the amps will deliver half the power rated (number of watts).

    The DBX223s already has Individual level controls on all outputs this helps in adjusting levels, experiment.

    I already suggested to you a crossover frequency of 700-800hz so you can have a compression driver protection capacitor for a 400hz roll-off.

    The power rating of the EVM 18B series 2 is 200 watts.

    Calculating all the gains and sensitivities could get complicated and be time consuming.

    I think you make it too complicated on you. The simplest way is to adjust the sound level of each driver by ear, listening and adjusting for acceptable balance between the drivers, meaning the sound levels blend well together (one not too loud vs others).

    In case you're not sure about your hearing then you can purchase a Sound Level Meter which will give you more objective db levels coming out of each driver, as long as you keep the same distance from each driver when measuring (e.g. 1meter).

    Sound Level Meters at say $100.+ should be enough for this, below this amount they rarely meet some standards and are more like kids toys.

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    Junior Member johnmgoss's Avatar
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    Thanks for this post mortron! The content is very valuable.

  4. #4
    Member macsic's Avatar
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    Hi,
    Difficult doesn't mean impossible, you want to buy a micro USB with Rew so go ahead, it's not really expensive. In my case this way helped me a lot with the possibilities offered by a DSP for corrections but without any correction tool what is the use of having REW ... Anyway, listening will always be the confirmation of success or not.
    Music is emotion.

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    Are there measurement microphone versions of USB mics? I've only seen cardioid mics targeted at podcasting and Zoom meetings rather than the flat response omni capsules needed for acoustic measurements. That said a very serviceable mic and mic pre/amp audio interface combo can easily be found on eBay for under $200.

    Quote Originally Posted by macsic View Post
    Hi,
    Difficult doesn't mean impossible, you want to buy a micro USB with Rew so go ahead, it's not really expensive. ...

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    Quote Originally Posted by Riley Casey View Post
    Are there measurement microphone versions of USB mics? I've only seen cardioid mics targeted at podcasting and Zoom meetings rather than the flat response omni capsules needed for acoustic measurements. That said a very serviceable mic and mic pre/amp audio interface combo can easily be found on eBay for under $200.
    at budget https://www.amazon.com/gp/product/B0...0e894f38f2fbd7

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    THANKS

    for your answers
    yes I will try, I already have de db meter, a I want to experiment with rew too

    what I need to do with db meter, I supose that with pink noise adjust de db of each driver, bass and misd needs to have same db ?

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    This is the dbmeter that I have
    Name:  WhatsApp Image 2021-08-09 at 17.08.14.jpeg
Views: 189
Size:  64.8 KB

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    I need to try to check this but, the 2446j driver is 100w at 500hz , 150w at 1000 hz
    if the hafler amplifier is 100w at 8 ohm, is like 50w at 16ohm, porbably is not enough ro handle the driver plus passive crossover plus 20w tweeter ?

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    An SPL Meter will tell you how loud the loudest sound is not the overall level of the passband in question. The most cost effective way to get useful level information about the passband would be an RTA app for a smart phone. Not a substitute for real measurement software but much more useful than an SPL meter.


    Quote Originally Posted by Eduardocastrejo View Post
    This is the dbmeter that I have
    Name:  WhatsApp Image 2021-08-09 at 17.08.14.jpeg
Views: 189
Size:  64.8 KB

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    Member macsic's Avatar
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    Quote Originally Posted by Riley Casey View Post
    An SPL Meter will tell you how loud the loudest sound is not the overall level of the passband in question. The most cost effective way to get useful level information about the passband would be an RTA app for a smart phone. Not a substitute for real measurement software but much more useful than an SPL meter.
    Good idea, I have Decibel X and Spectrum (all free) in my iPhone, you may know better ones but they will always be less precise than a calibrated microphone.
    Music is emotion.

  12. #12
    Senior Member RMC's Avatar
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    Eduardo,

    RE what I need to do with db meter, I supose that with pink noise adjust de db of each driver, bass and misd needs to have same db ?

    Yes about the same, can be small differences, but if you don't have pink noise you can still use music to get an idea, make it easy on you since you're starting at this. As you get more proficient with this and biamping you will refine your techniques (Rome was not built in a day as they say...).

    That db meter should be ok, follow the instructions and maybe use wider DBC scale instead of DBA if you have it. Its not really the absolute db numbers that matter here but more the relative levels, i.e. difference between each driver if any, e.g. one is 4 db louder or softer than another for gain correction purpose. Later you can use EQ to refine some things.

    RE if the hafler amplifier is 100w at 8 ohm, is like 50w at 16ohm, porbably is not enough ro handle the driver plus passive crossover plus 20w tweeter ?

    I wouldn't worry too much about this, you should have enough with 50W. Just remember a high sensitivity woofer has about 5-6% efficiency, but the 2446 has 30% efficiency!! A lot more, there's no contest, in normal use one would likely have to turn down the HF section gain if it was wide open. Usually need less watts for HF than for LF.

    Richard

    I wrote the following last morning for you, didn't have time to post it, had to go, so i'm adding it here now:

    After my initial post i realized you may need more help than i thought, that's fine, since you never biamped and asked for a baseline. In your situation and having an initial startup to do i would proceed carefully by bringing up the sounds progressively (in steps) one section only at a time. Better be safe than sorry.

    When everything is connected properly and turned off make sure all gain/volume controls are way down. With all level controls still down, now turn on your gear (amps last), including your music source. Next bring up preamp level to say 1/3+ of the way, crossover LF output levels around middle (or zero or unity depending what its called on unit), and bass amp gain about half way for now. Hear anything from LF cabs?

    Too loud or too soft adjust gain/level along the way for comfortable listening level, no need to be loud now. Next bring up slowly MF/HF section on crossover output levels to a perceived level that about matches the LF cabs level. Horn works?

    That gain structure isn't great nor final, its just to get you started with precaution. Now the real work starts in balancing the gain/levels (some more here maybe less there). Since bass amp gain was only half way its likely you'll need to increase it due to high horn sensitivity requiring less.

    The burden of providing gain/level should be shared logically among the gear in a system (usually not one item full gain while another is barely up). You need to adjust and experiment in fine tuning the gain load each component has to provide (preamp, amps, crossover). Sometimes when level is wrong you can either increase one or reduce an other (or a mix of both). Some require more than others, like big amps.

    So you play with this until its properly balanced and sounds good to your ears. You'll find the trick pretty fast. Try to remember or note the settings that provide the best outcome for you at this time.

    To keep things simple i didn't get into the amplifier rule of "on last and off first" which is good practice, specially with amps not having turn-on delay and instant off, that could cause noise or damage to speakers.

    Richard

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    Thanks a lot for your time

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    Senior Member RMC's Avatar
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    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...

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    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...

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