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132.147.145.198
Electro-Voice Aristocrat with a 12TRXB coax...which frequencies act like they are delivered through a horn? I'm thinking clarity and dynamics.
And these terms--horn-loaded, back-loaded, front-loaded, corner-loaded--what exactly does "loaded" mean? Does "loaded" (acoustically) always refer to a horn?
Follow Ups:
Nice work by everybody in this thread, but I'll pile-on in the margins, anyway. The freqs that "act like a horn" are, driver-depending, 80-120Hz in Aristocrats--that's jacked-up ~6dB over the already corner-lifted response. One can muscle that down by choking the pinch some, but at the cost of excursion and even more stubborn ringing (than the already stubborn design). What comes out the back is at least partially dependent on how you line and fill them (treat them like a taller reflex-box is more sane than leaving them empty, IMO).
Loaded doesn't always refer to only horns. For the "room" part of the loading, Mr. Murphy has a nice 1-pager https://trueaudio.com/st_spcs1.htm
Re the response curve, context is in order.
- cab design was from late '50/early '51
- this was still when cabs were sold for Any driver that fit the hole
- curves shown are pads wide-open on MR/HF as approp (BUT)
- subject curve was for the Radax (aka Whizzered) SP12B--a 12" playing to around ~10kHz
- motion pic assoc standard of the time was +/- 5dB
- given a '50's car, what standards might we hold it to?
If your house has solid corners (ie not sheetrock + nothing), they're still cool designs, EV just made them too thin and didn't line/fill them quite enough or brace them enough (esp the baffles & the top). All that is understandable given the need to market (and ship!) cabs as Hi-Fi exploded during the "golden era".
Another category of speaker which couples the speaker to air are 6th order bandpass speakers. While not horns, they still fall within a category of high transducer-air coupling devices.
Many backloaded horns are a kind of cross between horns and TQWP speakers, so many of these types of speakers are in a sort of grey area.
Retsel
The Aristocrat is a rear loading folded horn. As for it not looking like a horn, yes, it does. You just have to know where to look. It's pretty obvious if you look at cutaway on the data sheet.
Loading refers to the treatment of the air in front of or behind the speaker cone. It is very difficult for the cone to transfer energy to air because of the great difference in mass (think of how hard it is for you to throw a feather, the feather does not have enough mass to push back against your body so it is hard to transfer much energy to it. The way a speaker traps air in front of or behind the driver so that the mass is increased or the resistance increased through compression of the air, affects efficiency. The greater the resistance the more effective is the transfer of energy. The horn in front of the speaker acts to contain the air and improve such energy transfer. The same is true with the various approaches to the back wave. All speakers, except perhaps open baffle designs, harness that back wave energy and provide some resistance and control of the woofer movement.
Some speakers employ a long, gradually widening channel behind the woofer which is then ported to the outside, this back wave substantially adds to the speaker output. Such designs are often described as back loaded horns (e.g., "quarter wave back loaded horn") or some described as "transmission line").
For other people a horn means a speaker where one or more drivers has a wave guide in front that directs the propagation of the sound wave into a narrower beam than would be the case without the horn wave guide. To me, a horn wave guide does not make a speaker a horn system. I use that term for a system where the midrange has a horn wave guide, but also the driver is a compression driver. A compression driver utilizes a dome diaphragm pushing against air contained in a small chamber. Because the diaphragm has to work against higher resistance from the tramped air (it has to compress that air), energy transfer is much improved and the drivers tend to be very efficient. To me, the magic of horn-based system is mainly in the midrange compression driver and horn waveguide combination.
As far as sound characteristics, horn systems tend to be very vivid and lively sounding, though some tend toward being tonally colored (nasal or peaked at some point in the midrange). But, there are many systems that don't use midrange compression drivers that do sound like very good horn systems and have similar high efficiencies, such as some fullrange driver systems. For example, Charney Audio makes terrific sounding speakers using one fullrange driver that delivers most of its treble and midrange from a paper cone driver (no horn wave guide), but the back wave delivering most of the bass would be considered a quarter wave back loaded horn. Songer Audio makes systems using a field coil fullrange driver that reminds me of horn system and their speakers are also terrific.
Larry, very helpful explanation, thanks!
On the Aristocrat/12TRXB combo,I assume the LF's would be routed out the back, and the HF's have their own little coaxial horn...but what about the vocal range? Out the rear, or Direct Radiator?
