Speaker phase observation and question?

From the measurements section of Stereophile's review of your speakers:

The Silver 8's step response on its tweeter axis (fig.7) shows that the tweeter and midrange unit are connected in inverted acoustic polarity, the woofers in positive polarity. More important than the polarities (see "Letters," November 2014, p.11) is the fact that the decay of each unit's step smoothly blends with the start of the decay of the next step lower in frequency, which suggests optimal crossover design.

Enjoy!  Regards,
-- Al
 

Thank you Al, very informative!

OP,

So, positive polarity means a + voltage causes the driver to move towards the listener and away from the cabinet.

A speaker designer may need to flip the polarity of individual drivers to get the correct frequency and phase alignment across the crossover region. It is rather rare for a flat baffle, multi-way speaker to get the drivers all lined up in positive polarity.

When this happens the convention is to wire the largest driver, the woofer, in positive phase, and then flip drivers going upwards as needed to align with the next driver down.

For instance, almost all 2-way speakers end up with the tweet reversed. My LM-1 however happen to have aligned in positive phase.

https://speakermakersjourney.blogspot.com/2016/02/the-lm-1-bookshelf-version.html

But this was a result of a great deal of luck with driver sizes, location, and crossover design.

Best,


E

chewie70, My speakers are factory wired inverted by default (woofer wise - tested with battery). This default inverted phase gives me more bass (and fuller nicer sound) while opposite phase brings more treble/mids.  My amp and the source (DAC) are non-inverting, but many recordings might be.

Some speakers, e.g., Vandersteen, are purposely designed to have all drivers in the same, positive phase.  As Mr. Squires implies, Vandersteen does not use a flat baffle.

" I have made a couple of observations. When connected in positive phase (red - red, black - black), the speakers put out pretty substantial bass, but the mids and treble are somewhat subdued. Upon reversing the phase, the mids and treble open up substantially, and the bass becomes somewhat subdued. To my ears, I actually prefer the reversed phased."

Somethings wrong. Even though your speakers don't use first order xovers, you shouldn't have that much change. Can you list your amp and speaker cables? Be very specific with your speaker cables. (brand, model, single or biwire,)

Vandersteen also uses first order filters which don't honk up phase
...
and his crossovers are incredible feats of engineering without a big baffle to smooth frequency response - a big baffle is a nice flat horn

wiring a driver out of phase to attempt to fix a steep filters phase shift is NOT excellent crossover design...
but the magazine guys love it...

" Vandersteen also uses first order filters which don't honk up phase "

I have 3 pairs. I also had the exact same pair of speakers as the OP, and was able to do a direct comparison. Yes, Vandersteen is a better design, but I don't think that's the problem. If you look at the OP's description of the of complaint, it looks like a problem that needs to be fixed.

" When connected in positive phase (red - red, black - black), the speakers put out pretty substantial bass, but the mids and treble are somewhat subdued. Upon reversing the phase, the mids and treble open up substantially, and the bass becomes somewhat subdued."

I've seen several times where speaker cables were not labeled correctly. If the cables are terminated as a biwire config, and a mistake was made on either the high or low cables, but not both, it sounds like the OP's problem. One way the bass is correct, but the highs are not. After the swap, the highs are good, but the bass is now bad. The problem keeps going back and forth, and if you're not aware of what's going on, It'll drive you crazy.

Keep in mind that this is a guess on my part because we have no idea of what the OP's system is.

Thanks for the informative response Erik.

sfall, I don't believe there is anything horribly wrong with my system, this just confirmed what I was hearing and seeing with the polarity test.

To answer your initial question, my rig is Simaudio pre/DAC, Emotiva XPA 2-channel 300wpc amp, and Audio Art single shotgun run cables, with custom jumpers that mirror the cables.

Although I hear substantial differences between lows and highs when changing polarity, the system sounds amazing either way. I think if I could leave the bass in positive polarity, and reverse the polarity of mid/treble, the sound would be perfect. I should note that I am almost completely deaf in one ear; so when I say a "substantial" change, it my just be that I am hearing frequencies differently than others??

Thank you to everyone else that has taken time to comment, this has been for informative.

" I think if I could leave the bass in positive polarity, and reverse the polarity of mid/treble, the sound would be perfect. "

I'm not sure I understand what you're doing to change polarity. If you have high order xovers in your speakers, its true that the drivers will start and stop at different times. But keep in mind the designer knows this and factors it into the overall design. Its not something you would ever want to fool with. If you want to change polarity on the entire signal, you probably have a button for this on your Sim. Its a common feature on preamps and dacs. Just to be clear, I'm not saying that what you are doing is wrong, I just can't figure it out.

