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Old 5th August 2004, 04:33 PM   #1
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Question Low Q sealed design for Adire Tempest

Hi all,

Has anyone built the low Q sealed design for the Tempest from the Adire website? I'm almost ready to buy one of these drivers, and I had the low Q design in mind (for music), but the enclosure is kind of big.

Anyone have any suggestions for a smaller enclosure that gives good extension? I'm looking for tight, extended, non-boomy output , and I'll be happy to trade lower SPLs for better extension.

All suggestions gratefully received. This is a first time build for me, so it would be nice if any suggestions weren't too complex (hence the temptation for a sealed box... maybe less to go wrong?).

regards,

Glenn.
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Old 5th August 2004, 05:12 PM   #2
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I came close, but no, not quite the low Q. I built mine as a 24" cube out of 1" MDF, so it falls in between the mid Q and low Q Adire designs, somewhere around 165L. I'm happy with it. I'm planning to update it a bit in the future with a better veneer job, a bit more stuffing, and T-nut driver mounts, but just haven't got around to it.

Personally, I would have issues with the big box. Basically, to me, when they start getting that big, you have to wonder if getting an EQ device isn't the better way to go, especially if space comes at a cost.
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Old 5th August 2004, 07:32 PM   #3
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Quote:
Originally posted by leadbelly

Personally, I would have issues with the big box. Basically, to me, when they start getting that big, you have to wonder if getting an EQ device isn't the better way to go, especially if space comes at a cost. [/B]
Yes, I reckon you've nailed it with the EQ comment. I've started wondering if a Linkwitz transform circuit would work, but I'm not up to speed on that just yet.

I'm trying to keep the wood-work simple, but I don't have a problem with a bit of electronic trickery, and chucking some amplifier power at the problem if that gets me there.

Thanks for the comments.

Regards,

Glenn.
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Old 5th August 2004, 07:46 PM   #4
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Well, you don't have to jump all the way to an LT circuit. You can find sub amps with variable boost settings. Those might very well do the trick.

The big subs are harder to live with long term than when you first start researching and get excited with the "tight bass" hype (if you are putting them in a main living area of of modest size). At first, my sub was that and nothing else. Then, I decided it needed to serve as an end table so I could add a chair. Now I look at it and think "Can I ever get a sectional couch in this room?"
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Old 5th August 2004, 07:49 PM   #5
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Quote:
Originally posted by Glenn Booth
with the EQ comment
But that is adding more electronics in the path.... for sealed build as big a box as you can get away with, then if the Q is still too high make it aperiodic.

dave
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Old 5th August 2004, 08:12 PM   #6
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I have the exact same issue and I think I have come to a conclusion on it. What I am planning now is a ~2.4 ft3 box for the Tempest with the Rythmic A350 SE Amp with their LT add-on card. As far as I can tell, you just need to give them the specs on your driver (or tell them it's a Tempest), your box size, and what kind of extension/Q you are looking for. They will build the LT or send you the board so you can order the parts and build it (but it's only $40 done by them) and it hooks up inside the amp, so you don't need to build anything. Anyway, I settled on ~2.4 ft3 because that is the size where 350W will not ever cause the driver be exposed to over-excursion. Check that in UniBox to be sure, I don't have the specs with me right now. I have not called Rythmic to confirm any of this but it seems a great way to go to get everything I want for a relatively low price (especially when you factor in the cost of veneering a ~240L box and the SO complaints). You should come out under $400 for the driver, 350W amp, and LT - you'll have plenty of SPL and for my purposes, an F3 around 23Hz !!! Of course, my room is about 5500 ft3, so I need a sub that will go deep flat.

Good luck and let me know how it turns out if you go this route.
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Old 5th August 2004, 08:14 PM   #7
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Quote:
Originally posted by planet10


But that is adding more electronics in the path.... for sealed build as big a box as you can get away with, then if the Q is still too high make it aperiodic.

dave
Sounds like an interesting idea, but 1. I have no idea how to tune it properly and 2. I don't really understand how aperiodic boxes work (those are in the wrong order, but you probably get my meaning).

Putting more electronics in the path is something I understand better than aperiodic enclosures. My soldering is better than my carpentry.

Regards,

Glenn.
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Old 5th August 2004, 08:40 PM   #8
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Quote:
Originally posted by Glenn Booth
Sounds like an interesting idea, but 1. I have no idea how to tune it properly and 2. I don't really understand how aperiodic boxes work (those are in the wrong order, but you probably get my meaning).
Aperiodic is still much a try & try method... basically you add some leaks to the sealed box -- i've found the thing slots as in the Dynacos http://www.t-linespeakers.org/classics/dynaco.html the easiest to work with, but an array off holes (as in attachment) works too. You then makle these leaks resistive by blocking them with open cel foam, compressed fiberglass or such. You vary the resistance until you get the flattest impedance curve (or use GMs click test -- i think he mentions it on the forum, not having used it i can't remember. I've also gotten pretty close tuning by ear (the one pictured needed more resistance than i expected (ie i started with too many holes) it was a good thing it had the raised base for me to sqaush a mass of foam & fiberglass up against the bottom. It all worked out in the end, with 2 Philips 12" working well in a box size more suited for 1.

dave
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Old 5th August 2004, 08:47 PM   #9
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Dave, you're getting younger in your avatar again. What gives? Feeling re-energized in this Olympic year?
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Old 5th August 2004, 08:59 PM   #10
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I'm building a sealed bass speaker (actually two for a 3-way system) with Lambda SB12 in a 130 liter box. This should give a Qtc of around 0.85. With stuffing (sheep wool) I hope to get it down to 0.8.

Making a box with Qtc of 0.7 would require twice as large an enclosure (260 dm^3). Apart from the size (they are already huge, measuring 83 * 51 *63 cm) it is very very difficult to make a good, non resonating enclosure for this size. I use 2 and 3 layers of MDF right now with thicknes up to 68 mm and a lot of bracing, 1 M^2 leadbitumen and I'm still not completely satisfied.
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