Did anyone ever make a sim of a 520 with a 15" sub below? I would be interested in zhe vertical dispersion pattern if crossed at 800hz.
These are measurements of the T\S parameters of the DeltaLite 2515 driver. The driver is broke in at Xmax on 20hz for one hour. After that I waited one hour and measured the parameters. Maybe someone will find this driver interesting. It requires a slightly bigger box but a very small mms, which is very desirable on crossovers above 700hz.
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In this case, couldn't a throat insert help? The lower minimum of the conical exit section is 18.6 mm (https://www.diyaudio.com/community/...-design-the-easy-way-ath4.338806/post-7766322). Obviously, this would require to fit the throat of the waveguide device to a smaller opening at the conical exit section too.
I don't know, maybe it's worth a try.
This is A460D + BMS4554, adapter v1, roughly 0 - 50° / 10°
The difference between on axis and ~40° off axis:
It could be made basically flat to 20 kHz, I just need to print a different adapter.
- I've printed the same adapter twice, as it's always good to check for random errors. It's the same -
This is A460D + BMS4554, adapter v1, roughly 0 - 50° / 10°
The difference between on axis and ~40° off axis:
It could be made basically flat to 20 kHz, I just need to print a different adapter.
- I've printed the same adapter twice, as it's always good to check for random errors. It's the same -
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Here we go, I forgot I already have one -
0° and 40°:
OK, almost 🙂
Probably not worth the (slightly) more uneven response, but it's still no issue with a DSP.
This is probably as close to an actual 800-20k constant-directivity horn I can get.
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15" should be good for a crossover around 800 - 900 Hz, 12" a bit higher perhaps (in which case the WG could also be made a bit smaller, I guess).
/ High-frequency directivity can be easily shaped just by the choice of an adapter (the bluish part):
I have three versions already and swapping them is a matter of 20 seconds 🙂
/ High-frequency directivity can be easily shaped just by the choice of an adapter (the bluish part):
I have three versions already and swapping them is a matter of 20 seconds 🙂
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It could be used with an 18" as well, after all, if you find a nice one. The waveguide is also 18".
- Maybe with something like 5530ND there would be even more freedom in shaping the response. But I won't buy that one 🙂
- Maybe with something like 5530ND there would be even more freedom in shaping the response. But I won't buy that one 🙂
Note that Faital measures their woofers, or at least their big woofers, centered on a box whose face is one meter square. At the microphone location, this results in a dip slightly below 400 Hz. In other words, I think it's safe to ignore that dip - it's a measurement artifact.
Yep, I didn't find this dip at 18FH500, and the same anomaly is observed in 12FH500 graph, which confirms your note.
These are amazing feats of applied science. My question now is, since you've demonstrated that a completely flat as well as an slightly rising DI is possible (basically any DI slope we desire), what is the (psycho) acoustically) the most desirable? Or is that completely personal preference and is there no theoretical 'best'?
I don't know the answer, that's the reason I still make these different versions. It may be a preference thing to a degree, the problem is that there's no standard, and there have been very few such experiments done, if any. Reports of people building both would be certainly valuable. I haven't done such test myself yet, but I'd like to.
- It seems that we, as listeneres, prefer flat direct sound but not really flat total in-room power (which would lead to a slightly rising DI). But why? Is this independent of loudspeakers used in making the recordings, or is it given by the common radiation pattern used? Would it change if true constant-directivity speakers were used universally from the beginning? Questions that probably nobody knows the answers for. For PA this is different of course.
- It seems that we, as listeneres, prefer flat direct sound but not really flat total in-room power (which would lead to a slightly rising DI). But why? Is this independent of loudspeakers used in making the recordings, or is it given by the common radiation pattern used? Would it change if true constant-directivity speakers were used universally from the beginning? Questions that probably nobody knows the answers for. For PA this is different of course.
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If a technically superior speaker sounds not so good on the current recorded music heritage it will probably not be a hit despite its technical feats. This is the problem with the circle of confusion. The question of how a speaker should be deigned and placed in a room in order to reproduce a perfect illusion of reality is as much a question about the speaker as it is a question on how to record.
Digitally generated sounds and directly connected instruments to mixers do apply as no one could now what the sound - these kind of sounds can only be subjectively judged as sounding more or less nice but not how "real" they sound...
is my view on this...
//
Digitally generated sounds and directly connected instruments to mixers do apply as no one could now what the sound - these kind of sounds can only be subjectively judged as sounding more or less nice but not how "real" they sound...
is my view on this...
