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hz numbers on a 15" 2 driver (Read 38767 times)
Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #150 - 05/19/06 at 22:48:52
 
Not a bad idea 60.
I'll tweek some more based on John's advise. I have faith the man can help. He seems to be focused on bassboy and my projects fairly intently. He's got MUCH more experiance and knowledge than I. He's also got a home theater, so he might just have the edge on LFE's for soundtracks vs. music.
I don't mind tweeking, but like J_Rock said, it gets old after awhile. Especially when I thought I knew something about audio/video, and as it turns out, I know just slightly more than nothing. Tweeking is free. Being of "average income", I can't justify the purchace of the "just buy the high-dollar piece and be done with it" philosophy.  :(


Bob
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John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #151 - 05/19/06 at 22:53:47
 
Bob,

Check my post above, in case you missed it.  If you want to think of ports like air brakes on a truck, then below tuning you have a busted air line.
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J_Rock
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #152 - 05/19/06 at 22:55:02
 
Without a doubt the HWK will go that low.  Bob would just need different drivers that sweep more air.  and to lengthen ports.  The reason the HWK is a club bass cab is the tuning of the chambers, the top chamber and the bottom chamber are tuned signifiacantly higher than one would tune to get the really deep bass LFE channels contain.

(I would say the exact tunings, but then someone could easily copy the HWK design.  So Lets just say its too high for Bob's Subs to go low.)

As far as having two subs~
I think subs should be used for the really low frequencies.  From 10 to 80Hz max.  Thats 3 octaves.  Not a lot to ask of a main to go down to 80Hz.  And 3 octaves isn't alot to ask of a subwoofer.  SO as long as the subwoofer design gives clean extension deep and distortion free up top, there should be no need for two subs.

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J_Rock
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #153 - 05/19/06 at 22:57:12
 
[quote author=John in CR  link=1145573673/150#152 date=1148075627]Bob,

Check my post above, in case you missed it.  If you want to think of ports like air brakes on a truck, then below tuning you have a busted air line. [/quote]


this is an excellent analogy.  

Below a port's tuning in a normal ported box the Air behind the sub looses control over the sub's movements.   This is why You hear a klopping sound.  Below the port tuning, the ports no longer resist the Sub's motion so they flop around...

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Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #154 - 05/19/06 at 23:05:31
 
[quote author=J_Rock  link=1145573673/150#154 date=1148075832]

Below a port's tuning in a normal ported box the Air behind the sub looses control over the sub's movements.   This is why You hear a klopping sound.  Below the port tuning, the ports no longer resist the Sub's motion so they flop around...

[/quote]


By that reasoning, wouldn't DEcreasing diameter of top port help regain cone control?

John, That's a lot to chew on. Didn't understand totally after reading the first time.  Signing off here at work, will re-read again in the am.

Bob  (THANKS ALL)
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« Last Edit: 05/19/06 at 23:07:41 by Bob »  
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J_Rock
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #155 - 05/19/06 at 23:07:31
 
Nope, decreasing the diameter while keeping the same length raises the the tuning of the port.  Above that tuning everything is okay, but below you loose control.


If you really want to know why a port losses control below tuning I am sure someone can explain, but Its really not important the HOW or WHY.  Just know that it happens.
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Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #156 - 05/19/06 at 23:09:24
 
Knowing HOW or WHY would "help one master the outcome".

Remember, knowledge is power.   Grin

Bob
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« Last Edit: 05/19/06 at 23:09:48 by Bob »  
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Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #157 - 05/19/06 at 23:12:32
 
DAMMIT, just remembered, can't post at home.....  >:(

Talk to you all on Monday.

Bob
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J_Rock
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #158 - 05/19/06 at 23:16:45
 
Well alright then.  The way I understand it:

A Ported box is extremely alike to a sealed enclosure.  Only difference is there is a hole in a ported box that is deep enough to support a standing wave.  The frequency at which this wave will stand is based on the length and diameter of the port.  Above the frequency of this port, the box acts just like a sealed enclosure.  As you get closer and closer to the tuning frequency, the port begins to resonate.  The resonace results in a boost in output near the tuning frequency of the port.  

Below the tuning of the port, things go haywire.  They do this because below the frequency, the waves are too long to form a standing wave, and so they pass in and out of the port without any restriction.  Since the hole in the box no longer resists the air flow, the air cannot control the subs movement from the lack of pressure behind the cone.  So the sub becomes "unloaded" and is esentially acting as if it were in free air.  

