Lowthers are at their best between 150 Hz and 1.2 kHz, higher in freq. and things start going wrong *fast*.
300 Hz is going to be tough to accomplish with a compression driver (that extends to 18 kHz). Particularly with respect to horn-size (..which starts becoming HUGE). It's not impossible, but it will be very difficult.
500 Hz..and higher - yeah, that's realistic. (..though a good horn/waveguide will still be large).
I prefer wider dispersion for a horn/waveguide - which tends to result in a larger sound-stage presentation. Here is the horn/waveguide I'd suggest:
Fiberglass SEOS-24? - The SEOS? Waveguides DIY Sound Group
From there it's about choosing your compression driver in the 1.4" to 1.5" exit grouping.
I like several of the 18 Sound drivers for their diaphragm material + suspension type + reasonably well-controlled impedance.
The single driver with the most "band for the buck" IMO would be the ND1460A, which can be purchased for as little as $330 US each in either the 8 ohm or 16 ohm versions:
18 Sound HF Compression Drivers
The Radian 745NEOPB is also very well received AND costs a bit less, but I've not seen its impedance profile. (..and the impedance profile could well cost you more in crossover components for correction than the difference in price between the drivers).
Also, as a general statement: the higher the driver's gauss the more "transparent" the driver relative to driver Mms and Sd. (..though transparency or extreme clarity is not always preferred).
This should mean that perceptually the 18 Sound 1480A is clearer than the Radian 745NEOPB, which is clearer than the 18 Sound 1460A.
Also, the larger the compression driver's diaphragm - generally the better it is at depth reproduction (..though usually with some resulting loss in treble dispersion). All 3 of the above drivers have 3" diameter drivers, however..
-there is also the newer Be driver from 18 Sound at only a little less than double the price of the 1480A with a 4" diaphragm (and in fact they have several others as well with 1.5" or even 1.4" exits that have 4" diameter diaphragms).
300 Hz is going to be tough to accomplish with a compression driver (that extends to 18 kHz). Particularly with respect to horn-size (..which starts becoming HUGE). It's not impossible, but it will be very difficult.
500 Hz..and higher - yeah, that's realistic. (..though a good horn/waveguide will still be large).
I prefer wider dispersion for a horn/waveguide - which tends to result in a larger sound-stage presentation. Here is the horn/waveguide I'd suggest:
Fiberglass SEOS-24? - The SEOS? Waveguides DIY Sound Group
From there it's about choosing your compression driver in the 1.4" to 1.5" exit grouping.
I like several of the 18 Sound drivers for their diaphragm material + suspension type + reasonably well-controlled impedance.
The single driver with the most "band for the buck" IMO would be the ND1460A, which can be purchased for as little as $330 US each in either the 8 ohm or 16 ohm versions:
18 Sound HF Compression Drivers
The Radian 745NEOPB is also very well received AND costs a bit less, but I've not seen its impedance profile. (..and the impedance profile could well cost you more in crossover components for correction than the difference in price between the drivers).
Also, as a general statement: the higher the driver's gauss the more "transparent" the driver relative to driver Mms and Sd. (..though transparency or extreme clarity is not always preferred).
This should mean that perceptually the 18 Sound 1480A is clearer than the Radian 745NEOPB, which is clearer than the 18 Sound 1460A.
Also, the larger the compression driver's diaphragm - generally the better it is at depth reproduction (..though usually with some resulting loss in treble dispersion). All 3 of the above drivers have 3" diameter drivers, however..
-there is also the newer Be driver from 18 Sound at only a little less than double the price of the 1480A with a 4" diaphragm (and in fact they have several others as well with 1.5" or even 1.4" exits that have 4" diameter diaphragms).
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Wow! The page-draw on this forum really sucks today..
Anyway,
Lowthers in horns add problems and reduce problems. The biggest problem is still the whizzer cone, no matter the loading or equalization, you can't "get around" that problem as a full-range driver.
On the other hand you might like it with proper equalization regardless (horns or not).
