C-1200/1200H bass horn or transmission line

[gasfan]

I have 4 of these drivers, brand new never used. Got them on E-bay a number of years ago. They look and test perfect but the rims are badly cracked and dented. The solid seat past the outer perimeter where the gasket goes is still perfect so still usable. The damaged part could either be routed off, or they could be used out of sight. I was thinking I'd like to try my hand at a transmission line project. Thoughts?

Peter

[speakerdave]

This is just me wondering, but why not use them the way JBL used them?

[gasfan]

They're Century Gold drivers but as I stated, damaged and don't look so good. In what other configuration were they used?

[pos]

They were used in the 50th anniversary century gold speakers.
http://www.hiendoption.com/main/components/com_virtuemart/shop_image/product/JBL_CENTURY_GOLD_4dd11e895b529.jpg
As you can see the rims of the drivers are covered and not meant to be seen, so the dented look might well be normal :D

These are supposed to be very good drivers (evolution of the 128H), to be used as direct radiator in bass reflex boxes of around 40 or 50L tuned around 30 or 35Hz.
You would probably need some 1200Fe to beat them.
A pair per side would probably be a very good match for large horns like the TH4001 or A290.

[grumpy]

... except I -think- those gold rims -are- the frame, and very exposed.

[gasfan]

... except I -think- those gold rims -are- the frame, and very exposed.
That is correct. So?

[pos]

That is strange as the 5" mid also used in the LSR32 does not have integrated gold rims.
Anyway that is just an aesthetic matter: either add a rim yourself, or mount them from the rear of the enclosure and call it done.

[speakerdave]

. . . or mount them from the rear of the enclosure and call it done.

I don't think that's possible with that rim.

It seems that for some reason there were a number of these that somehow were dinged up. I remember seeing them on the market a few years ago. I have a pair that are not dinged, but the "gold" is flaking off (another case of a poorly prepared surface, I'm guessing), and they are not attractive for that reason. But it looks to me like they cannot be mounted on the back of the baffle just as the many JBL squircle frames cannot. If there is a trim ring on the Century gold, maybe that can be obtained from JBL. Also, possibly the one from the LSR32 can be made to work.

[gasfan]

I don't think that's possible with that rim.

It seems that for some reason there were a number of these that somehow were dinged up. I remember seeing them on the market a few years ago. I have a pair that are not dinged, but the "gold" is flaking off (another case of a poorly prepared surface, I'm guessing), and they are not attractive for that reason. But it looks to me like they cannot be mounted on the back of the baffle just as the many JBL squircle frames cannot. If there is a trim ring on the Century gold, maybe that can be obtained from JBL. Also, possibly the one from the LSR32 can be made to work.
As you can see in the pic, the rim is integral and also the finished/presented surface. Did you not just state you have a pair? I don't see why you could not work out mounting them from the rear, but that would cause response problems with the baffle. Speakers are mounted with the frame either flush or proud of the baffle for this reason. Are they not?

[speakerdave]

As you can see in the pic, the rim is integral and also the finished/presented surface. Did you not just state you have a pair? I don't see why you could not work out mounting them from the rear, but that would cause response problems with the baffle. Speakers are mounted with the frame either flush or proud of the baffle for this reason. Are they not?

I wasn't sure from the photo whether there is a trim ring or not. Mine are in boxes up on a shelf and I have not looked at them for a long time. I wasn't trying to debate about it really; just sharing my experience. You can mount them any way and any where you like.

[gasfan]

I wasn't sure from the photo whether there is a trim ring or not. Mine are in boxes up on a shelf and I have not looked at them for a long time. I wasn't trying to debate about it really; just sharing my experience. You can mount them any way and any where you like.
My only intent is to be accurate. I don't mean to take you to task. I need you guys' help. I have yet to complete my first project. I'm presently deliberating with my cabinet maker on the altered 4345s I'm about to undertake. I love overkill. I want to sandwich 1/2" HDF between 2 layers of 1/2" baltic birch with a 1/16" layer of modified roofing felt between the innermost 2 layers. He tells me this is not doable without a cupping problem. It could be as much as 1/4" on a 5'x5' sheet. Will construction and bracing deal with this issue? On the other hand, 1 and 1/2" laminated baltic birch is no problem. But I want to seriously damp these cabs which are about 2cu.ft. larger than original. You guys' insight and experience is priceless to me here.

[more10]

I have used damping glue from Swedish Swedac (http://www.swedac-acoustic.com/pages/vibra.damp.htm#DG A2) with great success. This kind of glue dampens vibrations. When knocking on a wook laminated with this glue the sound is dull.

