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Old 4th March 2010, 07:31 AM   #1
alspe is offline alspe  Finland
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Default 2-way, small FR for mids+highs

Idea of slim floorstander with small full range driven quite wide band, say about 700 - 20000 Hz. Couple of less sensitive woofers added below baffle step frequency to compensate its loss nicely. How this sounds to you?

Fostex FF85K

Seas L16RNX/8

Maybe L16's can be connected 4 drivers (WWMWW), two in series and pairs parallel for 8 ohm and 6 dB sensitivity gain. L16 is low enough of its sensitivity and Fostex is enough sensitive that you can consider multiple woofers (which give great acoustical benefit in traditional room). Less dipping in bass and low mids.

L16 is rated 85 dB but graph says that it gives 83-85 dB in lower mids where it is used in this design.

For me, speaker would be used near walls and in bass boosting room so maybe I do not need full 6 dB baffle step compensation.
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Old 4th March 2010, 08:53 AM   #2
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A very similar concept discussed here: A thread for Tysen and variations on FAST

It works REALLY well.

dave
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Old 4th March 2010, 10:24 AM   #3
alspe is offline alspe  Finland
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Oh yes, I remember that design. Though I'm more interested of multiple woofer design which gives benefit for comb filtering in lows.

If Fostex FF85K is too sensitive for 4 x L16RNX (consider ** loss), Fostex could be changed for Mark Audio Alpair 5 which is 3 dB less sensivite. Maybe it isn't sensitive enough.
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Old 4th March 2010, 10:38 AM   #4
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When the goal is a slim design, you need a lot of woofers to compensate for their smaller Sd. If you use one or two woofers, they will need to move a lot of air, thus to have extended movement. This will lead to higher distortion and loss of dynamics and speed.
A bigger woofer is always better but if you go with a 22cm or larger, it can`t be used up to 700Hz. For a small woofer application, I would chose the 15W of Scan, at least 5 of them. If price is essential, the ER15RLY looks like a better contender, it has a lighter cone, it is non-coated and is not that sensitive so you can combine many of these with a single fullrange. First order network should be ideal of this driver if you crossover at 200Hz to a bigger fullrange. If you look at the small Fostex drivers only, on ebay you may be able to find the old Fostex FE103 with alnico.
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Old 4th March 2010, 10:49 AM   #5
alspe is offline alspe  Finland
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Bigger is better in bass but what about comb filtering I mentioned? If we compare 1 x 10" at 70 cm height to 4" x 5,5" small array, array will give much less comb filtering (floor cancellation) or said in other words it gives more bass because of lack of deep nulls in response.
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Old 4th March 2010, 04:22 PM   #6
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Quote:
Originally Posted by alspe View Post
Oh yes, I remember that design. Though I'm more interested of multiple woofer design which gives benefit for comb filtering in lows.

If Fostex FF85K is too sensitive for 4 x L16RNX (consider ** loss), Fostex could be changed for Mark Audio Alpair 5 which is 3 dB less sensivite. Maybe it isn't sensitive enough.
The concept applies with any number of woofers. The lower the XO the less issues with combing, driver separation. Also the lower you can cross, the more of that FF85 goodness you can take advanatge of. I'd discourage any XO much up into the telephone band, ie keep it to <400 Hz

If you can bi-amp, sensistivity issues become moot. If you want a passive XO, the woofers need to be about 3 dB more than the mid-tweeter (in most real-world situations).

I have drivers set aside with a passive XO in mind. FF85KeN + 2 SilverFlute W14 (14 cm). I'm likely going to push box width out to ~13" to get the baffle-step down to the 300 Hz region.

dave

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Old 4th March 2010, 04:42 PM   #7
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WRT comb filtering - combing only happens when the distances between drivers reach 1/2 wavelength. At 300Hz, wavelength is around 1m, so you'd need the woofers to be less that 1/2m away from each other.

Dave, it's interesting you should say about the woofers needing to be 3dB up on the mid-tweeter. With mine, the mid-tweet had to be 3dB louder. I expect it's down to listening distances (lots of woofers will project further than one small driver)

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Old 4th March 2010, 04:48 PM   #8
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3dB is the theory. We'll see how it goes when i start building... biamping is soooo much easier.

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Old 4th March 2010, 07:18 PM   #9
alspe is offline alspe  Finland
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Quote:
Originally Posted by planet10 View Post
The concept applies with any number of woofers. The lower the XO the less issues with combing, driver separation. Also the lower you can cross, the more of that FF85 goodness you can take advanatge of. I'd discourage any XO much up into the telephone band, ie keep it to <400 Hz

If you can bi-amp, sensistivity issues become moot. If you want a passive XO, the woofers need to be about 3 dB more than the mid-tweeter (in most real-world situations).

I have drivers set aside with a passive XO in mind. FF85KeN + 2 SilverFlute W14 (14 cm). I'm likely going to push box width out to ~13" to get the baffle-step down to the 300 Hz region.
Hi. Sorry for messing with these things (english is not language). I meant nulls that come of floor and ceiling cancellation, not comb filtering by another woofer. The higher XO the less benefit from multiple woofers? So I see it. Of course, wider band with full range is good, but it gives less room for multiple woofers to play better low mids.

Quote:
Originally Posted by chris661 View Post
WRT comb filtering - combing only happens when the distances between drivers reach 1/2 wavelength. At 300Hz, wavelength is around 1m, so you'd need the woofers to be less that 1/2m away from each other.
As above, I messed with these. 4 woofers would come around 30 cm distance. Nice up to 600 Hz.


Quote:
Originally Posted by planet10 View Post
3dB is the theory. We'll see how it goes when i start building... biamping is soooo much easier.

dave
Biamp is easy but it insists active xo of you want to do sensitivity changes. I don't do that. Just passive Cyrus setup.
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Old 5th March 2010, 08:09 AM   #10
alspe is offline alspe  Finland
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Quote:
Originally Posted by planet10 View Post
The concept applies with any number of woofers. The lower the XO the less issues with combing, driver separation. Also the lower you can cross, the more of that FF85 goodness you can take advanatge of.
Do you think that 120-150 Hz XO would best option (FF85 K handles that)? I think you are more full range / point source guy, not fan of arrays? (no offense in this).

To me, higher XO would be nice. You get acoustic benefit and more cleaner upper bass / low mids because of multiple woofer. And _more_ bass because of lack of deep nulls.

Is there going to be problems in directivity when changing small vertical array to point source full range in 500-600 Hz region? How tall (or short) woofer array should be?
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