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Old 29th June 2013, 05:09 AM   #1
wrlco is offline wrlco  United States
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Default Aperiodic enclosure for TAD 1603

In Dec 2005 GM wrote the following regarding aperiodic (AP) designs: "When used as originally intended, among other things it allows smaller/shorter vents in alignments that will benefit from it. F3/Qtb goes down and you wind with what is essentially a ~low Q sealed alignment above Fb with gain. Indeed, if a LspCad Pro sim is to be believed, then my 'critically damped' 20 ft^3/~16 Hz Fb EBS 'subs' have a slightly lower GD in the audible passband than an IB. For sure, they have much more gain down low where it counts and even corner loaded only elicits other's observations of 'life-like'/tight/etc. performance."

This seemed exactly what I was after so I started studying all I could find on AP, which unfortunately was not much. Recently I heard a pair of Shindo Latour speakers that claimed to be AP designs from Japan. They were very revealing and among the most natural and dynamic non-horn speakers I have ever heard.

I own a pair of TAD 1603s currently in BR enclosures designed by George Augspurger as recording studio monitors. They are very good, but lack the dynamics and scale I would like in my 16'x26'x10' listening space.

The TS figures for the TAD 1603s are as follows: Vas: 10.73 cu.ft.; Fs: 28 Hz; Qts: .342; Qms: 6.8; Qes: .36; Re: 6.6 ohm; Sd: 881 sq. cm; 85 gram cone wt.

I have come up with a box design with internal dimensions of 30"x20.5"x42.640625" equaling 15.17591689 cu.ft. volume. The ducts, 6 of them, would each be 2.5"x9"x 2" in length exiting the bottom of the box which would be standing on 2.5" legs. Tuning would be slightly less than Fs, or should it be calculated at .7072xFs and the ducts made longer?

I am interested in any and all reactions to this design and changes which you might think appropriate.
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Old 29th June 2013, 12:48 PM   #2
Scott L is offline Scott L  United States
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Default TAD 1603's

Greetings,

You bring up a lot of points worth discussing. First, you listed every spec except the BL factor. But from what I can see, this is a fine woofer capable of dynamics. Ultra dynamics? IMO not in a "box". I think your 16 cubic foot box is just too big. The TAD's are professional woofers; they are not subs.
If I were limited in design to just one (per side) 15", I'd put it in a built-like-a tank classic bass-reflex. In this case, 6.75 cubic feet tuned to 33Hz. And I mean heavy-duty, double walled, and spiked to the floor.

From my experience, and what I have heard, the only way to get "ultra dynamics" from a single/per side 15" is to horn load it. If you're going to do that, then a real true dedicated subwoofer system would be absolutely required.

