Turbomax Reflex - It begins...

Timebomb wrote: You can set WinISD to display excursion as peak or RMS excursion, id set it to peak as thats your worst case and you measure xmax as a peak value anyway.  Like Ceharden says i wouldn't worry if it gos over a tad, are you inputting real xmax? (coil length-gap height/2) or adding 1/4 of the gap height?, or using a different meathod?  If your using real xmax you should be fine with that sim of the fane.  You can do a rough impedance plot with 2 multi meters and a sine tone generator/ pc program / rogs test cd.  Run a sine signal into the cab, keep voltage from the amp constant and mesure current drawn by the speaker, then repeat at difference frequencys, calcluate the impedance at a frequency (voltage/current), then plot it on a graph and you have an impedance plot to compare to the simmed one on WinISD.  Thats the best way of measureing the tuning of a cab, and how the port is being lengthnd.

I just realised this Ive simmed the jobst lbb118 in winisd and was a bit worried if I can give them full 500watts. Had the cone excursion at peak and it was 1mm over xmax,changed it to rms and its well under the line at 500w.

You can set WinISD to display excursion as peak or RMS excursion, id set it to peak as thats your worst case and you measure xmax as a peak value anyway.  Like Ceharden says i wouldn't worry if it gos over a tad, are you inputting real xmax? (coil length-gap height/2) or adding 1/4 of the gap height?, or using a different meathod?  If your using real xmax you should be fine with that sim of the fane. 

You can do a rough impedance plot with 2 multi meters and a sine tone generator/ pc program / rogs test cd.  Run a sine signal into the cab, keep voltage from the amp constant and mesure current drawn by the speaker, then repeat at difference frequencys, calcluate the impedance at a frequency (voltage/current), then plot it on a graph and you have an impedance plot to compare to the simmed one on WinISD.  Thats the best way of measureing the tuning of a cab, and how the port is being lengthnd.

  

In the actual cab the port will be effectively extended.  Simulation software doesn't seem to take that into account very well.

When designing port lengths in WinISD I generally set the tuning up to 5Hz higher than I want it to be on the real cab.

I think WinISD calculates based on sine wave signals so the excursion is worst case.  I wouldn't worry too much unless the predicted excursion goes several mm over xmax at full power input.

In the above example,  the input power is on a linear scale, if you converted it to log (dB scale) then you'll find the dip is probably only 2dB or less.

What is the cabinet volume and port tuning for those plots?

Excursion peak above the port tuning, the max input power the cab is capable of taking is limited by the xmax of the driver in that frequency range.  It can take more power down low as the port is reducing excursion.

If you were using that driver id suggest a little boost and 40Hz and a cut at 54Hz, it would increase overall power handleing of the cab, or maybe even dial it in as a dynamic EQ on the DCX if you have one? ,  so it only kicks in at high power.


Edited by Timebomb - 12 July 2009 at 2:29am

Hmm, put the tuning into WinISD to double check it (used Bassbox for the main design), it came out near enough the same.

However one graph did make me wonder, this is the turbomax cab, and then the same cab with a 600W 18XB in.

What's the dip all about? And are the manually entered T/S parameters for the Turbomax missing some data in comparison to the 18XB?