MJK or somebody: need some math help
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
 25th July 2012, 10:22 PM #1 chazdrumzalot   diyAudio Member   Join Date: May 2009 Location: Seattle, WA MJK or somebody: need some math help Just for fun, I'm trying to determine how the Eminence Deltalite-II would perform in a U- or H-frame. I wanted to get an idea of the ultimate system Q for the driver in a U-frame, so I tried using the equations that MJK has given in his article. I started with the equation for Qed: Qed = (Mms + Mair)*Fd*Re*Bl^-2 When applied to the eminence alpha 15, MJK gets a result of 1.792. However when I plug the deltalite's info in... (72+22)*36[est.]*5.29*15.7^-2 I get a result of ~72.62. What am I doing wrong to get such a dramatically different result? __________________ Then again, what do I know?
 26th July 2012, 05:03 AM #2 chazdrumzalot   diyAudio Member   Join Date: May 2009 Location: Seattle, WA Same thing happens when trying to solve for Qmd. According to the same paper I solved Rmd as 4.189, then when I applied that to the equation for Qmd I got 807.83. The equation given for Qmd is: Qmd = (Mmd +Mair)*Fd*Rmd^-1 or Qmd = 94*36*4.189^-1 however, if I change 94 to .94 I get a more reasonable solution of 8.07. Is that my error? __________________ Then again, what do I know?
 26th July 2012, 05:30 AM #3 chazdrumzalot   diyAudio Member   Join Date: May 2009 Location: Seattle, WA Well, I might have solved the problem. I was off by a factor of what, 100? By changing a gram from 1 to 0.01 in the equation I get more reasonable results. U-frame: .94*36*4.189^-1 = 8.07 Qms .94*36*5.29*15.7^-2 = 0.72 Qes (1/0.72+1/8.07)^-1 = 0.661 Qms predicted rolloff = 55Hz H-frame 1.14*36*4.189^-1 = 9.79 1.14*36*5.29*15.7^-2 = 0.88 (1/0.88+1/9.79)^-1 = 0.807 Fd = 32 rolloff = 40hz That sounds about right to me, although of course I am fudging the numbers a bit with regard to Fs. Without measuring I can't be entirely certain what a mass of 22g (or 44) will have on a cone of 72g weight compared to the alpha 15, which has a cone weighing 59.8g. If SPL is consistent with the A15 in these configurations, then the deltalite should still be around 89-90db efficient. But I have another question now, which MJK or some other guru can answer if he or she likes. Will a U-frame of double the depth (in this case, 15" as opposed to 7.5") have the same massing effect on a speaker cone as a similarly-sized H-frame, or is the effect diminished? __________________ Then again, what do I know? Last edited by chazdrumzalot; 26th July 2012 at 05:38 AM.
 26th July 2012, 03:17 PM #4 Jim Shearer   diyAudio Member     Join Date: Jun 2007 Location: eastern PA Somebody else should check this, but IIRC, making the U frame deeper than 7.5" will result in resonance down in a region where you don't want it. Cheers, Jim __________________ A day without music is like a day without food.
 26th July 2012, 07:03 PM #5 chazdrumzalot   diyAudio Member   Join Date: May 2009 Location: Seattle, WA That's what I recall too, but I wasn't sure if there was some leeway. __________________ Then again, what do I know?
 27th July 2012, 05:51 AM #6 GM   diyAudio Member     Join Date: Jun 2003 Location: Chamblee, Ga. Not really, unless you flare the sides out to at least a 12 deg included angle to turn it into a 1/2 WL resonator with good 'slap' echo decay same as a LEDE room design. When straight back it's a 1/4 WL resonator, so even before factoring in a large end correction that will further lower it, 7.5" is already down to ~13560/4/7.5 = ~452 Hz and you want it to be well above the XO point. GM __________________ Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Holton Precision Audio         CSS         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post Trapshooter Full Range 63 14th February 2012 01:53 AM wdcw Everything Else 15 1st November 2010 03:02 AM poorstudent Full Range 3 22nd November 2005 06:37 AM ctardi The Lounge 3 21st June 2005 05:11 PM

 New To Site? Need Help?

All times are GMT. The time now is 12:13 PM.