Horn Honk $$ WANTED $$

[dantheman]

Nice Soong, nice.

Dan

[soongsc]

Thanks. There seems much to be learned.
In the Newell and Holland book on loudspeakers, it mentions smooth acoustic impedance is an important factor. In my experience, stored enegy plays an important factor in how clean the sound reproduction will be. Now looking at these sims, it seems acoustic impedance is more related with efficiency of the system, and probably has less to do with any honk or HOMs than I originally thought.

[Elias]

Hi,

It took a while but here's some wavelets of the JBL2431H in RCA MI9594 horn.

Here's a multiresolution wavelet from 500Hz-20kHz up to 20ms. The right hand side is normalised to 0dB at every frequency.


And here's 'conventional' wavelet:



And here's the same but from 1kHz-20kHz up to 10ms:





There is two long resonances, at about 7.5kHz and 15kHz.

Before 2ms there is two strong reflections. Interesting would be to know if the reflection at 3ms is from the horn or the room?


Where is the honk in this horn?

In this big horn throat-mouth-throat distance is about 1.5m and thus it takes about 4.3ms for a mouth reflection. But there is nothing much seen at 4.3ms??

It might be needed to measure this horn outside without room reflections to separate the honk from the room? Have the snow melted yet?


- Elias

Originally Posted by EarlK

...

• The horn is a huge old RCA 60 degree radial / similar to the Altec 311-60 ( minus the mouth vanes ) .
• Rough dimensions of the horn are ;
  • Mouth ; 13H x 24.5W ( 33cm x @ 62.23 cm )
  • Depth ( to driver ) @ 29" ( 73.66 cm )
  • Depth ( to diaphragm ) @ 30" ( 76.2 cm )

...

ps ; heres the ARTA file zipped .

[thend]

Originally Posted by Elias

It might be needed to measure this horn outside without room reflections to separate the honk from the room?

Or use the impedance curve.
Simple and effective.

[Elias]

Originally Posted by thend

Or use the impedance curve.
Simple and effective.

Does a room reflection show up in the impedance in your tube method?


- Elias

[thend]

Originally Posted by Elias

Does a room reflection show up in the impedance in your tube method?


- Elias

Probably, but very lesser than horn reflection.

I was talking about impedance even without tube, for wavelet.
The tube has other advantages

[mige0]

could we possibly do a wavelet correlation between the two methods ?
We would need from the same horn both, the acoustic and the impedance measurement.

Also - I was thinking about doing some measurements right at the throat for comparison.
This should have further benefit in diminishing room interaction. With all the wavelet software checking and also some basic coding I haven't had time to do myself - but its definitely on my list...

Michael

[Pano]

Well I don't know, but what I see in those wavelet graphs is mostly junk between 1-3KHz.
That's where it is the messiest. And in the freq. range, it should be very easy to hear.

[ZilchLab]

Originally Posted by Elias

Where is the honk in this horn?

In this big horn throat-mouth-throat distance is about 1.5m and thus it takes about 4.3ms for a mouth reflection. But there is nothing much seen at 4.3ms??

If "honk" is down near cutoff, there is certainly trouble just below 4ms.

The stuff up top is something other than honk, by this view.

[ScottG]

Originally Posted by ZilchLab

If "honk" is down near cutoff, there is certainly trouble just below 4ms.

The stuff up top is something other than honk, by this view.

Not entirely.

You can see periodic resonances that travel up from the primary "mouth" resonance.

What you can't see is how the entire output is modulated by the mouth resonance - i.e. freq. response "ripple" at the average. (.."average" meaning full-output.) In this respect (and generally), I prefer a well-scaled series of CSD plots at varying axis's.