Dipole modeling software & info?

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BHTX

BHTX

Member
2006-02-16 10:49 am
  • #1
    I recently acquired 2 pairs of Pyle PPA15 woofers in two separate W type baffles from a fellow member on this forum. IMO, the dimensions are too deep, and it really needs a lot of bracing. It's creating a lot of ringing and resonances thoughout the operating range. Besides that, I'm currently planning on lowpassing them at 100-150 Hz 4th order to a pair of Radian 512/2B 12" coaxials anyway, so I don't really think this design is suitable anyway, regardless of how I modify it. Other than that, with quite a bit of EQ way down low, the amount of bass alone can be very plentiful and quite satisfying.. although I've only managed to listen to one all by itself on a mono amplifier with built-in lowpass xover, without anything for highs..so it's difficult to say yet how it'd be trying to match them with anything. Anyway, I was initially thinking of doing a WWCoaxWW configuration (I'll probably get 4 more of these woofers to play around with) in a very shallow U baffle, maybe around 24" wide at the most...but I really have no idea. Now I'm starting to have thoughts on a shallow H frame with all four woofers at the bottom..with two facing the opposite direction wired electrically out of phase so that the cones move in phase acoustically, with the 12" coaxial mounted above them on a flat baffle mounted flush on the front of the H frame. My only concern with anything besides a flat baffle is mainly cavity resonances, and that nasty hollow sound that I'd really like to avoid as much as possible. It really all depends on how low I'll be able to cross the coaxes to the Pyle woofers, but I guess I won't really know for sure until I get them and have something built to try it out for myself. Any thoughts though? I've just always assumed somewhere between 100 and 150 Hz. Any idea where I might be able to get ahold of some kind of free modeling software for open baffles that's fairly accurate? I've seen ABCDiple and MJK's software, but I was hoping there might be something out there free of charge, since finances are so tight right now. I might just go ahead and order one of them though. I guess I just thought I'd check around first. Mainly, any suggestions on what I should do to get me started in the right direction? Thanks..

    edit: Here's a link to info on the PPA15's, as well as the Radian coax I plan to use..
    http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=292-218
    http://www.radianaudio.com/products/ceiling/12_ceiling.php?viewT=ceiling&viewC=12_ceiling

    Also, I forgot to mention that the 15" woofers will be powered by their own Mackie pro amplifiers, and the Radians will be powered by a matching lower powered Mackie pro amp. The Radian coaxials will use Radian's prebuilt 2nd order xo, at least until I can figure out how to upgrade it or go active. I might decide to switch to tubes on the highs later on. As for which active crossover to cross between the woofers and coaxes, I'm not sure yet, but I'm leaning towards a Rane analog 4th order.
     
    AJinFLA

    AJinFLA

    Banned
    2005-02-09 4:35 am
    Tampa
  • #2
    Try The edge and XLbaffle
    Here is a post with a sim of your PPA15 drivers. The gentleman you purchased from was most likely influenced by the claims of another poster in the thread about 16hz bass from these - without eq in dipole configuration no less! ;)
    Slight difference between internet posts and physical reality as you might have found measuring these :).
    Keep in mind also that 4th order is the electrical, not electro-acoustic slope of your actual XO. The roll off of the coax must be accounted for. Or should be.

    cheers,

    AJ
     
    theAnonymous1

    theAnonymous1

    Member
    2004-02-19 5:53 pm
    Anonymityville
  • #5
    Right now I just have a pair mounted on flat baffles with two NSBs and a soft dome tweeter. One day soon (I hope), there will be two per side in W baffles to compliment the 12 NSBs and 24 soft domes per side.

    They hardly have any output >50hz or so right now. I blame that partly on the room and partly on the baffle. The baffle seems to absorb a lot of the energy from the driver. They are pretty close to the back wall also.

    They blend fairly well with the other drivers. They are crossed at 120hz 24dB/oct.

    Here is a bad pic, had to use my cell phone....

    [IMGDEAD]http://i19.tinypic.com/7yp6gcz.jpg[/IMGDEAD]
     
    BHTX

    BHTX

    Member
    2006-02-16 10:49 am
  • #6
    AJinFLA: Thanks for the reply. I've had the edge for a while..not all that useful in regards to open baffle simulation IMO, but does help give an idea of how driver placement on the baffle affects frequency response. I did download XLbaffle and played with it for a while, and found it to be useful. I also found and downloaded MJK's U & H Frame Woofer Worksheet here: http://www.pvconsultants.com/audio/boxmodel/uhframe.htm - Unfortunately, I can't quite figure out how to get it working properly, which sucks because I'm very interested in this one at this point. Seems like it could be very accurate, without taking specific frequency response of the driver into consideration of course. I'll keep toying with it though and see if I can figure it out. Doubtful though.


