Cone Excursion In WinISD

Discussion in 'Amps and Cabs [BG]' started by Donnie B, Dec 28, 2020.

  1. Donnie B

    Donnie B

    Jul 15, 2020
    I am currently attempt in to design a vented 1x15 cab in WinISD, it is my first time using this program and I'm running into some issues. The driver in question is a Celestion BN15-400X and I'm trying to tune at 33Hz. So, the problem is no matter what I do I cannot get the cone excursion below the Xlim of 0.16in at 300W (what my head will put out). At the spike around 57Hz the displacement is 0.375in with my current settings. If anyone could provide any tips, it would be much appreciated. Excursion Plot.jpg Response Plot.jpg Specs.jpg
     
  2. seamonkey

    seamonkey

    Aug 6, 2004
    TL;DR

    But try importing the params from Celestion BN15-400X

    And try some other box design software to see if it gives you similar results
     
    Dino Boreanaz likes this.
  3. Dino Boreanaz

    Dino Boreanaz Supporting Member

    Feb 25, 2018
    Toronto, Canada
    I tried running the OP's model using the parameters from Loudspeaker Database and got exactly the same results as the OP. I also tried reducing the box volume and had to make it VERY small to keep the excursion within Xmax throughout the frequency range. I tried adding a second-order HPF and had to bring the frequency up to 100 Hz in order to keep the excursion within Xmax.

    I'm certainly not a speaker designer or an expert with WinISD, but this seems like it may be a poor match of driver to application.
     
    seamonkey likes this.
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    There are 2 things going on here, they are somewhat related but not entirely.

    1. The box tuning is pretty low. Try 40Hz for Fb and I think you will find that you get better performance. 5 cubic feet, port area of 24 sq in, and a port depth of 4"

    2. The 5CF box is trading off low frequency extension for power handling fairly seriously, even with an Fb of 40Hz. The giveaway of this is the box size and the F3/F6/F10 numbers (42Hz, 36Hz, 30Hz). this comes at the expense of power handling. Xmax is 7.3mm at 63Hz with the tuning I posted above, which is 2mm less than yours (could be software differences but could also be your low tuning)

    3. Try a box that's 3.5CF with the same port area as above and a port depth of 6" and I think you will find that the displacement is now limited to 6.4mm at 300 watts) Of course you now have F3/F6/F9 numbers of 49Hz, 42Hz, 35Hz.

    But, in conclusion, this is why mechanical power handling ratings of speakers is such an important topic, and why some designers pay a lot of attention to using driver designs as well as cabinet designs that optimize mechanical power handling. I have received a fair amount of ridicule recently on TB about my cautioning players when using large amps with speakers that do not have enough mechanical power handling. In these conditions, players need to be very careful not to damage their speakers. I hear about the unfortunate results often enough to know that it is a very real problem, your example shows how this can happen.

    You can also see how you can't automatically take a speaker's nominal power handling rating as gospel, in this case how reliable would you think this driver might be with a bass player driving a 400 watt amp hard into it??? As usual, there is a lot of "it depends" in speaker design.
     
    Last edited: Dec 28, 2020
  5. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Adding a HPF will improve what happens below the low minima, but will not be very helpful for the peak excursion. This would be an example of applying a cure that's not really much of a cure at all... and maybe a false sense of security even.
     
    Dino Boreanaz likes this.
  6. Wasnex

    Wasnex

    Dec 25, 2011
    As @agedhorse mentioned, it's not that unusual for mechanical power handling below 100hz to be less than the driver's RMS rating.

    Choosing the right tuning is a matter of picking the compromise that best suits your needs. If you want extended lows, you often have to give up power handling. So do you want the cab to be able to play low, or do you want it to handle 400W?

