This review part covers the T/S parameter and free-air impedance measurements for the driver units used in the NHT 2.5i loudspeaker.
Tweeter:
The tweeter used in the 2.5i model is made by SEAS and is basically the same driver as the SEAS 25TAF-D (H534) driver, but the one NHT uses is called 25TAF-D (H858-NHT). This tweeter version uses a slightly smaller face plate of 98mm instead of the 104mm used in the H534. The H858 tweeter version was manufactured in a separate line with tighter tolerances and quality control compared to the H534 version.
The 25TAF-D (H858-NHT) has an aluminium dome and the voice coil is immersed in magnetic fluid.
T/S Parameters:
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The tweeter resonance frequency is within 1.5-4% from the official specification.
Impedance:
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The two tweeter samples measures almost identical.
Mid-woofer:
The mid-woofer used in the 2.5i model is made by Peerless. The 6.5″ Peerless (830301) mid-woofer has a polypropylene cone with a concave dust cap. The basket is made of stamped steel and it has a small 72mm magnet.
T/S Parameters:
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The T/S parameters are almost identical to the official specification. With its low Fs, high Qts and with an EBP of 45, this mid-woofer is made for a closed box configuration.
Impedance:
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Almost identical impedance plot for the two samples with a small wrinkle around 850Hz.
Sub-woofer:
The sub-woofer used in the 2.5i model is made by Peerless. The 8″ Peerless (830302) sub-woofer has a polypropylene cone with a textile dust cap. The basket is made of stamped steel.
T/S Parameters:
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Slightly higher Fs and Qts compared to the official specification.
Impedance:
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Identical impedance plots between the two driver samples.
Go to NHT 2.5i review part 3