›
Please review the site Rules, Terms of Service, and Privacy Policy at your convenience. Rules, TOS, Privacy
Get familiar with the reaction system: Introducing the Reaction System

First Design Walk Through

D1PP1ND1PP1N
edited August 2016 in DIY
Ok gentlemen I am going to attempt my first design with the SB26STAC tweeter and Tang Band w4-1720 4" woofer.
I want to shoot for a crossover point of 2000-2200. The tang band woofer has wonderful low end but gets over tasked
at high volumes playing into the midrange and my goal is to alleviate the burden of having to play from 20hz-4000hz
and drop it down to 20hz-2000hz. From what I read in Bagby's post about the SB26STAC going below 1900 on the sb26
introduces elevated distortion levels so I wanted to keep it above that.


The process I don't have full comprehension of. So I wanted to ask for some input. Here is what I understand so far.
Craig S was nice enough to run me through this for an hour or two a few years ago but my memory is foggy.

If any of this is wrong or can be add too I would appreciate any insight.

1) Take FR measurements on tweeter and woofer on each speaker (A and B
 
  A) Take near field FR measurements. Mic height at Tweeter level. Approx 1/4" from tweeter. Measure Tweeter and Woofer individually (without moving   mic from TW. height)
 
  B Take Far Field FR measurements. Mic height at Tweeter level. Approx 20-27 inches away from tweeter (IS this correct?) Measure Tweeter and Woofer individually (without moving mic from TW. height)
  
  C) I faintly remember taking both drivers measurements at the same time but I could be wrong (yes or no?)

2) Take DatsII zma measurements in box (this im a tad unclear of; as dats gives me random measurements at times)

   A) Take dats measurements on tweeter and woofer in box for A and B

3)Import these measurements into FRD blender (never used this program before)

4)Import blender file into PCD along with individual non blended measurements

6)Find Acoustic centers (I can't remember how to do this) but think I remember it was based on when you take both measurements at the same time.

7)Start to fiddle with PCD

«134

Comments

  • PWRRYDPWRRYD
    Hi Mike.

    There's a lot in your post to respond to.  How about we just start at step one and people can chime in step by step as you proceed through this design?

    Once I get the drivers mounted in the actual enclosures with wires running out to the real world I use DATs to measure each driver's impedance curve.  Hook up the allligator clips to the driver under test (DUT) wires and hit the "Impedance Sweep" button and let it do its sweep.  Then hit file/export/save as a .zma and give it a name.  Something simple like "Tweeter A".

    You don't have to measure the impedance first, but I do because if I have an air leak or weak faston connecter it likely will show up in the curve and I can correct it before moving on to the more involved frequency response measurements.
    ani_101D1PP1NJasonP
  • D1PP1ND1PP1N
    Sounds good Craigame and thanks.  I should have but dats first I remember that was the first thing we did. It is a vented cab so I should be able to verify my tuning frequency is correct as well. I think I shot for 60hz. 

    I'm stuck between wanting to veneer or finish the baffle to start measuring. Probably should measure them so I have more time to fiddle with the design. 
  • JasonPJasonP
    PWRRYD said:
    You don't have to measure the impedance first, but I do because if I have an air leak or weak faston connecter it likely will show up in the curve and I can correct it before moving on to the more involved frequency response measurements.
    Also, in my experience issues with cabinet damping will show in the sweep as well. When I have on occasion forgotten to properly treat the walls around the driver I'll see small blips and ripples in the impedance sweep between 150 and 550 hz.
    greywarden
    = Howard Stark: "This is the key to the future. I'm limited by the technology of my time, but one day you'll figure this out."
  • jr@macjr@mac
    The other thing that measured vs. simulated in-box impedance sweeps will show is how often our simulations bear no relation to the reality of box tuning. Not all wall linings are created equal, for example. The Blackhole5 eats up a lot of space inside a cabinet, fiberglass less so. You can cut ports shorter if you "corner" load them - this will only show up in simulations if you can predict the correction factor for the walls acting as part of the port and that is a lot of maths and edumacated guesswork - easier to make an assumption and cut them 10% short. 


    I have a signature.
  • jhollanderjhollander

    Also watch out for air leaks.  I've been burned more often than I care to admit.

    As I posted the other day I've had a string of port issues where I had to figure out how to shorten the port.

     John H, btw forum has decided I don't get emails
  • D1PP1ND1PP1N
    I got the baffle edge treatments done and picked up some gasket material. I gotta stuff the cabinets, mount drivers and run wires. I will get measurements this weekend. 
    JasonP
  • jhollanderjhollander
    That is sweeeeet! What wood is that?

    BTW I was able to help Tom Z by trading FRDs and walking through the measurement process. I'd suggest dong that with one of the "fellows" here.  It's so much easier to get immediate feedback as you go.
     John H, btw forum has decided I don't get emails
  • D1PP1ND1PP1N
    The baffle is Paduak the flame one is chen-chen and I'm not sure what's on the left anymore. I forgot what is was. 