" Audio Art single shotgun run cables, with custom jumpers that mirror the cables."

I'm not sure what you mean here. Anytime someone says shotgun speaker cables, it means you are running 2 separate pairs of cable from the amp to the speakers. (For ease of connection, you can have the amp ends of the speaker cables terminated to one set of connectors. Its still a shotgun design). So, if this is what you have, the jumpers are not needed. It actually negates most of the positives gained from the double biwire.

OP:

You may want to look into room correction such as DiracLive which can correct this. If you use a PC as a source you may even be able to play with it for free.

Best,

E

I'll vote with Eric on this...I've been applying room correction for a couple of decades now, adjusting for 'flat' as much as is practical given the existing space, the stuff within it, and the drivers applied to it.  Once one gets 'used to it', it doesn't make sense to do anything else IMHO.

Given my penchant for omnis, I have to do a bit more 'sampling', but I've the means to do so and the method for averaging the samples.  We all have our manias....;)

Hi sfall, to answer your question, I am swapping the (+) and (-) to change polarity. However, since the speakers are internally wired in both positive and reverse polarity, and change that I make will always have one set of drivers in reverse polarity. Even if my pre/DAC had a phase switch (which it doesn't), it wouldn't make a difference and the outcome would be the same.

My cables are a double run (i.e. shotgun) into single terminations, so not bi-wired.

Hi erik and asvjerry! Thanks for your input on room correction. I have briefly looked at it, but really know nothing about it. From what I understand, you have to have a dedicated computer to run it? I have also looked at the DEQX system, but am not enthused by the price. I wish that there were audiophile grade EQ's available, as that would probably solve the problem as well.

Years ago there was quite an audio controversy over whether inverse phase could be "heard".  Nothing ever came to a head, but based on my own observations I believe it can, however subtle.  I have for nearly thirty years owned Spiels and love Spicas, and I believe totally coherent slanted panel and positive crossovers are part of the "magic".

You might want to see if you can audition Thiels (older versions) or Vandersteins or Spicas to see if you are "sent to heaven" by the phase coherence.  

Thanks harrylavo! Although I have no desire to change my speakers, absolutely love them 95% of the time, I will look into your recommendations to see if I come across anything that truly Wow's me.

Interesting !!! Would not know about the manufacturer's inverting phase on mids/highs, that you would have to ask or check it out with some tech guys.

The results obtained with the bass are normal, and are you absolutely sure that your ears did not trick you, since when there is less bass, the mids and highs will appear to come out more, and vice versa. Maybe you prefer and advantage these frequencies in your personal sound analysis, and it would just mean that your speakers (and/or associated amps) are not very well balanced for your ear preferences. 

Another tech reason would be that inverting the bass could be pushing /helping the midrange cone, if the later is not isolated from bass resonance in the cabinet.

In a good many speakers the phase angle is significantly different for the woofers than it is for the midrange and tweeter. If the woofer has a significant negative phase angle while the midrange and tweeter are quite positive, inverting the phase of the woofer will bring them into better coherence. 

I also have a pair of MA Silver 8s that I fiddled with phase for years, and was never quite happy with the results. They play loud, they play clean, but I never was completely happy with imaging, soundstaging and coherence.
Bought a pair of Vandersteen 2Cs and am loving them.
Kept the 8s for a second system. My wife likes them better. YMMV

Tom

Man, I’m sorry I have to jump in here:

In a good many speakers the phase angle is significantly different for the woofers than it is for the midrange and tweeter. If the woofer has a significant negative phase angle while the midrange and tweeter are quite positive, inverting the phase of the woofer will bring them into better coherence.

This is too confusing phase angle with polarity. The polarity is either positive or negative. Applying the (+) of a 1.5V battery to the (+) terminal of a driver will result in the driver moving OUT. Reverse the battery and the driver will go IN.

Because drivers as well as their crossovers result in phase angles that may not add up correctly, matching the drivers so their total output adds correctly across the crossover frequency often results in the need to invert the polarity of drivers.  Something else not thought about is the time. In a flat baffle, a tweeter arrives about 0.1

My guess is that 99% of two-way systems have the tweeter in negative polarity. This is a good thing, because the alternative would be a deep null.

Designers deal with driver polarity consideirng only a pair of drivers at a time. By convention, the woofer is in positive polarity. Then the woofer/midrange is considered. If necessary, the midrange will be inverted. Based on the phase angles of the midrange and tweeter the polarity of the tweeter is considered. This time the tweeter may or may not be inverted.

The size, depth, placement of the drivers, the angle of the baffle, the order of the filters (1st, 2nd, etc.) all play into whether drivers will need to be inverted.