//
I think this finding may arise because the controlled blind listening tests we can read about have sought to answer the question of "which available package of loudspeaker characteristics do listeners prefer" rather than "what is the best-sounding approach to loudspeaker design". Imo those are two different questions.
In my opinion, and at the risk of oversimplfying:
A flat power response sounds too bright. And a spectral discrepancy between the direct and reflected sounds is arguably undesirable. Therefore, arguably, the "best approach" would have a gently downwward-sloping power response, AND the direct sound would have the same, or a very similar, gentle downward slope.
In other words, I question the prevailing wisdom of prioritizing a flat direct sound, rather than prioritizing minimizing the spectral discrepancy between the direct and reflected sounds.
In the real world this is easier said than done, which imo is one reason why this type of loudspeaker has (to the best of my knowledge) seldom been included in controlled blind testing.
Unfortunately I doubt the funding will ever be available for a new and more comprehensive round of controlled blind testing, leaving it up to those who can extrapolate and "think outside the box" to push the state of the art. Which imo is what @gedlee did, and what @mabat is now doing.
Hi Mabat,
I'm probably trying to keep up well outside my knowledge level:
The "price to pay" here is the drop at 17k hz?
Which a few posts later you've shown that you can do better with the BMS anyway?
If I'm following correctly the BMS will allow 800 - 20k hz CD in a single driver, the DFM-2535 allows 800ish to 17k hz.
Is there a reason you'd chose the DFM over the BMS then?
This is my very first foray into horns, compression drivers or constant directivity, so I'm definitely a little lost!
Thank you so much for your amazing work here.
Too late to edit post #15,977 so adding this here:
Incidentally, "a gently downwward-sloping power response AND a direct sound with the same, or a very similar, gentle downward slope" is what Earl Geddes was doing twenty-something years ago with the Summa, via his recommended 20-degrees-off-centerline listening axis.
Incidentally, "a gently downwward-sloping power response AND a direct sound with the same, or a very similar, gentle downward slope" is what Earl Geddes was doing twenty-something years ago with the Summa, via his recommended 20-degrees-off-centerline listening axis.
Hi,
here is what I'm after currently, but I haven't reached good profile yet as I keep on doing gradient descent on wrong valleys that don't get perfect lines so posting here for you with better optimization algorithm 😀
I think flat DI is not desired version of constant directivity as it seems to always yield the so called waistbanding, which makes frequency response not flat in listening window. Instead constant directivity in practice is that at least within the listening window frequency response is flat. This means parallel lines on the 2+2 polar graph and results slightly sloping DI which is desirable as per sloping power vs. flat on-axis that's mentioned everywhere. What I'm after perceptually is that being on-axis is not highlighted, this means as wide as possible -1db window without any hint of diffraction and flat response at least to the -3db line, a practical constant directivity.
Here example what I mean. The first image has some mouth edge diffraction making about +/-0.1db ripple on listening window which I do not want to have on ideal waveguide, I want pristine sound in listening window. Yes, why not as cost is the same for this and for the ideal version. The other example has almost no diffraction but is still waist banding a bit, as your new constant DI device.
ps. I have at least three different profiles with very different parameters that all yield different depth device, shallower than A460G2, that can do this kind of practical constant directivity, but would all yield bit different errors mostly with mouth edge diffraction, or waist banding so haven't found the good one o the middle yet.
Beyond this DI think I think shallow waveguide would be ideal in terms of off-axis performance, referring to my previous post with error depending on at which axis the waveguide is rotated and eventually positioned on top of a woofer. Simple goal would be to have max 1/4 wl depth at crossover, but this might be impossible if no diffraction is desired, except if the device has back cover which isn't practical. Also, here I would count directivity to perhaps 60deg very important for aforementioned reasoning and beyond could be bit ragged if necessary (regarding rotating axis) so perhaps the depth isn't that critical as these are quite shallow after all. But, deeper devices really get the edge diffraction out as A460G2 shows by properly waveguiding sound forward and very little gets to the edge. A460G2 performance is ideal in this sense, literally no hint of secondary sounds, ideal. A shallow device can also do this with proper back covering shape, but I havent' been able to make the parallel lines with those.
So if you find this reasonable line of thought please consider optimizing one as your algorithm is way better than mine to weed out the ideal performance, and if it's for 1.4" device I'll buy it 😀
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