diff --git a/CMakeLists.txt b/CMakeLists.txt
index 97004962..8c08af6b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -633,6 +633,12 @@ set(ALC_OBJS
     core/bufferline.h
     core/devformat.cpp
     core/devformat.h
+    core/filters/biquad.h
+    core/filters/biquad.cpp
+    core/filters/nfc.cpp
+    core/filters/nfc.h
+    core/filters/splitter.cpp
+    core/filters/splitter.h
     core/mastering.cpp
     core/mastering.h
 
@@ -674,12 +680,6 @@ set(ALC_OBJS
     alc/effects/pshifter.cpp
     alc/effects/reverb.cpp
     alc/effects/vmorpher.cpp
-    alc/filters/biquad.h
-    alc/filters/biquad.cpp
-    alc/filters/nfc.cpp
-    alc/filters/nfc.h
-    alc/filters/splitter.cpp
-    alc/filters/splitter.h
     alc/fmt_traits.cpp
     alc/fmt_traits.h
     alc/fpu_ctrl.cpp
diff --git a/al/source.cpp b/al/source.cpp
index 1af39da2..5dcd1cca 100644
--- a/al/source.cpp
+++ b/al/source.cpp
@@ -59,10 +59,10 @@
 #include "backends/base.h"
 #include "bformatdec.h"
 #include "buffer.h"
+#include "core/filters/nfc.h"
+#include "core/filters/splitter.h"
 #include "event.h"
 #include "filter.h"
-#include "filters/nfc.h"
-#include "filters/splitter.h"
 #include "inprogext.h"
 #include "logging.h"
 #include "math_defs.h"
diff --git a/alc/alc.cpp b/alc/alc.cpp
index faf6392e..87c0578e 100644
--- a/alc/alc.cpp
+++ b/alc/alc.cpp
@@ -82,10 +82,10 @@
 #include "compat.h"
 #include "core/devformat.h"
 #include "core/mastering.h"
+#include "core/filters/nfc.h"
+#include "core/filters/splitter.h"
 #include "cpu_caps.h"
 #include "effects/base.h"
-#include "filters/nfc.h"
-#include "filters/splitter.h"
 #include "fpu_ctrl.h"
 #include "front_stablizer.h"
 #include "hrtf.h"
diff --git a/alc/alcmain.h b/alc/alcmain.h
index 7949baf2..42808f26 100644
--- a/alc/alcmain.h
+++ b/alc/alcmain.h
@@ -25,7 +25,7 @@
 #include "atomic.h"
 #include "core/bufferline.h"
 #include "core/devformat.h"
-#include "filters/splitter.h"
+#include "core/filters/splitter.h"
 #include "hrtf.h"
 #include "inprogext.h"
 #include "intrusive_ptr.h"
diff --git a/alc/alu.cpp b/alc/alu.cpp
index 18a26a38..c13365ec 100644
--- a/alc/alu.cpp
+++ b/alc/alu.cpp
@@ -61,12 +61,12 @@
 #include "bs2b.h"
 #include "core/bsinc_tables.h"
 #include "core/devformat.h"
+#include "core/filters/biquad.h"
+#include "core/filters/nfc.h"
+#include "core/filters/splitter.h"
 #include "core/mastering.h"
 #include "cpu_caps.h"
 #include "effects/base.h"
-#include "filters/biquad.h"
-#include "filters/nfc.h"
-#include "filters/splitter.h"
 #include "fpu_ctrl.h"
 #include "front_stablizer.h"
 #include "hrtf.h"
diff --git a/alc/bformatdec.cpp b/alc/bformatdec.cpp
index b2a2aec9..6f229947 100644
--- a/alc/bformatdec.cpp
+++ b/alc/bformatdec.cpp
@@ -10,12 +10,10 @@
 #include <iterator>
 #include <numeric>
 
