GRFR vs FRFR - Is FRFR really needed for pure Guitar AMP/CAB profiling/modelling?

1) well, as you probably know, your guitar speaker acts as a sort of low-pass filter for the sound your amp produces. Most modelers emulate the speakers frequency response already. So if you amplify your modelers output, and use a guitar cab, you would "filter" the sound twice, which may sound cool, but does not reproduce the originally intended sound. using a normal PA speaker (or in guitar terms FRFR) your sound is only filtered once through the modelers cab emulation, and the PA speaker is flat. Or you would use a real guitar cab and disable your modelers cab emulation. That may be a valid choice but omits some advantages of modeling (more on that later)

2) didn't read that, but a thing to be aware of is that in cheap-ass speakers the crossover point at 1kHz or so between mid-low driver and horn is very critical. If your speaker is designed badly that frequency range is very harsh. Maybe they meant this?

3) brrrrrrrr, stay away from this. if you would take an impulse response from the DEQ + cab (hmmm work intensive...), Kemper would probably be able to pull this, BUT you are misusing your gear, trying to let a guitar cab reproduce things it isn't designed for, using extreme EQ settings, and therefore extreme phase anomalies. Correcting in the frequency domain leads to problems in the time domain and vice versa, and can mess with your available amp power.

To get back that 'more on that later' thing: In my experience as FOH tech, the big advantage of a modeler is that you can go straight into FOH with your line-outs, which gives you less stage noise from loud amps, and a clearer sound (no bleed from the drums into the guitar cab mic). Both make it easier to get a good FOH sound without ear-bleeding noise levels (and thats what we get paid for). In an ideal situation the only one allowed to make noise on stage is the drummer, there are only in-ears and no amps or speakers on stage. You can ask yourself why you would bother with a cab? FOH can deliver my guitar through the monitor mix? But there are many people who want to let their guitar feedback, or don't use a PA (some bands just put vocals through PA). Then a cab may prove handy. That just leaves the question: FRFR or guitar? Depends on what you'll like, but with FRFR you can choose the guitar cab your modeler emulates on the spot, with a physical guitar cab, you're stuck with that cab, but you have the sound of a real cab instead of a miced cab...

Hi cags , welcome!
1) you are right about that. But you need a frfr system after the kpa that is flat in the frequency spectrum you wanna hear, of yo u want to enjoy the cabs grom the kpa. So for guitar that is about 80 Hz up until 4500 hz. A system that is flat in it' s output in this range is broadly available in the form of pa and monitor speakers. Maybe some some specialized speaker cabs are topped of at the high end but i'm not sure. Of course if you play baas guitar or acoustic guitar through the kpa other frequenties are to be produced by your speaker
2) if yo u have a good profile, there are no nasty high frequencies when played frfr, at least that is my experience
3) the eq of the kpa is not as sophisticated as the bheringer. I guess what the video describes is an option, but i think it will be degrading the sound quality because with this kind of equalising you introduce all kind of phase problems, not to mention that a static equalizer can never compensate the dynamic eq differences of a speaker cabinet.

Quote from cags12

This is my first post and would like to say Hi to everyone.

Quick Intro: Although I am not new to modelling (I have owned a PODX3 for years), I am fairly new to the world of FRFR. Now that I am considering buying a KPA and wanting to take full advantage of the modelling, I have dug into researching about all the FRFR technologies and have read tons of topics that have made me wondering some things.

I have learned that current FRFR CAB manufacturers have also some either Passive or Active (DSP) GRFR options. i.e. Camper 112 and 212 (bypassing the tweeter), Gemini 2 (DSP), Matrix 112 (DSP), etc.

I totally understand the concept of Full Range vs Guitar Range as well as the Flat Response part which I believe is the most important part of the equation as far as I understand.

What I am trying to understand is the following:
1. If modellers/profilers mainly look to, well, model/profile Guitar Amps and Cabs which use Non Flat Guitar Range Speakers, why do we really need the extra range available on FRFR Cabs?
The Flat response part is a given so lets ignore that as well as other applications like playing music or other non guitar instruments.

2. On FRFR I have read that the high frequencies make stuffs sound non optimal specially for High Gain sounds.
Where does this high frequencies come from if the profiled sound did not have it? and why do we want to keep using FRFR if that is an issue?

3. Although not optimal, the experiment on the link below seem very interesting to me and supposedly Fractal can do it without extra EQ gear.Can the KPA flatten the Freq Response of a profiled CAB?

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Answers to this question would give me a better understanding that would allow me to make a better decision when buying my gear.

