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Basshorns - Pro and Con [message #17348] Thu, 13 January 2005 14:15 Go to next message
Wayne Parham is currently offline  Wayne Parham
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I recently made a post about basshorn folding methods, and it prompted a discussion about the pros and cons of basshorns in general. While I realize that they have their strengths and weaknesses, my earlier post was really comparing folding patterns and not comparing horns with other types of enclosures. But I'd like to enter into that discussion here.

My position has long been that basshorns are too small to support the lowest frequencies unless they are huge things, built-in to the room. After all, bass frequencies are dozens of feet long. You really can't even have a 1/4 wave resonator working at the bottom of the bass range unless it's over ten feet long. So to have a horn be of sufficient length and area to really support the bottom octave requires a structure that is literally as big as a house.

Still, you can make a scaled down version and gain some of its benefits. A truncated horn will work pretty well in many ways, particularly when the room corner is used. But the point is that it isn't realistic to think that a portable basshorn cabinet can support the deepest bass frequencies. Every one I've seen becomes more and more like a quarter wave resonator down low, and then reverts to being a bandpass or direct radiator. That's fine, nothing wrong with that. But it does mean that the lowest frequencies have 10x less power. The response curve isn't flat. What is happening at the bottom frequencies is direct radiation. You can either EQ it back up or limit output to the passband and forget about the range down low.

To me, it was always ironic that some of the most vocal hifi horn proponents - those that dismiss the use of a direct radiating woofer - were often using equalization of their basshorns to increase power for the deepest bass notes. What that really means is that their basshorn system is actually a hybrid, being used both as a direct radiator down low and a horn higher up. There's no problem with that approach, none at all. But that means the talk of "all horns or no horns" is actually just talk because in fact, the basshorn is not fully functioning as a horn.

Still, if what you want is maximum SPL, a horn is the way to go, even a truncated horn. Over the range where efficiency is increased, distortion is decreased. Even if it loses this ability down low, the benefit is gained over the horn's passband and that sometimes makes it worthwhile. As long as you have the real estate, because even a highly truncated basshorn is pretty large.

Those are some of my thoughts. What are yours?

Re: Basshorns - Pro and Con [message #17349 is a reply to message #17348] Thu, 13 January 2005 14:49 Go to previous messageGo to next message
Bill Wassilak is currently offline  Bill Wassilak
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>>The response curve isn't flat. What is happening at the bottom frequencies is direct radiation.

Your right about bass horns operating down low. To get the Lab subs operating at a nearly flat response curve down to 30Hz, Tom Danley says you have to have 6 of them. And even then the mouth area still a little small to support 30Hz wavelengths.

Slightly off topic [message #17352 is a reply to message #17348] Thu, 13 January 2005 16:14 Go to previous messageGo to next message
pgolde is currently offline  pgolde
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Registered: May 2009
Chancellor
I have a 20' x 40' inground pool in my backyard that needs a new liner, I have been considering filling it in with dirt. I have also been thinking this 20x40 concrete foundation would be a waste to just bury.
I think 20ft might be wide enough for a true bass horn mouth, or maybe I've completely lost touch.

Re: Slightly off topic [message #17353 is a reply to message #17352] Thu, 13 January 2005 16:20 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18782
Registered: January 2001
Illuminati (33rd Degree)
Yup, that'd do it.

Re: Basshorns - Pro and Con [message #17355 is a reply to message #17349] Thu, 13 January 2005 20:40 Go to previous messageGo to next message
Earl Geddes is currently offline  Earl Geddes
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Registered: May 2009
Master
This is a classic mis-discussion.

I mean are we talking living rooms or stadiums here? There is a pretty big difference in how one approaches the two problems and trust me they are not the same.

I do a lot of pro sound work, but in all honesty, they don't really care about quality. Its all SPL, flying and trucking. And oh yea, if it also sounds good, thats OK too.

I live for small rooms, currently home theaters, where quality in the sound is what its all about. In that space I prefer NOT to have a horn in a region where it does not provide an advantage. In a small room below about 200 Hz. its not about the kind of enclosure, closed, ported, horn, whatever, its about how many. I recently had dinner with a group of home theater specialists and we all agreed that in the very LF domain its all about numbers - at least four, six is better. I have five. And they don't need to be powerful - hell there's five of them! So LF SPL from a single source in any of my small rooms is irrelavent. So much for large horn enclosures.

Now when we can strt to control directivity and the ear/brain combination starts to tell us where the sources and refections are THEN directivity control becomes everything - it controls the sound quality in small rooms at the mid -> HF.

Keep your LF horns, give me six woofers, three monopoles and three ported.

Re: Basshorns - Pro and Con [message #17357 is a reply to message #17348] Fri, 14 January 2005 08:27 Go to previous messageGo to next message
Adrian Mack is currently offline  Adrian Mack
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Illuminati (1st Degree)
Thats pretty much what I think too. I personally dont like the idea of EQing the botttom end of a basshorn, it is against the very benefits a horn offers. I like to have the longest path length possible but with a somewhat undersized mouth for a home, as the eigth space location generally lifts up the bottom end lost from the undersized mouth.

Re: Basshorns - Pro and Con [message #17359 is a reply to message #17355] Fri, 14 January 2005 10:36 Go to previous messageGo to next message
pgolde is currently offline  pgolde
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How do you deal with cancellation from the 5 different LF sources?
Are they all placed in the same location?

Re: Basshorns - Pro and Con [message #17361 is a reply to message #17359] Fri, 14 January 2005 13:44 Go to previous messageGo to next message
Earl Geddes is currently offline  Earl Geddes
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Of course they are not all in the same location. That would be the same thing as having one speaker 5 times bigger. No they are placed arround the room. There is a lot of discussion about "where" to place them, but my opinion is that placement is not critical.

Reagrding cancellation, look at it as a problem in probability, which is what it really is. What is the prbabilty that I will have five vectors - each sources magnitude and phase - that add up to zero? Its just about nil - doesn't happen. With two sources, it is highly likely to happen at some frequency and with one source it is guaranteed to happen when the source is at a node. But with five sources, it virtually can't happen.

Thats really the point. The five sources will always have a smoother average than any lessor number. Its simple statistics.


Re: Basshorns - Pro and Con [message #17362 is a reply to message #17361] Fri, 14 January 2005 17:39 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18782
Registered: January 2001
Illuminati (33rd Degree)
Good point. Have you seen what Toole writes about it?

Re: Basshorns - Pro and Con [message #17363 is a reply to message #17362] Fri, 14 January 2005 19:53 Go to previous messageGo to previous message
Earl Geddes is currently offline  Earl Geddes
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Registered: May 2009
Master
Yes I have seen Floyd's discussion. This is basic Acoustics 101. His analysis assumes perfectly rigid walls and even their studies were done in faily rigid rooms. I do not build my rooms like this. You see, if the walls are limp and well damped at LF then the room appears to be free space, or very close to it. But of course we don't want to be in a free space room at higher frequencies so the walls must be rigid at those frequencies for a good room ambience and spaciosness. The construction techniques are well outlined in my texts. Floyd was most interested in my construction techniques when he read my book as he had never tried them.

Please remember that I did my PhD thesis on small room acoustics, and that was more than 20 years ago, so my concepts are based on some pretty substantial theroy. Far more in depth than the simple acoustics theories allow.



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