diff --git a/kokoro/custom_stft.py b/kokoro/custom_stft.py
new file mode 100644
index 0000000..15f3378
--- /dev/null
+++ b/kokoro/custom_stft.py
@@ -0,0 +1,198 @@
+from attr import attr
+import torch
+import torch.nn as nn
+import torch.nn.functional as F
+import numpy as np
+from scipy.signal import get_window
+
+class CustomSTFT(nn.Module):
+    """
+    STFT/iSTFT without unfold/complex ops, using conv1d and conv_transpose1d.
+
+    - forward STFT => Real-part conv1d + Imag-part conv1d
+    - inverse STFT => Real-part conv_transpose1d + Imag-part conv_transpose1d + sum
+    - avoids F.unfold, so easier to export to ONNX
+    - uses replicate or constant padding for 'center=True' to approximate 'reflect' 
+      (reflect is not supported for dynamic shapes in ONNX)
+    """
+
+    def __init__(
+        self,
+        filter_length=800,
+        hop_length=200,
+        win_length=800,
+        window="hann",
+        center=True,
+        pad_mode="replicate",  # or 'constant'
+    ):
+        super().__init__()
+        self.filter_length = filter_length
+        self.hop_length = hop_length
+        self.win_length = win_length
+        self.n_fft = filter_length
+        self.center = center
+        self.pad_mode = pad_mode
+
+        # Number of frequency bins for real-valued STFT with onesided=True
+        self.freq_bins = self.n_fft // 2 + 1
+
+        # Build window
+        win_np = get_window(window, self.win_length, fftbins=True).astype(np.float32)
+        window_tensor = torch.from_numpy(win_np)
+        if self.win_length < self.n_fft:
+            # Zero-pad up to n_fft
+            extra = self.n_fft - self.win_length
+            window_tensor = F.pad(window_tensor, (0, extra))
+        elif self.win_length > self.n_fft:
+            window_tensor = window_tensor[: self.n_fft]
+        self.register_buffer("window", window_tensor)
+
+        # Precompute forward DFT (real, imag)
+        # PyTorch stft uses e^{-j 2 pi k n / N} => real=cos(...), imag=-sin(...)
+        n = np.arange(self.n_fft)
+        k = np.arange(self.freq_bins)
+        angle = 2 * np.pi * np.outer(k, n) / self.n_fft  # shape (freq_bins, n_fft)
+        dft_real = np.cos(angle)
+        dft_imag = -np.sin(angle)  # note negative sign
+
+        # Combine window and dft => shape (freq_bins, filter_length)
+        # We'll make 2 conv weight tensors of shape (freq_bins, 1, filter_length).
+        forward_window = window_tensor.numpy()  # shape (n_fft,)
+        forward_real = dft_real * forward_window  # (freq_bins, n_fft)
+        forward_imag = dft_imag * forward_window
+
+        # Convert to PyTorch
+        forward_real_torch = torch.from_numpy(forward_real).float()
+        forward_imag_torch = torch.from_numpy(forward_imag).float()
+
+        # Register as Conv1d weight => (out_channels, in_channels, kernel_size)
+        # out_channels = freq_bins, in_channels=1, kernel_size=n_fft
+        self.register_buffer(
+            "weight_forward_real", forward_real_torch.unsqueeze(1)
+        )
+        self.register_buffer(
+            "weight_forward_imag", forward_imag_torch.unsqueeze(1)
+        )
+
+        # Precompute inverse DFT
+        # Real iFFT formula => scale = 1/n_fft, doubling for bins 1..freq_bins-2 if n_fft even, etc.
+        # For simplicity, we won't do the "DC/nyquist not doubled" approach here. 
+        # If you want perfect real iSTFT, you can add that logic. 
+        # This version just yields good approximate reconstruction with Hann + typical overlap.
+        inv_scale = 1.0 / self.n_fft
+        n = np.arange(self.n_fft)
+        angle_t = 2 * np.pi * np.outer(n, k) / self.n_fft  # shape (n_fft, freq_bins)
+        idft_cos = np.cos(angle_t).T  # => (freq_bins, n_fft)
+        idft_sin = np.sin(angle_t).T  # => (freq_bins, n_fft)
+
+        # Multiply by window again for typical overlap-add
+        # We also incorporate the scale factor 1/n_fft
+        inv_window = window_tensor.numpy() * inv_scale
+        backward_real = idft_cos * inv_window  # (freq_bins, n_fft)
+        backward_imag = idft_sin * inv_window
+
+        # We'll implement iSTFT as real+imag conv_transpose with stride=hop.
