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Hello, has anyone here gained any expertise in creating an impulse response file, particularly for an antique phonograph or radio equipped with a horn? I'm interested in emulating that distinctive sound.

You might be able to find a good premade one here: https://fokkie.home.xs4all.nl/IR.htm

I also sometimes use izotope Vinyl + CS12 (free VST plugins) to get that sound.

HectorBates wrote:
... phonograph or radio equipped with a horn? ...

AudioThing's "speakers" has "PA Horn" & "megaphone" presets which are close if you increase its "PITCH" control, and cut the bass with its in-built EQ. https://www.audiothing.net/effects/speakers/ (demo version is free)

Sharing my little wisdom for making "Impulse Responses" here.

First what is a IR ? It's a recording of the "response" of something such as a room and its reverb, or a speaker and its tone. You give it an impulse, and see how it responds.

Little caveat is all this doesn't recreate dynamic effects such as compression and distortion, only "EQ" / reverb / echo etc...

There are three types of IRs, a recorded burst and response, a "sine sweeps", and a "resonant" one.

1) A burst - A burst IR would be a fast transient from a clap, balloon pop, clapperboard, burst of noise, fire-cracker etc.... and record what happens after that. This is good to record an echo/reverb.

2) A sine-sweep - It requires extra work. As you need a speaker to playback an audio file, and then you "deconvolve" the recorded audio with a software which compares the recorded audio with the original audio and "extracts" the difference to give you the tone of what you recorded. This could be to record a room but also a combination of speaker and microphones which will affect the tone of the played audio and how it's recorded. Thus is useful for amp and mic simulation, or to record an EQ.

3) Resonance - I'm not familiar at all with this one. In short you vibrate an object or thing and record how it resonates. I'm not sure if this is exactly for a echo/reverb type thing or just a tone. It's not very frequent id say. Maybe it's very similar to the deconvolution technique just with a fixed frequency.

Now my tips :
- SNR Signal to Noise Ratio is king. The louder your impulse is, the quieter the environmental noise will be in contrast; making clearer echo/reverb.
- Balloons are loud at around 140db, they imo are perfect SNR but beware the explosion might produce wind noise and clip the mic. If your mic is in the same position as your balloon, I recommend to pop it near the floor and have your mic up at head level to avoid saturating your mic. Or have a wind jammer.
- 32 bit recording will help greatly!

- This software https://www.voxengo.com/product/deconvolver/ by Voxengo will generate sine-sweeps and deconvolve.
- Note for deconvolution, your recorded audio needs to be longer than the reference file, any extra time will be the length of your de-convolved IR! If they're the same, you'll have a 0.0s result! So give it an extra 5s. (Still trim it behind and apply a fade out in your DAW such as Audacity)
- Typically people use a Omni pickup pattern mic. Although you're free to use others.
- Don't sweat it for your mic / speaker. I put a tiny BT speaker in the fridge/oven etc... And I like the results for reverb!
- You'd be surprised by how good a 4s sine-sweep can sound. IMO record a short and long one.
- For Sinesweep IRs : Record a reference music and vocal track. It will be nice to compare music/voice playing the convolution reverb, with the actual music/voice playing from the speaker and having the IRL reverb. Checking if your result is close to reality.
- Have a few start/end reference clicks in your sinesweep file to line up your source material with your recordings. You will struggle to find the start/end of only a sinesweep!

- I created a sine-sweep kit https://freesound.org/people/Sadiquecat/sounds/845304/

Here are some quality videos :
What is an IR? https://youtu.be/d-1Zn1LvhB4?si=50cixIgWktqIvAra "Impulse Response | Audio Laboratory | Captain Pikant | Thomann" by Captain Pikant
Professionally recording sinesweeps https://youtu.be/aJ6A9fAAAHY?si=FV8rrkp0o-IehPl8 "recording a concert hall with two mics" by audioease
The 3rd type of IR thing https://youtu.be/7TnP2av1smo?si=r7l5fvmbUt45A3-l "
The Beautiful Tones of Gigantic Sewer Pipes" By Benn Jordan

More of a entertainment series https://youtu.be/rF_6E5gpCXY?si=XZ6j62m4p4FxIoCI
By Benn Jordan and https://www.youtube.com/watch?v=xneFdYRV_gM by Venus Theory
They go in a cave to get IRs. Good watch!