I am not that familiar with this particular system, but, I believe it is a triaxial speaker meaning it has a midrange cone and a horn tweeter all centered in the middle of the woofer cone. It is only a "horn" system in that the tweeter has a horn type wave guide. The woofer part of the cone will deliver bass and midrange frequencies firing forward. The rear wave is loaded in a conventional bass reflex cabinet so that the output of the port is primarily very low frequencies.
But, these types of systems which are meant to be put into the corner of the room are also sometimes referred to as corner horns because the walls at the corner act as wave guides directing the sound toward the listener. This is another example of how the term "horn" is used in different ways. The Klipschorn is also described as a corner horn because of similar placement, but, it is also a horn system because it employs compression drivers and horn wave guides while the E-V triaxial driver is not a compression driver.
A room corner isn't a wave guide. When a corner horn like the Aristocrat or Klipschorn is in a corner the room walls act as an extension of the horn. Combined with the 1/8 Pi space loading of a corner the lows are significantly boosted, although any speaker placed in a corner will get 1/8 Pi space loading at low frequencies.As to the term wave guide it's vastly overused. Technically speaking a wave guide is a horn with a throat that's at least one wavelength in dimension. That being the case it doesn't have the gain that a horn with a throat less than a wavelength in dimension has. We never saw the term 'wave guide' used until roughly 20 years ago. Someone started using it interchangeably with and in favor of 'horn', not for technical reasons but for marketing reasons, to overcome consumer resistance of the unwarranted poor reputation of high frequency horns. IME at least 90% of what are called wave guides are actually horns. If it's got a one inch throat it's a horn below 13.5 kHz.
Edits: 11/06/24
enn tee
all the best,
mrh
Yes wave guide is probably the wrong term. The walls limit the area that the speaker radiates into and thereby boosts efficiency and bass response (because bass otherwise goes in every direction).
Yours is a much more precise description.
The term "waveguide" was borrowed from the microwave area and came in to use when the constant directivity horns were first developed. These were needed for use when there is an audience listening vs a listener.
Horns can increase the efficiency by coupling more of the radiation impedance to the cone.
Horns can also appear to increase the efficiency by confining the radiation to a smaller angle so what one measures is normally the product of both things.
These two points both have a rule of thumb; for the impedance transformation, this stops at a frequency related to the horn passages circumference. This is why in the old days, people would say a 30Hz horn has to be 10 feet in diameter which is the point where the transformation stops BUT it doesn't mean the horn won't work if smaller.
On the other hand the expansion rate has a "high pass" corner in this transformation, for example a 30Hz exponential horn can't expand any faster than doubling it's area every 2 feet or so.
On the other other hand, the point that the horn stops controlling the radiation angle is approximately 10^6 / horn angle / / horn mouth dimension (inches) as cited by don Keele.
.
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Why you directed this to me I can't figure. Maybe it was in error? In any event this is how horns work:
Edits: 11/06/24
I thought I was responding to the OP. Yes, calling it an impedance transformer is a good description.
Awful frequency response. But at least EV proudly published it?!
That's a measurement at the limit of resolution then, not one smoothed to say 1/3 oct or more like many / most nowadays.
What one can see or to me, if i had to pick one, it would the the sp12 radax. That one (the measurement there) appears to have the least discontinuity and measurement "grass" both of which are counter indicators of a speaker that can make a strong phantom image in stereo.
The response flatness is a separate issue you would hear strongly as in very bright but it's simple shape and it's impedance curve would make it easy to fix even passively nowadays.
In general, the smaller coax drivers that have a horn at the center under the dust cap and use the cone body itself as part of the horn, can have the least discontinuity at the horn to cone radiation and that cone can then itself drive a "front" horn (if the horn angle is at or greater than the cone angle and the smallest possible discontinuity at the transition. At the opposite, there are some larger cone drivers that have a large horn attached at the center which have the discontinuity lower in frequency where the acoustic relationship makes them closer together and less significant
Using these drivers usually requires working out a network (in a passive speaker) to make the crossover and combined response flat or what ever.
In some drivers an adapted crossover shape can allow for a much smaller phase shift through crossover than normal as the hf signal emerges from the high pass filter before the woofer but is behind the woofer and so where everything is right, with a higher order filter, you can get less than 90 degrees per order phase shift, even zero like a single driver.
Frequency response isn't everything. High sensitivity and low distortion are the hallmarks of horns. Besides, the ragged response above 1.2kHz isn't from the woofer, it's from the high frequency unit.
I was interested because I almost bought a EV Regency III. If I bought any of these EV's, I'd be interested in changing out the horn/CD's on'em.
i would love to hear this now
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