60ndown's Merged Subwoofer Thread

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#84
doug20 said:
As a test...how about a sealed 25x15 room fully treated. What is the best design if 25Hz/120dB clean peaks are needed at 18ft??
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I'll play, I'm assuming for classical music.

(what i would do)... four 15" drivers each in separate box, say RSS390HF-4 in 9ft^3 boxes dual port tuned to 14hz with 500w each peaks at 34.64102v.

That should rattle your fillings.

oh yea... placement. 4 across the front . delay on mains 3ms
 
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#85
#90
Reminds me of some of my early designs.
They were mostly just banging a speaker into a wooden box.

First effort was a 4 by 12 inch cabinet which was fine until i tried to get it in the car, of course wouldnt fit. I ran a mobile disco so it was vital to fot in the car. So split into 2 off 2 by 12 inch cabinets which went in the car fine on their side. I used 4 Fane 50watt speakers and they were very loud, got told to turn it down a few times.
 
#92
KALLELUJAH !!!

60ndown said:
An externally hosted image should be here but it was not working when we last tested it.


it started here

http://www.diyaudio.com/forums/subwoofers/189823-projecting-bass-forward-not-omnidirectional.html

i used (4) 6.5" subwoofers from a thrift store purchase (2 pairs of nasty 3 way speakers that have the subwoofer section built into the speaker) $7.50 pair, so for $15 i got 4 *subwoofers* ??

the drivers are kinda lightweight compared t some of the subs ive used 😀


but the 4 of them in this box do sound surprizingly good ,

i dont do testing/measurements or spellcheck.

i trust my ears.


id say it gets down to about 35 hz with 'authority' and hints at lower.

havent pushed it too hard *yet* but it easily makes tv/movies exciting !

i have about 4 hours time and $15 in drivers and some scrap plywood into it.

im looking forward to having my EXCELLENT bass player friend come over and see what it really can do


😀

https://picasaweb.google.com/gregmuon/STUPIDHIFITRICKS#5597728348905766834
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Hi Dude

Personaly I would like to award you one of these !

1819medal.jpg

The worlds best & Koolest speaker cab. just got 4x better & FASTER too !

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


I love the battleship grey matt finish, my monitors have sported a nice Kodak grey card 18% density finish for 20 years... I'M LOVIN' IT !

As Thomas says the built in CD slot drive is the iceing on the cake !!!

Cheers

Simon
😎
​
 
#94
Quote:
Originally Posted by doug20
As a test...how about a sealed 25x15 room fully treated. What is the best design if 25Hz/120dB clean peaks are needed at 18ft??
I'll play, I'm assuming for classical music.

(what i would do)... four 15" drivers each in separate box, say RSS390HF-4 in 9ft^3 boxes dual port tuned to 14hz with 500w each peaks at 34.64102v.

That should rattle your fillings.

oh yea... placement. 4 across the front . delay on mains 3ms

I should note, assumptions : single listening position, room orientated depth 25"

If the listening position is wider than 3ft i would delay 1 , 4, 1.2ms. or do a vertical stack on center line.
 
#95
Why so many designs?

Because there are so many requirements--if I was a single guy, my subwoofer would be quite different! 😀 My wife would rather drag her face through half a mile of broken glass than read DIY audio--I'm safe!

My perfect sub would be a straight horn loaded quad 18" push-pull in a 106 foot long horn--doubles as a wind mill and lightning rod--make the mouth big enough and it can be the roof of the house.

Too much? Welcome to COMPROMISE! If I could get 130 dB of 10 Hz bass in a thimble--I would do it. As said earlier in this thread, why so many different cars? Build a 3 liter 4 cylinder diesel station wagon and take care of 99% of people's needs world-wide. Throw a 2" frame hitch on the back stock.

Then there is that other 1%... ahhhhh, yes! Some DIY'er would cut the frame, extend it to hold 9 people and stuff two diesels in the thing--others would use the engine as a generator and run electric hub motors...

Gotta hate that choice thing--such is freedom. If you want home theater--go to a theater. Want music? Headphones or concert stadiums... 😱
 
#99
60ndown said:
ive loved bass, sub-bass for 25 years, every week there is a new design !

is there a time tested and proven design that just works?

lots of great drivers/subwoofers available these days,

and great amps

and great x overs.

in my opinion, a 'good' subwoofer should reproduce the original tone, tones, dynamics, frequencies, transients as the original source

(stand up bass guitar, kick drum, 5 string bass, keyboard)

and only amplify those sounds.


*if* thats what a subwoofer is supposed to do, there must be many designs already available time tested by 1000s that work well.

what are they?

and why bother messing with box calc software, wood and glue if what we want already exists?


:djinn:
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"is there a time tested and proven design that just works?"

Yes, the acoustic suspension principle works best. When properly executed, it can have flat response to any arbitrary frequency from a small box, has inherently very low THD, and is equalizable to extend its range downward. These are the result of several inherent advantages.

First all woofers can be analyzed using Newtown's second law of motion applied to forced oscillation. This equation predicts FR and has proven very accurate over several hundred years. It takes into account three factors; moving mass, springiness of the suspension, and damping.

The first thing you notice is that because the acoustic suspension speaker relies on air pressure, the springiness (restoring force) is not a function of frequency. Every open box design depends to one degree or another on tuning. The springiness of air depends on frequency, low when it is near the tuned frequency and its multiples, high when it's around half an octave away. Also the linearity of air as a spring for most of the restoring force is much better than the mechanical suspensions of tighter speakers used in other designs. Damping is controlled by the amount of stuffing and the nature of the fibers (dimensions, geometry, packing density.) This creates an aerodynamic drag when the speaker tries to push or pull air through it. By manipulating the air volume inside the box and stuffing, the speaker can be tuned flat (critical damping is 0.707) to any frequency.

There are other advantages. Because the restoring force is applied evenly over the cone by air pressure, there are no radial or circumferential force gradients that tend to twist or tear the cone in shear reducing the tendency to break up into Bessel function modes causing harmoic distortion. The heavier cones required to have adequate mass are also inherently stronger.

Falloff below sysem resonance is only 12 db per octave so equalization can extend bass at least one octave. Ported designs fall off at 24 db per octave so the system resonance is effectively the LF cutoff of the system.

The price of this is efficiency. These are notoriously inefficient designs but in the days when 100 WPC is common that's not a problem unless you demand single ended Class A SET amps.
 
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