# So what should I try to design?



## Luke352 (Jul 24, 2006)

Basically guys I have two sets of Mpyre 65m's here and I was thinking considering I'm not likely to use these in my car, since I'm half way through installing 8's well then I may aswell try to use them in a Home Audio design since they are basically Extremis 6.4/8's. So of I went looking to find a nice design that used twin Extremis per cabinet, and what did I find nothing! Sure I found a couple designs but most were simple 2 way designs that used a single mid per cabinet, and I'm really looking for something more then that.

So I figured well maybe I'll do some research and look to design my own. I'm sure my initial design and build won't be fantastic, but MDF is cheap and I can always improve on it. 

What I want is a nice floorstander that has a nice even response that can dig reasonably low but with a bit of EQ on the bottom end will really pound you for when watching movies. 

So I'm thinking a 2 way with two mids per cabinet probably wouldn't work that well since I would need a really high efficiency tweeter to keep up with the two mids, so I was thinking of either a 2.5 way design or a full 3 way design using a 4"-5" midrange.

So guys where do you think I should go, so far I've started to read all the links on the DIYAUDIO.com wiki.


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## Luke352 (Jul 24, 2006)

Well not much response to this thread, but guess i'll post up my preliminary rough design.

Uses twin Mpyre Audio 65m's which will have a final enclosure size of 50L tuned to 35hz, then i'll use MCA15RCY's for midrange 300-400hz up to 2500-3000hz and then most likely the Seas 27TDFC for the tweeter playing from 2500-3000hz up.

Xover design is going to be where I struggle but I do intend on using Zobel networks to flatten out any impedence rise, and i'll probably use Linkwitz-Riley 2nd order filter as my base design which no will doubt change as I tune them.

Anyway here are some drawings of the preliminary rough design.


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## Ga foo 88 (Dec 18, 2005)

They could be used with a 4 ohm mid/tweeter such as the chr70 from markaudio or the new el 70 from css.


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## Luke352 (Jul 24, 2006)

Yeah the reasons I went with the larger 5" mid was for the extra sensitivity to meet up with tweeter and the woofers that gain by the time you add 3db for two of them and then add another 3db for the vented alignment. But then when I add in the zobel networks to cancel the impedance rise and also take into account BSC corrections then the sensitivity's end up changing a bit anyway. Which I have to sit down and model it all out to make sure i'm not going to end up with too much difference. 

This is my first ever attempt at anything like this and it definitely has my brain spinning, and I have to drop some of it and just concentrate on one thing for a bit till I get my head around that. The problem is I can figure out each bit individually, but when it comes to integrating it all I get kinda lost. I'm sure it will all come together in the end, it's just going to take a bit. As I'm determined to have as little compromise as possible with this project. But I do want to stick with fairly basic cabinet design.


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## Luke352 (Jul 24, 2006)

Ga foo 88 said:


> They could be used with a 4 ohm mid/tweeter such as the chr70 from markaudio or the new el 70 from css.


I did think about that but decided against it for no particular reason, other then possible concern about lack of dynamic output especially when compared to the woofer section.


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## Luke352 (Jul 24, 2006)

Ok so here is what i'm pretty sure will be the final design, i've left the back panel off so you can see the bracing and internal structure better.

The lower chamber is 50-52litres once you take into account space taken by drivers, port, and bracing. The port (35hz tune) shown isn't to length it's just there for reference purposes. the upper midrange chamber won't be as deep as that as there will be another panel in it that reduces the depth to achieve a final volume of about 4.5-5L's and there will be a rear exiting port that will most likely be stuffed to make it like an acoustic vent, I stole the idea from this design, Poor Man' and if it works for him I have no doubts it's a proven technique. 

The small chamber at the base of the cab is for xover placement and I can also put some extra weight in the base if I feel it's necessary.

The actual depth of the whole cab once the rear panel is in place will be 35cm and it's 27cm wide, and the construction will be 25mm MDF, and the front edges will be rounded off.

Now I believe the next step is to order my drivers and take some t/s spec measurements free air as well as some FR measurements and then to build the cabs per this design (unless anyone can point out any flaws in the design, please do if you think I've made a big stuff up) and once I have the cabs built mount the drivers and start taking impedance measurements etc... so I can start work on the xover design, as if i'm thinking correctly impedance measurements should be taken with the drivers in there cab rather then free air, or have I got that mixed up?

