lower-mid horn design |
Post Reply | Page <1234> |
Author | ||||
JD01
Young Croc Joined: 23 August 2004 Status: Offline Points: 819 |
Post Options
Thanks(0)
|
|||
@ RayVaughn: How do you cover the range from 100-1000Hz now? And what tops are these, going only from 1000Hz up? Seems there is already a misunderstanding or misconception...... I agree with Pinheiro that you won't get this spectrum out of one box in a good way. Around 200-300Hz there is kind of a boundary for what speakers/horns can do, so you can design a horn that will be very good below 200Hz or you can do one that will be good above 200Hz. This is, of course, NOT a limitation coming from the diameter of the speaker, but the type of the horn. If you want real output around 150Hz and below you need to have the horn folded for getting it into a transportable shape. Above 200Hz you need a straight horn, because the mids won't play well in a folded design. Of course a folded horn will go even lower then 100Hz.... and a good 10" horn with phase plug will go above 1kHz...... but there is no good way to do it with one speaker in one box..... As I said the output capabilities have nothing to do with the drivers diameter. The most amazing sub horns use 12" speakers.... Why? Simply because bigger drivers won't take the stress on the cone (bigger cone plus proportionally higher BL --> more stress). We have bass horns with 4 10" drivers per horn. They can do 40Hz (in a stack of four) to 250Hz real flat and really good sounding (flat doesn't mean that the timeline looks good too!) and they get very loud, so you see, the size doesn't matter in this case! Of course these are 10" drivers made for bass, not for mids. 15" drivers in horns should not be operated above 700Hz and even that doesn't sound really good.... and of course a horn of that type won't go below 130 or 150Hz (because it has to be straight and has to have a reasonable size)! So.... |
||||
RayVaughn
Registered User Joined: 20 August 2004 Status: Offline Points: 62 |
Post Options
Thanks(0)
|
|||
It's a 4 way system (per stack) Don't ask me about the kevlars, they're not available to the public
- they're a favour from a friend. The 6" are most unusual as the
effective radiating area of the diaphragm narrows with frequency as a
result of having no surround. Nothing else sounds quite like them. The 6" are fairly sensitive in the region we use them (100dB/w) but will be the limiting factor when i upgrade the lower mid. Thats ok. There's a price to pay for effortless clarity in vocals etc. The 7" are not very sensitive and despite the largish
array don't cut the mustard. I could just replace them with
a light coned 2" voice coil driver and throw more power in but a horn
is clearly a better way to go.
This makes sense. Maybe I need to be realistic and design for a 150Hz to 500Hz range.
Agreed.
Also true. So... I'm going to try and design for a 100Hz to 800Hz range with a view to using 150Hz - 500Hz |
||||
---------------
Ray Vaughn and on www.innerfield.co.uk www.rocketfestival.com |
||||
RayVaughn
Registered User Joined: 20 August 2004 Status: Offline Points: 62 |
Post Options
Thanks(0)
|
|||
I've been experimenting in McBeans program with various
drivers and horn flares. The best results have been with the TAD 1201
driver but I'm unhappy with it's low frequency performance. I too had assumed that a phase plug would be necessary
but don't really know what I'm doing! Still, I'll have a look at the
phase plug equations of Rogs that you're talking about. Currently the models I've done in McBean are only exhibiting 2mm excursions even at 100Hz... |
||||
---------------
Ray Vaughn and on www.innerfield.co.uk www.rocketfestival.com |
||||
JD01
Young Croc Joined: 23 August 2004 Status: Offline Points: 819 |
Post Options
Thanks(0)
|
|||
I see. So you want to go down to 500Hz with the 6" speakers then? Will they 'like' that? How do you crossover? All active or some ways passive? |
||||
RayVaughn
Registered User Joined: 20 August 2004 Status: Offline Points: 62 |
Post Options
Thanks(0)
|
|||
4-way active using BSS Omnidrive, 24dB L-R slopes, per band limiters. Only eq is a 6dB/octave ramp from 10kHz up to compensate for the roll-off of the tweeters. I tried running the 6" down to 750Hz last weekend and it sounded good. I'd say slightly better than crossing over at 1K but It's subtle. According to the designer of the drivers 500Hz is ok. I'm planning to add another 4 of these per side anyway and angle them down by 20 degrees becuase the top end of the range is quite directional. They should add well below 1K if they're close enough together so I'll get another 3dB at the bottom of their range. |
||||
---------------
Ray Vaughn and on www.innerfield.co.uk www.rocketfestival.com |
||||
JD01
Young Croc Joined: 23 August 2004 Status: Offline Points: 819 |
Post Options
Thanks(0)
|
|||
Adding up on the 6" seems to be a good idea...
