I have seen many favorable reviews of speakers using kompression drivers, so I wonder why its not more widely used in hifi speakers. Is its because of cost compared to domes and other COMMON types of drivers, or do they have disadvantages soundwise?
Actually Ive always read a "CD" as a compression driver, but I just found out that its (also?) used as controlled directivity or constant directivity.
Actually Ive always read a "CD" as a compression driver, but I just found out that its (also?) used as controlled directivity or constant directivity.
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A compression driver has to be horn loaded and the shape and size of the horn affects the sound quality.
The high efficiency of the combination is put to good use in pro audio systems as it plays louder than a dome tweeter.
The drawbacks of compression/horn drivers include:
The high efficiency of the combination is put to good use in pro audio systems as it plays louder than a dome tweeter.
The drawbacks of compression/horn drivers include:
- Affordable ones can be fatiguing to listen to.
- They add non-harmonic content to the sound.
- They can be more directional than dome tweeters.
- Blending them with conventional drivers can be problematical.
Yes I thought that the use widespread use in pro audio would have to do with efficiency. On the other hand pro audio was earlier very expensive, so I gathered they used CDs cause the cost of the rest of the system would justify it.
Yes, good compression/horn drivers are expensive, but justifiably so in the pro audio context.
I don't pretend to be an authority on horns, and I expect the experts will chip in shortly!
I don't pretend to be an authority on horns, and I expect the experts will chip in shortly!
Actually, no. I have had positive experience with unloaded compression drivers. In my opinion Compression driver on its own has little to no drawbacks. But also little to no benefits over well engineered domes. Application as always does matter.
The biggest problem is their high sensitivity which can exaggerate noise coming from the setup in quiet domestic environment. They tend not to like inefficient domestic midbass drivers as companions. And yes, method of dealing with their radiation (shaping or coupling wavefront coming from throat) is the biggest factor of performance characteristics.
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No Choice
A horn loaded compression driver operated at a low level in a domestic venue has no competion from the avaiable alternatives. In a commercial venue there are no alternatives to consider. For the purpose of this discussion, design excellance is assumed. WHG
A horn loaded compression driver operated at a low level in a domestic venue has no competion from the avaiable alternatives. In a commercial venue there are no alternatives to consider. For the purpose of this discussion, design excellance is assumed. WHG
Hi,
mind You ..... at least in a domestic environment and say up to ~110dB a well designed ESL-, and even Ribbon-hybrid, outperforms horns easily.
But that's just another opinion ;-)
jauu
Calvin
mind You ..... at least in a domestic environment and say up to ~110dB a well designed ESL-, and even Ribbon-hybrid, outperforms horns easily.
But that's just another opinion ;-)
jauu
Calvin
Another disadvantage of compression drivers is that a few reach 20 kHz and that most of the 10 - 20 kHz is diaphragm resonance anyway. These resonance peaks of metal diaphragms can be fatiguing. A parametric equalizer can (somewhat?) fix this.
If you mean harmonic distortion: yes but only at pro audio levels, at which the throat SPL is such that air is no longer a linear medium. At domestic SPL's the distortion can be low.
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Edit to OP sorry 🙂
Im Quite attracted to ribbons, AMT and other exotics, but I was mostly thinking about CDs compared to more common and widespread types of tweeters. Therefore I edited the OP - Not that exotics are unwelcome in the thread 🙂
I dont know; Maybe in some senses, but I imagine whatever is compressed will be decompressed before reaching our ears.
All an EQ would do is raise or lower the level of the 10-20kHz band. It's still mostly diaphragm bell-modes and other resonances.
The compromise of HF extension vs LF extension goes like this:
- Large diaphragms mean you can increase output or reduce excursion (ie, lower distortion), but the larger the diaphragm, the lower in frequency the resonances start.
- You can't use a smaller diaphragm with lots of excursion because the phase plug and space in front of the diaphragm form a low-pass filter. Increasing the space between diaphragm and phase plug will lower the frequency of the low-pass filter.
FWIW, I'm a live sound engineer and designed and built my own PA system (DIY stage monitors coming soon!). The HF drivers are 18Sound ND1460 on RCF HF94 horns (one per side). I get to around 14kHz, but loud enough to do this: YouTube
Where the stacks were putting out 135dB peaks.
It'd be nice to get all the way up to 20kHz, but at live SPLs, nobody has noticed yet.
As you can imagine, distortion at home HiFi levels will be exceptionally low, and if you find you're missing the last few kHz, it's easy enough to bring in a super-tweeter.
For small-format applications (I'd include home HiFi here), a 1" driver will probably do what you need, and it's possible to push them pretty low.
Titanium diaphragms are surprisingly resilient - I found this out the interesting way when someone was demonstrating some new amplifiers with my speakers, and managed to somehow bypass all crossovers. The HF units saw a few hundred watts of low-frequency signals, and came out just fine.
For bigger and louder systems, 1.4-2" exit drivers with 2.5-4" diaphragms are the way to do it. In the video above, the crossover was 1.2kHz.
For the biggest systems, there are ways of getting lots of HF units working together. See Danley, line arrays, etc etc.
Chris
In terms of classical mechanics, any applied force to an object will cause deformation. The work done corresponds to the magnitude of the deformation, and is equal to force applied times the distance moved. In order to increase efficiency, distance must be shortened and a more compressed state implies exactly that.
High efficiency = high distortion
Zvu, right?
High efficiency = high distortion
Zvu, right?
I've only used one cd (1" 18sound tin coated titanium). It was very dynamic and clean but I needed to use two notch filters to achieve a good frequency response, and even then the last octave dropped away quite rapidly (quite different to the published 18sound response graph) so lacked a bit of 'air' in the highest frequencies.
My understanding is "if it moves, it distorts". Therefore ALL speakers produce distortion right?
Take a compression driver and now, you can get the same output with much LOWER movement, hence distortion.
I think (but do not pretend to know) the trade-off is extension. You start to band limit the range of the driver when you add a horn to the front of it.
The last time I really heard some ESL's, they were NOWHERE near as loud as 110 db's and you could literally see the deformation of the membrane during low passages.
(dislaimer: I have and like horns)
My horns are 'around' 105 db/watt so can hit and blast through 110 db's without much of a sweat....
If you want sound "on the scale of life" with dynamics out the wazoo, then horns are about the only way (I've found) to get there.
The nice thing is.... they will also play just as quietly as any other esoteric speaker you wish to compare them with (just like any Ferrari will drive 20 mph to get a loaf of bread)
Take a compression driver and now, you can get the same output with much LOWER movement, hence distortion.
I think (but do not pretend to know) the trade-off is extension. You start to band limit the range of the driver when you add a horn to the front of it.
The last time I really heard some ESL's, they were NOWHERE near as loud as 110 db's and you could literally see the deformation of the membrane during low passages.
(dislaimer: I have and like horns)
My horns are 'around' 105 db/watt so can hit and blast through 110 db's without much of a sweat....
If you want sound "on the scale of life" with dynamics out the wazoo, then horns are about the only way (I've found) to get there.
The nice thing is.... they will also play just as quietly as any other esoteric speaker you wish to compare them with (just like any Ferrari will drive 20 mph to get a loaf of bread)
Cost, size, aesthetics and ignorance.
A good compression driver speaker requires a horn and perfectly executed filters. If done wrong it can sound very bad . They are large and mostly condemned by the conditioning of the audio magazine 'experts' and people that have never had a well done horn system.
They are not for everybody or every situation. A full range horn loaded multi-way system is probably the ultimate if you can fit it in your room and afford one done right.
That would maybe be the case if the compression was the biggest contributor or only thing that leeds to driver distortion - but it obviously isn't so saying that compression=distortion is the same as saying thermal compression=distortion. Untill we get to that point where it is a big contributor, there are much more variables that influences total harmonic distortion of any driver - compression driver or otherwise.
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