JBL PT 100x100 waveguides, any experience? MPro?

Hello,

There is another thread that goooooes on about this and other stuff.

I will reply here.

What driver will you use with this horn/wave guide?

What is the low crossover frequency for a possible 2-way? I see that JBL used 1.6K for the original version of this wave guide>

I am thinking of 3-way with JBL 2123's Directivity may be close at about 2K crossover.


I have a pair of JBL 2451's to test drive with these wave guides that I ordered today.

Thanks DT

Thoughts Comments?
 
polars look nice till 8khz anyway.
https://www.jblpro.com/ProductAttachments/JBL_AM7212_00-082016.pdf

I see it is a 1.5" throat (jbl 2432), but jbl uses it occasionally with a 1" with adapter such as the jbl 2408. But good question, I can't see going under 1.5khz, that would then lean towards 8's for dispersion.

I have a jbl 2407, but I not against other drivers.

Just where I am at, currently seeking reflection free horns that ideally don't beam like an exponential horn as the frequency increases.

Where is the other thread ?

I saw rob had the earlier pt h1010hf used in a 3 way.

Me, I'm thinking 2 x 8" crossed at 2khz.
Something of a higher output speaker but clean monitor for mid volume movies.


Norman
 
Hello I am looking to cobble together something that looks like a finished speaker. I do not expect this thing to ever be complete. Typically mid 80dB’s In terms of volume but then 100dB’s plus to shake things on occasion. I am also thinking of a sectioned front panel that can be removed and replaced in pieces with different midrange drivers and different tweeters including horn/waveguide variations as the mood changes.

Reflection free waveguides with short rapid flares sounds like a good idea to reduce diffraction and other distortions. I am also thinking of compression drivers with larger diaphragms that have larger air volumes behind the diaphragm to reduce the typical horn adiabatic nonlinear air compression distortion associated with horns. A faster flare rate in front the phase plug, a larger diaphragm and a larger air space behind the diaphragm adds up to a compression driver and horn with less compression and less distortion. Maybe? Stuff that I want to test.

Nice looking polars are a goal. Smooth, level and flat Directivity Index plots are nice. I wonder if level, dead flat constant directivity is necessary for optimal sounding speakers? I am thinking a smooth gradually sloping Directivity Index plot might be preferred. At least avoid discontinuous doglegged Directivity Index plots. The directivity should be set to the Goldilocks standards to allow just the right amount of space in the listening room.

Just some reflections of mine.

Thanks DT

Comments Thoughts?

The other thread.

1.4" or 2" throat large constant directivity horns you can actually buy!
 
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A flat and level directivity index will take a very determined effort to achieve. Smooth is definitely wanted.

In my opinion, getting it level is a sign of getting a lot of things right, for example focusing reflections behind you. At some lower point early reflections disappear, for example work out the first reflection frequencies. At the lowest frequencies directivity becomes a hazy issue, for example filling the room via its modes is the goal. Blending down to these points though can still require an acoustically large device.
 
I'm talking about reflections in horn path.

This would be reflection free.
 

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I see your point as you explain in your first post. This would be a good waveguide by those guidelines. I think calling it reflection free is splitting hairs.

There are more fundamental parameters such as how well it can hold directivity down to some frequency. For this the choice can't be based on it simply not doing anything else wrong.
 
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Yes it is. I guess I've made the assumption that it is done in a certain way. What kind of DI are you thinking about.. narrow, as wide as possible while excluding early reflections, frequency restrictions?
short rapid flares sounds like a good idea to reduce diffraction and other distortions.
I assume it doesn't make sense to let the directivity widen then narrow again, so a small waveguide is going to force wide directivity from a highish frequency down.

With regard to diffraction, a larger waveguide can reduce the issue as well by holding the wavefront until it can substantially support itself.
 
Yes it is. I guess I've made the assumption that it is done in a certain way. ...

I assume it doesn't make sense to let the directivity widen then narrow again, so a small waveguide is going to force wide directivity from a highish frequency down.

...

AlanB,

You are making a lot of assumptions; I do not know what they are. Please more words and clarity.

