That zoomed-in view actually shows a more concerning picture than the wide one did. Two things jump out:
The peak barely stands above its neighbors. Your "Ref" peak hits 100% at 0 μs, but the surrounding cycles are sitting at 80–90%. That's only about 1.5:1 dynamic range around the peak. A healthy impulse response should have the main peak dominate by a much larger margin — often 5–10× higher than nearby cycles. When the peak is only marginally taller than its neighbors, it usually means the measurement is being smothered by something else.
Pre-ringing is huge. You've got near-full-amplitude oscillation extending back to −3 ms before the impulse arrives. Some pre-ringing is normal in a band-limited swept-sine measurement (it's a deconvolution artifact), but not at 80–90% of the peak amplitude. That's way too much.
The oscillation looks like a single dominant frequency. Counting cycles, the ringing is around 3–5 kHz and the amplitude doesn't decay much across the visible window. A real impulse response contains a mix of frequencies that decays away from the peak; what you're seeing looks more like a sustained tone or a very high-Q resonance.
A few likely causes, roughly in order of probability:
- Low signal-to-noise ratio. If your sweep level is too quiet at the mic, the impulse buried in noise will look exactly like this — peak barely sticking out, "noise" filling everything else. Crank the output level (or use a longer sweep — 512k or 1M instead of 256k) and remeasure. REW shows an SNR figure on the measurement; aim for >50 dB, ideally >70 dB.
- Acoustic interference / leakage. Something else in the room is making noise during the sweep — fan, fridge, computer, the other speaker, even traffic. Check for steady background noise.
- Timing reference issue. The "Ref" marker at exactly 0 μs suggests you're using a loopback timing reference. If the loopback channel isn't actually carrying the reference signal cleanly (wrong input selected, wrong cable, or the loopback channel is picking up acoustic crosstalk), the deconvolution can produce exactly this kind of smeared mess. Verify your timing reference setup in REW preferences.
- A real, very high-Q resonance in the driver or cabinet. Less likely to look this severe, but possible — a sharp cone breakup mode or an enclosure resonance at ~4 kHz could ring this strongly. You'd see it as a tall, narrow spike in the frequency response.
I'd start by re-running the measurement and checking the SNR figure REW reports. If it's under ~50 dB, that's almost certainly your problem — more level, longer sweep, quieter room. If SNR is fine, then look hard at the timing reference setup.