Blog Forums DIY Speakers and Subwoofers I need an order of operations.

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    • #14855
      opulentone
      Member

      Oh wise and epic @123toid I have come to you with a question. 

      I have a set of ROKIT Powered 8 speakers with blown amps that are too expensive to fix. I would like to convert them to passive speakers in the same cabinet that they’re in now. 

       

      I know generally what I need to do but I could really use an order of operations. Like measure this with this, then this with this, export this file to this other program, then do this. 

       

      I have REW and XSim. I have a umik. I have DATS. I feel like I have everything I need except a mentor to smack me in the right direction. 

       

      Thanks <3

       

    • #14857
      ajc9988
      Participant

      @OpulentOne – Well, you have what you need. Hook it up to each driver separately and run the DATS for impedance for each driver. Export it. Go to REW. Set up your microphone. Do your frequency sweeps separately for each driver. All of this while in the enclosure. You now should have your measurements. You then go into XSim and setup the layout. You then select driver 1 and right click and select tune. Import the FRD Response File and ZMA Impedance file for the speaker. input any other information you need to on that screen (sensitivity, etc.). Repeat with the next driver.

      Don’t know if that is what you are looking for. More of a general “dive in, you got this” type response. And then, start playing.

      If you are unsure what to do next, if you know if you want a second or fourth order crossover, look up pictures on google on how they are laid out. Do not copy values, just their layouts. Then, start toying with the values. If you need to volume level, add a resistor before the sequence. Then, share your results. From there, more specific answers can flow, helping with impedance results, if phase issues wind up popping up, etc. And at that point, I’d recommend listening to someone more advanced than me at crossover design.

      But that should get you up and running and with an idea of what you are looking at for components to start.

    • #14944
      opulentone
      Member

      @ajc9988 

       

      Ok I managed to get DATS working (it’s actually really easy) and got some TS parameters, but when I enter them into WINISD it gives me an error for quality and then the measurements don’t make sense (like an infinitely large box required).

       

      Does anyone ever hop on Discord and just work on these programs together? I’d love to spend some quality time with a mentor… I have so many questions. 

    • #14948
      ajc9988
      Participant

      @opulentone – Sorry for the delay getting back to you.

      So, the help document for winISD first says the following:

      The suggested procedure for entering driver parameters is following (check first that “Auto calculate unknowns” option is checked):

      1. Enter Mms and Cms

      This gives fs. If either is not available, then enter fs and other parameter.

      2. Enter Sd, Bl and Re

      Now, you should get all but Qms (and Qts), Vas. Please note that Vas may not match exactly what is specified by manufacturer, because exact value of Vas depends on environmental parameters. See FAQ.

      3. Enter Rms or Qms.

      Either one will do, although I tend to prefer Qms over Rms, because it can usually be measured in driver measurement procedures.

      4. Enter Hc, Hg and Pe.

      If Hc or Hg or either is available, then enter Xmax and optionally either Hc or Hg if available.

      5. Enter number of voicecoils.

      This procedure is most accurate. Also note that it also calculates true SPL (1W/1m) value. So it might not match the marketing SPL value, which is generally somewhat vague. Not in all cases, though.

      6. Correct Znom, if necessary.

      If there are several voicecoils, then you must be careful when entering parameters in that case, because many manufacturers give Bl in voice coils in series, because it yields double value for Bl against parallel connection. If driver manufacturer gives Qes, Bl and Cms or Mms, then you can check how Bl is specified. For that, you can enter following parameters to calculate Re: Qes, Fs, Mms or Cms and Bl. Connection mode can be changed by changing the combobox selection. The driver editor then converts Bl and Re values accordingly.

      Equivalently, you can check for Bl by entering:

      Qes, Fs, Mms or Cms and Re (for desired connection mode).

      If you enter resistance for parallel connection and get about half of advertised Bl, then you know, that Bl was specified that way.

      Like in Driver-tab in project window, you’ll probably noticed the driver icon in bottom of the driver editor window. you can drag the driver object into some project by just dragging the icon.”

      Second is the question of what method you used for generating the MMS data in DATS. Did you do the added mass method? A known box volume? etc. This is needed for more accurate measurement of certain values.

