Another Noob question...rear tweeters

A

am74Gibson

Junior Audioholic
I was killing some time at work surfing for information on speakers. I have seen some that have 2 tweeters...one front and one rear. (infinity RS9 Kappa for example)

I have always heard that tweeters are mostly directional and should be facing the listening area. What does a rear facing tweeter do if it is facing the rear wall? I know the speaker should be out a couple of feet, but still, it seems like a waste.

Even if you got some bounce off the rear wall, wouldn't that kind of screw up the imaging?

any thoughts?
 
A

am74Gibson

Junior Audioholic
Always happens

Posted this thread because I could not find any info. Once I posted, found it right away...go figure...

Here is what I found...

The purpose of the rear tweeter is to supply room ambience. According to Madrigal, tweeters become increasingly directional at higher frequencies and contribute progressively less high frequency energy into the listening area as frequencies increase. The Salon's rear tweeter and its frequency shaping network provide very high frequency "sound power" output. The combination of the front and rear tweeter were done in an attempt to create an ideal reverberant field.
 
bandphan

bandphan

Banned
relections off the rear/side walls in the effects channels
 
TLS Guy

TLS Guy

Seriously, I have no life.
I was killing some time at work surfing for information on speakers. I have seen some that have 2 tweeters...one front and one rear. (infinity RS9 Kappa for example)

I have always heard that tweeters are mostly directional and should be facing the listening area. What does a rear facing tweeter do if it is facing the rear wall? I know the speaker should be out a couple of feet, but still, it seems like a waste.

Even if you got some bounce off the rear wall, wouldn't that kind of screw up the imaging?

any thoughts?
Good dome tweeter are not directional, they have excellent dispersion

The problem with placing a tweeter in the rear of a speakers, is that the direct source is separated in distance, and therefore time from the ambient source. I and many others regard that as not an improvement, and actually a practice best avoided.
 
WmAx

WmAx

Audioholic Samurai
Good dome tweeter are not directional, they have excellent dispersion

The problem with placing a tweeter in the rear of a speakers, is that the direct source is separated in distance, and therefore time from the ambient source. I and many others regard that as not an improvement, and actually a practice best avoided.
One has to qualify 'directional'. Even the best dome tweeters become substantially directional above 10kHz. The energy out to roughly 14kHz-15kHz is actually quite relevant to spatial/localization cues and such, perhaps this should be one consideration in the horizontal response characteristics of a high frequency transducer. But, it is very rare to find a transducer with wide dispersion at say, 15khz.

So far as the modern scientific literature goes, given an even full range spectrum, reflections from the front area do not demonstrate a negative subjective impact in highly controlled experiments on a wide variety of human test subjects, given a sufficient time window of integration for the direct sounds vs. reflected sound. However, the precise subjective effect into the subjective positive range has not yet been assessed in the appropriate controlled perceptual research as of yet. The effect has been assessed for side wall reflections into the subjective positive range, and these are found to be beneficial for sound quality, assuming a specific time window of integration for the reflected vs. direct sound arrival at the ear.

Personally, in the experiments I have conducted in as best a controlled situation as I can manage in a home environment, I find that rear reflections within an appropriate time window are positive in terms of sound quality - but only under very specific conditions - and with specific room acoustical treatments being applied for this condition that may be considered unreasonable by most people.

-Chris
 
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TLS Guy

TLS Guy

Seriously, I have no life.
One has to qualify 'directional'. Even the best dome tweeters become substantially directional above 10kHz. The energy out to roughly 14kHz-15kHz is actually quite relevant to spatial/localization cues and such, perhaps this should be one consideration in the horizontal response characteristics of a high frequency transducer. But, it is very rare to find a transducer with wide dispersion at say, 15khz.

So far as the modern scientific literature goes, given an even full range spectrum, reflections from the front area do not demonstrate a negative subjective impact in highly controlled experiments on a wide variety of human test subjects, given a sufficient time window of integration for the direct sounds vs. reflected sound. However, the precise subjective effect into the subjective positive range has not yet been assessed in the appropriate controlled perceptual research as of yet. The effect has been assessed for side wall reflections into the subjective positive range, and these are found to be beneficial for sound quality, assuming a specific time window of integration for the reflected vs. direct sound arrival at the ear.

Personally, in the experiments I have conducted in as best a controlled situation as I can manage in a home environment, I find that rear reflections within an appropriate time window are positive in terms of sound quality - but only under very specific conditions - and with specific room acoustical treatments being applied for this condition that may be considered unreasonable by most people.

-Chris
I've told you before, I'm an old geyser! I can't hear to 15 K any more. All I can say is I have experimented with rear firing drivers over the years, and overall have not found it helpful.
 
A

am74Gibson

Junior Audioholic
Very well written!

One has to qualify 'directional'. Even the best dome tweeters become substantially directional above 10kHz. The energy out to roughly 14kHz-15kHz is actually quite relevant to spatial/localization cues and such, perhaps this should be one consideration in the horizontal response characteristics of a high frequency transducer. But, it is very rare to find a transducer with wide dispersion at say, 15khz.

So far as the modern scientific literature goes, given an even full range spectrum, reflections from the front area do not demonstrate a negative subjective impact in highly controlled experiments on a wide variety of human test subjects, given a sufficient time window of integration for the direct sounds vs. reflected sound. However, the precise subjective effect into the subjective positive range has not yet been assessed in the appropriate controlled perceptual research as of yet. The effect has been assessed for side wall reflections into the subjective positive range, and these are found to be beneficial for sound quality, assuming a specific time window of integration for the reflected vs. direct sound arrival at the ear.

