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Old 8th December 2004, 06:24 AM   #1
jondoe is offline jondoe  Romania
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Question Opinions on speaker

So what any of you guys think is possible with this speaker ?
www.maniac-sound.com -> home -> cdcone
The speaker is 30412

The full link in case you want a quick jump is
http://www.maniac-sound.com/01 Home/cd cone/30412.html
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Old 8th December 2004, 10:11 PM   #2
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it has a high Fs low xmax and wouldnt be great for a subwoofer unless its a car audio application, even then it wouldnt perform very well.
The golden rule of DIY:
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Old 9th December 2004, 12:08 AM   #3
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Default And on top of what BassAwdyO said...

The Qts of this woofer is 1.51 !?! That's a very poor recipe for quality bass, even IF it had a low Fs and high Xmax. Such a driver will present low end response with a peak near the resonant frequency of the box, not a good thing. The peak will be about 4 dB if the box is large enough, higher if the box is too small.

All that said, there's an error in the specifications. It lists Vas as 2.9 liters. Even if it's supposed to be 29, that's still much lower than I've ever seen for a 12" woofer. I'd believe 129.

Aaron Gilbert
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Old 9th December 2004, 08:42 AM   #4
jondoe is offline jondoe  Romania
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Default I bought some of those ...

The Vas may be wrong but it sounds the same (allmost) in a 10l closed box as well as in a 100l one. I know, i built one. The low range is, welll, pretty low. Xmax is low allthough. I thought about it too. And the price is somewhere in between 35-45 $.
It works pretty well, anyway better than all the fake drivers that i can find in my area. Now, i could had gone for some good (original, brand) drivers but around here the price is about 2-3 times of what i can see on the retail shops online and it's kinda hard to buy online or from overseas (difficult payment). So, in a sentence, how bad is it for a home sub that isn't interested in a whole lot of power and for going well below 40 or let's say 35 ?
From my listeing tests i'd say it goes linear about to 30 Hz with peak to about 35-37. From my understanding, Qt is the driver's ability to resonate around Fs so this one will have 51% more Spl at Fs right ?
Also, i really wanted to go for a closed box design so i did. This one is just right for such a task. Minuses are low Xmax and low Wattage (max 100W sinus real power) despite the 300W advertised ( i never believe many of those figures)

I kinda like it's sound (again, compared to the alternatives).
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Old 9th December 2004, 06:28 PM   #5
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Default Is that $35-45 US dollars?

If so, that's not a bad price for the amount of air it moves. However, the super high Qts is still a major concern. Qts is not the ability of the driver to resonate at Fs exactly. Rather, it's the amount of control (damping) that the driver has at Fs. Fs is the natural resonant frequency of the driver, and as such, the woofer will want to move excessively if not controlled. As far as the amount of extra SPL this woofer has, it doesn't quite work as a percentage of Qts as you speculated. However, in this case, it's quite a bit more than 51%. 4 dB is actually slightly more than what you'd get from twice the input power. The thing to remember is that all the extra output, is output that is not present in the original signal, it added by the speaker itself, which most regard as a bad thing.

However, in the end, it really comes down to how the speaker sounds to you and what you like. If you're happy with it, that's what matters. You're right that the woofer should have good low end extension, for a sealed box anyhow.

Aaron Gilbert
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Old 10th December 2004, 06:15 AM   #6
jondoe is offline jondoe  Romania
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Default Yep, U$ dollars, it may even be less...

I am currently using it with a bridged tda7294@2x25Vcc with a 800W transformer that gives about 220-230 W max (typical 200W & low Distort about 150-160W), 12dB/oct lowpass linkwitz-riley before the amp & it sounds good. To liniarize it a bit & reduce the bump at fs due to high Qt i'm building a 3xTDA7293@2x50vcc (the tda's are in parallel) amp with a 1500 W transformer and a linkwitz transform. The drivers are both in the same enclosure made out of 4cm (1.57inch) thick MDF with about 65 liters and connected in parallel. They are connected directly to the amp so i guess that this amp will provide pretty good control (damping factor) for the speakers.

One experiment that i tried was to mount a 12db/oct passive lowpass L/C filter @ about 100Hz between the amp & the sub. Guess what ? Just as i expected, the excursion was about 50% bigger than without this filter, even tho it has only about 0.1 ohm resistance. I guess the amp saw a much greater impedance on it's output than just the speaker's due to filter's high reactance (inductive).

So, about the extra movement that was not in the original signal & it is in the speaker's at fs, i'm not pretty bothered about it. The linkwitz transform will get it down pretty good. Even without it it's great.

Considering i've heard 200-300euro subs sounding not as good as this one, or drivers blowing up at 100W or highly distorting at 80W...

I've seen only some magnat car speakers that were quite good in the car but not in a home & you can't find those real ones anymore (which were quite expensive anyway) just some lame fake immitations. Pretty much everything on the market in my area are just some lame fake immitations of the real thing because, well, they are cheap. Even if you would go to a so-called pro shop they will sell you the same **** for 4 times the money.

So thanks 4 the replys. I really had mi mind made about these drivers but just as an afterthought i wanted to compare my opinions & understanding with somebodyelse's who has a little more experience than me. (This is my first speaker project & i didn't know about Thiele/Small parameters & what they represent but reading through the speaker's manual i figured alone what they meant, well, most of them & then got to using the unibox design program to see what speakers deliver what i want).

Oh, and if you go to a audio (pro or not) shop and ask about T/S for a xxx speaker they will look at you as if you cursed them.

Thanks again.
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