You must be able to get the same kind of glue in Canada. Importing from Sweden is serious overkill :-)

[Ian Mackenzie]

My only intent is to be accurate. I don't mean to take you to task. I need you guys' help. I have yet to complete my first project. I'm presently deliberating with my cabinet maker on the altered 4345s I'm about to undertake. I love overkill. I want to sandwich 1/2" HDF between 2 layers of 1/2" baltic birch with a 1/16" layer of modified roofing felt between the innermost 2 layers. He tells me this is not doable without a cupping problem. It could be as much as 1/4" on a 5'x5' sheet. Will construction and bracing deal with this issue? On the other hand, 1 and 1/2" laminated baltic birch is no problem. But I want to seriously damp these cabs which are about 2cu.ft. larger than original. You guys' insight and experience is priceless to me here.

With the 4345 design the main enclosure is band limited from f3 to 300 hertz. The issues with MDF are above that and normally only come into play when running a sans diy 2 way with a crossover point of 750- 900 hertz

So attempting to damp reasonance above 300 hertz is a bit pointless.

The dog box is so small that its naturally rigid anyways.

Suggest you pick either 1 inch mdf or if affordable birch ply and brace liberally to avoid flexing.

If you are going for a bigger box dont go over board unless you are making a 20 hertz sub only box.

10.3 cu ft 3 net Vol @ 27.2 hertz fb is optimum unassisted alignment and will extol all the virtues of the 2245 and then some for use from Fb to 300 hertz

If you go bigger then yes the box dimensions become a resonance control issue and so does the group delay of the associated tuning for "music" play back.

The thing to understand with the 2245H is that it will boundary couple more than you will realize and with the added room gain you will have more low end bass lift then you know what to do with.

I have personally found the above tuning a works very well domestically as it has a gradual fall below 100 hertz but the resulting "in room" response is smooth and extended with a lot of punch but without the bloating some users write about with the 4345.

The actual factory boxes where perhaps smaller than they need be for marketing purposes and the smaller box tend to lift the 40-60 hertz range on paper which is not what you want domestically Free field or flush mounted this is not an issue but in a domestic room space and placement is always an issue with the 4345. So I tend to get the woofers up off the floor 6 inches if I can. Otherwise you end up resorting to parametric eq cutting the bass back as 2245 will excite all the room modes with its boundary coupling.

I have a pair of Gold Century woofers too and I was considering using them like below my Tad's like GT did in his much loved ultimate diy home system.

[gasfan]

Excellent, Ian. Thank you. 10.3 it is! Understanding and applying T/S parameters is a hard lesson to get my head around. Your explanation borne of experience is very generous of you. I've been accumulating components for a few years now but have been afraid to get started. No fault of the Lansing Heritage site. You do have to know what questions to ask. You've been very insightful indeed. As were a couple of others on this site last fall directing me towards a 4-way , 4345 type configuration. I now have a starting point. Where can I get a look at GT's system?

Peter

[Ian Mackenzie]

http://www.audioheritage.org/vbulletin/showthread.php?9951-Greg-Timbers-amp-DIY&highlight=GT%27s+system

[gasfan]

As I mentioned, these are altered. In searching the forum I found references to the 2206s as mid base in one of your threads. It just so happens they are what I have. I will also use 2441/2390s. They will be fully active. What is the best case scenario for the dog box?

[gasfan]

I guess my question is which type of enclosure will take best advantage of the 2206, sealed or ported? It only has to work from about 300hz so is it possible to downsize it to fit? How do I calculate that? Or should I just use a 1cu.ft. box which fits?

[more10]

If you choose ported for 2206 you will have problems integrating it because the port will shift the phase considerably. Use WinISD Pro Alfa to simulate response of your boxes. You will also need to handle baffle step in you design.

[gasfan]

Does the 2206 have to have a 4cu.ft. sealed dog box?

[more10]

I believe that if you are going to use the 2206 from 300 Hz you can build the box very small. But simulation is needed, I can do one for you.

[gasfan]

I believe that if you are going to use the 2206 from 300 Hz you can build the box very small. But simulation is needed, I can do one for you.
Well, coming to me, that would be more priceless information, wouldn't it. Thank you

[ivica]

Does the 2206 have to have a 4cu.ft. sealed dog box?

I think that for 2206 'closed box' of 1 to 2 cft would be more then enough (over 300Hz), but using 2206 over 1kHz, would be may be questionable
Regards
Ivica

[gasfan]

I think that for 2206 'closed box' of 1 to 2 cft would be more then enough (over 300Hz), but using 2206 over 1kHz, would be may be questionable
Regards
Ivica
The 2441/2390s will take it from probably 800, I'm thinking.

