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Multi-Way Conventional loudspeakers with crossovers

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Old 22nd October 2020, 08:40 PM   #531
Oneminde is offline Oneminde  Sweden
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The point I wana make for the APL vs BR is that if you look at the image I have included you can see what each individual part does.

The BR is Bessel tuned.

The APL graph is imported onto the BR simulation - this graph is the yellow one.
The total SPL into half sphere of the BR is indicated with the dark gray graph.
The port is indicated with red - remember that a port is always 180 degree out of phase with the driver.
The cone motion is indicated in blue.

We can see that there is a complete phase shift occurring at the port tuning frequency which in this case is at 30Hz. Also notice the cone movement between 25hz to about 55Hz... In a video I found on youtube a few years ago, this dip in cone output is recorded. Both a sealed and ported enclosure is demonstrated.

Ported vs. Sealed - Detailed Comparison - YouTube

While there are some benefits seen between 20-200Hz in this case, the cone and port behavior is less than ideal in my opinion.
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Old 22nd October 2020, 08:52 PM   #532
diyiggy is offline diyiggy
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...That is my underdtanding as well. So we can agree than Qtc at 0.5 is the way to go. Harmonics are in the reccording if acurate and if one has a chance to reproduce it in the right order and amplitude then better your driver to have no over or under shouting due to the load that will overlap the harmonics that follows and that are also in the next time windows? Ringing you are talking are in the reccording and not a new event created by the non good damping of the driver...theorically speaking I mean.
Can we agree here on the theory?

Last edited by diyiggy; 22nd October 2020 at 08:55 PM.
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Old 22nd October 2020, 09:11 PM   #533
twinter is offline twinter  United States
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Originally Posted by diyiggy View Post
...That is my underdtanding as well. So we can agree than Qtc at 0.5 is the way to go. Harmonics are in the reccording if acurate and if one has a chance to reproduce it in the right order and amplitude then better your driver to have no over or under shouting due to the load that will overlap the harmonics that follows and that are also in the next time windows? Ringing you are talking are in the reccording and not a new event created by the non good damping of the driver...theorically speaking I mean.
Can we agree here on the theory?

Optimum perceived Qtc of a woofer system is impacted greatly by the system resonance frequency and room gain.


General Subjective Guidelines For Woofer Systems in Sealed Enclosures:
f3=100 Hz......Qtc = 0.85 to 1.1
f3= 60 Hz.......Qtc = 0.6 to 0.85
f3 = 40 hz......Qtc = 0.5 to 0.75

Relating back to Speakerbuilder or Audio-X-Press Magazine articles, optimum subjective midrange clarity was stated to be with the Qtc below 0.71, in the 0.5 to 0.65 range.

An interesting and informative article by John Kreskovs (John K) on seal enclosure woofer system Qtc and non-steady state sine wave responses. There are two pages, so use the blue & white arrow button (Top left).
About Sealed Box-Q's
Box-Q

I have been plagiarizing myself on my previous posts on this site by the above prior comments.

We are veering, and staying off track here, from the original thread "SB Acoustics Textreme".

Last edited by twinter; 22nd October 2020 at 09:30 PM.
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Old 23rd October 2020, 02:27 AM   #534
diyiggy is offline diyiggy
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Interresting link


One doesn't want to use such good drivers without the best around... impulse response and phase... well lack of clarity and speed of the bass is not just about the damping of the cone by the material... we are on the topic here... Inverted polarity with passive filter in the tweeter can imho have great negative impact on the bass because the impulse response, just look at a good Dunlavy for instance... Without wanting to go with first slope XO, there are some other solutions to optimize the good textreme choice as already pointed out : minimum phase design la Duelund filter or why not la JMLC optimised filters to make the impulse response as good as possible in the crossovers area... Or digitally with Rephase for instance.. Sealed and low Qtc is not waf friendly because of the big cabinet in the bass (and also the cunterpart of a higher -f3 ... but a sympathetic -f10... well I assume electronic FIR EQ is a must to deal with the room in the low end...


I'm sure the 5" Textreme is going to give sweat to a lot of drivers ! Looking forward to read the reviews !
Anyway thanks guys for the link and sim aboce
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Old 23rd October 2020, 09:49 AM   #535
TNT is offline TNT  Sweden
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Originally Posted by oldspkrguy View Post
I don't understand the violation, I didn't even quote anything at all, just from memory; I didn't open the book or anything like that. If I violated a copyright; it was purely by accident; I haven't read that chapter in YEARS.
You linked to a file containing a book which is not in the public domain / for free - i.e you helped to acquire the book without paying.

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Old 23rd October 2020, 12:45 PM   #536
twinter is offline twinter  United States
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Relating back to Speakerbuilder or Audio-X-Press Magazine articles, optimum subjective midrange clarity was stated to be with the Qtc below 0.71, in the 0.5 to 0.65 range.
The above should have read:

Relating back to Speakerbuilder or Audio-X-Press Magazine articles, for a midrange driver, optimum subjective clarity was stated to be with the Qtc below 0.71, in the 0.5 to 0.65 range.
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Old 30th October 2020, 12:45 AM   #537
hifijim is offline hifijim  United States
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My new drivers arrived today. A pair of TW29TXN-B and a pair of MW16TX-4.

I am fabricating a baffle to do some measurements. I am using a 24"x24" sheet of XPS foam board (thanks to XRK971 for recommending this). I hope to have some results in a couple of days... Frequency response on and off axis, harmonic distortion, etc..
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File Type: jpg s20201029_183951_HDR.jpg (545.5 KB, 523 views)
File Type: jpg s20201029_185718.jpg (557.9 KB, 823 views)
File Type: jpg s20201029_183705.jpg (892.7 KB, 450 views)
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Old 30th October 2020, 02:39 AM   #538
454Casull is offline 454Casull  Canada
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Originally Posted by hifijim View Post
My new drivers arrived today. A pair of TW29TXN-B and a pair of MW16TX-4.

I am fabricating a baffle to do some measurements. I am using a 24"x24" sheet of XPS foam board (thanks to XRK971 for recommending this). I hope to have some results in a couple of days... Frequency response on and off axis, harmonic distortion, etc..
I have to ask... how well does the pattern of the weave line up with the mounting holes?
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Old 30th October 2020, 02:39 AM   #539
rhale64 is offline rhale64  United States
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I can't wait to see the results. I am really interested in a system using these drivers. But I want a three way with the bigger mw along with one of the smaller mw's
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Old 30th October 2020, 05:22 AM   #540
hifijim is offline hifijim  United States
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Quote:
I have to ask... how well does the pattern of the weave line up with the mounting holes?
Honestly I did not check that. I know it is important to some people, but it is not something I am concerned about.

Looking at the photos, it looks to me like it is aligned decently...
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