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Studio Active Monitors Speaker/Woofer Damaged buying equivalent one instead of original?

Discussion in 'Audio' started by ssyniu, Dec 19, 2020.

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  1. ssyniu

    ssyniu

    41
    0
    Sep 20, 2017
    Hi I have this studio monitors:
    https://www.alesis.com/products/view/m1active-620

    The speaker/Woofer is not working and I wish you to advise me on what specification I should look when buying non genuine speaker that would do the job instead of paying 69£ for original one?
    Ohm's And watt's and the size of the speaker are the only specification that are important?? if not what else I think the frequency response should be the same???What else please???The size of the Alesis genuine speaker is 6,5 inch ,8 Ohms and 65 watt's what else I need to look at to find good alternative to the original one??
    https://www.ebay.com/c/1505508508

    All the best looking forward for some advice.
     
    Last edited: Dec 19, 2020
  2. bikemech

    bikemech

    456
    40
    Oct 23, 2014
    Hi, i dont think you need anymore info, seems you have covered all bases, only thing i would do personaly is change them in pairs to be sure the balance is good,

    Pete
     
  3. ssyniu

    ssyniu

    41
    0
    Sep 20, 2017
    Hi Pete thank you for your answer.
    I found in the description of the woofer that actually the size of the speaker is 6 1/4":

    ( Woofer. 6 1/4” lightweight, magnetically-shielded, ultra-stiff polypropylene cone with rubber surround and high power handling voice coil ).
    I am completely lost now as I was trying to find one with this size (6 1/4") and all are 6,5".Is this is some sort of mistake or there are woofers with this size( 61/4")But I am unable to find even one???
     
  4. Audioguru

    Audioguru

    3,383
    727
    Sep 24, 2016
    A speaker has a long list of detailed spec's. Alexis probably do not list the speaker's spec's and the ebay speaker has absolutely no audio spec's and does not even say who made it (in their Chinese basement?).
    Buy a genuine speaker from the manufacturer.

    Whatever caused the original speaker to fail might cause the replacement to fail.
     
    bikemech likes this.
  5. ssyniu

    ssyniu

    41
    0
    Sep 20, 2017
    Hi have you got any Idea what might caused the speaker to fail???
    Ive bought four second hand cones (exactly the same) and I replaced one and its distorting as well so I am not sure if the replacement speaker is damaged or you are right and something inside is making this cones to fail.I have three more but I am afraid to try to fit another one so I won't loose another one ,or its a coincident that this one(replaced/second hand) is faulty as well.
    All the best
     
  6. Audioguru

    Audioguru

    3,383
    727
    Sep 24, 2016
    The cheap woofer burned out (?) because you played it too loud.
    I have stereo speakers I built with 6.5" woofers in ported enclosures and with dome tweeters. I never play them with more than 20 real Watts each.
    The Alexis 620 speakers say 100 Whats in the owners manual that might be 100 peak Watts which is 50 real Watts maybe at a horrible-sounding 10% or more distortion. Then the actual power is 40 real Watts at low distortion that is too much for a little 6.5" woofer.
     
  7. ssyniu

    ssyniu

    41
    0
    Sep 20, 2017
    "Then the actual power is 40 real Watts at low distortion that is too much for a little 6.5" woofer."

    How does that translate to the dB's???

    How many dB's to play them in 40 real Watts???

    Is it 46 dB??
    https://www.rapidtables.com/convert/power/Watt_to_dBm.html

    I was watching video
    ()
    on how to calibrate studio monitors and the guy in the video said to calibrate monitors to 75 dB's in small studio so mine are calibrated to 75 dB and when I am listening loud the loudest is 75dB is that too loud you think for this monitors??

    I have tested all (old and new) cones on the second (good/right) monitor.It showed that there was no need to buy any of the second hand cones as the old that I thought is damadged is working fine( the one that was distorting previously) in the left unit/monitor.So but when I put it back to the left one it sounded worst quieter and sounded like you put bunch of blankets over the monitor.I will upload the video its just take time to upload on the Vimeo.
    So again I have changed the cone to the "new one" and it worked ok and suddenly(after few minutes) volume dropped and it started sounding like the previous cone (like under the blanket) so I hit it with my hand and it brought back the good sound.Is it some sort of disconnection you think all the best I will post the video when its ready.

    Edit here is the video:
    https://vimeo.com/manage/videos/567025967
     
    Last edited: Jun 24, 2021
  8. Audioguru

    Audioguru

    3,383
    727
    Sep 24, 2016
    Decibels are usually used to measure sound levels, not power Watts. Every speaker design has its sensitivity listed in its detailed specs and measured in an anechoic chamber at a distance of 1 meter. Your (cheap?) speakers do not list any detailed specs.
     
  9. ssyniu

    ssyniu

    41
    0
    Sep 20, 2017
    "I never play them with more than 20 real Watts each."
    Ok So I don't get the part regarding watts how to adjust watts?
     
  10. Audioguru

    Audioguru

    3,383
    727
    Sep 24, 2016
    Since the amplified speaker has no detailed audio specs then nobody knows anything about it.
    If the amplifier power rating was truthful saying real Watts (maybe 40 real Watts) over a range of frequencies at a low distortion level, then play it for a moment at a loud enough level for you to hear the amplifier clipping. Then reduce the level a little (-3dB which is half the original power) and the loud parts will be 20 real Watts. But you do not know how much power will damage the woofer.

    Radio Shack sold a good sounding little two-way speaker, the Minimus 7 that was rated at 40W. I bought a pair on sale and blew up one 4" woofer.
    I looked inside and the blown woofer was stamped 5W.
    I ordered and installed a replacement woofer and it was also stamped 5W.
     
  11. crutschow

    crutschow

    115
    27
    May 7, 2021
    Speakers are not easily damaged by normal audio signals, but an amp failure that generates a DC output voltage can silently burn out the speaker voice coil.
    Check across the speaker leads for any significant DC voltage (above a volt or so).
     
  12. WHONOES

    WHONOES

    1,170
    319
    May 20, 2017
    Getting the correct drive units matters a lot.
    The cabinet containing you speakers has been designed with that specific unit in mind.
    For a ported speaker the volume of the cabinet and the diameter and length of the port are critical.
    The pertinent data that would have been used in the design is:

    Fs: This is the resonant frequency of the driver.
    Vas: This is the Volume equivalent compliance. Note that Volume is the volume of a closed box that would exhibit the same compliance and not how loud it is.
    Qts: This is the total Q of the driver and is derived from the electrical Q (Qes) and the mechanical Q (Qms).

    A sum using the above data is then used to calculate the box volume.

    Other sums are sums are use to calculate the port dimensions.

    Also, just because a speaker is listed as 8Ω impedance doesn't mean that it is actually 8Ω it could be less or more. The actual value will affect the performance of the crossover which will have been designed to reflect the actual impedance of the unit used. Further, the unit will have an impedance that rises with frequency and will have an impedance compensation network across it designed specifically for that one.

    Also the frequency response of the speaker used will have been taken into account when the crossover was designed.

    So, the answer to your question is................buy the correct replacement, to do otherwise is just a false economy.
     
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