AVS Forum banner
1 - 20 of 125 Posts

·
Registered
Joined
·
230 Posts
Discussion Starter · #1 ·
I know most would recommend a longer throw driver for HT but I cant help but wonder what an 18 from B&C like the 18TBX100 would be like if tuned for mid to high 20's. Basically a clone of designs from Pro Audio Technology etc. or QSC cinema subs. The goal being 20hz and up efficiency vs 20hz below infrasonics. Not trying to debate which is better. What ported or sealed sub box would work best for a driver like the 18tbx100 ? The big 21 inchers would be "neat" but out of budget. The interview on home theatre geeks with Paul Hales was interesting mentioning the design goals of his subs (low vs ultra low) again Im not trying to start debate, just would like to get some design ideas.
 

·
Banned
Joined
·
15,491 Posts
I know most would recommend a longer throw driver for HT but I cant help but wonder what an 18 from B&C like the 18TBX100 would be like if tuned for mid to high 20's. .
It's not going to work as well as a driver designed to work into the mid 20s, from both the standpoint of Fs, Qes and xmax. Like most pro-sound drivers it's designed to give maximum sensitivity, at the cost of low end extension.
 

·
Registered
Joined
·
927 Posts
I'm going to build a (dual) 20x21x23 sealed sub with the BMS 18N862 - 4 ohms
I'm from Europe and i can get the BMS locally at a cheaper price than i would get an UXL and much cheaper than i would get an HST, so i decided to go with the BMS.
Unfortunately, i'm waiting for a friend to have the availability to build my box. :(:(:(

I will start with one powered by an Inuke 6000 and will add another until the end of the year.

When i have the box build, i will start a thread with the details of the build.
 

·
Banned
Joined
·
15,491 Posts
mmmmhh JBL 2269H ?
The 2269 Fs is 28Hz, so it will go lower than the average pro 18. Still, in a maximally flat alignment f3 is 32Hz, and to go that low sensitivity is only 95dB/2/83v. It wouldn't be my choice for HT use. It's fine for a 'real' theater, but they don't care about going much below 30Hz.
 

·
Banned
Joined
·
15,491 Posts
maybe you didn't mean to say what you just said. :) as you know, how low a sub will "go" is a function of enclosure tuning and excursion limits (and in some small sealed cases power handling).
I meant exactly what I said. The 2269 will go lower than the average pro-sound eighteen, and not the least bit coincidentally it has a lower Fs than the average pro-sound eighteen. Of course the other specs enter into the overall equation, but where f3 is concerned in pro-sound Fs rules supreme. True you can go with higher Qts to give lower f3, but when you do so you lose sensitivity and the ability to use a ported or horn enclosure, and that takes the driver out of the pro-sound realm.
 

·
Registered
Joined
·
21,345 Posts
I meant exactly what I said. The 2269 will go lower than the average pro-sound eighteen, and not the least bit coincidentally it has a lower Fs than the average pro-sound eighteen.
how low a driver "goes" is a function of its excursion limits not its fs. you know that. there are drivers with compliant suspensions and very low fs that don't have very much excursion (the mfw15 comes to mind). there are drivers with powerful motors, tight suspension, and relatively high excursion (aa mayhem 18 comes to mind). the latter will "go lower" than the former. it isn't even close.
 

·
Banned
Joined
·
15,491 Posts
how low a driver "goes" is a function of its excursion limits not its fs.
Xmax determines how loud a driver will go, not how low.
the 2242h is quite similar to the 18tbw100 (high fs pro driver). Nichol tuned his to 22hz and got great results.
No matter how large the box is the 2242H with 22Hz tuning will have an f3 no lower than 90Hz. Model it and see for yourself. If you go all the way to 20 cu ft to realize a combination LLT/extended bass shelf alignment the lows aren't bad, -5dB at 22Hz, and with cabin gain it can work well. But 20 cu ft is a mighty large box, and with displacement limiting max SPL at 30Hz to 115dB it can be equaled or beat below 50Hz by many much less expensive consumer grade drivers in much smaller cabs, the Dayton RSS460HO in 8 cu ft, to name just one.
 
  • Like
Reactions: Billy Boden

·
Registered
Joined
·
4,816 Posts
Cowan did a 250l 22hz ported cabinet with the 18 Sound 18LW1400 driver and while it has a small Xmax he was able to do 20hz and everything up just fine. And with a pro audio driver he reaped the benefits of the better technology and specs to simulate. Also Josh Ricci did a large 25hz ported cabinet with the BC 21SW152 and it does 20hz also just fine. :D So it can be done.

I knew about inductance before but never saw it on a simulation what it does. So I am sticking with driver from pro audio or drivers that Ricci has already tested. Just my 2cents sorry.
 

·
Banned
Joined
·
15,491 Posts
Cowan did a 250l 22hz ported cabinet with the 18 Sound 18LW1400 driver and while it has a small Xmax he was able to do 20hz and everything up just fine. And with a pro audio driver he reaped the benefits of the better technology and specs to simulate. Also Josh Ricci did a large 25hz ported cabinet with the BC 21SW152 and it does 20hz also just fine. :D So it can be done.
Of course it can be done. You can drive a square peg into a round hole too, provided you use a large enough hammer. I'd rather use a round peg. ;)

When I choose a driver for a project I run it through a modeling program using the alignment that the program defaults to, as that's the alignment that the driver specs work best with. If the result is close to what I want to realize vis-a-vis box size, response, sensitivity and maximum SPL then I'll tweak it to get exactly what I want. If it's not even close I move on to a different driver, simple as that. There are so many driver choices available that there's no need to jump through alignment jamming hoops trying to get a driver to do what the designer never intended it to do.
 

·
Registered
Joined
·
15,396 Posts
Of course it can be done. You can drive a square peg into a round hole too, provided you use a large enough hammer. I'd rather use a round peg. ;)
Only if you start with the assumption that the diagonal of the square peg is larger than the diameter of the round hole.

When I choose a driver for a project I run it through a modeling program using the alignment that the program defaults to, as that's the alignment that the driver specs work best with. If the result is close to what I want to realize vis-a-vis box size, response, sensitivity and maximum SPL then I'll tweak it to get exactly what I want. If it's not even close I move on to a different driver, simple as that. There are so many driver choices available that there's no need to jump through alignment jamming hoops trying to get a driver to do what the designer never intended it to do.
And by jumping through hoops you mean enlarging the box a little and moving the tuning point of the port lower? You're right. That sounds awfully difficult compared to the joys of using a smaller diameter, high inductance, long throw driver. ;)
 

·
Registered
Joined
·
1,416 Posts
When I choose a driver for a project I run it through a modeling program using the alignment that the program defaults to, as that's the alignment that the driver specs work best with. If the result is close to what I want to realize vis-a-vis box size, response, sensitivity and maximum SPL then I'll tweak it to get exactly what I want. If it's not even close I move on to a different driver, simple as that. There are so many driver choices available that there's no need to jump through alignment jamming hoops trying to get a driver to do what the designer never intended it to do.
There is no program default, most of the programs don't even have pre-defined alignments at all. Even WinISD has several options, YOU are the one choosing the max flat option, and that is an arbitrary choice, the max flat version isn't "better" than the other options, it's just different. As others have been trying to tell you, the lowest possible F3 is not the "best" option, in fact it's usually a terrible choice.

This sounds a lot like what beginners do the first time they fire up WinISD - choose max flat response and assume it's the best they can get. More experienced users will use a better program than WinISD, and they will shoot for a response curve that complements their room gain curve.
 
1 - 20 of 125 Posts
Top