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Post by boomzilla on Jul 30, 2020 5:48:48 GMT -5
So the result is the same as I said. Two new things have been pointed out. 1)The speaker components have a tolerance so they are unlikely to be identical, but I do not think that would cause a perceptible difference. 2) DYohn pointed out that the damping factor would be lowered significantly. This is probably the single greatest difference than all other factors. You're both right. And although speaker components will never be exactly identical, if the speakers are the same make and model, then they're "close enough." Also, if you're using a solid-state amp of any significant power output, the damping factor is already excessive by a margin of between 10 and 100. And if the speaker impedance has doubled by placing two speakers in series, then the damping factor (speaker impedance divided by amplifier output impedance) has actually gone UP - not down. But Mr. Yohn is probably considering the situation of driving a single speaker with a bridged amplifier - in which case he's exactly right (the amplifier output impedance has doubled, but the speaker impedance remains constant). But even with the denominator being doubled, if one starts with a 10 to 100 damping factor excess, cutting it in half is academic.
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Post by mgbpuff on Jul 30, 2020 6:01:00 GMT -5
So the result is the same as I said. Two new things have been pointed out. 1)The speaker components have a tolerance so they are unlikely to be identical, but I do not think that would cause a perceptible difference. 2) DYohn pointed out that the damping factor would be lowered significantly. This is probably the single greatest difference than all other factors. You're both right. And although speaker components will never be exactly identical, if the speakers are the same make and model, then they're "close enough." Also, if you're using a solid-state amp of any significant power output, the damping factor is already excessive by a margin of between 10 and 100. And if the speaker impedance has doubled by placing two speakers in series, then the damping factor (speaker impedance divided by amplifier output impedance) has actually gone UP - not down. But Mr. Yohn is probably considering the situation of driving a single speaker with a bridged amplifier - in which case he's exactly right (the amplifier output impedance has doubled, but the speaker impedance remains constant). But even with the denominator being doubled, if one starts with a 10 to 100 damping factor excess, cutting it in half is academic. While I do agree about the insignificance of the damping factor change because it is so high to begin with, I do not agree that two speakers in series increases the damping factor. It decreases the damping factor because the other speaker's impedance must be lumped in with the amplifier's impedance.
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Post by boomzilla on Jul 30, 2020 6:16:04 GMT -5
While I do agree about the insignificance of the damping factor change because it is so high to begin with, I do not agree that two speakers in series increases the damping factor. It decreases the damping factor because the other speaker's impedance must be lumped in with the amplifier's impedance. Looked at as individual speakers, you're right. To control either of the two, the amplifier must "go through" the other. But considered as a system, the impedance doubles, therefore the damping factor also doubles. Consider for a moment a single cabinet with two series woofers inside (for example, a subwoofer with two 2-Ohm drivers) - although it's true that the damping factor for each individual woofer would be lower, the amp never plays only one woofer. It only plays the pair as a system. And therefore there are but two components in the equation - the amplifier's internal impedance (that doesn't change, regardless of load), and the load being driven - that is the composite of all individual drivers' impedances plus the resistance of the connecting wires. It's a deliberate distortion to say that the damping factor of a single component is low if the amplifier never plays that component individually. Only the composite impedance of the system being played is used to calculate damping factor.
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Post by mgbpuff on Jul 30, 2020 6:48:36 GMT -5
But you don't have one speaker system spring (which becomes a regenerative prime mover), you have two and they are not physically tied to each other and the back pressure waves on each may differ due to placement differences. I think we must agree to disagree on this matter.
