16 ohm and 4 ohms speaker in parallel |
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Hemisphere
Old Croc Joined: 21 April 2008 Status: Offline Points: 2272 |
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Well you've expanded the question beyond the original thread topic (which was more or less just 'can it be done?')
Mixing Ohm ratings has no impact on sound quality - positive or negative - it's just there are almost no instances where it would be sensible. If you have two speakers with mismatching impedances wired together, then one will draw more power from the amp than the other. We've established that. That doesn't mean the speaker will take more power to produce the same level of sound. One Watt into the speaker is still one Watt, that Watt will just be distributed unevenly between the speakers. Where sound quality comes into it, is that you literally cannot fit a crossover between the two parallelled speakers, so if you're running a bass bin and a midtop in parallel on the same amp channel, that bass speaker is going to be playing high frequencies which won't sound good, and the midtop will probably be playing bass frequencies that it can't handle. There's no risk to anything. The amp only cares about the total impedance of the load presented to it. The reason everyone is advising so strongly against the idea is because the 'stretch' you imagine of an instance where this might be sensible, basically doesn't exist. At least not if you're trying to build a professional system. Even if the frequency bands being reproduced are identical, and the sensitivity of one speaker is 3dB or 6dB lower (with half or a quarter of the amp power giving the same output level), there are so many other factors that will come into play. It would be better to revise the system plan and work from there, even if it meant selling old kit and buying something else.
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Jo bg
Young Croc Joined: 08 March 2017 Status: Offline Points: 552 |
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thanks for clearing it out. yes maybe i carried it OT, sorry.
i know i don't want a sub playing high, and surely there is nothing pro about it... this came to my mind thinking about a 12v suicide rig, in which careful placement (maybe a bandpass design?) of the woofer could maybe integrate it's falling slope with a full range 3 or 4 inch driver like the faital ones. power level will be very low so no excursion problems, and having the sub get more power through lower impedance should be a good thing in that case - i know i like my subs hot. i recon it would be very hard/impossible to find that sweet spot and building a simple crossover would be an easier way to get an almost decent sound (memba it's a suicide rig for drunks expectation is waaaay lower than for the main rig, and i should have clarified this earlier). thanks again for playing along, i will not waste more time on this idea. |
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Hemisphere
Old Croc Joined: 21 April 2008 Status: Offline Points: 2272 |
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Yes, that might be appropriate for a system like that. I know the sort of system you're talking about. You maybe only have one knackered old car amp and it's running full range and bridged mono, the less components you can possibly have running the better, etc.
Don't expect a bandpass to sound good outside of it's pass band just because it drops off in the sim though. It will be playing some frequencies that it shouldn't play, and some of those will definitely emerge from the enclosure, and if they're playing at 4 times the dB level (or 10 or more times if it's a sensitive sub) of the midtops then that's going to sound rough man. Even if it's 30dB down at 500Hz, it may only be 15dB down after the Ohm and sensitivity mismatch. The 200-500Hz area is exactly where you don't want a large peak in your response, so they'd better be drunk!
Edited by Hemisphere - 17 November 2017 at 1:22pm |
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Jo bg
Young Croc Joined: 08 March 2017 Status: Offline Points: 552 |
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Ok got it. Thanks again. Time to start messing with caps and coils...
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