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Cab DEP Parameter Measurements


pfsmith0
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What in the world does "Thump" mean? Does it go away when "RES LEVEL" goes to zero? And just what is "RES LEVEL"? I took my HD500 into the lab to find out. Since I didn't know what I was getting myself into I wanted to try to find an amp with flat frequency response, a mic with flat frequency response, and a cab with flat frequency response. If not flat then at least smoothly varying. If not over the whole frequency range, then at least over the range where Thump and Res Level do something interesting. So I picked:

 

Class A-15, adjusted for +/-2dB variation over a wide frequency range

121 Ribbon mic

1x12 Blackface 'Lux Cab

 

The results are in the PDF attached here. You can download the entire spreadsheet of data here.

 

I then set Thump = 0% and adjusted Res Level over it's range. You can see it basically acts as a boost below 1 kHz. It especially invokes a resonance at 80 Hz (for this cab at least).

 

I then set Res Level  to 50% (the default setting) and adjusted Thump over it's entire range. It has a similar effect but more restricted around the 80 Hz resonance. I suspect different cabs will have different resonance frequencies but the effect will be similar.

 

I then set Res Level to 0 to see what the Thump control does. Although it's effect is less, it does NOT go away. If you want to remove these effects then both Res Level AND Thump need to be set to 0.

 

Note that I did not measure DEP Decay. It is a slow time domain effect and can cause havoc in frequency domain measurements. I would get different measurements as I changed the sweep rate. The decayed signal would mix with the original signal and add constructively/destructively, depending on which frequency I was measuring and how long it took the sweep generator to get there. The measurement artifacts swamped any meaningful frequency response measurements.

 

So, I *think* this ends my adventures into HD500 amp/mic/cab DEP measurements. There should be total of 4 threads on this:

 

Amp/Pre frequency response and THD measurements.

Cab frequency response measurements

Mic frequency response measurements

And this one on Cab DEP measurements

Cab DEP Parameters.pdf

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Thanks for all your work on this.

 

During your testing, was there anything to indicate that the res level is structured off of fixed frequency points, or could there be an algorithm to pick which frequencies it's amplifying? Frequencies that might already stand out or have a slightly higher level than adjacent ones within a given resolution. This might have the effect of uniquely amplifying each amp/cab/mic differently, in which case picking flat response subjects might not be telling the whole story.

 

Or, another way to put that would be, if you did partial tests on more than one amp/cab/mic, was increasing the res level always operating on the same frequencies, independent of the amp/cab/mic selection?

 

But, if you don't know the answer, please don't measure more unless you really really like the tedious, mind-numbingly boring work I imagine this would take. Super grateful to you for taking your time for what you've done already. Thanks.

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Hi Duncann, no I did not measure Cab DEP parameters on other cabs/mics. However, it would not surprise me if they changed with each cab. That being said, I believe the effects will be similar. Thump will enhance some high-Q frequency in the 60-100 Hz region while Res Level increases the level over a broader low frequency region.

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  • 3 weeks later...

Hey pfsmith0,

 

could you please tell us more about the Decay? What does it do at 0% and what does it do when you slowly raise it? What would be the ideal setting in order to have the most natural sound out of it?

 

Thanks in advance!

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  • 4 months later...

I´m sorry but I´m not the author of these videos. This is the guy: https://www.youtube.com/user/mattmguitar/videos

 

The "RES LEVEL 0% and THUMP 25% trick" was something mentioned by Digital Igloo in the TGP forums as a personal preference. However, he also mentioned something like this is what the default should be, as the Res can only add resonance to the speaker IR.

 

That resonance is the thing that makes the POD HD sound fake to my ears.

 

Some quotes from different people:

 

The resonator is an add-on effect to the IR. I'm saying that the default "should" have been zero, but the sound designers obviously liked where it was when it was released. without the res it's just a plain old IR.

 

The other thing about these stock cabs is that the IRs were shot without a high pass. That's easily fixed in the DEPs, but it might also be the other half of the explanation on why some folks prefer third party IRs.

 

There are more things I do not like as default:

 

E.R: Another weird effect. I set this to 0-5%

Low Cut: Every cab sim on the pod needs a high pass filter, but is off by default.

Poweramp distortion: I´m no longer using the full amps models. Just the "Pre" versions (not removing the cabs) connected to a Roland GA-212 stereo amp (that works as a stereo 2X12 powered cab, due to the dual Line-in connectors).

