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 Subiectul mesajului: what i had in mind...
MesajScris: Lun Noi 28, 2005 6:48 pm 
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righty ho, this is what has been going through my mind of late in terms of layout and operating priciples. the plan is very short on actual detail, the flares are not calculated etc, but you can get the idea from this. thanks again to nexus for hosting this picture.
Imagine
basic points are as follows. the high and high mid horns are "floating" in the low mid horn mouth by being attached to the braces. unbolting these braces will allow access to these drivers and their crossover. to facilitate the use of a passive these two drivers are physicaly aligned within the cab, whilst the hf horn has to be slightly shorter that is no problem as the throw from the mouth will be unobscured by other cabinet components. there is a lot of potential for jiggling this around if we need to incorporate any inclination etc.

the floating mid horn may help cut down on diffraction wierdness, it may make it worse. as the low mid horn mouth is effectively the whole of the cabinet frontage up to the edges this should help the cabs couple when stacked. red bit on the back of the 6" is supposed to be a heat sink.

the 12" drivers are reverse mounted for voice coil cooling and to allow for an obscenely small rear chamber, the exact tuning of the bp-horn combo can be fiddled quite easily.

there is an easy dead space for handles at the top and bottom of the box made by the little seperator between the baffle and front flare piece shown on the picture, the side handles have been ommitted for clarity.

i also think that this is a good box size, big enough to house some decent horns with a bit of cunning but small enough to be manouverable. two will stack on wheelboards in a blatant copy of funktion 1 methodology. there is virtually no wasted cabinet space.

there's a bit more to it than that, but for starters i'm quite chuffed.

james.

edit: spelling and manners.


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 Subiectul mesajului:
MesajScris: Lun Noi 28, 2005 10:49 pm 
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oh yeah, i forgot to mention that there are no parallel walls in the horn flare. whilst i have not compared horns with and without, the boys at noise (control) advised that eliminating paralell walls and abrupt angle changes will do wonders for the "musicality" of a horn. whilst i suspect it looks a bit tight you can definitely fit a pair of 12" drivers in.

wall angle for the box is 10 degrees, hence the chosen dispersion pattern, in theory you should only ever be influenced by a maximum of 2 tops and as you move into the throw of a third you should be hitting the -10 dB point of the first. again, this is just what i have gathered from reading spec and chatting to reay, if anyone knows better...

the high mid horn phase plug follows on from the thread on that subject, most particularly how the plug expands sideways to get the required cross sectional area yet still allows a clear line of sight to the cone itself on the top and bottom to combat hf beaming.

james.


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 Subiectul mesajului:
MesajScris: Mie Noi 30, 2005 12:52 am 
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Looks good James. I've been throwing around similar ideas but haven't managed to get anything on paper properly yet.

What are the 12" drivers again? SN12MB's? I thought when I tried simulating them they needed a bigger rear chamber than was feasible to get a nice response. If you could post the sim params that would be very useful.

When I start prototyping I'll probably just use the odd drivers I have available to me without buying any more (except a 6"/8" which I don't have). Won't give the exact performance intended but will be cheap to prove the concept. I'll probably also build the three horns seperately initially then worry about trying to combine them into one box later.


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 Subiectul mesajului:
MesajScris: Mie Noi 30, 2005 3:39 am 
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i haven't as such based that cab on any particular driver sims, the approach is kind of hollistic reverse engineering of what i had so far considered the key design criteria. when i have a rough idea of the mid and top horn's dimensions i can plot a horn to fit the enclosure and flare rate (less the cross sectional area of the high mid and hf waveguides at each point along its length in a similar manner to the phase plug proposal) by jiggling the flare components and external dimensions till it fits, ditto the driver and rear chamber.

hornresping has kind of started but needs to progress to more tangible output. in terms of bifurcation i was planning on modelling a single flare then mirroring it to the other driver and letting them meet accodingly. this approach appears to have been used in the martin 215 series and the decware wo series. only a prototype would say for sure how well it worked.

as i think the nature of the horn folding/cramming/whatever will have an effect on the tonal charachter of a horn i'm not really that interested in what a "perfect" horn will sound like, hence my tactic of layout first, dimensions after. i think. also i'm not sure how much useful proof of concept you'll get with anything other than the intended driver, fickle blighters that they are.

i'm going to spend a little more time loking into the 12" modelling next, but i'm generally interested to know what peoples thoughts on the hazards or benefits of loading the mid and high flares physically within the low mid's horn mouth with regard to turbulence and phase cancellation at crossover or whatever. there's some community stuff that does this if i remember correctly.

james.