+        self.register_buffer(
+            "weight_backward_real", torch.from_numpy(backward_real).float().unsqueeze(1)
+        )
+        self.register_buffer(
+            "weight_backward_imag", torch.from_numpy(backward_imag).float().unsqueeze(1)
+        )
+        
+
+
+    def transform(self, waveform: torch.Tensor):
+        """
+        Forward STFT => returns magnitude, phase
+        Output shape => (batch, freq_bins, frames)
+        """
+        # waveform shape => (B, T).  conv1d expects (B, 1, T).
+        # Optional center pad
+        if self.center:
+            pad_len = self.n_fft // 2
+            waveform = F.pad(waveform, (pad_len, pad_len), mode=self.pad_mode)
+
+        x = waveform.unsqueeze(1)  # => (B, 1, T)
+        # Convolution to get real part => shape (B, freq_bins, frames)
+        real_out = F.conv1d(
+            x,
+            self.weight_forward_real,
+            bias=None,
+            stride=self.hop_length,
+            padding=0,
+        )
+        # Imag part
+        imag_out = F.conv1d(
+            x,
+            self.weight_forward_imag,
+            bias=None,
+            stride=self.hop_length,
+            padding=0,
+        )
+
+        # magnitude, phase
+        magnitude = torch.sqrt(real_out**2 + imag_out**2 + 1e-14)
+        phase = torch.atan2(imag_out, real_out)
+        # Handle the case where imag_out is 0 and real_out is negative to correct ONNX atan2 to match PyTorch
+        # In this case, PyTorch returns pi, ONNX returns -pi
+        correction_mask = (imag_out == 0) & (real_out < 0)
+        phase[correction_mask] = torch.pi
+        return magnitude, phase
+
+
+    def inverse(self, magnitude: torch.Tensor, phase: torch.Tensor, length=None):
+        """
+        Inverse STFT => returns waveform shape (B, T).
+        """
+        # magnitude, phase => (B, freq_bins, frames)
+        # Re-create real/imag => shape (B, freq_bins, frames)
+        real_part = magnitude * torch.cos(phase)
+        imag_part = magnitude * torch.sin(phase)
+
+        # conv_transpose wants shape (B, freq_bins, frames). We'll treat "frames" as time dimension
+        # so we do (B, freq_bins, frames) => (B, freq_bins, frames)
+        # But PyTorch conv_transpose1d expects (B, in_channels, input_length)
+        real_part = real_part  # (B, freq_bins, frames)
+        imag_part = imag_part
+
+        # real iSTFT => convolve with "backward_real", "backward_imag", and sum
+        # We'll do 2 conv_transpose calls, each giving (B, 1, time),
+        # then add them => (B, 1, time).
+        real_rec = F.conv_transpose1d(
+            real_part,
+            self.weight_backward_real,  # shape (freq_bins, 1, filter_length)
+            bias=None,
+            stride=self.hop_length,
+            padding=0,
+        )
+        imag_rec = F.conv_transpose1d(
+            imag_part,
+            self.weight_backward_imag,
+            bias=None,
+            stride=self.hop_length,
+            padding=0,
+        )
+        # sum => (B, 1, time)
+        waveform = real_rec - imag_rec  # typical real iFFT has minus for imaginary part
+
+        # If we used "center=True" in forward, we should remove pad
+        if self.center:
+            pad_len = self.n_fft // 2
+            # Because of transposed convolution, total length might have extra samples
+            # We remove `pad_len` from start & end if possible
+            waveform = waveform[..., pad_len:-pad_len]
+
+        # If a specific length is desired, clamp
+        if length is not None:
+            waveform = waveform[..., :length]
+
+        # shape => (B, T)
+        return waveform
+
+    def forward(self, x: torch.Tensor):
+        """
+        Full STFT -> iSTFT pass: returns time-domain reconstruction.
+        Same interface as your original code.
+        """
+        mag, phase = self.transform(x)
+        return self.inverse(mag, phase, length=x.shape[-1])
diff --git a/kokoro/istftnet.py b/kokoro/istftnet.py
index 01289b2..e61e510 100644
--- a/kokoro/istftnet.py
+++ b/kokoro/istftnet.py
@@ -7,6 +7,8 @@ import torch
 import torch.nn as nn
 import torch.nn.functional as F
 
