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3-Way Mid Top - Plots To Plans

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interweb View Drop Down
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    Posted: 19 December 2016 at 5:44pm
Hi all,

First things first, I'm an old member (Loonie) for those of you who knew/know me, but my account was deleted/deactivated.

**Spoiler** This WON'T be a short post, I'm intending to design a three way mid top from the ground up with limited HornResp knowledge.

Intro


I've been out of the game for a little while now and have decided to get back to it and finally do my own designs. I've got quite a bit of knowledge regarding sound engineering as well as the advanced mechanics of how our speakers work and I used to work for a small speaker fabrication company as well as a larger one. I'm just missing this last piece of the puzzle in my set of skills, the design.

So here we go,

This is the first trial for me designing the low mid first of all so that I can utilise it as a kick bin if it's not suitable for the form factor of a 3-way, therefore not wasting everyones time etc.

I've got screenshots of all of my screens on Hornresp and was just going to go through them one by one and give a short annotation so that other users wanting to learn can see my design process.


Plots & Inputs



So firstly I've had the caution error poopping up reminding me that my VRC is less that the surface area of my cone (SD), I believe I've sorted that now and I'm running with a chamber size of 40L as the spec sheet for the Precision Devices 12SB30 recommends 25L minimum per driver, so I don't think I'm being too aggressive with my choices.

I've not played with the exponential sections of the inputs, I'm only focusing currently on the S1, S2, S3 sectors of the horn as I'm not wanting to over complicate the process....yet.

I would kindly wlecome constructive criticsm as I'm sure there are some hilarious vales in here that may not work in practice, please feel free to flag these up to me if you notice them!

Lastly, this is for a 12x2" low mid, I have chosen this simply as I already have 4 x 12SB30's and I thought I could get straight to prototyping once I was happy with everyhting, I am also thinking about a B&C single 18" low mid as I currently have one, although not suitable for horn loading. So please just bear this in mind, I'm trying to make something practical whilst learning so everything is subject to change.



Not much to talk about here, it's the bit we all love to see I guess. So I'm aiming for a frequency response of 55-180hz so I can use these as DJ monitors / infills and the like. I chose 180hz because I'm after a smooth crossover between the high mid horn which I guess will come in around 120-160hz. Also wanted a lower cutoff so it could be used with subs or bass bins if needed.

I'm not too worried about the spike shown at 180hz as this is my upper cuttoff and I thought rather than trying to get the 12" to play the 60-100hz louder I could just use a hefty EQ on the DSP to bring that lump down to give me a flat range from 60-180hz.



This window completley baffles me, I'm not going to lie, II have no clue what I'm looking at other than a dual overlay showing me the correlation between ohms and hertz.
If i'm getting that large spike of 17ohms resistance at 74hz isn't that going to be horrendous and play havoc for the cab and or amp?

Lots of help needed here please... LOL



Good old displacement, xmech xmax blah blah blah, so the 12SB30 has 9.2mm Xmax on the data sheet and the worst I'm hitting is 2.7mm at 95hz, the low end roll off is 0.3mm at 67hz.

Not much else to report here, everything looks fine to me as long as I use a decent slope on the LPF/HPF.



Again, not a single clue as to what this is showing me, obviously a large spike of 21.8 ohms at 100hz but is this a problem? Is this the actual impedence that the amplifier sees?

Lots of help needed here as well please Wink



This one I've actually looked up and to what I can assertain this graph is showing me the articulation and transient characteristics of the driver whilst in the horn. I.e how slow and fast it can play at varying frequencies, right?

Therefore I guess we can take from this that the lump of 14ms at my lowest cutoff point of 55hz is going to give me a slow transient in the low end and potentially sound muddy and not be able to cope with the low end unless i were to choose a higher HPF and lower LPF on the sub?

The other issue I can see is that there is around 9.7msec at 170hz which is also rather close to my upper cutoff, I'm sure this means there will be some phasing issues going along somewhere and perhaps a cue for me to read more on horn theory?

Help needed here also please!



Again, some help needed on this section, I do understand phase and cancelations etc but I'm assuming this isn't quite the same topic at hand. Focusing on the image I can see that at my upper cutoff i've got around -120 degrees of shift which I'm assuming isn't bad but also not great.

My lower end comes in at around -31 degrees of shift at 55hz, now the only thing worrying me is that the cone is always going to be moving in a negative movement and isn't  showing anything positive which I'm guessing will mess with the phase also and cause a cancelation when used perhaps?



Finally the schematic, firstly the horn is already around 2m long from what I can figure out and already could be in the realms of horrendous kick bin, useless mid top design, which I'm happy to deal with and admit because obviously the 12SB30 is a sub bass driver and there are obviously other designs which work well, but as I mentioned before, I want to prototype and test and these are the components I have currently.

I have used a conical flare throat adapter which I'm looking forward to CAD'ing and fabricating but is this just the same as a letterbox? OR is it literally going to be similar to joining a square horn onto a round baffle? Am I going to need to cut a bunch of rings and stack them / get the lathe out to get an actual conical flare? This may be something I change in the design and perhaps utilise a letterbox providing I don't have too much compression in the chamber/throat area and shred the paper cones.

All things to think about, but I thought it was best to post all of this here and let the community help me bring something fresh and practical for all to use as Davey T isn't banging them out like he used to, damn Minirig LOL

Anywho, I say a forward thank you to all on the forum for the help I've recieved before as well as what I wish to recieve, I don't know why I ever left. Good to be home guys.

Now, where's the scoop forum, I want me some drama LOLLOLLOL

Loonie











Edited by interweb - 19 December 2016 at 5:57pm
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gen0me View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 22 December 2016 at 9:59pm
You came into topic same way as I would.
I interpret this group delay graph as:
dont cut speaker at 55Hz and 170Hz the best 80-130Hz - flat delay chart.
You could try System design>>With driver, then change horn to exponential and make it compact. Could get more flat response.

https://postimg.org/image/hwyxvmbb5/ -

https://postimg.org/image/vrx8e35q9/ -

https://postimg.org/image/j1t00zxs1/ -

https://postimg.org/image/lkep1oji9/ -

Can design some 3d flare/phase plug. Export in .stl file and 3d print in plastic(expensive) or you can Export it to dxf vectors and CNC it in wood, plastic, gum, anything.Tongue
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 22 December 2016 at 10:21pm
Hmm as it is for 2P(2 speakers) start thinking about how to place them in space so the front chamber would be 0,4 dm3.Dead This driver has 530 cm2 Sd! That is a place where I bounce back to 1 speaker in my designCry

Edit.
My mistake, its a kickbin. Ofc you can increase front chamber size so 2 should fit for your freq range.

Edit2:


Edited by gen0me - 23 December 2016 at 6:55pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote loonie Quote  Post ReplyReply Direct Link To This Post Posted: 30 June 2017 at 12:53am
Ok, so it's been 6 months and i've come back to find my exact same post and I haven't even pushed it forwards AT ALL.

Massive thread BUMP!!

Someone please help me!

Loonie (Interweb)
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