What's the deal with IR?

[dbsfgyd1]

Just remember that an IR is meant to replicate recording a mic'ed cab, it's not meant to sound like the cab itself so you shouldn't directly compare the sound in the room.

good point.

 

[BassmanNate]

I’ve tried IRs on a bass signal chain. If recording you can hear the differences soloed although they’re fairly subtle once they’re in a mix. (Or at least to my ears they are.) I’ve tried using them live and I didn’t hear anything I couldn’t already get with an HPF and LPF, a parametric EQ, or a really good preamp.

Truth is, I’m in the “just sounds good” camp and prefer to take a minimalist approach most times. I think with bass it’s more important to find a good sound you know inside out and can work with for pretty much everything rather than be constantly switching between minute tonal differences, most of which won’t be that audible most times, assuming they are at all.

With higher range instruments different IRs are far more noticeable and probably something worth exploring in depth if you also play guitar. But for bass, my experience (so far) has been that they’re not that big a deal. But that might be just me.

However, if you do want to get into IRs I’d suggest what others have already suggested and start with something inexpensive like the Sonicake or (my personal preference) the Mooer Radar. Neither are without limitations and minor bugs. But they’re not priced like a Kemper or Cortex are. And they do work surprisingly well…um…for guitar

Here’s a couple of good reviews to help you decide. Find the Sonicake review here, and the Mooer Radar one here.

Happy modeling.

Oh, I hadn't thought of running a hpf and lpf at the end of the signal chain to clean it up. I run them at the beginning to clean the signal before compression but now I'm going to have to try at the end, too! Never really thought about the fact that that's the bulk of what a cab sim is doing.

 

[jimfist]

Cabinet simulation IRs can be a wonderful thing...depending on what you want. They can be a problem solver for FOH issues and IEM/Full-range monitoring of DI bass. They can also allow you to change the sonic flavor of your tone in ways that are would be difficult to exactly replicate using EQs & filters.

Like amp modeling, cabinet sim IRs tend to be a little bit on the techno-geek side of things, so if you're not that kind of player, IRs might be a challenge IF you don't find something right off the bat that floats your boat. And the variety and quality of cab sim IRs is all over the map.

Personally, I like getting tones both with IRs and with EQ/Hi & Lo Pass filtering, depending on they type of sound I'm looking for. For players who use full-range stage monitors & IEM, cab sims can work great. If you're using a traditional bass rig on stage, the cab sim IRs are more helpful downstream at the mixing desk when dealing with a full-range DI signal that could use some taming (overdriven/fuzz tones) or character.

It's fun! Or maddening! It's great! It sucks!
Good luck.

 

[darwin-bass]

I believe IR (impulse response) refers to a digital filter, either finite impulse response (FIR) or infinite impulse response (IIR), that can be used to model or simulate some part of a signal chain.

I think it has become a thing because the digital filter is much easier to implement than the equivalent analog filter and has opened doors to modeling things that would have been all-but impossible with only analog circuitry.

At least that is the impression I get from my rather weak understanding of it all. I might be off base.

 

[FullumMusic]

I guess it would be hard to tell exactly how "impressive" (or, accurate might be a better word) a cab IR is, unless compare your bass clean vs through that IR vs through that actual cabinet.

On a really basic level, an Impulse Response is just a recording of a sine wave swept from 20Hz to 20,000Hz at a constant level. Using fancy math, that sweep over time is "folded back on itself" so it's no longer a sweep over time but an impulse of all the frequencies at playing instantaneously. Some more math magic is done by comparing the impulse created by your recording vs just a pure sine impulse, and the way your impulse deviates from the pure impulse is the tonal characteristics the thing you're making the impulse response of. (The cab, an amp, an EQ, reverb of a physical room, reverb plugin, hardware reverb, etc. Basically any linear audio system. The output is essentially a convolution of the input.) Those deviations from the pure sine wave can now be applied to any signal to give that signal the tonal character captured in the IR.

(You can also do it with a hand clap or some other "impulse" of noise, but it's less accurate than the sine sweep method.)

You can make your own IRs of your own cabinets using Reaper and their stock ReaVerb plugin, and then do your own A/B comparisons of your own cab. It's been a few years since i've made IRs so definitely find a tutorial online that's got more detail than i remember. You basically:
- have ReaVerb generate a sine wave from 20Hz to 20KHz at least 30 seconds long. The longer the sweep the more accurate the IR. 90 seconds is plenty though.
- Save that sweep. It's your master file. You use it to play through your gear AND you need to load it into ReaVerb when creating the IR as its reference sweep.
- Set up a mic in front of your cabinet.
- Put the sine sweep into a Reaper channel. Set Reaper to record the exact length of the sine sweep. Add a second channel to record to.
- Run that channel out to the power section of your amp (So, into the amp's Return, not input. Skip the pre section of the amp because then you'll be modeling both the amp and the cabinet. Of course, you'll inevitably be modeling the impact the mic and mic placement has on your cab, but that's unavoidable. It's the nature of the beast.)
- Press record and record that sweep!
Sweep Channel -> out interface -> into Amp return -> cabinet -> mic -> input channel -> recording.

