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Old 15th October 2016, 05:21 PM   #21
tb46 is offline tb46  United States
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Hi Entropy455,

There a quite a few others who have gone to extremes in the name of bass reproduction: here is one more:

REALHORNS - Ultimative High-End Surround Hornlautsprecher

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Old 15th October 2016, 05:31 PM   #22
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Originally Posted by Entropy455 View Post
In an equivalent spring-mass system, the horn’s throat impedance is simply a damper – in which case you need raw & blunt applied-force to overcome the damper (i.e. a high BL). You specifically do not need extra mass (MMS), nor do you need additional spring-K (high Vas), to overcome the damper. The ideal horn driver has a low Qts, mainly due to the high BL, and low MMS. Or am I completely out-to-lunch on my understanding of horn driver selection???
Entropy455,

Your understanding of horn driver selection is theoretically correct, but the theory was from an era when a 50 watt amplifier would have been considered quite high powered. The state of the art has evolved, drivers handling two or more orders of magnitude (5000+ peak watts) more power are now commonly available, and in terms of $$ adjusted for inflation, actually cost less than the 50 watt "high power" drivers that were common when horns ruled the playback and PA world.
To withstand the equivalent of several horsepower requires increased MMS and even more BL than classic "old school" theory would indicate. As an example, while in the testing phase of my Keystone "tapped horn" design, I tried an Eminence 4015LF 15" driver, a pair of LAB 12s, and a B&C 18SW115-4.
The low MMS 4015LF was the most sensitive, but well before reaching Xmax the distortion from cone flex was intolerable. The 4015LF has no problem in a BR (bass reflex) cabinet, but can not withstand high power horn loading without sounding awful, the distortion was so bad I did not bother testing it, though I wish I had in retrospect, simply to demonstrate the point to others.
Both the LAB 12s and B&C 18SW115-4 could withstand the throat pressure of the TH with relatively low distortion up to (and slightly beyond) Xmax. "Relatively" is an operative term, both drivers have less distortion at the same excursion in BR cabinets, but the Keystone TH has an average of 6 dB more sensitivity in the pass band of 35 to 100 Hz. Although the 18SW115 was less sensitive than the LAB12 pair, it's far superior heat removal system results in it having several dB more output potential, as it does not have anywhere near the "thermal compression" (voice coil RE increase with heat causing less delivered power) that the decades old LAB 12 has.

Amplification has become a relatively trivial expense, the Berhringer NU4-6000 with four 1500 watt channels, or two bridged mono pairs of 3000 watts each costs only $450, 13.3 pennies per watt. I can clearly remember that when I bought my first Phase Linear (AKA Flame Linear) amplifiers, they were the first to deliver power for under $1 per watt. The "dollar per watt" value held for decades, but now that technology has advanced to the point where there are less than 10 pounds of materials in a 6000 watt amp, compared to hundreds, cost also has dropped by an order of magnitude.

Although JAG and I frequently disagree on some minor issues, I agree with all he has written in the posts in this thread, other than this bit from #18:
"Besides, listening outside isn't all that great. Rooms create a spaciousness effect that you can't get outside (unless you are setting up a 7.1 system outside, which at this point wouldn't surprise me)."

Having mixed live sound (and playback) outdoors for over 40 years, I prefer the sound of no room to the sound of the best rated indoor venues. Outdoors, the sound is as close to the source as it possibly can be, with no room modes or "spaciousness effect" to interfere with accuracy to the source. Digital reverberation is now available for low cost that can duplicate the "spaciousness effect" of any venue, real or imagined, should you desire.

That said, being older and less tolerant of the often nasty outdoor conditions, I'd gladly trade a decent climate controlled room for outdoors for my listening enjoyment. Of course, hearing discreet echos two seconds after returning from a tree line 1000 feet away is kind of a "spiritual experience"...

Art

Last edited by weltersys; 15th October 2016 at 05:46 PM.
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Old 15th October 2016, 06:23 PM   #23
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Weltersys, I feel like you’re confirming what I have originally suspected – in that no one really knows how a set of horns will sound, until they actually build & listen to them. My original plan (above) was to construct the main portion of the horns from concrete, and leave the throat slightly oversized with a steel flange cast into the horn body. This will permit me to bolt on a wooden rear chamber – permitting adjustments to the horn’s throat area (and respective length accordingly) - for a wide range of potential driver types & configurations. I want to be able to take the Pepsi Challenge, and actually hear what sounds best - without having to take a jack-hammer to my horns & mixing fresh concrete. . . . . This was my original question, on my first post on these forums. However I received some negativity for wanting to build full-size horns (i.e. full-space) – and for wanting to use concrete as a construction medium. . . .

And I do have a tree line. . . . About that. .. . Below is a black-powder cannon that I built for the 4th of July. . . . . It's 1028 mild steel, and weighs about 2000 pounds. It's road-towable. I normally fire it (shooting blanks only) over the open water of the Hood Canal. The echo from the mountains on the other side is pretty impressive. It takes about seven seconds - and it’s way more exciting to hear than the initial blast. It’s like rolling thunder – similar to hearing a supersonic jet flyby in the distance. The shoreline however is loaded with trees – thus I'm pretty sure the trees contribute significantly to the echo-return. I’m not sure what to do about the tree line on my property. Maybe I could selectively thin the trees, so that the impedance mismatch between the open air and the woods is not so pronounced?

