qtc and fc of velodyne spl-8?

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Why, do you have a velodyne driver you need to use?

QTC between 0.5 and 0.75 are good for music listening, with 1.0 being okay, but with more boom. 1.0 Probably best if you are building main speakers with small drivers and no subwoofer but not for much else. I would stay between 0.5 and 0.8 for my own use. As I recall, the Velodyne SPL-series goes pretty low, and it uses EQ in the amp to do it, I think. That limits headroom. Instead, start from scratch. What will your subwoofer be used for, and what sort of sound do you like?
 
no i don't have a velodyne driver,, just wanted to know the qtc and fsc as a target point. =)

I don't really know if i should use PR or sealed. I got 2-3st TangBand w8-740c and 1 RCM BXP-10 Passive Radiator.

current sys looks like this:
Front: w8-740c, 33L @ 30hz (Qa 10)
w4-657s, Sealed.
28-847

surround:
unlimited amount of w3-871s =) 1 L Sealed

Subwoofer:;
Well i've got an old Peerless 830373 8" (not really a subwoofer)
:D

If i use 3 driver, then i maybe could build a sub that looks like Martin Logan Descent ( depth )

I've been reading much at http://sound.westhost.com/index.html about power distribution and the Linkwitz Transformer.

I will post some simulation i've been working on, soon.

Why and what subwoofer should i build, is the fronts enough for HT ? Able to do 109dB >28hz with fronts and not considering roomgain. (only simulation)
 
For HT you probably want a vented sub. Your target should be based on the output at your listening position. Most mains won't play that loud cleanly at the listening position. In fact most play quite a bit less than that.

Typical floorstanding mains with a pair of 6.5" midbass drivers would play probably about 20 watts cleanly with about 87db efficiency (1w 1m) >>> 100 db @ 1m
94db @ 2m
91db @ 3m

In order for a subwoofer to match that output, it needs 6db less capability at 20 Hz due to room gain. The sub would only need to produce 94db at 1m.

In practise you probably want more due to the insensitivity of the ear to low frequencies and due to the dynamic nature of bass in movie sound tracks. To achieve 105 db at the listening position you need to be able to produce 108 db into half space.
 
Maybe like this.

This is 2st w8-740c using absolute max power. 460w, Grey.


An externally hosted image should be here but it was not working when we last tested it.



Then i have 1st w8-740c i can build a small Linkwitz Transformer sub, fsc 25 and qtc 0.85. Only for music. Yellow.

This is without room gain.

THe higpass filter on the right, is an average of power amount under 40hz in music. Just so that sealed boxes having flat response down to 20hz but can't take that excursion still can have flat response. The main reason is to playback the sound just as it sounds in real world, everybody knows =) http://sound.westhost.com/linkwitz-transform.htm (power distribution by Gareth Abrey)
 
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