Romy the Cat wrote:

...my light woofers would not be the optimum solution and I might need to use 18”-24” woofers.

zanon wrote:

My room is big … So how to measure it's size? Just write in floorplan of the entire house.

I do not think that we need to measure room size but we need to understand the acoustic consequences of the room size and to measure the acoustic response of the room.

el`Ol wrote:

At least for corner horns I think I can say that lightweight drivers are the better solution. HBM's corner horns with, I think, 18" drivers sound as if an avalanche was rolling over you, something I didn't experience with corner horns containing four 8" drivers I heard at the home of a Manger addict. An other difference was that these horns were completely built of thick soft-fiber boards, nothing hard at all, but I think the drivers played the mayor role. But what I learned from HBM is that corner horns are less dependent on "real" corners as one usually thinks. In the visiting a reader column of a German hifi magazine I even saw a system where he avoided an existing corner to get better results. What bout this?

Oliver, yes, the idea to use midbass channels in the position that you specify is an interesting idea. Unfortunately I have no corners in there in the real room.  I do not think about alternative midbass channels now (with exception of temporary channels) and I hope I will go during summer for my midbass horn in attic.

jessie.dazzle wrote:

What am I saying? You might consider building a pair of "end of life" lower-bass channels now, while waiting to get on with construction of the mid-bass horns. This would be a good investment of your time and money, as you will need them in any case, and it would allow you to really use your system again.

Jessie, I know about my need in future to make lower-bass channels but I would like first to know how low my midbass horn will go in the room acoustically. Lower-bass channels that worst at sub 30 and sub 60Hz are different and I would like to know what I am dealing with. Generally the idea is to get proper sound with midbass channel and only THEN to add the lower bass by the need. The octaves under bottom are very short, room modes are wide and any improper calibration or use lower bass will mask out problems with midbass. The lower bass is in a way a “simple channel”, so it would not be a problem to employ it when I need it…

jessie.dazzle wrote:

What am I saying? You might consider building a pair of "end of life" lower-bass channels now…

What would be most interesting would be to capitalize on the possiblity you have to make use of the basement volume as an enclosure for the lower-bass channels. This wold however, almost certainly introduce floor vibrations requring that you find a way to float at least your turntable, if not the entire system, in space.

Romy wrote:

"...The "end of life" lower-bass channel in my view is not some kind of very well and ambitiously-made lower-bass transducers, enclosures and amplification, but rather a good lower-bass channel [is] very ambitiously and very strategically placed in a given room..."

"...A proper lower-bass channel shall not work against the rest system and against a room, so the positioning and its output might be defined before the construction..."

Positioning: Assuming you don't use the basement as an enclosure: Build the enclosures on wheels (for carpeted floors; large diameter, wide wheels).

Output: Given the possibility to modulate amplitude independently of the other channels, I'll assume the variables left to consider to be the following:

1 -Size of driver (multiple pairs of 10"-15" vs a single pair of 18"-24")
2 -Type of enclosure (fixed position, possibly vented, possibly located in the corners vs mobile sealed enclosures, vs making use of the basement as an enclosure)
3 -Type of amplification (Good SS vs ?)

"...at this point have no idea what would constitute the "end of life" performance status for bass in my room..."

Here is my possibly over-simplified view:

Assuming one will not get anything under 50Hz (usable) from a 40Hz horn, I interpret the mission of lower-bass channels in the context of a horn system as follows: 

To handle everything from 60Hz and below, producing a quality of lower-bass compatible with the mid-bass horns.

This for me meant large, sealed (easily repositionable) enclosures.

Driver size: For sound below 35Hz, in the context of an all horn system, I do not subscribe to the multiple, smaller-diameter drivers approach. My reasoning (certainly open to debate) is as follows: The multiple, smaller-diameter drivers appraoch, if it is really to produce sound of useful amplitude below 35Hz, would likely require a ported enclosure. Some of the gain in quality associated with the smaller drivers would thus be sacrificed in the interest of quantity (amplitude); a difference likely rendered more perceptible in the presence of mid-bass horns. If there is no requirement for sound below 35Hz, the multiple, smaller-diameter drivers appraoch might be better. After having lived with it, I would not want to go without the 18-36Hz octave.

jd*

jessie.dazzle wrote:

Assuming one will not get anything under 50Hz (usable) from a 40Hz horn, I interpret the mission of lower-bass channels in the context of a horn system as follows….

