Purifi-based monitor - options

Dedicated to those large boxes at one end of the room
User avatar
IslandPink
Social Sevices have been notified
Posts: 8833
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#16 Re: Purifi-based monitor - options

Post by IslandPink »

Going through all options, I don't think I can get port velocity from Hornresp, but i will search on the DIY Audio thread as well.

In the meantime I did a quick sim of what the driver will deliver on the sealed 30 litre enclosure that I am going to first test the driver on.
This looks quite good. The group delay at 40Hz is slightly less, but similar to what the MLTL design gives, about 4.5msec.
PuriMLTL_4ohm_30L_SPL.JPG
PuriMLTL_4ohm_30L_SPL.JPG (49.17 KiB) Viewed 1470 times
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
chris661
Shed dweller
Posts: 2456
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#17 Re: Purifi-based monitor - options

Post by chris661 »

Hi Mark,

Try:
Tools > Output > Horn.

Should give the frequency response of the port only.

Then:
Tools > Particle Velocity > Horn Mouth

I tend to find that drivers optimised towards high output (ie, anything with plenty of excursion) needs attention to air velocities if they're to be used at/near full power. Of course, at a few watts the problem disappears.

Chris
User avatar
IslandPink
Social Sevices have been notified
Posts: 8833
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#18 Re: Purifi-based monitor - options

Post by IslandPink »

Thanks Chris, will try that later.

Been a lovely weekend, and today it's like Christmas again. Nothing like a bit of unboxing where you didn't have to pay for the things yourself !
They seem like quality items - heavy for their size and nicely finished. The cone surrounds are very intriguing.

Image
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
User avatar
IslandPink
Social Sevices have been notified
Posts: 8833
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#19 Re: Purifi-based monitor - options

Post by IslandPink »

I just got these going, leant against the OB's, on the floor, clip leads etc.
Although there's a limited amount you can tell from this , without equalisation, they just sound classy.
You can sit on-axis to them, no crossover, and there's no treble harshness.
The upper midrange part of the vocals is clean and pure, with subtlety.
Straight out of the box they give a spacious room-filling sound even at the low level I'm playing currently.
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
User avatar
IslandPink
Social Sevices have been notified
Posts: 8833
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#20 Re: Purifi-based monitor - options

Post by IslandPink »

I've got one speaker fitted to the 30L sealed box now.
It sounds great. The bass goes quite low , enough to hear a lot more about what these drivers do.
I put on the familiar Ry Cooder 'Boomer's Story' and have nearly played the whole album.
I reckon I can hear slightly more clearly through the mix than with the OBs, on tracks like 'Cherry ball blues' and 'Crow black chicken'.
Each sound seems pure and clean with all its character there as good as I've heard.
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
User avatar
IslandPink
Social Sevices have been notified
Posts: 8833
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#21 Re: Purifi-based monitor - options

Post by IslandPink »

'Swordfishtrombones' sounded excellent.
If the 'fix' for hysteresis in the pole piece makes it work cleanly down to low signal levels, then I can hear that.
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
User avatar
IslandPink
Social Sevices have been notified
Posts: 8833
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#22 Re: Purifi-based monitor - options

Post by IslandPink »

chris661 wrote: Fri Jun 11, 2021 6:20 pm Try:
Tools > Output > Horn.
Should give the frequency response of the port only.
Then:
Tools > Particle Velocity > Horn Mouth

I tend to find that drivers optimised towards high output (ie, anything with plenty of excursion) needs attention to air velocities if they're to be used at/near full power. Of course, at a few watts the problem disappears.
Here it is for 1W ... seems a bit high ... but I have no background on this.
PuriMLTL_4ohm_Velocity.JPG
PuriMLTL_4ohm_Velocity.JPG (45.88 KiB) Viewed 1319 times
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
User avatar
IslandPink
Social Sevices have been notified
Posts: 8833
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#23 Re: Purifi-based monitor - options

Post by IslandPink »

Back with the listening tests. I knew it was time for 'Nuclear Burn', and it was certainly no disappointment.
Now for the rest of the LP.
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
chris661
Shed dweller
Posts: 2456
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#24 Re: Purifi-based monitor - options

Post by chris661 »

IslandPink wrote: Fri Jun 18, 2021 4:58 pm
Here it is for 1W ... seems a bit high ... but I have no background on this.

PuriMLTL_4ohm_Velocity.JPG
For HiFi designs, I try to keep below 17m/s at maximum expected power. Above that, compression starts to kick in, where the port won't "keep up" with the driver as levels increase.

NB - the "expected power level" for a midbass driver at/near the port tuning frequency is very different to that of a subwoofer, which might only have an octave or two of bandwidth. ie, for a subwoofer, a much higher proportion of input signals are at/near the port tuning frequency.

Chris
User avatar
IslandPink
Social Sevices have been notified
Posts: 8833
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#25 Re: Purifi-based monitor - options

Post by IslandPink »

A bit late in saying 'thanks' , but have been mulling over the implications of this.
I have tried a few designs with lower port velocity , but the trade-off so far is definitely more group delay.
I am considering getting having a single test-bed built where we can try at least a couple of options , to hear what is or isn't audible under the conditions that Jon is likely to use them.
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
chris661
Shed dweller
Posts: 2456
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#26 Re: Purifi-based monitor - options

Post by chris661 »

Hi Mark,

I'm a bit surprised that the group delay is changing - I'm assuming you're keeping the tuning frequency the same..?

Personally, I'd prioritise linearity (in terms of output at higher power levels) over group delay, on the grounds that the room is likely to swamp small differences.
I do recognise, though, that we have different approaches to this stuff.

If you do built a test bed to see how these things balance out, I'd be very interested in your results.

All the best,
Chris
User avatar
IslandPink
Social Sevices have been notified
Posts: 8833
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#27 Re: Purifi-based monitor - options

Post by IslandPink »

Simple answer - no, the port tuning isn't that same, I can't see how to enlarge the port area without also having the port tuning go up.
I am encouraged when looking at the plot above a bit more, that the port velocity is really only high at 20Hz. Knowing what music Jon is likely to be playing, and especially when recording/monitoring, I know there won't be much energy below 40Hz. So, I think I will go for the slim port with low tuning first, and see if we can get away with it.
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
chris661
Shed dweller
Posts: 2456
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#28 Re: Purifi-based monitor - options

Post by chris661 »

Making the port longer & wider will maintain the tuning frequency while lowering the air velocity.
However, the port itself can also exhibit resonances, so the hundreds-of-Hz range may end up bumpy. That's one of the tradeoffs.

For example, the 15" subwoofers I use for PA stuff are only really good up to 150Hz, because they use a large port which exhibits its own resonances above 160Hz-ish.
The benefits are obvious for PA duties.

Chris
vinylnvalves
Old Hand
Posts: 501
Joined: Sat Jan 26, 2013 12:08 pm

#29 Re: Purifi-based monitor - options

Post by vinylnvalves »

Troels has done all the hard work for you know regarding how to use this driver :wink:
http://www.troelsgravesen.dk/Purifi-6R.htm
User avatar
IslandPink
Social Sevices have been notified
Posts: 8833
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#30 Re: Purifi-based monitor - options

Post by IslandPink »

Ah thanks Steve, something good to check out after work.
I have made some progress , in that a couple of days ago Jon brought round the 'Serving suggestion' ported box that his made ran up for us.
So we will get a baseline from that, soon.
"Peridots and periwinkle, blue medallions Gilded galleons spilled across the ocean floor" ( Mitchell )
Post Reply