C-1200/1200H bass horn or transmission line

[more10]

What is the best case scenario for the dog box?

What's a dog box? Separate box?

[4313B]

Try cutting some 12 inch concrete form tube so the rear end is cut on an angle on 30 degrees do it forms a cylinder. Glue a sheet of mdf on the angle end.

This will form a rigid enclosure with good acoutic properties.

[gasfan]

What's a dog box? Separate box?

It's the separate mid-bass enclosure within the main cab.

[gasfan]

Try cutting some 12 inch concrete form tube so the rear end is cut on an angle on 30 degrees do it forms a cylinder. Glue a sheet of mdf on the angle end.

This will form a rigid enclosure with good acoutic properties.

Would the volumes More10 came up with still apply here? I can't see getting more than about a 16-18L cylinder in the cab. I think it wise to heed 4313B's advice and go with a vented enclosure.

[pos]

What is the exact list of drivers you currently have?
A pair of century gold 12" per side would probably have less distortion than a single 2206H per side at any reasonable listening level, and go lower in frequency to boot (you could even avoid using a sub)

If you are looking for an accurate listening experience (hifi...) then the 2390 will probably be the weak point of your system (assuming the 2441 are up to spec).
Some TH4001 clones or A290 would certainly be much better in that respect, crossed over around 600Hz...
I think Woody is currently selling a pair.

[gasfan]

What is the exact list of drivers you currently have?
A pair of century gold 12" per side would probably have less distortion than a single 2206H per side at any reasonable listening level, and go lower in frequency to boot (you could even avoid using a sub)

If you are looking for an accurate listening experience (hifi...) then the 2390 will probably be the weak point of your system (assuming the 2441 are up to spec).
Some TH4001 clones or A290 would certainly be much better in that respect, crossed over around 600Hz...
I think Woody is currently selling a pair.

This thread has gone in a different direction. What we've been talking about has nothing to do with the Century Gold drivers. That discussion changed into the current project I'm on which is a pair of altered 4345s. The drivers I'm using are 2245H, 2206, 2441/2390, and 2405A. Sorry for the confusion. Ian took the helm a while back advising on max main cab net vol.

[4313B]

I think it wise to heed 4313B's advice and go with a vented enclosure.

If you want to cross over lower than 300 Hz.

The 2206H likes 1.2 cu ft tuned to 60 Hz.

Here are the dimensions for Ian's perfectly valid sealed box suggestion. One can pick up the twelve inch sonotubes at Home Depot.

[gasfan]

If you want to cross over lower than 300 Hz.

The 2206H likes 1.2 cu ft tuned to 60 Hz.

Here are the dimensions for Ian's perfectly valid sealed box suggestion. One can pick up the twelve inch sonotubes at Home Depot.

Done. Looks like that leaves lots of room to experiment with. I'll be removing a dividing wall so room dimensions will eventually be around 22'x20'.

[more10]

I'll be removing a dividing wall so room dimensions will eventually be around 22'x20'.

That is 40 m2, just about the room size you need for bass horns :-)

Do you have any restrictions on the size of the speakers, or can you build big?

How do you listen? Always sitting in the sweet spot, or walking about? Always listen alone or with friends?

Are you going to use analog or digital crossover?

[gasfan]

My intention is to build the 4345s as per the recipe you guys have put together for me. Albeit with the Hartsfield horns and 2206s. If I don't like them, I can always swap out a different baffle and top end arrangement. But I have a hunch I will. Not sure I want to use the C-1200s in bass horns though. I like a well controlled bottom end. The very reason I'm using the Acoustat TNT 200s. I usually listen by myself. Not too many people care about this stuff. When company is present, it's always just back round music. Some times I turn it up and listen out side through the patio door. Good bass transfer out there. I will use a couple of DCX2496s. I'm thinking with Pos' volume control kit.

[more10]

I think your plan is excellent. I have simulated the 2245, and the enclosure is very close to a "maximum flat response". You could make it go deeper, but the box would be too big.

The Hartsfield horns (with the lens attached) and the 2405 have excellent dispersion, you will have a wide sweet spot. The Hartsfield horns loose some energy at higher frequencies, but you will be able to correct that in the filter.

