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MesajScris: Vin Noi 18, 2005 10:35 pm 
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:( dom. i'm hurt...

although the words anger management classes have been flitting through my head much of the day. life has been a touch challenging of late, i have a fresh dent in my van and what i strongly suspect to be a fractured metacarpel to testify to the fact that i am acting my shoe size and not my age. sigh. i'll make a mental note not to take anything you say personally...

:wink:

so yeah ceharden, the w bin thing has been modelled up around the rcf l12p530, which is a nice driver for sure but not probably what anyone else would want to use. by putting the 8" and 1" above it in the middle of the cab you sort of make space for the 12" magnet, but i can't make the w bin element horn fold get the expansion at the end without wasting cabinet space in the way the nca rgw 112 simply doesn't.

having sid that, i've just had an idea that might be worth sketching out a bit. very point sourcy too... imagine if you will a martin 215 mkIII turned on it's end and made trapezoidal. into the narrower ends now go 12" neo mbs for example. bang in the middle of the mouth and with a suitably innofensive rear profile is either a combined mid high horn like a danley unity or graeme centauri job, or just a mid and high horn stacked.

thing is, i've never been happy modelling dual driver horns in hornresp, especially like the martin where each driver has it's own first half of the horn.

james.


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MesajScris: Vin Noi 18, 2005 10:53 pm 
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@Nexus3.. Thanks for the assist in hosting.

What I wanted to show was mainly the low-mid. This is a fairly small design using a reasonable priced 12" driver. The bulk of the idea I borrowed from WG in Texas. He's using his from 80 to 300 above Labs and below a pair of B&C 8PE21's. I'm working up drawings in Autocad.

Jim


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MesajScris: Sâm Noi 19, 2005 1:22 am 
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james, ind.st scrie:
:( dom. i'm hurt...


Nothing personal. That's what I want in a cab. I can't help feeling my current mid tops are in someway responsible for me still being laid up with a bad back and chiropractor bills eating into the new drivers coffers...


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MesajScris: Sâm Noi 19, 2005 1:27 pm 
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strangely enough the thing that i was holding when my back went ping over the summer was... a mid cabinet. hmm... don't worry dom, i was laughing really and i always find you funny (4X1=4), although the fact that i can go from ecstatic to tearful several times per day at the moment suggests that i need to... well, something needs to happen anyway. funnily enough, my back has been a lot better since people have started helping carry stuff. but yeah, loudspeakers...

jimbo, looking interesting on the dual 12" front, but can we look to use a neo driver? like dom, i have kind of had my fill of heavy mid top cabs (the active mackies that avid av have are ludicrous, kind of like a baby opus at2000 but with 4 x 12" instead of 10", and of course the amplifiers and processing. three or four people required to safely lift into place, we do not want to go down this road!

what kind of horn/ horns are those 12"s on? are they bifurcated? what is bifurcated? haven't sketched out that martin inspired box yet.

james.


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MesajScris: Sâm Noi 19, 2005 11:01 pm 
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I need to learn how to use Autocad or similar to draw stuff. Given I do everything else on a PC it's odd I still go back to pencil, paper and a ruler to draw cab designs.

Anyway, I'd certainly be interested to see some sims/sketches of these 12" horn designs James and Jimbo. What horn lengths are you looking at? I haven't finished mine yet. My initial thought was a W-bin but rotated 90deg compared with the NoiseControl box. One of the advantages would be that you could design the driver rear chamber and the centre of the W to be removeable, solving driver access. Another is that you eliminate any nasty two-dimensional mitres. I might however find that it doesn't fit in the box!

The other option is to go with some kind of manifold loading like the Opus AT1000/2000. I've never had a good look behind the grill to see exactly how it's done but I'm guessing the entire cab is used as a big horn with the 10" firing in from the back/sides. It's certainly an alternative, then mount the mid/highs coaxially.

Edit: Seems the W bin will fit in a sensibly sized box. Can get up to 80cm horn length but the throat and first part of the flare could be a bit tricky to make. I'm not getting down to the 80Hz that some people are after tho. Best I've managed is f3@82Hz with two Kappa Pro 12's/SN12MB's. Using the SN12B gives more output but less low extension.


