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Old 25th January 2009, 08:51 PM   #1
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Default a bass reflex using two fullrange drivers. A good idea ?


Afrench manufacturer commercialise a bass reflex box using two full range drivers fostex FE 103 ; one on the front and the other one at the bottom. they claim there is no filter in the box. According to them it's a good and simple solution to add bass to this smal drivers.

they got quite good reviews from the french version of "what hifi" magazine.

It looks like the solution used by the quite critized version of ambience bass reflex cabinet of common sense audio (they use one drivers at the top instead of the bottom)

Here the link (in french) (enceintes avant-scene soprano piano)http://www.ktr-lab.com/index.php?opt...d=80&Itemid=85

They also commercialise this horn using two FE208 sigma per enclosure, also no filter and one driver INSIDE the horn to add bass and have a better balance.

Does somebody on the forum has experienced some kind of enclosures like this (bass reflex) or some horn with an addionnal driver inside (so quite different in this respect to the horns like lowther academy using two drivers ) ?
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Old 25th January 2009, 09:03 PM   #2
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In essence, by downfiring the 2nd driver you are acoustically low passing itm so it is a 1.5 way,

My preference has been to make a bipole, but the way Cal dud it on his calhouns is very appealing.

As done in the BD-pipes it is also good... i am working on a box for 2 FE127 inspired by Bert's design.

community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
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Old 25th January 2009, 09:33 PM   #3
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I'm a huge fan of bipolar designs and can't understand why they aren't more popular. They have so many advantages over monopolar or dipolar designs that it's mind boggling.
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Old 25th January 2009, 10:25 PM   #4
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Originally posted by Saturnus
I'm a huge fan of bipolar designs and can't understand why they aren't more popular. They have so many advantages over monopolar or dipolar designs that it's mind boggling.
That could well be, but then perhaps domestic considerations are at play? Not all of us are fortunate to have complete carte blanche regarding aesthetics / placement of our speakers, or a dedicated room large enough to permit a bipole to fully blossom.
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Old 27th January 2009, 05:13 PM   #5
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so could we state that any bass reflex designed for a full range driver will be improved (in the bass sector) by adding a second driver ?

For exemple, if I take the bass-reflex box recommended by fostex for their FE206, it will have more bass and overall sound better ?
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Old 27th January 2009, 07:02 PM   #6
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Hi hornophile, in my opinion, two drivers in a single bass reflex (or sealed for that matter) is an excellent idea, with a big caveat.

The bass won't be deeper but it may seem a bit so because it will be /correct/. The second driver can easily compensate for baffle step. Then you can integrate a sub very easily in my experience.

There is a tendency to try to bring the sub up to correct for baffle step, and it's unlikely to work (in my opinion). That second driver (facing backward in my cabs) suddenly makes the bass much, much fatter and flatter. No more sag around baffle step. Go ahead and pull those cabs into the room.

Then when you try to integrate the sub, it will be easier to smoothly extend the bass lower. And you won't be mucking it up trying to get the sub to do your baffle step.

If you've ever spent days fidding with the crossover point and level, and never got it to lock in, my guess would be it's because that sag around baffle step was still there, doing its dirty work.

My test is upright bass -- can you hear every note plucked? Every note -- not a single note should disappear.

Regarding why it's not more common, doubling up on drivers is a brute-force solution. There are many more subtle ways of engineering a solution. I use cheap drivers so I just slap the second one on there (don't forget to double cab volume).

Then you face the decision of whether to roll the second driver off, or enjoy basking in the ambience of the rear driver's HF. To roll off, use a single inductor (thank you Bob for that one!) Or just have fun with all the reflections.

Lastly, I'm a newb so ask around before taking my word on anything. I'm basically repeating advice I heard, tried and liked.
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Old 27th January 2009, 08:14 PM   #7
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You will not automatically improve anything by adding a second driver (and as noted, you can't just stick another driver in the box -you'll need to double Vb for a start). We're in the realms of differences & preferences; however, done properly, you've certainly a good chance of reaping some substantial rewards. As far as FR drivers are concerned, given that they generally need all the help that they can get in the LF, doubling up on the drivers is only going to be a good thing (providing you design the cabinet / whatever properly). Bipole has its advantages if you like that sort of thing, have sufficient space & a room that will work well with quasi-omni radiation. Alternatively, if you'll be listening primarily in the farfield, having both units on the front baffle & rolling one off above its mass corner (or the baffle-step frequency; whichever you prefer) will also work well. Personally I like the latter, but horses for courses.
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Old 27th January 2009, 09:18 PM   #8
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Hi Scottmoose, I took the caveman approach and doubled up on actual cabs (a back-to-back pair for left, and another for right). It's very messy but the bass is (semingly) flat -- notes no longer go missing.
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Old 27th January 2009, 10:47 PM   #9
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Simple / brute-force is often the best solution. Look at the Ford GT40. OK, a very fine Lola chassis, but that 7 litre V8 found in the MK2 etc. isn't exactly going to find a place in the Big Book of Engineering Subtlety. All the better for it as well, as Ferrari discovered in short order.

Besides, they're were clever chappies, those cavemen...
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Old 27th January 2009, 11:11 PM   #10
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I think a dual small driver is an option.

You get double the area for cleaner voice, but vertical sweet spot (on 4" drivers with 5" frames) is about 2" at 12'. If that is not a limiting option.................

Also 2 drivers run wide open do not address baffle step.
My dual 4" with 8" wide baffle gradually wanders away below 800hz when run wide open.

I could run 1 as a baffle step or 1 on the backside for bipole setup....... but at $50 per driver, I think that is a waste of the neo magnet/copper shorting ring/bamboo cone.

I knew the limitations of a dual full range run wide open and worked around them.

I figure if it didn't work out, I could run 1 as baffle step and run a setup like von schweikert vr-6.

But I run my 12" under my speaker wide open also, that takes care of baffle step and goes way way lower than if I ran 1 of the full rangers as baffle step.

I've been tempted to run the stiffened poly Tang Band w4-1320 because 2 of those tune to 50hz (also near the f3) in a 1ft3 box. And you can get 4 of them for $100 from partsexpress.

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