Is it possible to cover the whole spectrum, high SPL, low distortion with a 2-way?

[camplo]

I'm in the process of buying tools, I thought 1/2" radius was good for edges but it might be 1", can anyone concur. #Backwoodsbastard

 

[Ro808]

I do have a current question about exit size...I’ve actually read people suggesting that exit size has no influence on performance of range or dispersion....I’m pretty sure that’s wrong but can someone confirm that aspect? I was taught, here that a large exit performs better down low and a smaller performs better up high. Performs being a somewhat ambiguous description. I’d think that exit size has an affect no different than diaphragm size of a dynamic driver. As far as range, exit size seems to affect it, but I don’t understand why if the diaphragm is the same size like with the 2450/2451 or 950/951. Oh the top of my head the 2450 has higher extension than the 2451, judging by the chart. How’s that make sense.

Exit size does affect dispersion and usable bandwidth, because it's related to the size and material of the diaphram as well as phase-plug design.

The 2450SL is a pancake driver, while the (early)2450 features a nose cap (exit extension). I don't believe the 2451 is completely different.

 

[camplo]

What I noticed is that the 2450 has better extension on the high and low side vs the 2451.....2450 is 2" the 2451 is 1.5". How that plays out on the dispersion I am not certain, I need to look over the specs but if they didn't use identical horns with different exit sizes then its not a fair comparison.

 

[Ro808]

You're correct, in the specsheet the 2451H is coupled to the JBL 2352, whereas the 2450J is coupled to a JBL 2380A.
The 2450 looks better on the horn, and also delivers slightly higher output on the PWT.

It's also clear the 2380 is a very competitive horn wrt directivity, considering its modest size.

 

[GM]

I'm in the process of buying tools, I thought 1/2" radius was good for edges but it might be 1", can anyone concur. #Backwoodsbastard

In general, folks use a radius = material thickness, though going up to the next size to get a 'perfect' joint seam is a good plan, but if wanting to acoustically help, then must be much larger like on Dr. Geddes' Summas.

GM

 

[GM]

Generally we read the the smaller exit drivers go higher, flatter.

Looking at some on axis plots of various drivers, I don't always see that it follows.

Need to keep in mind that at least with Altec, early JBL that they have an internal, very narrow dispersion conical horn terminating at 1"/whatever, but start with a 5/8"/whatever throat, which sets its HF gain BW/cutoff.

GM

 

[Pano]

Ah, thanks. Good info.

 

[Robh3606]

Generally we read the the smaller exit drivers go higher, flatter. Some super tweeter compression drivers are 0.75" Altec did many 1.4" considered a compromise between 1" and 2".

It's not as simple as that. The phase plug, diaphragm material and diaphragm type all contribute. I have 1.5" drivers that are much more extended than all of my 1" drivers. Take a Be diaphragm and load it into my 1.5" driver and it rolls off and is not as extended.

Rob

 

[Ro808]

This is similar to my own experiences, Rob.
Subjectively perceived and measured output of a B&C DE 250 in the top octave isn't significantly better compared to some 3" diaphragm drivers of the same brand, or from competitors (FaitalPRO).

A ring radiator (BMS) is better >12kHz, but lags behind in the midrange compared to best 1" drivers.

 

[Ro808]

I'm in the process of buying tools, I thought 1/2" radius was good for edges but it might be 1", can anyone concur. #Backwoodsbastard

Roundovers... these are primarily useful for baffled waveguides and smaller cone drivers (<12").
For larger cones and low XO points you would need either a bullet shaped cabinet or a curved baffle in order to measure the difference.

At least, this is what I've learned from experienced builders and professionals.


Harman's Revel was one of the early adopters of rounded baffle edges for the Ultima and its successor: the Ultima Salon2.

However, if you take a look at the 4367 and M2, you'll notice only a small chamfer.

 

[Forane12]

I am tempted to ask again what was so wrong with the M2's WG? It was supposed to be the better one compared to the one in the 4367. And I quite liked the 4367 from the mids up, at least there was no beaming...

 

[camplo]

http://www.dwdrums.com/images/moonmic/olson_direct-radiator-loudspeaker-enclosures.pdf

Link on Harry Olsons studies on baffles. Anyone have some sources with better info? not that this one is bad, just a little dated.

 

[GM]

Maybe you can find what you want under this Google search: reflections off bounded surfaces - Google Search

GM

 

[DonVK]

http://www.dwdrums.com/images/moonmic/olson_direct-radiator-loudspeaker-enclosures.pdf

Link on Harry Olsons studies on baffles. Anyone have some sources with better info? not that this one is bad, just a little dated.

Vance Dickason's Loudspeaker Design CookBook (2006), Chapter 5 (cabinet shape) does a repeat on shape experiments that parallel the Olson experiments. Except Vance used larger drivers, both cone and dome, and he used smaller baffles than Olson.

 

[Ro808]

LDCB Chapter 5 & 6.

 

[Ro808]

This guy has successfully dealt with baffle edge (step) effects.

However, you have to take the size of his roundovers into account, relative to the baffle width and the size of his drivers.

 

[norman bates]

If i remember, the jbl m2 horn was about spreading the diffractions.

The Making of a Monitor: An Inside Look at How JBL Developed the M2 and Re-ignited Its Studio Line - Mixonline
"Forming an infinite number of reflections, and the net effect is that it smears the reflections coming back down the horn and negates them."


Why not try to not have them in the first place ?

 

[Ro808]

I am tempted to ask again what was so wrong with the M2's WG? It was supposed to be the better one compared to the one in the 4367. And I quite liked the 4367 from the mids up, at least there was no beaming...

Not much wrong with either of those, except for the rather limited depth of the M2 WG.
If anyone could take a series of Hi-Res images, 180° from the front of the 4367's horn, these could be automatically reconstructed into a 3D model by using photogrammetry software.
3DF Zephyr is probably no. 1 and Autodesk ReCap second for this purpose.
The free edition of 3DF Zephyr (50 photos max.) would suffice.

 

[Ro808]

P. Bateman's experiments with waveguides and synergies are fascinating.
He primarily focuses on tiny waveguides and miniature drivers that fit in, on or under the dashboard of his car.

In his "M2 for the poors" thread, this post is particularly interesting.

 

[Ro808]

Why do JBL's Image Control Waveguides excel?
Because these are diffraction horns.

An externally hosted image should be here but it was not working when we last tested it.