Initial Thoughts On Celestion Impulse Responses

This is a long read. The whole point of the HomeToneBlog is to go in-depth on getting great guitar at home, and understanding the choices available to us. The backstory is a big part of that process 🙂

I’ve been a very happy Redwirez Big Box user for years now. The sheer amount of cabs, microphones and placement options have allowed me to gradually figure out how everything that comes after the guitar amp affects my tone.

So why am I looking at Celestion’s impulse responses? Well, it’s all thanks to the Kemper …

The Need For Speakers

I’m currently running a dual-amp setup as my pedal platform. I’ve got a pair of Synergy SYN-1 enclosures running into the SYN-5050. I went with a Synergy setup partly for how compact it is … but also because the preamps are interchangeable modules.

Right now, I’ve got 4 different Synergy preamp modules: the Morgan AC, the Metropoulos Metro Plex, Synergy’s 800 and their T-DLX. The Morgan AC and the 800 module both pair well with the T-DLX for pedals. And the Metro Plex is just very special, and worth the price of admission on its own.

As with any amp, these modules need pairing with a suitable speaker to get the best out of them. I could just stick to using impulse responses. IRs are more than good enough for both playing and recording, and they have some serious advantages for home use.

But by getting real speakers – and cabs to put them in – I can mic them up and create my own Kemper profiles. I’ve already made a few, and for me they’re the key to getting what I want from the Kemper.

Choosing Speakers

When it comes to speakers, there’s a lot of choice out there. It’s also quite difficult to figure out how a speaker is going to sound with my amps. How do you describe a speaker tone using words? And how do you account for how a cabinet will influence the sound too?

So I’m playing it safe, and looking at classic speakers that are commonly used with these type of amps.

For the Morgan AC, the advice I was given was unequivocal: a Celestion Blue is the right speaker for that kind of circuit. I’ve also heard good things about the Celestion Gold, so that’s also on the list.

I’ve already got a G12M-65 and a V30. They’ll cover the Metro Plex and 800 modules just fine. I’m not really a big V30 fan, so I’m quite happy to stick that in storage and free up the cab for another speaker. On the forums I hang out on, the Celestion Cream has been getting a lot of love this year. I definitely need to take a close look at it.

That just leaves the T-DLX module. For pedals, I’m running in on the red channel, which is believed to be a Blackface-style circuit. Real Fender Deluxe Reverbs often use Jensen C12K speakers. However, the recent Hot Rod Deluxe MK 4 amps have started using Celestion A-Type speakers, and I’m really enjoying just how good that whole package sounds on the Andertons videos at the moment.

Whatever I choose, I’ll be getting 16 ohm versions of each speaker, and putting them into Victory V112 cabs. I’ve gone with 1×12 cabs because of how convenient they are, and I’ve gone with these particular 1×12 cabs because I’m very happy with the ones I’ve already got. 1×12 cabs are perfect for the kind of tones I’m after.

The nice thing about this whole process is that I can spread the costs out. I can pick up 1×12 cabs 2nd hand when they come up for the right price, and then buy a replacement speaker for it when funds allow. I’m not in any hurry, and the savings from doing it this way will basically pay for one of the cabs and its new speaker too.

I just need to figure out which speakers I want first.

Using IRs To Audition Speakers

Speakers vary quite a bit in price. They’re also physically bulky and heavy enough to be awkward to post if I don’t like them and want to sell them on again. Whatever I buy, I’d really like it to stick, so to speak.

That got me thinking. I’m largely looking at speakers from Celestion. Celestion have started selling impulse responses of their speakers, and those IRs have had favourable reviews. (I believe Brian Wampler uses them for his company’s YouTube demos.) And, to cap it all, Celestion have just launched a couple of bundles – any 3 IRs for a big discount, and any 5 IRs for another big discount.

It’s not going to be a perfect audition. We’re not told what cabs were used by Celestion, but there’s almost certainly going to be a difference. And IRs are a cab-speaker-mic combination. They capture what the mic hears, not what you and I hear. Oh, and I use the Sennheiser e906, which Celestion doesn’t use. So there’s that too.

It’s better than nothing, and – at less than 30 pounds for 5 IRs – it’s a lot cheaper and more convenient than taking a punt on the speakers themselves.

I ordered 1×12 open-cab IRs of the A-Type, Blue, Cream, and Gold to experiment with. I also ordered a 1×12 open-cab G12M-65 to act as a reference tone.  I bought them from the Celestion Plus website.

What Do We Get

After checkout, the first thing I noticed was that there was no download link. I had to wait for the confirmation email to come through to get access to the downloads. That wasn’t a great feeling.

The downloads struck me as a bit weird. Instead of just offering a single ZIP file for each speaker/cab I’d bought, there were also links to download various subsets. I can’t work out the point of going to that trouble. IRs are tiny on disk, and Celestion’s offering is tiny compared to something like the Redwirez Big Box.

My advice: just download the ZIP file that contains everything. That way you’ve got it.

