Radiation resistance changes, but on the other hand it has gone wide by then so it has to do a lot to maintain it.
I have a pair of BMS 4554s, which is a 4550 with 1.4" exit, and I've listened to the HF108 on several horns.
'Sound quality' is a matter of taste/preference, but for hifi I'd prefer the HF108.
The BMS can sound a bit hard, aspecially with vocals and when crossed low.
I may be a bit more sensitive to materials than others, but to me the HF108 sounds more like a paper cone, whereas the BMS reminds me of Polypropylene mids.
Of course, Fluid is correct about horn loading and therefore I'd use the ST280E when a low crossover point is desired.
It's about the throat resistance, indicated by the red ellipses.
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I think we've been here before, when Dr Geddes replied to your statement...
https://www.diyaudio.com/community/...w-distortion-with-a-2-way.334757/post-5937945
I'll stick with classical theory and my primary objective: efficiency (= less strain) 😉
Why would compression drivers behind shallow waveguides give up the ghost (long) before the same drivers connected to deeper horns, when pushed hard using the same (low) crossover freq.? Dr. Geddes experienced this firsthand with some of his speakers used in clubs.
"You would also think that increasing the output would be one aspect of horns, but this is included in both. Increasing the loading of the driver over that of free air increases efficiency and hence the output, and concentrating the sound into a certain solid angle increases the output further.
Loading of the Driver.
The loudspeaker, which is a generator of pressure, has an internal source impedance and drives an external load impedance. The air is the ultimate load, and the impedance of air is low, because of its low density. The source impedance of any loudspeaker, on the other hand, is high, so there will be a considerable mismatch between the source and the load. The result is that most of the energy put into a direct radiating loudspeaker will not reach the air, but will be converted to heat in the voice coil and mechanical resistances in the unit. The problem is worse at low frequencies, where the size of the source will be small compared to a wavelength and the source will merely push the medium away."
Why would compression drivers behind shallow waveguides give up the ghost (long) before the same drivers connected to deeper horns, when pushed hard using the same (low) crossover freq.? Dr. Geddes experienced this firsthand with some of his speakers used in clubs.
"You would also think that increasing the output would be one aspect of horns, but this is included in both. Increasing the loading of the driver over that of free air increases efficiency and hence the output, and concentrating the sound into a certain solid angle increases the output further.
Loading of the Driver.
The loudspeaker, which is a generator of pressure, has an internal source impedance and drives an external load impedance. The air is the ultimate load, and the impedance of air is low, because of its low density. The source impedance of any loudspeaker, on the other hand, is high, so there will be a considerable mismatch between the source and the load. The result is that most of the energy put into a direct radiating loudspeaker will not reach the air, but will be converted to heat in the voice coil and mechanical resistances in the unit. The problem is worse at low frequencies, where the size of the source will be small compared to a wavelength and the source will merely push the medium away."
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In the first image, it's clear that the waveguide is 'fully' loading the driver around 2 kHz. Ideally, you should not use this wg below ca. 1200-1500 Hz.
It still seems like a semantic argument over terms, I tried to avoid using the word "loading" as it is the increased Radiation Impedance that is giving the increased output lower down which is what would be helpful to the OP if he wants to cross low.
I had no coment about my naive try to low pass the 12pr320. So I surmise it is too much bad or unusefull as a choice factor (break-up trade off and cut off).
On an empirical side, following the good link given here, most users prefer to cut off the BMS 1" a little higher mini 1100 to 1200 hz for a more balanced sound. https://www.diyaudio.com/community/threads/best-compression-drivers-today-2022.382609/post-7172205
https://www.diyaudio.com/community/threads/your-favorite-1-cd-for-1-5khz-and-up.337608/post-5783977
https://www.diyaudio.com/community/threads/best-compression-drivers-today-2022.382609/post-7173516
So, while the BMS4550 has an acceptable THD from 900 hz for hifi use, some still find that cut-off a little hazardous causee the 1.75" diag Sd too much stressed that low.