-#include "AL/al.h"
-
 #include "almalloc.h"
 #include "alu.h"
 #include "ambdec.h"
-#include "filters/splitter.h"
+#include "core/filters/splitter.h"
 #include "front_stablizer.h"
 #include "math_defs.h"
 #include "opthelpers.h"
@@ -33,7 +31,7 @@ constexpr std::array<float,MAX_AMBI_ORDER+1> Ambi3DDecoderHFScale3O{{
     5.89792205e-01f, 8.79693856e-01f, 1.00000000e+00f, 1.00000000e+00f
 }};
 
-inline auto GetDecoderHFScales(ALuint order) noexcept -> const std::array<float,MAX_AMBI_ORDER+1>&
+inline auto GetDecoderHFScales(uint order) noexcept -> const std::array<float,MAX_AMBI_ORDER+1>&
 {
     if(order >= 3) return Ambi3DDecoderHFScale3O;
     if(order == 2) return Ambi3DDecoderHFScale2O;
@@ -52,7 +50,7 @@ inline auto GetAmbiScales(AmbDecScale scaletype) noexcept
 
 
 BFormatDec::BFormatDec(const AmbDecConf *conf, const bool allow_2band, const size_t inchans,
-    const ALuint srate, const ALuint (&chanmap)[MAX_OUTPUT_CHANNELS],
+    const uint srate, const uint (&chanmap)[MAX_OUTPUT_CHANNELS],
     std::unique_ptr<FrontStablizer> stablizer)
     : mStablizer{std::move(stablizer)}, mDualBand{allow_2band && (conf->FreqBands == 2)}
     , mChannelDec{inchans}
@@ -269,7 +267,7 @@ void BFormatDec::processStablize(const al::span<FloatBufferLine> OutBuffer,
 }
 
 
-auto BFormatDec::GetHFOrderScales(const ALuint in_order, const ALuint out_order) noexcept
+auto BFormatDec::GetHFOrderScales(const uint in_order, const uint out_order) noexcept
     -> std::array<float,MAX_AMBI_ORDER+1>
 {
     std::array<float,MAX_AMBI_ORDER+1> ret{};
@@ -286,7 +284,7 @@ auto BFormatDec::GetHFOrderScales(const ALuint in_order, const ALuint out_order)
 }
 
 std::unique_ptr<BFormatDec> BFormatDec::Create(const AmbDecConf *conf, const bool allow_2band,
-    const size_t inchans, const ALuint srate, const ALuint (&chanmap)[MAX_OUTPUT_CHANNELS],
+    const size_t inchans, const uint srate, const uint (&chanmap)[MAX_OUTPUT_CHANNELS],
     std::unique_ptr<FrontStablizer> stablizer)
 {
     return std::unique_ptr<BFormatDec>{new(FamCount(inchans))
diff --git a/alc/bformatdec.h b/alc/bformatdec.h
index 280ca2fc..adc69dc3 100644
--- a/alc/bformatdec.h
+++ b/alc/bformatdec.h
@@ -5,14 +5,12 @@
 #include <cstddef>
 #include <memory>
 
-#include "AL/al.h"
-
-#include "alcmain.h"
 #include "almalloc.h"
 #include "alspan.h"
 #include "ambidefs.h"
+#include "core/bufferline.h"
 #include "core/devformat.h"
-#include "filters/splitter.h"
+#include "core/filters/splitter.h"
 
 struct AmbDecConf;
 struct FrontStablizer;
@@ -44,7 +42,7 @@ class BFormatDec {
 
 public:
     BFormatDec(const AmbDecConf *conf, const bool allow_2band, const size_t inchans,
-        const ALuint srate, const ALuint (&chanmap)[MAX_OUTPUT_CHANNELS],
+        const uint srate, const uint (&chanmap)[MAX_OUTPUT_CHANNELS],
         std::unique_ptr<FrontStablizer> stablizer);
     BFormatDec(const size_t inchans, const al::span<const ChannelDec> coeffs,
         const al::span<const ChannelDec> coeffslf, std::unique_ptr<FrontStablizer> stablizer);
@@ -61,11 +59,11 @@ public:
         const size_t SamplesToDo);
 
