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Old 7th December 2009, 05:28 PM   #31
gibbed is offline gibbed  United States
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I suggest a 38 hz tapped horn, as seen here:
38 hz tapped horn, volvotreter

(mine is on page 2)
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Old 7th December 2009, 05:47 PM   #32
peace brainerd is offline peace brainerd
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Certainly,

Pluto + subwoofer

Whew!! Reading Mr. Linkwitz' webpages is not for the faint of heart. The attention to detail is a little forbidding to the novice. It challeges any assumption I might have of integrating a sub with any ease.

Quote:
To lighten the demands on the woofer/midrange driver a 100 Hz crossover frequency would be necessary with a LR4 acoustic filter response. The relatively high crossover frequency then requires that the radial distances from each subwoofer and tweeter to the listener should differ by less than 2 feet (60 cm).
Quote:
An impedance measurement of the driver in the sealed box can yield the the important parameters f0 and Q0 for the 2nd order electro-mechanical filter that controls the acoustic highpass response at low frequencies. In this case f0 = 74.3 Hz and Q0 = 1.57 as calculated by using the formulas in f0Q0.gif.

To extend the low frequency response these two parameters will be changed to a target of fp = 20 Hz and Qp = 0.5 by using a biquad equalizer. Values for standard components are calculated by using the pz-eql.xls spreadsheet.

R1 = 5.62k, R2 = 1.96k, R3 = 75k
C1 = 1000 nF + 390 nF, C2 = 100 nF, C3 = 100 nF
which gives
f0 = 76 Hz, Q0 = 1.59, fp = 21 Hz, Qp = 0.49
Adc = 22.2 dB
Quote:
some of the low frequency content of the input signal must be shifted away from PLUTO so that it is reproduced by the subwoofer instead. This task is not as straight forward as it may seem, because PLUTO's acoustic low frequency response is that of a 2nd order highpass filter with -3 dB corner at 60 Hz. Cascading this filter with any standard 100 Hz electrical crossover filter highpass section will not result in a 100 Hz acoustic crossover. PLUTO's response determines the missing electrical filter response, that when added leads to the desired LR4 acoustic crossover response. The block diagram of the w-ASP shows the necessary circuit elements for crossover filters and equalization of both PLUTO and its subwoofer PLUTO+.
Quote:
To obtain the desired 100 Hz LR4 acoustic crossover behavior for the subwoofer it is merely necessary to cascade an electrical LR4 lowpass filter (U4) with the biquad equalizer (U5B). The LR4 acoustic highpass filter for PLUTO, though, requires more effort since that speaker's low frequency response has a 2nd order roll off below 60 Hz. This must be equalized - again with a biquad (U2A) - to become an acoustic highpass with fp = 100 Hz and Qp = 0.7 to form one of the two LR4 crossover highpass filter stages. The other stage (U1B) then uses the standard electrical LR4 filter topology.
Quote:
R1 = 10k, R2 = 16.2k, R3 = 3.48k
C1 = 330 nF + 390 nF, C2 = 100 nF, C3 = 1 uF + 1 uF

The complete 100 Hz LR4 electrical highpass filter for PLUTO is shown below. Together with subwoofer equalization and lowpass filtering it can be easily implemented on the w-ASP printed circuit board. The pcb has a general topology that makes it useful for any woofer and its crossover.


Holy $hit. So much for slapping the 10" peerless inna box and wiring up the ol' Foster amp, eh? Or is this Nth degree of perfection just that? An Nth degree that won't be too great a loss to most of us? The quotes above certainly do some abuse to the suggestion by AdamThorne earlier in this thread that...
Quote:
Another reason you might not see a lot of write ups on builds like this is that there isn't much to doing it.
With respect to AdamThorpe, I do understand what he's saying actually. And I hope that it indeed turns out to be the case... in this case.

And with regard to Mr. Linkwitz, it's extremely encouraging to see that this thread has led to his doorstep. I believe that with regard to the criteria I've described above for my personal subwoofer requirements, he seems sympathetic. That's not bad company.

Last edited by peace brainerd; 7th December 2009 at 05:58 PM.
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Old 7th December 2009, 06:00 PM   #33
AdamThorne is offline AdamThorne  United States
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Quote:
Originally Posted by svejkovat View Post
The quotes above certainly do some abuse to the suggestion by AdamThorne earlier in this thread that...

