For the sake of this thread, I’m going to refer to this as a pair that I am building, but I will be actually building three so that one can be used as a center channel in my theater. These will of course, be used for theater, but will get tons of musical use.
This is going to be a fully active set up, with the exception of the horns, which will use charged couple passive crossover designed by JBL. For the upper end, I will be using a 045Be beryllium 1” horn tweeter/super tweeter and a 435Be 3” beryllium mid loaded in a H9800 horn.
For the safety of these drivers, I think it would just put me at ease if I were to drive them with this passive crossover
The crossover, the horns, and the midbass drivers were pulled from a trio of SK2-3300s.
That brings me to the midbass drivers which are going to be 251J. These are a fairly rare and special version of this series of driver, they weren’t used into many designs, they have the aquaplas and added mass over the originals. For the bottom end, I’m going to be using 15 inch woofers that were used in some of their nicer subwoofer designs, though they have been used in three-way designs with much success, they are 1500 sub drivers.
Dan
This is going to be a fully active set up, with the exception of the horns, which will use charged couple passive crossover designed by JBL. For the upper end, I will be using a 045Be beryllium 1” horn tweeter/super tweeter and a 435Be 3” beryllium mid loaded in a H9800 horn.
For the safety of these drivers, I think it would just put me at ease if I were to drive them with this passive crossover
The crossover, the horns, and the midbass drivers were pulled from a trio of SK2-3300s.
That brings me to the midbass drivers which are going to be 251J. These are a fairly rare and special version of this series of driver, they weren’t used into many designs, they have the aquaplas and added mass over the originals. For the bottom end, I’m going to be using 15 inch woofers that were used in some of their nicer subwoofer designs, though they have been used in three-way designs with much success, they are 1500 sub drivers.
Dan
So I’m thinking the only things I’m really looking for opinions on (which you can give your opinion on anything you wish, if you think this is a stupid idea feel free to say so) would be the cabinet for the mid base and potentially crossover points. Since this will be active, I can play around with the crossover points.
The original speakers that most of these drivers were pulled from the large horn crossed to the 10 inch driver at 800 Hz. Since I’m using that same passive crossover for the top end, I plan on doing the same. I figure I will have the 15 inch woofer play down to maybe 40 Hz or so. At least for movies, I could potentially go a bit lower for music. They will be crossed to a pair of 24 inch subwoofers at that point as I don’t want to put too much stress on the 15s. I am still trying to decide where to cross the 15 to the 10. Maybe 200 Hz? 250 Hz? At that point, the 15 will be playing a fairly small bandwidth, but that’s okay. When I mostly wanting from the mid bass and woofer is to get tons of impact, while at the same time getting the highest fidelity. I am guessing that the tens would have the best transient response seen as they have the least amount of mass to control the given motor strength.
Here is some information on the drivers: the 15s are the 1500 sub drivers sold by PE awhile back. The same driver used in the Revel Ultima sub. From what I understand it is quite similar to the W1500H. I know it may not be exact, but I’m thinking I want to go all sealed cabinets to keep cabinet volume down plus, I don’t want multiple tunings in the same room if I port the 24s. I know they have been used with success in sealed cabinets ranging from 2 to 2.5 cubic feet. Some of gone slightly smaller, and some have gone slightly larger. I figure if I have DSP and realistically, I am only running them down to maybe 30 Hz listening to music I can get away with not going huge.
15” woofer
https://www.audioheritage.org/vbulletin/showthread.php?7113-Project-Array#9
10” 251J
https://www.audioheritage.org/vbulletin/showthread.php?11985-251J
These are some parameters of the drivers.
What would you all do for the 10s. If I cross them as high as 200-300 hz I really don’t have to go all that large. Plus the original cabinets weren’t all that big, I was thinking maybe 1 cubic foot sealed? Maybe a little larger and crossing lower to the 15, I am wanting heavy impact in the chest.
I asked this question quite a while back on Audio karma, but I now have the test cabinets for the woofers built, and I want to start the test cabinets for the midbasses. Of course the other two drivers won’t need cabinets, so I’m very close to being there and want to get this done.
If everything ends up working out, I have an extra woofer and an extra midbass for each speaker, making them a WMTMW, but in a four-way format.
