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Is it possible to cover the whole spectrum, high spl, low distortion with a 2-way?
Is it possible to cover the whole spectrum, high spl, low distortion with a 2-way?
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Old 14th February 2021, 02:00 PM   #6391
DonVK is offline DonVK  Canada
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Quote:
Originally Posted by camplo View Post
Just to make sure I'm smoking what is being put down....Are we trying to say here that I can cross that Axi at 400hz with an OSWG without it loading to 400hz? I thought we had this conversation before and the verdict was a no? Am I mistaken?
Let's compare 2 horns that I have both physical items and simulation models. The SH402 (like a 2370a, diffraction horn) and a PHRN1014 (like the QSC, OS like) both are approx 90x50 coverage and relatively constant directivity. The complete model sim data is at Modular active 3 way - work in progress They are advertised to be useful to 400Hz and 500Hz respectively.

The actual SH402 requires 6dB EQ to make it flat at 800Hz, and the PHRN1014 requires 12dB and you can see that in the RadImp (loading) graph differences. So the answer depends on how much EQ you want to apply as you force output at lower frequencies. Both horn mouths are large enough to control the wavefront to approx 600Hz and used the same compression driver.
Attached Images
File Type: jpg SH402.jpg (37.8 KB, 158 views)
File Type: jpg SH402-RadImp.jpg (35.5 KB, 160 views)
File Type: jpg B52-PHRN1014.jpg (52.3 KB, 155 views)
File Type: jpg B52-PHRN1014-RadImp.jpg (34.4 KB, 153 views)

Last edited by DonVK; 14th February 2021 at 02:15 PM. Reason: coverage
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Old 14th February 2021, 02:44 PM   #6392
camplo is offline camplo
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ok I reaaally need to pay attention to my hornresp modelling cause I let the calculator change my exit size...ok

The smallest thing I can sim is a 1000hz horn...

but I can see that as long as my dimensions of the diaphragm are close, with this 1000hz tuning, theres no support at 200hzand400hz right?

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

if thats too big let me know....on a 65" screen everything is small to me)
um the bottom left is after a 200hz 6db butterworth and the right is a 400hz.
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File Type: jpg fkaye.jpg (299.6 KB, 162 views)

Last edited by camplo; 14th February 2021 at 03:06 PM.
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Old 14th February 2021, 03:08 PM   #6393
camplo is offline camplo
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I need to study IMD in tweeters...
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Old 14th February 2021, 03:12 PM   #6394
camplo is offline camplo
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Quote:
Originally Posted by DonVK View Post
Let's compare 2 horns that I have both physical items and simulation models. The SH402 (like a 2370a, diffraction horn) and a PHRN1014 (like the QSC, OS like) both are approx 90x50 coverage and relatively constant directivity. The complete model sim data is at Modular active 3 way - work in progress They are advertised to be useful to 400Hz and 500Hz respectively.

The actual SH402 requires 6dB EQ to make it flat at 800Hz, and the PHRN1014 requires 12dB and you can see that in the RadImp (loading) graph differences. So the answer depends on how much EQ you want to apply as you force output at lower frequencies. Both horn mouths are large enough to control the wavefront to approx 600Hz and used the same compression driver.
Thank you for showing this Don. My first thought is that these two horns have resonates within the passband...with a waveguide the tuning is generally out of the passband (or at the tippy top of it, looking at Fluids waveguide) so the EQ is going to look different but your though set still applies, after all is said and done ...done how much eq...they are able to produce waveguides where the on axis response is nuetral...from the horn aspect, it starts at the Axi's free air measurement from here?

With the current 350hz horn only one low shelf is needed to tweak the slope...I'm not sure how much attenuation if any is needed, I figured out how loud white noise was before finishing that session and lost track on another rant...

Last edited by camplo; 14th February 2021 at 03:16 PM.
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Old 14th February 2021, 03:43 PM   #6395
Ro808 is offline Ro808  Netherlands
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Quote:
Originally Posted by DonVK View Post
Let's compare 2 horns that I have both physical items and simulation models...
...Both horn mouths are large enough to control the wavefront to approx 600Hz and used the same compression driver.
Thanks Don, good to see such comparisons.


Up-to-date overview of horn profiles with their respective impedances:
Attached Images
File Type: png Horn Types.png (338.8 KB, 47 views)

Last edited by Ro808; 14th February 2021 at 03:47 PM.
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Old 14th February 2021, 03:56 PM   #6396
camplo is offline camplo
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Kippel? Is this what I need to investigate? How do I measure IMD and doppler and AMD...or better yet...why isn't this stuff already figured out? after a certain amount of excursion....no matter the size of the driver...certain distortions are eminent (probably amplitude modulation)....you guys must be keeping this information to yourselves or something?... I'd guess this be common knowledge amongst DIY designers. Who came up with the 2mm limitation for midrange drivers...whats the limitation for tweeters? I must be asking a crazy question and obviously something like 1mm and under is a good place to start huh lmao! I don't know! Guess this is my knew obsession for the moment. Maybe this is a unique question, whens the last time someone had a tweeter than could play to 400hz...pretty much anyone with a large format compression driver it sounds like but...I don't know what the heck is going on.