Have you considered designing a passive crossover for the 6" to tweeter cross? So you could really do two horns... it's because I don't think that your existing basshorns could do better if crossed over at 100Hz or even slightly lower. I mean the rest of your system seems to be very audiophil, so why getting the 'slow' and heavy 18" above 100Hz? |
||||
RayVaughn
Registered User Joined: 20 August 2004 Status: Offline Points: 62 |
Post Options
Thanks(0)
|
|||
It's a fair point - maybe... I'm reluctant to split the mid any further - more sources, more x-over trouble ... On the other hand maybe the lower mid horn can extend down a bit. Here's the SPL plot from McBean with the TAD TM-1201 on a cosh horn I know its a pie in the sky plot here but maybe 120Hz is on the cards ;) |
||||
---------------
Ray Vaughn and on www.innerfield.co.uk www.rocketfestival.com |
||||
Timber_MG
Registered User Joined: 27 March 2004 Location: South Africa Status: Offline Points: 1454 |
Post Options
Thanks(0)
|
|||
My sims show the SN-12B to be very good up
to around 800Hz regarding power response and if one looks at 0 to 30 degree
performance, I seem to be able to get the horn up to 1kHz and a little
higher or there abouts until I get -6dB @ 30 degrees off axis (designing for a
60 degree cab). I presume the -6dB @ the angle I want to cross over in a horn
top to be the highest I can push the horn before I get lobing, right? A 40
degree solution might allow one to cross higher. For simplicity there is nothing like buying a working solution though. |
||||
Timber_MG
Registered User Joined: 27 March 2004 Location: South Africa Status: Offline Points: 1454 |
Post Options
Thanks(0)
|
|||
And you should model into 4x pi, way too little ripple in that plot for
it to be a reasonably sized horn (except if you plan on tops much wider
than 50cm). That is some extreme bandwidth you have there, but TAD is
very expensive and IIRC has around 100W power handling. I generally use
Tractrix flares as they end up shorter and show less ripple than
hyperbolic/expo horns of the same mouth area (though I may be doing
something wrong)
|
||||
roborg
Registered User Joined: 05 July 2004 Location: United Kingdom Status: Offline Points: 1026 |
Post Options
Thanks(0)
|
|||
Yeah i suspected a mid-horn cab i've built was getting seriously hot (2x300w 10"s driven with about 1Kw.) I also have a tiny rear volume (smaller than mt102) & really thick walls, so heat dissipation was only thru the speaker cone (which was getting damn hot after a full power test (so were the neighbours tempers ) So i fitted a 100mm plastic tube through the rear of the box to each speaker vent (sealed with silicone sealant) & now it's all peachy. It sounds as good as before only without the insane heat buildup & prolly much less power compresssion, i didn't notice any P-C before but then i was getting bad hearing compression The prob with an aluminium access panel is that for the cooling to work you don't want to put damping material over it & u really need to line all the walls of a mid-cab with a good heavy layer of absorbent stuff. Cheers, Rob. |
||||
What I cannot create, I do not understand
|
||||
roborg
Registered User Joined: 05 July 2004 Location: United Kingdom Status: Offline Points: 1026 |
Post Options
Thanks(0)
|
|||
Here's a pic of the mid-cab cooling butchery the holes are now filled with 100mm plastic tubing. The drivers get hottish to the touch now, but no more & that's after a real thrashing.
|
||||
What I cannot create, I do not understand
|
||||
Timber_MG
Registered User Joined: 27 March 2004 Location: South Africa Status: Offline Points: 1454 |
Post Options
Thanks(0)
|
|||
Interresting. I take it the driver doesn't have a vented pole piece, as
otherwize you'd have a very leaky box. Come to think of it the SN-12B
doesn't seem to have an opening on the back plate either, but I think
in the long run leaks might creep in at some stage.
The SN-12B doesn't have a traditional backplate to which one could seal easily, but bringing the driver flush to the outside of the box and sealing off the gap around it with some suitable sealant seems like it might help the driver dissipate some of the heat and shorten the cabinet a little more. For access reasons this would have to be incorporated into the acces panel. Servodrive for instance circulate external air through their motor and achieve compression levels unheard of in traditional motor designs (like 1.5dB long term @ 2 times rated power) |
||||
Post Reply | Page <1234> |
Tweet |
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |