Does AVAudioUnitEQ actually work on iOS?

No matter what I do, I can't get the AVAudioUnitEQ to actually do anything. If I set the globalGain for the AVAudioUnitEQ, it's definitely effecting the signal, but no matter what kind of EQ filterType I set or parameters, I'm not hearing any change to my sound, it's acting like a straight pass-through.

I've tried low pass, high pass, low shelf, high shelf, setting the gain, the bandwidth, everything I can think of, but nothing seems to make a difference.

Is AVAudioUnitEQ actually functional on iOS 8.4 and 9.1? I'm seeing exactly the same results on iPads with both versions of iOS.

Here's my basic engine setup, trying to get a low pass filter cutting off at 1000 hz.

engine = [[AVAudioEngine alloc] init];

equalizer = [[AVAudioUnitEQ alloc] initWithNumberOfBands:1];

AVAudioUnitEQFilterParameters *filterParameters = equalizer.bands[0];

filterParameters.filterType = AVAudioUnitEQFilterTypeLowPass;

filterParameters.frequency = 1000.0f;

equalizer.bypass = NO;  

[engine attachNode:equalizer];

mixer = [[AVAudioEnvironmentNode alloc] init];

[engine attachNode:mixer];

AVAudioEnvironmentReverbParameters *reverbParameters = mixer.reverbParameters;

reverbParameters.enable = YES;

[reverbParameters loadFactoryReverbPreset:kDefaultReverbType ]; 

[engine connect:mixer to:equalizer format:nil];

[engine connect:equalizer to:[engine mainMixerNode] format:nil];

然后，稍后，我将各种文件源连接到调音台并启动引擎。一切正常，但是无论我如何配置均衡器频段，我都从未听到过发生任何EQ，几乎尝试了我能想到的每个选项...

事实证明，各个频段以及均衡器节点本身都存在旁路。设置filterParameters.bypass = NO可以解决此问题。