New DIY Mid High (90deg) - AKA PM90

Re: New DIY Mid High

Ossian Ott said:
I have a question, would it be possible to use another CD driver(bigger?), which can go down to 600-700 hz but not as far up to 20k(say 10-15k) with the same SPL as the 4594HE, but not being Coax and considerably cheaper? Is this a bad approach or could it work without losing to much HF/air in the cab.
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The best option to save some money is to use the standard BMS4594ND and use B&C 12NDL76 12” drivers. Having the HF section go down to 600 to 700Hz is critical. Once the Mids are pushed beyond this it all starts to fall apart.

Here are some of the best high performance 4” diaphragm drivers, but these are only recommended for a minimum crossover of 800Hz

http://www.bcspeakers.com/products/hf-driver/2-0/de1085 (not available in 1.4”)
http://www.eighteensound.it/PRODUCTS/Products/CatID/3/ProdID=152#.VaWWVmkiPq4
http://radianaudio.com/product/950pb/ (may be available in 1.4”?)
 
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Re: New DIY Mid High

Peter, as I've been designing my particular build of your box, I've been trying to understand your methods to designing it as well. One of the things I'm curious about are the ports. Am I correct in guessing that you're using them to limit the excursion of the 12" drivers just below the crossover point around 100Hz (their tuning being somewhere around 90Hz)?
 
Re: New DIY Mid High

Max Warasila said:
Peter, as I've been designing my particular build of your box, I've been trying to understand your methods to designing it as well. One of the things I'm curious about are the ports. Am I correct in guessing that you're using them to limit the excursion of the 12" drivers just below the crossover point around 100Hz (their tuning being somewhere around 90Hz)?
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Hi Max,

In this case it gives you about 6dB more output at 100Hz and limits the Xmax. One of the compromises with the DIY is size an weight. I would have preferred to be all horn loaded but that makes the box too big, so I added some ports.

The whole idea for the design was to put as much SPL and sound quality on a stick as I could. I wanted to exceed the performance of anything that was commercially available.

Here is a couple of Sims @ 1300 watts per driver, tunning is around 80Hz. Note, this is acoustic power not frequency response and it compares the response and Xmax with and without a port.
 

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Re: New DIY Mid High

Peter Morris said:
Hi Max,

In this case it gives you about 6dB more output at 100Hz and limits the Xmax. One of the compromise with the DIY is size an weight.
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I do this on my coax wedges. Tuning helps limit excursion. The second part of your quoted section struck me odd, as DIY to me has always been an opportunity to move away from the conscription of size and weight sometimes. Commercial products tend to be as small as possible to save costs many times.

John
 
Re: New DIY Mid High

John Halliburton said:
I do this on my coax wedges. Tuning helps limit excursion. The second part of your quoted section struck me odd, as DIY to me has always been an opportunity to move away from the conscription of size and weight sometimes. Commercial products tend to be as small as possible to save costs many times.

John
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Hi John,

I didn’t set out to build a DIY project. My aimed was to build something that was not commercially available, to fill a niche in my hire inventory.

The design criteria for the Mid Hi was to put as much SPL and quality as I could on a stick down to about 80 -100hz i.e. there were limits to the maximum size and weight.

I wanted it to be less than 35Kgs and to look like it belonged on top of a double 18 or even a double 21.

I didn’t want it to look or perform like a “DIY project”. I wanted extreme quality - frequency response, impulse response, phase response, distortion, pattern control and SPL … and I wanted to be able to use a smaller truck or van and need less crew than would be normally expected.

To me from a hire company perspective that = $$$
 
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Re: New DIY Mid High

Peter Morris said:
I didn’t set out to build a DIY project. My aimed was to build something that was not commercially available, to fill a niche in my hire inventory.
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I see this box as being in the same category as the Smithers coax wedge (or the John Halliburton coax wedge for that matter). There's really nothing out there of the size and quality on the commercial market that doesn't cost an arm and a leg, so someone comes up with a DIY to fill the niche.
 
Re: New DIY Mid High

hi there

I've been watching and reading about this design with interest for a few weeks now. For the 12" section, I don't mind buying the RCF drivers if needed, but I already have both BMS 12n802 and BMS 12n810 here, I wonder if you'd be kind enough Peter to sim both and see how suitable they would be for the design (of if a minor change to the horn or ports could make them suitable).

i suspect the 802 may be a little too suited for a reflex design and not a ported horn, while the 810 may go too far the other way and be better suited for a true FLH, but it would be nice to see if they can be made to work since I already have them here.

Thanks for your help

k
 
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Re: New DIY Mid High

Kevin McDonough said:
hi there

I've been watching and reading about this design with interest for a few weeks now. For the 12" section, I don't mind buying the RCF drivers if needed, but I already have both BMS 12n802 and BMS 12n810 here, I wonder if you'd be kind enough Peter to sim both and see how suitable they would be for the design (of if a minor change to the horn or ports could make them suitable).

i suspect the 802 may be a little too suited for a reflex design and not a ported horn, while the 810 may go too far the other way and be better suited for a true FLH, but it would be nice to see if they can be made to work since I already have them here.

Thanks for your help

k
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Hi Kevin,

Here are the frequency/power response plots. Note - these power response plots do not account for directivity. The increasing directivity will cause the HF region to be much more efficient than shown. Unfortunately Hornresp can't model directivity with 2 part ported horn.

The 810 looks good except its Xmax is limited compared to the RCF. ( 2.5mm Vs 5.5mm but they are measure / calculated differently - I suspect the BMS has a useful Xmax of more like 4.5mm)

The 802 response doesn't look particular good but the Xmax is fine.