- Export the audio of the recorded sweep (not the generated sweep.)
- Open up ReaVerb. Load the reference sweep and the recorded sweep. Click process. Save your IR.

Now you can record your bass direct. Duplicate the track. Have one of those tracks running through the IR, and the other running out of your interface into the Return of your amp. Get the volumes the same and see how they compare. Does it sound accurate? Does it change the tone much at all?

And once you see how easy it is to make IRs, you may or may not go IR crazy. I was in Sevilla and went to Real Alcazar really early. We were in the first group of people let in. My wife and i quickly walked away from the few other people there and found ourselves in some amazing empty rooms. We took turns: i'd take a pic of her with her phone, then she'd take a recording of me clapping for an IR. Got a few amazing reverb IRs of actual rooms in Alcazar.

I rented out the main concert space in the Tolbooth in Stirling Scotland. Put a Genelec on stage and had mics set up a few different places in the room. Now i have reverbs of that space.

Got great IRs of awesome sounding studio rooms, stairwells, mic on one end of ductwork and the speaker at the other end several rooms away.

You can even make IRs of your entire rig (amp + cab) with different settings and play around with going ampless with your own amp, and the ability to change IRs depending on the settings you want. IR your friends' amps & cabs. omg now i wanna make IRs again.

 

[J Wilson]

Geez I'm old.

I thought managing impulse response was keeping my eyes straight ahead and going home to my wife . . . .

 

[BassmanNate]

Thanks for the responses. I know WHAT an impulse response is and how they're made. I was just trying to figure out whether running virtual bass cabs as impulse responses was just hype. Sounds like I just need to get an inexpensive one and play with it to see if it's for me at all.

 

[DonaldR]

I've read somewhere that some cheap IR loader pedals are clipping with a bass signal. They are usually targeted at guitar players.

 

[FullumMusic]

Thanks for the responses. I know WHAT an impulse response is and how they're made. I was just trying to figure out whether running virtual bass cabs as impulse responses was just hype. Sounds like I just need to get an inexpensive one and play with it to see if it's for me at all.

Hehe, i guess what i said was a long winded way of saying just that: You can make your own IR for free of your own cab, or your amp + cab, and compare and hear first hand exactly how much the IR sounds like your rig, and how different it sounds from the direct signal of just your bass.

 

[BigBassBob]

I've been using the cab sim on my Darkglass X Ultra for years loaded with Nolly's Megameld (8x10 and guitar 4x12) and have been really happy with it. With the on-board EQ I haven't found any gigs it couldn't cover.

Currently using my main rig as a stage monitor for the more punky stuff I've been gigging lately with the majority of my tone going from my pedalboard to FOH. My live sound (especially when using a pick) has never been better.

IRs have a time and place. I like to have a bit of backline so I can FEEL some of the low end. I'll never stop using amps but the two guitarists in one of my current bands both use the Headrush floor unit and are running straight DIs using IRs. Their sound is on-point and quick to dial into a room without any of the sound engineering nightmares when mixing a high-gain band but I've deviated a lot.

TR;DR - I like IRs.

 

[jimfist]

Thanks for the responses. I know WHAT an impulse response is and how they're made. I was just trying to figure out whether running virtual bass cabs as impulse responses was just hype. Sounds like I just need to get an inexpensive one and play with it to see if it's for me at all.

[apologies for the length...]
It is implicit that listening to cabinet IRs is done using full-range (and flat response) speakers, whether they be studio monitors, headphones, or sound reinforcement speakers.

As you know, the cabinet IR is acting as a replacement for a mic'd speaker cabinet, and should in theory sound no different vs. that same mic/mic distance/cabinet/mic preamp would when listening in a studio via reference monitors (with the actual cabinet in isolation, not heard).

Question: what speaker system/sound reinforcement would you be specifically using when auditioning an IR player device?

One bugaboo with using cabinet IRs is that they are a single, static, tone snapshot devoid of any dynamics or changes in response that you'd normally find with a traditional amp/cabinet physical interaction: stuff like impedance variations changing tone, speaker compression, amp sag (tube amps), input gain dynamics (clean to overdriven based on input level/playing hardness), etc.

The better IR players also include models of these interactions, which helps make the IR usage experience (the "feel") more palatable when listening through otherwise very flat and sterile sounding (by design) full-range playback systems. Not all IR devices are the same in this respect, so keep that in mind if you're using a low-end IR player that doesn't account for the other aspects listed above. All this less relevant if you prefer ultra-clean or undistorted tones and solid state power amps.

