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Old April 17th 18, 02:11 AM posted to alt.home.repair,sci.electronics.repair,rec.autos.tech
Clifford Heath[_2_]
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Default Using an iPad to follow a YouTube DIY without Internet to replaceautomotive speakers

On 17/04/18 10:26, James Wilkinson Sword wrote:
> On Tue, 17 Apr 2018 00:24:14 +0100, Clifford Heath >
> wrote:
>
>> On 17/04/18 06:34, Ragnusen Ultred wrote:
>>> Am Mon, 16 Apr 2018 13:20:55 -0700 (PDT), schrieb :
>>>
>>>> Then they are out of phase and as one cone is moving out,
>>>> the other is moving in. How noticeable it is, idk,
>>>> but audiophiles would be* horrified.
>>>
>>> Makes sense.
>>> Do you think that could damage the speakers?

>>
>> If two stereo speakers are out of phase,
>> they tend to cancel out low frequencies.
>> You get no bass. The cutoff frequency
>> depends on how far apart the speakers are.
>> If they're less than half a wavelength
>> you get significant cancellation.
>>
>> Try this: wire two speakers this way,
>> set your amp to mono, and place the
>> speakers directly face-to-face. Most
>> of the sound gets cancelled.

>
> Am I being stupid or shouldn't ALL the sound get cancelled at ANY
> frequency if you're sat midway between them?* Imagine you're sat in your
> living room and have one speaker 3 metres in front of you and 1 metre to
> the left, and the other 3 metres in front of you and 1 metre to the
> right.* All sounds come out of the two speakers 180 degrees out of
> phase.* Since the distance from the left speaker and the right speaker
> to your head is identical, the sounds will still be 180 degrees out of
> phase when they reach you.
>
> Since this doesn't happen I can only assume that either:
> 1) you hear the two out of phase sounds with different ears and your
> brain allows for this.
> 2) reflections off the walls mean you can always hear the sound anyway.
>
> I've often connected speakers both ways round and never been able to
> tell one was quieter than the other.
>
> If you were in one of those weird silent rooms (anechoic?) then you
> might not hear anything if you wired them up wrong.* I saw a TV program
> once where you couldn't hear someone speaking if they faced the other
> way, as the sound from their mouth didn't bounce off anything.* I guess
> the same would happen if you were floating in mid air, like er....
> space, but with air.
>
> Anyway, it doesn't matter, you get precisely the same sound whichever
> way you wire them up, I guess something just bounces.
>


Most of the sound you hear in any room is actually reflections.
Like 70%. So in your setup, you might get cancellation of the
direct sound, but that's only part of what you hear - and the
rest takes various paths that don't cancel.
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