The Official HORNLESS Compression Driver Thread

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#89
JonBocani said:
I jumped outside of the box, then i took the bull by the horns.
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It is always good to see people trying unconventional approaches as sometimes they can lead to good outcomes.

There are two main reasons why horns are used particularly with compression drivers, to help match the impedance which usually gives a boost to the low end response and/or to get some directivity and pattern control.

Directivity is an important factor in speaker design which more people are paying attention to now. Reduced room influence from narrower directivity is also another factor.

It would be quite helpful and will probably reduce the number of "that won't work" type posts if you could take some actual measurements of the drivers in your baffle.

Frequency and polar response plots (with and without EQ) would be good data. People can then see the response and get a better idea of the directivity to see if hornless is worth trying.

There have been many threads where ideas have been shouted down initially. The best solution is to provide data in the form of measurements if you are able to.
 
#90
JonBocani said:
Correct me if i'm wrong, but the PA people are expecting 140-145db (1m distance) at max (sustainable) wattage from those CDs...
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Your estimate is rather high.

Most companies state about 110dB per watt and 100 Watts AES Standard for their best 2" compression drivers, so 130dB on a horn is the most I'd expect for max sustainable SPL. I'm not sure how much de-horning would reduce this by, 10 or 15dB seems about right to me.

The highest vaguely believable sustained SPL spec I've seen is for the 4592-mid:

"max. SPL (cont.) 136 db at 150 W"

Complete pro audio boxes have limits usually well below the ~130dB that the HF driver would set. For example, the SH50 states:

continuous output 127 dB SPL
SH50 | Danley Sounds Labs | Danley Sound Labs, Inc.
 
#91
I vaguely remember someone trying to sell speaker systems with a hornless compression driver.

...maybe a decade ago?

It was a 2-way with TAD HF drivers. If I recall correctly, each channel used a single big woofer in an unstuffed box. The box was basically a fridge: a laminate of MDF and aluminium. I remember lots of adjectives, but not a lot of measurements. I guess they didn't become the next big thing.
 
#92
Ooh, another 'blast from the past'! Some folks were using Altec 1" compression drivers with just a 3/4" baffle thickness flare and the 1.4" with 1.5" back at least to the early '60s. I've periodically recommended this on HE forums since they're great for HIFI apps.

There's been some high end consumer offerings in recent decades, but don't recall the details or if they're still around.

GM
 
#96
Here is a Japanese DIY'er using naked CDs with back cover removed:

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#97
frangus said:
AudioRoundTable.com: Pi Speakers => HF Compression driver without horn flare?
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:up:

Here some quotes from the post:

Hi Guys, I am the designer of the Model 16 loudspeaker system.
The question has been raised about our choice to use a compression driver without a horn. Well, firstly it must be realized that, as Wayne rightly states, a horn is a device that directs acoustic energy.
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Yes, basically the horn function is to direct, to concentrate acoustic energy. As little waste as possible on the sides, on the floor and on the ceiling (if any! ...outdoor PA, eh...)

But what if... What if i'd like some ''waste'' on my room's walls, floor and ceiling ? What if that helps achieve a more immersive audio experience ?



Now, if we start to bend the walls of this baffle forwards into a horn, the magnitude of the loading increases. So now we can see a simple relationship forming, the longer the horn walls the lower the frequency the loading will be maintained to, and the tighter the angle the greater the "severity" of that loading. Now, just to make things a little more interesting, the tighter the angle the more the horn resembles a pipe, and of course pipes have resonances at discrete frequencies, and so it occurs that these resonances also "load" the driver and there will be specific centre-frequencies of peak loading. Once you understand all this you realize that short horns will provide very little loading below what will inevitably be a fairly high cut off frequency.
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The higher the frequency, the less a horn-loading is needed/effective. Therefore, the big challenge here is about 400hz-1khz or so. YES you lose potential output (efficiency and max SPL), but then again if it's for domestic Hi-Fi it's mostly irrelevant. Only the possible damage of the diaphragm is the real concern here. Especially if EQ is used.


Now, as a consequence of loading, the on-axis sensitivity of the loaded frequencies is increased, and this allows the possibility of electrical filtering or attenuation of those frequencies because now we may have a little extra acoustic energy to burn. Hence, in theory we can reduce the excursion requirements of the driver over the loaded frequencies, and hence the idea that loading ultimately helps to protect the driver.
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Protection of the driver (diaphragm) seems to be the issue here, NOT the subjective qualities. As long as you get the undistorted SPL you need for a given bandwith, with directivity properties that suits your needs... What else matters ?

It is also true that the loading itself reduces driver excursion; the extent to which this happens is dependant on the magnitude of the loading.
In the case of the Model 16 however, it is first and foremost a domestic hifi speaker rather than a PA system or studio monitor and as such it was never intended to be foolproof under the wild dynamic demands of uncompressed live instruments common to those environments. When used sensibly in near-field domestic situations it is more than capable of providing satisfying SPL without exploring the maximum safe output levels of the compression driver.
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Precisely my point, and it's a solid argument against what i see as the single worst downside of using an hornless-CD config in a domestic HiFi system (over-excursion potential, damage of the diaphragm, ...)

The TAD4001 driver is rated at 30W with the TAD recommended filtering and assumed horn loading. It has an efficiency within the meat of its pass-band of 110dB per watt at one metre. So even with a tiny current flowing through its coil this driver is capable of sufficient safe output for me. We chose the 4001 driver for its sonic presentation…its tone…its musicality. We wanted to design a system that delivers a particular musical message, rather than a system that will impress people who want explosions or faithful recreations of space shuttle launches. Having a pair of Model 16s facing you at 1.5m in a quiet lounge room is like driving a 400hp car around town…you don’t ever really use the full wack…well…at least I don’t with the type of program material I listen to.
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The Radian 950PBbe is very similar to the TAD4001. In fact the Be diaphragms (Truextent) are used as TAD's replacements very often.


Finally, we feel that there are some very real subjective virtues that we have been able to manifest by avoiding a horn
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Yes, without a doubt.
 
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#100
using an CD without an horn is like driving a car without wheel , sure you can drive on the brake disc , but man it's realy hard !!!.........kidding !!

the fact is that you like it !! ,like we say here in France : every taste are in the nature ...

;-)


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