For goodness sakes, no one should be inverting individual drivers, that way lies madness unless you have the right tools or background information.

There are designers like old Thiel and current VanDerSteen who make polarity and phase coherense an absolute priority, and then buy or have drivers made that can work well in these configurations. It is not rocket-science, but neither is it proven to be desirable above all else, and often has risks associated with it.

Best,

E

By the way, if anyone wants to learn about speaker design, and how drivers and crossovers work together I have quite a bit of documentation, including real-time simulation tools you can use to play around and look at some of these concepts.  Please visit my LM-1 design page, here:

https://speakermakersjourney.blogspot.com/2016/02/the-lm-1-bookshelf-version.html

The files and design info are 100% free for music lovers. :) Haters have to pay.

Thanks everyone. This has been extremely informative, and I have learned far more about speaker design than I could have imagined.

@erik_squires My Focal 936's are exactly opposite of what you suggest about woofer polarity. The midrange and tweeter are in positive polarity while all 3 woofers operate in negative. 

The point of my comment was to point out how speakers are reactive and not subject to the superficial presumption that when voltage is applied a driver reacts predictably. A lot of people don't consider that a driver and crossover become more or less capacitive or inductive when driven by a signal and that the current draw that actually drives the speaker can be significantly ahead of or behind the voltage. 

Hi @kosst_amojan,

Well that is unusual, but not the end of the world.

Well, I consider that quite predictable, this is what math and simulations are for.

But your comments seemed to be mixing up phase and polarity.

Best,

E

Polarity is absolute; + or -, phase angle varies as a function of the frequency. Completely different concepts.

Polarity should not make that much difference. Unless you go one speaker reversed polarity and the other normal. 

That said - you are deaf in one ear.  In those with full hearing the brain does a lot of processing using BOTH ears - perhaps you are experiencing more masking from bass frequencies in one polarity vs the other because you only hear with one ear.

Hi Guys,  most of you know that I've been building speakers for 35 + years... Overall this is a great thread..
I noticed a couple of comments of phase angles.. Kalali mentioned that they are very different.
Phase angles show us how current rides with the voltage within the speaker... if current rides in front of or behind the voltage, you will see the large rises or dips in phase angles. So the phase angle changes how a speaker sees power...
Phase/polarity is important in the sense of keeping your individual drivers moving in unison... when a speaker is 180 degrees out of phase,  one driver has complete excursion moving outward and another driver has complete excursion moving inward. 
In theory when designing a crossover,  6db per octave gives you 90 degrees out of phase, 12db produces 180 degrees out of phase, 18db per octave produces 270 degrees out of phase and 24db per octave produces 360 degrees or full circle back in phase.
The most used crossover (which I don't use at all) is 12/12 slopes,  that means that the slopes between 2 drivers is 12db up from the woofer or mid to the tweeter and 12db down from the tweeter... Again, in theory, this is 180 degrees out of phase.  A designer can simply switch polarity and bring phase/polarity back into alignment.  A ton of things go into a design so that basic theory is not absolute,  but this is an accurate look at the theory behind speaker phase/polarity. 
I hope this little explanation helps, 
Tim

Tim, thanks for another of your always valuable inputs about speaker design.  Regarding:

In theory when designing a crossover, 6db per octave gives you 90 degrees out of phase, 12db produces 180 degrees out of phase, 18db per octave produces 270 degrees out of phase and 24db per octave produces 360 degrees or full circle back in phase.

I believe this theoretical model assumes that the impedances of the drivers themselves are purely resistive, and of course they are not.  Is that the basic reason why the phase angles of a speaker's impedance, as shown for example in John Atkinson's measurements in Stereophile, typically vary up and down over the frequency range by several tens of degrees, and swing between negative (capacitive) phase angles and positive (inductive) phase angles at various frequencies?

Thanks again.  Best regards,
-- Al
 

I really again, suggest anyone who wants to learn more would do so with the LM-1 simulation files. You can review the frequency, electrical and acoustic phase of the drivers by themselves, and then see how the crossover adds to it.

Best,


E

Thanks Al for your kind words,  you are always a gentleman.
Remember, I was discussing how it affects phase/polarity...
For phase angles,  an amplifier is feeding a signal to a speaker,  as you know, a speaker can vary wildly in impedance load by frequency... As the signal goes through these variances,  the current and voltage are working their way through it at different rates... If current is following behind the voltage, it will create a positive angle,  but if the current is leading the voltage, it will create a negative angle.  It is because of this, that I am a big believer in impedance compensation networks on speakers (even single cone drivers) I've never heard it adversely effect a speakers sound, but in many cases, I have heard improvement...
Next,  purely resistive speakers... I've had great luck with Ribbons,  many, even most have a load that appears purely resistive to an amplifier... Not all, big ribbons will destroy an amp. 

