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Post by Boomzilla on Jul 28, 2020 15:31:49 GMT -5
Here's the impedance (solid line) and phase (dotted line) of the Emotiva T2 loudspeaker.  If I were to place TWO of these speakers in series, the impedance would virtually double (as though it were straight resistance), but what happens to the PHASE? Does it double or half? Is it shifted in frequency? Note that this question is NOT about acoustic phase, but rather, electrical. Thanks - Boomzilla |
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Post by foggy1956 on Jul 28, 2020 16:09:44 GMT -5
Here's the impedance (solid line) and phase (dotted line) of the Emotiva T2 loudspeaker. If I were to place TWO of these speakers in series, the impedance would virtually double (as though it were straight resistance), but what happens to the PHASE? Does it double or half? Is it shifted in frequency? Note that this question is NOT about acoustic phase, but rather, electrical. Thanks - Boomzilla Does DC even have phase? |
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Post by mgbpuff on Jul 28, 2020 16:19:08 GMT -5
No change. One speaker impedance = R + jwL two speakers in series impedance = 2R + j2wL = 2(R +jwL) so impedance magnitude is doubled, but phase remains same. Dc has zero degrees phase  |
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DYohn
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Post by DYohn on Jul 28, 2020 16:47:29 GMT -5
And remember it's acoustic phase that you actually end up hearing...
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Post by DavidR on Jul 28, 2020 18:33:15 GMT -5
Here's the impedance (solid line) and phase (dotted line) of the Emotiva T2 loudspeaker. If I were to place TWO of these speakers in series, the impedance would virtually double (as though it were straight resistance), but what happens to the PHASE? Does it double or half? Is it shifted in frequency? Note that this question is NOT about acoustic phase, but rather, electrical. Thanks - Boomzilla Does DC even have phase? Speakers run on AC power. If it was DC it would not get thru any capacitors. It would also destroy most drivers. |
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Post by Boomzilla on Jul 28, 2020 21:17:48 GMT -5
No change. One speaker impedance = R + jwL two speakers in series impedance = 2R + j2wL = 2(R +jwL) so impedance magnitude is doubled, but phase remains same. Dc has zero degrees phase Other than your equation being wrong, it seems plausible. |
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Post by Ex_Vintage on Jul 28, 2020 22:15:28 GMT -5
I would think this is an implementation of series filters. The phase shift should double (for the 2nd speaker). The signal reaching the 2nd speaker IS impacted in phase (relative to the source) by the impedance and phase shift of the 1st speaker. Impedance doubles, phase shift total is cascaded from speaker 1 to speaker 2 in the series chain.
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Post by Boomzilla on Jul 29, 2020 3:11:11 GMT -5
I would think this is an implementation of series filters. The phase shift should double (for the 2nd speaker). The signal reaching the 2nd speaker IS impacted in phase (relative to the source) by the impedance and phase shift of the 1st speaker. Impedance doubles, phase shift total is cascaded from speaker 1 to speaker 2 in the series chain. Speaker 1 impedance = R + jwl Speaker 2 impedance = R + jwl Summed load to amplifier = 2(R + jwl) or 2R + 2jwl So from the phase chart: At 112 Hz. the minimum series impedance will now equal approximately 5 Ohms, and at 70 Hz. the phase will be -108 degrees, equivalent to +18 degrees? |
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Post by audiosyndrome on Jul 29, 2020 7:57:45 GMT -5
Boom - your equations are wrong unless you took the capacitors out of the T2s.