Mic sims: By choosing the "Combo Power Amp" output mode the mic sims are deactivated. Choosing a Preamp model (without poweramp emulation), the cabs works just as a kind of EQ, without the annoying poweramp crossover distortion coming from the poweramp emulation.

 

Another useful trick:

Mid focus EQ: This filter can do wonders by placing it after the Mixer block. Settings: HP Freq 5-10%, LP Freq 60-70%, Gain 0-10% (usually 0)

This makes the amps sounds like a guitar amp should do: restricted in a limited range of frequencies.

Of course you can use the global EQ instead, but I think that doesn´t have effect in the "Combo Power Amp" output mode I´m using actually.

 

 

 

This way I´m pretty satisfied with the POD HD500 working as a Preamp+MFX unit, and my Roland GA-212 as a stereo powered cab.

I´m working in a setlist made from the ground up for this setup, with every amp in the POD HD including the Fully Loaded Bundle.

 

I think that bundle worth the price just for the Roland JC-120, the new Ampeg SVT and the Bogner Shiva. Amazing models. Seriously.

About the models that we had earlier in the pod, I especially like the Fenders (once you get rid of the ear-piercing highs or boomy bass) and Vox models (unfortunately the new AC30 Fawn didn´t replace the old one for me, as there is not enough dirt coming from the preamp).

 

You can hear the evolution of the modeling that line 6 used over the years just with a POD HD with the bundles installed. When you play over the "Podfarm" models included in the Heavy or Vintage expansion packs, you will hear the old s_hitty XT modeling coming back to your ears. Then change the patch to any of the old HD stuff, play for a while, and then switch to the new HD amps from the model packs. Next stop: Helix.

 

In any case I think the POD HD500 still worthwhile, even if only for the 4 or 5 amps (or preamps) you like best, and some of the effects.

 

The POD HD series has been a great product but certainly hard to setup properly. This is a shame becouse it can sound great but there is a bunch of things you should know to achieve it. Too much for the average guitar player. Too much even for the techies.

 

Very special thanks to people like pfsmith0, meambobbo, perapera, and many others (special mention to DI) that helped over the years to understand our tricky machines. Line 6 should send a Helix to you, as you have doing the work that they never did.

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Ed_Saxman: "Mic sims: By choosing the "Combo Power Amp" output mode the mic sims are deactivated. Choosing a Preamp model (without poweramp emulation), the cabs works just as a kind of EQ, without the annoying poweramp crossover distortion coming from the poweramp emulation."

 

Can you show where this is documented? I thought the Combo Power Amp would have disabled the speakers and the mic sims since the combo power amp (or effects return) would be expected to have its own speakers. And aren't the mics included with the speaker when creating the impulse responses - meaning they couldn't be separated?

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Captura%20de%20pantalla%202015-09-16%20a

http://foobazaar.com/podhd/toneGuide/setup#outputChart
http://foobazaar.com/podhd/toneGuide/quickGuide#outputModes

 


 I thought the Combo Power Amp would have disabled the speakers and the mic sims since the combo power amp (or effects return) would be expected to have its own speakers. And aren't the mics included with the speaker when creating the impulse responses - meaning they couldn't be separated?

 

As you can see in the screenshot, when Combo Power Amp mode is selected, the mic sims have no effect (no matter which mic you choose, they dont have any effect) but the "live-voiced cabs" are still there.

 

Then you can use full amps (including poweramp simulation) or Pre amp (without poweramp sim), and in both cases you can remove the cab sim or not.

 

To me, a Pre amp without cab doesn´t sound good with the pristine poweramp section of my Roland GA-212, maybe with a valve poweramp it does. YMMV. (edit: Read my next post, #14)

 

So, a Pre amp + "Live" Cab sim (no mics) was the better sounding option to me.

 

Turning off the resonance parameter from the cabs (in fact, turning off all three parameters: RES, THUMP and DECAY) gives you what is safe to think as a plain IR, without any resonance (Res) or EQ (thump, decay) added.

 

The THUMP and DECAY parameters still have effect even if RES is set to 0. (the opposite was incorrectly mentioned by some people, but that was wrong)

 

THUMP and DECAY affects basically to low freqs. I have found that something like: RES 0%, THUMP at 3 o'clock, DECAY at 4:00 (and a bit of Low cut) makes any guitar amp in the POD HD sound great with a bass guitar.