    FYI PartsExpress includes plans for most of the pro Eminence woofers they stock. I have set up the following page to filter by the brand Eminence and 10", 12", 15", and 18" drivers. Click one of the drivers and view the product page. You should be able to open a Spec Sheet and Suggested Cabinet Design document for most of the drivers. The plans include graphs such as frequency response, max acoustic power, cone excursion. The variety of graphs varies somewhat from document to document. The idea here is so you can see the affects of different cab tunings.


    Pro Woofers, Subwoofers & Midrange Speakers - Parts Express

    Feel free to modify the filter to better suit your needs. For example if you only want to see the results for 15" drivers, deselect 10", 12", and 18"
     
    Jim C likes this.
  7. Donnie B

    Donnie B

    Jul 15, 2020
    Do you have any idea of the proper application of this driver, do you mean a smaller enclosure would be better? It is the speaker on hand, so I am working around it. In the end the enclosure I build, I want to best suit this particular driver.
     
  8. Dino Boreanaz

    Dino Boreanaz Supporting Member

    Feb 25, 2018
    Toronto, Canada
    I don't. My comment was based only on the fact that the WinISD model showed such high over-excursion through a very significant portion of your intended frequency range.

    I think @agedhorse gave some pretty solid recommendations on what to try in order to better match the driver to the enclosure. Part of it was a smaller enclosure and the other was a higher port tuning. Using his recommendations in WinISD, I get a peak excursion of about 7.7 mm at 71 Hz, whereas with your original design I got 9.5 mm at 57 Hz (confirmed to be the same as your result just to verify that the driver parameters matched what I downloaded from Loudspeaker Database). Although this is an improvement of almost 2 mm, it is still almost double the manufacturer's stated maximum of 4 mm. And note that these values are higher than those from @agedhorse model, so I would be cautious about basing your decision entirely on the WinISD model.

    Again, I'm not an expert. I'm just enjoying learning from the many others on this forum who have so much great, real-world experience. I've tried modelling some of their recommendations in WinISD to start to understand how all these parameters and characteristics affect things like the transfer function, cone excursion, and group delay of a system. Interesting stuff to be sure, but I'm afraid I can't offer any real help in trying to design an enclosure for a particular driver.

    As a final thought, although Celestion does not offer suggested enclosure designs for particular drivers unlike Eminence does, perhaps you could contact Celestion's technical representative for their thoughts. Although not specifically related to bass drivers, I have gotten great feedback from Dr. Decibel over the years on a variety of technical questions about their guitar speakers.
     
    agedhorse likes this.
  9. Donnie B

    Donnie B

    Jul 15, 2020
    Very helpful thank you. I'm new to this and trying to grasp some concepts so if you would mind explaining a few more things.
    If I tune above the Fs would the cab not audibly resonate at that frequency? Ive run into something before where a particular note would rattle the whole cab, not sure what the implication of the tuning frequency is in regard to this.

    Also I'm not sure if 400W or even 300W will ever see the light of day, as I primarily will use this in my small rehearsal space and anything past noon for gain would probably damage our ears, but does this mean i should not account for the maximum power.

    How does the Vas tie into the box size I thought that Vas was the optimum box size for the driver, for this one its 8.93 cf but the model in the software doesn't really back that up so im confused.

    Thanks again, thought I'd mention I'm currently an engineering student and love to challenge myself with projects way over my head, so please forgive my naivety haha.
     
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I have experienced results inconsistent results with WinISD compared with other software. With any modeling software, it’s essential to confirm the accuracy of the models. I find that I have greater confidence with the predictions when I am able to collaborate the model with actual measurements.
     
  11. Donnie B

    Donnie B

    Jul 15, 2020
    Right, thanks for your suggestions. I agree I'm incredibly fascinated by learning things like this and applying them in the real world. My intrests include engineering, woodworking and obviously slappin da bass, so as you can expect, this stuff is so exciting to me
     
  12. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    When resonance becomes an audible problem, it can usually be traced back to either poor enclosure construction (including bracing), or an effective “filter response Q” that is too high.

    VAS in combination with other parameters combine together to suggest a range of “optimum” enclosure volumes.