This thread started with the JBL PT H1010HF waveguide, JBL uses this wave guide with a crossover frequency of 1.6 Khz. That means any genital uphill slope in the DI vs frequency plot below 1.6K belongs to the cone woofer. From 1.6K up to 8K the DI plots provided by JBL look to be close to level and flat. Above 8K, with the data provided by JBL, it is hard to tell what is happening, other than an increasing slope.

JBL data sheet https://www.jblpro.com/ProductAttachments/JBL_AM5212_00-082016.pdf

Thanks DT
 
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Hello,

I am going to muse a bit more about using this JBL PT H1010HF waveguide.

The good folks over at JBL have done a lot listening preference tests. Not just can you hear a difference but do you prefer A over B or have no preference. I do not believe that there is any coincidence that the very similar waveguide in the JBL flagship M2 monitor is also 100 degree by 100 degree “constant dispersion”. I have the belief that the 100 x 100 dispersion waveguide is preferred because of the sense of space or emersion in the listening room(s) where the preference testing is performed.

The next logical step for successful marketing is to link this factory preference testing to the listening rooms across the market place. Good job Harmon/JBL.

Thanks DT
 
Hello,

A pair of H1010HF-1 waveguides will be delivered by UPS tomorrow. The JBL 2451 drivers are due on Friday. There will be a couple of days over the weekend to test drive these “Constant Dispersion” waveguides.

Looking around at “Constant Dispersion” waveguide performance it looks like none of them do a consistent job across the Band Width up to 20Khz. Even the M2 has a steep dogleg up in the DI vs frequency plot starting at about 8Khz.

Does anyone recall seeing or using a DIY speaker turntable for off axis speaker frequency response testing?

Thanks DT
 
I see there are the older pt waveguide in a jbl speaker.

The am4212/00.
I can speak for the compression driver, the 2407 doesn't have the big peak at 10khz that the 2408 does (jbl usually notches it out).
And no ferrofluid to worry about if 10 years old.

JBL AM4212/00 2-WAY LOUDSPEAKER (ONE) | eBay

If you offer 250, they will probably counter offer with 300 each (plus 85 shipping each).

The pic is the 4212/00, notice the bubble near throat.

I have no associations with seller and they are not mine.
I just ordered a pair of 6212/00 from them.


Norman
 

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Hello Norman,

It is all your fault.

I have been using the JBL H1010 HF-1’s with JBL 2432 drivers for several weeks now. I like the way they sound; open dynamic and all that. I like the 100 X 100 beamwidth much better than the 90 X 50 kind of stuff. With the 100 X 100 there is much more freedom to get up out of your seat and move around, the sweat spot, if you will, is much bigger. No head in the vise kind of affect like you get with the narrow beamwidth waveguides.

I am using 10 inch JBL2123H cones for mid-range drivers and cross-over at 1600Hz to the JBL H1010 HF-1’s with JBL 2432’s.

Thanks DT
 
I like the 100 X 100 beamwidth much better than the 90 X 50 kind of stuff. With the 100 X 100 there is much more freedom to get up out of your seat and move around, the sweat spot, if you will, is much bigger. No head in the vise kind of affect like you get with the narrow beamwidth waveguides.

I am using 10 inch JBL2123H cones for mid-range drivers and cross-over at 1600Hz to the JBL H1010 HF-1’s with JBL 2432’s.

Hello DT

Yeah me too on the 100x100 started with 2344 and 2425's in my active set-up. Really liked the open sound and freedom to move around. They also imaged great, nice and stable no head in a vice like you were saying. Changed over to PTH1010h and 2435 years ago and have not changed them. I also use a 2123 crossed about 1,5K and really like that combo.

Yeah something about those 100X100 just sound really good in my room

Rob:)
 
I've been looking at the crossover on my jbl am6212/00.

The 2431 has a plane wave response drooping after a couple of khz till peak maybe 13khz.
Seeing how the horn is 100x100, i assume no free boost as freq goes up.
Yet jbl's crossover has a notch at 10khz.

Any thoughts ?

Also, i think the jbl 2206 climbs till its 1200hz cross over point.

I'm having a hard time eq'ing my speaker by ear.
 

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