sorry I thought I understood the XTB40 reached 1khz how do you get to 4k? maybe I misread what you wrote you are talking about a 3-way system?
Moving from one thing to another but have you read about this THE 28 SUB PRO SQUARED https://www.aia-cinema.com/products/subwoofers/the28-sub-pro-sqaured.html
Thanks! Like I mentioned I do plan to have models focused on very loud home/studio use as well. At least if I find that I have to make any compromises when ensuring that the PA speakers also have best possible power density and SPL.
The last designs for Tectonic, before they stopped making DML, did not use a separate tweeter, and doing that would definitely be a step too far for me. I really want it to be all DML from 100Hz and up to keep the phase diffuse signal. With a regular tweeter I don't think it will blend as well, and you will get the usual projection problems. And IMO with my old design HF reproduction is not an issue, even if it drops of a bit in the top half octave.
Yes, the idea is that the XTB40 will go up quite high. With a first order filter at 4kHz it would not even be down 6dB by 7kHz, and be close to a 50/50 blend with the top plate. But it will remain to be seen where I put the XO. Apart from getting a good curve I also have to consider the power relation. Would be nice if it was enough with one XT25 for the top, and that might mean trying to push up the x-over a bit higher.
The XTB40 is very sensitive below 1kHz, but doesn't drop off dramatically until 8kHz. Using very gentle 6dB/oct filters, the bottom and top plates would work together over several octaves.
The big problem with a typical 3-way system is that you need to have a sharp filter in the middle of the most sensitive part of the hearing. Since I don't need to have the filter as sharp, and can be more flexible where I put the x-overs to move them out of that range, and considering how well multiple DMLs blend, I think it can work. But of course I wont know until I try...at least I hope so 🙂 There are a lot of parameters with materials and sizes, so is hard to know for sure, but I think I will get a feel for if it is worthwhile or not with some experimentation.
sorry leob but you know very well that 4000 hz is the only part where they should never cross, if they cross at that frequency on traditional systems it is for the usual reasons and then they have to deal with the phase, it crosses low and then where it arrives it arrives
And what about the XT19? It has very nice specs. Nobody has mentioned it or tried it yet as far as I know.
I will make an order soon to try them all out, except for the XT19 I think. The XT25 seems to go high enough IMO, and I want the power density. XT19 might be good if you want to make a smaller home/studio system that covers 20kHz though. Could be enough with an XT32 for low plate and XT19 for high.
I agree with everything except the crossing but maybe you're right, trying doesn't hurt, I'm just wondering about XTB40 what's the difference with a normal shaker? then if the plate is free it will start to move it on its axis with a lot of force, even if anchored I have some doubts
Slightly off topic but yes I saw this, 28 Sub pro Squared, and watched a couple of videos on the weekend. Pretty incredible specs and power handling, I did think it seemed similar to a panel speaker with 4 motors. They must have made their own with 22mm xmax and that kind of power (30kw peak) would love to hear one. I wonder if you could make a similar dml version with 4 x XTB40's in a closed box, xmax and output would be far lower but maybe it would play into sub region.
Leob why are you proposing a separate plate for the highs? Would you use a different material, lighter and stiffer material for the highs, and heavier, less-stiff for the lower frequencies?
How would a smaller driver for for the HF work if you put it onto the same panel?
Also, I'm sure you're applying the filter netwrok for the HF driver simply for protection, and not to shape the FR at the "cross-over" point in any way. So if efficiency is lacking, then I assume you'd use 2 x 8r small drivers for a 6db increase in sensitivity?
Here's the link that explains what I think happens at higher frequencies, specifically above coincidence frequency
https://www.acs.psu.edu/drussell/demos/evanescentwaves/evanescentwaves.html
https://www.acs.psu.edu/drussell/demos/evanescentwaves/evanescentwaves.html
Hi Leob,
Did you end up ordering an XTB40 to try? I'm curious but shipping is expensive to NZ so waiting to hear what others think of them as I haven't seen any results.
Did you end up ordering an XTB40 to try? I'm curious but shipping is expensive to NZ so waiting to hear what others think of them as I haven't seen any results.
Hi Leob,
Did you happen to order all the XTB40's in 4ohm for SoundImports?
I had to order a couple or 8ohm ones plus a couple of the XT25-8's. I look forward to trying them together with a first order crossover, as you suggested, around 4khz.
Did you happen to order all the XTB40's in 4ohm for SoundImports?
I had to order a couple or 8ohm ones plus a couple of the XT25-8's. I look forward to trying them together with a first order crossover, as you suggested, around 4khz.
I received a couple of XTB40-8's and some XT25's today, I didn't have much time to play with them but did a quick test on an HD Eps panel I had.
The panel is approx 12mm thick HD EPS 600/400mm, I had tuned it with a couple of weights for the XT32 I had on it. It is suspended in a frame with 30/3mm foam tape around 3/4 of the edge, corners free. Around a 5mm gap to the frame. I removed the weights when I added the XTB40.
