OB advice

[oublie]

Hi Folks,

I'm working on a set of open baffle speakers consisting of a pair of 15" subs , 6 mids in line configuration and a single tweeter per side. I've be playing around with these of and on for a while and will soon be building properly.

I've uploaded some pic including the edge response and the actual design. I'd appreciate it if someone could give me some advice on them. Am i on the right track or are there some points on which im way off.

Not there will be actively crossed and i should be able to even out the 2db bump in the mids with a band pass filter (i think thats the right term?)

Here are some pics and the xl baffle info.

15" skytronic qts 0.92


4" Wharfedale qts 0.52 picture with 0.25" wharfedale tweeter note the removable magnet on the wharfedale - this allows a certain altering of t/s parameters.



Edge response woofers (2) mid (6) tweeter (1) Physical design note the tweeter is slightly offset i may have to roll off the outer drivers at a lower frequency by i'm aiming for between 3 and 5 khz i'm think it might be possible to use a small horn to improve tweeter response i's fs is 1360 khz



ob design - My Photo Gallery
SUB MID
Driver Resonant Frequency (Fs - Hz): 30.00 90.00
Driver Electrical Q (Qes): 1.19 0.63
Driver Mechanical Q (Qms): 4.11 2.84
Driver Equiv Volume (Vas - liter): 178.00 3.20
Thermal Power Limit (P - VA): 250.00 75.00
DC Resistance (Re - Ohm): 5.80 4.80
Pk-to-Pk Excursion (Xmax - mm): 6.00 3.00
Effective Cone Dia. (D - mm): 320.00 75.00



sorry about pics - dodgy webcam used and some of my link might be a bit weird.

[sreten]

Hi,

The only thing I can say is thats the most bizzare OB design i've ever seen.
The narrow mid section and line array will not work well at all and you will
eventually rebuild them to something like a MTM at most with a decent
baffle width, and vertically stack the bass units for the tweeter height.

rgds, sreten.

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[cuibono]

Hmm, well, I think its doable. A few things though.

You didn't state where your XO points are. You are doing a fully passive XO? Do you have decent ability to sim the crossover, including the actual frequency response's of the respective drivers, on their baffles? Passives XO's like this are relatively difficult.

I would seriously caution you against relying on the edge and your woofer sim to come anywhere near the actual responses of your drivers on baffles.

Your line array will make sound, and may be acceptable - but it won't have a normal dipole or line array response. If I had to use all those drivers, I would try grouping them close together. You will have issues with any sound radiated with a wavelength half the distance of the furthest apart drivers.

But most of all, have fun!

[CLS]

This reminds me one of my previous thought (not identical but very close) and I'm glad someone is trying to make it real

Baffle-less Dipole Array

According to some OB line array builders (I don't remember the names, sorry), those lobing and interference etc sort of bad things are not so evident in real life while OTOH the benefit of arrays shines. So go for it and let us know how it goes.

The baffle holes have already been cut as seen in the picture, or I'd like to suggest naked drivers hung by wires

[oublie]

Thanks for the replies folks.

i've tried a bit of remodelling and come up with the info below this is based on vertically stacking the woofers and using a single tweeter and single mid.
The response in edge doesn't look as clean as with the 6 mids.

This is all going to be actively crossed with woofers running from 40hz to 200hz, mid/s from 200 to 300 to 5 khz depending on response and sound quality and the tweeter up from there.

As it's active i can choose between 1,2,4 and 8th order linear phase crossovers on the computer along with time delays shelving filters for any baffle step correction etc.

not sure if vertical subs make any real difference at least in the basic design done with edge. 6 mids do seem to even out the response over using just one although crossover frequency may have to be in the 2khz range due to combing. Of course theres nothing to stop me rolling of the outer drivers at say 1.5khz and running the centres to 5khz.

Apart from combing issues that may arise there doesnt seem to be any real benefit from changing to this design apart from a more 'normal design' lower crossover or rolled off mids and a physically smaller speaker which i don't care about. I think i might have to try both designs and see which i prefer.

Please note that the graphs have suggested baffle step compensation included and the subs have had bass drop compensation added.

[sreten]

Originally Posted by oublie

Please note that the graphs have suggested baffle step compensation
included and the subs have had bass drop compensation added.

Hi,

Your mid array will have baffle ripple and then baffle loss.
I cannot see how "baffle step compensation" is relevant.

rgds, sreten.

[oublie]

Streten,

Can you explain baffle ripple please not sure on that one. As for baffle step i added this as there is a rising response from 100hz up to around 1.5khz with a difference of 6db between 100hz and 1.5 khz by using baffle step compensation i guess i'm trying to tame the high midrange so it balances with the low midrange.

I should be able to get a fairly flat response across the mids by using compensation and dropping the high mids approx 2db.

Maybe i'm just way off with all of this?

Is it worth paying for a license for basta and modelling using it instead?

[StigErik]

It looks a bit - shall we say... DIFFERENT - but its not a bad idea, not at all! Narrow baffle is good for obtaining a good dipole radition pattern in the midrange. You might even consider dropping the mid baffle, and run the mid drivers nude.

[Rudolf]

Oublie,

Edge can only simulate the response of ONE driver SIZE on a specific baffle at a time. If you actually want to design and built anything, you urgently need a program which allows to consider real driver data and combinations of different drivers. Basta will do that or you might take a look at A_B_C_Dipole.

It is not only "worth paying for a license" - you will simply fail without it IMHO.

Rudolf

[oublie]

Have just ordered a license for basta, looking forward to getting stuck in and seeing the results.