At low power this has very little effect on the sub, but at higher power, the sub quickly begins to move back and forth farther than it is intended to do so.  Eventually leading to the sub reaching it's mechanical limit of excursion.  In other words, the voicecoil starts slamming into something.

Hows that?
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John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #159 - 05/19/06 at 23:29:11
 
Bob,

Something to keep in mind is that a little tweaking is very easy and realistically starting from scratch is going to require one of 2 things, 4 times the box size (which will at most get you 6db more than optimizing what you have) OR two smaller boxes plus as much power as your drivers can handle and Linkwitz transform circuitry (which probably won't net much SPL gain).  You could spend over $300/driver and get some extreme excursion drivers, but again your 2 will about equal one of those, so you'd need 2 of them to add another 6-8db to your existing potential.

Getting into the low teens just isn't easy without numerous high excursion drivers, not when you're asking for 100db+ down there.  That's why I haven't built a super sub yet even though I have lots of drivers.
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Adrian D.
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #160 - 05/20/06 at 17:37:05
 
i remember HBbass got pretty good results with the 10" version of the hwk, and steve's subs.
check the second page of the HWK support forum.
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Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #161 - 05/22/06 at 11:54:52
 
Well,.. had zero play time this weekend due to deck buliding, and the death of a good friends wife.  Too much death recently on this forum.

John, how about Dan Wiggins design you mentioned on page 3, reply #34. 110db @ 11hz to 40hz. I've got the amp, I think I've got the drivers (not sure if he's referring to DVC's or not?)

I've got the space,...I think for a 14cu'  box. That'd be less than 2'X2'X4' I believe. That seems small.

Now, I realize there's a gap from 40hz to my bottom of my current mains.
But I see an option...
"buck-up" and spend some money, Use Dan's plans for the content below 40hz, with new drivers, use HWK for the content from 40hz and up. Use existing 2 channel amp to feed both subs.
Would this be an acoustic mess? Crossover nightmare?

OR,... Build Dan's box, suffer with the hz gap until new main/surround can be built.

Whadya think big guy?

Bob
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John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #162 - 05/22/06 at 19:27:28
 
Bob,

Sorry to hear about the problems.  It really sucks when others die.  On the bright side, when it's our turn hopefully it won't.

Dan said "more than 110db in-room".  It's essentially what you have now (with the top cap on) output-wise, but with deeper extension.  It's also exactly what I was talking about with HWKenstein by just adding the extension to your existing cab as previously outlined.  If you make the extension removeable, then you can have your cake and eat it too.
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Bob
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #163 - 05/22/06 at 21:39:49
 
Ok, so I refered to post #66 on page 5. THAT is what I need to get lower hz, not nessesarily higher db.
Right?

I can accept the volume for the most part.  ???
But lower hz would be nice. I feel I'm not getting the most out of a movie if the soundtrack has material beyond what the equipment is capable of. The volume is the "cherry on top", as long as it has a decent punch. Your correct about teaching the youngsters bad audio habits. Not in the least, I'd hate to damage the frail little ears.
Bob
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« Last Edit: 05/22/06 at 22:16:32 by Bob »  
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John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #164 - 05/22/06 at 22:38:18
 
Bob,

That's the one and I think I had a post shortly after that talking about how to make it reversible.  Note that you will need to change the top port too to something close to Dan's recommendation.  The volume in that chamber net of the 3L for the driver and 4L or so for the port is a almost the size he recommended.

I think first though, try what you have with the top cap on.  Do your max test and SQ.  Experiment with lower tuning (longer ports) on each (4" in the case of the top one).  That higher tuning will get you higher max SPL than the big one and might just blend OK with your current speakers.  Even try a 10" longer bottom port for 15hz tuning, which may be low enough, although I think you'd be getting into high port noise territory with that long of a port.  

To check what 15hz tuning is like, you can also use your current bottom port length and mount the drivers in place of the top cap.  You wouldn't have the same excursion control (and max potential) that the 6th order BP (ported top and bottom) has, but it would definitely blend with your mains.  Easy conversion and easy change later to HWKenstein makes trying with the pretty box you already have make a lot of sense to me.  

If you want to go for the gusto, don't let me hold you back.  I've all but decided to give HWKenstein a go myself.  I just can't see building the 900L version of the Tower of Power that I've been discussing with Bassboy.  I might as well go sealed and use all my woofers if I'm going that big.  I change my mind on a daily basis.
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