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Old 2nd October 2005, 09:07 AM   #1
kyaloz is offline kyaloz  Australia
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Default HT SQ ported tuning frequency

Hi everyone,

Great forum massive amount of info!

Ok, what frequency are you guys tuning ported enclosures around for best SQ?

Or better still your opinion on tuning frequency for the following:

I have a DD9112 sitting on my shelf beckoning the HT room. It's music handling is 1600wrms(underrated) and I will be feeding it 2000wrms.

It will be running along side Aaron SW-240 (dual 10's) & Aaron ATS-5's (dual 8" towers).

An EQ for proper component matching is coming later.

thanks in advance for your help
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Old 2nd October 2005, 09:40 AM   #2
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There is no magic tuning frequency, it's entirely dependent on box volume and driver parameters. However, to maintain decent power handling at very low frequencies you should be tuning no higher than 30Hz, preferably a good few Hz lower than that.
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Old 2nd October 2005, 11:23 AM   #3
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Quote:
It's music handling is 1600wrms
It's music power handling is 1600 W = 800 Wrms.

Mvg Johan
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Old 2nd October 2005, 04:13 PM   #4
kyaloz is offline kyaloz  Australia
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800wrms is its power handling for a short burst at a fixed frequency or "burp".
1600wrms it its musical power handling as playing music produces far less heat than a burp.
3200w is its max power

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Old 2nd October 2005, 05:33 PM   #5
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I think you have the first and second ones the wrong way round. The point of burp testing is that it gets you the max you can out of the system, and this is not sustainable.

Anyway, a quick check indicates that because Vas is low you will struggle to accomodate the vent in the box due to it requiring large diameter and long length. Qts is a little on the high side for a vented box as well.

Is there a particular reason you want vented? Have you modelled a sealed box to see if it can give you the SPL you want?
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Old 2nd October 2005, 08:24 PM   #6
GM is offline GM  United States
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Greets!

Ideally you want the tuning to be well down into the room's pressure mode BW, so if you have a large and/or leaky room you need to go with a ~critically damped IB alignment (0.5 Qtc) IMO.

That said, my room doesn't measure any real gain and calcs not starting until somewhere around 6 Hz, but a 'stereo' corner loaded 16 Hz EBS alignment works well to get good SQ with a bit more gain in the audible BW. Note that an EBS tuned below ~(0.707*Fs) isn't a good plan IMO so I recommend a very low Fs driver and use as many as required to get the desired mechanical power handling, so unless your HT room is closet sized, probably best to stick it in an IB and use digital EQ to shape its in-room response.

FWIW, four 20.0Hz Fs HE 15" work well enough for me. When I escalated up to dual corner loased Servo-Drive Contrabasses to get a flatter in-room response to a lower cut-off, they shook my stick built/floating floor house to pieces pounding out special effects and low organ notes up to ~live levels in some cases, destroying most of the drywall joints in every room and cracking one of the foundation pillars under the listening room and still dealing with the consequences years later, so something to consider when determining a peak SPL/BW.

GM
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Old 2nd October 2005, 08:36 PM   #7
simon5 is offline simon5  Canada
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For best SQ, the best is to tune under 20 Hz hehe!

You could do 100 liters tuned to 18 Hz but you'll need to twist the port a bit hehe!

30mm Xmax, nice driver.

GM is right, the Fs is quite high, good luck.
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Old 3rd October 2005, 03:27 AM   #8
kyaloz is offline kyaloz  Australia
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Breaking your house with HT Classic, I love it!!

My room is 4x3m(13'x10') and enclosed, dedicated HT room.

The encl. does not have to be ported if you believe sealed will yeild better results.

The port does not have to be internal. I would make a feature out of it externally.

Also this sub is all I have available to me for a while. If I spend any more on the HT the missus will shoot me.

100L @ 18hz so far, anyone want to second that or beg to differ?
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Old 3rd October 2005, 05:15 AM   #9
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Making the Box a bit larger would allow a shorter vent for the same tuning frequency....

My suggestion:
Build a few ports into or out of the box with panels(if they're slot type ports) or plugs(for round ports) to close them off. You could try tunings at 18 24 and 30hz and also have a plug/panel to close off all the ports for sealed box operation. One box that can be 4 different enclosures sure beats building 4 different enclosures
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Old 3rd October 2005, 11:10 AM   #10
kyaloz is offline kyaloz  Australia
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Quote:
Originally posted by BassAwdyO
Making the Box a bit larger would allow a shorter vent for the same tuning frequency....
Do you mean a bit larger than the 100L (3.5cuft) mentioned before or larger than DD recomendation of 78L (2.75cuft)?

The changeable ports is a go'er. I'll build a trial box to determine best SQ then build a feature enclosure.
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