Announcement

Collapse
No announcement yet.

Jims 3 way speaker build

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • jimbones
    commented on 's reply
    Agree Dezzar. I didnt know that I am supposed to start by measuring each driver on axis. I will do that and save the files for when needed. This isnt my first project and I cant say how many revisions it takes to get right but its a lot lol. Im with both of you on that. Its important that when I do something I understand the importance as you have so clearly explained.

  • DeZZar
    commented on 's reply
    That's the offsets we can put in the model if you intend to listen directly on tweeter axis (which you usually would). But to achieve a good model each driver gets measured directly on its own axis as the starting point. That way you can fine tune the listening axis - you could make it midway between tweeter and mid if you wanted. Each driver should be measured at the exact same distance from baffle. It'll be important to try and at least get the speaker up onto a chair or something for that woofer measurement. If you are measuring from 3ft away you'll want the woofer to at least be 3ft from the floor. I know it might be difficult but it's just a necessary part of custom speaker design.

    rpb makes a good point. In my experience no matter how good the simulation is it's never given the final crossover first time. It just gives a very good starting point and helps provide a point of reference to confirm results and understand what's going on. Multiple iterations are usually needed. But getting the measurements and simulation as accurate as possible means you won't be chasing your tail with unexpected results.

  • jimbones
    commented on 's reply
    I think the three of us are circling around the solution and are very close so it is a matter of ME getting my crap together lol. I need to make sure my info is accurate and that we have all the info needed, I posted physical offsets below. I do not know how that relates to offsets done by the original method of measurements

  • jimbones
    replied
    So here are exact measurements
    Tweeter: X=Y=Z=0
    Mid X=0, Y=5.125, Z=1.75
    Woofer X=0, Y=25.625, Z=3.5

    But that means all my measurements need to be done on axis of tweeter not mid way between the 2. Correct?

    Leave a comment:


  • rpb
    replied
    There's many ways to do this xo. I hope my sims have offered ideas, if not accuracy. DeZZar, and others know the fine points of sims more than I. I just like tweaking the values. Any xo you try can be changed if the measurements show that it's not working as planned. For a while, it was hard to find coils, but now I see there;s plenty of them available in both high, and low DCR. How critical is the DCR to the bass extension? I put DCR estimates in my sim, but didn't look them up. I like the idea of crossing at 300hz since the woofer is positioned low, but I don't know how that sounds vs 400hz. I haven't kept any 3-way I assembled, so my experience is limited. On my 2-ways, in my room, I tend to like a level response. Others like a tilt. Some others like a depression around 3k. With a custom xo, you can have virtually anything you want, but you have to listen, and decide.


    My revised sim. (Remember, my offsets were made up, so this may not be accurate. It was fun though.) I like to round off numbers. Most of the values are not critical, so there's no reason to try exact values. Use as much, or as little of my sims as you need.

    Click image for larger version  Name:	revision tw.jpg Views:	0 Size:	313.8 KB ID:	1493165 Click image for larger version  Name:	revision mid.jpg Views:	0 Size:	275.7 KB ID:	1493166 Click image for larger version  Name:	revision impedance.jpg Views:	0 Size:	306.8 KB ID:	1493167

    Leave a comment:


  • DeZZar
    commented on 's reply
    Generally for gathering your raw measurements to run a sim you would measure each driver from precisely on axis out to 90 degrees horizontally (every 10 or 15 degrees). You wouldn't really measure at any mid points for this purpose as the simulation software can be used to define your final desired listening axis and it will adjust the responses relative to the listening axis and distance you define allowing a significant amount of flexibility in the simulation - but to this it is expecting specific on axis measurements per driver.

    It is a little odd that your tweeter measurement sort of drops off a cliff after 10K which may or may not have something to do with the off-axis midpoint measurement.

  • rpb
    commented on 's reply
    I used about .75", and 3". I think the woofer might be closer to 4". These are numbers I made up, not measured.

  • jimbones
    commented on 's reply
    OK so for my frd measurements the mic was midway between tweeter and midrange, I dont recall but in earlier posts someone said based on that the mid was 2+ inch and the woofer was 10.5. Then in later posts rpb stated he said the mid is recessed roughly 2 inch behind tweeter and the woofer 4 inch. I assume he is talking purely z axis where the other dimensions were between mic and source?? If I should measure again let me know

  • DeZZar
    replied
    In my sim I have the tweeter and midrange on the same axis as you said you took your measurement for each at the midpoint between them but I have your woofer as roughly 20 inches below this point. I've added the acoustic offset you advised - woofer is 100mm behind the tweeter and the midrange 57mm behind...

    I'm getting this from my sim:

    Click image for larger version

Name:	image.png
Views:	41
Size:	22.5 KB
ID:	1493132

    Click image for larger version

Name:	image.png
Views:	39
Size:	342.6 KB
ID:	1493133​​

    Leave a comment:


  • jimbones
    replied
    DeZZar I made slight modifications as I was getting a dip in response between mid and tweeter. couple of value changes as well as driver polarity. please see.
    Attached Files

    Leave a comment:


  • jimbones
    replied
    here are the tweeter files
    Attached Files

    Leave a comment:


  • jimbones
    replied
    there is some uncertainty regarding the files I am using. Here are the zma and frd for the woofer and the mid. I use a 4 inch set back for the woofer and 2.25 for the mid. tweeter in following post
    Attached Files

    Leave a comment:


  • DeZZar
    replied
    Here's what I get with the last setup you posted (assuming we're working with the same files)
    • You don't need that extra 4.7 on the tweeter
    • The midrange lowpass is better second order
    • I don't think you need the tank on the woofer. The extra resistor after 82 cap causes issues
    • Impedance is all over the place
    Click image for larger version

Name:	image.png
Views:	24
Size:	24.2 KB
ID:	1493117
    Click image for larger version

Name:	image.png
Views:	21
Size:	346.6 KB
ID:	1493119




    Here is what I would suggest instead:

    Click image for larger version

Name:	image.png
Views:	22
Size:	22.8 KB
ID:	1493118
    ​​​
    Click image for larger version

Name:	image.png
Views:	21
Size:	330.2 KB
ID:	1493120

    Leave a comment:


  • rpb
    replied
    The thing about a tank filter is that frequencies above the tank notch come back strong. When I simmed your woofer filter, there was woofer output around 3k that should have been way down. Try a second or third order filter. Or a damped third order like mine. You don't have to cross at 300hz like I did. If you have the 7mH coil, maybe change the mid filter if needed, and cross a little higher.

    My tweeter filter is weird. I was trying to raise impedance. I normally use smaller resistors on 2-ways.

    Leave a comment:


  • rpb
    replied
    Let me show you my tweeter, and woofer filters.

    Click image for larger version

Name:	tweeter filter.jpg
Views:	29
Size:	302.5 KB
ID:	1493112 Click image for larger version

Name:	woofer filter.jpg
Views:	27
Size:	313.8 KB
ID:	1493113

    Leave a comment:

Working...
X