    Ok I'll try to post my measurements here and if there are any takers I can email the files to see if I have everything setup correctly and measured correctly. 
  • FaceFace
    Paduak is very nice stuff!  The dust is bit nasty, I hope you're wearing a respirator.  Also, keep it out of the sun or it will turn brown within a year.
  • JasonPJasonP
    That baffle is looking terrific!
    = Howard Stark: "This is the key to the future. I'm limited by the technology of my time, but one day you'll figure this out."
  • D1PP1ND1PP1N
    I have a respirator but wasn't wearing it, I have a nice Dust collector with a pleated filter that takes care of most of everything. 
  • ani_101ani_101
    May I ask, why rear mount t the woofer? It will in trade z difference even further. But it is looking good
  • D1PP1ND1PP1N
    Purely cosmetic reasons. 
  • greywardengreywarden
    Nice baffle geometry, what's that like 1/8" between the chamfer and the tweeter?
    deadhorse - leviathan - harbinger - shockwave (wip)
  • PWRRYDPWRRYD
    Have you measured in box impedances yet?  Come on Mike!  Get going!  I wanna move on to step 2 you bum ;)
  • D1PP1ND1PP1N
    This weekend for sure. Been too tired allike week. My wife's car broke down so I've had to drive her to work in the mornings and I don't go to bed until 2am-4am she leaves at 7am so I have been dragging ass all week. I'm going to get my drum sander today. About 2hour drive each way. 

    Grey, yeh it's 1/8th maximum. One might be a tad deeper because the large 45 bit caught once and shot the baffle across the garage. 
  • jr@macjr@mac
    D1PP1N said:
    One might be a tad deeper because the large 45 bit caught once and shot the baffle across the garage. 
    I hate when that happens - around here it usually results in cursing and a switch from wood working to drinking heavily.
    jhollanderPWRRYDS7910greywardenJasonPD1PP1N
    I have a signature.
  • PWRRYDPWRRYD
    Same around here JR.
  • isaeagle4031isaeagle4031
    I dont drink, but will when that happens!
  • D1PP1ND1PP1N
    Ok I got everything mounted up and ready to measure. When I attempted to use dats it is reporting that the box is too large. Was I supposed to take free air T/S parameters before mounting them to the box? 
  • D1PP1ND1PP1N

    This is the error window I received. If I need to remove the woofers for this would it be better for me to just do the omnimic measurements before removing them? It's kind of a pita to remove rear mounted woofers lol.


    The cabinet is 6" W  X 10" H X 11.75" Deep with 3/4 inch material. I was shooting for like 56-60 vent tuning frequency with 2x 1" round ports I don't remember the length but i think less than 5 inches.




  • isaeagle4031isaeagle4031
    Your tuning looks spot on to what you wanted. In DATS, run the impedance sweep and not the free air measurements. 
  • ani_101ani_101
    Yep look for the valley for tuning, usually you need to trim the port, but if it is close enough then it is good.
  • kennykkennyk
    Not sure if the added mass method is OK with the speaker in the box?
    ............. could you hum a few bars.
  • jr@macjr@mac
    kennyk said:
    Not sure if the added mass method is OK with the speaker in the box?
    Nope - but if he stuffs the port and closely calculates actual volume of the (now) sealed enclosure - he can definitely use the closed box method for calculating Vas. 

    Speaking of, I really need to build several test enclosures for exactly this purpose. David Weems told me to do it that way 20 years ago, and he wouldn't lie. 
    I have a signature.
  • isaeagle4031isaeagle4031
    kennyk said:
    Not sure if the added mass method is OK with the speaker in the box?
    Nope, one or the other. When using the box method, the enclosure has to be sealed.
  • kennykkennyk
    Well, take off the baffle and use the added mass method.
    ............. could you hum a few bars.
  • PWRRYDPWRRYD
    All that is used for is to measure Vas.  Your enclosure is already built.  A little too late for that :)

    Like Chuck said, you only need to run an impedance sweep on each driver to use in PCD.  That setting un DATs makes no difference for that.
  • D1PP1ND1PP1N
    Ah, sorry im dumb, i knew i only needed impedence measurements maybe i should try working on design stuff at 3:12am after getting up at 8am with 5 hours sleep lol.

    I've got the the Impedence data. The tweeters appear a tad different however one is brand new and one was used for testing and minor break in. Hopefully that is the tiny difference.
  • D1PP1ND1PP1N
    My questions thus far on taking omnimic measurements.

    Questions on near-field measurements
    1) Do I just take 3 measurements per speaker nearfield?
      (A)Tweeter about 1/4" away
      (B) Woofer with mic position the same at Tweeter level
      (C) The Woofer Nearfield about 1/4" away. (since woofer is rear mounted this may need to be altered but I don't know for certain but my #2 question refers to this)

      If anyone cares to expand on the reasoning behind this it would be appreciated.

    2) As far as distance for measuring nearfield is 1/4 inch away from the tweeter suitable and do I keep the mic position exactly the same for woofer (distance wise) if I just lower the mic it will be about 1-1/2" or 1-3/4" away from woofer nearfield.

    Far field measurements

    1) Do I need to use 1 meter or can I go a little less distance wise?

    2) Do I need 3 measurements per speaker on this as well at Tweeter height @ X distance
      A) Tweeter   B) Woofer  C) Tweeter+Woofer

    My understanding is that having these 3 helps determine the Z-offset

    Thanks in advance.

Sign In or Register to comment.