diff --git a/Machines/Apple/Macintosh/DriveSpeedAccumulator.cpp b/Machines/Apple/Macintosh/DriveSpeedAccumulator.cpp
index f51f0f5a7..b4277def4 100644
--- a/Machines/Apple/Macintosh/DriveSpeedAccumulator.cpp
+++ b/Machines/Apple/Macintosh/DriveSpeedAccumulator.cpp
@@ -11,7 +11,7 @@
 using namespace Apple::Macintosh;
 
 void DriveSpeedAccumulator::post_sample(uint8_t sample) {
-	if(!number_of_drives_) return;
+	if(!delegate_) return;
 
 	// An Euler-esque approximation is used here: just collect all
 	// the samples until there is a certain small quantity of them,
@@ -50,14 +50,7 @@ void DriveSpeedAccumulator::post_sample(uint8_t sample) {
 		const float normalised_sum = float(sum) / float(samples_.size());
 		const float rotation_speed = (normalised_sum * 27.08f) - 259.0f;
 
-		for(int c = 0; c < number_of_drives_; ++c) {
-			drives_[c]->set_rotation_speed(rotation_speed);
-		}
-//		printf("RPM: %0.2f (%d sum)\n", rotation_speed, sum);
+		delegate_->drive_speed_accumulator_set_drive_speed(this, rotation_speed);
 	}
 }
 
-void DriveSpeedAccumulator::add_drive(Apple::Macintosh::DoubleDensityDrive *drive) {
-	drives_[number_of_drives_] = drive;
-	++number_of_drives_;
-}
diff --git a/Machines/Apple/Macintosh/DriveSpeedAccumulator.hpp b/Machines/Apple/Macintosh/DriveSpeedAccumulator.hpp
index 18a8d41b8..f626217d1 100644
--- a/Machines/Apple/Macintosh/DriveSpeedAccumulator.hpp
+++ b/Machines/Apple/Macintosh/DriveSpeedAccumulator.hpp
@@ -13,8 +13,6 @@
 #include <cstddef>
 #include <cstdint>
 
-#include "../../../Components/DiskII/MacintoshDoubleDensityDrive.hpp"
-
 namespace Apple {
 namespace Macintosh {
 
@@ -25,18 +23,20 @@ class DriveSpeedAccumulator {
 		*/
 		void post_sample(uint8_t sample);
 
+		struct Delegate {
+			virtual void drive_speed_accumulator_set_drive_speed(DriveSpeedAccumulator *, float speed) = 0;
+		};
 		/*!
-			Adds a connected drive. Up to two of these
-			can be supplied. Only Macintosh DoubleDensityDrives
-			are supported.
+			Sets the delegate to receive drive speed changes.
 		*/
-		void add_drive(Apple::Macintosh::DoubleDensityDrive *drive);
+		void set_delegate(Delegate *delegate) {
+			delegate_ = delegate;;
+		}
 
 	private:
 		std::array<uint8_t, 20> samples_;
 		std::size_t sample_pointer_ = 0;
-		Apple::Macintosh::DoubleDensityDrive *drives_[2] = {nullptr, nullptr};
-		int number_of_drives_ = 0;
+		Delegate *delegate_ = nullptr;
 };
 
 }
diff --git a/Machines/Apple/Macintosh/Macintosh.cpp b/Machines/Apple/Macintosh/Macintosh.cpp
index 89b303775..16d8c6bef 100644
--- a/Machines/Apple/Macintosh/Macintosh.cpp
+++ b/Machines/Apple/Macintosh/Macintosh.cpp
@@ -57,7 +57,8 @@ template <Analyser::Static::Macintosh::Target::Model model> class ConcreteMachin
 	public CPU::MC68000::BusHandler,
 	public KeyboardMachine::MappedMachine,
 	public Zilog::SCC::z8530::Delegate,
-	public Activity::Source {
+	public Activity::Source,
+	public DriveSpeedAccumulator::Delegate {
 	public:
 		using Target = Analyser::Static::Macintosh::Target;
 
@@ -119,8 +120,9 @@ template <Analyser::Static::Macintosh::Target::Model model> class ConcreteMachin
 			iwm_->set_drive(1, &drives_[1]);
 
 			// If they are 400kb drives, also attach them to the drive-speed accumulator.
-			if(!drives_[0].is_800k()) drive_speed_accumulator_.add_drive(&drives_[0]);
-			if(!drives_[1].is_800k()) drive_speed_accumulator_.add_drive(&drives_[1]);
+			if(!drives_[0].is_800k() || !drives_[1].is_800k()) {
+				drive_speed_accumulator_.set_delegate(this);
+			}
 
 			// Make sure interrupt changes from the SCC are observed.
 			scc_.set_delegate(this);
@@ -444,6 +446,12 @@ template <Analyser::Static::Macintosh::Target::Model model> class ConcreteMachin
 		}
 
 	private:
+		void drive_speed_accumulator_set_drive_speed(DriveSpeedAccumulator *, float speed) override {
+			iwm_.flush();
+			drives_[0].set_rotation_speed(speed);
+			drives_[1].set_rotation_speed(speed);
+		}
+
 		forceinline void adjust_phase() {
 			++phase_;
 		}