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 Subiectul mesajului:
MesajScris: Vin Dec 02, 2005 3:09 am 
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With respect to low extension there is a driver choice to make. The SN12B is definitely more of a horn driver and will probably give a tighter sound in the 100-300Hz range which is important. (Anyone else think this is actually quite a narrow range for a driver to cover?) I've also tried the SN12MB which appears to give a nice low extension (due to higher Q and lower BL) but might not give as much punch. The SN12B will still allow easily for the 120Hz crossover I'm after so I'd be happy with them.

Having just played with your params, seems a little bit of low extension can be gained at the loss of a little efficiency by increasing the throat area and volume, try 300 and 8000 to see the difference, somewhere inbetween might be more sensible. You can also probably reduce the rear chamber to about 20L. Damn those trade-offs! This kind of tweaking may be something that only prototyping can tell us.

Btw, anyone up for a complete point source? ie mount high horn within mid horn within mid-bass horn? Or is that getting too complicated??? :lol:


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 Subiectul mesajului:
MesajScris: Vin Dec 02, 2005 10:02 am 
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james, ind.st scrie:
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..


Not sure on the single horn with two drivers because of the size of the wave guide assembly for the mids. Keeping to two distinct flares will be easier to model and constuction would be easier if the mid wave guide isn`t floating?.
Yes the 215 concept is wicked in space saving ...

As I said I`m just sniping from the sidelines

as you were !

.p.


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 Subiectul mesajului:
MesajScris: Vin Dec 02, 2005 11:13 am 
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ceharden scrie:
Btw, anyone up for a complete point source? ie mount high horn within mid horn within mid-bass horn? Or is that getting too complicated??? :lol:


I hought about that (the high frequency driver enclosed in the paseplug of the mid horn ) bat the phaseplug can get big, and will probably not perform corectly :roll:

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 Subiectul mesajului:
MesajScris: Vin Dec 02, 2005 12:09 pm 
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point source, hmm... i know i mentioned this when i first discussed the whole up-ended trapezoidal martin bin thing, best suggestions were robbing the unity horn design or something akin to graeme's 2 x 6" + 2 x 1". i haven't come up with anything particularly ground breaking yet, the compression horn flare in an axehead phase plug has been used on the tannoy iq10 series to great effect, tony once again holds all the patents.

i'd really like a point source but it's not the be all and end all is it? apparently the sound physics labs 3 way unity horn is the perfect horn top when it comes to close packed seamless arraying, so something which just used two 6" and one 1" to do the top end sat inside a low mid flare might achieve this goal? costs rocket.

ceharden, the driver i had modelled that horn for was the sn12b, i have plummed for this over the sn12mb for exactly the reasons you give. yes 100 Hz to 300 Hz is quite a narrow range, that's probably not such a bad thing though. the driver will obviously play much wider but the horn geometry will dictate the passband.

the response was practically flat from 100 to 400 Hz for the dual driver horn in that packaging, what do people reckon will be the likely effect of splitting it all (and associated volumes and cross sectional areas) into two? i particularly worry about possible effects on the passband, there is not a great deal of margin for eating into the top or bottom end response of the horn.

phil, you are probably right about the size of the waveguides, i haven't given up hope yet but i shall also start jiggling another version that relies on seperated horn flares for the 12s. it's bound not to be as cool though...

james.


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 Subiectul mesajului:
MesajScris: Sâm Dec 03, 2005 3:01 am 
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james, ind.st scrie:
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...




they were.

muppet.

james.


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 Subiectul mesajului:
MesajScris: Lun Dec 05, 2005 6:23 pm 
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having got over the shock of modelling in 0.5 x Pi i have reset to the slightly more conventional infinte half space (2 x Pi, yeah?) and started modelling again from there. thanks ceharden, once again your hints have got me going in the right direction.

it is starting to look a little more promising now, but i kept losing my bandwith when i went for more extension. anyway, had something looking interesting, tried to model multiple speakers and was quite interested in the results. two boxes appears to be flat-ish from a bit below 100 to over 400 Hz, which got me thinking?

1) do people generally model in infinite half space?
2) is it 'acceptable' to model response for two cabs (or one in quarter space) where you intend them to be used together? i sort of feel it is a bit of a cop out, but then again it might be a more realistic way of arriving at the desired response.

answers on a postcard to the usual place.

james.


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 Subiectul mesajului:
MesajScris: Lun Ian 16, 2006 10:18 am 
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james, ind.st scrie:
1) do people generally model in infinite half space?
2) is it 'acceptable' to model response for two cabs (or one in quarter space) where you intend them to be used together? i sort of feel it is a bit of a cop out, but then again it might be a more realistic way of arriving at the desired response.

bump.

james.

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 Subiectul mesajului:
MesajScris: Lun Ian 16, 2006 1:00 pm 
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I hope I've understood what you asked:

1 cab off the ground (4Pi)
2 cabs off the ground (2Pi)
and so on

modeling 2 cabs means only switching from 4 to 2pi and pumping double the power in the sistem

at least that's how I model it :roll:

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Poweraudio Romania
Str. Gheorghe Sincai, Nr.26 Bistrita
Telefon: 0766332366
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www.poweraudio.ro
facebook.com/poweraudio.romania


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 Subiectul mesajului:
MesajScris: Lun Ian 16, 2006 9:04 pm 
Citat:

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



Citat:
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.