Hm, this is a bit tricky with bass. A playback might not have anything usable less than 50Hz but it is not necessary mean the lower bass section needs to be started from 50Hz and do down. This is the whole idea of the lower bass section that it might very much would need to be let say low-passed at 30hz with second order and to be enough to load the room properly. I don’t think that those things the might be recognized without actual trying, listening and measuring in a very specific room.

jessie.dazzle wrote:

Driver size: For sound below 35Hz, in the context of an all horn system, I do not subscribe to the multiple, smaller-diameter drivers approach. My reasoning (certainly open to debate) is as follows: The multiple, smaller-diameter drivers appraoch, if it is really to produce sound of useful amplitude below 35Hz, would likely requre a ported enclosure. Some of the gain in quality associated with the smaller drivers would be sacrificed in the interest of quantity (amplitude); a difference likely rendered more perceptible in the presence of mid-bass horns. If there is no requirement for sound below 35Hz, the multiple, smaller-diameter drivers appraoch might be better. After having lived with it, I would not want to go without the 18-36Hz octave.

Well, the multiple smaller-diameter drivers are good as they allow creating cylindrical waveform of line array. Again, what smaller-diameter drivers we are talking about? I use 10” but they have free air resonance of 19Hz. Not any of 18” drivers have such a low resonance. Still, if a channel is crossed relatively low then I would also probably prefer a single large driver instead of multiple drivers, or course only in sealed or infinite baffle. I however, do not make any presumption about the type of the enclosure. The enclosure I have in mind would be 40-50 sq feet at least and two of them is HIGE space. Where they would be and how they would interact with room is totally unknown. Make it portable on while in my view is unnecessary as moving such of enclosures no one will, or at least I would like not to. They need to be built to order for the very specific space of the house and to sit there. Where this “very specific space of the house” might be I do not know yet in my house, so I do not know what shape of the lower bass enclosure I would needed. I am not rich enough to make this project multiple times.

Bill wrote:

If you are going to build such a huge cabinet or put a hole in the floor to use the basement as a chamber, why not just build horns in the basement with a straight 8-10 foot section in the basement with the back chamber resting on the floor, cut through the floor and put a 90 degree angle with the mouth facing the listening position. If you put the mouth against the floor and side wall you could build a quarter horn with a length of about 16 ft. and mouth about 9x9 ft. May not go quite down to 20 Hz. but should put out at least 30 Hz. using your present amp?  Problem would be the time delay of the bass to the mid bass horn which would have to be overcome probably with an analog or digital  time delay. You could use a 24/96 active crossover such as that from Behringer  which would also act as the active crossover, time delay and even parametric equalizer for your  68 Hz room bump.      I know, there goes the living room and the W.I.F., but this is high end audio and there's no wife involved. Lucky you for this.      Before I got out of analog, I was thinking of building a 30 Hz horn to replace my 50 Hz. 6 ft. straight horn by building it from the ceiling down ( 14 feet, with one 90 degree angle facing toward the room in the corners of the room, but couldn't figure out how to do it years ago without having to go digital for the time delay for the rest of the system. Now its easy if you don't mind doing everything in digital.

The midbass horn is a legitimate horn but I do not believe to the lower bass horns. I have an article dedicated to the subject:

http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=7213#7213

Also, the negative impact of using digital or even active analog crossovers is irrelevant from the fact what analog or digital playbacks we use.

zanon wrote:

Do you mean that if you begin with digital source, it does not matter whether you use a digital crossover or not since the "damage" has already been done?

Romy the Cat wrote:

I use 10” but they have free air resonance of 19Hz. Not many of 18” drivers have such a low resonance.

el`Ol wrote:

The lowest I know is the Fertin with 23 Hz. http://www.fertin-acoustic.com/hp_46ex.php

Fertin does 23Hz with 18inch. The Scan-speak did with 10 inches

http://www.scan-speak.dk/datasheet/pdf/25w_8565-01.pdf

..pass the SD-1 motor. But I am known to be sucker for those 8565 drivers…. I have 8” version of them and even they are good.