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Hello Cags12,

First of all, that YouTube vid, while perhaps well-intentioned by the author, is pretty much rubbish. The author of the video was NOT transforming a guitar speaker into a FRFR speaker. What he was doing, was using an external EQ filter to smooth out the natural peaks and troughs of a guitar speaker, to better approximate a "Flat Response". In no way shape or form does this process turn a guitar speaker into a Full Range system. Furthermore, the quasi "Flat Response" that he achieved is just that...quasi. The problem is not so much the attentuation of the "peaks", as it is the artificial "boosting" of the "valleys" in the frequency response curve, in order to replicate a "flat" frequency response. Effectively, the EQ device is making approximations and summations to nearby frequency bands, in order to reproduce a certain frequency that isn't present in the original source speaker output. This results in artificial artifacts and distortions.

The YouTube video demonstration is not in any way, shape or form turning a traditional guitar speaker into a "Full Range" system...as it is not magically giving the speaker the ability to accurately reproduce frequencies beyond it's capabilities (particular in the higher frequency ranges). A "Full Range" speaker would reproduce the full frequency range of human hearing, which is 20 Hz through 20 kHz (within +/- 3 dB) . In actuality, "Full Range" in the industry is probably more like 40 Hz-15 kHz, +/-3 dB. In either case, a traditional guitar 12" single-driver guitar speaker cannot come close to this bandwidth and accuracy. In general, a traditional 12" guitar speaker has a dramatic roll-off of high frequency content beginning around 5 - 6 kHz.

So, the question remains why would one prefer a true FRFR system with the KPA? The reason is to leverage the advantages and the capabilities of the KPA's Cabinet Profiles. In general, the individual guitar speaker/cabinet contributes 75% of the over-all "tone" of a guitar amplifier. This is readily apparent when hooking up and playing different tube guitar amps through a single guitar speaker/cab. At the same gain and volume level, they will all (to a first approximation) sound pretty much the same. Conversely, if you hook up and play a single tube amp head through various speakers/cabinets...you will likely hear markedly different tones, timbres and colors.

This is where an FRFR system really shines. Since an FRFR monitor is designed to accurately reproduce the input signal it is fed, it will leverage the advantages of the Kemper's (or alternative modern digital modeler) ability to reproduce the frequency response of a specific guitar speaker/cabinet. While it is certainly important and desirable for such a system to have a high degree of "flatness" and neutral response (accuracy) in it's sound reproduction...that is not the only criteria. SOME OF THE UNIQUE tonal characteristics and harmonic content of any given amp-guitar speaker combination happens above 5 kHz. This can be enough to give a particular amp-cab system it's unique "finger-print". The ability to accurately reproduce the unique behavior occurring at higher frequencies (Full Range) is just as important as reproducing the signal with transparency and neutrality (Flatness).

This becomes even more pronounced with cleaner tones, which tend to be less compressed and have a greater frequency response. If you also want to have the ability to faithfully reproduce acoustic tones...then an FRFR is an absolute necessity. So, in general, an FRFR system will always have an advantage in terms of flexibility and versatility, over what has been recently advertised as a "GRFR".

Quote from cags12

This part flipped upside down my head :). I do not quite understand. So there are high frequencies on the range of Full range >10.500 that the profiler captured during the profile process that are reproduced again when playing even though the reference sound did not come from a full range system (regular guitar speaker)?
sorry if this is a stupid question

Yes, to a degree. Just because a traditional (typical) guitar speaker has significant HF roll-off (usually beginning around 5-6 kHz), it does not mean that all of the frequencies above 6 kHz are imperceptible or inaudible. In fact, some of the acoustical energy in this particular frequency range is what gives a particular amp-speaker combination it's sine qua non "air" and "ambience". While frequencies greater than 10.5 kHz are of diminishing (in)significance for electric guitar, there can still be a lot of character living in the 6 - 9 kHz bandwidth, depending on the particular guitar speaker/cab.

Be that as it may, a GRFR might be a satisfying and acceptable solution for home use, and even as a personal monitor on stage. However, if one is ultimately concerned about hearing (as close as possible) what the audience hears through the FOH/PA...then, IMHO, it makes an awful lot of sense to skip the GRFR and go straight to a bona fide FRFR monitor solution.

Cheers,
John

EDIT -- There is another significant advantage to an FRFR compared to a GRFR. If you are like me, and tend to tweak 3rd-party commercial profiles by swapping / switching the stock Cabinet with other Cab profiles (or the same Cab with different mics and/or mic positions)...you will notice a greater difference and variation in your tone when using a true FRFR monitor, as compared to a GRFR. Again, IMHO, a bona fide FRFR is just more conducive to leveraging the advantages of the KPA's fantastic Cabinet profiles.