The only real solution is removing the whizzer and having it cross-over to a good tweeter at a properly low freq.. (..to something like Beyma's heil-type tweeter), with a good steep crossover. (..in fact, if the crossover is low enough and steep enough you wouldn't need to remove the whizzer.)
Still, if you are contemplating that there are better solutions available for less money.
Anyway,
Lowthers in horns add problems and reduce problems. The biggest problem is still the whizzer cone, no matter the loading or equalization, you can't "get around" that problem as a full-range driver.
On the other hand you might like it with proper equalization regardless (horns or not).
The only real solution is removing the whizzer and having it cross-over to a good tweeter at a properly low freq.. (..to something like Beyma's heil-type tweeter), with a good steep crossover. (..in fact, if the crossover is low enough and steep enough you wouldn't need to remove the whizzer.)
Still, if you are contemplating that there are better solutions available for less money.
Hi Santiago
If you're going to cross as low at 400Hz - 500Hz, I would suggest you go for at least an 2" compression driver. Have a look at Lynn Olson's 'Beyond the Ariel' thread (the last 20 - 30 pages), and read his comments in this regard. He says he would not a 1" compression driver (on a horn) below 1kHz. Just a thought.
Deon
If you're going to cross as low at 400Hz - 500Hz, I would suggest you go for at least an 2" compression driver. Have a look at Lynn Olson's 'Beyond the Ariel' thread (the last 20 - 30 pages), and read his comments in this regard. He says he would not a 1" compression driver (on a horn) below 1kHz. Just a thought.
Deon
It is not that they can't do it, it is that they will sound 'strained'. They lack the easy dynamics of the 2" drivers. Read in that thread I mentioned. To use a simple car analogy: you can do 85mph on the highway in a small car with a 1000cc (1-liter) engine, but the engine be screaming its guts out! OTOH, doing 80mph in something like a 2-liter BMW will be a breeze. Sorry for the car analogy, but my point is, just because it can do it does not mean you should. You're too close to the limits of its workable range. YMMV.
Deon
Deon
Deon, I believe the 1.4 and 2" exit BMS drivers are virtually identical except for the exit. Basing a driver's capability by it's exit size is as vague as your car analogy since there are more important factors such as VC diameter, etc...
http://bmsspeakers.com/fileadmin/bm...1-04_coaxial_neodymium_compression_driver.pdf
http://bmsspeakers.com/fileadmin/bm...1-04_coaxial_neodymium_compression_driver.pdf
My horn is a custom designed tractrix, an Eliptrac 400, 2", good to at least 400. Perhaps even 350. I tried a 2" Radian 950PB, but it falls off fast after 7500, needs lots and lots of EQ to boost. I sent it back for a 2" B&C DE-750TN-8. Works like a charm to 350 for me with my TDM 24CX active crossover with 24 dB/octave LR topology.
However, like any two-way, HF begins to beam a bit. It does work nicely, but my preference is a true three-way crossed at 3500.
However, like any two-way, HF begins to beam a bit. It does work nicely, but my preference is a true three-way crossed at 3500.
Rather than arbitrarily picking a number like 300 or 500 Hz out of thin air, I would look at the underlying driver techologies and decide what kind of sound you like. No matter how much you equalize things, you are not going to make a Lowther sound like a compression driver, or vice versa.
As a result of diaphragm materials and the use/non-use of a phase plug, they work differently, and have different tonal and dynamic qualities.
Aside from sonic considerations, each technology has intrinsic, physical limitations. The whizzer cone of the Lowther (or the Feastrex) has a very rough mechanical crossover in the 2~3 kH region, and the whizzer itself is not a good acoustical match to the throat of the horn ... the wave it emits is far from a plane wave, and horn theory demands a uniform wavefront for the horn to work correctly. Any wavefront non-uniformities present at the throat will be greatly magnified by the time it exits the horn.
The drawback of compression drivers is they do not tolerate being crossed over too low; much more so than direct-radiators or cone drivers working into front horns. If you try and "push" a compression driver too low, you'll get harsh, gritty, one-dimensional PA sound. Move the crossover a half-octave higher (and steepen the slope to 4th-order), and the sound clears up, with all the grit going away. In subjective terms, it goes from "bad PA" to "good electrostat" with the crossover safely above the danger zone.
