Sep. 20, 2020

Purifi PTT6.5 Test Results in 1198 Transmission Line Enclosure

This blog post features the objective test data for the Purifi PTT6.5 woofer mounted in my own transmission line enclosure design.

1198 Floor Standing Transmission Line

Frequency Response Measurements

Test Setup: Ground plane method, mic distance 250mm (10") (Green), Black is port output

The response shows an F3 of around 36Hz with a well damped response.

Purifi PTT6.5 in 1198 TL Enclosure

Impedance Sweep

The impedance sweep shows an actual tuning frequency of 39Hz with good alignment. Adding additional line damping would lower this frequency slightly.

Distortion

Based on the result below you can expect a clean 105dB SPL using a distortion threshold of 1.0%.

Even at 95dB bass distortion remains around 0.50% at 70Hz, an excellent result for a 6.5" woofer.

95dB@1meter

100dB@1meter

105dB@1meter

110dB@1meter

Distortion raised quickly at 110dB however I'm not sure if my amplifier ran out of power in this instance.

Implementation

Below is the response with a 5mH inductor. This inductor can be used in a baffle step circuit to good effect.

Purifi PTT6.5 with 5mH Inductor

Interesting Comparison

Purifi advertises the PTT6.5 as having the same low distortion as a much larger driver such as those used in large scale studio monitors. Typically these large studio monitors will employ a 10" or 12" mid-woofer to cover the mid-bass and lower midrange. To test Purifi's claim I conducted a direct comparison against the B&C 12PE32 12" Mid-woofer in a small sealed enclosure. A distortion sweep at 100dB reveals that the Purifi does in fact produce less distortion than the B&C 12PE32!

Subjective Listening Impressions

The bass quality produced by the PTT6.5 is excellent. The lower midrange is lively and authoritative similar to what you would achieve with larger drivers.