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Old 10th March 2005, 08:17 PM   #1
bigwill is offline bigwill  United Kingdom
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Default Low Qts woofer

I have my eye on a nice but cheap woofer driver with a Qts of 0.27, and a VAS of around 120L, and an FS of 26Hz. What type of enclosure would it be best for? I'm thinking a TL because of the low Qts, but I'm not an expert on these things. Any suggestions? (Note: I plan to make stereo woofers, if that's helpful)
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Old 10th March 2005, 09:49 PM   #2
Mark Kravchenko --- www.kravchenko-audio.com
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Default Check for online enclosure calculators

Bear in mind that generally spealing that a low qts driver will have a fairly quick roll of in the low end. It will benefit the most from a vented enclosure.

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Old 10th March 2005, 10:05 PM   #3
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The downside of a low Qts driver in a basreflex is that it, in order to get low, will have quite a big groupdelay. On the other hand that doesn't seem to bother a lot of people out there. It's also the easiest solution I guess.

Low Qts drivers are suited for hornloaded but you'll need a huge enclosure to get low.

Personally I use a low Qts driver in a TL (0,297), with an smaller mouth than throat. It's not tuned at the Fs but a little bit higher to get a flatter response. It was simulated with AJ-horn.

Mvg Johan
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Old 10th March 2005, 10:30 PM   #4
bigwill is offline bigwill  United Kingdom
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You'd think the magnet having more control over the cone would give you deeper bass, wouldn't you
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Old 11th March 2005, 07:05 AM   #5
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Yeah, you would think so. Too bad that deep bass and efficiency are about the opposite of each other.

If you want deep bass, Xmax, Sd and Fs are the more important factors. Xmax x Sd = Vd (good for comparing drivers). But you still have to use the right Qts driver for the right enclosure.

A Qts below 0.3 is generally more suited for hornloaded, between about 0.3 and 0.45 for basreflex, higher for closed and dipole. It isn't a strict border, they overlap.

A low Qts will generally go together with a high BL and thus efficiency.

For a basreflex subbas enclosure a Qts of about 0.34-0.38 would be pretty nice. As told lower Qts is possible but groupdelay will be skyrocketed. In Europe it's almost fashion lately to make low Qts drivers.

Btw: Cheaper drivers will most of times have an low Qts and a smaller Xmax, or a big Xmax and a high Qts. That makes it easy to see what kinda driver you're dealing with.

Personally I use a PA-driver, so a low Qts/high BL is welcome in that case. It makes the f3: 30 Hz with getting a continues SPL of 126 dB (at 100 Hz), but it takes a 500 ltr enclosure to do so. Hornloaded would turn out much bigger (for this driver) to achieve 30 Hz efficiently, but SPL would be even higher.

The TL only sounds good with HT and slow music in my opinion.

Mvg Johan
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Old 11th March 2005, 07:22 AM   #6
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Quote:
Originally posted by bigwill
You'd think the magnet having more control over the cone would give you deeper bass, wouldn't you
It does give more control over the cone. The problem is in the fact that to extend the bass the reflex system adds a second characteristic to the mix which worsens the damping overall.
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Old 11th March 2005, 12:21 PM   #7
bigwill is offline bigwill  United Kingdom
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Why wont a t-line tuned to about 40Hz give me deep and fast bass with this thing?

The model in question is an MCM 55-1480.



Another option I'm considering is the MCM 55-1245. This is even cheaper, and has an "easier" Qts to work with. If I got these I would probably use them in a sealed cabinet since WinISD is telling me that it'll make a pretty good sub. Which driver should I get out of the MCM 55-1480 or MCM-1245?
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Old 11th March 2005, 01:28 PM   #8
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I would say that do not be frightened that a vented design will be uncontrolled. If properly done a vented design can be superb.

Bear in mind that cheaper drivers are generally less linear and also have poorer excursion abilities.
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Old 11th March 2005, 02:10 PM   #9
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One possible sub application for low QTS woofers is an ELF but you need:

1.) quite some power
2.) enough x-max
3.) a sturdy driver

An example can be found here:

http://sound.westhost.com/project48.htm

Regards

Charles
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Old 11th March 2005, 05:27 PM   #10
bigwill is offline bigwill  United Kingdom
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I doubt these drivers will be up to that
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