Home Forums DIY Speakers and Subwoofers Argh!!! Choosing Drivers Reply To: RE: Argh!!! Choosing Drivers

  • ajc9988

    Member
    April 8, 2021 at 5:10 pm

    @deadeye – I actually spent a lot of time compiling data and making my impressions of the data from the frequency response graphs, including off axis. Some companies were excluded due to them not having off axis data (looking at you Tang Band; just give more info because I “hear” you are great (horrible play on words)).

    As such, for midrange, there are two groups of speakers you would want to look at: mid woofers and lower ranged tweeters. Make no mistake, you will need a tweeter above those, as they both only go up so far.

    For lower ranged tweeters, I primarily found Peerless and Wavecor to have a LOT of offerings in this frequency range worth considering. I have my spreadsheet setup so I can see which frequency range I would use it at, which the company recommends, the SPL (two columns, one for 2.8V, one for 1W), the Nominal Impedance, the Pe RMS rating (not to be confused with Rms, which is a different category), the diameter (both baffle hole and overall) and then the calculated beaming frequency according to the equation F=(2*c)/(pi*D) with the frequency equaling 2 times the speed of sound divided by pi multiplied by the diameter (with the diameter, if not provided, being the baffle cut out, not the overall woofer size, as that includes non-moving metal). Considering 343.68 is in meters and I am using mm for the speaker dimensions, I divide the cone diameter by 1000 to get the beaming frequency. You could also multiply the 343.68m for speed of sound by 1000 to get the same result.

    I then also use a cheat sheet I found ( https://www.jdbsound.com/art/frequency%20wave%20length%20chart%202013.pdf ) to figure out the number of inches for a full wavelength. I then use the radius (diameter divided by two) of each driver added together to check if I can get them close enough to cross them within one full wavelength.

    Arguably, you might look more at the Morel MDM 55 and CAM 55. Half the price, similar frequency response.


    Aside from those, I have a couple midrange woofers tucked in accidentally to the Woofers tab of my spreadsheet, but generally, those are the mids that I would consider that are not too expensive, but still great performance (if their graphs are correct and in the ranges that I figured for them).

    In fact, if you want you could create this as a 3-way and add the Dayton Audio ND13FA-4 (granted, 4 Ohm instead of 8 Ohm, so you will have to deal with that), you could fill out the areas above the Peerless if you feel the highs are not enough. This would be around 6,000Hz crossover. Otherwise, you could use an ND20FB-4 as well.

    But evidently the frequency will also depend on the order of the crossover, just to avoid the Fe on the fall (which avoids overheating and overworking the tweeter).

    So start with a spreadsheet of driver specs. Separate them into their categories like this

     
    Once you have the information mentioned above (mine also has all the information needed to be added to WinISD for modeling, meaning the T/S factors from the mfr), you then start with looking for your main woofer. Then look for a midrange tweeter or a mid woofer that would cross well with the woofer (if possible over 1200 to avoid higher voices playing out of one speaker and lower voices driven by the woofer, but that isn’t a real rule and 800-1000 is realistically fine), while having a high enough range before the off axis splits to cross with the higher ranged tweeter. Then, when you have this, you can start designing the box size by figuring out the volume the Woofer(s) need. I still do not know how to calculate having woofers of different sizes for the necessary volume (tweeters are often sealed and/or do not have large requirements on volume, etc., so less worried of those in the same enclosure space in a cabinet). In any case, then check baffle diffraction with the front shape and figure out the dimensions from there.

    If there is anything I missed, please let me know.

    Edit: on those lists I still need to move some drivers around, so, for example, the 5 3/4″ Wavecore WF146WA05 needs moved to the woofer tab, as does possibly the WF118WA07. I am still debating is low 2000s is enough for the mid or just call that a woofer if the lower frequency is enough. If it hits (or is serviceable on off-axis) to 3000+, then it is a good mid. Lower playing tweeters really fill that role well.

    Reply To: RE: Argh!!! Choosing Drivers