I've been given 12 of some B&C 10" woofers that came out of a d&b line array. Attached is the impedance plot of one. Would you call it 12 or 16 ohm? Currently my best option is a TMM 2.5-way. I want to know if it's possible to do a TMMM 2.5 way, where the 2 drivers that are in series is the .5. I'm fairly confident in the wiring here, my concern is won't the .5 section only be taking 1/3 of the power due to its higher impedance, which sort of diminishes the whole point of doing a 2.5? These drivers have a sensitivity somewhere around 97dB but won't get any lower than 80Hz or so. I just think having more surface area would be more fun if I can do it (they were free after all) and also help with bass extension. Secondly, am I missing anything with getting more LF extension? I can't afford the size/power sub that would be needed to make them a 3-way.
Since they're so sensitive I don't think want the impedance lower than 8ohms, unless I'm missing something there.
I need the horns on top for this build so please don't suggest a MTM.
FYI I already have some Selenium D220Ti. Didn't want to break the bank on some free woofers.
PS - I tried modeling some passive radiators but vents looked quite a bit better.
Since they're so sensitive I don't think want the impedance lower than 8ohms, unless I'm missing something there.
I need the horns on top for this build so please don't suggest a MTM.
FYI I already have some Selenium D220Ti. Didn't want to break the bank on some free woofers.
PS - I tried modeling some passive radiators but vents looked quite a bit better.
Attachments
DCR looks around 12 ohms, but nominally "8 ohm" speakers have DCR's in the 6 ohm range. Certainly most competent amplifiers will not struggle with the load of the pair in parallel.
As far as I know, you've stated you have:
2x Selenium D220TI in some sort of horn
12x B&C 10"
Before getting ahead of ourselves on topology, what's the end-goal? Will this be an active setup? What are the volume constraints? There's a lot of things that could potentially be done here, depending on what sort of goals/objectives you're aiming for.
As far as I know, you've stated you have:
2x Selenium D220TI in some sort of horn
12x B&C 10"
Before getting ahead of ourselves on topology, what's the end-goal? Will this be an active setup? What are the volume constraints? There's a lot of things that could potentially be done here, depending on what sort of goals/objectives you're aiming for.
Correct on what drivers I have. Goals are vague at best (SMH). Big, open sound, with plenty of headroom. Passive for sure. Might replace some ribbon tweeter bookshelves that aren't filling my living space. Or maybe they'll replace my POS Polk towers. Certainly I favor fidelity over power or whatever, these can probably be a small PA, but will stay inside. Maybe they'll just be an experiment and I'll destroy the evidence when the build is done. Who knows (Yes, I know that makes the design process more difficult).
Okay, so you have WAY more oomph in drivers than you should really need, but that's a better problem to have than the alternative. And frames your ideas better as well.
A 2.5 way TMM would certainly let you rock the house. Mating the 10" to the tweeter/horn will require a relatively low xover, which might be ultimately close to the baffle step anyhow. I haven't plugged your woofers into a modeling to see what that gets you, but 2x10, even with an open air FS of 50-55 Hz, can be used in a low-low tuning alignment and have enough displacement to look at a bit of bass boost to compensate.
A 2.5 way TMM would certainly let you rock the house. Mating the 10" to the tweeter/horn will require a relatively low xover, which might be ultimately close to the baffle step anyhow. I haven't plugged your woofers into a modeling to see what that gets you, but 2x10, even with an open air FS of 50-55 Hz, can be used in a low-low tuning alignment and have enough displacement to look at a bit of bass boost to compensate.
The real question then-
So is a TMMM (note the 3 Ms) just a waste of time since the .5 section would have a higher impedance? Or will it actually contribute to the low end? I generally like how speakers with more surface area feel, but don't want to waste drivers if they're not going to ask for it from the amp. I guess what I'm getting at is is it possible to avoid a passive bass boost. I know the drivers can take it, but we all want the best sound before EQ is necessary.
So is a TMMM (note the 3 Ms) just a waste of time since the .5 section would have a higher impedance? Or will it actually contribute to the low end? I generally like how speakers with more surface area feel, but don't want to waste drivers if they're not going to ask for it from the amp. I guess what I'm getting at is is it possible to avoid a passive bass boost. I know the drivers can take it, but we all want the best sound before EQ is necessary.
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With active, I could see making a case for said speakers, or, some sort of dipole loading (if you're placing them far enough into the room). It'll be REALLY awkward getting the balance right to have some sort of (tm)(mm) with the latter coming in as baffle step.
Similarly, you *could* try some form of bandpass/tqwtp alignment as sub(ish), too, that come in lower. I mean you do have 12 of 'em.