I realise this is probably a long shot but....

Most of the big players in speaker design have contributed to the free party scene in some way over the years (notabley the 1850 and Lab subs) but unless there's a design that i'm not aware of, i dont think Mr Andrews has?

Given all the detail and trial-and-error ascoated with making phase plug, that its his recognised area of expertise amongother things, and that it looks as if it'll have an 'axx-heady' :wink: shape anyway, does anyone think he may like this opertunity to help? or even just give us a few pointers and his blessing?

If there is anyone who knows him personally or can get in contact with him we could test the waters? or maybe if anyone is in contact with Rog maybe he could put in a word, as far as i know they're on quite good terms.

As i said just a long shot but i know he has taken a little bit of stick in he past (on the ProSoundWeb forums for example) for not doing something like this and he may he happy for a bit of good PR.


As i said a long shot

kev


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 Subiectul mesajului: tony
MesajScris: Lun Ian 16, 2006 11:16 pm 
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well... funnily enough i was thinking of sending him the cad files with an explanatory note and links to the forum with the simple question, if i build these, will you sue?

actually asking him to pitch in is, whilst i agree a long shot, a much better idea. i've heard he's quite approachable, although i never had the guts to talk to him at glade.

james.

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 Subiectul mesajului: space for modelling
MesajScris: Mar Ian 17, 2006 11:01 am 
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@nexus: have you been modelling cabs in free air? (same question to centauri and ceharden) i had gone for 2pi on the premise that we would be ground stacking. of course once they are set up on top of a pile of bass horns i suppose they will no longer benefit from a boundary effect from the ground, or will they?

also, what did you mean about doubling the system power?

from reading your post i am getting a horrific sinking feeling that i am going about my hornresping in totally the wrong way. someone put me out of my misery...

james.

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 Subiectul mesajului: Re: space for modelling
MesajScris: Mar Ian 17, 2006 11:33 am 
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james, ind.st scrie:
@nexus: have you been modelling cabs in free air? (same question to centauri and ceharden) i had gone for 2pi on the premise that we would be ground stacking. of course once they are set up on top of a pile of bass horns i suppose they will no longer benefit from a boundary effect from the ground, or will they?

well, the thing about the boundary effect is a bit interesting

here is how i see it happening (not necesary a corect way, this is just my sick mind @ work here) while at a higher frequencu, as the quarter frequency lenght is sensibily shorter than the distance from the cab to the ground there should not be any benefit (4Pi in one cab is used), BUT as the frequency goes down, the wavelenght increases semnificaly , and there should be a gain in SPL the lowweer the frequency gets because we are aproacing 2Pi conditions.

Hope you get the point..

Like I said I am not sure about how real this effect is, some imput from the more advanced users would be greatly apreciated, as I have beed using hornresp only about a year now, and I don't know everything there is to know about horns


also, what did you mean about doubling the system power?


for example: if you want to plot 2 HD15 suspended in air you would plot only one cab, set the radiation angle to 2Pi and imput the power for the both cabs summed (this should make hornresp plot a pair of cabs fairly accurate)

a more simple explanation, imagine that by halving the radiation angle , you create a mirror image of the single hd15


from reading your post i am getting a horrific sinking feeling that i am going about my hornresping in totally the wrong way. someone put me out of my misery...

don't be so sure , I may be doing it the wrong way, ( read above :oops:)

james.
:wink:

_________________
ing. Mircea Bartic
Director general

Poweraudio Romania
Str. Gheorghe Sincai, Nr.26 Bistrita
Telefon: 0766332366
E-mail: office@poweraudio.ro
www.poweraudio.ro
facebook.com/poweraudio.romania


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 Subiectul mesajului:
MesajScris: Sâm Feb 04, 2006 4:41 am 
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i've just had the most awesome evening's hornresping, i spent a lot of the time looking at the predicted diaphragm displacement too and i have had to re-evaluate some of my driver applications. the dual sn12b horn of about 80cm length that i had been playing with will absolutely rinse the driver at rms power levels, a pity as the response was looking nice.

the plot for the b&c 12ndl76 is pretty much the same shape at first glance, but wind up the power to the cab's rms rating of 800 watts and the drivers remain nicely within manufacturer's given x-max, even below crossover point and the plot starts to look very, very loud. with two boxes the graph is smoothing out nicely, and the proposed cabinet volume has room for the combined system volumes of the dual 12" horn, an x-tro sized high mid horn, 1" horn, drivers and wood, give or take a bit.

here's the data...

Imagine

it isn't much worse on an 80 cm horn but i'm really clawing for bottom end extension. in spite of this i wouldn't want to cross this over too low as the plot starts to roll off just below 100 Hz.

if i can get that horn to fold into that shape without doing anything too contorted, if the resulting layout is replicable by human kind and then finally if the ensuing cabinet doesn't sound diabolical! then i reckon it would be a good performance from a large but manageable size.

james.

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