SWL9.0SE Inverting Phase (polarity)

s_cervin · « **on:** 22 Dec 2006, 01:02 am »

Hello,

I've got real interest in this preamp based on all the wonderful reviews, but would like to hear how some of you are handling this issue. I'm fully aware that swapping the speaker cable leads on both speakers will do the trick, but what do you do with the HT/BP input?

I'm looking to run the HT/SACD/DVD-A through this input and assume this input does not get the phase (polarity) inverted. I don't want to change speaker leads each time I change the music format.

How do you all manage? Leave it alone?

Thanks for the help.

SC

James Romeyn · « **Reply #1 on:** 19 Feb 2007, 04:20 pm »

It's a little surprising no one replied to this.

I am familiar w/ the 9.0 SE & the speakers with which it was once paired in a previously unheard system. The speakers are good & employ in-phase first-order xo's. Such xo's exhibit maximum transparency to phase inversion. Almost immediately after hearing the system I thought something was wrong. Indeed, the system polarity was not compensating for the 9.0's inversion. As soon as the speaker leads were inverted the sound went from C- or worse to B+ or better. Not subtle; in fact I'd consider an ABX test (no extra switches, just swapping the speaker cable leads).

A long way of saying, depending on your speakers, it seems important; though less critical w/ out-of-phase xo's (one driver goes + while the other goes -).

Probably the best alternative is a double-banana that can be unplugged, inverted, & re-inserted. I can't say I'm a fan of bananas regarding sound quality. Another solution might be gold-plated DPDT switches, either in your speakers or mounted in-line near the speaker binding posts. I have no idea how it might negatively affect performance. But at least you could invert by flipping a switch. Let us know what you do. Are your speakers in-phase or no?

If you do the switch, inline might be best. This may allow you to drill a small hole in the side of the switch, that would allow you to every 6 mos or so spray Caig Pro Gold onto the contacts.
My 2c.

TomW16 · « **Reply #2 on:** 19 Feb 2007, 04:37 pm »

I have read about polarity and from my perspective, I don't think that it can make that much of a difference since different CDs and different songs on the same CD can be recorded with reverse polarity.

I just built a pair of speakers and crossovers can reverse polarity which must be accounted for when wiring the drivers, however, once wired correctly, all the drivers will be in sync acoustically so there should be no issues.

This is of course different that reversing polarity on a single speaker.

Take care,

Tom

James Romeyn · « **Reply #3 on:** 19 Feb 2007, 04:54 pm »

Tom
At least one entire book was published on the subject of "absolute polarity" of audio signals. It's called "The Wood Effect" by Clark Johnson. Haven't seen any actual polls (though maybe I'll start one here). But I'd suspect a large majority of audiophiles agree it's quite audible, again, depending on the speakers.

On a decent system or better, w/ in-phase speakers, anyone can decide for themself. Listen carefully w/ familiar music (seems more audible w/ better/deeper bass).

Contrary to your statement, polarity is generally consistent in the recording chain. Audio engineers worth their salt are not in the habit of ignoring & swapping system phase. The reason being is exactly the subject of this thread. If you ignore polarity once, there is no fixed reference point. If you go back to a mix & remix something that is out of phase, esp bass, you are going to have one literally unlistenable pile of doo doo coming out of your speakers.

Kevin Haskins · « **Reply #4 on:** 19 Feb 2007, 04:55 pm »

I'd assume the HT bypass does nothing to the phase. Its the active stage that inverts the phase and you can just ignore it. Swapping the speaker leads is not going to make a difference.

The type of phase reversal that occurs to in a line stage is one where the entire signal is out of phase with the original. As long as phase is preserved across the frequency spectrum (50Hz is at the same time arrival as 20K) then it is completely inaudible. In a loudspeaker we worry more about phase because literally the music content from a tweeter may be slightly delayed from the arrival of the midwoofer/woofer signal. Believe it or not the ear is very tolerant of this "phase distortion" and it takes a fair amount to become audible.

In terms of people talking about crossovers that preserve phase, its mostly marketing. A first order crossover (single cap) on a tweeter inverts the phase by 90 degrees. Its basic physics and the laws don't change no matter how much you spend on marketing. Not even a full range driver without a crossover perfectly preserves phase. They radiate HF & LF content from physically different parts of the cone. Also... a standard driver uses a voice coil which is a small wound inductor (inverts phase @ different frequencies).