This is why many guitarists prefer to use their real amps running into a (reactive) load box to retain the organic "feel" of the amp, and then using the IR only as a mic'd speaker replacement.

 

[BassmanNate]

[apologies for the length...]
It is implicit that listening to cabinet IRs is done using full-range (and flat response) speakers, whether they be studio monitors, headphones, or sound reinforcement speakers.

As you know, the cabinet IR is acting as a replacement for a mic'd speaker cabinet, and should in theory sound no different vs. that same mic/mic distance/cabinet/mic preamp would when listening in a studio via reference monitors (with the actual cabinet in isolation, not heard).

Question: what speaker system/sound reinforcement would you be specifically using when auditioning an IR player device?

One bugaboo with using cabinet IRs is that they are a single, static, tone snapshot devoid of any dynamics or changes in response that you'd normally find with a traditional amp/cabinet physical interaction: stuff like impedance variations changing tone, speaker compression, amp sag (tube amps), input gain dynamics (clean to overdriven based on input level/playing hardness), etc.

The better IR players also include models of these interactions, which helps make the IR usage experience (the "feel") more palatable when listening through otherwise very flat and sterile sounding (by design) full-range playback systems. Not all IR devices are the same in this respect, so keep that in mind if you're using a low-end IR player that doesn't account for the other aspects listed above. All this less relevant if you prefer ultra-clean or undistorted tones and solid state power amps.

This is why many guitarists prefer to use their real amps running into a (reactive) load box to retain the organic "feel" of the amp, and then using the IR only as a mic'd speaker replacement.

I use a set of Sennheiser HD 280 pro cans at home most of the time. Out and about, it's iem.

First time I encountered speaker cab sim, I was a kid and couldn't fathom why on earth you would need such a thing outside of recording. Now, I sit here 20 years later and almost always have some kind of headphones. Lol!

 

[jbybj]

I tried a few Cabinet IR's when I first became aware of them. After a fair amount of experimentation, I realized I pretty much despise them. It took me a while to understand why, but here's my thoughts, (all anecdotal opinion based, no science experiments).
It seems like from the start of amplifying an electric bass, the goal has always been to present the loudest, cleanest, most accurate representation of the source. Unfortunately, technology was not up to the task. So all the early efforts in bass amplification involved compromise, employing tricks and innovations to make the bass as loud and clear as possible. But something was always sacrificed, sure, this cabinet gets loud, but it doesn't reproduce much below 80Hz, or this one gets low but it craps out early. Whatever the sacrifice, early cabinets were less than true to the source.

But that's all there was, and they were employed in making awesome music, so as a collective, lovers of Rock and Roll came to love these sounds. These diminished, less than ideal tones were the sounds of our favorite music.

Flash forward to the 21st century, and we now have the ability to, for relatively low cost, reproduce the loudest, cleanest, most high fidelity live electric bass in history. Hallelujah! No more having to settle for a crappy sounding bass just to be heard. So, lets take a glorious, full frequency, low distortion, big whompus bass, and throw a poopea old blanket over it. And while we are at it, lets go back to blood letting at the dentist for our medical care.

I know, there are many times I will employ a filter or distortion to present a less than pure bass sound, and I love that. Still it feels different than choosing to globally diminish my tone by trying to emulate old science. A good bass through a full range system, is a thing of beauty. Cab sims? no thanks.

 

[jimfist]

A good bass through a full range system, is a thing of beauty. Cab sims? no thanks.

So, what would your advice be to bassists who are currently using cab IRs and prefer them over pure DI? Asking for a friend.

 

[jbybj]

So, what would your advice be to bassists who are currently using cab IRs and prefer them over pure DI? Asking for a friend.

I think people should follow their bliss, simulate your favorite cabinet to your hearts content. I was just responding to the OP. If they are on the fence, maybe my opinion will provide some perspective.

 

[kyral210]

It won't be any better than actually changing bass cabs.
I've never found changing from one cab to another to make a spectacular difference but YMMV.

I don’t know about changing speaker cabs, but changing impulse responses (which are indistinguishable from a real cab being recorded) makes a huge difference. Maybe it’s the microphone part of the equation, but IRs change everything!

I tend to blend mine in so I get the best of both worlds, the ‘dry’ preamp and the ‘wet’ speaker.

 

[kyral210]

I tried a few Cabinet IR's when I first became aware of them. After a fair amount of experimentation, I realized I pretty much despise them. It took me a while to understand why, but here's my thoughts, (all anecdotal opinion based, no science experiments).
It seems like from the start of amplifying an electric bass, the goal has always been to present the loudest, cleanest, most accurate representation of the source. Unfortunately, technology was not up to the task. So all the early efforts in bass amplification involved compromise, employing tricks and innovations to make the bass as loud and clear as possible. But something was always sacrificed, sure, this cabinet gets loud, but it doesn't reproduce much below 80Hz, or this one gets low but it craps out early. Whatever the sacrifice, early cabinets were less than true to the source.

