Upgrade: SAM1HF or 2452H-SL in ScreenArray horn?

[pos]

Very interesting, thank you Gibber!
You should try truextent diaphragms if you can: these are a real pleasure to measure and listen to

[ivica]

Very interesting, thank you Gibber!
You should try truextent diaphragms if you can: these are a real pleasure to measure and listen to

Hi Pos,
In comparison aluminum D16R2441 and truextent-Be, I understand that you prefer Be diaphragm, is it??
Have you tried, Radian 4" aluminum to compare with others?
My Regards
Ivica

[pos]

Hi Ivica

No, sorry if my comment could me misleading: I did not compare the Be to any Al diaphragm directly: I only compared side by side the tuextent Be, JBL Ti ribbed, and JBL Ti SL...

Here is a comparison between the truextent and the radian:
http://materion.com/~/media/Files/PD..._Vs_Radian.pdf

In my comparisons I found the ringing of the ribbed Ti in the UHF (due to breakups) quite audible (once you put your finger on it).
Looking at these measurements it looks like the Radian also suffer from this type of breakups/ringings...

[4313B]

The back cap seems to have no influence in this case (both caps actually offer quite generous volume compared to what's available in 2435HPL).

Impedance curves?

[gibber]

Impedance curves?

The B&K stuff i use to run my acoustic measurements from Arta cost a ton, but sorry, don't have any hardware to do imp plots.
I do Q measurements on cone drivers by hand, but that's just three points on a single impedance peak. Arta doesn't seem to offer imp plots

Your recommendation?

[gibber]

Very interesting, thank you Gibber!
You should try truextent diaphragms if you can: these are a real pleasure to measure and listen to

If you have some for me to try, i am happy to give them a go
According to rumour i heard, they're no longer available after loss of their Be foil supplier. Rumour true or not? -- definitely haven't seen them on offer any more for a while. In any case i was not super-impressed with the Be drivers i have run in my setup so far (JA801 with modded Jabo, TD4002(Z)/2435/TD4001 on various horns), so i missed out on Truextent volontarily when they were still easy to get.

[gibber]

Nice and instructive work. Do you have less-smoothed response (say 1/24), even that aluminum diaphragm (in 2441 standard D16r2441, with 'diamond'-metal suspension) in your experiment used, is may be good damping itself.

Here you go, Ivica - i doubled resolution of the pic also



==> this is on the same HR9040A horn, and the periodic behaviour (every 190Hz) i attribute to the distance either between horn and mic or more likely, distance between (upwards aiming) horn and my 2.5m heigh ceiling. The driver is placed on the floor during measurement. The arrangement allows me to put horns on drivers fast, while the horn mass in combination with the gasket most drivers have still provide good if not perfect sealing ...

Mentioned loss around 3kHz can be seen on Mr. Keele original work while presenting HR9040 horn).
For me, it is interesting that you heave no beep notch behavior about 10kHz, that is visible on the Mr. Keele measurements

The HR9040 is a slot radiator type horn with 33mm entrance height that is squeezed down to just 18mm vertical size at the point where the slot opens into the radial section.
The HR9040A opens up from 33mm at throat entrance to 38mm vertical where the radial section begins. 38mm is more than double of 18mm.
Both horns expand towards the mouth following almost exactly the same horizontal formula.

As a result, we have two very different horns, even if the most visible part of them (the super-large mouth) is exactly the same and the horizontal shaping is almost the same. Because of slower area expansion in HR9040, the lower cutoff strongly differs, and the "slot" of HR9040 (Keele used it in the JBL bi-radials again, but turned vertical) will surely make for a very different high frequency behaviour.

Not sure the dip in your post of Keele's HR9040 plot is due to either "pipe effect loss" or diffraction, but it strikes me that speed of sound divided by 0.018m slot size is 19kHz, and the response anomaly is at half that frequency.

[Mr. Widget]

If you have some for me to try, i am happy to give them a go
According to rumour i heard, they're no longer available after loss of their Be foil supplier. Rumour true or not? -- definitely haven't seen them on offer any more for a while. In any case i was not super-impressed with the Be drivers i have run in my setup so far (JA801 with modded Jabo, TD4002(Z)/2435/TD4001 on various horns), so i missed out on Truextent volontarily when they were still easy to get.

Truextent couldn't have lost their supplier... they are one of the few companies in the world that actually mines Be ore.

In any event they are back in production and available.


Widget

[ivica]

Here you go, Ivica - i doubled resolution of the pic also

==> this is on the same HR9040A horn, and the periodic behavior (every 190Hz) i attribute to the distance either between horn and mic or more likely, distance between (upwards aiming) horn and my 2.5m height ceiling. The driver is placed on the floor during measurement. The arrangement allows me to put horns on drivers fast, while the horn mass in combination with the gasket most drivers have still provide good if not perfect sealing ...

The HR9040 is a slot radiator type horn with 33mm entrance height that is squeezed down to just 18mm vertical size at the point where the slot opens into the radial section.
The HR9040A opens up from 33mm at throat entrance to 38mm vertical where the radial section begins. 38mm is more than double of 18mm.
Both horns expand towards the mouth following almost exactly the same horizontal formula.

As a result, we have two very different horns, even if the most visible part of them (the super-large mouth) is exactly the same and the horizontal shaping is almost the same. Because of slower area expansion in HR9040, the lower cutoff strongly differs, and the "slot" of HR9040 (Keele used it in the JBL bi-radials again, but turned vertical) will surely make for a very different high frequency behaviour.

Not sure the dip in your post of Keele's HR9040 plot is due to either "pipe effect loss" or diffraction, but it strikes me that speed of sound divided by 0.018m slot size is 19kHz, and the response anomaly is at half that frequency.