     /* Retrieves per-order HF scaling factors for "upsampling" ambisonic data. */
-    static std::array<float,MAX_AMBI_ORDER+1> GetHFOrderScales(const ALuint in_order,
-        const ALuint out_order) noexcept;
+    static std::array<float,MAX_AMBI_ORDER+1> GetHFOrderScales(const uint in_order,
+        const uint out_order) noexcept;
 
     static std::unique_ptr<BFormatDec> Create(const AmbDecConf *conf, const bool allow_2band,
-        const size_t inchans, const ALuint srate, const ALuint (&chanmap)[MAX_OUTPUT_CHANNELS],
+        const size_t inchans, const uint srate, const uint (&chanmap)[MAX_OUTPUT_CHANNELS],
         std::unique_ptr<FrontStablizer> stablizer);
     static std::unique_ptr<BFormatDec> Create(const size_t inchans,
         const al::span<const ChannelDec> coeffs, const al::span<const ChannelDec> coeffslf,
diff --git a/alc/effects/autowah.cpp b/alc/effects/autowah.cpp
index 5ac51e32..f2ffab44 100644
--- a/alc/effects/autowah.cpp
+++ b/alc/effects/autowah.cpp
@@ -29,7 +29,7 @@
 #include "alcmain.h"
 #include "alcontext.h"
 #include "alu.h"
-#include "filters/biquad.h"
+#include "core/filters/biquad.h"
 #include "vecmat.h"
 
 namespace {
diff --git a/alc/effects/convolution.cpp b/alc/effects/convolution.cpp
index e191e7bc..2442f97e 100644
--- a/alc/effects/convolution.cpp
+++ b/alc/effects/convolution.cpp
@@ -8,7 +8,6 @@
 #include "AL/al.h"
 #include "AL/alc.h"
 
-#include "al/auxeffectslot.h"
 #include "alcmain.h"
 #include "alcomplex.h"
 #include "alcontext.h"
@@ -17,8 +16,9 @@
 #include "ambidefs.h"
 #include "bformatdec.h"
 #include "buffer_storage.h"
+#include "core/filters/splitter.h"
 #include "effects/base.h"
-#include "filters/splitter.h"
+#include "effectslot.h"
 #include "fmt_traits.h"
 #include "logging.h"
 #include "polyphase_resampler.h"
diff --git a/alc/effects/distortion.cpp b/alc/effects/distortion.cpp
index 757244c5..65f8977b 100644
--- a/alc/effects/distortion.cpp
+++ b/alc/effects/distortion.cpp
@@ -24,11 +24,10 @@
 #include <cmath>
 #include <cstdlib>
 
-#include "al/auxeffectslot.h"
 #include "alcmain.h"
 #include "alcontext.h"
-#include "alu.h"
-#include "filters/biquad.h"
+#include "core/filters/biquad.h"
+#include "effectslot.h"
 
 
 namespace {
diff --git a/alc/effects/echo.cpp b/alc/effects/echo.cpp
index a50d3c61..c030ac5b 100644
--- a/alc/effects/echo.cpp
+++ b/alc/effects/echo.cpp
@@ -25,17 +25,19 @@
 
 #include <algorithm>
 
-#include "al/auxeffectslot.h"
-#include "al/filter.h"
+#include "AL/efx.h"
+
 #include "alcmain.h"
 #include "alcontext.h"
-#include "alu.h"
-#include "filters/biquad.h"
+#include "core/filters/biquad.h"
+#include "effectslot.h"
 #include "vector.h"
 
 
 namespace {
 
+constexpr float LowpassFreqRef{5000.0f};
+
 struct EchoState final : public EffectState {
     al::vector<float,16> mSampleBuffer;
 