Personally, in the experiments I have conducted in as best a controlled situation as I can manage in a home environment, I find that rear reflections within an appropriate time window are positive in terms of sound quality - but only under very specific conditions - and with specific room acoustical treatments being applied for this condition that may be considered unreasonable by most people.

-Chris
Wow, I am impressed with your eloquence, you should sell used cars ;-)

But one thought comes to mind...if tweeters lose their dispersion after frequency increases, why are most speakers designed with a single, front firing tweeter? Why not put 3 mounted horizontally at angles, with the center facing front, the left and right appropriately facing slightly left and right? I suppose a horn tweeter is as close as it comes to doing this.
 
haraldo

haraldo

Audioholic Spartan
Wow, I am impressed with your eloquence, you should sell used cars ;-)

But one thought comes to mind...if tweeters lose their dispersion after frequency increases, why are most speakers designed with a single, front firing tweeter? Why not put 3 mounted horizontally at angles, with the center facing front, the left and right appropriately facing slightly left and right? I suppose a horn tweeter is as close as it comes to doing this.
Actually, Aussie brand VAF has done that in one of their products.... (not 3 but 2 tweeters)
http://www.vaf.com.au/detail.asp?audio=dc&grunt=s200r26724
 
haraldo

haraldo

Audioholic Spartan
I personally have not liked speakers with drivers facing in more than one direction. I think it is the spacing that causes the trouble.

Here are a couple of tweeter pdf,one dome the other a ring. The dispersion is not perfect, but not terrible either.

http://madisound.secureserverdot.com/catalog/PDF/seas/e011.pdf

http://madisound.secureserverdot.com/catalog/PDF/R2904_700000.pdf
Of course, to get something good you had to pick a Norwegian tweeter :D

Jokes aside... What's never shown in tweeter measurements are compression figures, or the lack of compression, at which I've read the Scan Speak ring radiator is almost text-book perfect.... Any thoughts on this?
 
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haraldo

haraldo

Audioholic Spartan
We agree about Stax headphones also!
And Sailing !!!
I love it, nothing beats reaching with spinnaker in a large boat


I actually lived for a year less than 5 miles from the Seas Factory, these are really professional guys, I can't comprehend how they can manage to create all these custom versions of their drivers for all kinds of different speaker manufacturers like, Like Audio Physic, Sonus faber, Krell, Burmester and a whole bunch others.....
 
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TLS Guy

TLS Guy

Seriously, I have no life.
And Sailing !!!
I love it, nothing beats reaching with spinnaker in a large boat


I actually lived for a year less than 5 miles from the Seas Factory, these are really professional guys, I can't comprehend how they can manage to create all these custom versions of their drivers for all kinds of different speaker manufacturers like, Like Audio Physic, Sonus faber, Krell, Burmester and a whole bunch others.....
Oh yes sailing!

On Benedict Lake we don't have sea room for a large sailer. However I restored from a complete wreck a 1959 O' Day Daysailer. I bought it for $150. Restoration took two years. I did it all on site in my large shop.

http://mdcarter.smugmug.com/gallery/2464830_TxYuH#129274810

The outboard is an 1953 Evinrude 3.5 horse.

I grew up sailing on the Medway and Thames estuaries.

I bolted from socialism in 1970 when Harold Wilson was PM.
 
haraldo

haraldo

Audioholic Spartan
If you get to Bergen, you can come with me and sail regatta's with my friends in a First 40s7 (that's 40 feet).... Last year we were the first boat in.... In the largest regatta to win overall.... in the most popular regatta over here...
I ran the spinnaker sheets all the way, and you could see the smile on my face for 4 miles..... Do you think that's fun :)
I'll give you one shot to answer :D

(The only downside is that the boat is French)

What the HE..... Did I see a T-shirt in some of the pictures with the text: Norge

And, nice work on the boat!!!!!!!!
 
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TLS Guy

TLS Guy

Seriously, I have no life.
If you get to Bergen, you can come with me and sail regatta's with my friends in a First 40s7 (that's 40 feet).... Last year we were the first boat in.... In the largest regatta to win overall.... in the most popular regatta over here...
I ran the spinnaker sheets all the way, and you could see the smile on my face for 4 miles..... Do you think that's fun :)
I'll give you one shot to answer :D

(The only downside is that the boat is French)

What the HE..... Did I see a T-shirt in some of the pictures with the text: Norge

And, nice work on the boat!!!!!!!!
Thanks for the kind invitation! After my two very extensive surgeries of last year, I would not be much use as crew I'm afraid. I have to be careful what I tug and reef on for ever and a day.

I don't venture out on my sailer anymore without a strong crew member along.
 
haraldo

haraldo

Audioholic Spartan
Thanks for the kind invitation! After my two very extensive surgeries of last year, I would not be much use as crew I'm afraid. I have to be careful what I tug and reef on for ever and a day.

I don't venture out on my sailer anymore without a strong crew member along.
Just being there :D:D:D:D:D
Nice weather, sunshine, gentle wind against your hair,seeing all the competitors left behind in the dust....
Running a spinnaker reach in 14 knots......
What more can you ask for.....

Sorry guys about hijacking the thread :-D
 
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