      Also, some drivers are made for open baffle, which those will show you need something infinitely large. Can you say what driver you have? Could you also give the values you have for T/S values? That way I, or others, can simulate it and we can compare what we come up with.

      I don’t use discord anymore due to their terms of service and record retention policies. Sorry. I use that exclusively for old friends (and even that is limited these days).

    • #14965
      opulentone
      Member

      @ajc9988 my man my mentor, how’s it going.

       

      I made a video so you can watch me fumble through the process. 

       

       

      Enjoy! Any help is appreciated <3

       

       

    • #14967
      ajc9988
      Participant

      @opulentone – watching now. And yes, a driver is a driver. It is all about learning to create the driver’s best enclosure. The skills always translate.

      Piston diameter was entered wrong. You need to measure the peak to peak of the surround (unless that is what you measured). Most times, a speaker’s “size” is the size of the speaker plus the basket. You want only the piston diameter. For example, my 30W/4558T00 subs are 12″ subs. BUT, for piston diameter, it is only 244mm (that is what the spec sheet said, I measured 243, but I was doing it with a straight edge from my compound square set on top, so within 1mm, why not just add it from what the spec sheet said).

      If you get the diameter wrong, all other calculations on which it uses that number will also be wrong. So that is a potential issue.


      Now, notice that the diameter you entered as 6.5″ (Piston Diameter, D) in DATS is the value you should enter as Dd in WinISD. From Dd, WinISD can calculate the Sd value, and from that with I forgot what other value, it calculates Vd which is Volume displacement (IIRC).

      Now, if you also notice, I entered Qes from DATS. So if you enter the values I show in the sheet there, it should pass the driver check integrity.

       Now, I have not learned a good way to measure XMAX yet, and I took XMAX off of the product spec sheet, same with Power (for Pe, enter the continuous or RMS value of the driver, preferring that followed by Long Term Continuous 100 hr if the RMS value is not present.

      Now, Scanspeak, in their infinite wisdom, listed two values for peak and linear excursion. The highlighted ones are correct whereas the ones to the left under “Key Features” is wrong. The Key Features one is the peak to peak excursion. You need to divide that in half, which when you do, you get the values I highlighted in Yellow.

      For power, they listed it as IEC18.4 for the 100hr RMS. THAT is the one you want. The 18.2 long-term max power is a different measurement, and you will be riding your sub harder if you use it. Basically, use the lower power rating that is meant for long term when choosing what to enter for Pe.

      To recap:

      1) pull out a ruler and measure from the center of the surround (the domed part at the edge that sits highest) going from peak to peak.

      2) look online and try to find a datasheet for the driver to pull the XMAX and Pe (RMS Power rating) from (unless it is on the label for the driver somewhere).

      Once we deal with that, you should be ready to rock.

    • #14968
      ajc9988
      Participant

      @opulentone – As to designing the box in Winisd, I’ll take some screen shots to show iteration. I’ll do that after I finish this work product sometime tomorrow night, though. But I will step through fully my process, things I check, etc.

    • #14969
      opulentone
      Member

      @ajc9988 ok thanks! 

       

      I measured from center of the surround to center, so at least I got that right. Should I be looking up any other physical measurements or is the Xmax the only one I will need? 

    • #14970
      ajc9988
      Participant

      @opulentone – Center of surround to center of surround, right? See highlighting below.

      Other than that, Xmax and Pe (RMS power) are the only two you won’t have.

    • #14971
      opulentone
      Member

      @ajc9988 This particular driver says 50 watts max on it… should I go with that or some pro-rated number? Mind you these are garbage drivers but it’d be cool to be able to design on something totally unmarked. 

    • #14972
      ajc9988
      Participant

      @opulentone – So, I’d put 50W in winISD, but I wouldn’t plan on using 50W. Now, without X-max, it is a crap shoot. You could guess at X-max. For a 6.5″ driver, 4-6.5mm for X-max is probably what you are looking at. For example, my SEAS U18RNX-P have an X-max of 6 and a Pe of 80W. So, throw something like 4.5mm (9mm peak to peak) for X-max, and 50W for the Pe and see what you get.

      Now, remember, you will have to use the Piston Diameter you just measured and remeasure the driver in DATS as the other values will change with the piston diameter being smaller.

