Those specific measurements were not done at a normal listening distance. The distance was very close and they were mounted close to a table in a vice. They were specifically made only with the purpose of having a consistent mounting method such that I could measure the difference between the drivers i.e. the driver consistency.
When I have measured normally then they perform close enough to PEs measurements that I'd say they are accurate.
Much interest in these planars in recent times. Why? New materials? New designs? Audio systems re-thinking? DSP? New publicity?
(I've added planar tweeters recently. Exceptional test and listening results.)
B.
Thanks!
Part of it might be supply chain woes. P-E actually has these in stock. Plus while I am pretty new to audio DIY, it seems like alternative speaker designs have just become more popular recently. I'm not even sure how or why I got into DML speakers for example, but it was within the last 2 years. I think the Ali Express exciters I got are relatively new to the market.
These planars seem to have a lot of the strengths of DMLs (broad frequency response, easy mounting, dipole dispersion with good off-axis response) with less of the downsides (frequency responses that don't need extreme EQ to correct, or possibly any correction at all). All for not much more money than a decent exciter.
No other planar I know of has even been close to the GRS in performance * consistency / price for a long time. And on top of that they are available in large numbers.
There are specific drivers that have the performance, but cost have skyrocketed the last few years. The GRS line opens doors to play with planars without breaking the bank.
the sensativity of planers like this in actual use is typically around 87-89 db IF u are using them below about 500 hz
Ok, I got a PT-2522C here that I’m planning to retrofit into a center channel. Does the tweeter have wide horizontal dispersion and narrow vertical? It looks like it’d be easier for me to mount if I put it sideways, but I assume that would not work for this tweeter. Some modification of the existing box is required and I’m not looking forward to that!
I’m sure I have other issues, but I’d better save that for another thread...
Regarding the question of “why are these GRS drivers getting attention”, they seem pretty affordable for planar speakers. I gave it a quick listen, and it sounded good to me. Can’t wait to put it all together, but I’ll have to wait.
Does this need a strict 2nd order filter, or will a first order work, as long as the roll off starts high enough?
I’m sure I have other issues, but I’d better save that for another thread...
Regarding the question of “why are these GRS drivers getting attention”, they seem pretty affordable for planar speakers. I gave it a quick listen, and it sounded good to me. Can’t wait to put it all together, but I’ll have to wait.
Does this need a strict 2nd order filter, or will a first order work, as long as the roll off starts high enough?
Not sure about increased interest in planars in general, but these GRS ones are near clones (different material) of the Bohlender Graebener planars. Those have been highly regarded for many years and are on many peoples' short list of favorite tweeter, but the BG Neo3 is now $96 and the GRS 3 1/2" is $33.
The felt damping is different in the horizontal/vertical directions, but this is more likely to influence the higher frequencies.
The vertical directivity of this one won't be as strong as you'd see with longer ribbons/planars, since this one is nearly square.
Is there a way you can mock it up without modifying the enclosure? I find it helpful to get something I can listen to first to figure out if it's worth the trouble to do the real build. If you can throw something together to test the orientation issue and overall performance, it should help you pick some directions.
On the open-back version, distortion performance is good to about 2 kHz, and tolerable to 1 kHz (depending on your views), but rises rapidly below 1 kHz. The closed-back is probably similar in that regard, but I haven't tested it so can't say for sure. If their distortion profile is similar, you'll need a pretty high first-order crossover to get high performance, but it's possible.
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Hmm, OK, it's worth it for me to try again. I did listen to it hand-held while hooked up to the old crossover, and it did seem to fall off a bit, off-axis, but hard to tell. It still needs some modification to fit sideways, but it's MUCH better if I can make that work.
I agree. I did connect it to the old crossover (crossed over really high for the old tweeter), to get an idea of how it sounds and to see if I needed to dampen the tweeter. I was thinking of crossing it more like 4000 for this tweeter, if using 1st order, but it would still have some output below 2000Hz.
I had to hand-hold it kind-of in place, but it sounded pretty good. It was a bit loud relative to the woofers, which I kind of expected, so I also added a 2ohm series resistor, and it matched pretty well! I'm doubly-excited to try it, now that I've heard it.
(Using my hand-held SPL meter, using the 2ohm resistor seemed to match the volume, but this was really hard to tell like this. I should use REW, but it's just in too much of an ad-hoc state to do that and get meaningful results anyway.) Worst-case, I'll have to re-work the crossover a 2nd time if what I have planned is too far off from reality, but seems like this is worth trying, for sure.You seem more concerned about audio quality, and I 'm more concerned about it getting cooked by playing too low! Not that I don't want high quality sound, just that I'm less concerned about audibility below 2000Hz as the tweeter falls off below that anyway. From my modeling, it wouldn't be an issue by the time it hits 1000hz, I would think, as it would be something like 25db down by then.
The specs on the closed-back version do not go as low as the open-backed one (1,800 to 20,000Hz, on Parts-Express). (I would prefer to have the open one under normal circumstances, but since this is going into a center-channel under the TV, the closed one makes more sense.) Below 1800, it rolls off, which explains why they use that range.
I use a lot of masking tape and Fome-cor for early prototypes. You can get away with a pretty shoddy mock-up for higher frequency drivers and many dipole baffles.
That sounds like a good idea. That would make it easy to measure the drivers, if you had a big enough surface area.
In my case, I also want to change the crossover, so that's going to alter the sound as well. Should be for the better, as the old crossover used electrolytic caps.
But I've heard enough to make me want to continue. I tried listening closer to the off-axis response, vertical and horizontal, and I can't tell an obvious difference. There's fall-off both ways. I'm sure there's some difference, and that felt has to be there for a good reason, but I dunno - I'm going to go for it. Going horizontal with it means more modest cuts to the enclosure, and a clean look. I don't want to spend too much time screwing up the enclosure, as I have a lot of work to do re-doing the crossover. I'll have to save that for this weekend. Thanks for your comments.
I made a separate thread so I don't feel guilty about derailing this one, but the GRS tweeter project worked great. Fitment required some modification and the front baffle doesn't fit quite right, but it's OK. Frequency response turned out really good except for a dip at 8khz. Not sure what that's from, as it's well above the crossover point.
This dip is inherent (part of) the PT2522 response. The radiating surface is only about 1/3rd of the width of the tweeter, and this likely causes diffraction/interference that results in the on-axis dip at 8kHz. It is similar to a driver in a open baffle that is more than about twice the radiating area of the driver. The response problem at 8kHz is well known, and identical to the B&G Neo3 response. The GRS tweeter is a 100% copy of the B&G model. Off axis the dip flattens out, so don't worry about it.