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#240486 - 08/21/08 02:42 PM DIY Speakers for Sound Reinforcement
jetgraphics Offline
Junior Member

Registered: 09/02/02
Posts: 17
Loc: Temple, GA USA
[Cognitive Dissonance Flag On] http://www.billfitzmaurice.com/

I've been researching folded horn cabinets, and came across this site.
It appears to have some unique design characteristics, especially in the complexity of the horns. In essence, they're incredibly efficient, and according to owner/builders, great sounding.

One of the startling models rely on 8" and 10" woofers, to drive a super loud boxes that compare with 15" and 18" monsters that require 8 times the power to reach the same SPL.

Check out these models: DR200, Titan 39, and the Wedgehorn. They look like great prospects for a live venue.

Photos of live rigs: http://billfitzmaurice.com/phpBB2/viewtopic.php?t=4353

Titan 39 construction photos: http://www.lonesaguaro.com/speakers/BFD/Titan39/index.htm

I was surprised by the technical know how of the speaker designer. HE knows acoustics - fir shir.

What was shocking to this fan of the Acoustic Control 370 bass amp, was his refusal to make 18" folded horns. His answer is a picture at: http://billfitzmaurice.com/phpBB2/viewtopic.php?t=1130
The big cones can't handle the stress of a folded horn!
Go figure...

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#240487 - 08/21/08 09:56 PM Re: DIY Speakers for Sound Reinforcement
Dnj Offline
Senior Member

Registered: 09/21/00
Posts: 39551
Loc: NJ
Boy I'd hate to be sitting at that first table

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#240488 - 08/22/08 04:18 AM Re: DIY Speakers for Sound Reinforcement
cgiles Offline
Senior Member

Registered: 09/29/05
Posts: 5645
Loc: Roswell,GA/USA
Fascinating. I moved on to browse their forum. Gives you a good insight into the life of a Rock musician. I can't imagine playing constantly at those sound levels. Oh well, at least I can still hear (unless my wife is talking ).

chas
_________________________
"Faith means not wanting to know what is true." [Nietzsche]

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#240489 - 08/23/08 08:13 AM Re: DIY Speakers for Sound Reinforcement
jetgraphics Offline
Junior Member

Registered: 09/02/02
Posts: 17
Loc: Temple, GA USA
Tsk, tsk...
You've been misled by experiences with nasty commercial sound systems, and their inefficient distorted sound.

Just check out this post about an A/B test of cabinets: http://billfitzmaurice.com/phpBB2/viewtopic.php?f=13&t=4304&start=90&st=0&sk=t&sd=a

"I took them [DR200] to a Christmas party that is attended by about 60-70 people, 15-20 of which are musicians. One guy in particular, the keyboardist from my old 8-piece blues band, commented on how natural they sound. he said: It's just like listening to someone sing unamplified, only louder.

We also ran an acoustic through them that night (for those that have asked) and it was STELLAR! Very exciting to hear that."

What's "in" these cabinets?
Complex split folded horns that couple the speaker driver to move air (generate LOUD soundwaves) with minimal power input.
The DR200 + Titan 39 (full range) has a 10" driver for the subwoofer (!), 8" driver for the midrange, and a cross fired transmission line array made from inexpensive piezo tweeters. Based on user reports, they sound louder / better than a typical power sucking 18" subwoofer, 15" driver, compression horn system costing 10 times as much and needing 4 times the power.

Why aren't they made by commercial companies?
The woodwork is so labor intensive (DIY), that it's cheaper to build plain cubes that need kilowatts to drive them.

SPL chart: http://billfitzmaurice.com/phpBB2/viewtopic.php?f=12&t=1669

A DR200 measured at 1000 Hz, 103 dB/watt @ 1 M (input 2.83 V)
With 100 W amp, that adds 10 dB, resulting in 113 dB SPL. (A riveter generates 120 dB)

To put that into perspective, see chart: http://home.new.rr.com/trumpetb/audio/dBexamp.html

The right column lists "Professional sound reinf. equip, typ. all horn; 102 dB/watt "

Now, here's the "gotcha"... the 1000 Hz measurement is the LOW POINT.
The DR200 has 108 dB/Watt SPL at 150 Hz.

3 dB is a DOUBLING of sound pressure level.
So the DR200 has almost FOUR times the output as a "professional sound reinforcement" box for the same input.

The secret is the folded horn. Just as a trumpet makes "one lung power" into loud music, the folded horn makes modest speaker drivers into prodigious air movers.

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#240490 - 08/23/08 08:22 AM Re: DIY Speakers for Sound Reinforcement
Dnj Offline
Senior Member

Registered: 09/21/00
Posts: 39551
Loc: NJ
jetgraphics thanx for the info....very interesting....