So... the moral of the story is to not worry about the phase inversion caused by the ModWright preamp. It causes the change across the entire frequency bandwidth with equal amounts. It will be entirely inaudible. In loudspeakers phase issues are a concern but mostly for the designers.

ted_b · « **Reply #5 on:** 19 Feb 2007, 05:14 pm »

Kevin,
I can't believe you are saying absolute phase in preamps is a non-issue and "completely inaudible". ?? Not. Quite audible to those of us who hear polarity issues. Heck, the wonderful Bent TAP preamp (and Dan's new LS36) both have invert phase capabilities built into the front panel and even the remotes. It's an important feature that I've been asking Dan to include for the past three years. I'm glad folks like Dan and John went the extra mile to include them.

I own a Modwright SWL 9.0 SE and have to say that I leave the amp in "swapped" invert mode so the phase is correct for 2 channel listening. When I engage the HT bypass I am listening to 5.1 or 7.1 output and the slight (but audible

) phase issues (yes, the HT bypass doesn't invert phase) across the front soundstage are less of an issue when you introduce a center channel and some surrounds (in my case, dipole sides and rears for movies, or identically matched direct radiating music rears for hirez mch music). If i'm gonna be doing some real serious evening-long 5.1 hirez mch listening, I'll swap the main amp leads for the evening. I was trying some bananas to make it effortless, but didn't like the sound. I use spades and spend the 1-2 minutes to swap them and the amp end; since I biwire I'm not opting to instead do the speaker ends...too much work.

James Romeyn · « **Reply #6 on:** 19 Feb 2007, 05:15 pm »

BTW, I've never seen anyone contradict the belief that speakers have different distortion products moving forward vs. inward. Looking at the mechanics of a speaker (the surround is rolled one way, it can't have the same movement both directions, ditto the surround & voice coil) this becomes more obvious.

An old trick to cancel the above defined uneven polarity distortion components is "Isobarik" woofer loading, but w/ a twist. Isobarik mounts one woofer behind the other to cut the enclosure volume in half. A twist is to reverse the physical relationship of each driver (one's rear faces the other's front). The cones move in reverse directions vs. their chassis (though they are wired out of phase, so the sum result is in-phase). This entire exercise is absolutely pointless if speakers don't distort differently depending on their direction. BTW, it works very well, at least below 100 Hz. It's expense & mass are the only reasons it's not an audiophile standard for bass.

The above is the speaker world's answer to Bongiorno's full dual-differential full-complementary amplifier topology, the world standard for high end power amplifiers. The uneven distortion products are cancelled.

This may be one reason absolute polarity is audible, again, depending on the speakers. If the original transient of the original music waveform started out positive, inverting it is audible. The distortion component of the speaker is altered when its polarity is inverted.

Again, w/ non-in-phase speakers, the test is probably moot.

Manufacturer's who install polarity switches on components are not doing it because they ran out of stuff to worry about.

Kevin Haskins · « **Reply #7 on:** 19 Feb 2007, 05:23 pm »

Quote from: ted_b on 19 Feb 2007, 05:14 pm

Kevin,
I can't believe you are saying absolute phase in preamps is a non-issue and "completely inaudible". ?? Not. Quite audible to those of us who hear polarity issues. Heck, the wonderful Bent TAP preamp (and Dan's new LS36) both have invert phase capabilities built into the front panel and even the remotes. It's an important feature that I've been asking Dan to include for the past three years. I'm glad folks like Dan and John went the extra mile to include them.

I own a Modwright SWL 9.0 SE and have to say that I leave the amp in "swapped" invert mode so the phase is correct for 2 channel listening. When I engage the HT bypass I am listening to 5.1 or 7.1 output and the slight (but audible ) phase issues (yes, the HT bypass doesn't invert phase) across the front soundstage are less of an issue when you introduce a center channel and some surrounds (in my case, dipole sides and rears for movies, or identically matched direct radiating music rears for hirez mch music). If i'm gonna be doing some real serious evening-long 5.1 hirez mch listening, I'll swap the main amp leads for the evening. I was trying some bananas to make it effortless, but didn't like the sound. I use spades and spend the 1-2 minutes to swap them and the amp end; since I biwire I'm not opting to instead do the speaker ends...too much work.

I'm sorry to disagree but the absolute phase of given program material is swapped any number of times when it passes through active circuits. Its just part of life.

In terms of loudspeakers, if you swap phase of a given driver relative to another you get cancellations. That causes issues in the FR domain and is obviously a problem. Your loudspeakers should be in phase with each other but it matters not if you have them both with swapped phase (negative & positive reversed) as long as you hold to using the same throughout the system.

