Hi all,
I've read multiple threads on the subject and I'm getting a bit frustrated 🙂 Before calculating my own box I wanted to 'benchmark' by simulating the cab designs available on the website in WINISD. I don't get why, simulated before with dayton and other drivers, which I built and measured as expected.
I followed the tips on how to input a driver, basically not entering all data but having WINISD calculate as much as possible to avoid rounding errors. I got a 'green message' approving my driver in Winisd which is good. I tried also the export file available at loudspeakerdatabase, but it keeps calculating differently from the cab design sheet, I keep on getting a negative port length. I must be doing something wrong, and getting a bit frustrated.
Strange things is, I do get a vent speed similar (but higher, but that's because i used a round port as most topics say winisd does not calculate rectangular ports correctly) to the simulation. Also the graphs look similar, except the DB are much higher. Also the cone excursion at 600W is completely off.
I've done dozens of simulations, changed the parameters, so I will probably be doing something very wrong, would love to get your help on this! Avoids me building total crap with this driver.
I've read multiple threads on the subject and I'm getting a bit frustrated 🙂 Before calculating my own box I wanted to 'benchmark' by simulating the cab designs available on the website in WINISD. I don't get why, simulated before with dayton and other drivers, which I built and measured as expected.
I followed the tips on how to input a driver, basically not entering all data but having WINISD calculate as much as possible to avoid rounding errors. I got a 'green message' approving my driver in Winisd which is good. I tried also the export file available at loudspeakerdatabase, but it keeps calculating differently from the cab design sheet, I keep on getting a negative port length. I must be doing something wrong, and getting a bit frustrated.
Strange things is, I do get a vent speed similar (but higher, but that's because i used a round port as most topics say winisd does not calculate rectangular ports correctly) to the simulation. Also the graphs look similar, except the DB are much higher. Also the cone excursion at 600W is completely off.
I've done dozens of simulations, changed the parameters, so I will probably be doing something very wrong, would love to get your help on this! Avoids me building total crap with this driver.
Hi,
There are a couple of things I can suggest to check which will help a little, but the Maximum SPL difference baffles me.
I'd recommend deleting your driver record and starting again - I'll attach mine if you want to try it.
There is just no way that any 15" driver moving up to 14mm can possibly generate 140dB, so it may even be worth uninstalling and reinstalling WinISD to see if that helps.
The other specific things I can think of are these:
1: WinISD defaults to a box Ql of 10 rather than the more common 7 which Eminence use; if you haven't adjusted that then there will indeed be slightly higher excursion in the WinISD prediction. That is found in the "Advanced->" section on the Box tab. It doesnt bring things exactly in line with the Eminence model, but is a bit closer.
2: You haven't really modelled an equivalent vent. The Eminence suggestion is a square of 6.5" each side, giving 42.25 square inches of cross sectional area. You have modelled a round vent of 5.51" diameter which has only 23.8 square inches cross sectional area. Increase your vent diameter to 7.33" and the required vent length will get longer.
FWIW, WinISD does model 10-20% more excursion for a given input power than pretty much all of the Eminence suggested designs show, so I suspect they're simply using different maths to calculate that characteristic.
HTH,
David.
There are a couple of things I can suggest to check which will help a little, but the Maximum SPL difference baffles me.
I'd recommend deleting your driver record and starting again - I'll attach mine if you want to try it.
There is just no way that any 15" driver moving up to 14mm can possibly generate 140dB, so it may even be worth uninstalling and reinstalling WinISD to see if that helps.
The other specific things I can think of are these:
1: WinISD defaults to a box Ql of 10 rather than the more common 7 which Eminence use; if you haven't adjusted that then there will indeed be slightly higher excursion in the WinISD prediction. That is found in the "Advanced->" section on the Box tab. It doesnt bring things exactly in line with the Eminence model, but is a bit closer.
2: You haven't really modelled an equivalent vent. The Eminence suggestion is a square of 6.5" each side, giving 42.25 square inches of cross sectional area. You have modelled a round vent of 5.51" diameter which has only 23.8 square inches cross sectional area. Increase your vent diameter to 7.33" and the required vent length will get longer.
FWIW, WinISD does model 10-20% more excursion for a given input power than pretty much all of the Eminence suggested designs show, so I suspect they're simply using different maths to calculate that characteristic.
HTH,
David.
Yeah, HR's 2pi mid band eff. is 90.84 dB + 10log(1200) = 121.63 dB, so can only go higher if tuned > Fs.
Thanks!!! the project you added gave the same results in winisd as expected, if I use the driver to start a new project, again I have these high Db ratings. Will reinstall Winisd to see if this solves it!
YES YES YES, completely removing WINISD and reinstalling worked like a charm, finally I'm getting the same results as the cab design! No idea what was wrong, but it's solved. Thanks a million times!!!