    • #14973
      ajc9988
      Participant

      @opulentone – For the enclosure, try vented/Chebychev.

      Then, you can go to the box and play with the tuning. I usually have to cycle between adjusting the filter I put on (I always filter the low end to help on when it reaches X-Max), changing signal to match a power wattage that does not go over the max excursion line, then back to box or vent to adjust the vent tuning or the box tuning, etc. You basically rotate between all of them finding equilibrium. Then, up at the top, you cycle between showing the following graphs:

      Transfer Function Magnitude – trying to make the response curve decently flat, figure out your 3dB down point, etc.

      SPL – just to see curve and estimated dB output

      Cone excursion (keep it under the line for the driver; this is effected with the filter for the low end and the wattage in the signal tab)

      Rear Port Air Velocity (you have to tune the vent to get this value to around 17m/s)

       

    • #14974
      ajc9988
      Participant

      To further get a handle on winISD, I would recommend watching the videos from Toid on his youtube channel and from DIYAudioGuy. There are a couple other tutorials I watched, but that got my feet wet.

      For the box tab, you can tune it manually slowly or use the mouse like you did (where it created a big hump in response). I usually play around with it like a theremin until I get it close, then I fine tune by slight adjustment.

      https://www.youtube.com/watch?v=LKUL_Q4JXbw&t=8s (example of theremin)

       

    • #14978
      123toid
      Keymaster

      @opulentone 

      A couple notes.  You do not have to re-calibrate your leads every time.

      For this driver you do not have to worry about it, but typically you do not want to put the driver directly on a hard surface.  You typically want to leave the pole able to vent.  This one doesn’t have a vented pole, so it isn’t an issue.  But something to think about. 

      You can measure the diameter yourself.  Just measure from one side of the surround (outside edge) to the direct other side (inside edge). Often times this will differ from the manufacturers stated diameter.  I am guessing yours is less than 6.5″ – this will throw off your data.

      For WinISD with Dats, you can use just the top data QES, QMS, QTS, FS, VAS etc. just enter one at a time and allow it to auto calculate. 

      You are correct that you can measure xmax with a tape measure. 

      This driver is a sealed back end, meaning it almost always will be designed for a smaller sealed box.  WHich is one of the reasons you are getting some weird info via xsim.  

       


    • #14979
      123toid
      Keymaster

      This is how I typically input new drivers, but in this case, I would skip to just the top data sections.  Remember to allow it to auto populate before inputting your next data.


    • #14984
      tvor-ceasar
      Moderator
      Posted by: @123toid

      @opulentone 

      For this driver you do not have to worry about it, but typically you do not want to put the driver directly on a hard surface.  You typically want to leave the pole able to vent.  This one doesn’t have a vented pole, so it isn’t an issue.  But something to think about. 

      And typically, the closer the driver to a flat surface, like a desktop, the more the sound reflections can influence the readings. If you can find something to set them on, a tall glass/cup, heavy cardboard tube, something not much bigger than the magnet, to lift it away from the desk, the higher the better.

      I’m lucky enough that the plotters at the office use roll paper and I have an S-load of 24″-36″ tubes in 1-1/2″ to 3″ diameter. Check out your local engineer/architect/sign/carpet places to see if they have any they are going to throw away. You can build a couple of nice stands from them for testing purposes.


    • #14985
      ajc9988
      Participant

      @123toid – So, here is my thought on how to measure the X-max using 1-2 straight edges and a AA battery.

      First, you lay one straight edge across the speaker for the reference, then measure down to the center of the dustcap. Now that you have that value, you use the battery to do a negative extreme in the way you test polarity for positive and negative terminal. While it is there, you read again from the center of the dustcap.

      You then subtract the second value from the first value and you have the excursion in one direction.

      I’m sure there may be an issue with whether it is still within the linear window for the field since the battery moves in to hold in one direction, but I think it is a good estimate.

      @OpulentOne – I forgot to mention, if the driver’s max is the short term max of 50W, just divide the value in half. Overall, the Xmax is more determinative to how much power you can put in and still play linearly, usually, than the power rating, which has to do with suspension, heat, and other variables like that before the driver harms itself.

