Hello fellow hifi fanatics and tinkerers.
I've found myself yet again needing to build cabs from scratch for a set of dual concentric drivers that I like the mid-bass, mids and highs of.
I picked up a pair of Tannoy CMS 1201 DCT 12" dual concentrics, brand new, paper cone with very stiff suspension, 1.34" aluminum dome firing through the hole in the woofer with a phase plug.
The driver model # is 1276 and there seems NO info or specs on this at all, except that the manufacturer rates the -3 db for the woofer at 60 hz, that's presumably mounted in their 2.9 cf ported back can which I do not have.
So my first thought was to build large cabs around 5 cf and see how low they can go, but with a little bit of researching I've found that the predecessor to my ceiling speakers are CMS 12/8 and apparently their woofer fs is around 60 hz, so no point really trying to get any low bass out of these. This is that thread:
https://www.diyaudio.com/forums/full-range/274222-12-tannoy-paper-coax-box-type-karlsonator.html
I've sorta settled on using a 15" helper woofer at this point.
My main question is: If I use one Dayton PA380 per cab at 93 db efficiency, passively low-passed, will the speakers still be 'easy to drive' and can a small amp or tube amp still power them with ease like right now?
The CMS 1201 are 97 db efficient, so close enough to the Dayton PA 380's 93 db. I'm worried that passively low passing the helper woofer, say around 150 hz or so, will introduce a phase cancellation around the crossover point. Is that possible to avoid without an electronic crossover and bi-amping?
The goal is a simple tower speaker that can be driven by a single amp. I will experiment with super tweeters sat on top of the cabs as well, because the Tannoy dome rolls off gently above 10 - 12k and has nothing at all above 16k.
Thanks for any input!
I appreciate it.
PS I preliminarily chose the Dayton PA 380 because it is cheap enough, can get down to 40 hz in about 3 cf and is efficient enough. I'm open to suggestions that won't break the bank.
I've found myself yet again needing to build cabs from scratch for a set of dual concentric drivers that I like the mid-bass, mids and highs of.
I picked up a pair of Tannoy CMS 1201 DCT 12" dual concentrics, brand new, paper cone with very stiff suspension, 1.34" aluminum dome firing through the hole in the woofer with a phase plug.
The driver model # is 1276 and there seems NO info or specs on this at all, except that the manufacturer rates the -3 db for the woofer at 60 hz, that's presumably mounted in their 2.9 cf ported back can which I do not have.
So my first thought was to build large cabs around 5 cf and see how low they can go, but with a little bit of researching I've found that the predecessor to my ceiling speakers are CMS 12/8 and apparently their woofer fs is around 60 hz, so no point really trying to get any low bass out of these. This is that thread:
https://www.diyaudio.com/forums/full-range/274222-12-tannoy-paper-coax-box-type-karlsonator.html
I've sorta settled on using a 15" helper woofer at this point.
My main question is: If I use one Dayton PA380 per cab at 93 db efficiency, passively low-passed, will the speakers still be 'easy to drive' and can a small amp or tube amp still power them with ease like right now?
The CMS 1201 are 97 db efficient, so close enough to the Dayton PA 380's 93 db. I'm worried that passively low passing the helper woofer, say around 150 hz or so, will introduce a phase cancellation around the crossover point. Is that possible to avoid without an electronic crossover and bi-amping?
The goal is a simple tower speaker that can be driven by a single amp. I will experiment with super tweeters sat on top of the cabs as well, because the Tannoy dome rolls off gently above 10 - 12k and has nothing at all above 16k.
Thanks for any input!
I appreciate it.
PS I preliminarily chose the Dayton PA 380 because it is cheap enough, can get down to 40 hz in about 3 cf and is efficient enough. I'm open to suggestions that won't break the bank.
Forgot to mention that I want the 15" helper woofer to be down firing, as to be invisible. The only thing showing on the front of the large tower should be the 12" Tannoy, and the super tweeter on top.
The 15" woofer being down firing, does that help any at all with the crossover, or phase issues around the cross over point?
In theory it should at least help with voices and too much mids coming out of the woofer.
The 15" woofer being down firing, does that help any at all with the crossover, or phase issues around the cross over point?
In theory it should at least help with voices and too much mids coming out of the woofer.
I believe this is the same driver i am looking to score (in a set of T12). I have found that trying to get decent bass out of a Tannoy — even the big ones — requires an ugly alignment if you are doing a reflex box, so adding a woofer is a really good idea. As well as real bass, it should improve the midrange (and the top if the moving cone is disturbing the tweeter).
ir you want to do a passive XO you really need a woofer that is 3-6 dB more sensitive than the midbass.
But crossing as low as you should (i’d suggest 150-200 Hz as a start) you will quickly find that going active (ie 2 amps) could be cheaper, and certainly WAY easier to get right than trying to design a passive.
dave
That's too bad, I don't think I am willing to spend that kind of money on this project. I was trying for an affordable, passive tower with 15" woofer. Ultimately, I regret selling my Ashly electronic xo and several power amps recently. All of which would've helped with this project.