[more10]

Well, coming to me, that would be more priceless information, wouldn't it. Thank you

2206H/J 300 mm (12 in) Low Frequency Transducer (http://www.jblpro.com/pub/components/2206.pdf)


Baffle Cutout Diameter
Front mount or rear mount: 280 mm (11 1/16 in)
Depth7: 127 mm (.5 in,)

Volume Displaced by Driver: 41(0.15 ft3)
Clearance of at least 76 mm (3 in) must be provided behind the magnet assembly and the
gap vents to allow sufficient air circulation and proper cooling to take place.


The smallest box you can make is 2.8 x 2.8 x (1.27 + 0.76) - 4 = 12 liter. This gives a QTC of 0.785. You will get flat response down to 200 Hz. Group delay will be 0,4 ms at 300 Hz. Maximum SPL 124 dB. The first standing wave (half wave) between top/bottom and right/left will be at 607 Hz . You will have a quarter wave resonance between back and front at 420 Hz.

If you make the box dimensions according to "golden ratio" you will have a box of 20.3 x 32.8 x 53.1 cm. This will give a volume of 31 liters. This will give a QTC of 0.57, very close to "Max flat delay" optimization. You will gain 0.1 ms in group delay and loose 1 dB at 300 Hz. I have no idea if a golden ratio box will improve anything regarding standing waves :-).

If you make a vented box of 27 liters (quasi butterworth) the result will be very close to the golden ratio sealed box. Above 300 Hz the phase will not be a problem (I was wrong in an earlier post). You will have the added benefit of venting out heat through the ports.

56806568095680856810

[more10]

Impedance and maximum spl.

5681156812

[4313B]

I've given up on the golden ratio boxes, they just don't seem to sound as good as the deeper boxes. Perhaps turning the golden ratio box sideways (1.62:0.62:1 instead of 1.62:1:0.62) would work. I almost alway use the 1.25:1:0.8 or 1.2:1:0.8 boxes.

The standing waves can clearly be seen in an impedance curve of the box without fiberglass. Fiberglass marginalizes the standing waves. I know alot of people QQ when dealing with fiberglass though. Sucks to be them I guess.

[gasfan]

Impedance and maximum spl.

5681156812

My goodness! Is there anything you need? Is there a benefit to a sealed box with this driver? The faster the better. I want to hear every individual wire on the snare.

[4313B]

My goodness! Is there anything you need? Is there a benefit to a sealed box with this driver? The faster the better. I want to hear every individual wire on the snare.One hump instead of two screwing up your passive low pass filter? :rotfl: If you're active you don't care.

Don't forget about heat build-up in a sealed box. Some guys beat the crap out of this stuff and wonder why their coils fry in sealed boxes.

[more10]

Red = 31 liter sealed
Yellow = 12 liter sealed
Blue (hard to see) = 27 liter vented

One benefit of the sealed box is that you can build it smaller. The smaller box the worse impulse response though.

I believe maximum spl is 600W sinus. But in reality you will be able to feed this with a 1 kW (per channel) amp. My experience is that you don't need more than 300 W (8 ohm) per channel for midrange.

[Ian Mackenzie]

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.

[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.:yes:

[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/images/jbl/specs/pro-comp/horns-lens/page3.jpg)http://www.lansingheritage.org/images/jbl/specs/pro-comp/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/jbl/reference/technical/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.

[more10]

A Loudspeaker for the Range of 5 to 30 kc. B.H Smith and W.T Selsted (http://www.audioheritage.org/vbulletin/showthread.php?9871-Smith-Selsted-Tweeters&p=101069&viewfull=1#post101069). Scanned from the original 1950 article introducing the Smith horn.



This type of horn has an interesting performance characteristic. When listening to it one can not tell precisely from where the sound is coming. This is due to the fact that the focus of the sound source is not the same in the vertical and horizontal planes. The source of sound in the horizontal plane appears to be at the throat of the horn, while in the vertical plane it appears to be at the mouth. This effect is startling in a similarly designed horn for the 500 to 5000 cps range.


I have not listened to these, so I have no opinion myself.

[gasfan]

A Loudspeaker for the Range of 5 to 30 kc. B.H Smith and W.T Selsted (http://www.audioheritage.org/vbulletin/showthread.php?9871-Smith-Selsted-Tweeters&p=101069&viewfull=1#post101069). Scanned from the original 1950 article introducing the Smith horn.





I have not listened to these, so I have no opinion myself.
Neither have I. From that description, I wonder what influence it has on imaging.