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hz numbers on a 15" 2 driver (Read 43811 times)
John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #240 - 06/09/06 at 19:40:01
 
[quote author=Bob in St. Louis  link=1145573673/240#240 date=1149873260]Are you looking for the volume behind drywall including the 4" insulation, or volume between back of insulation to the concrete? [/quote]

If it's less than 100cuft don't worry about it.  If it's more, then approximate total volume behind the drywall.

Quote:
Horrible PITA to move cabinets. Don't know if it's possible with the way the screen attaches to the wall. (wouldn't have a wall to fasten to anymore if it's moved out).


I was hoping just a handful of screws holding the whole unit to the wall.  Move the light fixture on the right.  Move the cabinet unit out 18-24", and build a new wall with the airspace behind to house 1 or 2 IB manifolds.  Then just replace one of the panels with a grill to vent it into the listening area.  You sub would be out front where it belongs.  Extreme extension and output is easy.  No worries about integration with mains up to 80 or 100hz.  Your projector can move back and you get a bigger image ratio, and no big ugly sub to hide.
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Bob in St. Louis
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #241 - 06/09/06 at 21:12:34
 
[quote author=John in CR  link=1145573673/240#241 date=1149878401]If it's less than 100cuft don't worry about it.  If it's more, then approximate total volume behind the drywall. [/quote]

Without being at home, and the ability to measure the wall, I'm at a handicap. Hears a close guess. Under the 'cove' the wall is about 7' tall, we'll call the drywall .75 feet from concrete, and wall is about 20 feet long. I'd call that 105cu' which sound close enough to need an accurate measurement. I'm assuming an IB needs essentially no 'sealing' in the cavity the magnet is in.? The cavity between drywall and concrete is 'open' to all sides but the floor. It's as sealed as a 2X4 could be when next to concrete.

I really like the idea of an IB in the screen wall ( Yea, I've seen "The cult of the Infinitely Baffled". Cool stuff! )

When I started this project, I had never heard of IB.  ::)

Man that would be a huge undertaking, dealing with moving the screen and cabinets.

        l
        l
COVE \/    X         X         X joists X        X         X
------------+-------------------------------------
               l l                   ceiling tiles /\
               l l                                   l  
__________l l
                 l  <----- screen
                 l
                 l
                 l                      seating ------->
"open area"   l
                 l
-------------l
                 i
                 i
                 i
 cabinets     i
                 i
                 i
                 i
                 i                                 floor
------------------------------------------------------

Ok, the 'cove' is very permanent. Never to move. The "+" sign is the hinge for the screen (actually on the facing wall of the cove) If I pull the screen out, even a fraction of an inch, I'd have to 'reinvent the wheel' attaching it to something. Dealing with the tiles, and joists above to hang it from the ceiling instead of a wall is a bigger PITA than I think I want to get into.

Now the back wall,... I'm wide open.  ;D

Bob
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Bob in St. Louis
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Re: hz numbers on a 15" 2 driver
Reply #242 - 06/09/06 at 22:59:57
 
You got me thinking John.   Smiley

Talk to you Monday. (here in the 'upper 50') Don't know what time it is there.  :P

Bob
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John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #243 - 06/09/06 at 23:26:03
 
IB just means the front radiation is kept separate from the rear radiation and the rear air space needs to be of sufficient volume that the driver cone operates like it is in free air.  The typical recommendation is 8 times Vas, but you can get away with less.  eg For the IB15 driver Dayton recommends at least 15cuft of box volume for each driver (less than 1.5xVas).  How well the airspace enclosed by the rear wall can be used for IB will depend upon how freely the air can flow in that enclosed area.  The drivers you have aren't suited for IB use anyway, just trying to help develop a good plan when you are ready to upgrade.
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Bob in St. Louis
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #244 - 06/12/06 at 17:19:27
 
John, I think two things have helped my rig.
#1 Your advise on the sub. The tweeks have helped. I've played with some of those car audio bass cd's (you know, the woofer torture discs). This sub could be used for a room fan. The air coming from the lower port is amazing (scary actually). WITH NO KLOPPING.  :D

#2 My maturity level. I've turned down the overall receiver/surround volume, and turned the sub amp up, quite a bit actually. I suppose I was so interested in the HT "escape" that I thought the entire experience had to be loud. Like a good song you crank up. (However, a 2 hour long cranked up movie leads to fatigue.) But was still looking for the 'punch' from the sub. Well, at that volume, the sub was already at 90%. Not much headroom left. So, turned the receiver down, sub amp up. Gives it the nice little suprise when the movie requires it. Didn't really change placement so to speak, but twisting it on it's axis so the waves have to take a different path has helped somewhat.