    • #14997
      opulentone
      Member

      @ajc9988 

       

       

      Here’s an updated video on ‘crappy’ driver. 

       

      I also started doing measurements for the Rokit 8 woofer and tweeter.

       

      Here’s a fun question: does DATS measure a 1 inch tweeter correctly? I used the added mass measurement with a 18gram weight and got some results which I can attach for scrutiny… no wait I can’t because that file type is not allowed… so here’s a screenshot I guess. 

       tweeter

      woofer

       

      Here’s the final question. Both the tweeter and woofer are 4ohms. Will I be able to design a crossover to get them to an 8ohm load for use with a normal amplifier or am I doing a fool’s errand by even attempting this project? 

    • #14998
      ajc9988
      Participant

      @opulentone – I’ll watch the video on my next break.

      What I can say is the speaker will be 4 Ohm if the woofer is 4 Ohm. The largest driver (sub, woofer, etc.) determines the impedance of the speaker. So, with the Woofer being 4 Ohms, it is a 4 Ohm speaker all day.

      As to tweeters, because they are sealed usually (if not, ignore because you should then test the tweeter, although I would prefer the known box volume method for tweeters at that point), you will not be using the T/S parameters to design the enclosure most likely. If the tweeter is not sealed, then optimizing for it is something I can discuss at that point. 

      As such, if a sealed tweeter, just focus on designing the box for the woofer at that point, while being aware of crossover points and effects if you put the tweeter more than a wavelength away from the woofer.

      I’ll also put the data for the woofer in winISD later and then see what I come up with and what you come up with for a comparison.

      Also, if it ever says the file type isn’t allowed, save in a .zip archive and then attach the zip file. But those images will work great!

      You might also run a rub and buzz test on the drivers to see if they pass.

    • #14999
      ajc9988
      Participant

      @opulentone – I just looked closer and would recommend for the woofer to change the Le reading to be at 1K instead of 10K. 10K is used for tweeters.

      Edit: While cooking dinner, I just realized I forgot to tell you where this setting is. Go to Edit > Preferences then it is the third box down on the left.

    • #15007
      ajc9988
      Participant

      @opulentone – Have you ever heard of open baffle drivers? Basically, some drivers are built so that they do better in a massive space. When you see it ask for something insane, it means it is going to do better with being strapped to a board without compression on the other side of the driver, known as loading.

      An example of this is like guitar amps that are made to be in open enclosures.

      So, to be honest, if you want to build something with this, a flat board is the way to go!

    • #15016
      opulentone
      Member

      @ajc9988 To infinity open! Ok let’s say that I want to build something infinite open baffle with Crappy speaker. 

       

      The next step is to measure with REW and try to find a tweeter that is complementary? 

       

      I think I’ll make a video doing some REW measurements of various drivers I have and get your opinions on things. In this case I don’t have a box made for Crappy… do I do open air measurements? Built a board with a hole in it for the driver? 

       

      I took some REW measurements for the KRK 4 ohm speakers and got some weird results even after I limit the time window. I’ll make a little video and show you what’s up maybe tonight. Half my REW issue is that I’m in northern Canada and my furnace runs 90% of the time now that it’s -25C every day 😛 

       

      p.s. thanks again for all the help, it’s so awesome to see a helpful person / community. 

       

       

    • #15017
      ajc9988
      Participant

      I’ve got to get some sleep. Was up working all night and now crashing…

      A baffle (board with a hole) does help for directionality. But, TVOR gave a bit of information that mentions about trying to get the nearfield readings of the driver while trying to minimize reflections from the backside.

    • #15021
      123toid
      Keymaster

      @opulentone you only need to get your impedance measurement from a tweeter. The woofer if you do not know the T/S specs, you’re going to use that’s to receive those so that you can design the box properly.

      Otherwise once you’ve designed your box, you’ll take your impedance measurement of the woofer inside the newly designed enclosure. Then you will save that information in dats and export it as a zma file. You’ll need that impedance measurement for both the woofer and the Tweeter.

      Once you have the impedance of the tweeter, you want to get its frequency response. For this you’ll want to build a test baffle or the enclosure. Then you’ll get your frequency response using your microphone and software.  You’ll save those files as an frd file. You also want to take a measurement of both the woofer and the Tweeter in parallel together. 


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