First open baffle project

OK \
while I wait to accumulate funds for the big project I thought I would put together my first open baffle to see how they sound compared to a sealed box.
Searched thru the shelves in the garage and found some cheap drivers, I can't resist a bargain and these were $10 a pair, seriously not worth any more.
Using the published T/S parametres no realisable box would work so at a very high Q these should work in a flat baffle.
Started a thread in subwoofers but thats the wrong place,
Three and a half way, with the half in a sealed box rolled off very early first order'
So this is WW M T M W, Crossover is text book with listening changes, comment welcome as I have only a little experience developing x-overs, but I also used JBagby's excell work sheets.
This is a near enough good enough trial so not after perfection
 
OK access to Flicker files for open Baffle

http://www.flickr.com/photos/organize/?start_tab=one_set72157604464939012

I bought a "Jasper " circle jig from Soundlabs, makes things a lot more fun, but I need to write everything down as the router works better with 1/2 inch bits and I have cut a couple of holes far too big because my arithmatic was out.
The more clamps I seem to have the more I seem to need,
 
Hi gainphile, I saw those a while ago, have a pair of those cheap DS speakers myself, it's the pretend tweeter that lets them down.
I had a good tweeter cheap from a repairers surplus stock and tweeked the crossover on mine, BIG improvement
Just filled the box with polyfill tho, this experiment is my first real speaker in over a year and if I am really happy with imaging and overall sound I'll make the "Eathers"

http://www.diyaudio.com/forums/showthread.php?s=&threadid=117599
 
Here is a picture of the finished speakers.
http://farm4.static.flickr.com/3082/2684886778_ba0d885e65.jpg?v=0

Stupid beginners mistake made.

But I have a problem, in my haste to finish this project I have wired the 10inch 4R driver and the 2 X 8 inch woofers all in parallel and I'm presenting my amps with a 2 Ohm load which they do not like, I need to rewire but I lack the technical knowledge to calculate the correct inductor value to rewire in a cascaded topology, the 8's are rolled off at about 500 Hz with L/R2 2.65mH in series and 33uF in parallel and I have in mytoolbox some 5.6mH and 3mH coils.
What size inductor do I need to give me the boost at around 80 Hz?? and please direct me to any information so I can fill in the gaps in my understanding.
I must say I am impressed with the openness and depth of bass I have with this setup, especially when you consider the low cost of the drivers involved, $20 woofers and $7 midranges
 

ttan98

Member
2006-04-04 11:24 am
Melb
Moondog55 said:
Here is a picture of the finished speakers.
http://farm4.static.flickr.com/3082/2684886778_ba0d885e65.jpg?v=0

Stupid beginners mistake made.

But I have a problem, in my haste to finish this project I have wired the 10inch 4R driver and the 2 X 8 inch woofers all in parallel and I'm presenting my amps with a 2 Ohm load which they do not like, I need to rewire but I lack the technical knowledge to calculate the correct inductor value to rewire in a cascaded topology, the 8's are rolled off at about 500 Hz with L/R2 2.65mH in series and 33uF in parallel and I have in mytoolbox some 5.6mH and 3mH coils.
What size inductor do I need to give me the boost at around 80 Hz?? and please direct me to any information so I can fill in the gaps in my understanding.
I must say I am impressed with the openness and depth of bass I have with this setup, especially when you consider the low cost of the drivers involved, $20 woofers and $7 midranges

Nice photos you much have put a lot of work into building the open and closed baffle cabinets.

I am taking another approach which is alot quicker and does look as nice as yours, I spend more time experimenting with open and closed baffle. I also use DCX2496(US$250) so that I do not spend lots of time tweaking the passive x-overs and lots of cash on the passive components.

So far I have tried these configurations over the last 6-12 months,

a. TWW similar to emerald physics CS2 ,OB
b. MTMWW similar to GR research,OB
c. TW similar to Jazz module, vented enclosure
d. Full range driver in Martin King cabinet
e. TMWW similar to Jamo 909
f. TW in a cabinet, similar to JBL outdoor pro speakers
g. WMTMW to be done.

I have NOT published my results because the cabinets do not look attractive, also I am only experimenting with what are combos I like most. More importantly I can understand when people are building and talking about any one of the above configs.

In the end I will build one or more permanent pairs which I can live with.

cheers.
 
Hi ttan98, I could just put them together but I'm trying hard to improve my woodworking skills, as noted earlier i am thinking of using my Vifa P-13's in a clone of the "Eathers" and just seeing how an OB sounds I do like the mid-range, I'm going to make another pair soon using some surplus drivers that are much better than these, perhaps same configuration perhaps just a combination of only three drivers, the more drivers the easier it is to make mistakes I guess.
Don't worry about your woodworking skills; post your photos's; we just like to see what everyone else is building.
People are free to come round and comment and critique; just email me to arrange a time, we really do need to have a Melbourne get - to - gether like the crew is Brisbane
regards Ted
 
Hi Moondog, you could try a series xover;
In my OB WWMTM, I used 150uF in parallel with the two woofers;
these connected in series to the two Ms and 3mH in parallel and the T in series with 3.3uF. (LF Xover @ ~150Hz)

You could try various combinations of your 3 & 5.6mH coils to get the sound you want.

Judicious use of the bass tone control is a more efficient way of controlling lows, rather than huge inductors across your woofers.

Cheers,
Pete McK
 
I am thinking that if I just rewire the bass section as a nominal 8R load it will be close enough, experimented late last nite and the 5.6 coil in combination with a parallel cap of 10uF and that seemed to work.
The bottom woofer did not predominate as I thought it might, must be that change from 2Pi to 4Pi that gives the 10inch a presence without overpowering.
The bass these cheap drivers give in a small room is surprising, if I was allowed to buy more woofers ( WAF ) I'd consider another unit using Jaycars really cheap 12inch paper cone with a Qts of 1.46 they sound even more suitable for OB use.
 
I used a 12" jaycar and a 10" 'no-name' driver per side for woofers, 2x ancient 8" Magnavox for mids, and a EV 35T horn tweeter, wired as in post 15 above.
Baffle design is similar to the Visaton 'No-Box'.
2 are OK for bass (enough to get comments from the neighbours :D ), but go for 4 if you can afford it, nothing like surface area to make up for the OB's lack of efficiency...
 
Resurrecting this to comment about the driver selection I made.
I used some very cheap woofers and mid ranges, after finishing the crossover and tweking for a few hours listening I cranked the volume for a short while, "BBLAAATTT" a surround tore off one of the woofers and the paper was flopping around like a fish out of water. Thats what I get for using only 2 $20 woofers in an open baffle and a 200 watt amp.
The woodwork has a few resonce issues but too good to scap, I have some slightly better drivers here ( Jaycar 8inch poly cones) that seem to model OK if given a bigg enough box; try 10,000 litres, thought I'd try them but while they fit the cutout they do not fit the rebate.
I,m thinking I can fit them from the back of the panel; please comment on what happens if I round out the front of the hole with a router, does the air coupling become any more efficient?? or is a half inch round-over too small to have any effect??
One thing I keep learning is that is it is relatively easier to work with good drivers.
Peter I bought a quad of those Jaycar 12inch paper drivers and working on a cheap baffle as a gift for friends of ours, do you know anything about the Magnavox 8WR?/ I'm bidding on a pair in ebay at the moment thinking they may work well as the mid-top