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Officially documented on "Page 4, Setup: Output Options" of the POD HD500 Advanced Guide v2.10

 

• Studio/Direct: Typically the best option when connecting “Direct†to a mixing console or recording device. This signal includes “Studio†  Cab Models, Mic Model and an “AIR†convolution to best emulate a mic’ed amp within a room.

• Combo and Stack settings: Optimizes your tone for connecting to an external amplifier. The signal includes “Live†Cab Models,with no Mic Model or “AIR†convolution, with a special EQ curve added for each.

 

• Combo Front & Stack Front: For connecting into the front input of a typical combo amp or amp head + external cab, respectively.

When choosing either of these Modes, you’ll see the following additional options for further tone shaping:
• Lows (Knob 2): Attenuates the low frequencies.
• Focus (Knob 3): Increases the overall midrange.
• Highs (Knob 4): Attenuates the high frequencies

 

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A quote from Meambobbo´s guide:

 

iv. Live-Voiced Cabs

The cab selections in non-Studio/Direct modes use "live-voiced" cabs which are a mild EQ effect designed to make whatever real cabinet you are using sound more like the cab model selected in the cab. Note: although you can change the selected microphone and there is a gap in audio as you change selections, it has no effect on the tone.

Misha.png

These have also been called cab simulation without mic simulation. "Cab simulation" is the wrong name. By itself, it does not come close to the frequency response changes made by real guitar speakers - it is designed to supplement, not replace, a real guitar cabinet (or speaker simulator/IR). Without such, "cab simulation" will sound nothing like a real guitar cabinet, mic'ed or not. It will be very harsh.

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as you can see what's written above here is official, and based on my direct experience with this device I can confirm that this is how it works..

 

the forum member "pfsmith0" with his CAB DEP measurements clearly showed that with resonance at zero, thump and decay can have still some residual effect on the IR frequency response, but even if set at their maximum value the effect on the final tone it is so little that is not audible at all or appreciable in any way..

 

therefore turning down to zero just the resonance is like turning off completely the resonator (i.e. with thump and decay doing nothing anymore).

I´m not agree with this part: "the effect on the final tone it is so little that is not audible at all or appreciable in any way.."

And definitely I´m not this sentence: "turning down to zero just the resonance is like turning off completely the resonator (i.e. with thump and decay doing nothing anymore)."

 

I´m using :

For guitar: RES 0%, THUMP 25%, DECAY 50%

For bass: RES 0%, THUMP 75%, DECAY 90%

 

In both cases with RES to 0%:

—The guitar usually sounds slightly better to me with Thump at 25% rather than 0% (or 50%). I leave Decay to default in most guitar presets, not being sure at that point if changes here improves the sound, or using different values in each patch.

—The bass, however, sounds (or feels) much better to me with Thump and Decay raised up.

 

 

So, IMO, the effect in the tone may be little, but it is still audible and apreciable.

After all, the interaction of each small amount of "effects" all together is what makes your whole tone in the end, isn´t it?

 

The manual simply lies when it says "RES 0 turns off the resonator".

Pfsmith0 himself said exactly the same in the first post, there is not contradiction with my experience:

"I then set Res Level to 0 to see what the Thump control does. Although it's effect is less, it does NOT go away. If you want to remove these effects then both Res Level AND Thump need to be set to 0."

 

 

By the way, you've mentioned that pfsmith measured the Decay but he said he didn't.

 

 

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Yep, exactly what Ed says. With RES=0, whether or not you can HEAR the small changes as you adjust Thump is another question. I could certainly measure it.

Yes, I did not measure Decay. I'm still trying to figure out how to best measure that. The waterfall videos are certainly interesting but I (personally) did not find them insightful. But I think an Impulse Response, which they mention in the video, is probably the right way to go.

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Thank you, pfsmith0!

By the way, what do you think about the sentence: "Resonance, Thump and Decay controls only be audible when the POD is in Studio/Direct mode" that appears in the manual? (screenshot in hurganico´s post)

 

Becouse I think that may be wrong too, at least with the "Combo Power Amp mode" I´m using. It is obvious that the RES parameter in Studio/Direct mode has a lot more impact, but I´m not sure that is really being completely bypassed in the rest of the output modes. (The same goes with Thump and Decay)

They said "not audible" but that not means "bypassed".

As a disclaimer, I´m just hearing it, not measuring it in any way, so I cant be absolutely sure.

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I only measured Studio Direct because 1) I wanted access to the cabs and mics, and 2) that's how I use it.

