CurtPalme.com Home Theater Forum

ecrabb · Posted: Thu Apr 30, 2009 4:29 pm Post subject:

greg_mitch · Joined: 03 May 2006 Posts: 5321

I say go for it if you are comfortable with your box making skills and design.

But even if you could sell your existing subs for $75 a piece and not sink money into the rest of the equipment it might make sense to just try out an A7S-450 and have it by this weekend (if they are in stock).

I am all for building but...I would go sonotube route to make it cheaper and quicker..but I suck at wood working due to major inexperience with it.

**AnalogRocks** · Posted: Thu Apr 30, 2009 9:46 pm Post subject:

The push pull one we did had one sealed chamber ( large ) and a smaller chamer (vented ) with two 10" drivers of the same manufacture ( MTX ) it was a space saving design.

futrhse · Posted: Fri May 01, 2009 5:02 am Post subject:

ALL JBL pro...

I just got through helping design, build and implement a rather large residential theater 40 X 37 X 11 it used 8 JBL pro 18" Subs in individual dual cabinets with 14, 15" JBL's on the fronts, sides and rears. Driven by 8 4000 watt Picker gradient amps and 8 channels of Sherborne side and rear amps. 200WPC X 8 Utilizing JBL CV horns and 2" large throat horns and drivers (7) This system will deliver the impact you want. FOR ANYTHING, All EQ'd up with 1/3 octave and parametric EQ's calibrated to + or - 1Db at the main listener position

This is a VISCERAL system full of life like impact! and where I'm going with all this is if you want subwoofers, the JBL pro stuff in the right size bass reflex box is UNBEATABLE. I.e; there is NO BETTER subwoofer than the JBL pro 15" and 18" pro-theater versions as has been touted by not only me but Stereophile, Home theater mag the Absolute Sound and AUDIO Mag when they were still being published. Place these woofers in custom cabinets using MARINE GRADE hi-density particle board DOUBLE thickness for less resonance and you will love their performance for the next 30 years. Yeah they're large and VERY heavy but they are astonishing. Think about it what do you think the THX movies are MASTERED ON? JBL pro. I built mine to Lucasfilms specs using the Theile-Small parameters in 1980 and they still outperform anything commercially made today and at very Hi SPL's as long as you use 200-500WPC amps that are clean.

Go to www.trueaudio.com and look up their WinSpeakerZ speaker builder package and you can build ANY Speaker cabinet for any driver using T-S parameters on this SW package and any order Xover or box. ALSO look at their realtime in a laptop analyzer. TRUE RTA.

Remember 1 thing most designers forget about... the length of you room will dictate the LF cutoff, NOT the speaker on a reasonably accurate box.

Realize to HEAR 20 Hz (CPS) the room must be 50' long for the wave-front to fully develop. Otherwise you're listening to an OVERTONE of 20 Hz usually the 5th or the 4th harmonic above the root freq.

Good Luck hope this helps.

G Bell

JBL 2248 18" SUBS 2, ALTEC 515B's 4-15" woofers , Altec 511B 24" horns and 1" 802 drivers
ESS HEIL full ribbon tweeters driven by PAOLI Tube amps.
6 Custom amps built on the National SEMI LME49810M op amp delivering 529WPC
(fronts are quad amped with RANE elect Xovers)
(6) Sides and rears Gold Sound 8" dual point source coaxial drivers in THX config
1 Lexicon DTS & Dolby DD processor, Toshiba HDDVD (2)
8 channels of ARP and SAE 3rd and 1/2 Octave EQ.
Asus HTPC with Crossfire, LG, Intel 965 Win DVD for Blu-Ray
JVC Pro D-ILA 4000 Projector
LEDE room for Live end/Dead End acoustic treatments 35' X 27' X 8'
True RTA 1/3, 1/6 Octave realtime with AKG calibration instrumentation mic's
Rockland FFT Specrum Analyzer with "waterfall" TDS.
IVIE IE-10 SPL meter

All 8 channels calibrated to + or - 1DB at the listeners viewing seat.

WTS · Joined: 08 Mar 2006 Posts: 1276 Location: Calgary

Have you had a look at the diyaudio.com forum yet? Great forum for speakers.

greg_mitch · Joined: 03 May 2006 Posts: 5321

eD has the A5-350's on sale now.

A pair for $1300! If you knock of shipping both of them to your door (108lbs shipping weight) by picking them up you should be out just a bit over $1,000 which is a bit more than $500 a piece.

