Purifi-based monitor - options

[IslandPink]

I've just been pushing this project on and having some success. I've gone to the 2nd-order low pass on the Purifi ( with a 0.56mH air-core ) and it sounded nice, and measurements today confirmed that it works without having to reverse the tweeter polarity.
I had, however, more woofer output ( nearly 2dB ? .... ) after taking out the notch filter, so had to modify the L-pad to the tweeter somewhat to bring that up to match.
I will post plots later.

Incidentally, with the speaker running fairly loud, on test, I can hear the port chuffing a bit. However it's only at the very start of the sweep, so around 20 to 30 or 35Hz , and this is playing louder than Jon will need in the studio. So, given he isn't playing or recording Techno, this will be fit for purpose.

ps. Dave, our cabinet maker, is into the work on the first 'smart' monitor enclosure now, so I'm playing catch-up, and have been ordering some caps/resistors/tag-board and will buy a pair of ABS Hammond enclosures for the crossovers to fit to the back of the cabinet.

[IslandPink]

Here are the crossovers. They are both 2nd-order but transitional, so the slope of the HP is more like 1st-order in the crossover point, and then steepening away from that . I think that this is the way I avoided a dip at crossover, while having both drivers in phase. Bear in mind that the Purifi unit is rising from 1kHz to 3.5kHz, so it doesn't fall off as quick as the crossover suggests. It may also be more of a transitional 1st/2nd slope, acoustically.

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Monitor_SB_HP_03Feb23.JPG (163.44 KiB) Viewed 1746 times

[IslandPink]

This is the response at approx 1m, with the mic on-axis to the tweeter. This was from 6 different positions in my room, each using 4 sweeps. I think I used 12th-octave smoothing on each measurement before averaging.
The bass is down rather a lot, but I believe it'll rise quite a bit in Jon's smaller ( studio ) room. The monitor was positioned a good way out into the room here, on most of these measurements.
The big suckout around 150Hz is annoying and a feature of my room.
The roll-off above 11kHz is bogus and just a feature of the generic mic calibration file - Chris proved that the tweeter actually goes flat to 20kHz, at Owston.

Monitor_w2ndLP_3Feb23_ii.jpg (70.43 KiB) Viewed 1740 times

[IslandPink]

In actual use, Jon will likely be around 2m from the speakers, and approx 3" down from the tweeter axis. So, I did another final measurement to represent that. I think this one used 1/6th-octave smoothing , bearing in mind that was just one measurement. As you can see, the slight rise to 10kHz has been flattened.

Monitor_w2ndLP_3Feb23_2m.jpg (58.8 KiB) Viewed 1739 times

[vinylnvalves]

An interesting article on a speaker designed by the the brains behind Purifi drivers. Interestingly it uses a AMT for the top end.https://audioxpress.com/news/lyngdorf-a ... -ise-2023/. Nice design, footprint of the tripod legs takes up to too much floor space imho though.

[Paul Barker]

Like the style. Diana would trip on them though, so not for me.

[IslandPink]

This is from a couple of weeks ago. Dave sent us some pics of veneer work on the finals cabs, in-process.
I believe the plan is to darken this considerably with stain ; then a deep gloss as per piano finish...

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[Scottmoose]

Missed this as I'm away from home & not much audio time, but -question? Is that SPICE circuit diagram showing the actual LP, or is it also indicating some kind of approximation of the driver impedance? If it's the former -watch out for the power-handling on R2; it will be shunting a considerable part of the power input as well as heavily reducing the LF impedance, so it may be running a bit on the hot side. If so, it may be worth upping its rating or using suitable multiples for the target value.

[Nick]

I would assume that R2 is representing the DCR of the driver. So the second part of your question.

[IslandPink]

Correct Nick, thanks.