I guess I'm an official member now of the housewrecker club. One of my favorite cocktail 'hurricane' glasses I got from Bubba Gump's Shrimp Company in Chicago broke.  ::) I truly had mixed emotions about that one. Pissed that I broke it, but had an uncontrolable grin as I walked past my wife to get the vacuum cleaner...... Thinking to myself as I cleaned the broken glass, "Yea, I got me a badassed sub, I can break shit now."

I'm beginning to realize some of my unhappiness with the system is due to me. I've always had a problem with wanting to make something that works perfectly fine, better. We all know my setup would not be considered audiophile grade. I hear you guys talk about your systems knowing mines nowhere close. Man, I can't imagine how some of your systems sound (charlieboy's, Mr. C's ect..ect..). Granted they're listening rooms, not HT, but there is no law that says you can't have both. I guess knowing that there is something out there that's sooo much better acoustically than what I'm hearing from mine is what my biggest problem is. I'll never be happy.  :(
I'm not at all embarrassed about my system, I'd show it proud to any of you guys. Knowing all the while your probably thinking, "this sounds like hell. I can't wait to get back to MY room". But proud none the less.
I could stop on the room right now, never tweek another thing and be pretty happy with it. I'd continue to have friends/relatives over and show it off. BUT, I know myself, and will continue to tweek/complain/modify/spend money/bitch untill I'm blue in the face.

So John, as far as your comment about being ready to upgrade,.... I'm always ready (just not ready to move walls yet  ;)) ... you just keep those radical ideas coming. I'll build 'em...
Can't wait for you and bassboy to design that W.M.D. your planning.   Smiley  I'd build it, as long as the drivers is'nt super high dollar.

Bob

EDIT- just proofread after posting, apparently the website censored me when I wrote "c0cktail", it replaced it with thingytail!? ... WTF? a totally innocent word censored by a website.  >:( (had to use a zero instead of an 'o' to get it to work that time.) Apparently "it" doesn't have a problem with me using other 4 letter words though.  ::)
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« Last Edit: 06/12/06 at 17:31:03 by Bob »  
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Bob in St. Louis
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #245 - 06/12/06 at 19:46:54
 
In an effort to further educate myself (surfing the net) I ran across this...

Specifically look for the clock, and the jar of rocks.

http://www.machinadynamica.com/

I wasn't feeling bold enough to start it's own thread.

Bob
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jj420
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #246 - 06/12/06 at 20:28:44
 
for such a "popular" product, that clock has very little to back it up.... there's not even a white paper on it, I am not certain a passive device such as this could actually improve the sound in a room.  I would have a much easier time believing it if there was more to digest on the site than some reviews of questionable objectivity, along with the alway suspect comments from "customers"

The pebbles on the other hand, I can see those working, I always weigh my speakers down with something, helps the definition a little.  At the ame time, a sort of " phase plug" in corner helps to break up refractions in these problem areas.

Magic rings, stage expanders, isolation platforms, this may show my ignorance, but the site is either a snake-oil cart, or a shop out of AD&D...

and all of it at bargain basement prices!!!! I cant wait to give them my account number HAH

almost always skeptical
JJ
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Bob in St. Louis
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #247 - 06/12/06 at 20:58:29
 
I understand the principle of weight on a speaker enclosure, but the ounce and a half the glass jar of rocks provide wouldn't do didley squat. (except rattle and buzz).

Bob
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John in CR
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #248 - 06/12/06 at 21:12:52
 
Bob,

I thought you were in St Louis.  I ran accross a Missouri audiophile group on Audio Circle and it was filled with nothing but "believers".  Since when did Missouri go through the gross transformation away from being The Show Me State.  If it sounds too good to be true, guess what, it is too good to be true.  

You want a jar of colorful rocks, fine buy a jar of colorful rocks.  You want to buy a digital travel alarm clock, buy one.  You want to separate you rig from vibration with weight and springs, fine, learn the math and do it right with the appropriate mass and springs, just don't go out and pay $25/ea for 25cent springs.  In any other business, vendors like that end up in jail for fraud, yet audio welcomes them with open arms.
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Bob in St. Louis
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #249 - 06/12/06 at 21:44:42
 
John, I've read some of your conversations with my geographic brethren. Funny stuff. (Although not funny for those involved)   Tongue

Yea, Missouri IS the 'show me state", but I didn't need anyone to 'show me' those things.  ::)

I've been trusting (nieve) before, but that's just stupid. Anybody that buys that... well, you know.

Hey John, do you have any pics of your setup?

Bob
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Bob in St. Louis
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #250 - 06/13/06 at 18:14:03
 
Ok, I want to put a Deathbox INSIDE of a Housewrecker, then put the Housewrecker INSIDE an Imperial, Then put the Imperial in the back of my truck. What would that sound like? Should I install a camper shell on my truck for more gain?