Thank you very much
Dan
The original speakers that most of these drivers were pulled from the large horn crossed to the 10 inch driver at 800 Hz. Since I’m using that same passive crossover for the top end, I plan on doing the same. I figure I will have the 15 inch woofer play down to maybe 40 Hz or so. At least for movies, I could potentially go a bit lower for music. They will be crossed to a pair of 24 inch subwoofers at that point as I don’t want to put too much stress on the 15s. I am still trying to decide where to cross the 15 to the 10. Maybe 200 Hz? 250 Hz? At that point, the 15 will be playing a fairly small bandwidth, but that’s okay. When I mostly wanting from the mid bass and woofer is to get tons of impact, while at the same time getting the highest fidelity. I am guessing that the tens would have the best transient response seen as they have the least amount of mass to control the given motor strength.
Here is some information on the drivers: the 15s are the 1500 sub drivers sold by PE awhile back. The same driver used in the Revel Ultima sub. From what I understand it is quite similar to the W1500H. I know it may not be exact, but I’m thinking I want to go all sealed cabinets to keep cabinet volume down plus, I don’t want multiple tunings in the same room if I port the 24s. I know they have been used with success in sealed cabinets ranging from 2 to 2.5 cubic feet. Some of gone slightly smaller, and some have gone slightly larger. I figure if I have DSP and realistically, I am only running them down to maybe 30 Hz listening to music I can get away with not going huge.
15” woofer
https://www.audioheritage.org/vbulletin/showthread.php?7113-Project-Array#9
10” 251J
https://www.audioheritage.org/vbulletin/showthread.php?11985-251J
These are some parameters of the drivers.
What would you all do for the 10s. If I cross them as high as 200-300 hz I really don’t have to go all that large. Plus the original cabinets weren’t all that big, I was thinking maybe 1 cubic foot sealed? Maybe a little larger and crossing lower to the 15, I am wanting heavy impact in the chest.
I asked this question quite a while back on Audio karma, but I now have the test cabinets for the woofers built, and I want to start the test cabinets for the midbasses. Of course the other two drivers won’t need cabinets, so I’m very close to being there and want to get this done.
If everything ends up working out, I have an extra woofer and an extra midbass for each speaker, making them a WMTMW, but in a four-way format.
Thank you very much
Dan
Nice set of drivers. Standard JBL large format 4 way 15/10/CD Horn/Tweeter 250-300Hz 1200-1500 8-10K. If you are using the passive crossover on the 9800 that's going to define the mid or woofer crossover point to 800Hz.
Rob 🙂
Rob 🙂
Well, the pioneers chose based on matching polar responses for max efficiency/integration over distance, so in the link is an example I did using the driver's theoretical pistonic BWs (Fs - Vc diameter, must be signed in to see specs):
https://www.diyaudio.com/community/...chn-40-driver-for-top-end.413838/post-7709803
In general though, historically we want either the analog (250-2500 Hz) or digital phone's BW (300- 3000 Hz) 'billiard table flat', though in much later years Altec backed them down to 500 Hz, so your call with this interactive chart to guide you.
https://www.diyaudio.com/community/...chn-40-driver-for-top-end.413838/post-7709803
In general though, historically we want either the analog (250-2500 Hz) or digital phone's BW (300- 3000 Hz) 'billiard table flat', though in much later years Altec backed them down to 500 Hz, so your call with this interactive chart to guide you.
Thank you very much, so that cements my decision on going with the 800hz. I want to say that the passive crosses the tweeter at about 10 kHz so that seems in line with what you said. Obviously, the 10 is going to be cross a little lower than the 1200 hz point at 800 hz, but looks like I was right and around the proper point for the 15-10 crossover point of 200-300.
Do you have an opinion on how big I should make the cabinet for the 10? And alignment I guess, but I’m thinking that going sealed is probably the way to go. I don’t know what porting a cabinet for a driver that’s running 250-800hz is going to do for me.
Dan
Thank you, once I get the test cabinets finished and can get some measurement equipment setup I know the crossover points will be adjusted, but your response led me to another question. Seeing as I’m going active I have the ability to cross at different slopes. Would 4th order be the way to go? I’m thinking that especially if I go with a WMTMW arrangement it would help with any comb filtering by crossing steeper. I did the math and the center to center spacing on the two 10s with the horns between them is like dead on with the 800 hz crossover point. So potentially could be an issue to overcome. I think I can possibly even cross steeper.
