Bikeology.net

i renew the speakers of my bike. now i have 3 woofers 8" 1 satelilat in the front and two tws piezo.. some pics..

What's it sound like? I'd be very worried of using two different drivers in common airspace.

two different drivers can actually be a good thing. each one will have different EQs and resonances etc. so they can spread their weaknesses further. one speaker might tone down the other's peak while the other fills in a frequency dropout.

i seem to remember reading something about that, or maybe it was in regards to isobarik subs where the backwards firing woofer cancels the other's distortions to a degree. i've always like the idea of isobarik subs because they're quicker & have less distortion, but they're automatically 3dB less efficient requiring twice the power for the same volume level.

weight and inefficiency are bad things for a street party bike.

Different speakers in the same enclosure sharing common airspace is a bad idea as they'd interfere with eachother.

Isobarik setups are great because you would only do it using the same woofers, it minimises any linear distortion as it's the opposite of the same driver.

but by mixing, you spread each speakers resonances etc. out. while it's a different design principle, that's what you get a bit with passive radiator systems which often use small woofers and larger passive radiators. haven't seen one of those in a few years though. the extra "driver" cuts into profit margins more than a cheap plastic port.

did the original poster say anything about SQ?

regardless, it's got to be better than a lowly boombox by a mile.

Unfortunately it doesn't quite work like that in reality, the variables you insert by using unmatched drivers far outnumbers any chance of countering resonances. Something will always have a resonance, you can't change that unless you modify it. For instance, a subwoofer might have a resonance of 32hz, you can stick it in a box with as many subs as you want but that one sub will still resonate at 32hz. The only resonance you'll effect by using multiple drivers is the cabinets but even then it's a much more productive task to just brace the hell out of.

Also passive radiators work in the same way as ported enclosures, they allow a woofer to fitted into a typically much smaller box but still have the sonic capabilities of a ported box, the beauty if a passive radiator set up is that you can change the tuning by differing the weights on the radiator.

right, but when you put a speaker with that 32Hz resonance in with one whose Fs is 50Hz, they'll smooth each other out.

i'd like to see test results for that.

It doesn't work like that man, you can't change the resonance of something without modifying it. What you will change is the resonance for the whole speaker cable.

cable resonance? huh? what are we doing talking about cables?

SPEAKERS (cone & dome etc. types anyways) all have resonant frequencies. this frequency can CHANGE according to the size of the box it's in (system Q) and each driver has it's own specific stats.

if you put TWO drivers in the same box with the same specs, they'll share THE SAME resonant frequency... let's say 50Hz for the sake of argument. both speakers will try to emphasize the SAME resonant frequency like any two instruments playing the same note.

when you use a speaker with entirely DIFFERENT thiele small parameters though, the resonance will be different. maybe speaker #2 resonates at 30Hz.

when you AVERAGE the response of the two speakers in a system, they will be resonating at two different frequencies and thus cancelling some of each other's resonances. speaker #1 doesn't add anything to 30Hz, because it's tuned to 50Hz and #2 doesn't boost 50Hz because it's tuned to 30Hz thus each speaker cancels out (or smooths) the other's resonances.

you know... MANY speakers have been built with multiple drivers of mixed sizes covering the same range? you make it sound like the world will end if you mismatch two different woofers when REALLY the more important issue is system Q! when you effectively cut each driver's airspace in half, you raise the Q and the resonant frequency of both drivers as well as raise the LF rolloff frequency. that's more important than driver interactions by a mile.

let's get REALLY extreme and mismatch an 8" sub with a 15" one. the 8" will add a little bit of speed to the attack of both woofers while the 15" will add extension. each speaker IS DOING A DIFFERENT THING and that's a good thing. they're spreading their errors into different fields.

two of the SAME drivers will repeat each others' peaks and distortions where two different drivers can help each other out to an extent.

ESPECIALLY regarding frequency response... unless they share some modes, each driver will smooth out the others peaks and valleys. if driver #1 has a frequency dip at 47Hz and #2 doesn't, it can help fill some of that out.

it really doesn't matter one way or the other though as it's purely THEORETICAL until someone builds for it and tests it. just like in societies... i still think variety is good. two different drivers can add different voices to a speaker.