Thanks again 

Luke









Shot at 2009-09-01









Shot at 2009-09-01









Shot at 2009-09-01


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## Luke352 (Jul 24, 2006)

OK the latest version, I've been posting over at Diyaudio aswell, and a couple guys were really nice to suggest some design changes and the reasons why, chances are the possible issues they pointed out may not have been an issue or rather my uneducated ears in comparison to some of these guys probably wouldn't have noticed. But since I want to do as good a job as possible with this, I've implemented the changes and I think it will be all for the better.









Shot at 2009-09-10









Shot at 2009-09-10









Shot at 2009-09-10


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## Austin (Mar 12, 2009)

So what is the different bracing going to do? is it supposed to diffract standing waves better or something?


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## Luke352 (Jul 24, 2006)

Apparently it's a much more effective method of bracing, plus the previous window bracing can be quite restrictive to air flow apparently.


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## SStealth (Oct 26, 2008)

Nice design Luke,

Hows the building going?

I'm doing something similiar with my 3 way set of sinfoni's i've got laying around.

Keep posting updates

Ant


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## Luke352 (Jul 24, 2006)

SStealth said:


> Nice design Luke,
> 
> Hows the building going?
> 
> ...



No building yet, I want to get the design well sorted before I place my order for material cut to size. Though I'm fairly confident this layout is essentially the final design. I've also decided I'm going to run it active with a Behringer DCX2496 and I'll make up a 6channel chip amp to power them. Reason being I think in the end it will be cheaper (Good passive aren't cheap!) and I can probably achieve better results active over passive when you consider my total lack of knowledge in designing a passive vs in comfort and ability using an active setup in car.


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## GPM (Sep 19, 2007)

Well, apparently I have to post to see the latest Klippel test results, so following up on one of my DIYaudio responses, I finally found an on-line copy of Olson's work on baffle diffraction for future reference, but posting a link sent this response to a mod for deletion, so trying again with a thumbnail.........

WRT porting, assuming the Mpyres, the vent required to have a low vent mach will be huge if much power is used (I assumed 300 W total or half the two driver rating) and short of stuffing it until it's effectively a sealed alignment will theoretically be required.

In such cases, a reverse tapered TQWT is my solution, but this will require an exit up at the top rear of the chamber, i.e. turn the whole chamber into a huge folded, tapered vent by using a solid panel horizontal brace that begins at the top rear and angled towards somewhere in the front half of the bottom, but cut short. This will require simming in MJK's MathCad software.

GM


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## Luke352 (Jul 24, 2006)

Well I had planned on using about a 4" dia port.

I had a look at MJK's MathCad Worksheet and that looks totally over my head. Not really sure where to go from here.


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## GPM (Sep 19, 2007)

Hmm, still haven't gotten an email notification.........

4" is way too small for 300 W. You can determine what's acceptable using any box program that graphs vent mach. You want < ~ 5% (17 m/sec) @ Fb.

??? They're plug n' play, i.e. just highlight the driver's individual specs except Qts and the cab design's individual dims and once you've changed all that's required, then depending on how the current sheets are set up (I don't have them) either just scroll down to initiate auto calculate or click the 'math' drop down menu and click 'calculate worksheet'.

This gets the basic info and you can ignore some of the plots, i.e. any that doesn't tell you its summed response, cone excursion, vent mach, etc.. Further down, you can define some aspects of boundary loading to get an idea how it might perform in-room.

Anyway, except for the much less user friendly AkAbak and an expensive program the name of which evades me ATM, it's the 'only game in town' for simming high aspect ratio cabs.

GM


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## Luke352 (Jul 24, 2006)

I'll download the mathcad sheets tonight if I get a chance (having a 1 month old in the house isn't leaving me much spare time in the evenings) and play with it all, I do have WinISD/s so i'll check the vent mach tonight as well.

Thanks again GM!

Luke


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## Luke352 (Jul 24, 2006)

Well I had a play with Vent air speed and I see where you are coming from, the vent mach does get very high. But I'm looking at all these TQWT on MJK's site and getting totally lost I'm having a hard time just trying to understand what each each style of QW enclosure is meant to look like internally.

Having read through some of the theoery and his application notes about the only one I think i'm capable of at this time is probably a simple folded TL. As for a TQWT or a reverse tapered TQWT (I can't even figure out what a reverse tapered one is meant to look like) I'm lost with these one.

I'm starting to wonder if maybe a sealed enclosure would just be simpler at this time, just means I end up with an f3 around 60hz (from memory) and about half my cab with a big empty space, guess i'd just fill it with sand.


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