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  • #13765

    sb-woo
    Participant

    I built some 2-way speakers using dayton reference paper woofers. Just got the DATS V3 and tested them out. Surround speakers use 7″, center uses 6″ and fronts use 8″. All the tunings seemed to be making sense except for the 8’s. I dont have the data in front of me but they came out tuned lower than expected. The port is an uncut tube from parts express. 2.5×8.5 I believe and the box internal is just less than a foot cubed. About .94′ they tuned around 34 hz. The only thing different about the 8’s is the foam damping material on the inside back wall is higher quality thicker material with the 8’s. Any ideas as to whats going on? 

    Also, when testing frequency response with REW. There is a dip around 660 hz. It shows up on the DATS as well. The boxes are approx 9.25×10.25×18. The longest dimension is unbraced and the woofer lies in the center of baffle. Possible standing wave or cabinet resonance.. im not sure.

  • Confused

  • 123toid

    Administrator
    August 7, 2021 at 5:08 am

    @sb-woo

    Do you have any pictures?  Of the speakers front and rear along with some screenshots of DATS.  That would help a lot.  Also can you provide the model number of the driver you are talking about.  Right now, it is anyone’s guess.  But I will have to ask, is the port directly behind the driver?  Or is is up near the tweeter?


    Confused

  • sb-woo

    Member
    August 7, 2021 at 7:08 pm
  • 123toid

    Administrator
    August 7, 2021 at 8:26 pm

    @sb-woo 

    Let’s start off with the impedance.  This appears to be an issue with resonance. If you notice you have an issue at 660hz then again at 1200 and again at 2400. This typically indicates resonance.  Typically I would ask you about your bracing.  However, this is most likely port resonance.  If you look inside WinISD, that woofer when tuned to 34hz in that sized box will have a first port resonance right around 657hz. This lines up exactly with what you are seeing in your impedance graph. What is off is the size of your port. 

    Now whether that is an issue with measuring, not being broken in or an issue with Dayton’s T/S parameters, I couldn’t tell you.  But WinISD does predict a tuning of 37 with an 8.5″ port. 

    If you want to tune it higher (close to 37hz) you will just want to cut the port a little and keep testing until your target is met. This will also change your first port resonance. Which should make that resonance move up (closer to 800hz when you are tuned to 37hz). 

    Typically this really isn’t a huge issue.  It only changes the tuning F3 by about 1hz.  It’s not off by much.  If you haven’t got a chance to break them in yet, I would do that and then take another measurement.  


  • sb-woo

    Member
    August 7, 2021 at 9:16 pm

    @123toid I have heard you talking about port resonance, it’s not something im familiar with. But, apparently I need to have a better understanding of what’s going on. I also saw you designing your crossover on some software program and i was blown away with what you can do. Taking a manufactures frequency responce and resistance graph, plugging those in and working out the components. Seems quite complicated, but something I will be very happy to learn. I have really only messed with full range drivers and subs up till now and my understanding of crossovers is very limited but i can follow a schematic.

    Im not too concerned with the tuning of the boxes i have now. I always play with port lengths a bit to get them sounding good to me. My interest is definitely more about learning this stuff.

    This is the frequency responce i got from that speaker. I took these outside. Top one is a crude attempt at ground plane and bottom is with it about 7′ up on a ladder. Not the best but its really my first attempt at designing a two way on my own. As you can see there’s a problem at around 660 and more issues up higher. Not sure whats going on up there in the higher frequencies. 

    Sorry about the screen affects going on there. 

  • sb-woo

    Member
    August 7, 2021 at 9:30 pm

    Something else I found quite interesting.. the top response is the 8″ and the bottom is a 7″. Look how well they track each other from around 60hz to about 600hz.

     

  • 123toid

    Administrator
    August 7, 2021 at 9:32 pm

    @sb-woo 

    The best way to figure out what’s going on is to take individual measurements of each driver. By the looks of it it would appear that most likely what’s going on is the cone break up with the 8-in woofer is going into your Tweeter response. If you want, we can all help you designed a custom crossover from scratch. If you’re willing to take some measurements, we can walk you through it. If you do want to do that, I would suggest starting a new thread and that way we can sticky it for other people that might want to learn the same thing. 


  • sb-woo

    Member
    August 7, 2021 at 9:39 pm

    Also, this is the in room response of the 8″ (my front left) how on earth do I tame that mess!

    The upper frequencies cleaned up a bit though.. this is from listening position. 

    Second pic is full 5.1 system reponse.

  • sb-woo

    Member
    August 7, 2021 at 9:44 pm

    @123toid That would be Much appreciated!! 

  • sb-woo

    Member
    August 7, 2021 at 9:56 pm

    I’ve been awake for about 24hr. Gotta get some rest! Gonna try and start this new thread in the morning. Any suggestions as to how best to go about this?

    I can give a short but detailed explanation of what I’ve done with some pictures and we can take it from there…