Russ
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Post by mgbpuff on Jul 29, 2020 8:29:18 GMT -5
Boom - your equations are wrong unless you took the capacitors out of the T2s. Russ Well show us the equation then! I don't think it makes any difference what the imaginary magnitude is (I just showed an L because inductance predominates), the answer is still the same. |
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Post by Boomzilla on Jul 29, 2020 9:54:08 GMT -5
Boom - your equations are wrong unless you took the capacitors out of the T2s. Russ I got lazy & just used mgbpuff 's equation. But if you want to be technical, then impedance (Z) is defined as:  Since I lack the X/sub L and X/sub C for the T2 speakers, I'm having to use the Stereophile graph instead. But I don't want to build clocks here - I want to tell time. And the issue here is NOT about the impedance. With speakers in series, impedances are simple addition. The question is about the electrical phase, that relates (in layman's terms, and as I understand it), to how hard the amplifier must work to maintain current flow relative to the reactivity of the speaker. In "pro" audio, series and parallel speaker networks are used extensively to provide amplifiers with acceptable impedances. So this is neither unusual nor excessively complex. I just don't have the information necessary to see what the phase angle will be with series drivers. |
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Post by DavidR on Jul 29, 2020 10:30:14 GMT -5
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DYohn
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Post by DYohn on Jul 29, 2020 11:00:53 GMT -5
Boomzilla, I assume what you are worried about in terms of phase is creating an out of phase relationship between the two loudspeakers? That can't happen by series or parallel wiring (unless you do it intentionally.) As far as the effect on passive crossover networks by placing two of them in series, this can change both the crossover knee point and the effectiveness of things like level pads, but it should have no effect at all on the electrical phase shifts inside each system caused by the crossover. The far far greater impact will be the impedance change and the impact of acoustic phase issues in the listening space caused by speaker placement (which is what you've been experimenting with.) And finally, I'll leave you with a quote from one of the premier theorists in this field:
"It turns out that, within very generous tolerances, humans are insensitive to phase shifts. Under carefully contrived circumstances, special signals auditioned in anechoic conditions, or through headphones, people have heard slight differences. However, even these limited results have failed to provide clear evidence of a 'preference' for a lack of phase shift. When auditioned in real rooms, these differences disappear ..." -- Dr Floyd Toole
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Post by DavidR on Jul 29, 2020 13:41:34 GMT -5
Use two amps and you won't have to worry about impedance or phase angle
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Post by garbulky on Jul 29, 2020 13:46:20 GMT -5
Use two amps and you won't have to worry about impedance or phase angle This would probably be B'zilla's best bet imo. |
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Post by Boomzilla on Jul 29, 2020 13:54:11 GMT -5
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Post by Boomzilla on Jul 29, 2020 14:00:20 GMT -5
Well, I did wire the speakers in series, and I did bridge the amplifiers. Results: Sounds GREAT! Can I tell any radical difference from running each speaker with its own amplifier channel? Difference - yes. Radical difference - no. From what I'm hearing, the bridged amplifier with series speakers seems more dynamic than did the "one amp channel to one speaker" arrangement. Why? I've no idea. I don't play loudly, so it isn't a headroom issue. Maybe these particular amps just sound more dynamic in bridged mode? I may remove the bridged amps and try the series speakers with the Emotiva PA-1 amps. Should be an easy load for them. But if you're putting IDENTICAL speakers in series, then KeithL is right - NOT a problem. |
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DYohn
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Post by DYohn on Jul 29, 2020 14:19:39 GMT -5
Well, I did wire the speakers in series, and I did bridge the amplifiers. Results: Sounds GREAT! Can I tell any radical difference from running each speaker with its own amplifier channel? Difference - yes. Radical difference - no. From what I'm hearing, the bridged amplifier with series speakers seems more dynamic than did the "one amp channel to one speaker" arrangement. Why? I've no idea. I don't play loudly, so it isn't a headroom issue. Maybe these particular amps just sound more dynamic in bridged mode? I may remove the bridged amps and try the series speakers with the Emotiva PA-1 amps. Should be an easy load for them. But if you're putting IDENTICAL speakers in series, then KeithL is right - NOT a problem. I'll argue that they don't have to be identical. |
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Post by Boomzilla on Jul 30, 2020 5:53:18 GMT -5
The following is courtesy of Mr. David Rich from Secrets of Home Theater and High Fidelity:
1) I have never seen a speaker with internal drivers in series. I have seen some simple series crossover circuits in the past but not for a long time. They tended to be low order.
Your assumption that the connection at the middle of the speakers is Vin/2 assumes the impedances of the two speakers match. They do not as a result of manufacturing tolerance. You also have to remember the graph you show below is a small signal (less than a watt) linear representation. As the voltage drive does up the speakers suspension and spider change compliance at the limits as does the impedance of the motor as the coil starts to get near the end of the gap.
Good enough for sound reinforcement. I also suspect the rule is parallel for two then next two series. Allows the 4 speakers to average the errors.
You need a speaker engineer to answer the question of what disadvantages occur when put identical speakers in series when all the issues are considered.
2) It is not the question you asked so let us move on to what you did ask.
Z = magnitude (f )> phase angle (f ) where f is a given frequency.
Call the magnitude at f MAG and phase of f PHA
It is now time for some junior high math so I can convert magnitude and phase into real and imaginary
Re = Magnitude cos (phase) Im = Magnitude sin (phase)
Let us define them for one speaker as:
REL =MAG cos PHA IMG = MAG sin PHA
Since you have two identical blocks in series we double these:
REL (identical series) = 2REL (individual) IMG (identical series) = 2IMG
Now we have to go back. The magnitude is the square root of the square of the real and imaginary lets skip that. Trust me it is coming out 2 MAG
The phase is tan –1 (Re / Im)
=tan-1 (2REL/2IMG) = tan –1 (REL/IMG)
So we have no change in phase
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DYohn
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Post by DYohn on Jul 30, 2020 8:46:59 GMT -5
Absolutely. His statements all apply if the two are identical. But they do not have to be identical. If they are not the math simply changes. The acoustic impact on the listening space changes. But it is perfectly OK to do so and the phase shift in each system remain the same.
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