Pushing further the reading to try to make the best choice between my wallet short deepness and curiosity about a modern design with controlled directivity but still good sound (thd?) I looked at a close Faital reference that exhibits a little high thd odd harmonics level... Also considering Dual Triode input filler between the horn and the 12" like a 8" or 6". (second hand JBL are rare in my country because higly rated and a 10'
" off axis above 1500hz is an off axis trade off perhaps https://www.diyaudio.com/community/threads/best-compression-drivers-today-2022.382609/post-7173412)
Thd of the close 12PR300 predecessor https://5e8772ee-a-62cb3a1a-s-sites...pEN3DTfe38164pVr-qPDbNK_YPHdDu&attredirects=0
From https://sites.google.com/site/drive...558se/faitalpro-12pr300/non-linear-distortion
The two ways passive with high cut off is attractive cause less parts less monney and the high cut off reduce the expensive passive filter parts. But as some stay, too much trade offs equals not good enough equals too much expensive for what it is (Buy once cry once ?).
What Humblehomemadehifi hifi or Gravsen does not present is a more 3Ways classic but with horn from 1200 hz or above in spite off the classic dome ?
On an empirical side, following the good link given here, most users prefer to cut off the BMS 1" a little higher mini 1100 to 1200 hz for a more balanced sound. https://www.diyaudio.com/community/threads/best-compression-drivers-today-2022.382609/post-7172205
https://www.diyaudio.com/community/threads/your-favorite-1-cd-for-1-5khz-and-up.337608/post-5783977
https://www.diyaudio.com/community/threads/best-compression-drivers-today-2022.382609/post-7173516
So, while the BMS4550 has an acceptable THD from 900 hz for hifi use, some still find that cut-off a little hazardous causee the 1.75" diag Sd too much stressed that low.
Pushing further the reading to try to make the best choice between my wallet short deepness and curiosity about a modern design with controlled directivity but still good sound (thd?) I looked at a close Faital reference that exhibits a little high thd odd harmonics level... Also considering Dual Triode input filler between the horn and the 12" like a 8" or 6". (second hand JBL are rare in my country because higly rated and a 10'
" off axis above 1500hz is an off axis trade off perhaps https://www.diyaudio.com/community/threads/best-compression-drivers-today-2022.382609/post-7173412)
Thd of the close 12PR300 predecessor https://5e8772ee-a-62cb3a1a-s-sites...pEN3DTfe38164pVr-qPDbNK_YPHdDu&attredirects=0
From https://sites.google.com/site/drive...558se/faitalpro-12pr300/non-linear-distortion
The two ways passive with high cut off is attractive cause less parts less monney and the high cut off reduce the expensive passive filter parts. But as some stay, too much trade offs equals not good enough equals too much expensive for what it is (Buy once cry once ?).
What Humblehomemadehifi hifi or Gravsen does not present is a more 3Ways classic but with horn from 1200 hz or above in spite off the classic dome ?
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Hello,
For a cone driver the angle of coverage is a function of the circumference of the piston vs the frequency, a linear sort of thing. However octaves are a frequency doubling sort of thing.
As seen in fluid's post above the directivity of a given cone driver increases at a accelerating (steeper) rate as the crossover frequency increases.
If we have a constant dispersion wave guide there will always be a dogleg in the directivity curve at the crossover frequency. Crossover slopes will add additional complexity. Smooth directivity is not going to happen without lowering the crossover frequency away from the steep part of the piston driver directivity curve.
Crossovers at higher frequencies and smaller coverage angles will only make the dogleg worse.
Thanks DT
The B&C DE250 has a 1.7" diaphragm and is used lower than 900Hz on a regular waveguide with no problem.
....often we read: try to make the things less worse where the ears are the most sensible....1k to 3k hz.
Dr Earl Gedlles is for 500 hz cut off max as an ideal while I think it was certainly for the 15" model. I do not know where he finished withe 12" models...
Dr Earl Gedlles is for 500 hz cut off max as an ideal while I think it was certainly for the 15" model. I do not know where he finished withe 12" models...
The data from the OSMC has a difficult to deal with dip, I don't see this being as bad in every measurement like this one of the mezzo Calpamos, so you have to decide how much validity you want to put into a basic sim using someone else's measurements unless you plan to copy exactly what they did.
I understand the desire to seek other people's opinions but you have to consider the circumstances under which they were formed. Would their opinion be different if they had used a different woofer, a different waveguide or a different crossover. If you try hard enough you can always find someone who doesn't like something for some reason 🙂
I can not agree more, I know that is not a good methodology. I try to sort out that because I can not afford the experience myself, nore several iteration and at least has an ethic problem to collecting goods that stay on a shelf nowadays. But well I am optimist. I have not calm environment to test the woofer at 2m from the ground outside.So nicely shared third party measurements help more than not in my situation.