Last edited by camplo; 14th February 2021 at 04:01 PM.
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Old 14th February 2021, 04:00 PM   #6397
Ro808 is offline Ro808  Netherlands
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Quote:
Originally Posted by DonVK View Post
Let's compare 2 horns that I have both physical items and simulation models. The SH402 (like a 2370a, diffraction horn) and a PHRN1014 (like the QSC, OS like). They are advertised to be useful to 400Hz and 500Hz respectively.
The advertising obviously has nothing to do with practical reality

The values should be doubled, the 2370a can be used from about 800 Hz and the PHRN1014 from 1000 Hz.
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Old 14th February 2021, 04:11 PM   #6398
Ro808 is offline Ro808  Netherlands
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Long ago it was determined that 2 mm is a critical threshold for Doppler distortion in woofers, I believe by a number of scientists at Philips.
Of course IMD is also excursion dependent (among other things).

For subwoofers, IMD and Doppler distortion are less relevant.

Excursion of compression driver diaphragms is often less than 1 mm, so IMD and Doppler distortion are rarely factors of significance.

Last edited by Ro808; 14th February 2021 at 04:16 PM.
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Old 14th February 2021, 04:14 PM   #6399
gedlee is offline gedlee  United States
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Originally Posted by fluid View Post
One thing that is not always apparent in the discussions of narrow vs wide pattern designs is that if done properly the wide pattern can be more similar off axis and therefore any reflections that return to the listening position are more spectrally similar to the on axis sound. This is something Floyd Toole talks about out of the blind perception tests but the theory does not seem to have been proven. This is something I would like to try out for myself to see if it is real.
It has not been proven and Floyd and I agree that there is no definitive answer - it depends on listening source preferences.

As to tests, let me describe an unpublished one that we did.

Consider two sources, one wide and one narrow, both CD. With the wide one no matter how one points the system the reflection pattern remains basically the same. But, the narrow one can be pointed such that the farther wall gets more sound while the closer one gets less. Is this reflection pattern difference effective. We tried to test that.

In the test we (lidia, another DIY and myself) tried (I say tried because I don't think we were totally successful, as you will see,) to simulate this situation. We had >20 blind subjects where they were asked to point to the location of a virtual simulated source, with first reflections, and without. The accuracy of their guesses would show a degradation of imaging. Reflections clearly degraded the image stability when compared to no reflections. In the end the results were not "statistically significant" and so my wife did not want to publish a paper.

That said, the results did indicate that pointing a narrow directivity speaker at the far wall does improve image localization - it just wasn't "statistically significant" in this small and somewhat simple test.

Now, if localization is not what you are looking for since, perhaps the recording is done in-situ with lots of confounding reflections on the source added to those in the room, then adding spaciousness to cover those aberrations is going to be perceptually advantageous.

On the other hand consider a fairly dry studio recording where strong imaging is a goal. In this case the narrow directivity when properly setup can enhance the imaging - but of course spaciousness will degrade. But spaciousness is not a criteria in the most studio work.

This is precisely where Floyd and I agree to disagree since our musical tastes are on the two extremes and we understand what each is looking for and that they are different.

One will never find nirvana until they come to a decision about what is important to them - what they are willing to give up (spaciousness) or emphasize (imaging). Good speakers do both better, of course, but at the extremes of design - like what should the DI be - there isn't one answer. But both Floyd and I do agree that in either case smooth and nearly flat DI is essential. Exponential horns don't do that, they beam.
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Old 14th February 2021, 04:20 PM   #6400
gedlee is offline gedlee  United States
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Quote:
Originally Posted by camplo View Post
Kippel? Is this what I need to investigate? How do I measure IMD and doppler and AMD...or better yet...why isn't this stuff already figured out? after a certain amount of excursion....no matter the size of the driver...certain distortions are eminent (probably amplitude modulation)....you guys must be keeping this information to yourselves or something?... I'd guess this be common knowledge amongst DIY designers. Who came up with the 2mm limitation for midrange drivers...whats the limitation for tweeters? I must be asking a crazy question and obviously something like 1mm and under is a good place to start huh lmao! I don't know! Guess this is my knew obsession for the moment. Maybe this is a unique question, whens the last time someone had a tweeter than could play to 400hz...pretty much anyone with a large format compression driver it sounds like but...I don't know what the heck is going on.
It has, it just gets ignored. Doppler distortion in driver is not really an issue. It can be, of course, in a poor design, but it needn't be. And almost any nonlinear distortion in the driver itself needn't be an issue, so design it out. That's why you don't hear much about it because most professionals have moved on to topics of significance. Nonlinear distortion in drivers is not an issue. Again, Floyd Toole and I are complete agreement on this point - it's been laid to rest.
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