10-25 hz, is it necessary for HT or Music? - Page 3 - diyAudio
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Old 27th August 2007, 04:54 AM   #21
Petriej is offline Petriej  United States
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I was having some fun with WinISD and thought I'd share some of my calculations.

Dayton's RSS390HF-4 in an isobarik configuration in a ported box around 6 cu ft. It's not a horn...but the graphs look good. One day I'll make this. I'll see if I can find the files. If you want, I'll email them to you.
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Old 27th August 2007, 06:36 AM   #22
Daveis is offline Daveis  United States
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Quote:
Originally posted by Petriej
I was having some fun with WinISD and thought I'd share some of my calculations.

Dayton's RSS390HF-4 in an isobarik configuration in a ported box around 6 cu ft. It's not a horn...but the graphs look good. One day I'll make this. I'll see if I can find the files. If you want, I'll email them to you.
That sounds interesting. I have two of those drivers now in 3 cu foot sealed Parts Express boxes.
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Old 1st September 2007, 08:15 PM   #23
nik1818 is offline nik1818  United States
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i feel bad for missing this thread for so long. the solution is right in your backyard, davies. about 30 miles east of des moines is a town called Newton, IA, and there is a company called Elemental Designs. They do mostly car audio, but have bridged the gap to home theatre. at this very second, ive got music cranked on my home theatre featuring subs i got from them. And i've checked, i get considerable output from 8 Hz, all the way to ridiculous output as high as 80 Hz. They've got a nice office, great customer support, and if you give them a call, they'll let you come in an check out their theatre room. i was out there a couple months ago, and they had their dual 18" home theatre offering for anyone to listen to. You can pick up the 18" for $195 with a 5 year warantee. I got 4, and only use two until i can find another amp. But check them out, im sure you and your friend wont be disappointed.

www.edesignaudio.com
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Old 1st September 2007, 08:54 PM   #24
Daveis is offline Daveis  United States
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nik1818, great information. yes, having a place to build boxes less than 40 minutes away is a good thing.

Some continued thoughts I've had...

Zaph says that low Xmax drivers sound better. He uses a Dayton woofer and sub woofer as an example. The sub woofer has a flatter response as it trails off towards 20hz.

Doubling woofers, even big high excursion woofers like TC Sounds reduces distortion.

Putting those two together... would I be better off with one TC Sounds TC-2000 type driver. Or two 26W/8861T 10" Revelator Woofers?

The Scanspeaks Fs=19 whereas the TC Sounds Fs=23.

Scanspeaks are a bit more money, but TC's prices are going up soon.
(And that's if DIY'ers are still able to get ahold of them)

Is there a driver that can do 20hz without using porting? Can any driver do this? It seems to get below 30hz you have to resort to porting.

And one more thought... can you hear/feel 8-20hz at less than 120db's output anyways? Are the guys that claim they can hear/feel this just dreaming.

Which brings up another point... let's say you boosted your output down below 25 hz so you could feel the movie explosions. What kind of plate amp would you use and what power rating do you need?
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Old 1st September 2007, 11:09 PM   #25
ScottG is offline ScottG  United States
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It seems most are arguing against ultra low freq. sound reproduction..

I'll suggest otherwise.

Music Reproduction:

While fundamentals in music rarely go below 40 Hz, there are harmonics on either side of the fundamental (and harmonics of the harmonics, etc..). And thats just direct sound..

Then there is indirect sound.

Most recordings have some form of low freq. "hall" sound, or reverberant room character (real or processed) - there are exceptions of course, but they are *exceptions*. Essentially lower freq.s "build" near boundaries - i.e. floors, walls, and ceilings. Each boundary represents a +3db gain nominally. This means that the acoustic space the recording is "in", (again real or processed), is highlighted by low freq.s that are "lifted" in level relative to direct sound.

If this indirect sound is reproduced well in a proper location then it tends to dramatically expand the "soundstage". Not only contributing to audible enjoyment and realism, but it is also less fatiguing to "locate" images of direct sound with this audible spatial "marker". This is despite picking up recording flaws, which can occur.

Unfortunately there are some obstacles to overcome.

1. The indirect sound is often considerably lower in spl than the average, despite having a "highlighted" signature.

2. The listening room.. even a well acoustically isolated room, typically has an ambient noise level over 15 db's (+++). This "masks" audibility of these lower freq.s.

