Ampeg is mixing cabs!

[johnpbass]

Come along, Nurse Ratched has your afternoon meds ready.

Just another pin prick - there'll be no more...

 

[Duder]

I know that some of you don't like the idea, but it appears that Ampeg is ready to sell pre-mixed rigs.

Ampeg Portaflex PF800 Head, PF-410HLF 4x10/PF-115LF 1x15 800W Bass Amp Stack

[Invalid or Expired Link Removed]

I posted this link a little over 2 years ago. I learned to not start these threads anymore, haha.

Perhaps I Misunderstand "Mixing Drivers"

 

[tfer]

One experiment that I tried, using the same cabs that I always use, failed terribly.

My rig is a Hartke HX 115, a Hartke 2.5XL (2X10" + a 5" 'tweeter').

My regular amp is a Hartke LH500. My backup is an Ampeg PF500.

Out of boredom, one day I split the signal using the stereo outputs of my Boss ME20B, sending one channel the the LH500+HX115 and the other to the PF500+2.5XL.

I rolled off all the lows on the PF500 and give the mids a nice big bump, then I trimmed the highs and mids from the LH500. Then I turned them up...

The phasing nearly made me seasick! No bottom end at all, and my inner ears protested wildly!!

I then tried each amp separately, powering both cabs and it sounded fine...

Looking at those charts, I wonder if there isn't a slight time difference in processing the signal between the two amps, and if that tiny lag caused the problems?

 

[David Jayne]

One experiment that I tried, using the same cabs that I always use, failed terribly.

My rig is a Hartke HX 115, a Hartke 2.5XL (2X10" + a 5" 'tweeter').

My regular amp is a Hartke LH500. My backup is an Ampeg PF500.

Out of boredom, one day I split the signal using the stereo outputs of my Boss ME20B, sending one channel the the LH500+HX115 and the other to the PF500+2.5XL.

I rolled off all the lows on the PF500 and give the mids a nice big bump, then I trimmed the highs and mids from the LH500. Then I turned them up...

The phasing nearly made me seasick! No bottom end at all, and my inner ears protested wildly!!

I then tried each amp separately, powering both cabs and it sounded fine...

Looking at those charts, I wonder if there isn't a slight time difference in processing the signal between the two amps, and if that tiny lag caused the problems?

"no bottom end at all..." My guess is that something in your signal chain flipped the electrical phase of the signal going to one cab vs the other.

 

[tfer]

"no bottom end at all..." My guess is that something in your signal chain flipped the electrical phase of the signal going to one cab vs the other.

I'd generally agree, but the signal, aside from being split using the stereo outputs, was unaffected.

That's what was so confusing.

 

[wintremute]

I posted this link a little over 2 years ago. I learned to not start these threads anymore, haha.

Perhaps I Misunderstand "Mixing Drivers"

It appears that I was quite late to notice that was for sale! So, it's nothing new. I can't wait to see this thread again in a few years.

 

[Duder]

It appears that I was quite late to notice that was for sale! So, it's nothing new. I can't wait to see this thread again in a few years.

I'm sure there will be many like us who are baffled by this setup when so many find it to be an atrocity. I don't honestly care what cabs people use as long as it sounds good from out in the crowd.

 

[JimmyM]

I'm sure there will be many like us who are baffled by this setup when so many find it to be an atrocity. I don't honestly care what cabs people use as long as it sounds good from out in the crowd.

One man's atrocity is another man's chocolaty goodness

 

[David Jayne]

I'd generally agree, but the signal, aside from being split using the stereo outputs, was unaffected.

That's what was so confusing.

Could be one amp is out of phase with the other, either at the input or output. Maybe try the test again, with one speaker lead phase-reversed. Betcha.

 

[ThisBass]

One experiment that I tried, using the same cabs that I always use, failed terribly.

My rig is a Hartke HX 115, a Hartke 2.5XL (2X10" + a 5" 'tweeter').

My regular amp is a Hartke LH500. My backup is an Ampeg PF500.

Out of boredom, one day I split the signal using the stereo outputs of my Boss ME20B, sending one channel the the LH500+HX115 and the other to the PF500+2.5XL.

I rolled off all the lows on the PF500 and give the mids a nice big bump, then I trimmed the highs and mids from the LH500. Then I turned them up...

The phasing nearly made me seasick! No bottom end at all, and my inner ears protested wildly!!

I then tried each amp separately, powering both cabs and it sounded fine...

Looking at those charts, I wonder if there isn't a slight time difference in processing the signal between the two amps, and if that tiny lag caused the problems?

Those nasty artefacts may happen if
- amp A shows reverse polarity vers amp B
- cab A shows reverse polarity vers cab B
- in stereo mode the effect board shows reverse polarity of wet channel versus dry channel.

