My FR OB idea

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Ppasco1018

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#1
I do not know if someone has put this together before but. I figure I could have a crack at it. I am thinking of a OB FR set up consisting of.....

1 or 2 (don't know if 2 is overkill) 3" FR woofers on top
1 8" High Q woofer on bottom.

My thoughts on dimentions are....

Front baffle....24L by 18w
Side open walls 24l by 10w
Bottom support 10l by 18w

I would be putting some sort of dampening inside of the cabs.

I want to keep this on the super cheap. The 3" woofers are $11 each, and I would perfer not spending more then 25-50 per 8".

Anyone got any ideas on a decent sounding High Q 8" woofer for the price I am stuck on??
 
#2
The idea you're thinking of is FAST (Full Range And Subwoofer Technology), and is a good idea, as you take the crossover away from the sensitive 3kHz band which is where conventional 2-way speakers have their XO.

What FR drivers are you looking at?

Chris

PS - you (could) be looking at a Pro woofer for higher Q at 8" - something like the Eminence Beta 8 (tested on various OBs with some good results)

Good luck with the project!
 
#3
Not really sure. I think now I might be able to put a bit more quality into the factor as my budget got a little larger. I don't think I will be running a panel amp or a sub amp to the 8".

I was thinking something like the Audio Nirvana Super 8 but the Q is quite low.

What could I get with $300 driver budget thats good OB?

I think I want one 4" and one 8" per OB.

Thanks!
 
#5
#6
My experience is a single 8" woofer is not going to be useful for OB.
You would be much better served with a high Q 12" or 15" driver.
I user a couple of 12" no name buyout drivers and a NSB 4" with great results.
There is a great design floating on the board using the Eminence Alpha 15 and a full range driver.
http://www.diyaudio.com/forums/full-range/108751-new-mjk-baffle-article.html
I would not use two 3" unless you are going to use a tweeter, because of lobing.
You're idea is good.
Good luck.

Doug
 
#9
huh. Well thats no good, the Q on the 8 was .7 i belive. I am not a big bass head so if this is a bass extention issue I could live! At $10 a pop honestly could you complain?

Is there a fostex driver thats good for OB?

Since I am planning on using a larger woofer with higher Q, does the smaller woofer need to adhere to this?
 
#10
The jamo 6.5 is Q 1.28. Would that at least extend omph with the regular driver. And since they will be ran together, will this fix the somewhat low SPL? I figure it couldnt be that bad.

A Audio nirvana 6.5 and the jamo 6.5? That would be quite cheap to put together. A good first take no??
 
#11
At $10 a pop honestly could you complain?
Click to expand...
It will sound fine. The issue is that the baffle roll-off is 6 db per octave starting at Fequal. If your baffle Fequal is 120 Hz, (just a WAG) you either are 6 db down, need twice the Xmax, or twice the area at 60 Hz. There are spreadsheets that calculate max spl. Run the numbers, but my intuition is that a 40 Hz base note could bottom the woofers at any reasonable volume. I had to keep the crossover point up (above 200 Hz) to avoid bottoming the mid-range.

If you try it, let us know. As you say, the price is right.

Doug
 
#12
I shall. There will be pictures and all!

I want to sand and gloss black/red what ever gets built. So it will be while before they are done.

I think I am going to buy a pair of the little $10 3" and build a little MDF home for them to tinker around with in the bedroom to see how interesting the full range thing can be before I spend over $100 dolla!

Does anyone know how much mdf for my size will be.

I would say 30f by 20w FB / Small same height arms?
 
#13
Ppasco1018 said:
snip...

Is there a fostex driver thats good for OB?
Click to expand...


Well, if you read the MJK project paper referenced earlier, you'll see he nominates a range of Fostex drivers for the mid/tweeter portion of his 2-way OB.

There are more than a few builders who've been very happy with the results. Probably most effusively - Jim Shearer and his FF85K - see his posts starting about here:

http://www.diyaudio.com/forums/full-range/108751-new-mjk-baffle-article-48.html#post1931872

Mind you, any of the suitable Fostex drivers will cost more than $10 each
 
#14
Today i received the 5.5" jamo and the 8" jamo from PE... They look great in the pictures but not so great in person... plasticy and lightweight. Every single Fostex i have seen simply looks and feels better made. Every single TB i've seen looks and feels better made... I remember getting the titanium 3" TBs and couldn't wait to hook them up. Just looking at these jamo's i don't even want to hook them up. They look like they will break if i turn up the volume. Uhg... oh well, they only cost a few bucks.

Godzilla
 
#15
I figure it would be a start though. I bought a pair of those insignia ns-b2111's today just to tide me over until I had the time to start building my OB's. Dear lord they sound fantastic at low levels (cost wise-paid $60) but once you crank up the levels the thin box really shows. I think I am going to do the rock hard mod to them and shove a 6.5 full range in them until I get the time to build the OB's. I think I am stuck on a 6.5 and a 8 or 10" for the OB.

I did a paint draw up of what I sort of want them to look like in the end.

Tell me what ya think!
 

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#17
Cool. This box is real flimsy. Its only 5 dollars to add the rock hard and maybe two days of my time. I have the slightest clue how to do crossover stuff.

Is this a simple upgrade? Thanks for the tip, I can def afford $40 to make a better speaker. As when the OB's are done, the FR will be removed from this box and will need to be put back together with the original driver.

Does anyone know what kind of crossover I would have to widdle to use those drivers in my car until I put them back in later on? I would figure it would be a small filter??

Thanks guys, your nothing but help!
 
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