+from kokoro.custom_stft import CustomSTFT
+
 
 # https://github.com/yl4579/StyleTTS2/blob/main/Modules/utils.py
 def init_weights(m, mean=0.0, std=0.01):
@@ -254,7 +256,7 @@ class SourceModuleHnNSF(nn.Module):
 
 
 class Generator(nn.Module):
-    def __init__(self, style_dim, resblock_kernel_sizes, upsample_rates, upsample_initial_channel, resblock_dilation_sizes, upsample_kernel_sizes, gen_istft_n_fft, gen_istft_hop_size):
+    def __init__(self, style_dim, resblock_kernel_sizes, upsample_rates, upsample_initial_channel, resblock_dilation_sizes, upsample_kernel_sizes, gen_istft_n_fft, gen_istft_hop_size, disable_complex=False):
         super(Generator, self).__init__()
         self.num_kernels = len(resblock_kernel_sizes)
         self.num_upsamples = len(upsample_rates)
@@ -289,7 +291,11 @@ class Generator(nn.Module):
         self.ups.apply(init_weights)
         self.conv_post.apply(init_weights)
         self.reflection_pad = nn.ReflectionPad1d((1, 0))
-        self.stft = TorchSTFT(filter_length=gen_istft_n_fft, hop_length=gen_istft_hop_size, win_length=gen_istft_n_fft)
+        self.stft = (
+            CustomSTFT(filter_length=gen_istft_n_fft, hop_length=gen_istft_hop_size, win_length=gen_istft_n_fft)
+            if disable_complex
+            else TorchSTFT(filter_length=gen_istft_n_fft, hop_length=gen_istft_hop_size, win_length=gen_istft_n_fft)
+        )
 
     def forward(self, x, s, f0):
         with torch.no_grad():
@@ -383,7 +389,8 @@ class Decoder(nn.Module):
                  upsample_initial_channel,
                  resblock_dilation_sizes,
                  upsample_kernel_sizes,
-                 gen_istft_n_fft, gen_istft_hop_size):
+                 gen_istft_n_fft, gen_istft_hop_size,
+                 disable_complex=False):
         super().__init__()
         self.encode = AdainResBlk1d(dim_in + 2, 1024, style_dim)
         self.decode = nn.ModuleList()
@@ -396,7 +403,7 @@ class Decoder(nn.Module):
         self.asr_res = nn.Sequential(weight_norm(nn.Conv1d(512, 64, kernel_size=1)))
         self.generator = Generator(style_dim, resblock_kernel_sizes, upsample_rates, 
                                    upsample_initial_channel, resblock_dilation_sizes, 
-                                   upsample_kernel_sizes, gen_istft_n_fft, gen_istft_hop_size)
+                                   upsample_kernel_sizes, gen_istft_n_fft, gen_istft_hop_size, disable_complex=disable_complex)
 
     def forward(self, asr, F0_curve, N, s):
         F0 = self.F0_conv(F0_curve.unsqueeze(1))
diff --git a/kokoro/model.py b/kokoro/model.py
index 27ab5c1..25659ad 100644
--- a/kokoro/model.py
+++ b/kokoro/model.py
@@ -26,7 +26,7 @@ class KModel(torch.nn.Module):
 
     REPO_ID = 'hexgrad/Kokoro-82M'
 
-    def __init__(self, config: Union[Dict, str, None] = None, model: Optional[str] = None):
+    def __init__(self, config: Union[Dict, str, None] = None, model: Optional[str] = None, disable_complex: bool = False):
         super().__init__()
         if not isinstance(config, dict):
             if not config:
@@ -49,7 +49,7 @@ class KModel(torch.nn.Module):
         )
         self.decoder = Decoder(
             dim_in=config['hidden_dim'], style_dim=config['style_dim'],
-            dim_out=config['n_mels'], **config['istftnet']
+            dim_out=config['n_mels'], disable_complex=disable_complex, **config['istftnet']
         )
         if not model:
             model = hf_hub_download(repo_id=KModel.REPO_ID, filename='kokoro-v1_0.pth')
@@ -72,30 +72,29 @@ class KModel(torch.nn.Module):
         pred_dur: Optional[torch.LongTensor] = None
 