Quote from cags12

1. GRFR (guitar range, flat response) is NOT equal to GR (NON-flat response or regular Speaker cab). That being said, I want to highlight that the intention here is not to process the audio through 2 Cabs (modelled and real). only the modelled and the flat response one (GRFR or FRFR).

forget about the GRFR and FRFR thing: once uou are above 3000-4000Hz you have a crossover in your system, so i cant imagine GRFR has better sonic qualities than FRFR. A real guitar cab has no crossover, so thats one "design flaw" less (as in passive crossovers have inherent design flaws). Active crossovers + time alignment is a different story... I think of those terms more as marketing terms anyway: if a speaker is FRFR its just a fullrange speaker, maybe packaged in guitar cab aesthestics... FRFR is only used as a term in the guitar world, not in the PA world...

PS: if you use a full range speaker you can play your backing track through it too...

Quote from jpoelmans

forget about the GRFR and FRFR thing: once uou are above 3000-4000Hz you have a crossover in your system, so i cant imagine GRFR has better sonic qualities than FRFR. A real guitar cab has no crossover, so thats one "design flaw" less (as in passive crossovers have inherent design flaws). Active crossovers + time alignment is a different story... I think of those terms more as marketing terms anyway: if a speaker is FRFR its just a fullrange speaker, maybe packaged in guitar cab aesthestics... FRFR is only used as a term in the guitar world, not in the PA world...
PS: if you use a full range speaker you can play your backing track through it too...

Hello jpoelmans,

There may be some confusion, here. When cags12 talks about a GRFR, he is talking about either a single driver monitor, or a 2-way in which the HF driver has been disabled. No cross-over circuit is applicable in the first case, and in the second case the cross-over has been bypassed.

Also, the term FRFR is most certainly understood and used in the Pro Audio market.

Cheers,
John

To be clear: A GFR cab is NOT a simple 2-way cab with disabled tweeter.

We have a new cabinet, which can do both, FRFR and GFR, by toggeling a little switch. Search for BlueAmps "Beast", if you are interested.

Quote from Gitarrenschlumpf

To be clear: A GFR cab is NOT a simple 2-way cab with disabled tweeter.

We have a new cabinet, which can do both, FRFR and GFR, by toggeling a little switch. Search for BlueAmps "Beast", if you are interested.

Fair enough. On your particular system ("Beast"), I presume that the toggle switch on your passive model switches the cross-over point, and/or engages a filter to cut off frequencies greater than approx. 10 kHz (in GFR mode).

GFR in the way we do it, are speaker cabinets with speakers inside which do the whole spectrum of GFR. And that´s the advantage, better than a coax, if you play electric guitar. The toggle switch switches off the tweeter, that starts at 10 kHz. Everything under 10 kHz comes out of the 12 inch speakers.

Quote from Gitarrenschlumpf

GFR in the way we do it, are speaker cabinets with speakers inside which do the whole spectrum of GFR. And that´s the advantage, better than a coax, if you play electric guitar. The toggle switch switches off the tweeter, that starts at 10 kHz. Everything under 10 kHz comes out of the 12 inch speakers.

Hello Gitarrenschlumpf,

I am now confused...

So, what you are saying is EXACTLY what I originally wrote -- which you felt the need to correct. The toggle switch simply turns off the tweeter.

We may have a language barrier, here.

I think what you may be trying to explain, is that with your GFR product ("Beast"), the primary 12" driver is not a typical "guitar" speaker. Instead, it has been specially designed/selected in order to provide an extended frequency range with a relatively flat response, up to 10 kHz.

I am not sure why this necessarily has any advantage over a coaxial system which has a properly implemented cross-over circuit. On my XiTone passive 1x12 FRFR, there is a switch which provides a -3 dB pad on the HF driver, which can be activated to achieve more of a "GFR" frequency range and response, if desired. I actually never use this pad / switch.

Cheers,
John

Sorry. My first post wasn´t meant to be a correction to your post above.

Tha advantage to a coax in GFR-mode:

The coax speaker has 2 different voice coils. The tweeter sits behind the LF-driver. So all the stuff above the x-over point comes out of the speaker a little later. In GFR mode also, if it´s just a 3 dB pad on the HF.

The GFR cabs in the way we build it have only one voice coil. So the whole sound comes out at the same time.

Quote from cags12

Coming back to the original discussion.
Reading that sentence on the quote, you are basically saying what I thought initially that a GFR Cab that has a x-over point over 10.5 kHz would be more than enough to reproduce any profiled/modelled Cab. That would bring me back to my original question in the topic title.

