Building a low-end sub for outdoor use

[CCU]

Hi all you wonderfull DIY'ers

I'm building a new and BIGGER setup for turing Denmarks festivals

The new one is quite large, 1 meter wide and 3 meters long.
I am building 2 DR 280 speakers from Bill Fitzmaurices website and i need 1 or 2 subwoofers to go with them. just to ad a litte UMF

Our old speaker setup used 8 Velleman VDSSP8/8 bas units and a couple of piezo tweeters. Velleman nv

I've been thinking about building a small horn for them. obviouslythere are NO designs for them, because they are ridiculously cheap/low-end

My question is. do you know of any design for a small'ish horn that those drivers might work in.

I've been thinking about building 2 of these, but 60cm wide, so that i can contain 4 units
Speakerplans.com

Will this give anything near a diesent performance,

I don't look for anything under 45hz of usable output, simply because it is a low power rig og outdoor

Would really apriciate some input for you guys

PS here's a picture of the old setup

An externally hosted image should be here but it was not working when we last tested it.

 

[CCU]

I've found more T/S specs for them than is listed on the website.

Impedance (Z) 8
Resonant frequency (fs) 35Hz
Max. frequency range f3-6,000Hz
Music power 350WMAX
Power rating (P) 250WRMS
SPL (1W/1m)Â 91dB
Suspension compl. (Cms) 0.25mm/N
Moving mass (Mms) 65g
Mech. Q factor (Qms) 4.95
Electr. Q factor (Qes) 0.66
Total Q factor (Qts) 0.58
Equivalent volume (Vas) 43 l
DC resistance (Re) 6,4
Force factor (BxL) 12.6
Voice coil induct. (Le) 0.8mH
Linear excursion (XMAX) ±6mm

And i have no idea of how accurate they are!!

 

[BP1Fanatic]

What is the Sd or hole cut out diameter?

 

[CCU]

The cut out hole i 17.6cm. if i understand the question.
The casket has a diameter of 20.5cm

 

[BP1Fanatic]

I've been thinking about building 2 of these, but 60cm wide, so that i can contain 4 units
http://www.speakerplans.com/index.php?id=hd15horn

You need to model it in Hornresp to see if 4 of those subs will perform with good results in that modified HD15.
http://hornrespdb.com/showparameters.php?id=105]HRDB - Hornresp Database

Horn Parameters
Ang : 1,0 x Pi Eg : 2.83 Rg : 0 Fta : 16.51

S1 : 544.8 S2 : 722.16 L12 : 27.38 F12 : 0
S2 : 722.16 S3 : 1054.92 Con : 15.25 F23 : 0
S3 : 1054.92 S4 : 1785.57 Con : 15.36 F34 : 0
S4 : 1785.57 S5 : 2206.16 Con : 8.97 F45 : 0

Chamber parameters
Vrc : 52 Fr : 40 Vtc : 20000
Lrc : 40 Tal : 4 Atc : 1982.4

 

[CCU]

thanks
I'm not really sure how to use that program, but i'll give a try

 

[BP1Fanatic]

The cut out hole i 17.6cm. if i understand the question.
The casket has a diameter of 20.5cm

Sd = 17.6 x 17.6 x 0.7854 = 243.29cm^2.

 

[CCU]

i think i've done it right

Multiplied the sd by 4 for the 4 drivers and added the volume to the rear champer

here's how it looks...

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[CCU]

for a low-end build i don't think i looks to bad with usable output to 40hz

 

[letsbangout]

When I was new to Hornresp, I also made the mistake of trying to derive new values for parameters like Sd, for example, by multiplying the Sd by the number of drivers. Hornresp works much better if you use the built-in Driver Arrangement wizard. Go to the Input Parameters, fix all of the parameters as they would be for a single driver, then click Tools and Driver Arrangement. Tell it how many drivers you will have in series, then how many of those groups you will have in parallel. You want to do it this way because the electrical parameters, for example, will determine the usable bandwidth and the upper/lower end of your design.

What kind of horn are you trying to design for these?

 

[CCU]

ohh thanks for the tip.

I don't really care what kind of horn it is. just like to have high usable output from 45hz to 100-200hz and will have to fit in a box of 60x60x60cm or less

 

[letsbangout]

I think you will be _extremely_ limited in what you can build with 60cm(3). At the very least, I think you will end up with 3 or 4 boxes which are something close to 60x60x60, and perhaps a bit wider. That's probably better anyway, since you will be able to stack them in a row next to each other like 1-2-3-4 for a wider effective horn mouth, and thus, better loading on the low-end. With those dimensions you are pretty much limited to either a scoop (back-loaded horn), or a tapped horn. Of the two, my preference is the tapped horn, because of the better response all the way down to the resonant frequency of the driver. If you're interested, I have another thread in this forum about Tapped Horn Theory and you can (probably) follow along with the tutorial and the questions/answers with pertinent information.

Good luck!

 

[BP1Fanatic]

+ 1

 

[CCU]

Okay, i'll just try the speakerplan box and compare it to my old box.
Se what i like the best.. because i really have no way of simulating any design, since i don't know who arcurrate the data are