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MesajScris: Dum Noi 20, 2005 1:49 pm 
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i had followed the noise control orientation as opposed to the fitzy dr-esque layout because it was possible to eliminate parallel horn walls. whilst i admit that talking boxes when visiting their works was instrumental in forming this opinion, i do now heavily subscribe to the theory that a folded horn can be kept musical, truthful and useable into the hunreds of hertz by getting rounding corners and keeping the flare consistent in both axes.

i know you must have been busy at glade but i am surprised that you didn't see the at2000 on the origin stage which was missing it's grill. the 6.5" high mid driver has a small round throat with no phase plug on a gigantic, nearly conical horn which pretty much takes up the top half of the box. the four 10" drivers fire in at about 40" inclination from centre axis with a small ridged divider. in the top of the horn mouth for this double open clamshell is a gigantic compression driver on a stubby little horn.

i've been really getting into the idea of a point source arrangement consisting of concentrically mounted horns. the andrews designed tannoy iq tops have this down to a tee, the complexity of integrating a compression driver into a phase plug is probably far beyond the remit of this project though. i am finding it hard to juggle the shapes around in box shells without really having a better undestanding of the most appropriate high mid horn to be thinking about.

the high mid horn is possibly the least forgiving bit of this cab, it's size is going to dictate the layout and loading of the low mid section. tractrix horns are often employed at this frequency band, hornresp shows an almost linear phase response for this type of horn.

also, has anyone had much experience with the sn8mb? availability of the sn12mb pretty much means the 8" will be available from the same place, although other possible drivers include the b&c and we are looking at their compression drivers. a neo is desireable not just for weight, they are supposedly better for doing the 1.5-3k region than ferrites.

james.


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MesajScris: Dum Noi 20, 2005 4:38 pm 
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I did see that AT2000 on the origin stage and I have previously looked at them briefly before but at the time I didn't think to look to the back of the cabinet and see how the bass-mid horn worked.

I hadn't really thought about the parallel top and bottom walls of my w-bin. I guess that might become a problem at the upper end of the range it needs to cover.

You're right that the high-mid horn is the one which will convey most of the musical information and is the most important to get right. It'll also be the most noticable if it doesn't array properly. For arraying, I believe tractrix or conical are going to be the most likely candidates. Oblate spheroids are definitely worth considering. If we can find a good neo 8" that would be nice. I don't think the B&C ones are candidates for this. RCF do a closed back 6.5" I think but might be a bit more $$$ wise.

Point source would certainly be nice but not essential if it over-complicates things. Since you're most likely to listen to these cabs at a reasonable distance (ie not near-field) it's probably not a crucial design parameter.


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MesajScris: Dum Noi 20, 2005 6:05 pm 
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Hi, all - have been lurking and watching progress..... :wink:

The AT2000 is a perfect example of what lack of a phase plug can do - even though the mid is a 6.5" driver, it can only go to 1.6kHz, neccessitating the use of a 2" HF driver - a costly (and weighty) compromise. Whilst the small diameter throat can keep efficiency up, cancellations in the geometry limit the top end.

Also note that a phase plug cannot be made as an "accessory" to be appended if felt one is required, it must be an integral part of the horn design - a horn designed to work without a phase plug won't work with one stuck in there, and vise-versa.

I agree that the hi-mid horn will be the most critical - fortunately HF driver manufacturers have already done the hard work of throat/plug geometry.

To even start thinking about any designs, we really need to set a solid set of goals. I assume that the reason for comtemplating this project is that presently available designs (Rog's, Walt's etc) are lacking in some area. What is the general concensus of what is lacking? Is it proper arrayability? Is it weight? Size? Spl?

If arrayability is a prime concern, then we need to agree on an acceptable dispersion. The common angle of 60 degrees is, IMO, too wide for an arrayable box - two boxes at around 110 to 120 degrees coverage (assuming MINIMUM overlap for least combing) would be too wide for most indoor venues. For a stand-alone box, I like to get coverage at 90 degrees, 60 degrees being too restrictive in this case. Maybe aim for 45 degree segments with a coverage angle of 50 degrees - this should be achievable without too much problem, the narrower you go, the more difficult the design becomes.

So, probably the main questions at this point are:
What horizontal coverage do we need?
How high do we want the HF crossover point?
(I prefer it above 2.5kHz or higher)
How low do we want this box to go?

Lots of discussions here !!

Cheers
Graeme


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MesajScris: Dum Noi 20, 2005 6:44 pm 
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Hi Graeme, glad you're on the team! In terms of the questions at the end of your post, my take is as follows:

The main disadvantages with the other designs are: Many don't play much below 160-180Hz (MT122/102) which means that you end up with vocals in your bass bins (I'm interested in use for live work as well as dance events etc). The X-tro is a good design we can take inspiration from but is not suitable for arraying.