Hello Gibber,

Thanks for the explanation the differences between HR9040 to HR9040A horns, and the measurements 2447 driver ( I understand with D16R2441 ALUMINUM dome) in HR9040A horn.

My expectation of 9kHz deep notch (loss) in Mr. Keele measurements (that are definitely not present in your precise work 1/24 smoothing). I can understand that in such way: if the sound is passing 'between" two parallel plates, that are D apart, then the first notch would be expected around f= Co/(2*D), so for 18mm=0.018m expectable f[18]= 9580Hz, and if D=38mm, f[38]=4540Hz, but in your measurements none of the mentioned frequencies are visible as notches.

Regards
Ivica

[gibber]

Truextent couldn't have lost their supplier... they are one of the few companies in the world that actually mines Be ore.

In any event they are back in production and available.


Widget

Widget

thanks for the info,
do Trueextent mine Be and do the foils or just mine Be and have Be end user products ?
That would be interesting to know, as i heard from a French speaker designer there are only two Be foil companies ww, so Truextent might have the whole value chain in-house.

Sad i never saw the offer Altec large format drop-in replacements. Talking about drop-in of diaphragms (and this may or may not warrant another thread), does anyone know the meaning of JBL's magic numbers ? Here's a few shots:






The "+1" fram came from the "-3" driver which looked like never opened (but i bought it 2nd hand...)

[gibber]

if the sound is passing 'between" two parallel plates, that are D apart, then the first notch would be expected around f= Co/(2*D), so for 18mm=0.018m expectable f[18]= 9580Hz, and if D=38mm, f[38]=4540Hz, but in your measurements none of the mentioned frequencies are visible as notches.

Regards
Ivica

Hi Ivica,

the HR9040 monotonously increases area like all good horns do, but being square in area, it can do so while severly tapering vertical size from 33mm to 18mm. I don't have HR9040, so the 9.5kHz notch cannot possibly be in my measurement screenshots. For more info, see posts ab0ez and i did elsehere. The 1975 Keele paper you quoted has a drawing of vertical expansion. Horizontal expansion of HR9040 and HR9040A are the same except for the first 1cm into the horn. That first horizontal 1cm is very different, though. It's also printed in the 1975 paper.

The HR9040A does not taper the incoming 33mm at all, but rather opens up gradually. I can see your reasoning for an artifact at 4.5 KHz. Not sure we should expect a pronounced diffraction effect, if the horn opens up. I have maybe 50 more measurements of HR9040A with about 15 different drivers. I just went through them and saw there is a tendency (visible with about two thirds of the drivers) to have a reduced amplitude by about 3dB @ 4kHz, not 4.5 kHz. This drop is not narrow as in the plot by Keele you attached, but i will re-do some of these plots in 24th oct resolution to see whether your prediction is right. I will upload if i find something useful.

Ralph

[ivica]

Hi Ivica,

the HR9040 monotonously increases area like all good horns do, but being square in area, it can do so while severly tapering vertical size from 33mm to 18mm. I don't have HR9040, so the 9.5kHz notch cannot possibly be in my measurement screenshots. For more info, see posts ab0ez and i did elsehere. The 1975 Keele paper you quoted has a drawing of vertical expansion. Horizontal expansion of HR9040 and HR9040A are the same except for the first 1cm into the horn. That first horizontal 1cm is very different, though. It's also printed in the 1975 paper.

The HR9040A does not taper the incoming 33mm at all, but rather opens up gradually. I can see your reasoning for an artifact at 4.5 KHz. Not sure we should expect a pronounced diffraction effect, if the horn opens up. I have maybe 50 more measurements of HR9040A with about 15 different drivers. I just went through them and saw there is a tendency (visible with about two thirds of the drivers) to have a reduced amplitude by about 3dB @ 4kHz, not 4.5 kHz. This drop is not narrow as in the plot by Keele you attached, but i will re-do some of these plots in 24th oct resolution to see whether your prediction is right. I will upload if i find something useful.

Ralph

Hi Gibber,

Looking at the mentioned Mr. Keele presentation HR9040 it seems to me that in vertical plane there is almost about 10cm ( 4-inch) part of almost parallel surfaces, but as I have understood you, on HR9040A there is "almost" the same 'situation' but 38mm (or some mean value form 33mm to 38mm) not 18mm distance. But there is no any 'intention' of notch-filtering effects, around 4.5kHz.

[gibber]

Hi Ivica, just in case you own HR9040, would you say that the drawing you attached is correct? I ask because from photos i saw i seem to remember the vertical tapering does not happen at the horn throat only, but is more gradual. Maybe i'm mistaken, it's been a year since. Here's one of the measurements where the driver showed a 4kHz 3 dB droop on HR9ß40A -- redone for you in 24th oct resolution. The meas conditions are not the same as they were when i did the 6th oct plot last year, but are similar as for the screenshots i posted in this thread before. Maybe ca 2dB are broadly missing in the area around 4.5 kHz. But a strong notch effect is not there. Let's maybe take further discussion of the EV horn into pm, as i believe this thread veers off-topic quite a bit already.

[ivica]

Hi Ivica,
.................Let's maybe take further discussion of the EV horn into pm, as i believe this thread veers off-topic quite a bit already.

[]

Hi Gibber,
Many thanks for your precise work, I have sent you PM.
Regards
Ivica

[Mr. Widget]

Widgetthanks for the info,do Trueextent mine Be and do the foils or just mine Be and have Be end user products ?That would be interesting to know, as i heard from a French speaker designer there are only two Be foil companies ww, so Truextent might have the whole value chain in-house.

Truextent is part of a much larger company. Part of the company mines the ore in Utah, part of the company creates the foil in the midwest, and the part here in California creates the Truextent diaphragms that we have been talking about as well as domes and foils for other loudspeaker companies.


Widget