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 SplineEQ by Photosounder is a Virtual Effect Audio Plugin. It functions as a VST Plugin and an Audio Units Plugin.
SplineEQ SplineEQ
Product SplineEQ
Developer Photosounder
Price (MSRP) Free / $29
Type / Tags
Plug-in, App & Soundware Format(s)
Operating System Availability
Download Released
 1.2  Downloads Released
System Requirements
A VST 2.x-compatible host
 1.2  Downloads Released
System Requirements
Mac OS 10.5+, an AudioUnit or VST 2.x-compatible host
Miscellaneous Information
Copy ProtectionCustomized Per Customer

SplineEQ is a linear phase equalizer plugin. Designed to be simple and flexible, SplineEQ allows you to create filters using Bézier splines, the best known way to design curves.


Linear phase equalizer. Offers a better sound quality than the more common minimum phase equalizers by not affecting the phase of sound, only the intensity of frequencies, which makes it easier to achieve good sounding results. Also has the advantage of not incurring aliasing artifacts.

Spline-based filter design. Filters are simply created by designing a spline curve which can be made to adopt any imaginable shape. No filter types to choose from, all points simply define part of the shape of the filter's spline curve. The actual filter's frequency profile is displayed as a dashed curve when it differs from the ideal spline curve (this can be changed by changing the filter's resolution).

Up to 60 bands (only up to 4 in the free version of SplineEQ) or as low as 1. You can create or disable bands by double clicking on the visualisation area of the interface and adjust them either in that area or using the knobs or even the automatable parameter sliders in the host's interface.

Simple curve modification functions. You can modify the curve as a whole using the transpose function to shift the curve up and down by up to 10 octaves, affect the overall gain to shift all gain settings up or down evenly or even change the gain scale to apply a ratio to all gains, thus enabling you to either flatten, exaggerate or reverse the shape of a curve.

Frequency analyser. More intuitive than your usual logarithmic curve frequency display, this frequency analyser shows you the intensity of frequencies before and after the filtering with colours. It's also fine tuned so that intensities at different frequencies are represented in a way that matches closely to our perception. It moves in a fluid manner in sync with the source sound and has a frequency resolution of about 10 Hz.

Smooth and fluid graphics. The whole interface responds fluidly to change, even the frequency visualisation has a great frame rate and all the graphics are perfectly anti-aliased.

-Infinite dB to +60 dB gain range. This allows you to completely silence entire ranges of the spectrum or to really bring back some fainter harmonics by boosting their amplitude thousandfold. Gains are represented logarithmically between -60 dB and +60 dB and linearly below -60 dB. Given the uniquely immense gain range there's also a built-in limiter whose knob lights up when over the adjustable threshold.

Smooth transitions. Changing parameters, either by adjusting the knobs, the graph or by parameter automation is always done smoothly and creates no audio artifacts.

Adjustable resolution, latency and CPU usage. The resolution of the filter can be lowered or increased (up to roughly 22 Hz) and the processing latency can be changed to obtain a lower CPU usage or a lower latency.

Good performance. Linear phase equalizers always require more power than other types of equalizers. However SplineEQ is as fast or faster than other linear phase equlizers, often with less latency.

Presets are available here and can be saved or open (not with the free version of SplineEQ). Their format is compatible across all platforms and hosts and can be edited with a text editor.

Also supports all sampling rates (384 kHz included), is available on both Windows and Mac (Intel and PowerPC), in VST (2.4) and AU format, in 32 and 64-bits. All input, output and processing are done in 64-bit floating point format and in stereo.

User Rated

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Discussion: Active


4 March 2012 at 9:09amariston

@myk: I haven't used SplineEQ, but as I understand it, EVERY linear phase EQ introduces latency because of the way linear phase adjustments are computed (the signal must be delayed a bit, kind of obvious if you think about it). That's why they're typically used for mastering and final mixing, as opposed to tracking. Seems kind of unfair (if not dead wrong?) to mark it down for something that's inherent to its way of working.

5 March 2012 at 9:23amSyrou

@myk Just locate the latency knob and adjust it for lower latency, you should be just fine.

The reason why you want to be able to change latency, is for rendering purposes. If you are really anal about getting the best possible sound, you should increase the lantency when you render, and that will give you an even sharper sound. As you might have noticed with the "dotted real processing" line that shows up on the lower frenquencies,

it will become more accurate with higher lantecy settings, this is something you can't escape when processing audio the way linearphase eq's does it.

It's not fixable, it's just something you have to learn, with ALL linearphase eq's :)

5 May 2012 at 5:19amjam92189

just a little thing to say I tried this out on a audio cleaning project i had and it kept the tone of the voice but got rid of the noise I mean whistling right next to the vocal frequency. no other eq i had was doing it right and this baby kicked ass.

7 May 2012 at 5:43amjackmazzotti

i use this for sound design and it is awesome

7 May 2012 at 6:03amjam92189

yea its a great plugin i love it

7 May 2012 at 6:17pmEndor-8o8

Really nice free EQ, very tweakable, efficient and colorless. Perfect for cleaning, mixing and mastering.

7 May 2012 at 9:05pmjam92189

I agree. the paid version is even better to. I use this for cleaning and mastering

3 July 2012 at 7:23amKrakatau

Yep, i discovered what the free is by itself capable of on a sample design purpose and after that i'll certainly by the full version ASAP ...really excellent tool !

3 July 2012 at 8:24amjam92189

You know what is awesome is if you set it to minimal delay and stuff right to find something like if there is this annoying hum then you cut the hell out of it swap back to max mode and render you will be amazed on how high the quality of the eq its like you never did anything but the hum is gone. its very non destructive

3 July 2012 at 9:36amKrakatau

well i currently experience narrow bandpass (rather than bandstop) to isolate locust's stridulation at almost a precise frequency then rendering, not much different technique as you know, that what made me amaze about spline eq

3 July 2012 at 6:56pmjam92189

I know some people complain because its super latency ridden but that's what i think makes it so good the quality of the eq is so high that it has to be

12 November 2012 at 6:58pmBrother Charles


Great review. I like how you brought out more information about the unique graphically-driven features.

12 October 2013 at 4:53pmxtrax

Brilliant mastering EQ. Top quality.

28 June 2014 at 1:52pmoclock

TOP notch EQ plugin right here..

Best delivered in final mixing master bus and mastering.

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Average user rating of 9.50 from 12 reviews

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