Double Bass It's just a silly Phase I'm going thru...

[Don Kasper]

@fdeck -
Mr. Deck, would you be able to offer an explanation (to me & others?) of the following scenario:
(In early 2024) My D string was overly sensitive,"hot" (is "feeding back" the proper term?), and, consequently, was abnormally louder (& infinitely sustaining) than any other open string (while using my WW Electracoustic Amber Light thru my 10" Eminence DIY cabinet.) I use Double Banana plugs in my DIY cabs, and I tried simply reversing the +/- orientation of the Dbl Banana (after powering down!).
This IMMEDIATELY solved the open D string sensitivity. (I have since fabricated a "phase reversed" speaker cable for that particular setup, which works perfectly.)
Can you explain (in LAYMAN'S terms!!!) why that "phase reversal" is so simple, yet effective? (Is the +/- phase simply how the speaker cone FIRST moves - inward or outward? This has been my Neanderthal understanding of Speaker Phase.)
Are there other factors that come into play?
Thank you for your time, expertise, and ongoing contributions to TB.
Don Kasper (Neanderthal)

 

[DoubleMIDI]

There are a lot of amplification stages in an amp. Typically every transistor inverses the phase. So it depends on the amp design but also on electrical orientation of the pickup if the number of serial inversions is even or odd.
EQ can also add frequency dependent phase shifts that can attenuate or boost frequency ranges.
Also the distance between speaker and bass top or back has a time delay that when it gets back to the pickup acts like a comb filter, specially if things get louder.

I think there is no simple answer beyond “just try the phase switch” and it might be totally different if you only change one thing in the loop.

I know, you asked Francis and I think he wants to answer your question, but I wanted to give you some hints that the question might not be simple to answer.

 

[Chris Fitzgerald]

Can’t find the iconic Kasper “Banana mittens” pic, but why am I not surprised that this same person uses banana plugs? As always, EEMWCB

 

[Don Kasper]

Can’t find the iconic Kasper “Banana mittens” pic, but why am I not surprised that this same person uses banana plugs? As always, EEMWCB

Trolling Troll Spotted!!! "Terms and Rules" have been violated!!!
Can a Moderator please step in and Moderate???
Sheesh. $90 a year and I have to contend with this nonsense?
(jk)
Mr. Banana Mittens

 

[Ryan in PDX]

Is the +/- phase simply how the speaker cone FIRST moves - inward or outward?

Yes.

Are there other factors that come into play?

Yes.

I tried simply reversing the +/- orientation of the Dbl Banana

This is inverting the polarity of the speaker.

I think there is no simple answer

Agreed.

My polarity switch helps sometimes, and not other times. Explaining why would take rather a long time, and likely spoil your afternoon nap time (or mine, at least). YNTMV

 

[Don Kasper]

Yes.


Yes.


This is inverting the polarity of the speaker.


Agreed.

My polarity switch helps sometimes, and not other times. Explaining why would take rather a long time, and likely spoil your afternoon nap time (or mine, at least). YNTMV

OK...I guess.
Still "Waiting For The Deck".
Thx.

 

[Chris Fitzgerald]

Don, in all earnestness, it’s like putting the left mitten on the right hand, and vice versa. IMFO.

 

[Don Kasper]

Don, in all earnestness, it’s like putting the left mitten on the right hand, and vice versa. IMFO.

So, you've heard my bass playing!
(Still "Waiting For The Deck"...)
I hate it when Mods are on Summer Vacay and have time for Unregulated Trolling.
Thanks? I Thank Not.
Mr. B. Mittens.

 

[Sam Reese]

What are the individual tensions of each string on your bass?

 

[Don Kasper]

What are the individual tensions of each string on your bass?

I have no idea, (I don't believe that is a worthwhile or quantifiably answerable question, IMFO). but my carved Juzek is remarkably "even" acoustically. My Phase Reversal experiment DRAMATICALLY solved the "hot note/string" issue immediately. I did this on a live gig, FYI.
I was prompted to try this, as I had listened to an interview of bassist/engineer Steve Rodby, about 15 yrs. ago, where he spoke of the importance of signal chain "Phase" issues in DB amplification.
Thanks,

 

[Chris Fitzgerald]

So, you've heard my bass playing!
(Still "Waiting For The Deck"...)
I hate it when Mods are on Summer Vacay and have time for Unregulated Trolling.
Thanks? I Thank Not.
Mr. B. Mittens.

I must protest: I am absolutely regulating this trolling. I just wish that could find the damn pic! It was epic. I think the search feature must still be indexing under the new software.

But the open D thing is real. Recently, while recording a solo intro for a forthcoming video on intonation, it reared its ugly head. Both the ceiling, the second DB across the room, and the acoustic guitar behind me just lit up and started ringing every time I played the open D, to the point where I had to cram mutes under the strings of the other bass and the guitar… nothing to do about the ceiling.

I look forward to hearing from the esteemed Dr. Deck.

 

[dylanjohnson]

A little taste of classic TB here. Thanks, gents. I’ll be here with my popcorn waiting for Fdeck.