The trick with the RCF was the 3.5" VC which resulted in a relatively light Mms and high BL product that's need in this design, while still allowing a reasonable Xmax and power handling.
 

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Re: New DIY Mid High

Thank you for taking the time to do that. I agree that when you calculate the xmax using a more traditional method 4.5mm seems about correct, so I will at least give them a try.

I have discovered I have a maker-space type facility near me that I've been considering investigating, which can potentially CNC cut the wood for me and also provide CNC plasma cutting for custom grill designs, and I have two of the BMS 12N810 speakers here as well as the slightly bigger 4592ND coax driver which is on a 2" 90 degree horn (beyma TD400n).

The box will need to be slightly wider and deeper to accommodate these different components, however while it won't be the exact same as your original it means that with a little modification I can give the design a try simply for the cost of the wood, and get a chance to compare it to various speakers I already have, plus it'll give me a chance to try the maker facilities for some future projects.

Will keep everyone updated on my progress.

k
 
Re: New DIY Mid High

Kevin McDonough said:
Thank you for taking the time to do that. I agree that when you calculate the xmax using a more traditional method 4.5mm seems about correct, so I will at least give them a try.

I have discovered I have a maker-space type facility near me that I've been considering investigating, which can potentially CNC cut the wood for me and also provide CNC plasma cutting for custom grill designs, and I have two of the BMS 12N810 speakers here as well as the slightly bigger 4592ND coax driver which is on a 2" 90 degree horn (beyma TD400n).

The box will need to be slightly wider and deeper to accommodate these different components, however while it won't be the exact same as your original it means that with a little modification I can give the design a try simply for the cost of the wood, and get a chance to compare it to various speakers I already have, plus it'll give me a chance to try the maker facilities for some future projects.

Will keep everyone updated on my progress.

k
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The design will not work correctly with that horn. It has a cut off frequency of 800Hz .... you need to cross below that 600Hz to 700Hz.

The trick with this design is using a compression driver and horn that could go low enough so it could be matched with a bent dipole horn arrangement.
 
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Re: New DIY Mid High

Peter Morris said:
The design will not work correctly with that horn. It has a cut off frequency of 800Hz .... you need to cross below that 600Hz to 700Hz.

The trick with this design is using a compression driver and horn that could go low enough so it could be matched with a bent dipole horn arrangement.
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lol very true. In my excitement at trying out this design and checking that the 810s for the 12" section would be a possibility, I forgot to check this. Having a look at some available horns, the only one I can see initially that meets the criteria of 90 degrees (edit: actually, while the website I saw it on said 90 degrees, the actual ciare spec sheet says 100 degrees) with loading down low enough is the Ciare PR 401. However it then becomes a little wider even than the beyma horn, which was already wider than your original design.

I'd have to make the cab around 80mm wider internally to fit the horn at the front which isn't ideal. Or possibly add a slight trap angle to the sides, a very rough scale drawing says around 6 or 7 degree sidewalls should keep the baffle for the 12" around the same but then expand enough by the front to squeeze in the larger horn, but this obviously then changes the expansion of the horn and will have an effect on the response.

Nothing is ever easy! :lol:

k
 
Re: New DIY Mid High

Peter Morris said:
The design criteria for the Mid Hi was to put as much SPL and quality as I could on a stick down to about 80 -100hz i.e. there were limits to the maximum size and weight.

I wanted it to be less than 35Kgs and to look like it belonged on top of a double 18 or even a double 21.

I didn’t want it to look or perform like a “DIY project”. I wanted extreme quality - frequency response, impulse response, phase response, distortion, pattern control and SPL … and I wanted to be able to use a smaller truck or van and need less crew than would be normally expected.
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It looks like you hit your targets. I hope it works well for you.
 
Re: New DIY Mid High

Finally had some free time today to work on assembling these. The panels have been cut and sitting in a pile for 8 months. Better late than never I guess. 20160207_154941.jpeg20160207_185114.jpeg
 
Re: New DIY Mid High

Brandon Wright said:
Finally had some free time today to work on assembling these. The panels have been cut and sitting in a pile for 8 months. Better late than never I guess. View attachment 14010View attachment 14011
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That's looking great, once you have load the speakers into them the hard bit begins .... developing some settings. I think you will like the results, and I'm sure a few of us will be able to contribute if needed . :)~:)~:smile:
 
Re: New DIY Mid High

Peter Morris said:
That's looking great, once you have load the speakers into them the hard bit begins .... developing some settings. I think you will like the results, and I'm sure a few of us will be able to contribute if needed . :)~:)~:smile:
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I would like to say that even just throwing the IIR settings on the box from the DIY 60 degree thread sound absolutely fantastic. I can't wait until I have access to the tools and some time to work out the settings.
 
Re: New DIY Mid High

Ready to start making sawdust...I am so excited to make these speakers. I ordered my 12" speakers, components, handles, etc. I am gonna order my BMS drivers as soon as the group buy thread is ready. I have two questions before I mess things up. I have read people are using 18 mm for the baffle structure and 15 mm wood for the exterior shell. Living in Iowa, I am able to find 1/2" and 3/4" Not having luck on 5/8" plywood to mix the two sizes. Does this mean I should use 18 mm for the entire box? Lastly, the .pdf I have is in post #316 of this thread. Is this the final most complete and accurate build version if using the RCF950 horn?
 
Re: New DIY Mid High

I had the privilege of hearing Peter Morris' design working while I was on a gig in Adelaide last week. Spectacular, just spectacular. If it holds it's pattern and tonal balance at high SPL, then this box is really something. In fact, it begs the question...why can't the big brands do this?
The stereo image was incredible, the tonal balance was incredible with a beautiful range. Well done Peter.
 
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