Purifi-based monitor - options

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IslandPink
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#181 Re: Purifi-based monitor - options

Post by 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.
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#182 Re: Purifi-based monitor - options

Post by 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.
Purifi_LP_03Feb23.JPG
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Monitor_SB_HP_03Feb23.JPG
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#183 Re: Purifi-based monitor - options

Post by 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
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#184 Re: Purifi-based monitor - options

Post by 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
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vinylnvalves
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#185 Re: Purifi-based monitor - options

Post by 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.
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#186 Re: Purifi-based monitor - options

Post by Paul Barker »

Like the style. Diana would trip on them though, so not for me.
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#187 Re: Purifi-based monitor - options

Post by 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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#188 Re: Purifi-based monitor - options

Post by 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.
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#189 Re: Purifi-based monitor - options

Post by Nick »

I would assume that R2 is representing the DCR of the driver. So the second part of your question.
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#190 Re: Purifi-based monitor - options

Post by IslandPink »

Correct Nick, thanks.
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#191 Re: Purifi-based monitor - options

Post by IslandPink »

Well, we're at the finish line now. We had another life-related delay to Dave finishing the cabinets, but the work is now done and is exemplary. The main veneer is American Ash. The three of us spent a very hot 3 1/2 hours yesterday getting all the wiring in place and lightly stuffing with long-haired wool.
The crossovers are in diecast aluminium boxes, I will provide some pics later.
Dave will take them over to Jon's studio on Sunday for first testing as a pair. I hope to get over in the next few days and will also try a test with my own CD/DAC kit for comparison against the mono sound in my room.

Image

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#192 Re: Purifi-based monitor - options

Post by Paul Barker »

Beauty to behold, I loved the one you brought to Owston.
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#193 Re: Purifi-based monitor - options

Post by Ali Tait »

Top notch!
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#194 Re: Purifi-based monitor - options

Post by rowuk »

IslandPink wrote: Sat Feb 04, 2023 2:29 pm 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
If the baffle were wider (or adding wings), would it fill in the mid bass dip?
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#195 Re: Purifi-based monitor - options

Post by IslandPink »

It might fill some of it but not the 150Hz part, which is a feature of my room.
In John's studio, I intend to get a short testing session to see how the bass has come up in his smaller room, and whether anything like a BSC is required.
Currently he's in a honeymoon period, calling me a 'Genius' and a 'God' so I won't bother him just yet, although I haven't heard them and would love to hear them now in stereo.
The way they are being fed, they can have some bass boost added either at the amp or earlier in the chain.
Personally I want to also hear them with my front end , DAC and chip amp, where there's less electronics in the path.
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