Bob  :-/

By the way, I took pics of the face of my Niles, then disassembled the cabinets and photo'd the inside. Have to develop the film to post.  ::)
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« Last Edit: 06/13/06 at 18:17:22 by Bob »  
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jj420
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #251 - 06/13/06 at 19:33:13
 
[quote author=Bob in St. Louis link=board=Housewrecker;num=1145573673;start=240#251 date=06/13/06 at 12:14:03]Ok, I want to put a Deathbox INSIDE of a Housewrecker, then put the Housewrecker INSIDE an Imperial, Then put the Imperial in the back of my truck. What would that sound like? Should I install a camper shell on my truck for more gain?
[quote]

outrageous man...

lets see, theoretically the two tunings would average the output from the db, yeilding two 'smaller than a normal HWK' spikes, which would in turn be amplified by the imperials horn...

so the system would have a fairly restricted output (low efficiency), likely resembling the comb effect of voight pipes, except distributed across the imperials response curve instead of a flat line.  Likely this would sound like @$$-mike + a long stairway, but with excellent power handling...

I think you were kidding though...  but the camper shell would help the gain a bit, by lowering it, that would be your only hope of achieving decent loadiung of the horn

I still think you are kidding, but a useless post is never truly appreciated until it is justified by an equally useless response.

JJ
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Bob in St. Louis
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #252 - 06/13/06 at 20:41:22
 
[quote author=jj420  link=1145573673/240#252 date=1150223593] I still think you are kidding, but a useless post is never truly appreciated until it is justified by an equally useless response.
JJ [/quote]

Yea, I was joking. I was amazed at the amount of threads dedicated to fitting a home sub into a vehicle. Had to add my own flavor. Didn't want to trash someone else's thread, sooooo,... naturally had to trash my own.  :)

Thanks for the quick response though. Shame our last two post were useless (you were correct JJ)

So, are you board at work too?

Bob
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Bob in St. Louis
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #253 - 06/19/06 at 19:14:12
 
Ok. B.S. aside. I've got pics and numbers. (Pics of surround drivers to be posted on webshots later today. Hopefully)

John, I played with some toys over the weekend. I have db numbers from 1 meter away from the bass of the sub at a hz range from 90hz, down to 10hz. ( yea, 10hz   Grin ) in 5hz increments. The first column is db's, second and third columns are hz's with the top cap on, then removed, respectively.
     cap    cap
     on      off

DB - HZ  -  HZ
90 - 110 - 110
85 - 112 - 110
80 - 115 - 111
75 - 117 - 112
70 - 119 - 112
65 - 119 - 112
60 - 117 - 112
55 - 113 - 109
50 - 109 - 106
45 - 109 - 107
40 - 109 - 107
35 - 109 - 108
30 - 109 - 108
25 - 108 - 107
20 - 105 - 104
15 -  94  - 97
10 -  88  - 96

With cap on (middle column)--Imagine a graph, (from right to left) you could see a small climb, to a peak of 119 between 65-70hz, with a gradual slope back down below about 20 hz where the slope falls sharply. (need to find my graph paper, just to see the pretty picture).
Interesting thing happens there in the teens with the cap off. The damn thing falls off in the same place, but is doing pretty well in the 'bottom of the well' so to speak.
Back on post #193, I said "18hz@130db may not be obtainable on a budget, but I 'might' be happy with 18hz @105db."   Well, the proofs "in the puddin'" as they say. John, thanks to you, I've got 20hz@105db. May play around with increments in 1hz from 15 to 20hz to see if we're there, but that's pretty damn close if nothing else.

BTW,  2 year old daughter can maintain 101db's when she's pissed, with an occasional peak to 108db. HZ is unknown, but painful.

Sound quality is perfect for movies (my goal) the torture tracks/chapters faired very well. The amp knob is now actually at about 1 o'clock (60%) during these tests. If memory serves, I believe I posted earlier that the knob was around 40%, and drivers were bottoming before the mods were performed.
Sound quality for music is ok, (granted the knob is at around 10 o'clock for music) but havn't sat down to actually LISTEN to some tunes without the family around. But what listening I've been able to do, does sound favorable.

John, would your Flinstones, or a OB in general "fit my bill"?

Bob
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bassboy
Ex Member



Re: hz numbers on a 15" 2 driver
Reply #254 - 06/19/06 at 20:39:39
 
Bob has a real home theatre subwoofer!  Good job Bob.

I'd keep the cap off as response looks much flatter that way.
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« Last Edit: 06/19/06 at 20:41:27 by bassboy »  
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