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Treble range : compression driver vs others
Treble range : compression driver vs others
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Old 1st May 2017, 05:00 PM   #1
Eldam is offline Eldam  France
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Default Treble range : compression driver vs others

Hi,

Is there any advantage of a horned compression driver for the trebles at an average civilsated listening volume of 75/80 db spl ? (domestic environment)

Does the compression driver/horn combo winns on some trade offs like :

better micro dynamic over a ribbon/esl/planar or dome tweeters ? Or better macro dynamic (huge spl difference between two notes)

Less distorsion when dynamic occurs (increase of SPL during peaks demands)

Or just different patterns between the types of transducters due to their shapes and/or hability to have less stress in their low end (XO cut choose) ? So more a choice because the room (size, sound balance) ?

We often read than ribbon owners find their tweeter is the nearest from the reality, is it all about the average spl volume we play at home ? Question is not inocent (or maybe it is ?!) as for instance for the same low average volume, compresson drivers will need more attenuation, i.e. greater résistor values (more distorsion ?).

But the trade offs of your amp (sensibility of the speaker as a choice factor for the amp), what gave you the best results for trebles (> 1500 Hz)

I'm often surprised to see than ribons owners, dome owners, compression drivers owners seem almost unreconcilable ?!

Last edited by Eldam; 1st May 2017 at 05:03 PM.
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Old 1st May 2017, 07:51 PM   #2
ScottG is offline ScottG  United States
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It's often a matter of freq. range.

(..there are of course operational reasons for each preference with objective results.)



Subjectively in general:

The lower the mms AND mechanical damping (particularly the surround), the greater the apparent detail.

HOWEVER,

With lower mms you end-up with lower force/"dynamics" and "imaging" that is less "3D" (..though this depends quite a lot on how the amplifier works with the driver and crossover components - if any).


You'll often see enthusiasts that are using compression drivers for upper-mid lower treble, also using (crossing-over to) Ribbons/Electrostats/Heil-AMT for the upper treble range. Part of this is often to increase the pressure off-axis horizontally (..assuming they aren't horn-loaded as well), BUT it's also done to improve detail reproduction. The compression driver in-turn generally provides more "body" and "dynamics" in the upper midrange and lower treble (irrespective of amplifier) while NOT providing the last "word" on apparent detail at higher freq.s.


Freq. range is a huge factor for any given design (both objectively and subjectively). When you say something like >1500 Hz I automatically think dome tweeter (..and it's really more like >2000 Hz).
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Last edited by ScottG; 1st May 2017 at 07:57 PM.
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Old 1st May 2017, 09:31 PM   #3
Eldam is offline Eldam  France
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Wow, quite interresting !

I understood something near but without enough experience to abstract any conclusion. There is too much dependancies between the stuffs which are often designed standalone. Which push us to tweaking to make our mixed devices sounding more coherent.

I see a great, avenir, futur, for the whole designed stuffs : daced, Amped speakers ! It will talk more about brands capabilities and savoir-faire, but at least less liberty in our hobby.

If this time, taking a standalone dome driver above 2000 Hz (you are true, so few can be crossed lower), dome should be a winner taking all the trade offs (less filter and passive parts) or regarding just the sounding result : does a mix of drivers could subjectivly a greater accuracy like your good illustration of mixing several technologies where they are the most likely to sucess. For instance here the ribbons above 8K/10K Hz and Something else at the bottom where a different patern and more air needs to be moved ?

Of course difficult conversation (at least for me) as : there are topologies as you said : amps, passive parts or not...

In the real world i know few brands who are making with success a whole great hifi system from A to Z; maybe Bang&Olufsen, but mixed combinations seem to go further in sound quality !

Maybe my question was bad, it's maybe bad to beginn from a particular device (here the tweeter) to targett a holystic result (sound reproduction) because the dependencies you pointed out ?! I did management project, but there are so much subjects and different knwoledge areas about hifi reproduction than the task seems often...dificult (very) in relation to the result (having Something sounding musical and right enough in non standardized listening rooms)!

Last edited by Eldam; 1st May 2017 at 09:36 PM.
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Old 1st May 2017, 11:04 PM   #4
ScottG is offline ScottG  United States
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Well, a *good* dome tweeter generally provides a better subjective result with a crossover in that all important operating freq. range of 1-7.5 kHz. (..with a crossover typically between 1800 and 2800 Hz - usually depending on how steep the high-pass filter is for the tweeter.) ..and this is with respect to normal input-levels/domestic use.


Getting a truly fantastic result however, often involves other technologies.

Ex. (compression driver vs. dome)

A really nice large format aluminum compression driver (3" with 2" exit) between about 800 Hz and 5 kHz with the right type of waveguide *can* substantively improve (subjectively) on what a *good* tweeter can provide. (..it can also improve some characteristics of objective quality as well like non-linear distortion, though other objective qualities can suffer as well.) BUT it can also be a royal pain trying to get good integration with superior super-tweeter (..and not necessarily easy getting good integration with the lower midrange driver either).

Despite that, a really excellent dome tweeter(s) in an unusual configuration might still exceed that subjectively over the same freq. range.

-It really depends on the design.



IMO though, I would generally NOT choose a compression driver - at least not unless I needed really high output (..which really isn't "Hifi"), or extreme efficiency (..*over* 100db at 1 watt).

Even if I needed good efficiency (a bit less than 100 db), I'd look to other design choices (..like maybe an array of dome tweeters in combination with an efficient ribbon super tweeter - even though I'd loose some of that force/"dynamic" sound).
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Old 1st May 2017, 11:10 PM   #5
ScottG is offline ScottG  United States
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On the subject of good tweeters:

http://www.diyaudio.com/forums/multi...ml#post5060907
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Old 2nd May 2017, 05:51 AM   #6
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Eldam View Post
better micro dynamic over a ribbon/esl/planar or dome tweeters ? Or better macro dynamic (huge spl difference between two notes)
A compression tweeter is good for attaching to a waveguide which gives you the pattern you need. The downside is size, cost, setting up including equalising/crossing. Then, they sound the same at very quiet levels as they do loud and this is important.
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Old 2nd May 2017, 07:52 AM   #7
chris661 is online now chris661  United Kingdom
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The way I see it...

- Ribbons tend to be fragile and light-weight. They'll extend very well past 20kHz, but tend to suffer if driven low or loud due to their very limited Xmax
- Compression drivers are happy going loud and (if their design allows) often quite low. The ones that go low will get ragged above 10kHz, though.
- Domes are, IMO, a happy medium. They'll usually get to 20kHz just fine, and some of them will go pretty low.

There are sub-sets like ring-radiators and AMTs, but I'll leave it up to the reader to figure out where they sit.

Chris
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Old 2nd May 2017, 10:11 AM   #8
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by chris661 View Post
Compression drivers ..... The ones that go low will get ragged above 10kHz
It's typically the phase plug that causes a ragged response. A larger driver could have a phase plug that works to 20k. Larger drivers can be less useful due to lower efficiency at the top end, but a 1" compression driver can cover from above 10k to below 1k in a domestic situation. Below this is less critical and more tolerant of a crossover arrangement, probably making things easy enough to call it, IMO.
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Old 2nd May 2017, 11:31 AM   #9
TBTL is offline TBTL  Germany
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If only looking at dispersion:
  • Soft domes have both wide (180 deg) horizontal and vertical dispersion but they narrow above ~5 kHz. This is because at those high frequencies, the centre and circumference of the dome do not move in phase any more. Ring radiators exhibit approximately the same dispersion pattern.
  • Hard domes can hold their wide (180 deg) dispersion up to a slightly higher frequency than soft domes, as their domes move in phase up to above 20 kHz.
  • Ribbons usually are narrow, so they have the same wide (180 deg) horizontal dispersion as domes. As they usually are tall, they have a narrow vertical dispersion, which decreases as frequency goes up. Some people say that a wide horizontal and small vertical dispersion is good. If I understand the book 'Sound Reproduction' by Floyd Toole correctly, this is because lateral reflections add spaciousness, while reflections coming from above and below do not add much of this. Floyd Toole however appears to favour a constant beam width. As for why some people like narrow vertical dispersion: my own interpretation is that reflections coming from above and below decrease clarity.
  • Dispersion of compression drivers is determined by the horn, which can be anything. Usually horn designers strive for constant horizontal beam width and either constant or decreasing (with increasing frequency) vertical beam width.
Wide (180 deg) dispersion causes first reflections to happen within a few ms of the direct sound. If you want to avoid that, you need a dispersion of say 90 degrees. Then horn loaded compression drivers or other drivers with a deep waveguide are the only options.

Quote:
Originally Posted by Eldam View Post
Question is not inocent (or maybe it is ?!) as for instance for the same low average volume, compresson drivers will need more attenuation, i.e. greater résistor values (more distorsion ?).
Compression drivers indeed require a lot of padding. Resistors are close to perfect in loudspeaker applications, so fortunately this does not add a significant amount of distortion if you do it after the amplifier.

Last edited by TBTL; 2nd May 2017 at 11:36 AM.
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Old 2nd May 2017, 12:29 PM   #10
chris661 is online now chris661  United Kingdom
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Quote:
Originally Posted by AllenB View Post
It's typically the phase plug that causes a ragged response. A larger driver could have a phase plug that works to 20k. Larger drivers can be less useful due to lower efficiency at the top end, but a 1" compression driver can cover from above 10k to below 1k in a domestic situation. Below this is less critical and more tolerant of a crossover arrangement, probably making things easy enough to call it, IMO.
I thought it was the 3" diaphragm going into breakup modes above 10kHz. It'd explain why aluminium diaphragms measure differently to titanium, phenolic, beryllium etc etc.

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