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The Preference for Direct Radiators
The Preference for Direct Radiators
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Old 3rd December 2018, 10:43 PM   #21
Patrick Bateman is offline Patrick Bateman  United States
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I heard the cheap Revels and the expensive Revels back-to-back, and the expensive ones disappear better. One of my theories is that the curved baffle of the more expensive ones helps with the 'disappearing act.'

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$22,000

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$3,500

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7.28" wide baffle, with sharp edges, and a dome tweeter mounted on a 135 degree waveguide

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9.28" wide baffle, with 1" roundover, and a dome tweeter mounted on a 135 degree waveguide

The part that's super interesting to me, is that the roundover improves the polars all the way to 10khz. I don't understand waveguides well enough to know why this is, but you can see it right there: the off axis response of the tweeter is improved, even at 5-10khz, and when the waveguide loses directivity control the beamwidth collapses slower than WITHOUT the roundover.

I found the same thing this month; I added a whopper of a roundover to an 18Sound XT1086, a full 3.5" on each side, and saw that the polars improved quite a bit.

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Augerpro's measurement of the XT1086, on a baffle

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Here's my measurement of the same, with a 3.5" roundover on each side of the waveguide
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Old 4th December 2018, 02:21 AM   #22
bbutterfield is offline bbutterfield  United States
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Quote:
Originally Posted by Patrick Bateman View Post
As I understand it, Harman has copied the power response and used it over and over and over again.

So it gives us some interesting data; if the power response of their speakers is nearly always the same, then why do the speakers sound different?
When I suggested matching the directivity, I didn't mean the directivity as a single number. I meant matching both the vertical and horizontal dispersion characteristics across the widest bandwidth possible. Some of those speakers you've pointed to may have the same power response, but how they get to that power response is quite different, and will sound different.
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Old 4th December 2018, 09:51 AM   #23
burgunder is offline burgunder  Denmark
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Originally Posted by kipman725 View Post
I long ago came to the conclusion that sofit mounting or in wall speakers are the way forward if you can have them.
Couldn't you get most of the benefits with on-wall mounting in a proper cabinet?
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Old 4th December 2018, 11:33 AM   #24
pblossom is offline pblossom  United States
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How far away from the XT1086 were the roundovers?
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Old 4th December 2018, 12:27 PM   #25
chris661 is offline chris661  United Kingdom
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I think there are several things at play here, most/all of them in the time domain.

NB - I'm into HiFi, but run a live sound business and do a bit of recording on the side.

First up, the short-time-scale-stuff:

Baffle width:
When a wave hits the sharp edge of a baffle, you get diffraction, essentially from the edge acting as a second source of sound. The narrower the baffle, the shorter the time delay, the less "smearing" of sound.
Large roundovers help a lot - they reduce diffraction at the source. Narrow baffles are a band-aid IMO.

Small delays are better than large delays below a few ms.


At longer time-scales, it more comes down to personal preference as well as the information on the recording.

I'd argue that recordings with little ambience of their own benefit from speakers that illuminate the room more.
Similarly, a recording taken with a pair of mics at the back of a concert hall would have loads of ambience recorded. No need for your listening room to add anything.

The result of that is that there are, arguably, two recording techniques and two matching reproduction techniques:

"They are here" - close mic techniques, little recorded reverb
"I am there" - distant mic techniques, plenty of recorded reverb included.

The former would probably require speakers that tend towards omnidirectional. They need to illuminate the room in the same way as actual musical instruments would.

The latter would need something like Synergy horns. Controlled directivity, with minimal excitation of the listening room. That way, you're not getting a weird overlay of recorded & room acoustics. You're just getting what was there at the venue.


I suspect the reason why people like direct radiators is that they do illuminate the room quite a lot. A very dry-sounding recording gets a bit of reverb, while a recording with plenty of reverb already just gets a bit more.

Some people will like the "precise" sound that you'll get from taking the room (mostly) out of the equation. Others will find close-mic'd recordings unnaturally dry.

Some people like open baffle speakers. I find the imaging a bit too vague - more like a watercolour picture than a photograph. It's probably because they're also throwing sound backwards. It could also be that most of the OBs I've heard have had fairly wide baffles.

There's definitely an amount of personal preference here. None of the approaches are a one-size-fits-all solution. I'd say direct-radiators are a decent middle-ground that will satisfy most people most of the time.

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Old 4th December 2018, 01:46 PM   #26
marco_gea is offline marco_gea  Italy
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Quote:
Originally Posted by chris661 View Post
I'd argue that recordings with little ambience of their own benefit from speakers that illuminate the room more.
Similarly, a recording taken with a pair of mics at the back of a concert hall would have loads of ambience recorded. No need for your listening room to add anything.