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 Subiectul mesajului:
MesajScris: Mie Noi 30, 2005 2:18 pm 
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Membru din: Vin Noi 18, 2005 10:31 pm
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great design i was working on something like that inspired by the horn of the punisher but a bit shorter
and i dont understand why the 12" are not in a closed box???


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 Subiectul mesajului:
MesajScris: Mie Noi 30, 2005 2:45 pm 
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well,... they are, but the back chamber is really that small space in front of the speaker :wink:

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 Subiectul mesajului:
MesajScris: Mie Noi 30, 2005 3:33 pm 
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I tried some ballpark (exponential approximation) simulations of James' bass-mid horn using the Challenger 12-300MB and the SN12MB (both quite similar). I guessed the path length of the horn to be about 75cm and the mouth to be about 2000cm2 given the area ignoring the mid horn is 5000cm2 (divide by two for the horn seen by each driver). Best results seem to be acheived with 300cm2 throat, 4L front chamber and 12L rear chamber. f3 with two drivers is about 85Hz.

On James' design the front chamber is probably much larger than this, and the rear chamber much smaller. This means that the driver mounting shown probably won't work unless we use a very high BL driver which likes such a small rear chamber. The front chamber is easier to change.

All of the drivers I've tried so far seem to work best with ~10L rear chamber and ~4L front chamber.

What upper limit are we trying to reach with this horn? I'd say for an 8" mid driver 300Hz is ok, but probably needs to be 500Hz if a 6" is used.


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 Subiectul mesajului:
MesajScris: Mie Noi 30, 2005 4:42 pm 
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ceharden scrie:
I guessed the path length of the horn to be about 75cm and the mouth to be about 2000cm2 given the area ignoring the mid horn is 5000cm2 (divide by two for the horn seen by each driver).

if you read my bit on bifurcation you'll see why i am not sure we need to do this, i think it models as one single horn with a bigger mouth.
Citat:
Best results seem to be acheived with 300cm2 throat, 4L front chamber and 12L rear chamber. f3 with two drivers is about 85Hz.

cool. is this for that particular horn length and mouth area? perhaps i was being too optimistic but i figured on the horn being a bit longer than 75cm, maybe 85?
Citat:
On James' design the front chamber is probably much larger than this, and the rear chamber much smaller. This means that the driver mounting shown probably won't work unless we use a very high BL driver which likes such a small rear chamber. The front chamber is easier to change.

All of the drivers I've tried so far seem to work best with ~10L rear chamber and ~4L front chamber.

i shall have a jiggle with those volumes and see what happens, as you say there is plenty of room to maneuver with this layout.
Citat:
What upper limit are we trying to reach with this horn? I'd say for an 8" mid driver 300Hz is ok, but probably needs to be 500Hz if a 6" is used.

now you got me there, that will be determined by the mouth area of the high mid horn as much as anything else won't it? in terms of higher power handling and a shorter horn an 8" is in many ways very desireable. 300hz will already be testing the musicality of a folded horn, and we are starting to hit critical information region at that frequency. 500Hz may well just be too high.

james.


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 Subiectul mesajului:
MesajScris: Mie Noi 30, 2005 6:49 pm 
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I'm not sure about the bifurcation either but I was working on the principle that it was two horns just missing the central divider. If you built a HD215 without the common side, would you expect it to perform the same as two singles stacked together? Probably yes. Of course I might be completely wrong.... I think you either have to model it as one driver with combined parameters in the whole horn (add the individual throat areas together etc) or as two horns stuck together, each seeing half of the large horn.

The best results I mentioned were for the 75cm length and 2000cm2 mouth. I reckon that using the whole 5000cm2 for a 75cm long horn is too large so I'm hoping that you have to share it between the two drivers. Assuming your drawing is to scale, I find a piece of string with scaled markings at 5/10cm intervals is good for measuring horn length.

We probably want to get the crossover to the 8" as low as possible as you say to avoid nasties in the folded horn. 300Hz is probably a sensible/acheivable choice.


