I just thought it was a good idea to make sure that a manual measurement was in agreement with DATS?
Was it?
//
The beaming is a well-known phenomenon and needs no further explanation.
Throat (versus horn length) related distortion is a more complicated subject.
There is second-harmonic distortion in an exponential horn as a function of the intensity at the horn throat with the ratio of the frequency to the cutoff frequency as parameter.
This is explained in Beranek's book (see attachment) and has been studied by, among others, Holland & Newell.
Since this distortion is only manifest at very high SPL and is also drastically reduced at the horn mouth, it's most likely not something to worry about.
However, as noted in Markaski's thesis a.o, the match between driver and horn also affects interferences between diaphragm/phase plug and horn throat.
IOW some drivers work better with a long (low-T) horns than others.
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In addition, from Holland & Newell's extensive research:
Twenty mid-range loudspeakers formed the test examples in a listening test conducted as part of a three-year project on mid-range horn loudspeakers.
Some of the aims of the test were to find which, if any, of a range of horns sounded similar to example direct-radiating loudspeakers and what physical characteristics make a horn sound like a horn. Measurements were taken of the frequency response functions of all of the loudspeakers and comparisons were made between these measurements and the listening test results. The power cepstra of the loudspeakers were calculated as above and, when compared, were found to reveal many clues as to the similarity or otherwise of the sound of the different loudspeakers. For example, it was discovered that the shorter horns sound more like the direct radiating loudspeakers than the long horns, and this was found to be due to the reflections from the mouths of the short horns occurring at around the same time as those in the cones of the direct-radiating loudspeakers; the reflections from the mouths of the long horns occur later and contribute to the characteristic 'horn sound' even though they are generally lower in level than those of the short horns.
During the same hom research, a flare mismatch at the throat of one of the horns when attached to a particular driver was found to be the cause of response irregularities. Cepstral analysis revealed quite strong reflections from the discontinuity and when the horn was attached to another driver both the spikes on the cepstrum and the response irregularities disappeared.
Twenty mid-range loudspeakers formed the test examples in a listening test conducted as part of a three-year project on mid-range horn loudspeakers.
Some of the aims of the test were to find which, if any, of a range of horns sounded similar to example direct-radiating loudspeakers and what physical characteristics make a horn sound like a horn. Measurements were taken of the frequency response functions of all of the loudspeakers and comparisons were made between these measurements and the listening test results. The power cepstra of the loudspeakers were calculated as above and, when compared, were found to reveal many clues as to the similarity or otherwise of the sound of the different loudspeakers. For example, it was discovered that the shorter horns sound more like the direct radiating loudspeakers than the long horns, and this was found to be due to the reflections from the mouths of the short horns occurring at around the same time as those in the cones of the direct-radiating loudspeakers; the reflections from the mouths of the long horns occur later and contribute to the characteristic 'horn sound' even though they are generally lower in level than those of the short horns.
During the same hom research, a flare mismatch at the throat of one of the horns when attached to a particular driver was found to be the cause of response irregularities. Cepstral analysis revealed quite strong reflections from the discontinuity and when the horn was attached to another driver both the spikes on the cepstrum and the response irregularities disappeared.
Mismatch/irregularities/discontinuity is well known, so there is little new here.
Furthermore, not everything mrs Newell and Holland wrote should be taken for science: the whole cepstral analysis of loudspeaker does not yield any (new) info that is not already present in the impulse response of a single point in space, i.e the measurement point. It tells us nothing about off axis behaviour.
It is not a surprise -to my best of knowledge- no one else has followed suit with cepstral analysis: a basic CSD will yield the same info.
Furthermore, not everything mrs Newell and Holland wrote should be taken for science: the whole cepstral analysis of loudspeaker does not yield any (new) info that is not already present in the impulse response of a single point in space, i.e the measurement point. It tells us nothing about off axis behaviour.
It is not a surprise -to my best of knowledge- no one else has followed suit with cepstral analysis: a basic CSD will yield the same info.
I once bought four small drivers where three were perfect and one seemed to be faulty, with an undercharged magnet (0.38 Qts vs 0.6 Qts).
The shape of the frequency response plot was exactly the same, the only difference to response was that the faulty one was about 1.5dB quieter.
Measurement shown here:
Midrange (cone driver) horns; low relevance of magnet strength and Qts
The bulk of their research dates back to the early 1990s.
Since then, much progress has been made, not only wrt lab simulation technology (processing power) but also in the field of measurement techniques.
Their extensive research into the perceived differences between different horn types is unparalleled to this day.
It is precisely the practical implications of their findings that are useful to the DIY community.
For example, a deeper horn is preferably combined with a horn-loaded radiator, because the wave fronts match more closely.
As a result, the system sounds (naturally) much more homogeneous.
There is a reason why fully horn loaded high end loudspeakers have been gaining popularity over the past 10-15 years. Examples are BD-Design, Cessaro, Tuna Audio and the Living-Voice Vox series.
Likewise, many people still prefer single-ended tube or class A(B) transistor amplifiers over the best Class D designs.
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Looking at 700hz...unless its due to the filter... its pretty clean yet. The horn is slightly cleaner than the woofer, decay wise. Not drastic....yet if the the 700hz area is the cutoff of this horn, it is supporting a part of my idea that a horn, even at tuning, can compete with a dynamic radiator.
Well the underlying statement was pointing towards the idea that a bandpass system has more sound quality than a strictly sealed or vented enclosure. A synergy is a bandpass device. So we would be comparing the synergy to sealed or bass reflex/TL to make a point. Anyone have any CSD data on synergy or similar?
How about the measurements from an SH50 from Mr. Danley himself:
Upcoming Tom Danley Hifi speakers | Page 4 | Audio Science Review (ASR) Forum
Upcoming Tom Danley Hifi speakers | Page 4 | Audio Science Review (ASR) Forum
As a result, the system sounds (naturally) much more homogeneous.
Now that is precisely what I mean: that is journalism, not audio science. By what metric is "homogenous" defined? Toole, Olive, Geddes e.a. are shaking their heads in bewilderment.
But I will refrain from polluting this interesting thread.
Now that is precisely what I mean: that is journalism, not audio science. By what metric is "homogenous" defined? Toole, Olive, Geddes e.a. are shaking their heads in bewilderment.
But I will refrain from polluting this interesting thread.
You're kidding right?
Several fundamental acoustic principles underlie this comment.
One of those is mentioned in a post I referred to very recently.
"Naturally" implies some basic knowledge of horn physics.
Or ask the guy working on this concept if it might be based on journalism.
Several fundamental acoustic principles underlie this comment.
One of those is mentioned in a post I referred to very recently.
"Naturally" implies some basic knowledge of horn physics.
Or ask the guy working on this concept if it might be based on journalism.
Attachments
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Really?! A typical sealed, vented box is presumed to have a ~uniform particle density, i.e. homogeneous: Homogeneous | Definition of Homogeneous by Merriam-Webster