In terms of multiple loudspeakers in different locations you start to get cancellations anyway because they are all out of phase relative to each other when you record the arrival time of the content. Once again.... its just part of life. You play a lot of different loudspeakers simultaneously your going to have them out of phase even though the original electrical signal is in phase.

I'm just stating basic physical properties here. This isn't a complex subject. In terms of being able to hear a phase swap and why a given manufacture includes it, I'd guess its mainly due to the marketing need. People perceive they need it and it has to be included to make people happy. I won't speak for Dan or John, they can do that themselves but I personally find it a complete non-issue.

James Romeyn · « **Reply #8 on:** 19 Feb 2007, 05:29 pm »

Kevin
I'm saying this as person who has never met you, but someone who is looking out for your best interest.

You are in the extreme minority on this issue.

I've worked in the recording business. Your statement about ignoring polarity are pure nonsense.

Do some research.

I'll post a poll if possible.

Have you ever done a listening test on a quality in-phase system? If not, you really should re-consider your position till you do.

Kevin Haskins · « **Reply #9 on:** 19 Feb 2007, 05:40 pm »

Quote from: RibbonSpeakers.net on 19 Feb 2007, 05:15 pm

BTW, I've never seen anyone contradict the belief that speakers have different distortion products moving forward vs. inward. Looking at the mechanics of a speaker (the surround is rolled one way, it can't have the same movement both directions, ditto the surround & voice coil) this becomes more obvious.

An old trick to cancel the above defined uneven polarity distortion components is "Isobarik" woofer loading, but w/ a twist. Isobarik mounts one woofer behind the other to cut the enclosure volume in half. A twist is to reverse the physical relationship of each driver (one's rear faces the other's front). The cones move in reverse directions vs. their chassis (though they are wired out of phase, so the sum result is in-phase). This entire exercise is absolutely pointless if speakers don't distort differently depending on their direction. BTW, it works very well, at least below 100 Hz. It's expense & mass are the only reasons it's not an audiophile standard for bass.

The above is the speaker world's answer to Bongiorno's full dual-differential full-complementary amplifier topology, the world standard for high end power amplifiers. The uneven distortion products are cancelled.

This may be one reason absolute polarity is audible, again, depending on the speakers. If the original transient of the original music waveform started out positive, inverting it is audible. The distortion component of the speaker is altered when its polarity is inverted.

Again, w/ non-in-phase speakers, the test is probably moot.

Manufacturer's who install polarity switches on components are not doing it because they ran out of stuff to worry about.

The suspension of all transducers is non-linear but that has nothing to do with phase when your talking about the transducer. I just designed a 6.5" driver and the suspension non-linearity is observable via the Klippel measurements. It contributes mainly to even-order distortion products and it measures the same no matter which way I hook up the test leads.

If you hook up a pair of them and run them such that their out of phase by 180 degrees you would get some cancellation of the linear distortion products similar to the discussion you are quoting. As a designer that is a trick that works with bass units but it becomes problematic at higher frequencies where you are trying to design for a specific polar pattern. It has absolutely nothing to do with absolute phase (no pun intended). If you swapped the phase on the system in question it would measure and sound exactly the same in either direction. It also only really works with the least audible types of distortion and is a method that is mainly practical for bass systems where our ear is much less sensitive to relatively larger amounts of even order distortion products. Its a solution to a non-problem if you design a transducer correctly to begin with.

James Romeyn · « **Reply #10 on:** 19 Feb 2007, 05:49 pm »

Kevin

1. Have you ever done a test on a good system w/ in-phase speakers?

If no, you might consider stopping saying it's in-audible. You are not obligated to answer, but it may shed a lot of light on the issue. You state it's inaudible, so that would imply you have tested your theory.

The pole is posted so you can read members vote shortly. Dan includes instructions on compensating for the phenomena in his preamp. I wonder why?

Kevin Haskins · « **Reply #11 on:** 19 Feb 2007, 06:37 pm »

Quote from: RibbonSpeakers.net on 19 Feb 2007, 05:29 pm

Kevin
I'm saying this as person who has never met you, but someone who is looking out for your best interest.

You are in the extreme minority on this issue.

I've worked in the recording business. Your statement about ignoring polarity are pure nonsense.

Do some research.

I'll post a poll if possible.

Have you ever done a listening test on a quality in-phase system? If not, you really should re-consider your position till you do.

Thanks for looking out for me.

I'm not adverse to being proven wrong on anything. I'm just trying to provide some people with advice based upon what I know. I don't pretend to be all-knowing but I feel pretty comfortable in my knowledge of how polarity effects the output of a transducer.