BTW what do you think of the BOSE PAS L1 system?
http://www.bose.com/controller?event=VIEW_STATIC_PAGE_EVENT&url=/musicians/index.jsp

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#240491 - 08/23/08 03:04 PM Re: DIY Speakers for Sound Reinforcement
jetgraphics Offline
Junior Member

Registered: 09/02/02
Posts: 17
Loc: Temple, GA USA
Quote:
Originally posted by Dnj:
BTW what do you think of the BOSE PAS L1 system?
http://www.bose.com/controller?event=VIEW_STATIC_PAGE_EVENT&url=/musicians/index.jsp



Found on one site:
"Leave the psychoacoustics to Dr Armar Bose. He's been fooling the public for many years and I'd hate to take that crown away from him!"
http://www.bose.com/controller?event=VIEW_STATIC_PAGE_EVENT&url=/musicians/faqs.jsp&ck=0
27. Why doesn't Bose publish full system specifications for L1 systems?

A. While some specifications add value when comparing two otherwise similar products, they're mostly meaningless for a product as fundamentally different as the Cylindrical Radiator® loudspeaker and the L1 system. In addition, most specifications used to describe sound systems can be very misleading. They suggest relatively complex physical or perceptual properties can be condensed to a single or small set of numbers that defines overall quality or performance. In many cases these numbers only loosely relate to what you would experience in a real-world application.

There are also several variations in how a specific measurement can be carried out, making number comparisons useless. We believe it serves our customers better to describe L1 systems in terms they can relate to more directly. We also encourage customers to experience an L1 system personally, either at a demonstration or in actual real-world trials they conduct themselves.


YEAH, RIGHT...
DO NOT LOOK BEHIND THE CURTAIN!
WE ARE THE GREAT AND POWERFUL BOSE...

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#240492 - 08/23/08 03:33 PM Re: DIY Speakers for Sound Reinforcement
jetgraphics Offline
Junior Member

Registered: 09/02/02
Posts: 17
Loc: Temple, GA USA
My apologies for snarking at Bose.

In my own experience (subjective), I do not find Bose worthy of praise.

However, 'loudness' is subjective and not measurable.

Sound pressure level (SPL) is an objective measure and useful for comparison.

To some people, Bose may sound wonderful. Especially when a salesman is subtly suggesting 'how good they sound'.

In a live sound reinforcement situation, the name of the game is sensitivity - the relationship between power in and audio out.

For folks who have to live with standard 120 VAC / 15 Amp circuits, it's nice to have a sound system that sips 'the juice' while pumping the air.

Frankly, I've had to adjust my thinking on a lot of audio tech, after reading about BFD speakers.

For example, the "sage wisdom" of pro sound suggests that a subwoofer will need 3 times the power as does the midrange, and the horn will take about 1/3 as much as the midrange.
So you might have to provide 300W/100W/30W power spread to each unit of a tri-amped system.

BFM speakers, especially the subwoofers, are so sensitive, that you don't need 3x the power for the subs. And since he uses Piezos for tweeters, you don't need a crossover, and thus save on another amp.

Thus (4) DR200 and (4)Titan 39 speaker set up may only require a stereo amp 2 x 200W for a balanced full range sound (40 Hz to 20 kHz).

Measured at 100 Hz (crossover point)
4 x DR200 = 115 dB SPL at 1 meter (2.83 v)
4 x T39 = 115 dB SPL at 1 meter (2.83 v)

(Interesting point - BF suggests that you never increase power to get louder. Add more cabinets first. Apparently folded horn speakers do not distort as readily, so users have been known to blow their speakers from overdriving them to destruction. There's no benefit from high power voice coils speakers, either. Apparently power compression occurs at such power levels and output does not increase.)

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#240493 - 08/23/08 04:16 PM Re: DIY Speakers for Sound Reinforcement
jetgraphics Offline
Junior Member

Registered: 09/02/02
Posts: 17
Loc: Temple, GA USA
Link to an owner / builder in Israel, who built some wicked BIG flying rigs: http://srforums.prosoundweb.com/index.php/mv/msg/19198/0/0/0/
http://billfitzmaurice.com/phpBB2/viewtopic.php?f=13&t=5749&hilit=dr290

Link to a Vet Fest, featuring DR200's and Titan 39's. http://billfitzmaurice.com/phpBB2/viewtopic.php?f=13&t=6353&p=59311&hilit=dr200+build+photo#p59311

Link to DR200 build photos: http://www.finnbass.com/showthread.php?t=2210&highlight=dr200
(You can see the 'guts' of the split folded horn...oh my!)

Link to another DR200 build: http://www.frappr.com/?a=viewphoto&id=2160552&pid=3278433
(The DR series are the most complex / high performance BFD cabinets. The smallest, the 200, uses an 8" driver. DR250 uses a 10" driver. Can you guess which driver is in the DR300?)
hint, hint
200mm, 250mm, 300mm

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#240494 - 08/23/08 09:28 PM Re: DIY Speakers for Sound Reinforcement
Dnj Offline
Senior Member

Registered: 09/21/00
Posts: 39551
Loc: NJ
Jetgraphics...

Thank you for the very honest & informative answer. Very interesting observations.

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