Sure there is a limitt to use else measurements. An impulse response should be good enough but seems it is maybe not due to testing environment.
First there can be unit dispesrion, not ruled difraction and so on when testing the cab combo and sim have limits as sim tools. The most difficult to trust are third party T&S... I never see two people showing a close measurement of a same unit.
If you see 3 close design with the load of the 12pr320, OSMC, T gravsen, T. Gee. None has the same average dB level between 100 hz and their cut off, even liters load and BR vary, be it a choice by design or else. Not easy to be sure and very less easy to do it as good alone. 90 db to 93db average between the three designs. So you really want to know what to do... and advance carrefuly when a noob 🙂.
Sure there is a limitt to use else measurements. An impulse response should be good enough but seems it is maybe not due to testing environment.
First there can be unit dispesrion, not ruled difraction and so on when testing the cab combo and sim have limits as sim tools. The most difficult to trust are third party T&S... I never see two people showing a close measurement of a same unit.
If you see 3 close design with the load of the 12pr320, OSMC, T gravsen, T. Gee. None has the same average dB level between 100 hz and their cut off, even liters load and BR vary, be it a choice by design or else. Not easy to be sure and very less easy to do it as good alone. 90 db to 93db average between the three designs. So you really want to know what to do... and advance carrefuly when a noob 🙂.
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At some point you'll have to decide which compression driver to get (and what horn to pair it with).
But if you have a computer with a 2 channel soundcard and a stereo amp, there's nothing stopping you from trying different configurations before committing to a certain crossover, should you desire to have a passive solution in the end. You can try a few things and make up your mind with quick active tweaks, if you get what you like, for instance: you've found the right crossover frequency, you can work (with Vituix) to re-create it with passive means.
But if you have a computer with a 2 channel soundcard and a stereo amp, there's nothing stopping you from trying different configurations before committing to a certain crossover, should you desire to have a passive solution in the end. You can try a few things and make up your mind with quick active tweaks, if you get what you like, for instance: you've found the right crossover frequency, you can work (with Vituix) to re-create it with passive means.
I have the two channels EMU soundcard and the wires, the arta box, Vituix, Arta, and Rew, the calibrated mic with the phantom supply, two faital 12pr320 not breaked in. I assume an impulse response to have a first spl and impedance without breaking in before is useless ?
For some reasons I certainly test the upper range before I am free enough to make the cab and test again the 12pr320 in it.
In between, yeah, I have the strong feeling than I should invest time to learn active for designing the filter prototype, at least I know the theory already
On a fire and forgett point of view, maybe a 2 ways genelec with a 5 +1 and an active sub, should be better sound wize and perhaps for the walett too... less fun and learning though.
For some reasons I certainly test the upper range before I am free enough to make the cab and test again the 12pr320 in it.
In between, yeah, I have the strong feeling than I should invest time to learn active for designing the filter prototype, at least I know the theory already
On a fire and forgett point of view, maybe a 2 ways genelec with a 5 +1 and an active sub, should be better sound wize and perhaps for the walett too... less fun and learning though.
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You can easily make reasonable measurements at home without a huge amount of space. Any ordinary room with the driver half way between the floor and ceiling will work. The gating time will determine how much resolution there is in the lower midrange. A nearfield and baffle diffraction simulation is accurate enough for the response in the low hundreds of Hz down in most cases.
The shape and size of the baffle and driver placement will matter, this can be simulated in Vituix to get an idea of what the baffle will add or subtract.
You can relax the suspension on a driver by carefully playing 10Hz tones through it, you won't hear them but they will get the suspension moving with enough voltage. But be careful as you could also destroy it too. There is no need to have the thing blaring at 100dB for 80 hours or some other nonsense like that.
I get that it is hard but start by using the right tools that you already have to begin working this out.
Unless you can listen to other peoples systems to get an idea of what you like and don't like about them then it will be an educated guess at best. In that case look for drivers and combinations that are flexible, that way you can continue to work on the speaker and modify it if you find something about it you don't like or think can be improved.
Wesayso is a great example of building one speaker and working on it over time to make it what he wants.