Altec 3182's in a 4 meter transmission line

**joyspring** · August 14th, 2004, 05:35 PM

HiFiPlayer:

"Although he can follow principles to built his amazing system. But is there really such simple can reproduce ultra low frequency? Don?t forget that 8Hz is true infrasound!"

I fail to see what's so amazing about this; he sought to produce a system that no only can reproduce subsonics but also has excellent transient behaviour and group delay characteristics. He outlined a reasonable system specification and realised it via careful design.

None of the piecemeal `add a cable here' or `tweak a doo-dat there' that amateurs are constantly doing.

If you would step out of the 1950s/1960s low-Q/high-efficiency Vintage mindset for only a moment, you'll notice that there are *lots* of LF drivers that have extended Xmax (linear excursion) and optimised Thiele-Small parameters to achieve excellent sub-LF performance. Funny, now that engineers have the codified Thiele-Small methodology, they can now consistently, predictably and accurately produce drivers for a specific system performance spec. Note that they could not even come CLOSE to doing so prior to the 1970s.

Anyhow, excellent high-power amplifiers are now relatively inexpensive, so high-mass/low-efficiency drivers with massive EQ boost render subsonic performance relatively easy to achieve.

"Other hand, I doubt that speaker really able to load and against such low frequency such easy."

Read the article again; enclosure design, room loading, EQ and lots of power are employed to achieve his results.

Also, a working knowledge of Physics and Acoustics certainly helps.

"Then please let me know what amplifiers, CD player, DAC and also driver units etc that he has employing."

For the LF amp, this person is using a Tripath 5KW digital amplifier fed by a Behringer 24-bit/96kHz digital crossover. The LF drivers are Altec 3182, as noted in the original post above.

Since you're having trouble viewing the original page, here's his system description:

The system setup in the reception room of my new town house in Hampton wick, each of the major components is numbered, with a brief description in the accompanying box:1) Altec 3182 18" woofers, 2) 4meter tapered, concentric transmission line cabinets, 3) Speaker stands, 4) JBL 2123 102 drivers in .55 cu.ft. vented cabinets tuned to 85hz, 5) TAD 2002 compression drivers mounted on Oak Tractrix horn, 6) Tripath Amplifiers,5kW total 7) Balanced volume control, and Tripath treble amp 8) Behringer DCX2496 digital crossover, 9) Denon CD, 10) Linn LP12 turntable

<font size="2" face="Verdana, Helvetica, sans-serif">It's too bad that you're not able to view the page as it's not the equipment description but the acoustic measurements that are so interesting.

" Cause I also want to get one such High Fidelity audio products."

This person built the Tripath amps from evaluation boards and home-built power supplies, so that may be somewhat out-of-reach for most end-users.

The rest of the system is not quite so exotic. Heck, I use a US$150 DVD-A player at home with great results.

Digital amps and signal processing will becoming far more commonplace over the next decade, especially if audiophiles will finally get over all the ridiculous `tube retro vintage' rubbish.

Better performance for less money; that's why engineers exist and that's technological advance is all about.

"As Far as I know that once accident was happened. But I forget the details. You can see that just a story. A village peoples and animals were all dead within about circum 3 kilometers in an afternoon. Caused by a laboratory made a mistake to turn on the infrasound wave generator."

Cite the story, or at least provide some details (location for example) so others may research this. I don't believe it based on your description.

"Take a look at this site if you want to know how terror about ultra low frequency or infrasound wave weapon."

It's already known that sound in certain frequency ranges may be unpleasant; the article simply states that infrasonic sound may be unpleasant, particularly when it's relatively low-SPL and undetectable (remember the Fletcher-Munson curves?).

High-SPL sound has been extensively used as a weapon - concussion grenades are an example I can think of off the top of my head.

BobR

**jnorv** · August 14th, 2004, 08:01 PM

Nelson Pass tried a similar experiment.

http://www.passdiy.com/projects/el-pipe-o-1.htm

Jim Norvell

**HiFiPlayer** · August 14th, 2004, 08:22 PM

BobR

Does it easy to reproduce completely pipe organs, 747 and rocket launches?
Causes I?ve never been hear any system can really achieve. Even no one was brag in their product?s adverting in hi-fi magazines.