 

That's how I used to use it, too. Straight to a Roland Octa-Capture (S/PDIF and/or XLR) in a pair of EVENT ASP6. I am still doing for recording or playing bass.

But I definitely prefer the sound of my 2x12"powered cab to play the guitar. Most especially since I found the alternative output modes, and the clean and natural sounding PRE versions of the HD amps (including live-voiced cabs) in a pristine Roland poweramp section. PA/Studio/Recording sound Vs. plain guitar amp sound.

 

Anyway, yesterday I tried to feed pink/white noise from my iPad to the Aux-in of the HD500, then I monitorized the output with Logic Pro X´s EQ. But, since I´m an IT guy, I don't have the knowledge to understand many things while watching a EQ curve. So, my question to you are :

Do you know any EQ analysis method for dummies, that I could use? My target is just to confirm if the Resonance, Thump and Decay controls are efectively bypassed in all the alternative output modes, or if they are simply "inaudible" (in the manner of Line6, you know)

 

Keep at it. Keep telling yourself as you adjust thump and decay with res at zero that you can hear a difference. Your brain might start telling you something different than before.

I guess you meant to be sarcastic, but there is certainties in your words: The auto-suggestion is a powerful thing.

 

That´s why my rational mind needs a scientific evidence like the pfsmith0 measurements to be completely sure.

 

In fact, I would prefer that the answer to the question I'm asking were a resounding "NO, the three parameters of death have absolutely no effect on the alternative output modes: they are absolutely bypassed, so forget that and play music".

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I guess you meant to be sarcastic, but there is certainties in your words: The auto-suggestion is a powerful thing.

That´s why my rational mind needs a scientific evidence like the pfsmith0 measurements to be completely sure.

 

In fact, I would prefer that the answer to the question I'm asking were a resounding "NO, the three parameters of death have absolutely no effect on the alternative output modes: they are absolutely bypassed, so forget that and play music".

 

Not sarcastic at all.

 

Even knowing that there is objective data, your brain can still easily override that to convince yourself otherwise, turning an objective reality into a subjective one, at least for the observer. It's even likely. You eventually become an inseparable part of the system whether you like it or not. So does an objective reality exist at all? Does a tree...lol.

 

Or maybe a person's hearing system is really fine tuned to hear the subtle differences.

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Hi Ed, what you look for are changes to the shape of the white noise frequency content. Try studio direct first and adjust Low Cut first as that's the most drastic effect. Do you see a difference?

 

If so then move on to Res Level and then Thump, as they have less and less effect. Then do the same for different for the other output modes and see if those changes still happen.

 

If not, then the white noise source is not sufficiently stable (after all, it's noise and changes over time) or not precise enough and you'll have to move to sinewave sweeps (which is what I did). An alternative is to use a lot of averaging with white noise. That tends to settle things down and may allow you to see more detail, but it takes more time.

 

Let us know what you find out!

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Quote

 

If not, then the white noise source is not sufficiently stable (after all, it's noise and changes over time) or not precise enough and you'll have to move to sinewave sweeps (which is what I did). An alternative is to use a lot of averaging with white noise.

Great advice, thank you!. The Sine Wave works better than the white noise. I tried with Sweeps but I found that a 100Hz sine wave is enough for my humble tests. The app I´m using is Tone Gen Pro by performance audio (IOS).

 

QuoteHi Ed, what you look for are changes to the shape of the white noise frequency content. Try studio direct first and adjust Low Cut first as that's the most drastic effect. Do you see a difference?

Yes I do.

CUT 0%:

Captura%20de%20pantalla%202015-09-17%20a

 

CUT 100%:

Captura%20de%20pantalla%202015-09-17%20a

QuoteIf so then move on to Res Level and then Thump, as they have less and less effect. Then do the same for different for the other output modes and see if those changes still happen.

Not happening. Cab Parameters does nothing in any other output mode. Not at all. Even the "Low Cut" is useless.

 

 

Dammit! Duncann was right!.

Homer: All right brain, you don't like me, and I don't like you. But let's just get me through this, and I can get back to killing you with beer.

Brain: It's a deal!

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BTW, the new "Global EQ" (Fimware 2.62) works in all the alternative Output modes. (although some of them already had EQ controls)

 

This way we can use a high pass filter despite the lack of the Cab Low Cut parameter. Or both high and low PF without using the Mid focus EQ.

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