That is crazy good price. Find a buddy to go halvsies with you and you are set if you don't want to spend much....heck...I am thinking about it.

ecrabb · Posted: Thu May 07, 2009 4:52 pm Post subject:

That's tempting, Greg... I just can't spend the money right now. If you said you were going to do it, and you needed me to go in on the deal, I might have to give it some serious thought. Wink

But, what I'm doing right now, and the point of this thread is just research. I just wanted to start getting some ideas because I got a serious case of sub envy at Cliff's place... Which is easy to do given the RIDICULOUS amount of LFE he has going in his room (not that there's anything wrong with that! Wink

). I have realistic expectations, though... He probably spent nearly triple on his big SVS' to what I'd spend... even if I bought two A5-350's for myself. I'm just thinkin' and schemin' right now. I'll probably do nothing and then just go nuts right before the fall HT meet. Wink

SC

Mark_A_W · Posted: Thu May 07, 2009 11:11 pm Post subject:

greg_mitch · Joined: 03 May 2006 Posts: 5321

futrhse · Posted: Fri May 08, 2009 2:23 am Post subject: Wavelength of sound in AIR...

Wavelength of Sound in AIR as a function of frequency, Temp 20 deg. C, @ 760mm pressure:

And....

"Remember 1 thing most designers forget about... the length of you room will dictate the LF cutoff, NOT the speaker on a reasonably accurate box. "

These statement is totally and utterly wrong. Completely backwards in fact. Think about it - take it to it's conclusion, say in a car. If this was true there would be NO bass in a car. In fact the opposite is true. Even my stock 6" car speakers have plenty of bass in a small environment. Then think about headphones...

Below the lowest standing wave you get MORE bass, as the pressure can effect takes over, and you get room gain.

futrhse, go and read the Adire white papers. If what you said was true, I would not be able to physically shake the roof (projector and all) at 14hz with my four 15" woofers, when if fact it does it so easily it's scary (I only did it once, for fun...literally sounds like a helicopter is landing on the roof).

WRONG!!! Don't give a CRAP about the Adire white papers, or what they say. Don't take my word for it...I take my information from the BIBLE of the audio industry.
"The AudioCyclopedia" by Howard Tremaine..."the most comprehensive and authoritative reference volume on AUDIO ever published."
Page 16 is the reference graphic for wavelength in air vs distance. The bottom line is...the human ear ain't gonna hear 20hz in any room less than 50' in length cause the wave doesn't develop. IF your woofer can reproduce it. If it can and the room isn't that long you won't hear 20 hz. PERIOD! What is heard is an overtone (harmonic) of the 20 hz fundamental. Using 30 hz, the wavelength distance is appx 35'. Car stereo doesn't develop the wavefront in appx 4'.
Stand back 20-30' behind the car, open the windows and you'll start to hear the REAL bottom end.

Check your facts Mark A W, but use a credible reference source. The AudioCyclopedia was WRITTEN by those who pioneered the Motion Picture industry along with MA BELL LABS where the history of recorded and reproduced sound, for all intents and purposes, began.

BTW I'll bet you 1M USD the resonance of your room is MUCH higher than 14 hz and the reason it shakes is because it was built NOT intended for sound reproduction as the major joist, stud, wall and flooring materials were not SCREWED or ringshanked and RIGIDLY glued together. I could walk into your room and EASILY shake it apart at practically any frequency between 80hz and 40 hz with a simple sine wave generator and a big power amp and an ALTEC, JBL or McCauley 15" woofer. What you're hearing is room resonance excited by many different frequencies.

The AudioCyclopedia...

http://www.amazon.com/Audio-Cyclopedia-Howard-M-Tremaine/dp/0672206757/ref=sr_1_1?ie=UTF8&s=books&qid=1241748736&sr=8-1

futrhse

Mark_A_W · Posted: Fri May 08, 2009 8:16 am Post subject:

Try it. One test is worth one thousand theories. Bible said the earth is flat and the sun goes around the earth.

My room is 5.5m long.

I have a strong, rising response to ~20hz. Below that it tapers to ~14hz.

At 25hz and below, you can't hear a thing, but the room shakes. It is a very odd and queasy feeling.

I have four 15" Tempests in an IB, driven by 600w (although 100w will drive them to their excursion limits, as it is an IB...at about 110dB).

Just try it.

According to your theory, based on biblical FACT, it should be impossible to have any bass below 65hz in my room. SIXTY FIVE HERTZ.

Tried it yet? Can you explain headphones to me??

You are parroting the biggest audio myth of them all.

Mark_A_W · Posted: Fri May 08, 2009 9:01 am Post subject:

Oh, and the bibles are:

"The Loudspeaker Design Cookbook" by Vance Dickason. (The recipes book is helpful too.)

"Testing Loudspeakers" by Joseph D'Appolito.

Tom.W · Joined: 09 Mar 2006 Posts: 6637

I have the first book. Very good !