12" or 15" tops, with 100Hz subs? (live sound)

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You realise these dispersion angles happen over a couple of octaves at best, right?
Above 10kHz or so, you get beaming since the HF exit diameter is fairly large. Below a couple of kHz, most horns are too small to effectively control the dispersion.

Time to look at Synergy horns...

Chris


Yeah, I've read this recently, and good to know.

But I don't see how that changes things. Why else would manufacturers purposely control the vertical spread with "normal" horns? Even Tannoy has started doing this on the newest dual concentric designs.

Well, I dunno. Still on the fence. As I said before, those 90º conical T300's worked great, sounded incredible at the back of the room, so ......
 
BUT I WANT TO GET BACK THE THE ACTUAL THREAD TOPIC, FOR A MOMENT:

If anyone is still reading this, I have more thoughts about that "slightly anemic" sound my old system had in the low mids..

I've been thinking about 12's vs 15's again, AND -

I've been thinking about something Art Welter wrote, concerning PPSL and energy ABOVE 100 Hz. This has really puzzled me, but now I'm thinking about a speakers output passed the system crossover point. This is probably standard stuff for you guys, but new thinking for me. The first octave or two "on the other side" of the crossover is obviously important. (Slapping myself upside the head, with a loud "DUH," then seeing the lightbulb come on..... :eek:)

My old system was the T300's, with four sealed 18" Bag Ends. Crossed at 120 Hz.

The T300's are -3dB at 55Hz, with the dedicated processor.
OK, that seems about right, but the 12" cones in these coaxial speakers are more like 11", due to the large HF unit in the center. Could it be that the sub-crossover octave of 50 - 100 Hz doesn't carry well into the room?

OR: Could it be that the sealed 18's don't have enough energy above 120 Hz? (I know sealed cabinets have a natural high-end roll off.)
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If the above is correct, the solution would be to use corrective EQ, yes?
- But wouldn't it then be best to do this on only the tops, or on the subs?

With my new top speakers, (yet to be decided on, but most likely 12" mids ) I'll have to use my own electronics, probably likely a top-end DriveRack. The DriveRack will give me separate EQ control for both subs and tops (or all three drivers if I forgo any passive x-over) so I will then have the ability to do as above.

So - Is this the solution? Would pushing a little extra Eq at 80 Hz or so to the tops, while crossed over at 100 Hz, help the crossover point sound more substantial, or would I still have losses out in the room, or maybe even just be adding mud?

Is the answer simply more mid drivers (a dual 12", for instance) or - getting back to the main subject - using 15's instead of 12's?
 
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can a "lens" be of use sometimes with larger cones? - like recent JBL, "BBC" or oval ? - it can make things rougher

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First port of call would be if you haven't already is to stick a mic in front of a stack, preferably 5m or more if possible from any boundaries and measure the response with REW, Holm, Arta or similar to see what is going on before binning the existing tops?

I did this toady, even though the HF is distorting a little. (Dues to the boxes being dropped,and the huge magnets shifting.)

I understand now at least a bit of what's happening.
I set up my old rig as it always was, with the stock 120Hz crossover for the tops, and not LPF for the sealed 18's.

At three feet, I can get pretty even from 38 - 18K, as expected. However, at even 30 feet away, there is a noticeable drop from maybe 100Hz to 300 or 400Hz. It hard to measure exactly as at that distance all sorts of weird stuff happens before it gets to the mic, but the change is significant.

So evidently I was right to worry about the coaxial 12's lack of cone area. Even a normal 12" surely does this at distance. Gotta' move as many air molecules as you can, just like with subwoofers.
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I figured that I would have two solutons:

1: Go with 15's after all, despite the negatives you gusy have already mentioned.

2: Add a second (non coaxial) 12", as Tannoy is doing now with one of their VX speakers.

I spoke to Jeff at Radian today, and ran all this by him. (This guy appears to know his stuff. I'd love to get him and Art together, get 'em drunk & talking about speakers, and just sit back & record the whole thing. :) )

FWIW< here's what he told me:

Re 15's: Absolutely no good for me. Yes, there would be more cone area and thus better throw, but it has the beaming effect you guys talked about. He also mentioned their tests using their own Coaxials mounted on top of smallish subs, in order to simulate a typical "event D / "Bar Band" type of setup. No physical or electronic delay for the subs.

He said that the 15's required 30 feet to fully couple with the subs, whereas the 12's needed MUCH less distance. (He couldn't remember exactly. That's a big deal for me. I don't know if electronic delay would help with that or not, I didn't think to ask.
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So we move on to the "two 12" mid drivers" thing, but he feels there would be too much phase smear. (Although a number of good companies have speakers liek this, including Fulcrum and Tannoy. OK, Tannoy is now Behringer, :( but, well, Fulcrum.)

His suggestion, which kinda' blew me back, is to run my subs at least an octave higher, since they have a lot more cone area. In fact, I will probably be using a total of six 12" , or possibly even twelve 10", in my new PPSL subs (unless I build small TH's) so that's a LOT of cone area, lots of high-mid capability, and not a lot of total cone movement so pretty reasonable modular distortion.

What bothers me about this is that I've always felt subs sound best when crossed at 120Hz or lower. The lower you go, the punchier they sound.
I still think so based on the stuff I have hear, but that a very limited sample.
Dennis thinks that with todays technology and super-strong neo magnets, subs can deal with higher frequencies and not lose any punch.

Kinda' sounds like what Art's been trying to get me to understand all this time. I think. :confused:
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I am DYING to get some opinions on all this from you guys.
 
can you give more specific details about your setup it seems as though there's an overlap in the frequency range between sub and mid high that is cancelling the low mid area. it could be a polarity issue or you may need a crossover with a steeper slope.

+1 on that, reason I gave for measuring the system away from any boundaries is to see what the system is doing without the effect of the room, it will make it possible to set the xover between the lows and hi's much much more accurately, when yoy then take the system indoors you will be able to see what effect the room os having on the system. Where to place the mic is important.
Re the HF, have you dissasembled the HF drivers to check the diaphragms?
 
can you give more specific details about your setup it seems as though there's an overlap in the frequency range between sub and mid high that is cancelling the low mid area. it could be a polarity issue or you may need a crossover with a steeper slope.

That's an interesting possibility, although if true it would probably be an ADDITIONAL issue as well.

But if it's a phase issue, wouldn't I hear that at all distances?

Both of my electronics (tops & subs) have phase switches, and I definitely tried both ways long ago, and preferred in-phase. - But I was only listening for the sound of the subs. I'll give this a try when I have time again to set it all up. (and the neighbors are all at work. :) )
 
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