Other hand, mostly audio products also responsible frequency within 20Hz to 20kHz, so why his Denon CD, Linn turntable, Behringer Xover and Altec, JBL drivers can provide such fearfulness frequency response? (flat extend to 8Hz!)

BTW, 5kW total outputs are continuous or peaks? What class? I think he use that system for cooking dinners if those are pure class A. Then it can also disinfest and warming up his home in winter.

To imagine that you can sit on chair at home to enjoy completely pipe organs, 747 and rocket launches records.

He will get the Nobel prize!!!

HiFiPlayer forums

**joyspring** · August 14th, 2004, 10:28 PM

HiFiPlayer:

"Does it easy to reproduce completely pipe organs, 747 and rocket launches?"

No, it's not easy, particularly at high sound pressure levels; however, it now can be done with enough amplifier power and modern high-output, high Xmax LF drivers.

It could NOT be done 30 years ago -- LF transducer technology has rapidly developed since.

"Causes I?ve never been hear any system can really achieve. Even no one was brag in their product?s adverting in hi-fi magazines."

I've heard many Bag End ELF-based systems used for film mixing, and many mastering and even music mixing control rooms are being outfitted with subsonic-capable systems.

WHY????

Because digital recording does NOT have all the limitations of analogue LP or magnetic tape recording and CAN and DOES remain flat, with no distortion, mistracking, phase anomalies, etc. that phonographs and analogue tape are plagued with, far below 20hz.

I have a colleague who has outfitted his living room hi-fi system with a Bag End ELF subwoofer system; he initially left the ELF processor to integrate all the way down to 8Hz. A 10hz sinusoid consumed all available amplifier power (from Crest Audio 9001s, mind you) and did manage to knock things off shelves in adjacent rooms.

Several companies do offer subwoofer systems that are flat below 20Hz: Velodyne, HSU Research and Sunfire come to mind. And yes, they do advertise in hi-fi magazines.

"Other hand, mostly audio products also responsible frequency within 20Hz to 20kHz, so why his Denon CD, Linn turntable, Behringer Xover and Altec, JBL drivers can provide such fearfulness frequency response? (flat extend to 8Hz!)"

With the exception of the phonograph cartridge, everything else is digital, and if not high-passed, is fully capable of providing flat, distortion-free response below 20Hz.

"BTW, 5kW total outputs are continuous or peaks? What class? I think he use that system for cooking dinners if those are pure class A. Then it can also disinfest and warming up his home in winter. "

This person assembled several Class T (Tripath's Class T technology white paper is available here
into a Class AB topology. The general website for Tripath is:

http://www.tripath.com/
Tripath's Class T white paper

I rather doubt that it is continuous power since most residential circuits are 20 amps (in 110/120VAC countries). However, have a look at the 2.5KVA toroidal transformers and capacitor banks - I think he has enough reserve power for any transients ;-)

Nearly every semiconductor manufacturere and amplifier company is developing switched topology power amplifiers, and many are now outperforming traditional amplifier designs.

Class A? Completely ridiculous in power amplifiers; modern designs in the past twenty years have made crossover anomalies completely inaudible and utterly inconsequential.

FFT and other time-domain measurements of even inexpensive but modern integrated-circuit amplifiers bear this out.

Otherwise, Class A is a total waste, and most `boutique' designs have deficient power supplies and consequently have high THD.

Folks, please use have some perspective and some common sense!

Class A does have some application in line-level or millivolt-level circuits where the magnitude of crossover distortion is much higher in proportion to the overall signal but for power amplifiers, it is simply a waste of energy.

"To imagine that you can sit on chair at home to enjoy completely pipe organs, 747 and rocket launches records. "

Some people already do; that is, people that don't insist on and limit themselves to 10W SET/Class A amplifiers, phonograph records and low-Q/high-efficiency drivers that have negligible output below 25Hz.

BobR