With respect to AdamThorpe, I do understand what he's saying actually. But then again.....
Well, to be fair, the Pluto+ subwoofer is not exactly your average budget sub...
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Old 7th December 2009, 08:17 PM   #34
littlemike is offline littlemike  United States
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Quote:
Originally Posted by svejkovat View Post
littlemike, at the risk of sounding like I want too much for too little....

(wait a sec, that's exactly what I want! Otherwise why work this hard at it?)

- SNIP -

Is the 830668 worth the extra 14 dollars (pretty insignificant difference all considered)? Or are these drivers pretty much neck and neck in a sealed sub?

Le/Re is a better ratio on the 830634 with slightly more xmax, but the 830668 seems to have a slightly better (lower) freq response and Fs. Are all these too close to matter? Do they share the same motor structure? Is a Nomex cone anything to get hot and bothered about? (rimshot)


Thanks so much all of you for entertaining these questions.
For what you initially described, they are functionally identical. Between these two, I would choose based on price. Both drivers will work fine, but if I can buy 2 for the price of one, I'll choose the cheaper ones.

As far as the complexity - Linkwitz's stuff is exceptional, but certainly would not be described as either "simple" or "budget". It is possible to complicate anything if one tries hard enough. It is also possible to simplify things to the point where they lose value. You can make things as simple as, or as complicated as you'd like. Personally, I'd start simple.

"Make everything as simple as possible, but not simpler."
-- Albert Einstein

"Any fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."
-- Albert Einstein
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Old 7th December 2009, 08:22 PM   #35
littlemike is offline littlemike  United States
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BTW - since the internet may not catch my tone - I meant no offense to anyone with those quotes.

Einstein was a far, far smarter man than I, I occasionally find guidance in his quotes.

Back to your regularly scheduled discourse.....
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Old 7th December 2009, 08:29 PM   #36
badman is offline badman  United States
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Just a heads up, since this is budget oriented: Zalytron has a very nice sale on their inexpensive sub drivers.

Zalytron
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Old 7th December 2009, 08:57 PM   #37
Pallas is offline Pallas  Pakistan
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Quote:
Originally Posted by svejkovat View Post
Is the 830668 worth the extra 14 dollars (pretty insignificant difference all considered)? Or are these drivers pretty much neck and neck in a sealed sub?
The only thing that might make the stock model "worth more" than the Genelec buyout is that if it breaks it's a stock model, so you can replace it with the exact same thing. But then again, sealed subs are fairly tolerant, and they do use the same basket/screw hole locations, so if you buy the 38 dollar one and it breaks, replacing it with the stock model will be just fine.

So in short, buy the cheaper one while they're still out there.

Quote:
Originally Posted by svejkovat View Post
Do they share the same motor structure?
I haven't compared coil lengths, but for simple cost reasons one would expect them to share a motor structure. The Genelec buyout might have a slightly different cone/coil/surround, but for subwoofer use that's not a big issue.

Quote:
Originally Posted by svejkovat View Post
Is a Nomex cone anything to get hot and bothered about? (rimshot)
No. Well, maybe if you build your box out of metal and your house catches on fire.
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Old 7th December 2009, 08:57 PM   #38
BP1Fanatic is offline BP1Fanatic  United States
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This looks looks REAL nice for $15.00 a piece on sale!
Zalytron Model #800PL, 8.0 in, 7.88 ohm, fs = 32hz .QTS = .45, VAS = 55 liters, Xmax = 7.9mm, stamped basket, rubber surround, 88 db @ 1w/1m, List = $45.00.
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Old 7th December 2009, 09:54 PM   #39
TheSeekerr is offline TheSeekerr  Australia
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Pluto + subwoofer

EDIT: Oops, for some reason my browser didn't load the second half of the thread, so I'm a bit behind the times!

Last edited by TheSeekerr; 7th December 2009 at 09:58 PM.
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Old 7th December 2009, 11:02 PM   #40
mightydub is offline mightydub  United States
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I put this 8" Dayton subwoofer Parts-Express.com: Dayton RSS210HF-4 8" Reference HF Subwoofer 4 Ohm | subwoofer Rss210hf-4 8" subwoofer dayton reference rs sub dayton loudspeaker in a sealed cube 12" on a side, double thick front, with a homebuilt plate amp and crossover/EQ. I got the driver for $80 when PE had it on sale. EQ was necessary because of the small sealed box, it does the job very nicely. Has enough oomph at the low end to scare the cat when watching movies, though my main use is for bass extension for a pair of homebuilt small 2-ways.
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