Hi  @almarg 

Looking at my answer, I see that I tip toed around your question, this still isn't a complete answer, but contributing...
We look at phase angles varying by impedance, so yes,  if we change crossover points or slopes,  we can affect phase angles to some degree. Anytime that voltage and current cannot travel together, they are no longer in phase themselves... A speakers impedance along with each drivers own characteristics, ie load variations, qes, voice coil induction etc causes these variations.  I hope this makes sense, 
Tim

Sorry, for those of us that are a bit slow, the phase angle of a speaker obviously changes with frequency and so does the impedance. Furthermore, it appears that a combination of a low phase angle and low impedance puts "stress" on the partnering amplifier. So, this begs the question why would a "good " speaker designer design a speaker that would create such condition. In other words, how does sound quality - whatever that means in objective terms, benefit from such design.

Tim & Erik, thanks for the excellent info and the informative link, which I’m still going through.

Kalali, first, although the term "impedance" is commonly used to simply refer to a number of ohms, to be precise a speaker’s impedance is a vector quantity, meaning that it is comprised of both a magnitude (the quantity that is measured in ohms) and a phase angle (measured in degrees). If the impedance is purely resistive at a given frequency the phase angle will be 0 degrees at that frequency; if it is purely inductive (hypothetically speaking; no speaker will have an impedance that is even close to being purely inductive at any audible frequency, or it would not be able to consume any power at that frequency) the phase angle will be +90 degrees; if it is purely capacitive (again, hypothetically speaking) the phase angle will be -90 degrees.

Also, as has been mentioned above, the phase angle of the impedance describes the amount by which voltage leads current (in the case of a positive/inductive phase angle) or voltage lags current (in the case of a negative/capacitive phase angle), at a particular frequency.

But to address your question, I suggest that you take a look at this thread. The entire thread is well worth reading, but note especially the latter part of Atmasphere’s post dated 1-9-2017 (beginning with "I feel like several points need clarification ..."). The short answer is that sound quality **does not** benefit from low impedance design, but other factors such as cost and marketability may. With those factors deriving in part from the fact that solid state amps can supply more power into low impedances (up to a point, of course) than into high impedances. The background and previous experience of the particular designer, and the kinds of designs he or she is most familiar with, also seem likely to be factors in many cases.

Best regards,
-- Al

Hi Almarg,

I am definitely on team "easy to drive speakers." Get easy to drive speakers and a lot of amps will sound really great.

Get demanding speakers, and your amp costs may go up considerably.

So make sure if your speaker is demanding that it's really worth the cost of ownership. Being able to tell amps apart is not why I buy speakers anymore. :)

Best,

E

Likewise, Erik. Putting it another way, I prefer the dollars I choose to invest in an amplifier to go as much as possible toward sound quality and build quality, rather than a lot of that investment simply going toward watts and amperes.

Best regards,
-- Al  

Hi Kalali,    well to answer your question... quality would not benefit from a design with a combination of low impedance and low phase angle,  but when you are designing, if you want a very detailed speaker, you may choose a very stiff cone,  you may want a low qts for a lean sound or a higher qts for a sealed box design, You may want a driver that can cover 4 or 5 octaves or a driver that has no peaks or one that only has a very smooth rolloff on the top end or one with a low fs.  What it all comes down to,  is that when you have a design in mind,  you tend to find a driver that comes as close to  what you are after in sound quality and deal with phase angles the best that we can. 

Thanks for the excellent and thorough explanations. I had completely missed the interrelationship between the impedance and phase angle and voltage/current interplay referenced in the posts. It all makes sense now.

Hey chewie70....late post, but I've 'been away'/out of town/preoccupied...

For eq and room correction, I run a dedicated/in line Behringer 8024 (yeah, PA stuff...but it works nicely and is reasonably 'clean') and the APO eq off Source Forge with the Peace interface on the 'puter...

https://sourceforge.net/p/equalizerapo/wiki/Documentation/

One for room eq, the other for 'tweaks 'n tricks'; monitor the results with an RTA and see what's going on...

Between the 2, I could probably bend an acoustic 2x4, but that's more for grins than accuracy. *L*  I'm not so much a 'purist' of late, but having 'been there/done that/smoked the t-shirt. ;)

I just amuse myself of late...my approach to the 'hobby' isn't as 'serious' as some, but to each...*S*

Hoping to be helpful, J

A ton of pre amps invert phase 
 

@twoch is right. Especially minimalist tube preamps. A single stage, single ended gain stage always inverts.