The result of that is that there are, arguably, two recording techniques and two matching reproduction techniques:

"They are here" - close mic techniques, little recorded reverb
"I am there" - distant mic techniques, plenty of recorded reverb included.

The former would probably require speakers that tend towards omnidirectional. They need to illuminate the room in the same way as actual musical instruments would.

The latter would need something like Synergy horns. Controlled directivity, with minimal excitation of the listening room. That way, you're not getting a weird overlay of recorded & room acoustics. You're just getting what was there at the venue.


I suspect the reason why people like direct radiators is that they do illuminate the room quite a lot. A very dry-sounding recording gets a bit of reverb, while a recording with plenty of reverb already just gets a bit more.

Some people will like the "precise" sound that you'll get from taking the room (mostly) out of the equation. Others will find close-mic'd recordings unnaturally dry.

Chris
Right on the money, methinks.

Bold emphasis indicates my own preference ;-)

Marco
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Old 4th December 2018, 04:07 PM   #27
bbutterfield is offline bbutterfield  United States
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When considering the abilities and deficiencies of the human perception of stereo playback, there are implications for what directivity a speaker should have. (And also implications for how recording engineers should approach their micing and mixing).

Since stereo speakers can create the perception of a sound coming from anywhere between them, we should allow the recording engineer complete control over this space. That means speakers should not cause reflections off the front wall.

Since humans have poor localization abilities in the vertical plane (elevation/depression of source), any sounds intended to come from a horizontal (azimuthal) angle between the speakers, but at a different vertical (elevation) angle can also be put directly into the mix. Again, we give the recording engineer control over this domain, and we avoid floor and ceiling reflections. There are filtering techniques that can cause the perception of elevation differences based on head related transfer functions.

There's little point to trying to re-create a sound just barely outside the span of the speakers, so those should be fully panned by the engineer, and speakers should avoid close sidewall reflections.

For sounds coming from far outside the span of the speakers, stereo is deficient in this domain. However, if the desired sounds are simply delayed versions of sounds in the mix, then sidewall reflections can fill in the void. We'll want them sufficiently delayed and coming from angles significantly separated from the span of the speakers. These wide-angle sidewall reflections are where listener preference comes in. Luckily, they have little impact on the perceived detail of the recording. Interference from an off-axis source doesn't degrade our ability to understand human speech as much as closer sources, due in part to a human perception ability called binaural unmasking. So if someone chooses to be enveloped with wide-angle sidewall reflections, they will still perceive and appreciate the finer details of the mix.
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Old 4th December 2018, 04:32 PM   #28
mitchba is offline mitchba  Canada
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Thanks for starting the thread Patrick!

Agree with Chris's assessment and my preference is the same as Marco's...

It does seem about one's preference to directivity...

The Preference for Direct Radiators-di-jpg

The 2 x 15" with 90 x 50 waveguide is the JBL 4722, which I use. The single 15" with 120 x 100 waveguide is the M2 and the cone and dome is the Salon2. From: https://www.avsforum.com/forum/89-sp...l#post54613040

The M2 and Salon2 are close in directivity, yet the Salon2 is the preferred speaker, at least in the shootout thread. Listening scores with 6 participants:

The Preference for Direct Radiators-listening-scores-jpg

And comments like this from one of the participants seem to confirm that it is about the directivity:

"My assumption/guess is mainly due to dispersion pattern and room interaction. The controlled directivity of the M2 will likely minimize that of early reflections in the room. The Salon2 would likely energize the room since its directivity control is dictated by the driver size. How else could one provide the perceived difference in spaciousness in a test like this?

My biggest take away is that Toole is likely right about people preferring certain types and amounts of reflections based on the recording. The M2 seemed to be preferred on the same tracks by our group. The Salon2 was preferred on the others. As shown by John, the track list provided a good amount of variation. I do not consider this test as a definitive statement. The next logical would be to do the same as a stereo pairing as this will bring some more of the room into the equation. Either way, this was a great experiment and one that I hope can become more common."

https://www.avsforum.com/forum/89-sp...l#post54630984
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Old 4th December 2018, 08:46 PM   #29
augerpro is offline augerpro  United States
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The simplest answer to me is that even though both Harman products use the same power response target, neither achieves it exactly, so we should not expect them to sound the same. And look at where they differ. One has a bump @ 1.8khz while the other has a dip, similar also @ 750hz. These are in the heart of the midrange, so I would imagine the differences are audible. And the Revel looks overall a bit smoother through this area so perhaps that is where the higher preference lay?
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Old 4th December 2018, 09:28 PM   #30
Zvu is offline Zvu  Serbia
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M2
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Salon 2
Salon 2 spinorama.jpg
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