3. Further "masking" occurs naturally to our ears at low freq.s, though more so for direct sound than indirect sound (see Fletcher Munson "curves"). So in effect you have a loudness threshold to "pass" - but again, it isn't nearly what F&M would suggest.

4. Indirect sound (at least from my observations) seems to be even more critical of driver distortion (linear and non-linear) than direct sound. (In effect indirect sound is distortion.. and distortion on distortion just seems to increase the overall noise level similar to room masking - making it more difficult to hear all recorded detail. Where as distortion of fundamentals if kept moderately low - only seem to "color" the fundamental rather than "bleach" it out.)

Home Theater reproduction:

Better recorded and transfered movies also have hall sound in varying degrees.

Movies produced from the mid-eighties (and more so today), also have occasional low freq. effects that are fundamentals (..sometimes below 12 Hz). However these fundamentals often have fast "dropping" harmonics (and today are typically synthetic) - so harmonic reproduction of direct sound isn't real important at these low freq.s.

While you will always want to reproduce the fundamental in a movie (and are less concerned with direct harmonics), you might not want excellent (or even good) reproduction of hall sound detail. The problem here is that you can sometimes hear several different acoustic spaces effectively superimposed on each other - and this distracts from the virtual reality of the movie the director was trying to give you.
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Old 1st September 2007, 11:31 PM   #26
Daveis is offline Daveis  United States
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Another thought...

Almost everyone I know with a separate sub puts it in the corner of the room. They feel they are getting a wall loading boost from doing that. Typically, these same folks are crossing over at 70-80hz.

Now I like good bass guitar playing. And the bass has a lowest frequency at something like 41hz.

So... if you want your bass guitar to sound tight, wouldn't you try to cross over to the sub at 40hz. This is assuming your main speakers are good to 40.

Now, it seems to me that you'd want to be able to switch the sub out when listening to music that doesnt require it... and switch it in for movies and the few musical pieces that need it.

You could cross over at 40hz... but then your sub sitting far off in the corner would be interfering with your enjoyment of your main speakers bottom octave. I'm assuming your using a steep crossover like 24/48db octave.

So, is there a crossover at 40hz that is infinitely steep so that your big/monster sub doesn't "contaminate" your main speakers above 40hz? Is this a Bessel filter? Or Cauer Elliptical?

Is there software that can help simulate woofer box placement? I think I remember there being something out there for that.
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Old 1st September 2007, 11:39 PM   #27
Daveis is offline Daveis  United States
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Default Box construction

Box shape has been studied as it effects speakers.

Has anyone studied the effect of different shapes of internal shelf bracing?


So, let's say you build the sub to end all subs... what is the point of diminishing returns for wall thickness?

If the walls of your speaker were infinitely rigid, would that be a good thing? Don't you want your box to be a compromise between rigid and lossy?

I'm thinking you want the back wave to decay and the only way for that to happen is if your speakers walls absorb some of the energy.

So maybe the internal braces should be somewhat flexible? Like maybe 1/2" MDF instead of 3/4"... That way the internal braces flex a little and absorb some of the sound.

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Old 1st September 2007, 11:49 PM   #28
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For MUSIC, my first concern was setting the sub so that it did not over boost. After months of tinkering, my subs sound great but, they hardly ever fire up. Too much sub makes a muddy sound.

Also: I think most Sub Amps cut off at 30 Hz by default. Otherwise, you'd have a hard time playing vinyl.

I guess for HT, alls fair since you are looking for sensationalism rather than accuracy.
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Old 2nd September 2007, 08:13 PM   #29
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Quote:
Originally posted by Daveis
Adire Audio is gone. TC Sounds is no longer going to sell to DIY from what it sounds like.
Fortunately everytime someone closes up shop or abandons diy, someone else steps in... CSS SDS12 & SDX15 for instance and i hear John at Stryke/Acoustic Elegance is back so we have what can be considered the decendants of both Adire & Llambda....

Scott & i are working on a couple push-push SDX15 TLs that should easily extend below 15 Hz. Not really small thou (the small one is ~33 ft^3 and of course you should use a stereo pair )

dave
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Old 6th September 2007, 09:16 AM   #30
mikee55 is offline mikee55  United Kingdom
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Default Not enuff

My opinion is, there is not enough low stuff, more is needed.

I feel that todays equipment is more than capable of recording and re-producing it. How often do you listen to a track and all of a sudden, your sub behaves like it should rather than just underpinning your main speakers. It pops up and says ,"I'm Here", and you think, wow-give me more of that.

Cheers

Mike
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