There’s something odd about the ZIP files as well. My Mac couldn’t expand them using Finder. I had to open a terminal and unzip them the old fashioned way, which worked without a hitch. I’d like to see Celestion improve their testing to spot problems like this.

Inside each ZIP file, we get IRs recorded at a number of resolutions from 44.1kHz up, and with durations of 200ms and 500ms. The different resolutions are there to match the audio quality you’re recording at.

The two durations? I’ve no idea, and I haven’t been able to find anything online to help with that. For now, I’m assuming that the 200ms IRs are a lower detail than the 500ms, and that they’re provided for use on machines that don’t have enough CPU to process the 500ms IRs. It’s just a guess.

Celestion have used three classic mics – SM57, R121 and MD421 – plus a TLM107 as a room mic. Each of the main mics have been close mic’d (yay!), and there’s six positions for each mic. These positions have names like ‘bright’, ‘balanced’, and ‘dark’, and they quickly become very natural to work with.

Using The Impulse Responses

I’m using MixIR as my IR plugin in Reaper. It allows me to load and blend IRs in multiple ways. I got it as part of the Redwirez Big Box, and I’m very happy with it.

That ability to blend multiple IRs on a single channel came in very handy.

What I ended up doing was running one of the ‘balanced’ IRs, and blending in a small amount of one of the ‘dark’ IRs to add in a bit more bottom-end. I picked which mic entirely by ear. Sometimes I’d use the same mic for the blended ‘dark’ IR, and sometimes I’d prefer a different one.

It took about an hour to hit on this approach. Once I had it, I found that it worked for me with all the different speaker IRs that I’d bought.

My final track setup was this:

  • track 1: Morgan AC panned 100% left
  • track 2: Morgan AC panned 66% left
  • track 3: room mic IR, panned 90% left
  • track 4: T-DLX panned 100% right
  • track 5: T-DLX panned 66% right
  • track 6: room mic, panned 90% right

Tracks 1-3 use mics from the same speaker. Tracks 4-6 use mics from a different speaker. The room mics are getting a mix of post-FX from the other tracks, plus the result of running those tracks through an Echoplex.

The idea is to build a bigger tone through the effects of audio summing, using the Echolex and room mics to give the sound a bit of life without losing the definition.

And, boy did it work. My pedals have never sounded better.

The Different Speakers

The T-DLX module was the easiest to sort out. I paired it with the A-Type IR and didn’t touch it for the rest of the session.

The A-Type didn’t give me those classic Blackface cleans. It didn’t have the same top-end glassy characteristic. That’s okay. It sounded great with dirt pedals, and I’m sure that I can get more out of this with a bit more time.

The Celestion Blue was a huge step-up in audio quality compared to the equivalent IRs from Redwirez. It exhibited a much wider frequency response. That’s very important with the Morgan AC module, as it is hampered by not having an EL84 power section to shape the tone.

I thought that the Celestion Gold was quite similar to the Blue, only with the highs a little more tamed. I went back and forth between the two, and I found that I preferred the Blue for humbuckers. The Gold – with the way I had the IRs setup – sounded a little dull for humbuckers. One thing I didn’t try at the time: I suspect the Gold may be the better choice for my bright Telecaster.

I did briefly try the Cream with the Morgan AC module. Er … no. That just sounded wrong. I’ll revisit that speaker in another session.

I didn’t try the G12M-65 at all. I wasn’t running any of the Marshall-esque modules, and I was having far too much fun with the Morgan to swap it out.

Great Sound Quality

I ran several of my pedals through the dual amp + Celestion IRs setup, and I was delighted with the results.

I always start with the Uber Bee, as it has become the core of my rhythm tone today. I thought it sounded great with the Redwirez IRs. Through the Celestion IRs, it sounded better still.

From there, I tried a bunch of different stuff. The Fender Pugilist was very happy, especially in serial mode. The Boss BD-2 Blues Driver sounded great. The Lovepedal Amp 11 sounded fantastic, but there again it always does.

The biggest leap though came for my Mad Professor Bluebird Overdrive. Once I had that dialled in, I lost a good hour and a half just jamming along to a backing track made by my friend Dave Page. Lovely thick lead tone that worked perfectly over Dave’s clean Telecaster rhythm work. So happy!

Some pedals didn’t sound so good. That’s to be expected when using an AC-style amp. That’s why I went with a Synergy setup, so that I can switch preamps to suit different pedals.

Conclusions So Far

The Celestion IRs are good. Once I figured out how to approach them, I was able to get better tones than I had from my Redwirez IRs. That was for noodling on a single guitar. I have yet to try them in a mix.

They’ve sold me on buying a Celestion Blue speaker. I am going to revisit the Celestion Gold to see whether it is the better choice with brighter single-coil guitars. I’m not sure that I want both speakers though. We’ll have to see.

I am going to look at whether the A-Type is right for the T-DLX, or whether a C12K would be better for me. I need to stop playing with the dirt pedals, and put some time into those clean tones.

Most of all, I’ve really enjoyed playing through them. Now, if only Celestion did their very own equivalent of the Big Box …

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