 

[Don Kasper]

I just wish that could find the damn pic!

Do I have to do EVERYTHING in this thread??
Sheesh...
Thanks & Yer' Welcome a Bunch, Chris.

 

[Don Kasper]

But the open D thing is real.

Yours seems to be a simple case of Sympathetic Vibration - not really a mystery and very solvable with Neanderthal-Level Tools. (Good Job, Chris!)
I'm Still W.F.T.D. to delve into the phenomenon of the Amplified D, versus the Phase Reversed Amplified D.
OMG! - I sound like a Pretentious Music Theory Ph.D. candidate!!!
OUCH!

 

[fdeck]

Here's my hand-waving explanation. The bass is acting like a microphone. An acoustic wave from the speaker will make the belly move in and out, producing a bit of a signal in the pickup.

I've noticed under really adverse stage setups, with loud players, that my bass and amp can pick up and amplify things like the kick drum, or the bass keys of electric piano.

So it works like microphone feedback. If the acoustic wave reaching the bass produces a signal that is amplified and reproduced in the same direction, it will reinforce itself and can keep getting louder and louder. If reproduced in the opposite direction, it will quickly dampen itself out.

Now for phase switch. While technically correct, in this context, it means reversing the polarity of the signal. A preamp-that-shall-not-be-named has a switch that does this. Swapping the speaker terminals will do the same thing, as BANANA JACK has observed.

Is it a panacea? Unfortunately not. The reason is that the frequencies reaching the bass from the speaker all have different wavelengths, and thus different phase. There are also time delays in the bass and amp. For this reason, I think that in practice the best that can be hoped for is a reduction in the effect of feedback, rather than killing it outright. And feedback shows itself in a degradation of tone and dynamics, even when it's below the level of actually howling or squealing.

Getting beyond that simplistic level is actually a lot of math and theory, that the electrical engineers eat for breakfast, but I'm just an old industrial physicist, and didn't study that stuff in depth.

And yeah, the D string. Maybe it's just the most lively string, who knows.

Magnetic pickups are less susceptible to feedback because the strings themselves are acting as ideal filters. I used a homemade magnetic pup on my Kay for a few years before switching to a piezo. It got me through some stoopid loud gigs, but those gigs have kind of dried up for me.

 

[Don Kasper]

Here's my hand-waving explanation. The bass is acting like a microphone. An acoustic wave from the speaker will make the belly move in and out, producing a bit of a signal in the pickup.

I've noticed under really adverse stage setups, with loud players, that my bass and amp can pick up and amplify things like the kick drum, or the bass keys of electric piano.

So it works like microphone feedback. If the acoustic wave reaching the bass produces a signal that is amplified and reproduced in the same direction, it will reinforce itself and can keep getting louder and louder. If reproduced in the opposite direction, it will quickly dampen itself out.

Now for phase switch. While technically correct, in this context, it means reversing the polarity of the signal. A preamp-that-shall-not-be-named has a switch that does this. Swapping the speaker terminals will do the same thing, as BANANA JACK has observed.

Is it a panacea? Unfortunately not. The reason is that the frequencies reaching the bass from the speaker all have different wavelengths, and thus different phase. There are also time delays in the bass and amp. For this reason, I think that in practice the best that can be hoped for is a reduction in the effect of feedback, rather than killing it outright. And feedback shows itself in a degradation of tone and dynamics, even when it's below the level of actually howling or squealing.

Getting beyond that simplistic level is actually a lot of math and theory, that the electrical engineers eat for breakfast, but I'm just an old industrial physicist, and didn't study that stuff in depth.

And yeah, the D string. Maybe it's just the most lively string, who knows.

Magnetic pickups are less susceptible to feedback because the strings themselves are acting as ideal filters. I used a homemade magnetic pup on my Kay for a few years before switching to a piezo. It got me through some stoopid loud gigs, but those gigs have kind of dried up for me.

Thanks, Mr. Deck, (and not a minute too soon, I might add....You have no idea of the chaos, noise, and general TB turbulence that my inquiry set into motion!)
Also - I "get" about 25% of your lesson.
So, as a Neanderthal, I still am amazed (and thankful ) at the massive sonic improvement as a result of my simple experiment in PhaseOlogy. (With a hat-tip to Steve Rodby in his interview.)
Thanks, again, for your time, expertise, and patience.

 

[Don Hergert]

Uhmmm, where can I order the banana mittens? They look like they might be helpful for sore hands.

 

[Don Kasper]

Uhmmm, where can I order the banana mittens? They look like they might be helpful for sore hands.

Amazon has an abnormally large selection of said "...mittens".
See below. If you dare.
Sheesh. Do I have to do everything in this Thread?

 

[RBrownBass]

Props on the thread title- absolutely fantastic song. There's a whole YT video about how it was recorded.

 

[Don Kasper]

Props on the thread title- absolutely fantastic song. There's a whole YT video about how it was recorded.

They say "Big Boys Don't Cry", but this thread almost brought me to tears!
(jk)
Thx.