Especially modulaten effects in stereo mode which show a timevariant relative phase due to "modulation" with timevariant delay may cause audible effects which then may cause a listener to feel like seasick. The seasick effect becomes very strong if in stereo mode one of the stereo out channels is of "reverse" polarity.

That all said,
my (nasty) Boss CEB-3 bass chorus does exactly THIS.
Boss calls it kinda "space" sound but, I rather would this "space" chorus call as design error.

 

[johnpbass]

One man's atrocity is another man's chocolaty goodness

I'm tempted to add that to my sig line - giving you full credit of course! LOL!

 

[tfer]

Those nasty artefacts may happen if
- amp A shows reverse polarity vers amp B
- cab A shows reverse polarity vers cab B
- in stereo mode the effect board shows reverse polarity of wet channel versus dry channel.

Especially modulaten effects in stereo mode which show a timevariant relative phase due to "modulation" with timevariant delay may cause audible effects which then may cause a listener to feel like seasick. The seasick effect becomes very strong if in stereo mode one of the stereo out channels is of "reverse" polarity.

That all said,
my (nasty) Boss CEB-3 bass chorus does exactly THIS.
Boss calls it kinda "space" sound but, I rather would this "space" chorus call as design error.

I understand that, but all effects were bypassed.

 

[ThisBass]

I understand that, but all effects were bypassed.

So I'm pretty sure you have got a reverse polarity issue with either amp or cab.

Another possibility for a "seasick" sound may happen if response of HT cab A overlays way too much with woofer response of cab B. Although there is no phase issue per se it does not sound well if HT and woofer share same mids bandwidth. Personally I prefere to discribe the sound this way, sounds like day after a drunken night

 

[JimmyM]

I'm tempted to add that to my sig line - giving you full credit of course! LOL!

Well that would be better than using a line CL400Peavey stole from me and giving him the credit

 

[Hoochie Coochie Man]

Which line did CL400Peavey steal from you? Was it the one about liking your tone to sound like a wet fart?

 

[ThisBass]

Please explain in your own terms the phenomenon that is displayed by my mixed narrow stack.

At relatively modest volume easily achievable by a single cab, the biamped stack sounds pristine, whereas the full range stack is but ok.

I describe this as a lack of coherance between the phase responses of the two cabs. In other words they are summing well enough but not perfectly. What do you call it?

- HT of cab A overlays with woofer mids response of cab B and vice versa
- different partial membrane resonances of woofer at mids
- different woofer voicing at mids
- different system damping of cabs caused by different cab system filter alignment
- group delay issues caused by different cab system filter alignment

If damping of cabs differs too much the amplifier has got no chance to control both cabs just the same way.
Which cab does the amplifier should give a preference? The amplifier only gets an total average feedback of both cabs. Cab A receives too less of amplifier control while cab B gets more of amplifier control and vice versa
In biamping mode this issue is solved.

 

[Downunderwonder]

- HT of cab A overlays with woofer mids response of cab B and vice versa
- different partial membrane resonances of woofer at mids
- different woofer voicing at mids
- different system damping of cabs caused by different cab system filter alignment
- group delay issues caused by different cab system filter alignment

If damping of cabs differs too much the amplifier has got no chance to control both cabs just the same way.
Which cab does the amplifier should give a preference? The amplifier only gets an total average feedback of both cabs. Cab A receives too less of amplifier control while cab B gets more of amplifier control and vice versa
In biamping mode this issue is solved.

what's so wrong with characterising group delay as phase response? Nobody but you has that issue.

 

[JimmyM]

Which line did CL400Peavey steal from you? Was it the one about liking your tone to sound like a wet fart?

No, "Use your ears and what's between them and you'll be fine." Although he paraphrased it...I said, "Use your ears and the gray goop between them..."

 

[ThisBass]

what's so wrong with characterising group delay as phase response? Nobody but you has that issue.

Explained in rough words,
As phase on it's own does not cause any delay (in science) means it's not valid to try to address things like delay to phase shift

See the pics I posted above. There is strict differentiation of phase and delay.
The samples for shifted phase start at just the same "point" on time axis, while delay (as is) starts little later on "time" axis.

Different phase with cabs does not mean the signal with "bigger" phase shift starts something delayed. Even the signal with bigger phase shift starts at just the same time like the signal with smallish phase shift.

That's totally different to group delay which is actually delay of time.

edit,
the group delay is totally independent of actual phase shift. Group delay depends on shape of the phase response. If phase was steady 180 degree from DC to 20kHz then Group Delay equals zero
So actual phase has nothing to do with Group Delay while Group Delay is the number how much of time the signal is actually delayed.

Nobody but you has that issue.

even engineers sometimes miss the math at some content.

 

[Hoochie Coochie Man]

I was just having some fun Jimmy. You had a good one a long time ago. I wish I could remember it.