60deg is probably too wide, most people agree on that. Maybe 45deg is the way to go?

I'd also like to get the crossover up to 2.5kHz or even 3kHz to avoid crossing over within the vocal range.

In terms of how low, I'd like to go lower than the Porns/MT122/102 but reaching 80Hz with any sensitivity could lead to an excessively large/heavy box (ideally requires 1m+ horn). Also, finding something which will deliver significant kick at 80Hz and sound good up to 3/400Hz could be difficult. I like 120Hz as a crossover point between subs and bass-mids as it's high enough to take a lot of work off the bass-mids but low enough that you don't get significant amounts of vocals in the subs. Most (horn) bass bins will play up to 120Hz without any problems. Maybe f3 @ 100Hz might be good to aim for?


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 Subiectul mesajului: how about?
MesajScris: Dum Noi 20, 2005 10:25 pm 
fk1 have had a lot of success by folding the low section of their cabs and i suggested fitting a type of hd15 section under a porn horn on speakerplans, the real weakness of a lot of cabs is the low mid, porns dont go low enough for most purposes and neither do thl811's etc. theres a gap which need to be filled there and many of us dont want to add another amp/controller channel to fulfil it. i think the cab should go down to 100hz, be a 3 way design with the himid/hf passively (or switchable) crossed at around 3.5k to allow a 1" top to just add fairy dust rather than clacking and squarking. dispersion i reckon should be 45% as most party crews will use 2 min in a stack which will give good coverage and be arrayable for multiples.with either an 8" or 6.5" for high mid. i reckon that crossing over so high will add to definition and avoid difficultis in the vocal range.

well thats my tuppence worth.

rich


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MesajScris: Dum Noi 20, 2005 10:33 pm 
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dammit. dont know what happened to my name in that last post?

_________________
what do you mean "can you turn it up?"


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MesajScris: Lun Noi 21, 2005 12:48 am 
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@chilli: I'm with you on your specs for the box. Low mid is definitely something lacking in a lot of boxes.

Best I've got so far (using light,cheap drivers) is two SN12MB's on a 60cm horn giving 134dB continuous @ 200W/driver and f3 @ ~95Hz. If don't go for Neo then there are a few other drivers which would work, ultimately giving a few more dB.

This is the easy bit however. The bass-mid horn is likely to be a real challenge to build if I can ever get the concepts out of my head and onto paper of course!


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MesajScris: Lun Noi 21, 2005 4:58 pm 
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to answer graeme, echo ceharden and reiterate my own points, what i think the group should work on is an arrayable cab capable of crossing over low enough to get the best from a folded horn subwoofer such as the punisher or lab. the lab really doesn't like playing higher than 80 as i understand it, walt reckons that's where the punisher sounds sweetest, whilst my martins play higher the straight horn equipped mkI bin sounds better doing that bit, you get the picture...

for the diyer who really has amassed a proper big bottom end there isn't a coherent kick bass and mid top sollution that they can put on top of it, using up to maybe four a side to get decent coverage, but at any given point the throw from one box is concentrated enough to keep up with all that bass.

i think we (possibly incorrect use of the word) basically want x-tro performance and packaging cleverness in a trapezoidal enclosure, although there are a few other specifics emerging. the most prevalent of these is that the upper mid cone has got to try and harness the best part of the vocal range, most particularly the top end.

noise control seem to have pulled off 2k with a 10" without using a phase plug, but as graeme says 2.5k really will require us having designed one in from day one. i am very interested also in how the bung in funktion's resolution tops is used to tidy up the dispersion to help facilitate good arraying, although the specifics are quite beyond me at present.

slenium's HL14-25-SLF horn is one of the only 1" horns with a sensible dispersion obviously available but the screw on fitting, as discussed before, puts it out of the running. i was actually more concerned with the polar response plots which seemed to show it as a poor top end performer. fairy dust (i like that...) must have decent dispersion in order to get any real sense of space to the program material. i have been forced to cross over to an array of supertweeters to get proper hf dispersion on my rig.

graeme, you are the only person i know of to have tackled an hf flare with wood, would you recommend this approach?

drivers... i'm all for seeing how far we can get with the p audio sn series, the price is right and the performance seems promissing but i haven't had a bash with the 8" yet. the most promissing 8" horn model for the rcf/mckenzie top box i was working on was a tractrix and the almost linear phase response plots leed me to believe it could be the winning choice.

budget is a factor too, at list price pap could furnish any uk types with 2 x sn12mb, an sn8mb and a de250 for prototyping purposes for around £270 plus postage. good value? how does the budget committee see this?

appologies for the verbosity...

james.


