Re: Hello to everyone old and new.
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Flipping the wires to the treble driver in a Leslie indeed changes the phase relationship, and while this might seem subtle in some contexts, the impact on the crossover region is real and provable. Phase alignment, or lack thereof, can lead to cancellations or reinforcements around the crossover frequency, creating notches or peaks in the frequency response. These are measurable and audible as inconsistencies in tonal balance and imaging. Uwe's point about "notches" reflects well-documented acoustic principles, and tools like an RTA or phase response plots can demonstrate this. Aligning phase ensures smoother frequency response and coherent sound, which is why it¡¯s so critical in crossover design.
And I'll say this again, in a Leslie speaker system, with the horn rotations ongoing, whether this drastically affects the sound is debatable.
My 142 was wired out of phase and I flipped the?polarity 2 weeks ago. I hase only did one gig so far, but I am positive the frequencies in the 800-1200hz range were much more easily heard.
I know Christoph knows a lot more than I do, and I think he is simply misunderstanding what we are talking about. It's the same as having the HF horn driver and the 15" LF driver polarity reversed in a regular speaker enclosure.
It might be the use of 'phase' instead of 'polarity'. ?
Hi Christoph,
Not to beat the dead horse too badly, but the stereo example was to illustrate the original concern about how to phase a speaker so it will play well next to another speaker.? Indeed to solve the general case of bringing any random other speaker into the room and not have to worry about their relative phase.? ?Perhaps the manufacturer did not specify or pay attention to this at all in design/manufacture (odd as thst would be), perhaps the 2 models in the original discussion were wired "correctly" for each model, perhaps there was a mistake in assembly with one of them,? or maybe something else.? ?So I think this is what the OP has been trying to get to. Subwoofers generally do have 0/180 deg switches.? I don't believe most leslies or organ speakers do.? ?Also, I maybe should, but I don't know if + on the red terminal of every speaker in the world is supposed to make the cone move out (or in). In the end,? the OP can and will wire his speakers so they move in-phase, but I believe his question about which wires should go to which connector pins and speaker terminals on each model is valid.
Thanks for bringing some inspirational thoughts to my stalled restoration projects!
-Hugh
Hugh,
I¡®m not speaking of a stereo system with its two speakers. And also not about two Leslies.
The issue is alone about the question whether it is important to wire the woofer and the treble driver in a single Leslie ?in phase¡° and otherwise there were ?notches¡° in the frequency response ?nearby the takeover frequency¡°. And this I was criticizing.?
And a side note: it¡®s enter the room, not ?root¡°, as I mistakenly wrote below.
Good luck with your CV. I just finished a revision of a CV. Sounds great. Wonderful Chorus C3 Vibrato with a 122 hooked up to it.
¡ª Christoph? ? Christoph,
Please sit in front of your stereo speakers and listen to something with bass,?maybe in mono.? ?Then reverse the polarity of one of the speaker connections.? ?In one case the bass will appear to come from the middle of your head (in phase), and in the other case (out of phase), the sound will be all wrong.? So for low frequencies the phase of the woofers is quite important and Uwe's question is quite relevant.? ?(otherwise why would it be important to wire one's speakers with the correct polarity)? (the wavelength in air of a 100Hz sound is around 3.5 meters).? It is the interference here that is important, not the exact phase of a single signal.
Sorry to sound pedantic.?
One of these days I will get to working on the 3 tonewheel organs and leslie in my house (C3, Cv and M100, and 142 leslie (i think, missing its label)).? They I will be around with all sorts of sophomoric questions for the group!
-Hugh The human ear cannot hear the phase. It only can hear a phase change. If you enter the root with the Leslie spinning, you cannot say, whether is in phase or out of phase. Also the phase is frequency dependent on your position in the room.
Either is out of phase, you cannot say this or that is "out of phase".
In my remark to Uwe below, I was referring to the situation in a single Leslie in which you flip the wires going e.g. to the treble driver. And Uwes statement about "notches" in the range near the takeover frequency was what I was putting into doubt.
-- Christoph
Am 01.01.2025 um 18:10 schrieb Dennis Wage (N9OQ) < dwage@...>:
I witnessed it with my own ears. I put a sine wave tone at 600-700hz with the motors stopped and then physically reversed or flipped the phase of one of the drivers. It very easy to tell which way was in phase and which way was out of phase.?
Now, how much this affects the overall sound of the Leslie when motors are going fast and slow is debatable.? Uwe,
I believe you are wrong in your claim, that "out of phase connection of both drivers will result in a considerable notch in overall frequency response in the xover frequency region".
This is a nebulous statement lacking any mathematical or scientific substance.?
-- Christoph
You're absolutely right regarding the AC thing. But an out of phase connection of both drivers will result in a considerable notch in the overall frequency response in the xover frequency region. And, similar to a stereophonic setup, two Leslie's need to be connected in phase to get proper sound. ? Best regards!
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Dennis Wage (N9OQ)