But that's all there was, and they were employed in making awesome music, so as a collective, lovers of Rock and Roll came to love these sounds. These diminished, less than ideal tones were the sounds of our favorite music.

Flash forward to the 21st century, and we now have the ability to, for relatively low cost, reproduce the loudest, cleanest, most high fidelity live electric bass in history. Hallelujah! No more having to settle for a crappy sounding bass just to be heard. So, lets take a glorious, full frequency, low distortion, big whompus bass, and throw a poopea old blanket over it. And while we are at it, lets go back to blood letting at the dentist for our medical care.

I know, there are many times I will employ a filter or distortion to present a less than pure bass sound, and I love that. Still it feels different than choosing to globally diminish my tone by trying to emulate old science. A good bass through a full range system, is a thing of beauty. Cab sims? no thanks.

Because IRs sound so different to real amps:

 

[gillento]

I tried both analog cab sims or LPF filters and digital IRs on bass.
My "beef" with digital IRs is that they create phase/latency issues once you try to an analog blend with a clean signal.

Further, to my ears a miked cab or a IR does sound softer that an analog DI signal. So this (analog DI) is easier to fit (cut better) in a mix to my ears.

analog LPF and HPF (Broughton RFE or L&HPF, Empress Para EQ Mk2 Deluxe or tech21 Q/strip....) at the end of the chain works best for me

 

[jimfist]

I tried both analog cab sims or LPF filters and digital IRs on bass.
My "beef" with digital IRs is that they create phase/latency issues once you try to an analog blend with a clean signal.

Further, to my ears a miked cab or a IR does sound softer that an analog DI signal. So this (analog DI) is easier to fit (cut better) in a mix to my ears.

analog LPF and HPF (Broughton RFE or L&HPF, Empress Para EQ Mk2 Deluxe or tech21 Q/strip....) at the end of the chain works best for me

Agreed, and good points. Digital latency is a fact of life with IRs, and yes, parallel blending with an analog signal is a problem. This is where analog cab sims have an advantage over digital IR, and there are still plenty of good choices available (SansAmp of course, DSM & Humboldt, A.D.A., Palmer, Hughes & Kettner). The other solution is to commit to a digital modeler that allows you to blend the IR with the parallel path, all within the digital domain to avoid latency phase issues. Not for everyone, though fairly popular (see Line6 HX Stomp).

The double-edged sword of digital IRs, in terms of tone, is that a typical near-field IR will capture the very complex interactions of the sound that can sound "phasey" and less in-your-face than a less complex analog filter. The remedy to this is far-field IR captures, and ideally in an environment without any room reflection (good luck with that). We listen to speakers in the far field vs. near-field with one ear only an inch or so away from the speaker. That I'm aware of, the only products capable of addressing this issue are Fractal Audio, AxeFxIII "smoothing" and AxeFxII "De-phase" features. This essentially smooths out the IR, removing the phase issues, but also removing some of the IR's unique character in the process. But this can be a very good thing as it simulates what that IR might sound like in the far field.

I think that some day this will all get figured out in a less messy fashion as technology improves. 15 years ago, bass cabinet IRs weren't on many people's radar, and were just becoming a consideration for guitarists. Bass Cab IR tech isn't the be-all-end-all, but it is a cool tool to have. I actually run a synth tone into a cello IR and it's a remarkable emulation.

 

[GTHintz]

So, a little background. When I first heard about impulse response 10ish years ago, it was mostly for things like reverb. You could model a particular space using an IR. Could see that it was going to be a big thing in that space.

Fast forward to the last couple of months and I've started looking at analog/discrete digital individual pedals and see that now it's mostly being pushed for speaker cab simulation. I can see for guitars where a particular cab is going to interact with the amplifier it's plugged into. But for bass? Does it really have that much impact on your tone?

This isn't me mocking anyone. I legitimately want to understand. All of the cab sims I've messed with on bass haven't been IR to my knowledge and I've felt mostly meh about it. Even stuff that's supposed to model a particular cab hasn't been impressive. Is IR that much better?

I'm not a huge fan of cab sims and all the ir stuff. It could be useful for someone if you're really trying to get a specific vibe from a speaker or your di sound. Honestly it just takes your eq and skews it or ads a lever of compression. I've always found the best tones without the sims and just using eq or blending preamps together in a signal chain if I want something in there. But if you don't have the room for preamps and you want it all from 1 pedal or rack mount then the amp sims are nice to have. But I also feel like I'd prefer having the analog controls at my fingertips as opposed to everything kinda preset like sims are.