Compact FAST / WAW design

[rho]

I'm looking for a compact F.A.S.T. design. Something with a 6.5" bass driver and a 3" or 4" FR would fit my needs best I think.
I'm looking for a stand mounted speaker with maximum dimensions of about 25cm (10") wide, 45cm (18") high and 35cm (14") deep.
Anyone build anything like this?

Something with an SDX7 and FR125 would be very interesting.
But other design are very welcome too, obviously.

 

[planet10]

SDX7 + FF85. Alpair 6 or Fountek FR88 or other 3" could be substituted.

http://www.diyaudio.com/forums/full-range/144099-thread-tysen-variations-fast-4.html#post1833349

dave

 

[rho]

I have read trough the Tysen thread already.
That's a nice design, but I'm a little afraid the -3dB on the SDX7 will be a little disappointing in such a small sealed box.
Does that config even work with a passive x-over? (don't have 4 amplified channels (...yet?))

 

[audiobomber]

Alpair 5 and SDX7, ported box
Alpair 5 / SDX7 Team | Markaudio

JX150NG and JX6HD closed box
http://www.ejjordan.co.uk/articles/JX150_and_6_closed_cabinet.pdf

I'm interested in seeing what else comes up in this thread.

 

[planet10]

the -3dB

You can always make the box bigger.

F3 is without menaingful correlation, look at F10. If you want a small box you will have to give up ultimate extension (Hoffman's Iron Law, extension, size, efficiency, you can only pick 2)

dave

 

[rho]

Yes, I kow there are limits to the bass extension in a smaller box. But 15 liter or a little more should be possible.
Why do you think F10 is telling more then F3? Does that have to do with room-gain?

Alpair 5 and SDX7, ported box

Now that is really interesting!

 

[chrisb]

I have read trough the Tysen thread already.
That's a nice design, but I'm a little afraid the -3dB on the SDX7 will be a little disappointing in such a small sealed box.
Does that config even work with a passive x-over? (don't have 4 amplified channels (...yet?))

to answer the second question - at the XO employed in the Tysen ( circa 300Hz), passive high level would certainly be possible, but it's not hard to imagine that the cost of parts could be greater than the drivers, and their dimensions not tiny either


for example, the Jordan 2-way calls for 100mF HP cap to JX6, and the Mark Audio design's more flexible "anywhere from 200 to 5kHZ" ( personally I wouldn't waste the wonderful lower mid-range & upper mid bass of the Alpairs by crossing over any higher than 300) could range in values from 200mF on HP for 1st order to approx 100mF & 50mF plus chokes for 2nd order

altogether a very good justification for line level and active amplification, and how many of us don't have at least one ole SS amp or receiver lying around that wouldn't work for at least proof of concept on the woofers?

 

[planet10]

Yes, I kow there are limits to the bass extension in a smaller box. But 15 liter or a little more should be possible.

Tysen is 17 liters. Once you get over ~14 litre stuffing can have greater effect than extra volume. 21 litre effective volume (Q = 0.5) is as large as you want to go

Why do you think F10 is telling more then F3? Does that have to do with room-gain?

This is from Toole (Sound Reprodiution). F3 did not correlate with jusgements of extension of bass. He does have a tested metric that is (i'd have to go look it up)

dsve

 

[rho]

From other topics I noticed you prefer using the SDX7 in a sealed application. (and some disagree)
I intend to get as much bass-extension out of a small speaker and I'm not looking for an high SPL application. (I use a 6.5"mid-bass now with much less Xmax and never ran into problems)
I realize that the extra bass-extension comes with higher requirements towards Xmax, but I think the SDX7 has plenty.

Would a BR application be a good option in this case and if so, how much could I win going that route?

(in the meantime I'm considering a MiniDSP and fixing my chip-amp to go active)

 

[chrisb]

From other topics I noticed you prefer using the SDX7 in a sealed application. (and some disagree)
I intend to get as much bass-extension out of a small speaker and I'm not looking for an high SPL application. (I use a 6.5"mid-bass now with much less Xmax and never ran into problems)
I realize that the extra bass-extension comes with higher requirements towards Xmax, but I think the SDX7 has plenty.

Would a BR application be a good option in this case and if so, how much could I win going that route?

(in the meantime I'm considering a MiniDSP and fixing my chip-amp to go active)

SDX7's X-max is not unlimited, and you'll definitely hear when it's exceeded. It's major appeal for us is the performance possible in very small sealed enclosures, which particularly suits applications like the Tysen, or multiple woofers for HT systems.

 

[planet10]

Chris touched on our use of SDX7. The SDX7 gives no warning of running out of excursion. You just get a very disturbing "fart" when the voice coil hits its stops. To avoid this one needs to use a sealed box, an aperiodic box (the TL we built had to get stuffed to aperiodic to avoid the ugly noises, or you need to actively filter below the tuning frequency of a "vented" box.

Remeber that when you look at how loe a woofer goes F3 is mostly meaningless, F10 is much more significant, and things will sounf better if the slope of the roll-off more closely matches the room gain,

dave

 

[rho]

How big was the room and at what SPL did you get the bottoming-out of the driver?

Do you know what the F10 of an SDX7 in a 15 liter box is? (I migrated to linux, still need to find some good simulation SW)

 

[planet10]

We have no issues with SDX7 bottoming when sealed. My room is pretty large, the amp we were using was running out before the speakers, max levels were louder than i usually listen to (bit not really really loud).

14 litre sims as Q = 0.58, F3 ~ 70 Hz, F10 ~ 33 Hz

The chart is from the SDX7 sealed doc, 3.5, 7, 14, 21 litre, Q = 1.0, 0.707. 0.58, 0.5

dave

 

[rho]

Thanks for the info.
I think I'll have to put the SDX7 at the top of my shortlist then.