Acoustic power and dispersion

[Sonnar]

I suspect the theory according to which a speaker with better dispersion should sound making clear mid-high frequencies it does not match what we perceive. If it were so, an AR LST or an AR 3a should sound much more sparkling than a JBL L 65 Jubal : the 077 high frequency compression driver has a very poor dispersion ,  but the Jubal , a speaker I know very well, sounds much more sparkling , too much sparkling , and with high frequencies very present , in the foreground. I have often found that a speaker sounds exactly as revealed by its frequency response in anechoic chamber , in axis. Maybe I 'm wrong , but this is the reason why some people like me prefers the smooth and balanced sound of AR speakers and some people prefers the unbalanced , sparkling and rich in high frequencies sound of West Coast speakers , which have very little dispersion.    Adriano

[der]

West Coast sound = Squawk and Boom. Just the right type of speaker for Led Zeppelin at 110db.  

der

[Sonnar]

I totally agree with You, but my question is  about acoustic output : theoretically, a poor dispersion horn speaker should sound dull and without high frequencies in comparison to an extrawide dispersion speaker like AR LST : but in fact, when You listen to a West Coast speaker You have the perception of an ubalanced speaker oriented towards high frequency . 

[fedeleluigi]

4 hours ago, Sonnar said:

I suspect the theory according to which a speaker with better dispersion should sound making clear mid-high frequencies it does not match what we perceive. If it were so, an AR LST or an AR 3a should sound much more sparkling than a JBL L 65 Jubal : the 077 high frequency compression driver has a very poor dispersion ,  but the Jubal , a speaker I know very well, sounds much more sparkling , too much sparkling , and with high frequencies very present , in the foreground. I have often found that a speaker sounds exactly as revealed by its frequency response in anechoic chamber , in axis. Maybe I 'm wrong , but this is the reason why some people like me prefers the smooth and balanced sound of AR speakers and some people prefers the unbalanced , sparkling and rich in high frequencies sound of West Coast speakers , which have very little dispersion.    Adriano

Adriano, I think you should always consider the total amount of energy radiate on 360 degrees and not exlusively the one radiated on axis (0 degrees).

 

The only 0 degree anechoic chamber frequency responce will not tell you much about the loudspeakers sound in a listening room.

 

If a loudspeaker had a perfect flat 0 degrees frequency responce in an anechoic chamber using a hypothetical tweeter with no dispersion , (i.e. the tweeter does not radiate anithing off axis),   in a normal listening room, the loudspeaker sound would be with very reduced treble. 

 

The 077 JBL tweeter is not a "laser". In other words although it has not a very high dispersion,  it radiates an amount of energy also off axis. You should consider the total energy radiated by 077 tweeter on 360 degrees. Probably it isn't low.

 

In a listening room, the sound pressure perception depends on the total amount of direct and reflected sound pressure that arrives at your ears.

 

Hope someone more expert than me will give you a better answer.

 

Luigi

 

[Sonnar]

Luigi, I have an Altec/Jbl horn system, the 802 8g drivers/811b horn and the " bullet " 075 JBL tweeter radiates in a very small angle , the directivity is one of the major problems of first-generation exponential horns. The 077 has a decent radiation horizontally, but very poor vertically, as shown in JBL' s technical datasheet, and the 075 , which I use because of its grater sensitivity, its circular exponential horn provides a dispersion pattern that is 40 degrees at 10 Khz, very poor compared to the extrawide dispersion of AR's dome tweeters: however , these JBL , Altec, E-V horn system have a very sparkling sound with high frequencies in evidence if compared with an AR speaker : and in fact, their on-axis requency response is very rich in high frequencies . Greetings, Adriano

[fedeleluigi]

32 minutes ago, Sonnar said:

however , these JBL , Altec, E-V horn system have a very sparkling sound with high frequencies in evidence if compared with an AR speaker : and in fact, their on-axis requency response is very rich in high frequencies . Greetings, Adriano

Adriano, I've never seen the anechoic frequency response of these loudspeakers, but if these loudspeaker on-axis frequency response is flat and you perceive excessively powerful high frequencies, the total amount of energy radiated by their tweeters on 360 degrees will be in any case high. Maybe this energy is enclosed in not many degrees (unlike AR's) but the overall energy will be high anyway.

Luigi

[genek]

How "sparkling" a speaker sounds is probably determined more by how its designers voiced it than by its dispersion. What dispersion does most is determine whether whatever sound the speaker produces is uniform over a broad area of the listening space, or limited to a relatively small listening "sweet spot."

AR speakers didn't have less emphasis on highs than west coast speakers because they had wider dispersion, but because that was how their designers intended for them to sound.

[Sonnar]

Very often these speakers shows an increasing high frequency response in axis , not flat : in fact , listening to one of these speakers You have the perception of an exaltated high-range , as shown in anechoic chamber on axis frequeny response . One of the most important progress in horn design is the late '70 Was Mantaray and Constant Directivity horns , which shows a better dispersion respect to old exponential design and much more than conical horns used in JBL's classic monitors 4333, 4343, JBL used acoustic lens to improve the very poor dispersion while Altec used sectoral horns for small format drivers and multicellular long-throw horns ( from 805b to the giant 1505 ) for large format drivers ( 288, 291 ) , and the reason was still the same , directivity increases with frequency. However, despite their high directivity and poor dispersion, these horn speakers sounds very sparkling , ( too sparkling to me ) and I have the perception of a lot of high frequencies . To have an idea You can see to JBL 's 077 data sheet at www.jblpro.com >pages>obsolete . Greetings, Adriano

[Sonnar]

1 hour ago, genek said:

How "sparkling" a speaker sounds is probably determined more by how its designers voiced it than by its dispersion. What dispersion does most is determine whether whatever sound the speaker produces is uniform over a broad area of the listening space, or limited to a relatively small listening "sweet spot."

AR speakers didn't have less emphasis on highs than west coast speakers because they had wider dispersion, but because that was how their designers intended for them to sound.

And that is exactly what I mean. Despite its better dispersion, AR 3a tonal balance is slightly different from 3's , a strong midrange and a gradual roll-off in the high range, while AR 3 appears smoother and more linear , there is more " air " around the speaker , and high frequencies appears more extended and transparent . I said slightly different in tonal balance , differences are very subtle. A speaker sounds sparkling or dull because of its frequency response , linear and well-balanced just like an AR 3 or non-linear and unbalanced like horn monitors , it' s a matter of proportions between frequencies . My best wishes, Adriano