@@ -95,7 +97,7 @@ void EchoState::update(const ALCcontext *context, const EffectSlot *slot,
     mTap[1].delay = float2uint(props->Echo.LRDelay*frequency + 0.5f) + mTap[0].delay;
 
     const float gainhf{maxf(1.0f - props->Echo.Damping, 0.0625f)}; /* Limit -24dB */
-    mFilter.setParamsFromSlope(BiquadType::HighShelf, LOWPASSFREQREF/frequency, gainhf, 1.0f);
+    mFilter.setParamsFromSlope(BiquadType::HighShelf, LowpassFreqRef/frequency, gainhf, 1.0f);
 
     mFeedGain = props->Echo.Feedback;
 
diff --git a/alc/effects/equalizer.cpp b/alc/effects/equalizer.cpp
index 19d38498..c311a941 100644
--- a/alc/effects/equalizer.cpp
+++ b/alc/effects/equalizer.cpp
@@ -26,11 +26,10 @@
 #include <algorithm>
 #include <functional>
 
-#include "al/auxeffectslot.h"
 #include "alcmain.h"
 #include "alcontext.h"
-#include "alu.h"
-#include "filters/biquad.h"
+#include "core/filters/biquad.h"
+#include "effectslot.h"
 #include "vecmat.h"
 
 
diff --git a/alc/effects/modulator.cpp b/alc/effects/modulator.cpp
index 7e4f9fc0..a0af9890 100644
--- a/alc/effects/modulator.cpp
+++ b/alc/effects/modulator.cpp
@@ -26,11 +26,10 @@
 #include <cmath>
 #include <algorithm>
 
-#include "al/auxeffectslot.h"
 #include "alcmain.h"
 #include "alcontext.h"
-#include "alu.h"
-#include "filters/biquad.h"
+#include "core/filters/biquad.h"
+#include "effectslot.h"
 #include "vecmat.h"
 
 
diff --git a/alc/effects/reverb.cpp b/alc/effects/reverb.cpp
index 6471b210..a4b423c7 100644
--- a/alc/effects/reverb.cpp
+++ b/alc/effects/reverb.cpp
@@ -29,13 +29,12 @@
 #include <algorithm>
 #include <functional>
 
-#include "al/auxeffectslot.h"
-#include "al/listener.h"
 #include "alcmain.h"
 #include "alcontext.h"
-#include "alu.h"
+#include "alnumeric.h"
 #include "bformatdec.h"
-#include "filters/biquad.h"
+#include "core/filters/biquad.h"
+#include "effectslot.h"
 #include "vector.h"
 #include "vecmat.h"
 
diff --git a/alc/front_stablizer.h b/alc/front_stablizer.h
index 94882835..0fedeb50 100644
--- a/alc/front_stablizer.h
+++ b/alc/front_stablizer.h
@@ -6,7 +6,7 @@
 
 #include "almalloc.h"
 #include "core/bufferline.h"
-#include "filters/splitter.h"
+#include "core/filters/splitter.h"
 
 
 struct FrontStablizer {
diff --git a/alc/hrtf.cpp b/alc/hrtf.cpp
index 12cea416..01dc342f 100644
--- a/alc/hrtf.cpp
+++ b/alc/hrtf.cpp
@@ -47,7 +47,7 @@
 #include "alnumeric.h"
 #include "aloptional.h"
 #include "alspan.h"
-#include "filters/splitter.h"
+#include "core/filters/splitter.h"
 #include "logging.h"
 #include "math_defs.h"
 #include "opthelpers.h"
diff --git a/alc/hrtf.h b/alc/hrtf.h
index 3b9a272c..c26947de 100644
--- a/alc/hrtf.h
+++ b/alc/hrtf.h
@@ -11,7 +11,7 @@
 #include "ambidefs.h"
 #include "atomic.h"
 #include "core/bufferline.h"
-#include "filters/splitter.h"
+#include "core/filters/splitter.h"
 #include "intrusive_ptr.h"
 #include "vector.h"
 
