KVR Audio

SOL Studio · Post by **SOL Studio** » Mon Apr 20, 2026 1:44 pm

Hi everyone,

I’ve been developing a mastering limiter called SOL-4, and I’d really appreciate some feedback from experienced users.

The goal with SOL-4 is simple:

Achieve competitive loudness with fewer artifacts,
and without any hidden behavior.

Key features:

- Perceptual (K-weighting inspired) detection
→ reduces low-end pumping and focuses on what we actually hear

- Spectral-adaptive release
→ keeps low-end stable while maintaining high-frequency density

- Delta monitoring
→ hear exactly what’s being removed

- Safe gain-matching
→ output gain is placed before the final true peak stage

- Zero-latency mode (0.0 ms lookahead)

- Oversampling up to 8x + built-in dither / noise shaping

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I made a short comparison video (same LUFS / same True Peak ceiling):

- Piano (fortissimo): Pro-L2 vs SOL-4
→ listen to the decay and overtones

- Heavy kick track: APEX vs SOL-4
→ focus on low-end stability and pumping

- Full mix maximizer test: Pro-L2 vs SOL-4

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Formats available for beta:
VST3 (Windows)

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What I’d love feedback on:

- Transient handling and punch
- Low-end behavior on bass-heavy material
- Smoothness of the release
- Any bugs or UI/UX feedback

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If you're interested, feel free to comment or send a PM and I’ll share a beta build.

Thanks!

sinkmusic · Post by **sinkmusic** » Mon Apr 20, 2026 4:38 pm

Hello
It looks quite interesting! I'd be glad to give the beta a test drive

SOL Studio · Post by **SOL Studio** » Mon Apr 20, 2026 4:59 pm

Thank you so much！ I've just sent a private message.

pekbro · Post by **pekbro** » Mon Apr 20, 2026 5:24 pm

I'd like to test it, and have a modest core i5 and Iris XE graphics. Typically at the lower limits of cpu requirements these days. Anyway, thanks.

SOL Studio · Post by **SOL Studio** » Tue Apr 21, 2026 12:49 am

Thank you so much!

I’m so sorry—I realized I accidentally sent you the Debug build instead of the Release build earlier!
I have resent the correct file via PM.

SOL Studio · Post by **SOL Studio** » Tue Apr 21, 2026 12:59 am

@pekbro Thanks for your interest!

I've sent you the correct beta build via PM

SOL Studio · Post by **SOL Studio** » Tue Apr 21, 2026 1:08 am

I’m based in Japan, so my replies might be a bit delayed due to time zone differences.
Thanks for your patience

pekbro · Post by **pekbro** » Tue Apr 21, 2026 1:38 am

It's pretty nice and efficient for me so far

SOL Studio · Post by **SOL Studio** » Tue Apr 21, 2026 5:58 am

Thanks a lot, glad to hear that!

If you have time, I’d be really interested in your thoughts on:

-low-end behavior (especially kick/bass)
-release smoothness
-how it compares to your usual limiter

Any impressions are very welcome

pekbro · Post by **pekbro** » Tue Apr 21, 2026 6:20 am

So far, I'm finding it pretty transparent and not quite as weighty sounding as the AL-1, for instance. Low end offers a lot of control, but lacks some weight. Of course, I have much exploring to do yet though. The refinement section is very cool, again a lot of control and silky smoothness.

Anyway, it's impressive imo, I like it quite a lot

Even at 8x oversampling, it's performing very well for me on my modest rig.

I will keep at it.

SOL Studio · Post by **SOL Studio** » Tue Apr 21, 2026 6:47 am

Thanks a lot for the detailed feedback — really appreciate it!

That’s a very interesting point about the low-end weight, and it’s something I’ve been thinking about as well. The current design is quite focused on keeping the low end clean and controlled, so in some cases it might feel a bit lighter compared to more aggressive limiters.

If you have time to experiment a bit more, you might be able to bring some of that weight back using the refinement section — especially the low-band release multiplier.

Really glad to hear that section is working well for you and feeling smooth!

Would love to hear how it feels after a bit more tweaking. Thanks again, this is super helpful!

blockie710 · Post by **blockie710** » Tue Apr 21, 2026 7:41 pm

Would love to test it out.

pekbro · Post by **pekbro** » Wed Apr 22, 2026 1:04 am

I think it would be cool if you could set the theme to a custom color somehow. These are both very nice though.

Interestingly, I was able to really bring up the low end weight with only parallel techniques.
I only did that to see what it would sound like, it worked (seemingly)...

SOL Studio · Post by **SOL Studio** » Wed Apr 22, 2026 1:49 am

@blockie710 Thank you so much. I've just sent a PM with the beta build.

SOL Studio · Post by **SOL Studio** » Wed Apr 22, 2026 2:10 am

@pekbro Thanks a lot, really appreciate that!

Custom color themes are an interesting idea — I’ll keep that in mind for future updates.

Also very interesting to hear about the parallel approach — that’s actually a great insight. It suggests the weight is there, but depends on how the processing is blended.

I might explore ways to make that kind of result easier to achieve directly.

Thanks again, really helpful feedback

[Beta] SOL-4 – Transparent Limiter with No Hidden Behavior