The XTB40 definitely falls off above 1khz then very steeply from 7khz. There is good bass to mid 40's but not noticeably more than the XT32 on the same panel, it will be interesting to see if it can handle more power and play louder without strain once I run it with the dsp crossover. The panel needs some work as there is suspension noise when it's turned up and the bass is more extreme.
Below are some quick dirty bench close mic measurements comparing XTB40 with the XT32. I didn't have time to try different positions but will in the future.
I also added the XT25 with a capacitor high pass near the edge to try them together, this is measured on the bench from 250mm. Second screenshot.
I think this could work well with a little tweaking and tuning.
The panel is approx 12mm thick HD EPS 600/400mm, I had tuned it with a couple of weights for the XT32 I had on it. It is suspended in a frame with 30/3mm foam tape around 3/4 of the edge, corners free. Around a 5mm gap to the frame. I removed the weights when I added the XTB40.
The XTB40 definitely falls off above 1khz then very steeply from 7khz. There is good bass to mid 40's but not noticeably more than the XT32 on the same panel, it will be interesting to see if it can handle more power and play louder without strain once I run it with the dsp crossover. The panel needs some work as there is suspension noise when it's turned up and the bass is more extreme.
Below are some quick dirty bench close mic measurements comparing XTB40 with the XT32. I didn't have time to try different positions but will in the future.
I also added the XT25 with a capacitor high pass near the edge to try them together, this is measured on the bench from 250mm. Second screenshot.
I think this could work well with a little tweaking and tuning.
Attachments
Good questions! Yes, the idea was that I can optimize the materials used. I'm not sure if it matters if the HF and LF is mixed physically on the plate as well as acoustically. But seems like using a single plate could work, and not sure if I find a good alternative to EPS that will be more sensitive in HF range. Assuming I do not find something that gives a better HF response than EPS, perhaps using a single plate is the best option.
I got my large format printer set up and tuned, and did test printing a plate from LW-PLA to see if that could be a viable material. I had low hopes, and indeed the results was not very good. I did not bother to do measurements, just tried sticking an exciter on it and comparing to the EPS, and it had a dull sound and low sensitivity. Maybe improvements can be made to printing process and by applying coating, but with such a bad starting point it does not seem worth exploring further.
The filters would be used to ensure maximum power handling overall, which would mean both shaping and protecting. To maximize how hard I can push the HF exciter I would reduce the mid and low a lot. The LF exciter can probably remain unfiltered and I will adjust the HF exciters cross-over to fill in what is missing from the XBT40.
For now though I'm doing one more revision with the 4xXT32 design. I still have a bunch of those exciters and I do think the design works very well if I can iron out some construction kinks. And have to make 16 plates again this year, so probably best to stick to refining the current design more for now 🙂
One reason I have not been able to give this project full focus right now is that I have arranged for a place where we have the festival this year, where I can set up things a bit more permanently and do proper testing since it is very quiet with no neighbours. But printing of the first redesigned plate is under progress now, so hopefully I can report back on how that works out soon.
Not yet, as explained in my previous post. But nice to see that it seems to work out combining the XTB40 and XT25! What's your impression sound wise?
One reflection is that 12mm EPS seems a bit thin, especially for mounting a heavy exciter like the XBT40. I did get some thinner plates, but found 25mm to be a good thickness. Cannot remember exactly how the response differed between the plates though.
Here is print in progress of backplate to hold exciters, cables and speakon connectors:
Designed to print diagonally held up by some supports. Might seem a bit counterintuitive, but makes for stronger more accurate parts.
Designed to print diagonally held up by some supports. Might seem a bit counterintuitive, but makes for stronger more accurate parts.
Hi Leob,
Nice to see you are active on this front again.
I've made a couple of panels now with the XTB40 and XT25 combo, high pass 1st order capacitor around 4khz. They are 600/400mm 20mm thick HD EPS with dilute hide glue and shellac coating. Suspension surrounds are 40/3mm adhesive foam tape all around, will see how the adhesive stands up to use but it is an easy suspension with damping and allows piston motion for the bass to some extent. I'm not sure if it is as good as the clamping in places with EPDM foam I was using for other panels but a lot simpler.
Un Eq'd they sound pretty good and definitely listenable, much stronger in the below 300Hz than others I have made, they fall off pretty steep at 10khz so I need to tweak the XT25, maybe different coating or thin the mounting area more as I have had better HF results on the EPS before with other exciters so know it is possible. I haven't tried to physically Eq these with weights or changing the damping yet.
With DSP I smoothed and boosted the highs plus put a high pass at 80Hz to save the panel as I thought the XTB40 may rip out the poly beads as it has quite a bit more force and weight than other exciters.
Did some quick tests, first is no EQ, second DSP both average of close, 1M and 2M measurements in room. 3rd is comparison moving mic 1m no eq vs DSP.
They have a lot more punch than other panels I've made and solid output to 60Hz they play loud too but haven't pushed them too much without a high pass. Moderate volume they sound good without a sub.
These will be my party panels probably, with a sub. I have a little BRU5 amp that has inbuilt DSP so makes it fairly portable.
