Home Forums DIY Speakers and Subwoofers Hi, just a quick question about measurements

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    dameo182
    Participant

    I tried using my phone today to send the omnimic test tracks to a Bluetooth speaker, and as I was doing that I noticed that if I switched my phone to mono output that my response was slightly different to when I have it set to stereo. I usually use a little cd player and connect that to an amp using an aux in 3.5mm stereo jack lead, but it occurred to me that maybe my method was slightly wrong. I only ever measure one speaker at a time and have that connected to either the left or right output of my amp, I then use the short sweep mono track to do the tests (because I’m only testing one speaker is my reasoning). So my question is basically, am I doing that right? Or should I be using the short sweep left or right track (whichever corresponds with the output of the amp I’m using) rather than the mono track? Or should I be using a summing circuit to sum the left and right channels before it enters the amp? I feel like I’m confusing myself now, and it didn’t turn out to be that quick of a question either.. sorry 

  • Hi, just a quick question about measurements

    dameo182 updated 6 months ago 1 Member · 9 Replies
  • 123toid

    Administrator
    December 15, 2021 at 1:41 am

    When you setup your Omnimic you are supposed to set you mic to stereo and DVD quality 47Khz.  It usually comes up with a dialog telling you as much. I’ve never used it through my phone, so I can’t help much there.  But I would assume the stereo is closer.  It might be beneficial taking two measurements on stereo and mono and then running it through the laptop the way it is supposed to to see which matches the reference. 


    Hi, just a quick question about measurements

  • dameo182

    Member
    December 15, 2021 at 9:52 am

    @123toid 

    Yeah I have it set to dvd quality, it was a giving me an error message at first when I tried to change that, it kept saying another programme was using the mic and wouldn’t save the change, I had to uncheck the ‘allow enhancments button’ in the microphone advanced tab, after that it seemed to work ok. Next time I take measurements I will try doing a set in mono and then in stereo like you suggested and see which looks to be right, its hard to tell tbh because omnimic doesn’t come with something that can be measured as a reference, like the resistor in the DATS software, it would be nice to be able to check a response to say a tiny speaker that has a response graph, that way if it didn’t match up I would know something was off, as for the laptop, since I upgraded I haven’t run the test tracks through it yet, I don’t know if you remember but when I did my first measurements using my old one they were being coloured by the laptop and it’s put me off of using it.

    It’s mainly the fact that I’m running the tracks from a stereo amp into a mono set up for the measurements that makes me question which test track I should be using, it may not make much difference but I’m just trying to be as accurate as I can be so I can get the best out of my speaker designs

  • 123toid

    Administrator
    December 16, 2021 at 5:40 am

    @dameo182 

    That is a great point.  You have to disable enhancements.  With those on, it may not accurately measure.  You also need to make sure you have no eq set to your audio output.  For instance, if it is a soundblaster card, they can often be enhanced. Ie bass boost, virtual surround, etc.  If those are on, it will not send out an accurate sweep. 

    If you have any dayton drivers, they typically measure close to the manufacturers data.  You just need it on a baffle.


  • dameo182

    Member
    December 16, 2021 at 6:10 pm

    @123toid 

    Thanks, ill check that those aren’t enabled next time I take measurements, which should be soon as I have a few projects to get done, and yes I do have some dayton drivers, the pc68, they are for a small 2-way speaker I’m designing for bedroom use, so I can check when I take the measurements for the crossover design. It shouldn’t matter if they are in a box instead of just being mounted on a baffle should it? 

  • 123toid

    Administrator
    December 18, 2021 at 4:28 am

    @dameo182 

    It will if you are designing the crossover based off the measurements.  If you want to design the crossover, you need to design and build the box first. Then take the measurements inside the box. 


  • dameo182

    Member
    December 18, 2021 at 12:16 pm

    @123toid

    Last week I measured my father’s warfedale diamond 9.1 speakers as he wants me to upgrade them, I need to raise the treble slightly and upgrade the quality of parts for him, but you gave me the idea to check online for other measurements of those speakers to compare the results, and from what I can tell they match up pretty well. So maybe my setup isn’t too far off and I just have trust issues with my new laptop given the previous disobedience of my old one.

    I can post my results of that warfedale speaker if you’re interested to see them? 

  • 123toid

    Administrator
    December 18, 2021 at 5:00 pm

    @dameo182 

    Absolutely!  That would be awesome.  BY the way, I completely understand not trusting your measurements. We have all been there. 


  • dameo182

    Member
    December 18, 2021 at 10:27 pm

    So these are the measurements I took, at 16″ from tweeter level, the first is without the supplied grill that comes with the speaker, I took one with the grill attached and tbh it didn’t change enough to warrant posting on here

    Then I found a measurement taken by stereofile.com which I have used to compare, as I said above it seems pretty close, apart from the deeper nulls showing on the stereophile measurements. Maybe I had too much smoothing to show that up? Or because it’s a different speaker and microphone system?

     

     

    I’m not sure, but it seems that the over all shape of the response is mostly the same. I was impressed by the flatness of the speaker tbh, cant say the same for the inside though. Very little bracing and it echoes quite a bit during the knock test, also the parts are pretty cheap and I plan to upgrade those, mainly like for like apart from anything I change to raise the treble up a bit. Its also got dual binding posts which I can’t see a need for in a speaker that size, but I guess wharfedale know more than me at this point lol. anyway, sorry for the paragraph, I took spectral decay measurements too, well, I think I used the right waterfall for that, 

     

     


    First one with the grill on, second without.

    Also these are rated as 6ohms, so my dad matched them to a 6ohm amp, but it cuts out if turned too loud, after measuring with dats, I realised it’s probably because they are really 4ohm speakers and the amp can’t handle them, would you agree? I always assumed the lowest point of the line is the actual impedance? 

     

     

    I apologize for the bad quality of the last pic, It’s the only picture I managed to save of the impedance before I took the speakers apart 

    anyway I would like to know your opinion on the measurements I took, as in if you think my mic is likely to be accurate or if I need to do some tweaking etc

  • dameo182

    Member
    December 22, 2021 at 6:51 pm

    @123toidd

    Did you manage to check out my post above to see what you think about the accurasy of my setup? And before I forget, Merry Christmas,  wishing you all the best!