Dan
I used .5 cubic ft on my 2123's and if you look at he 4348 with a very similar driver to yours it's the same. Yours were used in pairs in vented enclosure no? Do you have the T/S for them? JBL also ran a pair of 2123's reflex as well. I would go with .5 sealed and see what you get.
4348 very similar to what you want to do.
Rob 🙂
https://www.audioheritage.org/vbulletin/showthread.php?17053-4348
Awesome!!!! Thank you so much. That indeed looks quite similar to what I am wanting to do. I will go with 1/2 cubic foot.
They were indeed originally used in a bass reflex and there were two of them. I forget the exact frequencies, but one of the drivers was crosses at like 120 hz while only one was allowed to meet up with the horn.
Here is the info I have on the 251J.
My other option is to do an exact clone of the K2-9800. It uses the same horns and compression drivers I have, but then I wouldn’t be able to use the tens. Also, I would have to find a third 1500AL-1 woofer in order to make a center. Otherwise I guess I could use the 1500ALs I have on the two mains for music and then just use one of the sub1500s I have for the 15” driver on the center. I’ve been going over that in my head for a while, but I think my initial decision would be better overall for home theater probably.
Dan
You're welcome!
4th is for high power apps with a 360 deg/1.0 Hz offset, but technically not the way to go for HIFI/HT and personally use(d) the pioneer's 1st order that I consider required to 'eek out' an H.E. system's potential resolution, closest to 'Is it live or is it Memorex' 😉.
WRT ctc spacing, was the JBL designed for studio or PA apps? IOW the baffle's polar response becomes much more important as 'throw' shrinks and here's where the pioneer's 1st order choice comes into play, which also can include adding some form of acoustical shaping/damping horn extension(s) for best overall blending Vs their ability to design/build horn profiles to suit specific apps.
If I am going to be crossing the 10 inch midbass around the same frequencies as they are, should it be mounted to a wide baffle? Like roughly as wide as the 15 inch cabinet? I plan to just make a small half cubic foot cabinet, but I can attach a white baffle to the front. I’m just not sure if frequencies that high will benefit from that.
Dan
Dan
Movies go a lot deeper than music. And you need a low-cut, especially for the movies or records.
I suggest to use 2 or more ports, that way you can close one or more of them for subsequently deeper tuning.
Right, movies go quite a bit deeper than movies which is why I said I would have the 15s go to maybe about 40 hz and then let the 24” subs take care of anything below that. I figured I could go lower with the 15s in music and turn the 24s off for music as music doesn’t have 15-20hz explosions in it that can kill the woofer. Well maybe the 1812 overture.
If I port anything, it would be the 24 inch subwoofers, and I’ve read that it can be a real headache having cabinets in the same room with multiple tuning frequencies.
Dan
If they have multiple different tuning frequencies at the same time (bp6, multi-chamber br etc), then yes but not if you move the tuning frequency by closing off identical ports. By reducing the port surface you are just lowering the tuning frequency.
What I meant by that was let’s say I have the 24 inch cabinets tuned to 15-18Hz and then tune the 15s to 25-27hz. by having them both ported at the same time I would run into issues correct? But in theory I could just block the ports on the fifteens and then the issue goes away. But what would the benefit be of having both the 24s and the 15s both ported and tuned to different frequencies? Another thing that I am accomplishing by keeping the 15s sealed is keeping the volume of the cabinet down. I figure if I sealed I would have them in roughly 2 1/2 ft.³ or so. if I went ported, I would have to jump that up to probably 4 plus the volume taken by the ports.
As I mentioned earlier, if this works out, I’m going to have the midbasses and woofer about in a WMTMW type of arrangement, like this
So far the plan is that the upper cabinets would be supported by 1 inch all thread, nuts and washers. Realistically, the smaller the cabinet the better. There will be 6 of these 15 inch woofers in total up front. Do you think ported is the best way to go? Revel used it in a smaller sealed alignment. I’m not completely against it, but the benefits would have to greatly outweigh the sealed for me to go that route.
Dan
I had not found the parameters of the driver and wasn't sure which one it exactly is. It's not a bass, it's a subwoofer driver. If you want to use them with the bigger subwoofers, build their enclosure sealed, that makes it a lot easier to create a DSP setup because it doesn't have the strong phase shift. Sealed will also have a lower group delay and will sound cleaner, so it's indeed a lot more promising.