So in an effort to keep this a simple, passive tower speaker that can be driven with a single amp, what are my options?
Two 15" Daytons in each cab would add 3 db efficiency over only one per, and only add $300 ish. Is that an idea?
What about the passive crossover is the difficulty? Price, or performance / phase issues?
Thanks for explaining.
What we are saying is that going active could be cheaper (& faster) than trying to do a passive. Look at the size of parts you need if you want to try to cross that low. Decent parts are scary. 5-10mH chokes (or larger), 100-400 uF caps.
You could start with a PLLXO for XO duty ($<<20 if you don’t do a fancy case), and a decent Class D amp for the woofer can be built amazingly cheap. 1 have 2 4x100w 4Ω amps, one cost less than $100 to build, the other has a buffered PLLXO built in, it cost $200.
It also solves the big issue with finding a woofer sensitive enuff to do a passive without heavily padding the Tannoy (not something you like to do with a driver being used that low).
dave
Snap, that really puts it into perspective, thank you.
I love going active and biamping, don't have to convince me that it's superior, it's just that unfortunately I let go of all that equipment.
If it's not feasible to execute as planned, a tower able to be powered by the average integrated, even tube amp on occasion, then I will change plans and build small monitors with these drivers instead that will serve fine in a small size room. Such a monitor, as long as it reaches down to 60 hz, plus room gain in a really small room should still be a fun speaker to keep in the rotation.
Just for giggles though, roughly what components would I need to build a passive for the low pass section of a 15" 8 ohm Dayton around 150 hz? Just a single inductor and cap enough? Electrolytic caps are cheap, even large ones, so the real expense is a huge choke?
Dayton Audio PA380-8 15" Pro Woofer
So I can at least ball park the expensive of building that passive low-pass.
Can I get away with NOT high passing the Tannoy if I keep it in a separate small sealed enclosure within that tower? And the 15 is down firing.
THANKS!
Something like that?
Dayton Audio 10mH 18 AWG Perfect Layer Inductor Crossover Coil
400uF 100V Electrolytic Non-Polarized Crossover Capacitor
Totalling about $30 per cab. Or am I way off?
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Gotcha.
The 18ga 10.0 mh inductor has a DCR of 2 Ohms, the 15 ga version only 1.2 Ohms. But it's triple the price, putting me dangerously close to buying subwoofer plate amps to power each 15" woofer. A decent 250 - 300 Watt plate amp is around $140 + depending on sales, sometimes even lower.
Regarding the passive low-pass around 200 hz, would it be a simple 2nd order?
Can the 12" Tannoy driver be high-passed simply by virtue of being mounted in a small sealed enclosure? (I'm sure there's a technical term for that)
What kind of crossover would be needed for the drivers to be phase coherent to avoid a suck out of bass near the xo point?
The impedance correction you mention, could it be as simple as a parallel resistor, or does it have to be complicated?
If I did cross the woofer over passively, I would use an electrolytic cap as it's not in the signal path and only on a woofer playing 200 hz and down. I can't afford to be an idealist there.
If building passives costs anywhere near half as much as a pair of plate amps, it's a no brainer to go active. The plate amps would just have to have high level inputs as to not complicate setup all too much, so the only inconvenience at that point would be one power cord per tower speaker.
Thanks for your input!
I used to have a pair of NHT SuperTwo towers, and one of the things that bothered me very much is that there was a 15 db suck out of bass near the xo point ( 115 hz or so ) between the down firing sub and the front firing mid. Certain bass notes would just be missing out of the program, I couldn't stand it. I want to avoid that.
Still probably too high.
Now you are starting to get it :^)
With a subwoofer amp that is pretty much how you have to do it. XO will be wherever a Q=0.707 sealed box has its F(-3).
It will probably be an RCL shunting the driver.
i don’t think that anything in the XO is not in the signal path. And certainly the big cap on the Tannoy will be directly in series.
and only on a woofer playing 200 hz and down. I can't afford to be an idealist there.
It likely is. Especially since you are not likely to get a passive right on the 1st pass.
You don’t need a high level input (althou if you have a set of variable level pre-amp outs line level is preferable). The subs i have in my living room most often get hooked up with speaker wires coming off the mains terminals.
dave
You'd have to be certain that it wasn't the room or some reflection interference rather than loudspeaker. Have you measured any other loudspeaker at that same speaker and mic position ?
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Well it is settled then, either plate amps for the woofers, or build small monitors with these drivers.
In the tower with helper woofer version, how do I calculate whether or not the Tannoy driver needs to be high-passed, or if it's sufficient that it would be mounted in a small sealed enclosure? You mentioned a series cap for the Tannoy, are you saying it would have to be high-passed?
I'll see what i can do about assessment of crossover components needed to cross woofer around 150Hz as soon as i get to my computer (in an hour or two). Drivers are pistonic down low so it should be quite close to actual values needed.
Why wouldn't you want to mount he woofer below the dual-concentric ? Aesthetics or some other reason ?
Why wouldn't you want to mount he woofer below the dual-concentric ? Aesthetics or some other reason ?
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