How good is the Altec 511B horn and driver (GPA 902) compared to todays exclusive High Fidelity tweeters.
Is it worth the money to spend on the Altec 511B horn ,and new GPA drivers, when you can get newly developed and well regarded high fidelity tweeters
around for about the same money, and less size.
What are the benefits to go an Altec horn route. Will they sound better to any ears ? More engaging ? Better soundstage etc. etc.
or is it just nostalgia?
It's a question that is actually several questions; one part being, are horns better than other midrange & tweeter solutions. Horns typically offer better dynamics and controlled dispersion and (at least to my ears) better "realism", for whatever reason. Horns also offer better sensitivity than most other solutions, so class A amplifiers become very practical.
The latest TOTL JBLs use (bi) radial horns, and the fairly recent K2 S9800 used a radial horn (H9800) very similar in shape to the 511 and 811: H9800
More recent horns sometimes offer better dispersion it's true, although IMHO the verdict is still out as to whether a CD horn offers better sound for hi-fi listening, as opposed to pro audio, where you need the dispersion. Dispersion is a two-edged sword; the sound radiated over a wider angle will cause more room reflections and hurt clarity. A lot of audiophiles seem to prefer the LeCleach and Tractrix horns, both of which have collapsing directivity with frequency. A design like the 511 or 811 strikes a compromise for dispersion, one which I'm happy with.
My $0.02 etc.
Last edited by fpitas; September 24th, 2012 at 04:49 PM.
An apples n' oranges comparison. To even try and compare the two, you'll need to XO the 511 high enough that it's merely a WG [guessing around 2 kHz] and once EQ'd flat I doubt it will sound much different or be much more efficient than a very high end cone/dome tweeter except that the latter will have a bit more top end 'air' that depending on one's hearing, may not be noticed.
You want the best of both and can afford them, buy a prosound WG loaded ribbon if they still make them.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
I thought dome tweeters had sensitivities in the 91dB/1W/1m sort of range?
Originally Posted by GM
They do.
A 1 inch compression driver has a mass-induced -6 dB/octave drop above 3 kHz. A good CD horn will have an on-axis response nearly identical to its terminated tube (plane wave tube) response; that is, the unequalised CD horn output will match the driver power response. It must be equalised to be flat.
In the upper octave with equal electrical input power, the dome and compression driver will have comparable acoustical output power.
BobR
Anyhow, I'll agree with Old Guy that choice of horn type / HF driver is a personal preference or - for a manufacturer - an application dictated by swings and roundabouts... that is, finding a balance of attributes that fits the matter at hand.
I had a set of 802/511Bs + 515B in 825 cabinets during the 1980s and they certainly sufficed at the time -- the 511s were quite pleasing on-axis so I understand why they're still sought.
BobR
Which would put it down between about -11 & -22 dB in the top octave. Or about as efficient as a good dome. But don't forget, down low it's still much more efficient than the dome. That's where the energy is and were it should be used.
A great tweeter it would not be, but a great extended mid-range, it is.
The H9800 is a BiRadial; it is a constant-directivity design based on the work of D.B. Keele.The latest TOTL JBLs use (bi) radial horns, and the fairly recent K2 S9800 used a radial horn (H9800) very similar in shape to the 511 and 811: H9800
Room reflections will not affect clarity so long as RT60 (reverberation time) is sensible and room modes are well-distributed, and additionally an even power response yields a spectrally balanced reverberant field.More recent horns sometimes offer better dispersion it's true, although IMHO the verdict is still out as to whether a CD horn offers better sound for hi-fi listening, as opposed to pro audio, where you need the dispersion. Dispersion is a two-edged sword; the sound radiated over a wider angle will cause more room reflections and hurt clarity.
This was the impetus for developing constant-directivity design and it is nearly impossible to find contemporary control room monitors or even well-designed high-end audiophile loudspeaker systems that do not have even power response.
Good directivity index is only one criteria inherent in horn/system design (albeit a very important one); others include good low-frequency loading, low second harmonic distortion and freedom from unwanted constructive/destructive interference and diffraction. Commercial designs attempt to balance these depending on intended use (cinema, sound reinforcement, critical listening, etc.)A lot of audiophiles seem to prefer the LeCleach and Tractrix horns, both of which have collapsing directivity with frequency. A design like the 511 or 811 strikes a compromise for dispersion, one which I'm happy with.
Apparently those audiophiles are willing to sacrifice certain attributes to maximise others.
BobR
Got a link to a design paper for the H9800? It has flat sides in every picture I've seen; I thought bi-radials had curved surfaces.
As for the reverberation time factoring into it, the home listening environment isn't usually that well-controlled.
My apologies; my error. I was referencing the horns in the TOTL S9800. The H9800 does appear to be a standard radial horn.
All the more reason to use excite the reverberant field evenly as the spectral balance of reflections must resemble the original sound for Precedence Effect to work. Most typical living rooms have usable RT60 (400 - 600 mS) and can work with even power response loudspeaker systems with little room treatment.As for the reverberation time factoring into it, the home listening environment isn't usually that well-controlled.
BobR
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