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MesajScris: Lun Noi 21, 2005 8:35 pm 
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Wow! A guy goes away for the weekend and misses so much!

@Graeme,, Glad your here. I've read and re-read and re-read again your information on phase-plugs.

Again, the 12" design is based on another mans work. The horn length is 110cm. I've combined two cabs with a few modifications to meet my orginal intent. The orginal design is actually pretty reasonable in size and build, but again this was designed as a seperate unit from mid-tops. I've got a drawing started and will post some specifics tonight. As far as a Neo driver, let's have a look! Same response and lighter is an improvement!

I'm with all on the 45deg design. Crossover should be at least 2500. 3000 would be better.

Jim


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@James: Have you actually seen inside one of those Noize Control boxes? - the only info I can find on them shows a grille in the horn, so cannot tell what is happening in the throat. I also note that their info does not include response and polar plots....

The polar plots of the HL14-25 horn didn't impress me much either, but not entirely surprising with continually curved side walls. Again, I'm not certain that the curved walls of the Noize Control tractrix can maintain a constant directivity vs frequency, unless someone can show otherwise with polar plots.

A wooden HF flare would not present much problem, as all the fancy throat geometry is already included in the driver, and all that is needed is a short straight-sided waveguide similar to the F1 Resolution top end. The main consideration would be the use of body filler in the corners close to the throat to give as smooth a transition from the round hole to square horn as possible. I have also found that bare timber can absorb HF energy, and a few good coats of gloss paint can make up to 6dB difference..

The F1 axehead plugs are very interesting. If you start with a flare using straight panels all around, and then calculate a central member to give an exponential area expansion (for high efficiency) as well as using it to effectively split the horn into two vertically stacked segment, you end up with something VERY similar in shape to the F1/Turbo axehead. I did try this (in timber - VERY time consuming to make from layered shapes) and found it narrowed top end response considerably. However, I was using a different throat geometry, so this probably made it worse, but it would seem that this style of plug will influence dispersion as well. LOTS of experimentation would be required to get this system right, and while Funktion-One would have had the neccessary time, resources and cash to develop this (and very well I might add), it would be beyond the scope of most DIYers. I think we should be able to achieve very acceptable results without having to go to this extent.

There are a few problems associated with narrow dispersion horns. We need to make the mouth width large enough to maintain pattern control at lower frequencies, and the sidewall angles will dictate the depth of the flare. In this respect, an 8" driver would allow a shorter horn than a 6.5" driver. A long flare with shallow sidewalls will tune to a much lower frequency than what would be normally required, naturally increasing low end efficiency at the expense of top end loading. Techniques such as a fast initial flare rate (achieved through phase plug geometry) feeding the lower rate can improve the top end, however an unnatural midrange response hump around 400Hz to 700Hz is a typical consequence. To offset this, a driver with a rising response characteristic (response increases with higher frequencies) will work very well.

I have been looking at a few different drivers, including the SN-8MB and the B&C 8PE21. Unfortunately, most 8" drivers available off-the-shelf are really designed as mid-bass woofers and not as dedicated midrange units. As such, they usually have low resonant frequencies and reasonably heavy cones. Drivers such as whatever is in the F1 resolution mids just aren't normally available without a special build. The raw response of both the SN8MB and 8PE21 would present a problem in the low-mid area. The Eminence Beta8 response is a little better, but I still had problems with a 500Hz hump in a previous design. Whilst I haven't modelled it, the small Xmax of the 8PE21 could also be a limit, depending on the lowest frequency it is taken. Both these drivers have similar sensitivities within our intended operating range, but is not overly high. The SN8MB is available here in Aus at a reasonable price, so I may grab one to play with anyway.

Most of my current work is based on the 6.5" Eminence Alpha6 - mainly because it is cheap!! (here anyway), however the importers no longer stock this model, so I will have to look at something else anyway. Whilst I have had good results with the Alpha6, there are other options to gain better performance. One driver that has caught my eye is the 18Sound 6ND410 neo 6". This beast has the desired rising response, high sensitivity and good power rating and will probably work very well despite a slightly longer horn requirement. I plan to get one of these for further experiments.

In regards to the low-mid section, I was wondering if the SN12B may be a better choice than the SN12MB, due to higher sensitivity and power rating.

Cheers
Graeme

PS: Do I get the prize for longest post :lol:


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