     @torch.no_grad()
-    def forward(
+    def forward_with_tokens(
         self,
-        phonemes: str,
+        input_ids: torch.LongTensor,
         ref_s: torch.FloatTensor,
-        speed: Number = 1,
-        return_output: bool = False # MARK: BACKWARD COMPAT
-    ) -> Union['KModel.Output', torch.FloatTensor]:
-        input_ids = list(filter(lambda i: i is not None, map(lambda p: self.vocab.get(p), phonemes)))
-        logger.debug(f"phonemes: {phonemes} -> input_ids: {input_ids}")
-        assert len(input_ids)+2 <= self.context_length, (len(input_ids)+2, self.context_length)
-        input_ids = torch.LongTensor([[0, *input_ids, 0]]).to(self.device)
-        input_lengths = torch.LongTensor([input_ids.shape[-1]]).to(self.device)
+        speed: Number = 1
+    ) -> tuple[torch.FloatTensor, torch.LongTensor]:
+        input_lengths = torch.full(
+            (input_ids.shape[0],), 
+            input_ids.shape[-1], 
+            device=input_ids.device,
+            dtype=torch.long
+        )
+
         text_mask = torch.arange(input_lengths.max()).unsqueeze(0).expand(input_lengths.shape[0], -1).type_as(input_lengths)
         text_mask = torch.gt(text_mask+1, input_lengths.unsqueeze(1)).to(self.device)
         bert_dur = self.bert(input_ids, attention_mask=(~text_mask).int())
         d_en = self.bert_encoder(bert_dur).transpose(-1, -2)
-        ref_s = ref_s.to(self.device)
         s = ref_s[:, 128:]
         d = self.predictor.text_encoder(d_en, s, input_lengths, text_mask)
         x, _ = self.predictor.lstm(d)
         duration = self.predictor.duration_proj(x)
         duration = torch.sigmoid(duration).sum(axis=-1) / speed
         pred_dur = torch.round(duration).clamp(min=1).long().squeeze()
-        logger.debug(f"pred_dur: {pred_dur}")
         indices = torch.repeat_interleave(torch.arange(input_ids.shape[1], device=self.device), pred_dur)
         pred_aln_trg = torch.zeros((input_ids.shape[1], indices.shape[0]), device=self.device)
         pred_aln_trg[indices, torch.arange(indices.shape[0])] = 1
@@ -104,5 +103,37 @@ class KModel(torch.nn.Module):
         F0_pred, N_pred = self.predictor.F0Ntrain(en, s)
         t_en = self.text_encoder(input_ids, input_lengths, text_mask)
         asr = t_en @ pred_aln_trg
-        audio = self.decoder(asr, F0_pred, N_pred, ref_s[:, :128]).squeeze().cpu()
-        return self.Output(audio=audio, pred_dur=pred_dur.cpu()) if return_output else audio
+        audio = self.decoder(asr, F0_pred, N_pred, ref_s[:, :128]).squeeze()
+        return audio, pred_dur
+
+    def forward(
+        self,
+        phonemes: str,
+        ref_s: torch.FloatTensor,
+        speed: Number = 1,
+        return_output: bool = False
+    ) -> Union['KModel.Output', torch.FloatTensor]:
+        input_ids = list(filter(lambda i: i is not None, map(lambda p: self.vocab.get(p), phonemes)))
+        logger.debug(f"phonemes: {phonemes} -> input_ids: {input_ids}")
+        assert len(input_ids)+2 <= self.context_length, (len(input_ids)+2, self.context_length)
+        input_ids = torch.LongTensor([[0, *input_ids, 0]]).to(self.device)
+        ref_s = ref_s.to(self.device)
+        audio, pred_dur = self.forward_with_tokens(input_ids, ref_s, speed)
+        audio = audio.squeeze().cpu()
+        pred_dur = pred_dur.cpu() if pred_dur is not None else None
+        logger.debug(f"pred_dur: {pred_dur}")
+        return self.Output(audio=audio, pred_dur=pred_dur) if return_output else audio
+
+class KModelForONNX(torch.nn.Module):
+    def __init__(self, kmodel: KModel):
+        super().__init__()
+        self.kmodel = kmodel
+
+    def forward(
+        self,
+        input_ids: torch.LongTensor,
+        ref_s: torch.FloatTensor,
+        speed: Number = 1
+    ) -> tuple[torch.FloatTensor, torch.LongTensor]:
+        waveform, duration = self.kmodel.forward_with_tokens(input_ids, ref_s, speed)
+        return waveform
diff --git a/kokoro/modules.py b/kokoro/modules.py
index 2b72307..05d1575 100644
--- a/kokoro/modules.py
+++ b/kokoro/modules.py
@@ -50,21 +50,21 @@ class TextEncoder(nn.Module):
     def forward(self, x, input_lengths, m):
         x = self.embedding(x)  # [B, T, emb]
         x = x.transpose(1, 2)  # [B, emb, T]
-        m = m.to(input_lengths.device).unsqueeze(1)
+        m = m.unsqueeze(1)
         x.masked_fill_(m, 0.0)
         for c in self.cnn:
             x = c(x)
             x.masked_fill_(m, 0.0)
         x = x.transpose(1, 2)  # [B, T, chn]
-        input_lengths = input_lengths.cpu().numpy()
-        x = nn.utils.rnn.pack_padded_sequence(x, input_lengths, batch_first=True, enforce_sorted=False)
+        lengths = input_lengths if input_lengths.device == torch.device('cpu') else input_lengths.to('cpu')
+        x = nn.utils.rnn.pack_padded_sequence(x, lengths, batch_first=True, enforce_sorted=False)
         self.lstm.flatten_parameters()
         x, _ = self.lstm(x)
         x, _ = nn.utils.rnn.pad_packed_sequence(x, batch_first=True)
         x = x.transpose(-1, -2)
-        x_pad = torch.zeros([x.shape[0], x.shape[1], m.shape[-1]])
+        x_pad = torch.zeros([x.shape[0], x.shape[1], m.shape[-1]], device=x.device)
         x_pad[:, :, :x.shape[-1]] = x
-        x = x_pad.to(x.device)
+        x = x_pad
         x.masked_fill_(m, 0.0)
         return x
 
