This blog post features the objective test data for the Purifi PTT6.5 woofer mounted in my own transmission line enclosure design.
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| 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.
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| 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.
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| 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.
1 comment
Greetings,
Just read through your experimentation with the Purifi 6.5 drivers. I purchased a pair of Purifi PTT6.5X08-NFA-01 drivers which I am pairing with the Dynaudio Esotar t330D’s that i have had forever in a 22L enclosure with a 2200hz passive xover and 5 ohm resistor to pull the esotar in line, I would like your opinion on the possibility of a vented rather than round ported enclosure. This must remain a small bookshelf speaker or I would try a TL like yours. Also, I have already been through the epic thread at DIY where everyone was using a 15L enc and losing it over port length and using passive radiators. I would like to keep the front baffle as small as possible and do not want a rear mounted port. Would it be possible to perhaps use a slotted port at the bottom of each side and what would the dimensions need to be for say a 14"H x 8"W x 17"D cabinet (inside dimensions)? I have made a mock up mdf cab with dim above only 16’ high rather than 14" high with a bottom front slotted port that is roughly 10" wide x 1" tall x 12" deep and it sounds pretty good but i have no way to measure so no idea where it is tuned to. Curious what your thoughts are. Never been a fan of passive radiators and bought the purifi for the low distortion rather than extreme bass output but would like to get what I can out of it without going PR or using a rear port.
Also, if you had the opportunity to try it, what were your impressions of this driver in a sealed cabinet? If it doesn’t roll off too crazy fast, maybe just go sealed and crossed to a sub somewhere between 50-80hz?
Sorry I am all questions but I am a fan of your work and would love to hear your thoughts.
Thanks.
Todd