Originally Posted by MBentz
I've not delved into this level of detail, but I'd be curious if the phase response of the system accounted for the slight difference in the voltage you're calculating. This would be due to the power factor:
In all honesty, some of this is a bit academic because at the end of the day you're going to use a volume knob to adjust the level - and if a musical signal comes through that exceeds the limits of the system, then you're going to hear the distortion and naturally turn it down. The important thing is to turn the system up slowly at the beginning until you're comfortable with where the true limits of the system are. You don't want to just start out blasting as loud as you can because different music causes the system to behave differently - and maybe a later transient will cause damage.
These calculations should be used to determine if your driver and amplifier is in the right ballpark of power rating. I generally go a bit higher on the amplifier because I prefer the sound of the driver distorting over the amp, and I know I'm not going to get crazy with the volume. An unclipping amplifier will also have better damping over the driver, which means better control over the driver when it does get over-driven.
LOL, yes, I agree that this became a little to academic, and laughed out loud when I read «at the end of the day you're going to use a volume knob to adjust the level»
However, I didn't understand jack sh*t before this project, but now I understand what amplifier gain is, how the voltage limiter works, how to optimize the gain structure, how EQ'ing affects max SPL over the whole passband, what Qtc and Fsc is, the difference between voltage peak and rms, how to think about voltage, impedance and current and are just more competent in reading measurements in general. Also I feel comfortable in my WinISD estimations and how to do them, knowing that they're just estimations and are only a guide and not absolute. +++ a lot more! I'll try to calm down the academic undertones from now on.
I do appreciate practical advice and that's what I'm after, but would also like to know how stuff works, as that makes me feel confident.
Thank you for the advice on having the sub distort before the amplifier, so I actually did as you said. In combination with what I tell BassThatHz below it gave goosebumps and maybe even a few structural cracks!!
Originally Posted by BassThatHz
I wouldn't go more than a few degrees above room-temp. If you feel any heat, stop.
If you don't exceed this much excursion then you will be ok (assuming the thermals are ok too). When the surround dipples like this then you know you are within 5-10mm of bottoming it out, this is about 88% xmech. Beyond this point the distortion is gonna climb fast (+10% THD).
More than 80 to 105vRMS gets risky for a sealed LMS in a decent sized box.
I've actually watched all your youtube videos with great interest these last few days, some of them several times.
The ones on the Ultra is very helpful because I see how far you push them there, and I've been looking for dimples like a teenager for pimples all night long playing 'the joy of minimal' which you were playing in a video. I've never been confident enough to push the sub that hard before, but now I am thanks to you and your videos
The dead spider video was hilarious, lol.
Also bought an IR thermometer from dealextreme which I hope is reliable. Been using my hands up until now, but don't want my fingerprints all over the cone.
The driver should arrive at the port here in Norway today, so maybe I'll have it before the weekend!! Can't wait to see what two Ultras can do with 'the joy of minimal', haha. These are very exciting times, and I lust for more!
Why did you go with four? I think your room is a little bigger. You have a lot of other subs too, but are you able to crank the Ultras as loud as you want to, or do you still want more? I want to be able to crank it up until I feel it's enough w/o fear of destroying the subs. I might have to start saving for two more.
EDIT: Reading your thread about building quads now.