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Post by boomzilla on Jul 30, 2020 7:55:43 GMT -5
But you don't have one speaker system spring (which becomes a regenerative prime mover), you have two and they are not physically tied to each other and the back pressure waves on each may differ due to placement differences. I think we must agree to disagree on this matter. I do understand your viewpoint, and I respect your comments. The only qualm I'd offer is that you've suddenly shifted the discussion from electrical phase to acoustic phase. I'd readily agree that acoustic phase WILL have significant differences. But from the circuit analysis standpoint, impedance is still just impedance. In any case, I think we've beat this horse enough. I agree that we can disagree. And I admire both your thoughtfulness on this issue and the fact that you stick to your guns! Thanks. Glenn
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KeithL
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Post by KeithL on Aug 3, 2020 15:16:46 GMT -5
When you chain two identical loads in series the total impedance doubles. But the phase angle stays the same. (Although, at least in theory, you could get tiny differences due to pressure loading on the drivers themselves.)
You also have one more choice. Place them on their sides on top of each subwoofer. Have the tweeters on each stack flipped. So a tweeter from the top speaker is above the woofer of the second. Alas, this is not feasible. Why? The Sanus Euro stands have a weight limit below the combined weight of the S15 subs and two pairs of T2s. Experience has shown me that if I exceed the stands' weight limit, the support tubing on the bottom deforms and the whole rack tilts. I almost dumped a whole review group of McIntosh gear on the floor one time because the stand was deforming! The only good way to avoid deformation is to eliminate the support tubing base entirely, and to use plate casters, screwed directly into the bottom wooden shelf. I've done that with my main "double wide" equipment rack, but have not yet done it with any of the single-width racks. I can, however, as klinemj has suggested, place the two towers side-by-side, and may do so soon. While they're close like that, it may also be time to try wiring the towers in series and bridging the Ashly amplifiers. KeithL and/or DYohn and/or leonski - What happens to phase angle when identical speakers are daisy-chained in series? Thanks - Boom
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Post by leonski on Aug 3, 2020 16:59:57 GMT -5
What happens when you place loudspeaker systems in series is 1) you double the net impedance loading the amplifier. This has the effects of reducing the output dbSPL for any given volume setting, and of reducing the total damping factor of the system significantly. 2) you introduce a time delay phase shift in one loudspeaker relative to the other as the crossovers are now in series and affecting each other. This may or may not be audible and depending on system placement might cancel out. 3) anytime you introduce multiple systems reproducing the same signal you introduce unpredictable time-domain cancellations in the listening space due to lobing. Again the degree to which this is audible (or even detrimental) varies depending on speaker placement and room geometry. Try it. What have you got to lose? I LONG time ago....mid 80s, perhaps? I experimented with a DIY version of Dynaquad. Remember that? You DIDN'T need more amplifiers for more channels. I boiled it down to the minimum. And DID use a second amplifer for the 'back' channels. Wireing was as follows:: Standard stereo setup in front. 2 speakers properly wired and tuned for placement. You needed to 'jumper' the signal to the back amp.... A SECOND amp, with a PAIR of speakers wired in series from PLUS to PLUS. For the possible health of the amp, I put a power resistor in the normal place of the speakers on that amp. What you ended up with was the channel difference going to the 'back' channels. It worked wonders on LIVE material but was dead for studio material where such phase shifts didn't exist. \To TOP it off? It DID make a difference on the back speakers if they were wired Plus to Plus or Plus to Minus....Putting them facing mostly away from one-another wired Plus to Minus produced the widest sound field. When playing a LIVE album, it sounded like you were in the middle of the venue, surrounded by people. You could do the same thing with a common ground amp, but I had an 'extra' lying about. I used a 100x2 SAE amp in front with JBL 4311s and I had some RSL 3600s and a Kenwood amp in back. The speakers were a near-perfect match, since the JBL was the 'target speaker' when the RSL was designed. Same 12" 3-way ported configuration. And within milimeters dimensionally. I suspect also that if Keith was referring to phase differences in the electrical domain, that component differences which you'd NEVER hear, may cause additional issues. Don't forget that most caps used in 'regular' crossovers maybe be 20% tolerance and in other cases a better 10%. Higher cost alternatives are out there in the 5% range....
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