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Old 3rd December 2012, 12:22 AM   #411
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I doubt you are tourist in any of this. Appreciate the response. Will play more with MJK.
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Old 3rd December 2012, 12:38 AM   #412
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I was just playing with the program.

If there is a way to use square port, I would love to know.
Understood and I was just giving you something else to consider for maximizing SQ!

Square, rectangular ports of the same area are ~ identical to round until the aspect ratio exceeds ~1:1.2732, then friction losses begin increasing the length required for a given Fb with increasing ratio until around 1:9 when it heads towards aperiodic.

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Old 3rd December 2012, 12:56 AM   #413
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all I can say is that , properly made long (folded) pyramidal MLTL (or derivation of it ) is much less boxy sounding than BR counterparts

difference is , if you put it that way - that BR is always haroomph-ing through pipe (opening ) while TL (derivatives ) are much less using those openings for relaxation

dunno - I'm telling you - trust to GM's words (even if I sometimes can't grasp sole simple sentence he's writing )

I'm just a tourist in those loudspeaker things
They really need to brush that horses hair.
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Old 3rd December 2012, 12:58 AM   #414
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Quote:
Originally Posted by GM View Post
Understood and I was just giving you something else to consider for maximizing SQ!

Square, rectangular ports of the same area are ~ identical to round until the aspect ratio exceeds ~1:1.2732, then friction losses begin increasing the length required for a given Fb with increasing ratio until around 1:9 when it heads towards aperiodic.

GM
GM, What do you think of the enclosure 1.3 I modeled and how would your ideal enclosure differ. I have figured the port based simply on the area of the port diameter strecthed out into a rectangle, with the length being the thickness of the proposed baffle, about 1.25".

In detemining the rectangular port, is ther any difference if it stretches from one side to the other, like in Scottmoose' Pensil designs, or is it better to have it centered with a limit on width. Based on 1.4 design, a vent stretching across the 19" interior face would have to be 1.25" tall to equal the area of figured 2.75" port. I noticed in your big MLTL for the 416, the rectangular port was quite small.
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Old 3rd December 2012, 01:30 AM   #415
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Originally Posted by buzzforb View Post
Couple of questions.

How important is consistency of wavelets(?) of the first two impedance graphs?

How do you determine port tuning? I have been using WinIsd. I dont know how to model aperiodic tuning.

Here is try using better box ratio. Cant figure out why acoustic impedances are so ugly and why there is nasty port phase issue
I think it's important or I wouldn't have suggested you compare the different driver locations I posted plus Iíve posted that vents typically do well at 3rds, 5ths.

That said, stuffing density is the great equalizer, so for the vast majority of folks itís not AFAIK and when thereís a large horn perched on top I typically ignore it somewhat since c-t-c spacing normally has a more audible impact on SQ.

At whatever frequency the cone excursion has the deepest null.

True aperiodic loading means to flatten the driverís impedance peak as much as practical, so only a properly designed TL or BLH can do this AFAIK.

All others are semi-aperiodic at best and can be simmed in WinISD Pro by changing the rear chamberís and ventís Q values in the advanced tab, though the only way I know how to compare real Vs simmed is by impedance measurement.

In MJKís software it would be increasing stuffing density throughout the line plus in the vent with best overall performance achieved when the right TL length Vs tuning is found.

GM
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Old 3rd December 2012, 01:39 AM   #416
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THanks GM. I must admit I have been rambling on long enough that I may have forgotten some former post. I will try different port locations.
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Old 3rd December 2012, 06:51 AM   #417
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What is the major advantage of the reduced impedance peaks as seen in ZM's calculations included below?
My ignorant assumption is that it provides a more even load to the amp that should improve performance, but does this play out in real life as audible improvement?
This is a big deal when being driven by a high output impedance and why one must always tune to Fs for best overall performance/power transfer. With today's vanishingly low output impedance systems it only matters if the speaker's impedance drops below the amp's minimum rating.

There is group delay to consider though, so for higher Fs drivers it's best overall to tune them so that the lower impedance peak is damped.

Low Fs drivers tuned low have a higher group delay, but the vast majority of folks don't hear well enough down low, so by the time their hearing acuity improves, the group delay has decayed enough to be acoustically benign.

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Old 3rd December 2012, 07:10 AM   #418
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Is this reduced acoustic phase ripple the advantage of true Tqwt vs ML-TQWT, like mine? I can reduce mine with more stuffin, but not to the degree that you have achieved. OTOH, the impulse response from mine is very good, which i would think is an indicator of a quick cone response. Just trying to figure out what all these graphs mean. No where does MJK speak to these things.
Correct, ideally we want a flat frequency and electrical phase response, but they are hard to come by except over a narrow BW.

Yes, ideally we want the system to be extremely well damped, so there would be ~nothing under the curve and no HF ripple [ringing]. Unfortunately, the only time Iíve witnessed it is from a small theoretically ideal BLH designed specifically to see if it was possible and otherwise useless except for a near-field app as it had virtually no power handling capability over most of its pass-band.

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Old 3rd December 2012, 07:18 AM   #419
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Originally Posted by Zen Mod View Post
difference is , if you put it that way - that BR is always haroomph-ing through pipe (opening ) while TL (derivatives ) are much less using those openings for relaxation

dunno - I'm telling you - trust to GM's words (even if I sometimes can't grasp sole simple sentence he's writing )
Right, look at a BR Vs TL impedance.

You can always ask for a clarification, though no guarantees I can explain it further as I don't understand a lot of the underlying math.

GM
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Old 3rd December 2012, 07:51 AM   #420
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Originally Posted by buzzforb View Post
GM, What do you think of the enclosure 1.3 I modeled and how would your ideal enclosure differ. I have figured the port based simply on the area of the port diameter strecthed out into a rectangle, with the length being the thickness of the proposed baffle, about 1.25".

In detemining the rectangular port, is ther any difference if it stretches from one side to the other, like in Scottmoose' Pensil designs, or is it better to have it centered with a limit on width. Based on 1.4 design, a vent stretching across the 19" interior face would have to be 1.25" tall to equal the area of figured 2.75" port. I noticed in your big MLTL for the 416, the rectangular port was quite small.
Itís just a reflex, so little can be done to improve it, though shifting the driver down to 19.43Ē might fine tune it a little. In room, the vent may need some Ďcriticalí damping as most reflexes do IME.

Again, itís all about width x height aspect ratio, so a narrow slot will lower tuning more than the sim predicts due to friction losses.

True, but itís deep and itís loading a MLTL tuned with an inverse tapered TQWT. These cabs date from í69 when I only needed ~36 Hz tuning, so the vent was far larger and only ĺĒ deep, but as CDs, then DVDs, lowered the available LF I kept tuning it lower till now theyíre around 15-16 Hz after Ďcriticalí damping [the dense mesh screen visible behind the ĺĒ removable plate].

Since all this damping is combined with low tuning, the vent area can be smaller due to a lower vent mach even when pushed to hard with a 300 W/channel Mcintosh MC2300 or Altec 9444A/SA.

GM
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