Hi all,
I'm thinking of playing around with an open baffle monitor using these drivers:
1 x GRS PT6816-8
2 x GRS 10PT-8 (parallel, did two of them for the excursion and sensitivity to bring it up)
Just fooling around in X-sim to see if they're even remotely compatible in a meaningful way without requiring super complex passive crossover. But, I'm very weak with crossover design and mostly use full range drivers. So any help is appreciated if anyone has a moment!
I tossed in the drivers in X-sim and did a simple set of low pass and high pass to get a general idea of things and how the impedance would be.
I don't need it to be super flat. I mostly just want to get to about 70~80hz on the low end before I crossover to a sub. I imagine I will do this on the thinnest baffle I can and will add some wings assymetrically to the sides, then measure, then re-do the crossover. So this is more of a preliminary attempt to see if they will even work together passably. I have the PT6816 drivers, but I do not have woofers yet, so I'm open to something superior for the role in a similar price range (~$30 per driver).
I've attached my X-sim model here to this post so it can be loaded with the drivers.
Thanks!
Very best,
I'm thinking of playing around with an open baffle monitor using these drivers:
1 x GRS PT6816-8
2 x GRS 10PT-8 (parallel, did two of them for the excursion and sensitivity to bring it up)
Just fooling around in X-sim to see if they're even remotely compatible in a meaningful way without requiring super complex passive crossover. But, I'm very weak with crossover design and mostly use full range drivers. So any help is appreciated if anyone has a moment!
I tossed in the drivers in X-sim and did a simple set of low pass and high pass to get a general idea of things and how the impedance would be.
I don't need it to be super flat. I mostly just want to get to about 70~80hz on the low end before I crossover to a sub. I imagine I will do this on the thinnest baffle I can and will add some wings assymetrically to the sides, then measure, then re-do the crossover. So this is more of a preliminary attempt to see if they will even work together passably. I have the PT6816 drivers, but I do not have woofers yet, so I'm open to something superior for the role in a similar price range (~$30 per driver).
I've attached my X-sim model here to this post so it can be loaded with the drivers.
Thanks!
Very best,
Thanks, true, its mid-way Qts. Was hoping two of them might do the job with high sensitivity and 7mm excursion. Guess not?
The GRS 10PF-8 is only 88db sensitive, 3mm excursion, high Qts. If two of those would be better, that can work too. I think the excursion was throwing me from being interested on an open baffle. But if they're only going down to 80hz or so, I guess that doesn't matter.
Yea, even at 2mm excursion, this is plenty loud in a normal sized room to 80hz. I guess I could try those. They're just lower sensitivity and will need to pad the mid-tweeter some.
Will try again.
Very best,
Basta sim of a pair of these on a 30cm wide baffle suggests you can easily get a -6dB of 70 Hz, with passband sensitivity of 90 dB at 1m for 2.83V. Simple inductor (4 mH maybe) and cap will do it. A bit more crossover work might pay dividends though.
Thanks, interesting, I'll try a few more options in Basta to see what works. I'd overall like to get close to 70~80hz usable output on the low end. Keep the tweeter-mid up top with no wings, skinny baffle, and then lower baffle for the 10's can be wider of course and have longer depth wings to help get more baffle width. I'd like to manage an acceptable curve via passive crossover, but happy to then actively DSP it for final results in room(s). I could go all active and forget all this, but I do need to learn more about crossover application and design since its my weak point.
Very best,
Here's a Basta sim of two of the GRS 10PF-8's I linked above on a meter wide baffle (intention is to do a 12" front baffle and fold the sides/wings to get to about a meter). Do you think this is worth considering? It looks ok to me, but needs work to be "good" of course.
Very best,
Well, personally I'd stick with the the 10PT. I don't see the Qts of around 0.5 as a problem for OB, even with a passive crossover. That's the point I was making above. If you go for the 10PF, the higher Qts means it wants to roll off lower, near Fs. But with limited Xmax, what's the max power you can give it? Not much, I'd bet. Basta will tell you, if you show the MOL curve.
With wings, you need to watch that you don't create a cavity resonance problem, especially when you want to use them up into the midrange. (The 10PT can give you good sensitivity just on a 30cm baffle, Basta suggests, so you shouldn't really need wings.)
With wings, you need to watch that you don't create a cavity resonance problem, especially when you want to use them up into the midrange. (The 10PT can give you good sensitivity just on a 30cm baffle, Basta suggests, so you shouldn't really need wings.)
Thanks,
One thing to note, the published Qts of 0.5 is just that, GRS often measures with more Qts in reality, I have lots of their drivers and they always higher Qts, so maybe its something to not worry over as you mention.
That loss in excursion I feel might hurt. Double excursion means more SPL which means more than the roll off.
Good point on the cavity, I am currently working on a slot loaded open baffle sub that has cavities and so I know for sure I don't want that happening on the back of the open baffle monitor. If I do create one, the cavity will need to be huge so that the cavity resonance is pushed to a lower frequency.