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 Subiectul mesajului: modelling bifurcated horns
MesajScris: Joi Dec 01, 2005 3:47 pm 
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ok, so that got me thinking about the specifics of trying to model this horn as the design ain't that much use if we can't. one possible way is shown in another one of my not particularly to scale dodgy byro illustrations.
Imagine
the horn is modelled as a dual driver jobby using the multiple driver feature of hornresp which gives the on axis rear chamber and flare. this flare is then compensated for the additional volume of the high mid and hf waveguides which occupy it (shown by the blue shaded areas).

then... (and this is the suspect bit) one attempts to split the dual driver horn down the middle and bend each half over on itself to realise the final layout (green outline). the volume of the single driver's rear chamber is half that of the dual driver's (as shown by the green shaded area) and the same goes for the volume of the front chamber (cross hatched) and the throat (blue aroow tipped line).

so then, does anybody have any experiences or bona fide reasons why this will or will not work?

james.


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 Subiectul mesajului:
MesajScris: Joi Dec 01, 2005 6:09 pm 
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Couple of quick points from the sidelines....

Not sure the 2 x 12 arrangement on one horn will work? I know it`s only a rough but the back of the central wave guide IMO will need to be against the back of the box and eliminating the "floating aspect" will result in 2 horn flares.

Bolting the phase bung thru` the driver....hmm think Mr Tony Andrews might have something to say about that!

Still a wicked starting point james

.p.

edit ..just hacked your drawing about in photoshop to show what I meant!

Imagine[/img]


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 Subiectul mesajului:
MesajScris: Joi Dec 01, 2005 11:04 pm 
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@James,

Have you simulated the 12's yet? If you have any info I could toss it around in Autocad. My 3D skills aren't very good, but I could get something reasonably quick in 2D.

Jim


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 Subiectul mesajului:
MesajScris: Vin Dec 02, 2005 12:08 am 
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jimbo, bear with me, i'm having a furtle as we speak but hornresp on virtual pc is tortuously slow.

phil, why do you reckon the high mid waveguide will need to start from the back of the cabinet? is that because you think the estimates for the length of that part are too short in this plan or is it because you want to keep the horns as two distinct flares? or indeed some other reason?

i am into the idea of firing two drivers into one horn as it works so well on my martin 215s and the wo series. the symetrical layout is a boon to saving wasted space and it allows for a very desireable "power density" for the truck packing volume.

i am still looking at how others have hornloaded 6" and 8" drivers and it does look like a 6" might require too long a waveguide to facilitate physical alignment of the drivers. did i mention i was keen on using a passive crossover? of course i did, so an 8" might be the most appropriate way of achieving this goal.

is anyone here using ajhorn or one of the others that is supposed to tackle mid well? what are the problems with using hornresp to model higher frequencies than bass?

ultimately i think the only way of knowing if this horn concept actually works will be a prototype, there are just a few too many oddities in the layout and construction to really know from modelling i think. all the same it would be nice to arrive at something credible and logical before undertaking a build because then at least we would be in a position to say: it should have done that, it actually did this, what is likely to have caused that? i am quite keen on this idea, the box represents the zenith of all my thinkings on the subject over the last 12 months and if i can, with some help, arrive at that credible model i will definitely build.

james.


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 Subiectul mesajului:
MesajScris: Vin Dec 02, 2005 12:11 am 
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ha ha, yeah. i know the phase plug looked like it was bolted through the heatsing but i was aware our tone had that one patented.

my one's held there because it's artistically right.

james.


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 Subiectul mesajului:
MesajScris: Vin Dec 02, 2005 1:17 am 
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ok, i've just had a little play with hornresp using the bifuraction method above, that is to say modelling a dual driver horn with long term intentions to split it.

i started with 100 x 50 for the mouth less 40 x 40 for the high mid waveguide and 10 x 10 for the hf leaving an S2 value of 3300. i figured the length was about 80, and used an exponential flare, because they are cool. from ceharden's suggestions i guessed a double rear chamber volume of 28 litres. LRC was 16 and a little jiggling saw me end up with S1 as 200, VTC as 4000 and ATC as 1100. driver was (two of) the sn12b.

i thought it looked rather nice, phase response weren't bad, 135 dB was predicted as being breached before x-max at crossover, directivity looked useable, bit more extension would have been nice...

doh! as per usual though i have forgotten what space i was modelling in and they may have been corner loaded or something gash like that, and now i've shut virtual pc down... oh well, im going to bed so i'll look tomorrow. if anyone feels like modelling it i'd be interested to know what you think. it has come about by reverse engineering a sketch of what i thought might work and dimensions i could live with so i am prepared for it to be quite poor. still, it looked nice enough.

james.


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