@@ -108,17 +108,15 @@ class ProsodyPredictor(nn.Module):
 
     def forward(self, texts, style, text_lengths, alignment, m):
         d = self.text_encoder(texts, style, text_lengths, m)
-        batch_size = d.shape[0]
-        text_size = d.shape[1]
-        input_lengths = text_lengths.cpu().numpy()
-        x = nn.utils.rnn.pack_padded_sequence(d, input_lengths, batch_first=True, enforce_sorted=False)
-        m = m.to(text_lengths.device).unsqueeze(1)
+        m = m.unsqueeze(1)
+        lengths = text_lengths if text_lengths.device == torch.device('cpu') else text_lengths.to('cpu')
+        x = nn.utils.rnn.pack_padded_sequence(d, lengths, batch_first=True, enforce_sorted=False)
         self.lstm.flatten_parameters()
         x, _ = self.lstm(x)
         x, _ = nn.utils.rnn.pad_packed_sequence(x, batch_first=True)
-        x_pad = torch.zeros([x.shape[0], m.shape[-1], x.shape[-1]])
+        x_pad = torch.zeros([x.shape[0], m.shape[-1], x.shape[-1]], device=x.device)
         x_pad[:, :x.shape[1], :] = x
-        x = x_pad.to(x.device)
+        x = x_pad
         duration = self.duration_proj(nn.functional.dropout(x, 0.5, training=False))
         en = (d.transpose(-1, -2) @ alignment)
         return duration.squeeze(-1), en
@@ -148,32 +146,33 @@ class DurationEncoder(nn.Module):
         self.sty_dim = sty_dim
 
