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Old 19th February 2013, 11:09 AM   #1
soren5 is offline soren5  Denmark
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Lightbulb miniFAST Boombox Build

My friend and I have been thinking about this idea for a while and the other day we made some test builds. The idea is small active 2.1 boombox using two fullrange drivers and a (sub)woofer. The objective for this project is a small box with as much low extension as possible. After trying different drivers we settled on the Fostex FF85WK as fullrangers and a TangBand W6-1139SIF for bass duty. Crossover is in the 250-300Hz area. For amp we use the Hifimediy DDX320v2 2.1 Digital Amplifier with a Connexelectronic SMPS300R 38V.

Here are some pictures of the test build using some leftover 15mm BB ply. The fullrangers are each in their ~1.5 liter sealed chamber, 75% stuffed. The woofer is in a 11.5 liter BR enclosure with a 50mm port tuned to 35Hz.

The DDX320v2 has an adjustable electronic crossover, which can be set between 80-360Hz, we settled on 280Hz. It uses a 2nd order low pass and 1st order high pass

So how does it sound? Okay I would say, but not amazing! We made a comparison with some budget 2-way bookshelves, the Dali Concept 1, placed very close together to be fair Our boombox surely wins on the low frequency extension, but it isn't as "clear", "open" and "crisp" as the Dalis.

This is of course only a test build. We haven't measured it yet, and no EQ or time alignment has been applied so far. Filter options are very limited with the DDX320v2, but we also have a miniDSP and various amps so we can experiment.

Thoughts and ideas are greatly appreciated!
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Old 19th February 2013, 11:35 AM   #2
mortron is offline mortron  Canada
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On the cheap, you could add some top end with a pair of cheap apex jr tweeters or something.

Looks cool. Been pondering something similar.
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Old 19th February 2013, 06:21 PM   #3
soren5 is offline soren5  Denmark
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Quote:
Originally Posted by mortron View Post
On the cheap, you could add some top end with a pair of cheap apex jr tweeters or something.

Looks cool. Been pondering something similar.
Thanks for the input. Wanted to keep it as simple as possible, so adding another set of drivers doesn't really appeal to me. But might be worth a try if the DSP tweaks won't help.
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Old 19th February 2013, 07:42 PM   #4
IG81 is offline IG81  Canada
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Quote:
Originally Posted by soren5 View Post
So how does it sound? Okay I would say, but not amazing! We made a comparison with some budget 2-way bookshelves, the Dali Concept 1, placed very close together to be fair Our boombox surely wins on the low frequency extension, but it isn't as "clear", "open" and "crisp" as the Dalis.
Very cool project!

Maybe you need to give the FF85WK some time to break-in, not that I noticed that huge a difference on my pair. OTOH, maybe the FF85WK is just bringing to light what are actually flaws in the Dali speaker. The little Fostex is a very good little driver and relieving it of bass duty as you did is probably the best thing you can do to it. This could be a pretty hi-fi lil' box!

Maybe that 6" sub is kinda "slow" and does not convey tuneful mid and upper bass? Not to mention that it is trying to reproduce the lower voice registry. The Peerless NWR1643308 6" midwoofer could work in this volume with a much larger and shorter vent for increased vent efficiency. It would not go as deep, but give f3~50Hz with probably much better quality upper-bass and lower midrange. You'd have more play room on your active crossover to experiment as well.

IG

Last edited by IG81; 19th February 2013 at 07:50 PM.
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Old 19th February 2013, 07:52 PM   #5
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Quote:
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On the cheap, you could add some top end with a pair of cheap apex jr tweeters or something.
The FF85wk goes upto 25k with excellent fidelity, a tweeter would just muddle things up.

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Old 19th February 2013, 07:53 PM   #6
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Quote:
Originally Posted by soren5 View Post
We made a comparison with some budget 2-way bookshelves, the Dali Concept 1, placed very close together to be fair Our boombox surely wins on the low frequency extension, but it isn't as "clear", "open" and "crisp" as the Dalis.
With the same amp?

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Old 19th February 2013, 09:38 PM   #7
soren5 is offline soren5  Denmark
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With the same amp?

dave
No, the Dalis had an old Sony solid state while our "boombox" was on the DDX 2.1 amp. Tomorrow I'll try with my miniDSP, using the Sony for the Fostex and then a TK2050 amp for the bass. This will also give me many more filter possibilities.

I also want to put a microphone on it to see how it measures.
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Old 19th February 2013, 10:18 PM   #8
soren5 is offline soren5  Denmark
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Originally Posted by IG81 View Post
Very cool project!
Thank you!

Quote:
Originally Posted by IG81 View Post
Maybe you need to give the FF85WK some time to break-in, not that I noticed that huge a difference on my pair. OTOH, maybe the FF85WK is just bringing to light what are actually flaws in the Dali speaker. The little Fostex is a very good little driver and relieving it of bass duty as you did is probably the best thing you can do to it. This could be a pretty hi-fi lil' box!
The Fostex have had some break-in. I bought them months ago and have been using them for other projects. And I agree, they do sound very good compared to other full-rangers I've heard in similar size. However, it doesn't appear to me that the Fostex are "bringing to light what are actually flaws in the Dali speaker" as you say. It rather feels like the sound "opens up" when I switch from the boombox to the Dalis.
I've had this idea of making a tapered TL style chamber for each of the Fostex, inspired by Planet 10's Tysen. Do you think this will affect the sound much compared to our current 1.4 litre sealed enclosure with stuffing?

Quote:
Originally Posted by IG81 View Post
Maybe that 6" sub is kinda "slow" and does not convey tuneful mid and upper bass? Not to mention that it is trying to reproduce the lower voice registry. The Peerless NWR1643308 6" midwoofer could work in this volume with a much larger and shorter vent for increased vent efficiency. It would not go as deep, but give f3~50Hz with probably much better quality upper-bass and lower midrange. You'd have more play room on your active crossover to experiment as well.
Maybe this yes, but it just sort of defeats our objective to have deep bass from a small enclosure. I could of course also just use two sets of small 5" midwoofer + tweeter and and have a more traditional 2-way stereo boombox (another project actually ). It could probably be even smaller, though it wouldn't go as deep, but sure as loud as the our current miniFAST.
I didn't think the W6-1139 had problems if kept under 300Hz. Maybe I should try cutting lower and with a steeper XO. I also wonder how much phase and time-alignment matters as this has not been looked at yet.
By the way, which Peerless are you referring to? Couldn't find that model number you wrote.
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Old 19th February 2013, 10:37 PM   #9
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....Do you think this will affect the sound much compared to our current 1.4 litre sealed enclosure with stuffing?...
Yes.

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Old 19th February 2013, 10:41 PM   #10
soren5 is offline soren5  Denmark
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Yes.

dave
So when you say "yes" I assume you mean for the better? Could it be that the FF85WK simply don't behave very well in a sealed enclosure?
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