So, if staying with the 10PT-8, that takes me back to the crossover above in initial post. Any suggestions there? The saved file is attached if you need it.
Thanks!
Very best,
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New X-sim using the GRS 10PT again.
I think this will allow me baffle step compensation for the upper range, so the lower range is higher level so it will even out with a baffle step. In theory.
I like the response graph.
I do not like the impedance graph lol. I pushed it below 3ohm in a few spots. Sigh. Can't use that. Any suggestions from anyone?
Attached the X-sim file if anyone wants to play with it.
Basta:
I can't get a graph like the previous one (here). Is there a filter enabled I'm not seeing?
Edit: Oh duh, it was the low pass filter enabled. Hur dur.
Very best,
I think this will allow me baffle step compensation for the upper range, so the lower range is higher level so it will even out with a baffle step. In theory.
I like the response graph.
I do not like the impedance graph lol. I pushed it below 3ohm in a few spots. Sigh. Can't use that. Any suggestions from anyone?
Attached the X-sim file if anyone wants to play with it.
Basta:
I can't get a graph like the previous one (here). Is there a filter enabled I'm not seeing?
Edit: Oh duh, it was the low pass filter enabled. Hur dur.
Very best,
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Here's another option.
Using 4 x GRS 6PT-8 (6.5 inch drivers, 4.2mm excursion each)
Closer to 4ohm finally.
This could be built into a slot loaded open baffle for the 4 woofers too, to get a better curve response down low. Then I just need to deal with cavity resonance. Maybe. Or can just do 4 woofers on the face with none of that. Not sure what I'd want to do for the sake of how it looks.
Also attached for tinkering.
Very best,
Using 4 x GRS 6PT-8 (6.5 inch drivers, 4.2mm excursion each)
Closer to 4ohm finally.
This could be built into a slot loaded open baffle for the 4 woofers too, to get a better curve response down low. Then I just need to deal with cavity resonance. Maybe. Or can just do 4 woofers on the face with none of that. Not sure what I'd want to do for the sake of how it looks.
Also attached for tinkering.
Very best,
Slot loading will induce a steep low pass filter at the 1/4 wavelength equal to the depth of the slot……for 6.5” woofers that’s around 440hz. I don’t think that will work for you for a 2 way.
You can’t really use a driver up through the mids with a wide baffle for low end support……you’ll amplify the dipoke peak so much that it will take quite a few components to beat it down.
I’d say you’d be just fine IF you targeted an F3 of around 100hz instead…..let the subs take over from there…..just keep em close. Then you could look at woofers with a qts around .5 or so.
If 100 hz works for the F3 and 1200hz XO to the slim, the GRS 12 will get ya there on the cheap…..the top end break up is not great but manageable
You can’t really use a driver up through the mids with a wide baffle for low end support……you’ll amplify the dipoke peak so much that it will take quite a few components to beat it down.
I’d say you’d be just fine IF you targeted an F3 of around 100hz instead…..let the subs take over from there…..just keep em close. Then you could look at woofers with a qts around .5 or so.
If 100 hz works for the F3 and 1200hz XO to the slim, the GRS 12 will get ya there on the cheap…..the top end break up is not great but manageable
Thanks, I've seen builds that use the slot loading successfully, they do have to deal with the cavity resonance. That may indeed be more than I'm shooting for. As I understand it, if I make the cavity area large enough the resonant peak frequency will be lower. If I can get it to be low enough, it won't matter. But then again I won't benefit the slot load anymore either. So might as well just face mount the drivers. I mostly like slot loading for compact and opposed alignment for folding a baffle up and reducing its max gross dimensions.
I would really like to try to get to 70~80hz as the F3 range. I can do 100hz with a single full range driver as it is and have done this already (8" full range, Visaton). With this planar tweeter-mid, and two 10's, I would hope I can push a little to get to 70~80hz. Just enough to get that last little bit in vocal range from the drivers so my sub isn't producing natural male voice (at least typical male voice). Maybe this isn't possible with these drivers.
I'm happy to entertain other drivers if it will let me get closer to that without too much complication. Any suggestions?
Very best,
The resonance is secondary.....that's easily handled......it's the acoustic high pass filter that will be 3rd order that matters......for a slot depth of 6.5", that will be roughly 440hz so by the time you're at 1.2k, the signal from your OB slot loaded woofers will be down around 30db......this won't work for a cross to the PT slim
Thanks, I'll probably just see if I can do it with the two 10's or two 12's then. No slot.
I just want to try for the best option up front. Ultimately, I will measure them in the baffle and build the crossover based on that. Don't mind some trial and error. Just don't want a $150 crossover for a $30 driver lol.
I need to learn more about this:
I really don't know where this even goes in the circuit lol, or if it even works as intended or if its just theory stuff and nukes output.
I'm used to active DSP, but haven't done this with a passive.
Very best,
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