     def forward(self, x, style, text_lengths, m):
-        masks = m.to(text_lengths.device)
+        masks = m
         x = x.permute(2, 0, 1)
         s = style.expand(x.shape[0], x.shape[1], -1)
         x = torch.cat([x, s], axis=-1)
         x.masked_fill_(masks.unsqueeze(-1).transpose(0, 1), 0.0)
         x = x.transpose(0, 1)
-        input_lengths = text_lengths.cpu().numpy()
         x = x.transpose(-1, -2)
         for block in self.lstms:
             if isinstance(block, AdaLayerNorm):
                 x = block(x.transpose(-1, -2), style).transpose(-1, -2)
-                x = torch.cat([x, s.permute(1, -1, 0)], axis=1)
+                x = torch.cat([x, s.permute(1, 2, 0)], axis=1)
                 x.masked_fill_(masks.unsqueeze(-1).transpose(-1, -2), 0.0)
             else:
+                lengths = text_lengths if text_lengths.device == torch.device('cpu') else text_lengths.to('cpu')
                 x = x.transpose(-1, -2)
                 x = nn.utils.rnn.pack_padded_sequence(
-                    x, input_lengths, batch_first=True, enforce_sorted=False)
+                    x, lengths, batch_first=True, enforce_sorted=False)
                 block.flatten_parameters()
                 x, _ = block(x)
                 x, _ = nn.utils.rnn.pad_packed_sequence(
                     x, batch_first=True)
                 x = F.dropout(x, p=self.dropout, training=False)
                 x = x.transpose(-1, -2)
-                x_pad = torch.zeros([x.shape[0], x.shape[1], m.shape[-1]])
+                x_pad = torch.zeros([x.shape[0], x.shape[1], m.shape[-1]], device=x.device)
                 x_pad[:, :, :x.shape[-1]] = x
-                x = x_pad.to(x.device)
+                x = x_pad
+
         return x.transpose(-1, -2)
 
 
diff --git a/tests/test_custom_stft.py b/tests/test_custom_stft.py
new file mode 100644
index 0000000..103c083
--- /dev/null
+++ b/tests/test_custom_stft.py
@@ -0,0 +1,81 @@
+import torch
+import numpy as np
+import pytest
+from kokoro.custom_stft import CustomSTFT
+from kokoro.istftnet import TorchSTFT
+import torch.nn.functional as F
+
+
+@pytest.fixture
+def sample_audio():
+    # Generate a sample audio signal (sine wave)
+    sample_rate = 16000
+    duration = 1.0  # seconds
+    t = torch.linspace(0, duration, int(sample_rate * duration))
+    frequency = 440.0  # Hz
+    signal = torch.sin(2 * np.pi * frequency * t)
+    return signal.unsqueeze(0)  # Add batch dimension
+
+
+def test_stft_reconstruction(sample_audio):
+    # Initialize both STFT implementations
+    custom_stft = CustomSTFT(filter_length=800, hop_length=200, win_length=800)
+    torch_stft = TorchSTFT(filter_length=800, hop_length=200, win_length=800)
+
+    # Process through both implementations
+    custom_output = custom_stft(sample_audio)
+    torch_output = torch_stft(sample_audio)
+
+    # Compare outputs
+    assert torch.allclose(custom_output, torch_output, rtol=1e-3, atol=1e-3)
+
+
+def test_magnitude_phase_consistency(sample_audio):
+    custom_stft = CustomSTFT(filter_length=800, hop_length=200, win_length=800)
+    torch_stft = TorchSTFT(filter_length=800, hop_length=200, win_length=800)
+
+    # Get magnitude and phase from both implementations
+    custom_mag, custom_phase = custom_stft.transform(sample_audio)
+    torch_mag, torch_phase = torch_stft.transform(sample_audio)
+
+    # Compare magnitudes ignoring the boundary frames
+    custom_mag_center = custom_mag[..., 2:-2]
+    torch_mag_center = torch_mag[..., 2:-2]
+    assert torch.allclose(custom_mag_center, torch_mag_center, rtol=1e-2, atol=1e-2)
+
+
+def test_batch_processing():
+    # Create a batch of signals
+    batch_size = 4
+    sample_rate = 16000
+    duration = 0.1  # shorter duration for faster testing
+    t = torch.linspace(0, duration, int(sample_rate * duration))
+    frequency = 440.0
+    signals = torch.sin(2 * np.pi * frequency * t).unsqueeze(0).repeat(batch_size, 1)
+
+    custom_stft = CustomSTFT(filter_length=800, hop_length=200, win_length=800)
+
+    # Process batch
+    output = custom_stft(signals)
+
+    # Check output shape
+    assert output.shape[0] == batch_size
+    assert len(output.shape) == 3  # (batch, 1, time)
+
+
+def test_different_window_sizes():
+    signal = torch.randn(1, 16000)  # 1 second of random noise
+
+    # Test with different window sizes
+    for filter_length in [512, 1024, 2048]:
+        custom_stft = CustomSTFT(
+            filter_length=filter_length,
+            hop_length=filter_length // 4,
+            win_length=filter_length,
+        )
+
+        # Forward and backward transform
+        output = custom_stft(signal)
+
+        # Check that output length is reasonable
+        assert output.shape[-1] >= signal.shape[-1]