Kevin Haskins · « **Reply #12 on:** 19 Feb 2007, 06:42 pm »

Quote from: RibbonSpeakers.net on 19 Feb 2007, 05:49 pm

Kevin

1. Have you ever done a test on a good system w/ in-phase speakers?

If no, you might consider stopping saying it's in-audible. You are not obligated to answer, but it may shed a lot of light on the issue. You state it's inaudible, so that would imply you have tested your theory.

The pole is posted so you can read members vote shortly. Dan includes instructions on compensating for the phenomena in his preamp. I wonder why?

I guess I'd ask what do you define as a good system?

I have Dan's preamp, I build Hypex based amplifiers. I design my own loudspeakers rather than buying them nowdays. I assume there would be some people that consider my system good and others that don't.

I don't concern myself a whole lot with what other people think but that is because I'm a stubborn individualist guy who takes pride in bucking popular opinion.

mtodde · « **Reply #13 on:** 20 Feb 2007, 12:55 am »

As the owner of a SWLP 9.0 let me say that this makes a HUGE difference in the soundstaging and imaging in my system. It seemed to affect digital playback at least as much as vinyl. When I reversed the polarity of my speaker wires everything fell into place and I haven't changed them back.

I'm running the SWLP into an ARC VT100 Mk II via Cardas Neutral Ref and using Zu Wax biwires into Paradigm Signature 4s.

Bill Baker · « **Reply #14 on:** 20 Feb 2007, 02:02 am »

Hey folks, I think from preventing this thread from going in a bad direction, maybe we should agree to disagree and leave it at that?. Being one who will not get involved in debates, I won't post my opinion on phase but the way I look at it, what harm is there in swapping polarity on speak cables. It doesn't cost anything.

Just trying to keep some peace and save this thread from turning into a heated argument

James Romeyn · « **Reply #15 on:** 20 Feb 2007, 03:22 am »

Bill
I second your thoughts about keeping this civil.

I should not have, & apologize right now if I was uncivil in any way.

People who are interested in whether the difference is audible or not may click to the pole at Audio Central, which I encourage them to do.

I can think of no reason why anyone would fabricate anything like the audibility of absolute polarity, or be anything other than totally honest about their opinions. I trust the people who say they hear no difference just as much.

James Romeyn · « **Reply #16 on:** 20 Feb 2007, 03:42 am »

Quote from: Kevin Haskins on 19 Feb 2007, 04:55 pm

I'd assume the HT bypass does nothing to the phase...Swapping the speaker leads is not going to make a difference...
As long as phase is preserved across the frequency spectrum (50Hz is at the same time arrival as 20K) then it is completely inaudible...the moral of the story is to not worry about the phase inversion caused by the ModWright preamp...

Kevin
If your several rather concrete proclamations above are accurate, then apparently the designer is misleading readers by the very fact of mentioning its existence in the owner's manual. The mere fact of mentioning it ascribes some audible significance to it that you apparently state flat out does not exist.

Can you explain why a designer would mention something that "does nothing"...that "is not going to make a difference", that is "completely inaudible", nothing "to worry about"? One might surmise, considering the fact that the designer (I think) recommends compensating for the phenomena at the speaker leads, that the person who designed your preamp strongly disagrees (though I'm not speaking for him). I posit Dan indeed disagrees w/ your position.

If you just shared an opinion that you haven't heard it, in your opinion it doesn't exist, AND if you could just kindly put forth some moderately sensible reason why most audiophiles state otherwise, it would be, well, it would seem to make more sense, at least to me.

Bill Baker · « **Reply #17 on:** 20 Feb 2007, 03:52 am »

Hey Jim,
Let me start by saying that my post was in no way directed to you or any one individual but I would like to thank you for your polite and respectable response.

I did vote in the poll by the way.

James Romeyn · « **Reply #18 on:** 20 Feb 2007, 04:00 am »

As a person who has been to countless fires stared by line voltage, to what extent does one increase the liklihood of starting a fire by using a cheater, & even more so by inverting the line phase?

You used to be able to buy cheaters w/ nuetral line phase. No more. Now you must Dremel the ground blade down, which heats up the cheapo plastic insulator & melts it, which causes a loose blade (I don't ever recommend such out of fear of a lawsuit).

Kevin Haskins · « **Reply #19 on:** 20 Feb 2007, 04:08 am »

First, I don't either mean to offend nor do I take it from a simple disagreement. I don't like to cause problems in other people's forums either, especially Dan who I consider a friend.

With that in mind I'd rather not continue the debate in this forum. I'm happy to share my opinion and what I know or don't know concerning the matter in other places. Feel free to post in my forum and I'll continue with my thoughts on the subject.