This means the Lowther works quite happily into very large horns with 300 Hz or lower cutoff, but the sound gets murky and confused in the 3 kHz and above region. Musically, though, it sounds pretty decent, with good tonal values ... the usual virtues of a good paper cone allied with an Alnico magnet. It doesn't sound like a compression driver; it sounds like a very large Lowther with generous dynamics. Keep in mind that folded backhorns and straight front horns are two very different things, and do not sound the same.
By comparison, a large-format compression driver provides ultra-transparent sound and shockingly wide dynamic range. At times it even sounds like it is exaggerating dynamic range, something you don't hear with cones or electrostats, which subtly compress dynamics. But ... even a large-format compression driver is restricted to a 700 Hz to 500 Hz crossover, depending on horn size and the type of diaphragm suspension. (Modern Mylar suspensions require higher crossovers; take the manufacturers lowest recommended frequency seriously.) Old-school phenolic diaphragms can operate down to 300 Hz if the horn is large enough; on the other hand, phenolic starts to fade above 3 to 5 kHz, so there's a tradeoff in terms of usable frequency range.
Audiophiles are greedy and want to "stretch" compression drivers to frequencies lower than the manufacturer's recommendation. This has results similar to taking a car over the RPM redline; don't do it if you want it to last and sound good.
In terms of my own preference, I tend to choose higher crossover frequencies than other folks in the industry, because I like the sound of unstressed drivers, and am very sensitive to the sound of a driver that being pushed too hard in the LF region. I'm also willing to take them a bit higher, and use them in the HF range where they're starting to fade out, or become directional. This is strictly personal preference, though, and everyone hears things differently, so the choice is always up to you.
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A quick google search of: "Lowther measured", provides several different measurements for Lowthers.
Note: when looking at them always be aware of the freq. scale, measurement axis, the use of a test baffle vs. a box baffle - with baffle-step loss, and the reference input vs. distance measured.
Note: when looking at them always be aware of the freq. scale, measurement axis, the use of a test baffle vs. a box baffle - with baffle-step loss, and the reference input vs. distance measured.
I use Jbl 2482' s to get down to 330Hz on my 200Hz tractrix horns.
I have also used BMS 4596 down to this too.
They will not play so high high as discussed here, I have measured them and the jbl's behave well to 6KHz.
I cross them at 1200 as I have Vitavox S2 above that and then Raal lazy ribbons above that.
I've always found you run into probs trying to get too wide a freq range out of each horn...
I prefer the sound of compression drivers used like this to anything else I've heard.
I have also used BMS 4596 down to this too.
They will not play so high high as discussed here, I have measured them and the jbl's behave well to 6KHz.
I cross them at 1200 as I have Vitavox S2 above that and then Raal lazy ribbons above that.
I've always found you run into probs trying to get too wide a freq range out of each horn...
I prefer the sound of compression drivers used like this to anything else I've heard.
3way, with 2 compression drivers
are there any horns/waveguides designed for two drivers ? ... two throats into one waveguide/horn
... now I'm tempted 
3way, with 2 compression drivers
are there any horns/waveguides designed for two drivers ? ... two throats into one waveguide/horn
Tom's Unity does this..
Honestly I don't see much of a problem just using a chunky paging horn for the mid-range with one coupling insert (as opposed to the Unity's 8) away from typical horn entrance (..which would be for the treble driver).
Most mid. paging horns have enough treble loss on their own that it shouldn't be a problem (..as a cavity resonance from the mid. driver's position further toward the horn's exit).
At most I think the issue would be mild problems associated with the mid.'s entrance-hole and the treble driver's interaction with it. (..and even then the typical "bug-screen" on the mid. driver isn't leaving an entirely exposed 1" hole).
Here you can see the Unity's 8 holes:
Unity Horns - AudioKarma.org Home Audio Stereo Discussion Forums
Instead it would likely be just one hole centered on the lower panel of the horn's walls (but similarly near the treble entrance hole).
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