    panomaniac: Yep, I got these for $100 USD, plus $20 each for the W-U baffles..mainly just to have something to experiment with until I can get something else built, as well as to get a feel for OB bass, as I've never really had any experience with this type of design. Yes, they're cheap, but it's OB! I'd never consider them for anything else. Plus, this being my first venture into OB with conventional drivers, I wanted to start out cheap and end up with a solid design, only upgrading drivers in the long run if I felt it was really necessary and would be beneficial. So, that's the plan for now. And you're right about the rated Fs...I'm anxious to test these drivers some how. Been wanting to buy the new Woofer Tester, but I guess that'll have to wait a while longer. As for the sensitivity rating, it actually seems like it might be fairly accurate. And it's not quite as low as some of the 'better' alternatives, like the Hawthorne Augie for instance, which is what I was actually going to get in the first place, but decided not to after reading so many comments from others regarding the quality of bass from very high Qts drivers, plus the simple fact that this is my first OB project. With the possibility of 4 15's per side, that $150 per Augie turns into a pretty risky experiment!


    theAnonymous1: From what I've experienced with these W-U frames, your lack of low bass from those baffles isn't the least bit surprising. With them set up in these frames though, I can tell they have potential. Once I EQ the hell out of the 150-250+ Hz area to tame the cavity resonances and boost the low end a bit at around 50 Hz and under, it actually sounds quite good. The amount of bass alone can be more than I'd ever need, and this is only with ONE pair hooked up (only 1 of the 2 baffles). However, I have noticed a big null at about 55-70 Hz, and can't figure out why. The strange thing about it is.. I actually found the thread where the guy I bought these from was posting when he bought them. He mentioned experiencing the same exact thing in his room with these baffles. As of now, I'm leaning towards an H frame with half of the woofer's backs facing out (supposedly helps reduce some harmonics or something, just like an isobaric system), but still not completely sure. And I have no idea in regards to dimensions. The guy I bought these from said he tried facing one of the woofers the other direction (and wiring electrically out of phase so that the cones move the same direction), and didn't notice any difference. But I'm anxious to try it out myself, which I might do later tonight. Anyway, as far as these woofers go.. well, the build quality seems to be as you would expect from a woofer in its price range. You might have noticed the thread I just posted late lastnight regarding damping of the steel frames. They ring badly! Just take out and set it down in free-air, tap on the cone, and you'll see what I mean. The vented pole piece tends to make quite a bit of noise at high volume levels. I thought it wouldn't be quite as bad as it is, since we're only dealing with 6mm of excursion here. By the way, I wouldn't be the least bit surprised if that spec'd 6mm Xmax is actually the mechanical limit, rather than linear excursion. I've also noticed that the tensil leads are quite a bit longer than they actually have to be (once again, only 6mm cone travel), and they sometimes tend to flop around just right to where one or both of them will end up slapping the cone, which of course is very audible, actually quite loud, and sounds disgusting. Of course, this is only at high levels though. It's not that big of a deal really. Do yours have the push terminals? Mine do, which wasn't expected since most pictures you'll find on the 'net don't show them. However, I've found that you have to be very careful when connecting them, as it's extremely flimsy and wants to bend when you push them. Also, if I end up deciding to keep these for the long haul once I get something I'm satisfied with, I plan to paint the ugly dust caps. So... ringing stamped steel frame, tensil leads are too long, noisy vented pole piece at high levels, maybe a couple of questionable specifications, not the absolute quietest of drivers, and ugly logo stuff on the dust caps. Other than that, they're ok. Actually, despite what all I've said above, I still think that strictly for OB use, they'd be VERY hard to beat for such low costs. Any negligible improvements in another driver that's equally suitable for open baffle would likely cost a lot more.

    I just found out that the batteries in my digital camera are dead. It's a disaster in here right now anyway, and any photos I took would probably be pretty embarrassing. However, I do have a photo from the guy who sold them to me. He sent it to me just before I bought them. Even though he posted it on this forum back when he built these things, I don't feel right posting it here myself (it shows some other stuff in the pic, you know?). I'll see if I can email it to you. Maybe later tonight I can take a few more pics if you want.
     
    theAnonymous1

    theAnonymous1

    Member
    2004-02-19 5:53 pm
    Anonymityville
  • #7
    Thanks for the info BHTX.

    I just measured the Fs of one of my drivers in baffle and it is ~32hz. I used a frequency generator and voltage meter. The PE woofer tester is also on my "to buy list", but who knows when that will happen.

    The difference from the published spec might be due to the fact I replaced the dustcap as seen in the pic above. When I ordered the drivers from PE I also ordered 5" dustcaps as I knew I wouldn't want to keep looking at the pyle logo.

    I pulled the metal screens off the back and this seemed to help with the pole piece noise quite a bit.

    Your right about how flimsy the basket is. I'm not too worried about damping it at the moment as any resonance it has is well above any frequencies it plays. I'll save that tweak for last.
     
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