Similarly, you *could* try some form of bandpass/tqwtp alignment as sub(ish), too, that come in lower. I mean you do have 12 of 'em.
It seems odd to cry poor when you have all these surplus drivers
You could sell some of them, and use the money for parts for make a 3-way.
OR
Using a couple of assumptions:
1) You need the midbass section to be ~80cm tall to get the horn to ear height, so an enclosure volume of about 100 litres seems reasonable.
2) The drivers probably have a VAS of only 25-30 litres (the other B&C 10" drivers have values in that region). You'll be able to pack a lot of these into a 100 litre cabinet.
...so why not make a 2.5 way using five of the 10" woofers per cabinet?
- one 10" (nominally 16 ohm) running as a midbass, up to ~1.5kHz
parallel that with:
- four x 10" (in series-parallel, nominally 16 ohm), bass only.
That'd give you a 'normal' nominal 8 ohm load. The crossover on the bass quad could possibly be as simple as one humungous inductor.
You wouldn't have to mount the 5 drivers woofers on the front panel. The bass quad (or half of it) could go onto the sides.
These are used, but in VERY good health from what I have measured. I am connected to d&b through my career in live sound and they are fairly protective of who gets their stuff so I don't want to mess with our relationship. But man, it's tempting cause this stuff is expensive!
I prefer HF a little higher, but yes, you're right, I've got lots of room here to play with.
I get the concept, and I like it. But what am I missing with getting 4x16ohm woofers into an 8ohm load? I end up with 8(P)+8(P)=16, 32(S)+32(S)=16, or all parallel at 4Ohm.
Ya, unfortunately I have only poor speaker locations available and I'm concerned that proximity to the walls would very negatively impact any sort of dipole. Am I thinking about that correctly? Plus, in general, forward facing I think is safer in unforgiving environments.
I was thinking something similar in terms of dipoles, Hollowboy.
Do think this requires some active to leverage the extra surface area down low.
I'm on my phone, G, so I'll dig up some material soon. Look up tapered quarter wave pipes. They're yet another helmholz resonator.
Ahhh, I see. What software can do these calculations? Or do I need to break out the calculator? I'm familiar with bass box, Jeff Bagby's stuff, and WinISD (a little) as far as predictions go.
I was assuming a passive crossover. If you're using active, then yea, it makes no sense.
If you go passive with a simple 1st order passive crossover, then:
Midbass is a small inductor in series with a ~16ohm woofer.
...if you ran this in isolation, the DC resistance would be about 12ohm (16ohm nominal).
Bass is a huge inductor, then 4 woofers (A, B, C and D) arranged in series-parallel, so the signal can go through:
A-and-B (32ohm nominal)
OR
C-and-D (32ohm nominal)
...if you ran this in isolation, the DC resistance would be about 12ohm (16ohm nominal).
If the midbass and bass were run from a single amp (in parallel), the DC resistance would be about 6ohm (8ohm nominal, i.e. "normal").
I'm no expert, so take this with a grain of salt:
- In a sealed or ported box, putting LF drivers on 3 faces would still be a monopole, not a dipole (you'd get an omni bass pattern, not figure 8).
- slot loaded 12" woofers are supposed to be fine up to about 300Hz (according to people who build PPSL boxes), so as long as the wall clearance on your (bass only) speakers was bigger than a PPSL plenum, I think you'd be OK.
The developer of hornresp is a wonderful gentleman who frequents this site regularly: David McBean
You can find him here: Hornresp
His software is great for just this purpose.
My reservation about TM(M^4) is how low that BSC is likely to be, where having an active + passive would bypass that monstrosity. But bigger things have been done passive than this.
Ok, I read this when I was way too tired last night. This makes perfect sense now, I just wasn't thinking straight. Also whiskey. . . .
Ya, I just don't think I can convince my wife of it
I was just looking at this. Looks great, thanks!
What's wrong with having a low BSC? You mean just because thats the region I'm concerned about to begin with? Also, having an active also I'm assuming would have to be a different driver since these just don't get down there. FWIW these may end up in my HT setup which obviously has an active sub already. I need to build new surrounds anyway. Might as well just take over my shop for this
A low bsc (or rolling in the additional woofers I should say) will require a big inductor, the kind that may be pricey. The second reservation about using 4 woofers in the .5 section is that they will need to be resistively padded down to match the top, killing a big portion of the advantage. Third, active would give us better access to bass boost to leverage that huge displacement.
I realize that adds a couple layers of complexity, so feel free to ignore it!
I realize that adds a couple layers of complexity, so feel free to ignore it!
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