Ampeg's response is true and correct. But essentially boils down to 'No, they aren't specifically designed to work well together but they might." This is the reply you'd get from most companies who make cabs.
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Ampeg is mixing cabs!
- Thread starter wintremute
- Start date
Science wise it is not valid just to consider different phase response of stacked cabs versus relative phase which is caused by room reflections.
As different phase response of different but narrow stacked cabs does not cause any relative delay it's not valid to predict something like relative phase which was caused by delay, just like it clearly happens with room reflectons.
Narrow stacked cabs couple acoustically together as just to one source independent of any (relative) phase response deviation.
Different phase response of cabs does NOT relate in relative delay between several cabs as long as the cabs do couple acoustically
Lots of "engineers" try to predict delay caused by different phase response of different cabs. That's a totally mistake of (electro-) acoustic science and can be easily disproved by math.
So any question asked if different cabs may cause mud due to different relative phase has to be denied.
It's not possible to explain any mush sound by different phase of different cabs.
However different cabs which don't match "soundwise" do show different phase response anyway but, it's not the relative phase deviation which was responsible for mush sound.
As different phase response of different but narrow stacked cabs does not cause any relative delay it's not valid to predict something like relative phase which was caused by delay, just like it clearly happens with room reflectons.
Narrow stacked cabs couple acoustically together as just to one source independent of any (relative) phase response deviation.
Different phase response of cabs does NOT relate in relative delay between several cabs as long as the cabs do couple acoustically
Lots of "engineers" try to predict delay caused by different phase response of different cabs. That's a totally mistake of (electro-) acoustic science and can be easily disproved by math.
So any question asked if different cabs may cause mud due to different relative phase has to be denied.
It's not possible to explain any mush sound by different phase of different cabs.
However different cabs which don't match "soundwise" do show different phase response anyway but, it's not the relative phase deviation which was responsible for mush sound.
Al Kraft
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It never seems to be anymore of a deadlock to me than admitting that any single cab with one, and only one driver (and no other bass cabinets within a 5 mile radius), will sound great in every venue with every head and every bass. The truth is that you can minimize your chances of having problems when using more than one cab, but there is no way to ensure you will always get the exact tone you're after with any cab or set of cabs in all circumstances...and from the musicians I've heard, it would seem there are folks with vastly different tone goals out there.
So you might get some "negative" mush with matching cabs. As long as you don't do the trial you'll never know.
Passinwind
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- Dec 3, 2003
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This one thinks it's great if you actually use well considered driver choices. That does not include using two standalone bass cabs, pretty much ever.
I think the mixed cabs police would not write you a ticket for that.
I bet they don't have these types of arguments over in the Fender Rumble thread.
Signal direkt transfered from speaker to listener
View attachment 1181229
Signal delayed by wall reflection. relative phase caused by delay equals to 765 degree
View attachment 1181230
total signal at listener position if both signals direct and reflected signal show same level at listener position
Cabinaet A with a phase shift of 90 degree at 60Hz
View attachment 1181232
Cabinet B with a phase shift of 135 degree at 60 Hz. That's relative phase shift of 45 versus cab A which was quite a very lot of deviation for different ported MI cabs
View attachment 1181233
As both cabs are stacked very close there is coupling of the two sources at 60Hz. So there is a total signal that looks like
View attachment 1181234
For comparison two matching cabs with identical phase shift of 90 degree at 60 Hz gives a total signal that looks like
View attachment 1181235
As a 90 phase shift turns the sine into cosine waveform even matching cabs do some nasty things to the signal, Fortunatelly it doesn't hurt the total sound by no means
The total signal of the stacked cabs (either matching or mixed) can't cause mush in the room while the reflected total at listener position might do it.
View attachment 1181229
Signal delayed by wall reflection. relative phase caused by delay equals to 765 degree
View attachment 1181230
total signal at listener position if both signals direct and reflected signal show same level at listener position
Cabinaet A with a phase shift of 90 degree at 60Hz
View attachment 1181232
Cabinet B with a phase shift of 135 degree at 60 Hz. That's relative phase shift of 45 versus cab A which was quite a very lot of deviation for different ported MI cabs
View attachment 1181233
As both cabs are stacked very close there is coupling of the two sources at 60Hz. So there is a total signal that looks like
View attachment 1181234
For comparison two matching cabs with identical phase shift of 90 degree at 60 Hz gives a total signal that looks like
View attachment 1181235
As a 90 phase shift turns the sine into cosine waveform even matching cabs do some nasty things to the signal, Fortunatelly it doesn't hurt the total sound by no means
The total signal of the stacked cabs (either matching or mixed) can't cause mush in the room while the reflected total at listener position might do it.