Because of the 12' and the larger horn, the box will have to be taller than the 4345. Taming the resonances (between top and bottom) inside the box will be your biggest challenge. The first standing wave will have a frequency of about 170 Hz (1 meter tall cabinet). Another way to handle the standing wave is to lower the crossover frequency between the 18' and the 12'. I also believe that the 12' will sound better in the midbass region, but then you will have to plan for letting it go lower.

The Behringer hasn't got the best reputation, but it can be improved.

Mårten

[gasfan]

I think your plan is excellent. I have simulated the 2245, and the enclosure is very close to a "maximum flat response". You could make it go deeper, but the box would be too big.

The Hartsfield horns (with the lens attached) and the 2405 have excellent dispersion, you will have a wide sweet spot. The Hartsfield horns loose some energy at higher frequencies, but you will be able to correct that in the filter.

Because of the 12' and the larger horn, the box will have to be taller than the 4345. Taming the resonances (between top and bottom) inside the box will be your biggest challenge. The first standing wave will have a frequency of about 170 Hz (1 meter tall cabinet). Another way to handle the standing wave is to lower the crossover frequency between the 18' and the 12'. I also believe that the 12' will sound better in the midbass region, but then you will have to plan for letting it go lower.

The Behringer hasn't got the best reputation, but it can be improved.

Mårten

Stock inside dimension is 39" tall. There will be lots of room to tailor response with Ian's mid-base dimension. Cab will be heightened according to Ian's initial max net vol. Seems to work out. As I stated, I love overkill. There will be no problem with internal resonance.(wishful thinking?)

[gasfan]

BTW. It's not my plan. It's you guys' plan. I'm just the grunt. And a very tickled one at that! I will keep you updated with pics.

Thanks All,
Peter

[Ian Mackenzie]

What I suggest you do is decide next is decided on your listening chair and then measure your ear height so you can start working out the front baffle.

From that data then format the vertical location of the horn and slot so the horn is at ear height or a bit above (like the 4344mk11).

The reason for this approach is that the vintage horn lense assemblies tend to have a comparitively narrow vertical response with increasing frequency.
http://www.lansingheritage.org/images/jbl/specs/pro-comp/horns-lens/page3.jpg
http://www.lansingheritage.org/image...2405/page2.jpg



In order to have a linear vertical high frequency response it is useful to be listening on or near the vertical axis.

This along with the choice of drivers and crossover characteristics will have a bigger foot print on the overall sound quality than attempts at perfection in other aspects of the design.

To allow some flexibilty one approach (to prototying) is the make up some modular boxes out out mdf for the woofer, mid bass and horn and stack them together to get a feel for how it will work (and look) before making the finished boxes. This will allow you to preview the design at concept stage so you can make changes to drivers and layout empirically to meet your own preferences.

Interesting this is exactly what happens behind the scenes at Northridge (or it used to before they fired the guys in the custom shop)

Later on when you start looking at the frequency response the design point will then be at ear height as opposed to compromising the response with a sub optimal ear height.

(the 2397 would be another option if wider vertical polar response is preferred, this is an outstanding horn even by todays standards)

Because the 2206 enclosure and the horn assembly occupy significant displacement in the main enclosure they will impact on any likely boundary related standing waves.

Check out the references threads on text books that explain all this stuff. One of the better authors was John Eargle who was pretty much an authority on the whole E2E recording process.

http://www.lansingheritage.org/html/.../technical.htm

[gasfan]

Thank you, Ian. I had no idea what I was actually getting into when I decided I want to build me a pair of JBLs. I have done some research on the 2390s and am aware of their limitations. But I always want to be right dead on the sweet spot anyway so that will be no problem. I know the 2397s are a very popular horn for good reason but I just love the look of those lenses. I will build them as short as possible. They need 6" at the bottom, right? That puts the horn at around 44" or there about with the 2405 at about 50 with the 2206 in place. I'm 6'2" so that's perfect. My listening chair will be what the speakers demand. I was thinking to simply line up the drivers and put the 2405 outside on top. I've seen some examples of this on the forum. I thought this was for the sake of imaging. A 30" box can use all the help it can get. Either that or I was wondering if it could go behind the lens.