diff --git a/alc/voice.cpp b/alc/voice.cpp
index 54775a72..8b5cd02f 100644
--- a/alc/voice.cpp
+++ b/alc/voice.cpp
@@ -47,10 +47,10 @@
 #include "alstring.h"
 #include "alu.h"
 #include "core/devformat.h"
+#include "core/filters/biquad.h"
+#include "core/filters/nfc.h"
+#include "core/filters/splitter.h"
 #include "cpu_caps.h"
-#include "filters/biquad.h"
-#include "filters/nfc.h"
-#include "filters/splitter.h"
 #include "fmt_traits.h"
 #include "hrtf.h"
 #include "inprogext.h"
diff --git a/alc/voice.h b/alc/voice.h
index 8a7d12d1..00012de3 100644
--- a/alc/voice.h
+++ b/alc/voice.h
@@ -8,9 +8,9 @@
 #include "alu.h"
 #include "buffer_storage.h"
 #include "core/devformat.h"
-#include "filters/biquad.h"
-#include "filters/nfc.h"
-#include "filters/splitter.h"
+#include "core/filters/biquad.h"
+#include "core/filters/nfc.h"
+#include "core/filters/splitter.h"
 #include "hrtf.h"
 #include "mixer/defs.h"
 
diff --git a/alc/filters/biquad.cpp b/core/filters/biquad.cpp
similarity index 100%
rename from alc/filters/biquad.cpp
rename to core/filters/biquad.cpp
diff --git a/alc/filters/biquad.h b/core/filters/biquad.h
similarity index 98%
rename from alc/filters/biquad.h
rename to core/filters/biquad.h
index 3ce70cb3..b2e2cfdb 100644
--- a/alc/filters/biquad.h
+++ b/core/filters/biquad.h
@@ -1,5 +1,5 @@
-#ifndef FILTERS_BIQUAD_H
-#define FILTERS_BIQUAD_H
+#ifndef CORE_FILTERS_BIQUAD_H
+#define CORE_FILTERS_BIQUAD_H
 
 #include <algorithm>
 #include <cmath>
@@ -141,4 +141,4 @@ struct DualBiquadR {
 using BiquadFilter = BiquadFilterR<float>;
 using DualBiquad = DualBiquadR<float>;
 
-#endif /* FILTERS_BIQUAD_H */
+#endif /* CORE_FILTERS_BIQUAD_H */
diff --git a/alc/filters/nfc.cpp b/core/filters/nfc.cpp
similarity index 100%
rename from alc/filters/nfc.cpp
rename to core/filters/nfc.cpp
diff --git a/alc/filters/nfc.h b/core/filters/nfc.h
similarity index 95%
rename from alc/filters/nfc.h
rename to core/filters/nfc.h
index 2327c966..33f67a5f 100644
--- a/alc/filters/nfc.h
+++ b/core/filters/nfc.h
@@ -1,5 +1,5 @@
-#ifndef FILTER_NFC_H
-#define FILTER_NFC_H
+#ifndef CORE_FILTERS_NFC_H
+#define CORE_FILTERS_NFC_H
 
 #include <cstddef>
 
@@ -60,4 +60,4 @@ public:
     void process4(const al::span<const float> src, float *RESTRICT dst);
 };
 
-#endif /* FILTER_NFC_H */
+#endif /* CORE_FILTERS_NFC_H */
diff --git a/alc/filters/splitter.cpp b/core/filters/splitter.cpp
similarity index 100%
rename from alc/filters/splitter.cpp
rename to core/filters/splitter.cpp
diff --git a/alc/filters/splitter.h b/core/filters/splitter.h
similarity index 90%
rename from alc/filters/splitter.h
rename to core/filters/splitter.h
index 18ab4998..ba548c10 100644
--- a/alc/filters/splitter.h
+++ b/core/filters/splitter.h
@@ -1,5 +1,5 @@
-#ifndef FILTER_SPLITTER_H
-#define FILTER_SPLITTER_H
+#ifndef CORE_FILTERS_SPLITTER_H
+#define CORE_FILTERS_SPLITTER_H
 
 #include <cstddef>
 
@@ -33,4 +33,4 @@ public:
 };
 using BandSplitter = BandSplitterR<float>;
 
-#endif /* FILTER_SPLITTER_H */
+#endif /* CORE_FILTERS_SPLITTER_H */