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

No, it's not possible.
Its already been answered, and the answer is yes, its just not whats been practically done. I am trying to finish up my project, and it is looking 2-way at this point, The Axi2050 mated to 4 large woofers on each channel. Any two-way can do it if designed with this condition; Excursion kept under ~2mm at peak spl at lowest intended reproduced frequency. That is overkill, less efficiency would yield desirable results, Keeping excursion under 2mm at peak spl is better than most peoples systems period. The challenges are dispersion, LF extension of the tweeter, and woofer efficiency. The lower your tweeter can play, the less you have to worry about woofer excursion. The more efficient the woofer section, the less you have to worry about tweeter lf extension. TMM and MTM are the easiest ways to have a large 2 way for this application. A large 2 way with only 1 large woofer can it as well if we allow the definition of "whole spectrum" to "enough of the spectrum". 30hz cutoff is suitable for music playback and a large 2way can play this bandwidth at high spl/low distortion. Sub woofer systems are commonly seen as a separate application because multiple subs is and has been one of the status quos. Once multi subs are introduced LF goes up.
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The lesser the amount of drivers used in the LF section puts more pressure on the included woofers to perform, meaning the best drivers available are required. High Xmax, High BL, low Q.
 
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Define "whole spectrum"?

For me it´s 20-20.000 hz, even if its -3,4 hz at 20 hz.
Which woofer can handle that it up to xover?
I'd like to know. I think the lowest among my mixed army of ten different 15-inchers, Fostex 15W300, is officially Fo25hz-3khz, though I haven't considered going lower. JBL 2226H Fo40hz should be able to cover 30hz-ish to 1.5khz (3-tweeter reflector point-source).

 
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'd like to know. I think the lowest among my mixed army of ten different 15-inchers, Fostex 15W300, is officially Fo25hz-3khz, though I haven't considered going lower. JBL 2226H Fo40hz should be able to cover 30hz-ish to 1.5khz
Yes, the "best" 15 inch i know of handling up too 800 hz is old JBL.
2215h, E-145 and maby some other.

But no near 20 hz there, and a driver thats "handle" around 20 hz will be "feed up" at 3-400 hz max.
 
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For me it´s 20-20.000 hz, even if its -3,4 hz at 20 hz.
Which woofer can handle that it up to xover?
literally any woofer if kept within a few mm of excursion lol.... OK I can't say literally cause I have no idea what "even if its -3,4 hz at 20 hz." means? Once a drivers excursion has been eliminated there is little left to signify.
Define "whole spectrum"?
I think the listener has to do that. I agree with you that I want to cover 20hz and above. For music, some might argue that 30hz and above is fine.
 
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The challenges are dispersion, LF extension of the tweeter, and woofer efficiency. The lower your tweeter can play, the less you have to worry about woofer excursion. The more efficient the woofer section, the less you have to worry about tweeter lf extension.
I'm afraid I don't get that.

Isn't large-C2C vertical comb-filtering an issue even in a very large room?
 
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CtC is an issue in any room isn't it? I'm confused about your question because the majority of design out there do not reach optimal results on the vertical polar.... it is the norm actually. Show me a waveguide based design without a vertical null... except for maybe mine when I run a low Xover or A synergy/coaxial type design.
 
CtC is an issue in any room isn't it? I'm confused about your question because the majority of design out there do not reach optimal results on the vertical polar.... it is the norm actually. Show me a waveguide based design without a vertical null... except for maybe mine when I run a low Xover or A synergy/coaxial type design.
(Pictured) 45cm-CtC 2-way crossed high, even worse than usual WG+15 (which I don't like unless very far away).
 
I think it can with the right design, and probably a little damping material. Depending on the crossover one may not need to be so extreme, as trying to keep excursion limited to 2mm. The very last part of the last octave, is extreme. A tuning near 25hz helps alot. Truth be told I dunno any other way to get closer than basically what I am doing with the sets of PPSL woofers, totaling to 8,160cm². The 2mm or less goal is pretty ambitious like I said. Another person might argue that reasonably we should be able to trust a woofer to something closer to Xmax. With a 14mm Xmax I'd like to think that 7mm of that excursion is worthy of the best production if the woofer is one of high stature. Non the less, if we relax from 2mm to half Xmax, which is still being conservative, headroom might be considered much higher for these scenarios we are debating
 

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Think it´s maximum is around 350 to 450 hz anyway.
If a woofer is worthy of crossing, say 500hz... if we can keep its excursion down, then it should be able to play anything below, while crossed at 500hz, once again, with excursion being the limitation. The logical thinker would say, well isn't that the problem? Keeping excursion down that is? And I would say yes. Its the main almost only problem in a lot of cases. So from there you might wonder ok, well what I can I do lower excursion while meeting the expectations I might have. I see people crossing waveguides ~800hz most of time. Horns crossed closer to ~600hz with some crossing 500hz, and even less going lower. Just a random assessment of a lot of what I've seen. The SE-MF2.1 crosses at 400hz so they say. I think most people aren't using a driver that will play well so low, (4" diaphragm/2" exit) or is it a Horn not big enough... but SE-MF2.1 horn...a JBL(2380A?), thats hardly a 200hz F3 horn which is what some argue should be used for that cutoff. So with large/powerful compression drivers, we can be a little creative. I am all for low crossovers anyway so its already up my alley. I don't think my 15"s sound better than my compression driver on the large horn either. I think the biggest part about it is directivity, not drivers, but still it seems past about 300hz there starts to be issues.
 
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Think it´s maximum is around 350 to 450 hz anyway.
As you know i have 6 woofers with FS 21,8 and +- 12,5 mm linear xmax and 2800 cm2.... but only up to 340 hz
Filter/EQ'ed down ~10dB at 400hz, bandwidth broadens above 1khz. Loud enough?

My tweeter assemblies (soft-dome or ceramic) can approach 1khz from above.

Without doing anything fancy the Fostex 15W300 paired with bullet T96A (which I'm eyeing but holding off on) could meet at 3khz each 100dB sensitivity.
 
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