I am interested in knowing the point of view of @Gitarrenschlumpf about this topic. if we are not playing tracks or any other instruments, would not a GFR Cab be enough and FRFR overkill? (Strictly speaking about guitar).

Hello Cags12,

I am sure @Gitarrenschlumpf will respond to your question, as well. First of all, you may find a dedicated GFR perfectly suitable for your needs. However, even with the Blueamps "Beast" cab/monitor, the unit is designed as a FRFR system, with the ability to also operate in "GFR" mode.

It all comes down to how you use your KPA, and how much versatility you need. Keep in mind my closing statement in an earlier reply:

Quote from Tritium

There is another significant advantage to an FRFR compared to a GRFR. If you are like me, and tend to tweak 3rd-party commercial profiles by swapping / switching the stock Cabinet with other Cab profiles (or the same Cab with different mics and/or mic positions)...you will notice a greater difference and variation in your tone when using a true FRFR monitor, as compared to a GRFR. Again, IMHO, a bona fide FRFR is just more conducive to leveraging the advantages of the KPA's fantastic Cabinet profiles.

Cheers,
John

Quote from cags12

I believe you guys are comparing apples with oranges here.

The coaxial design on the XiTone I take is to achieve FRFR, not GFR and what @Gitarrenschlumpf mentions on the Blueamps with a broadband driver, is restricted to achieve GFR. Both devices use a 2 driver approach for FRFR, one coaxial an the other non-coaxial. Or I am wrong?

My understanding is that to achieve GRFR the XiTone only reduces the HF with the -3 dB pad, and Blueamps totally shuts down the HF driver. right?

Yes, you are right in both questions.

Quote from cags12

Coming back to the original discussion.
Reading that sentence on the quote, you are basically saying what I thought initially that a GFR Cab that has a x-over point over 10.5 kHz would be more than enough to reproduce any profiled/modelled Cab. That would bring me back to my original question in the topic title.

I am interested in knowing the point of view of @Gitarrenschlumpf about this topic. if we are not playing tracks or any other instruments, would not a GFR Cab be enough and FRFR overkill? (Strictly speaking about guitar).

My point of view: If you play electric guitar without sparkling sounds (earlier clean Lukather, earlier Marillion, some Oldfield... everything above 10 kHz), it´s enough to have a GFR amplification. It sounds more realistic, if there are broadbands inside. But if you want the whole range and acoustic guitar, FRFR is the right way.

Hmm, sorry for being sceptic, but:

If you compare to frequency response of take a V30, and your average RCF PA midlow driver, youll see that the V30 is flat up to 4k, and many PA driver show big irregularities above 2k, and so are specd to go up to 2k. The rest is for the tweeter. Also, compare the whole frequenty range. A V30 doesnt do a whole lot worde than that average PA speaker. Most of the guitar cab sound is made by the cab design (closed or open back instead of ported, and no tweeter), so i guess that a midlow PA driver used in a closed back wont sound that bad, itll just have its own specific tones which it boost or attenuates, and therefore, emulated cab + real cab isnt that different from emulated cab + GRFR. Not in its lows (ported cab..) but especially in its highs!

That is offcourse not true if you would find a 12 inch driver which does up to 10k -3dB, but mind you, laws of physics cannot be changed. PA speaker builders would pay big money to get the Xover point away from 1-2k, because there the harshest of tones + thats where most speech intellegibility is, and its all compromised by passive Xovers. Still most designers stick to 1-2k. Wonder why?

Hmm, sorry for being sceptic, but:

If you compare to frequency response of take a V30, and your average RCF PA midlow driver, youll see that the V30 is flat up to 4k, and many PA driver show big irregularities above 2k, and so are specd to go up to 2k. The rest is for the tweeter. Also, compare the whole frequenty range. A V30 doesnt do a whole lot worde than that average PA speaker. Most of the guitar cab sound is made by the cab design (closed or open back instead of ported, and no tweeter), so i guess that a midlow PA driver used in a closed back wont sound that bad, itll just have its own specific tones which it boost or attenuates, and therefore, emulated cab + real cab isnt that different from emulated cab + GRFR. Not in its lows (ported cab..) but especially in its highs!

That is offcourse not true if you would find a 12 inch driver which does up to 10k -3dB, but mind you, laws of physics cannot be changed. PA speaker builders would pay big money to get the Xover point away from 1-2k, because there the harshest of tones + thats where most speech intellegibility is, and its all compromised by passive Xovers. Still most designers stick to 1-2k. Wonder why?