I'm putting together an efficient 3 way speaker system with an active crossover. Because the drivers are efficient (~97dB) and won't be played overly loud, I was thinking that I could use a lower crossover point for the dome tweeter (~1600hz 24db). My rational is this: I won't have thermal issues because the driver is efficient.
I'm wondering, in this situation, could the mechanical limit of the tweeter be reached? Anyone with experience having tweeters "bottom out"? If so, what did it sound like and were they destroyed? I have 4 but I'd rather not use the spares stupidly.
I'm wondering, in this situation, could the mechanical limit of the tweeter be reached? Anyone with experience having tweeters "bottom out"? If so, what did it sound like and were they destroyed? I have 4 but I'd rather not use the spares stupidly.
Usually about 1.5 - 2 octaves above the resonant freq of the tweeter is a good place to cross. Your theory is sound that by crossing a high efficiency with a 24db filter you can get away with crossing lower, but it can sound harsh (distorsion) on many, if not most tweeters.
And if you are using HE mids and bass the tweeter will have to match them ie the tweet will have to be about 6db higher.
And if you are using HE mids and bass the tweeter will have to match them ie the tweet will have to be about 6db higher.
Opinions have varied on the Infinity Polycell tweeters, personally I like them (though I haven't tried them crossed over at 1600 yet). I still need to purchase a 6 channel amp
Good to know. I guess it'll be trial and error, easier done with an active crossover!
I will be using HE mids and bass (probably going to go with an Eminence Alpha 10A for bass, and use the original 4" midrange from the Infinity SM-112).
I didn't know that I'd have to boost the output of the tweeter so much to match the other drivers. Easier with an active crossover as well!
Basically, my reason for this project is that the foam surrounds on the woofers has rotted on a pair of Infinity SM-112 (so replacing with Eminence Alpha 10A, stuffing the box with some insulation and reinforcing cabinet), and the midrange section of the crossover of one of the speakers has malfunctioned (hole between its lowest frequency and highest of woofer). I'm on a somewhat tight budget for the next couple years and think these drivers are sufficient for me to learn with/enjoy music for a while.
Edit: resonant frequency for the tweeters are 1548 and 1555hz
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Bad Engineer! No Cookie!
TYPICALLY a tweeter's maximum mechanical excursion is significanlty longer than the linear Xmax excursion. You will hear nasty distortion before any mechanical damage occurs. If your tweeter uses FerroFluid, you may knock it out with large excursions.
You will want to study the tweeter's coil/motor datasheet.
ScanSpeak D3004/660000 example of a small linear Xmax tweeter
Voice Coil and Magnet Data 26mm
Voice Coil height 2.1mm
Height of gap 2.5mm
Linear excursion +/- 0.2mm
Max. mech excursion +/- 1.6mm
TYPICALLY a tweeter's maximum mechanical excursion is significanlty longer than the linear Xmax excursion. You will hear nasty distortion before any mechanical damage occurs. If your tweeter uses FerroFluid, you may knock it out with large excursions.
You will want to study the tweeter's coil/motor datasheet.
ScanSpeak D3004/660000 example of a small linear Xmax tweeter
Voice Coil and Magnet Data 26mm
Voice Coil height 2.1mm
Height of gap 2.5mm
Linear excursion +/- 0.2mm
Max. mech excursion +/- 1.6mm
Very helpful, thanks!
Unfortunately the datasheet is unavailable. Maybe if I contacted Infinity they could dig it up (the tweeter's 20 years old), but that seems pointless if what you're saying is true of most tweeters.
Then you have the winning tweeter. Unless you have a weak tweeter then 1600 hz @ 24 dB would probably work without any issues at all.
I measured some Monacor DT-300 with the WG-300 waveguide the other day and they would even allow a 1400 hz @ 24 dB crossover and still play 96-100 dB without significantly distorting.
Hi,
Replace the surrounds rather than new bass drivers, lots of kits.
Update / repair the original crossovers.
A 6 channel amplifier and an off the shelf active x/o makes no sense.
Reality is absolutely nowhere near 97dB/W/1m.
rgds, sreten.
I considered repairing the drivers with a kit. Still not decided for sure, but I'm really leaning towards buying new ones.
Part of the reason I'm using an active crossover now is to get a feel for how to configure one (as well as reap some benefits of them in the mean time). In a couple years I'll buy new drivers, start from scratch, and put together a slick system.
Reality is very close to 97dB/W/m, possibly greater. In the past I've had these speakers on channel A of an amplifier, and a various assortment of speakers between 89 and 92dB/W/m on B. Switching between them an extreme difference in amplitude. Having one SM 112 on left of A and a Mission M32 on the right of A, at lower volumes, it has been hard to tell if the mission was on or not. Easily 6dB greater efficiency than the missions, which I believe are 90-91dB/W/m
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