Last edited:
Passinwind
I know nothing.
- Dec 3, 2003
- 23,078
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- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Come along, Nurse Ratched has your afternoon meds ready.
Let me share with you another example why phase can't tell the truth.
Frequency response of two different MI bass cabs
Phase response
around 165 degree phase shift both cabs at 50Hz so everything looks to be fine at 50Hz. Based on pure phase the signal at front baffle of each cabinet looks like
Based on phase response it looks like we would get two coherent signals for both cabs at 50Hz which add to a total of
Now lets have a look to the group delay
around 6msec of delay at 50Hz yellow cab versus white cab
So the signal of the yellow cab versus white cab looks for 50Hz in relation like
Due to group delay (which is not phase) both cabs will add to a total signal like
lets have a final look to the frequency response,
the yellow response looks close to Tschebyscheff alignment while the white one looks more close to Butterworth filter alignment characteristic. Each alignment provides distinct characteristic for frequency response (roll-off shape) and damping and group delay. The frequency response is shown with the pic, the group delay is discussed above, the phase response is very close but, besides group delay the damping differs a very lot which makes it delicate to mix both cabs.
Phase response does match well (as discussed above) but other variables don't.
Flat earth folks and also mixed police folks very likely will never understand why phase on its own can't tell the truth
Frequency response of two different MI bass cabs
Phase response
around 165 degree phase shift both cabs at 50Hz so everything looks to be fine at 50Hz. Based on pure phase the signal at front baffle of each cabinet looks like
Based on phase response it looks like we would get two coherent signals for both cabs at 50Hz which add to a total of
Now lets have a look to the group delay
around 6msec of delay at 50Hz yellow cab versus white cab
So the signal of the yellow cab versus white cab looks for 50Hz in relation like
Due to group delay (which is not phase) both cabs will add to a total signal like
lets have a final look to the frequency response,
the yellow response looks close to Tschebyscheff alignment while the white one looks more close to Butterworth filter alignment characteristic. Each alignment provides distinct characteristic for frequency response (roll-off shape) and damping and group delay. The frequency response is shown with the pic, the group delay is discussed above, the phase response is very close but, besides group delay the damping differs a very lot which makes it delicate to mix both cabs.
Phase response does match well (as discussed above) but other variables don't.
Flat earth folks and also mixed police folks very likely will never understand why phase on its own can't tell the truth
Attachments
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[rant on]
flat earth "phase police" folks argumentation frequently reminds my on just the same argumentation of oldish back in the day flat earth "flat clipping line" folks who tried to explain overheating of drivers with DC [rant off]
flat earth "phase police" folks argumentation frequently reminds my on just the same argumentation of oldish back in the day flat earth "flat clipping line" folks who tried to explain overheating of drivers with DC [rant off]
This Westlake Audio speaker is in Prince's Paisley Park studio.
Another Westlake cab. Looks like it would make a great sounding bass cab.
There's nothing wrong with mixed speakers if they are designed to work together. Studio monitors are a good example. These days, monitors tend to be self powered, with multiple dedicated amps, one for each speaker or within the same group. This allows for even better fine tuning. There are always solutions.
In any case, one less snarky TB'er (albeit an informed one) absent from the amps forums is a good thing. I'm not so sure the snark I see there is directly proportionate to the number of "bad" ideas shared by inexperienced posters, but it's uncalled for nonetheless. The subject of amps/cabs can be daunting and the Amps forum has to be one of the less friendly places on TB to people who aren't educated on the subject. There are plenty of engineers on the FX side that can manage not to be nasty or condescending, so the Amp gurus can do it too. The problem isn't even so much them, if at all, but the vociferous lemmings that attach themselves to every word someone smarter than they are says as if they had known it all along.
Al Kraft
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Only one way to know for sure...kick the tires and light the fires...View attachment 1181310 So this won't work for me?
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?