Get yourself a copy of the Sheffield release "James Newton Howard and Friends" on CD and if your are not totally thrilled and left exhausted emotionally after listening, then you don't have enough dynamic expression in your loudspeaker system.
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Old 29th June 2013, 10:06 PM   #3
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TL-1603 Low-Frequency Loudspeaker - Pioneer TAD
An ideal BR enclosure for this driver (not counting with others/George Augspurger alignments) 178.0 L tunned to 25 Hz.
(178L = 6.2860ft³)
This alignment can give you 20Hz@F-12dB with guaranteed best LF achievable for this driver. Different alignments are possible, this one above is (int. volume) for each driver, and less than the 500W (~350W) are enough to bring them to Max Linear Peak Excursion. Some engineers use smaller enclosures than ideal for different objectives like pro-sound.
I will check later in a couple of days, for validation of your data and more simulations for confirmation. I can not confirm the other subject, on the aperiodic (AP) design, with my software but others can. Regards.
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Old 29th June 2013, 10:27 PM   #4
Scott L is offline Scott L  United States
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Quote:
Originally Posted by Inductor View Post
TL-1603 Low-Frequency Loudspeaker - Pioneer TAD
An ideal BR enclosure for this driver (not counting with others/George Augspurger alignments) 178.0 L tunned to 25 Hz.
(178L = 6.2860ft³)
This alignment can give you 20Hz@F-12dB with guaranteed best LF achievable for this driver. Different alignments are possible, this one above is (int. volume) for each driver, and less than the 500W (~350W) are enough to bring them to Max Linear Peak Excursion. Some engineers use smaller enclosures than ideal for different objectives like pro-sound.
I will check later in a couple of days, for validation of your data and more simulations for confirmation. I can not confirm the other subject, on the aperiodic (AP) design, with my software but others can. Regards.
Hello Mr. Inductor:
I guess you are directing at me ? In a QB3 alignment, box tuning is always higher then the driver's Fs. I use the D.B. Keele re-writes as a reference. I don't use sims, I do long math. The ratio set forth by the drivers' Qts is
1.15fs= fb so 32.2 is exact.
From your link I see the Bl spec is 19.5 This is one fine driver.
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Old 30th June 2013, 07:04 PM   #5
wrlco is offline wrlco  United States
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Thanks to both Scott L and Inductor for their input. In Thuras original BR patent, it is suggested that Vb should equal Vs and likewise Fb = Fs (or be slightly below FS according to some designers). This would make for rather long Lv; in the case of the TAD 1603 around 9.5" with Auspurger's correction for vent length. That is the reason I had hoped to use the aperiodic approach to shorten the vents and flatten the impedence hump. What do you fellows think?
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Old 30th June 2013, 09:22 PM   #6
Scott L is offline Scott L  United States
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Quote:
Originally Posted by wrlco View Post
Thanks to both Scott L and Inductor for their input. In Thuras original BR patent, it is suggested that Vb should equal Vs and likewise Fb = Fs (or be slightly below FS according to some designers). This would make for rather long Lv; in the case of the TAD 1603 around 9.5" with Auspurger's correction for vent length. That is the reason I had hoped to use the aperiodic approach to shorten the vents and flatten the impedence hump. What do you fellows think?
I'm pretty sure both Inductor and myself are in agreement that aperiodic
is something we are not comfortable with. In "theory" the aperiodic is simply a sealed box with numerous small ports cut into the back panel and covered
with some sort of foam for damping. It's supposed to lower the impedance peak of a sealed box. It won't give you the deep bass of a BR.
In my above example, a nice quasi-butterworth 3rd order vented alignment requires 2 vented ducts, 4 inches in diameter, 6.29 inches in length.

I have no idea about Mr. Thuras. I learned it from Thiel/Small/Keele/Weems.
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Old 30th June 2013, 10:42 PM   #7
wrlco is offline wrlco  United States
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Yes, aperiodic is often referred to as a "leaky sealed box," but such alignments have proven highly successful for Dynaudio and Seas loudspeakers. In addition the famous Onken speakers have been considered aperiodic by some commentators, though others have considered them highly damped BR and even modified 1/4 wave TML enclosures. It would seem that box design is more a continuum then individual types of enclosures...rather like the continuum of horn flare rates from exponental to conical; so from closed box to open baffle. What do you think?
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Old 30th June 2013, 11:19 PM   #8
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Here is an exmple of an MLTL
Attached Files
File Type: pdf TAD 1603.pdf (196.9 KB, 135 views)
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Old 1st July 2013, 05:24 AM   #9
wrlco is offline wrlco  United States
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Buzzforb,
Thanks so much. I will study this with great interest.
Bill
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Old 2nd July 2013, 01:31 AM   #10
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Aperiodic and resistive-vent have a lot of semantic overlap; Richard Small referred to this class of enclosure as "resistive-vent" in an unpublished chapter of his doctoral thesis, and that's the term I prefer to use.

One property that distinguishes RV enclosures from canonic T/S alignments is the much broader vent tuning. When you directly measure the spectra of a T/S aligned vented-box, the vent output has a rather narrow peaked spectra, centered on the box frequency.

RV enclosures, depending on tuning, may have much broader tuning for the vent ... it's resistive, after all, and this lowers the Q substantially. For example, the vent output of the Ariel is pretty much flat from 30 Hz to 100 Hz, and doesn't look like the output of a vented enclosure at all, but more like a subwoofer.

I see two possible benefits to RV alignments: they are less sensitive to dynamic BL variations from the driver, since there is resistive damping provided by the vent as well as the power amplifier (the part that is sensitive to BL variations), and the felt, wool, or cotton damping in the vent suppresses organ-pipe modes in the vent.

The difficult-to-characterize properties of felt, wool, or cotton damping makes the modeling process more awkward, but I personally like the sound of RV and TL enclosures, even if there's more cut-n-try in the building process.
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