JTR Noesis 212RT Measurements

[shellback]

The top graph is 2db per division while the bottom is 1db per division.

Thank you for pointing that out and welcome!

FYI - Jeff Permanian is JTR Speakers.

 

[andreasmaaan]

The top graph is 2db per division while the bottom is 1db per division.

That's true, but the vertical divisions in the top graph are wider.

I tried to line them up so that the scale was commensurate per pixel, rather than per division. As it turns out, it looks now as though the top graph spans 60dB while the bottom one spans 50dB. So it seems I was off by a factor of 5/6.

In any case, this only strengthens the original point.

 

[richard12511]

While this is an objective forum there has been many questioning the subjective sound quality:
https://www.audiocircle.com/index.php?topic=137722.msg1465233#msg1465233
http://www.enjoythemusic.com/RMAF_2016/Holt/Digital_Amplifier_Company_JTR_Speakers.htm

I don't think there's been that much subjective questioning. It's mainly just one person , and that person has never heard the speakers. He just doesn't like the shape of the horn. Yet, the "good horn" examples he's shown seem to measure worse.

 

[richard12511]

Random subjective report: I drank a 12oz bottle of 5 year aged Dogfish Head 120 Minute IPA(19% ABV) tonight while listening to classical and classic rock music on these speakers at 105-115db at the mlp(4m) for 2 hours. No distortion, no compression. Not many loudspeakers can do that.

 

[LTig]

Random subjective report: I drank a 12oz bottle of 5 year aged Dogfish Head 120 Minute IPA(19% ABV) tonight while listening to classical and classic rock music on these speakers at 105-115db at the mlp(4m) for 2 hours. No distortion, no compression. Not many loudspeakers can do that.

... and not many ears survive that.

 

[tuga]

While this is an objective forum there has been many questioning the subjective sound quality:
https://www.audiocircle.com/index.php?topic=137722.msg1465233#msg1465233
http://www.enjoythemusic.com/RMAF_2016/Holt/Digital_Amplifier_Company_JTR_Speakers.htm

I can only speak for myself and I have been questioning objective sound quality (audible distortion) not subjective sound quality (personal preference).

Could you explain the reasoning behind going from a more advanced profile (JRT 3TX) to the current straight-sided horn.

Also could you provide clarity in regard to the throat entry of the current design; does it have the curved transition profile necessary to provide geometric continuity?

 

[tuga]

Random subjective report: I drank a 12oz bottle of 5 year aged Dogfish Head 120 Minute IPA(19% ABV) tonight while listening to classical and classic rock music on these speakers at 105-115db at the mlp(4m) for 2 hours. No distortion, no compression. Not many loudspeakers can do that.

Sound good when you're drunk? Sure they can.

 

[TimVG]

Also could you provide clarity in regard to the throat entry of the current design; does it have the curved transition profile necessary to provide geometric continuity?

That's funny because some of the guys using and modding JBL 4722s seem to put a flat spacer between the driver and the horn to improve the measured response.

 

[tuga]

That's funny because some of the guys using and modding JBL 4722s seem to put a flat spacer between the driver and the horn to improve the measured response.

Does that spacer eliminate the curved transition profile (do they chop it off) or merely extend the distance of driver to horn entry?

 

[TimVG]

Does that spacer eliminate the curved transition profile (do they chop it off) or merely extend the distance of driver to horn entry?

 

[tuga]

It doesn't.

 

[jeff permanian]

I can only speak for myself and I have been questioning objective sound quality (audible distortion) not subjective sound quality (personal preference).

Could you explain the reasoning behind going from a more advanced profile (JRT 3TX) to the current straight-sided horn.

Also could you provide clarity in regard to the throat entry of the current design; does it have the curved transition profile necessary to provide geometric continuity?

The distortion is less than 0.30% below 6khz at 100db/1m. The 3TX is using an off the shelf horn. The horn on the 212RT provides 60 degree coverage over most of it range (some narrowing around 2khz). There is a contour transitioning the driver to the horn that is machined into the driver's mounting plate. The angle of incidence is equal to the angle of reflection so horns with slow expansion near the throat will have issues from reflections and suffer from narrowing as frequency raises. The horn measurement article that you posted has a good diagram showing this. Please see attachment and look at #4 trace. Rectangle horns have been mentioned however they suffer from issues at the lowend of the horns range.

 

[tuga]

The distortion is less than 0.30% below 6khz at 100db/1m. The 3TX is using an off the shelf horn. The horn on the 212RT provides 60 degree coverage over most of it range (some narrowing around 2khz). The angle of incidence is equal to the angle of reflection so horns with slow expansion near the throat will have issues from reflections and suffer from narrowing as frequency raises. The horn measurement article that you posted has a good diagram showing this. Please see attachment and look at #4 trace. Rectangle horns have been mentioned however they suffer from issues at the lowend of the horns range.

Thanks for the reply.
If I understood correctly the 212RT horn provides a more balanced/smoother coverage of its operating range than the off-the-shelf 3TX horn.

I don't think my question was clear, though.
I would like to know about the transition from cilindrical drill to the pyramidal stairght-sided throat, if it has the curved profile necessary to provide geometric continuity like an oblate spheroid or a quadratic-throat below, which as per the illustration guarantees that "the wavefront is always at right angles with the horn walls".

 

[jeff permanian]

We have a contour machined into where the compression driver mounts to the horn. I've found it advantageous not to have slow expansion near the horn's throat.

 

[richard12511]

... and not many ears survive that.

To be fair, I didn't start at those levels, but those are the levels I was reading towards the end. My ears were ringing for 20 minutes afterwards, so I know I did do some damage. Was my 30th birthday, though, and I had been aging that beer for 5 years. It sounded incredible.

 

[tuga]

We have a contour machined into where the compression driver mounts to the horn. I've found it advantageous not to have slow expansion near the horn's throat.

Thanks.

 

[tential]

This isn't the only science based forum. The diy audio section of avs forum is also science based and jtr speakers does have high regard there.

In my eyes, it's the best value speaker you can buy by a serious designer. These are of course heavy duty speakers.

It's either jtr speakers or build your own.

I would never recommend a serious home theater audiophile much else.

 

[tuga]

Interesting observations on horn profile, honking, etc.:

Factors Affecting Sonic Quality of Mid & HF Horns & Waveguides
http://www.audioheritage.org/vbulle...ic-Quality-of-Mid-amp-HF-Horns-amp-Waveguides

 

[dwill73]

To be fair, I didn't start at those levels, but those are the levels I was reading towards the end. My ears were ringing for 20 minutes afterwards, so I know I did do some damage. Was my 30th birthday, though, and I had been aging that beer for 5 years. It sounded incredible.

Curious what amp/receiver are you using?? My room is a acoustic nightmare to say the least with a 18yr. old Yamaha ZR-1 amp and my JTRs sound awesome. I've had mine to 118db. without distortion. Cherry Monos someday.

 

[tential]

Curious what amp/receiver are you using?? My room is a acoustic nightmare to say the least with a 18yr. old Yamaha ZR-1 amp and my JTRs sound awesome. I've had mine to 118db. without distortion. Cherry Monos someday.

These speakers have been tested by limiting only 1 watt to them with amazing results.

That's what happens when you have high efficiency speakers. You can get a lot of output with very little power.