Home Forums DIY Speakers and Subwoofers Response Graph

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  • #9545

    richardbmw
    Member

    How do you guys get a response graph of what a multi driver speaker will sound like?

    I’ve tried looking at a few bits of software, but they all seem to fall down when you try to input the tweeter t/s parameters as there is no vas.

  • Response Graph

  • bjaurelio

    Member
    August 12, 2019 at 9:18 pm

    I’m a little confused on what you are trying to do. If you’re trying to simulate a a box model for a particular driver, you don’t need to do that for a tweeter. Unless it’s an open back ribbon for dipole, tweeters are enclosed systems. Woofers can be modeled, but you want to measure the T/S parameters of your drivers as they are often different from the specs you get on a website. Online specs for most drivers will get you in the ballpark to know what you’re dealing with, but some can vary quite a bit. I measured a pair of 10″ Hsu subs for a project for my parents over the weekend. It changed the design quite a bit by requiring the box to go from 2.5 cubic feet to 3.5 cubic feet. At the same time, the F3 dropped from around 30 Hz to around 25 Hz.

    It sounds like you want to create graphs of each driver individually from a box model and then combine multiple box model sims into crossover design software. When you get to crossover design, you have to measure the tweeter and any mid and/or woofer all in the box to do crossover work. That’s the only way to have a reliable starting point from which to design the crossover. 

  • richardbmw

    Member
    August 12, 2019 at 10:14 pm

    @bjaurelio

    Essentially what I’m trying to do is see  a rough combined response graph of a 2 way speaker before I buy the drivers. 

     

  • bjaurelio

    Member
    August 13, 2019 at 12:43 am

    @richardbmw

    Before you buy drivers that you plan to use together, all you need to look at is that you’ll have sufficient overlap in the usable band for each driver. The crossover will handle the combination of the drivers and depend on their spacing and alignment on the baffle. 

    For the tweeter, usually the crossover should be no lower than 2x the Fs. If using a waveguide, you can get away with going a little lower. For the woofer, you want to make sure it doesn’t become too directional at the crossover and any breakup modes are outside the frequency range you intend to use. 

    What tweeter and woofer are you looking at purchasing?

  • 123toid

    Administrator
    August 13, 2019 at 4:37 am

    @richardbmw

    Do you have Xsim? or Passive Crossover Designer?  Either would be a good place to start.  In these you can import your FRD and ZMA files. to get your summed response.


  • richardbmw

    Member
    August 13, 2019 at 8:23 am

    @123toid

    Yes, I have both of those.

    Just watching through Ryan’s guides again to see if it sinks in this time.

  • 123toid

    Administrator
    August 14, 2019 at 6:25 am

    @richardbmw No worries.  If you need help, let me know and we can jump on discord sometime and see if we can figure it out together.


  • bjaurelio

    Member
    August 15, 2019 at 7:16 pm

    A crossover simulation with manufacturer frd and zma files aren’t going to tell you much. There’s no baffle step in the measurements, no way to determine z offset, and your own measurements may be quite different, especially the woofer response based on the final box design.

    Before purchasing drivers, all you need to know is that there’s sufficient overlap in the usable passband. The usable passband is where there’s a relatively flat frequency response with no issues in the off-axis response. If you have that, the drivers can play well together. Determining how they will do so is for the crossover design process with your own measurements.

  • richardbmw

    Member
    August 16, 2019 at 7:56 am

    I am making a small 2 way bookshelf speaker. I picked up the following drivers.

    http://www.loudspeakerdatabase.com/Peerless/BC20SC15-04

    http://www.loudspeakerdatabase.com/Peerless/SDS-P830855

    Being in the uk, there isnt really a place like parts express, so drivers area bit harder to come by.

    Ordering from parts express costs quite a lot once shipping and taxes have been applied.

    As an example, the shipping on a pair of Tang Band W5-1138SMF 5-1/4″  costs $38

  • bjaurelio

    Member
    August 19, 2019 at 7:33 pm

    Those should work with about a 2.5k crossover point. Once you get them mounted in a speaker, your measurements may result in a different natural crossover point, but I think that would be a good general target. You can see the rise in frequency response on the tweeter from the built in small waveguide that allows you to get away with less than 2x double the Fs. 

  • richardbmw

    Member
    August 19, 2019 at 7:39 pm

    @bjaurelio

    Thanks for that, this is where I got to on Xsim, not sure about the impedance side though.

  • richardbmw

    Member
    August 21, 2019 at 7:41 am
    Posted by: @richardbmw

    @bjaurelio

    Thanks for that, this is where I got to on Xsim, not sure about the impedance side though.

    Scratch that, I had the wrong drivers files loaded.

  • richardbmw

    Member
    August 21, 2019 at 7:43 am

    This is what it looks like with the same xover components and the correct drivers.

    A bit more work required I think!!

  • 123toid

    Administrator
    August 21, 2019 at 3:17 pm

    @richardbmw

    Not a bad start, You will definitely want to add a zobel to the woofer after the crossover.  That will help bring that peak down.  Did you add a z-offset on the woofer?  You might also want to crossover a little sooner.  When you look at the the SDS resonse, you can see the off axis starts to diverge after 3Khz.  So anything after that, you might start to have beaming problems in that area. 


  • richardbmw

    Member
    August 21, 2019 at 3:56 pm

    @123toid

    I have had a little play with it, I’m not 100% sure what a zobel is or what it does.

    I added what I think is one and the graph looks far better.

    I’m still not sure what the impedance graph should be

  • tvor-ceasar

    Moderator
    August 21, 2019 at 5:33 pm

    Just for reference, take a look here: https://www.v-cap.com/speaker-crossover-calculator.php for a bit of information on a number of different aspects of cross-over types and add-ons. Scroll down to Zobel and click additional information. That should help explain things. I’m sure the software you are using has this capability, but I thought this might help.


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