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Old 15th October 2016, 06:41 PM   #24
TNT is offline TNT  Sweden
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Bo's concrete bass horns. Amazing says those who heard them. Entropy increases as the louder and longer you play them

faktiskt.se • Visa tråd - Allmän babbeltråd om högtalare, konstruktioner osv osv.

Last edited by TNT; 15th October 2016 at 06:44 PM.
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Old 15th October 2016, 07:16 PM   #25
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TB46, those are some pretty clean looking horns. Do you know what the lower cutoff frequency is? Or other design specifications? (I can only read English)

TNT, when people ask me about Entropy, I tell them that Entropy is the quality of potential work-extraction from a thermodynamic heat-reservoir... Or, Entropy is the amount of thermodynamic disorder generated while extracting heat from that reservoir – depending on if you’re glass half-full, or glass half-empty kind of guy. . . . (engineering joke) If you ever want to truly test an engineer’s knowledge-retention, ask him/her to explain the difference between Enthalpy and Entropy.

They should tell you that mathematically (as related to a thermodynamic heat-reservoir) - that the partial derivative of Entropy is equal to the partial derivative of Internal Energy, divided by the absolute temperature of the heat-reservoir in which work is being extracted.

And mathematically (as it relates to a thermodynamic system) – Enthalpy is equal to the Internal Energy of the fluid medium, times the flow-work placed upon that fluid medium.

I'm telling you, this type of stuff keeps people up at night!

Last edited by Entropy455; 15th October 2016 at 07:37 PM.
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Old 15th October 2016, 07:52 PM   #26
TNT is offline TNT  Sweden
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The middle picture in my link above is from one stair down.

//
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Old 15th October 2016, 08:34 PM   #27
tb46 is offline tb46  United States
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Default Post #21 - realhorns.de

Hi Entropy455,

Post #25: "TB46, those are some pretty clean looking horns. Do you know what the lower cutoff frequency is? Or other design specifications? (I can only read English)..."

I had Google Chrome translate it for me, that seems to work. They have some diagrams under 'Produktion', and a lot more pictures throughout their site. There seem to be some interesting ideas as to the coupling of multiple drivers into the bass horn throat chamber, and water cooled drivers. But not a lot of details. :-)

They also have a facebook page.

Regards
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Old 15th October 2016, 08:40 PM   #28
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Ok TNT, now that is pretty darn cool. I didn’t realize what I was looking at initially. I wish I could read the text on the website - without having to copy & paste into a translator (I can only read English)

What is Bo using for drivers? What is the cutoff frequency of the horns? The third picture reminds me of looking down through some deck-grates and into the belly of a ship. I love it!

I've wondered about putting horns into the floor of a large room, and how one would keep people (and pets) from falling into the horn. The grates seem like an excellent idea. They appear to be fully welded assemblies - which I'm assuming would keep them from rattling. . . It's like a big speaker grill.. . .
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Old 15th October 2016, 10:23 PM   #29
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Weltersys, I’m not a big fan of Class-D amplifiers. Yes they are low-cost, lightweight, and very energy efficient. They are a blessing for DJs, and small touring bands. However the Berhringer NU4-6000 for example, has a damping factor of 120. In my opinion, 120 is a serious problem – it is way too low. The threshold for an audiophile quality amplifier is typically a damping factor greater than 300. This is why I am such a big fan of the Macro-Tech series (the older ones that were built with very heavy copper-wound transformers). The MT series packs a big-time damping factor greater than 1000. I personally can hear the difference (i.e. the sharpness in the speaker’s trainset response/fidelity), in between listening to a 1000 damping-factor amplifier, vs a 120 damping factor amplifier.

I think of a speaker like a hammer. There are 5 dollar hammers, and there are 50 dollar hammers. However the hammer alone is a poor indicator as to how well nails will be pounded – as a 50 dollar hammer in the hands of an accountant, will not perform as well as a 5 dollar hammer in the hands of a roofer. Point being - the arm swinging the hammer is a very important performance variable. I like to think of an amplifier’s damping factor as the size of the arm that’s swinging the hammer. Between all of the advertised amplifier specifications (THD, frequency response, Signal to Noise ratio, channel separator, slew rate, etc), it has been my experience that the damping factor specification alone is the best overall indicator as to how well the amp is going to sound. Again, it's just one man’s opinion. . .

Below are bass-guitar speakers that I built for the wife. They are powered by 10-kW of greater than 1000 damping factor amplification. The 18s are tuned for 30-Hz, and sound absolutely fabulous on a 5-string bass! Yes, some people prefer a wall of 10s for a bass, but this system sounds pretty good too. . .



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Last edited by Entropy455; 15th October 2016 at 10:32 PM.
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Old 15th October 2016, 11:07 PM   #30
GM is offline GM  United States
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I had Google Chrome translate it for me, that seems to work.
Me too, I'm lost without its translation capability, though the Oriental pages can be a 'tough' read in English.

GM
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