FAST subs under MA drivers

[chrisb]

Originally Posted by soren5

I subscribed to this thread as I'm currently looking for some drivers to add some bottom to my Alpair 7.3s.

One of my objectives is to build a small sized FAST system. I've been looking at various drivers, but is currently set on the TB W6-1139SIF. I've never used these drivers, but I hear good things about them. In a small vented cab with a bit of EQ these little subs should reach an f3 of 30Hz (relatively big and long vent required but doable). From other threads I hear that they play well up to around 600Hz.

The idea is to put the Alpairs in a small sealed cab and cross at something like 250-300Hz using miniDSP.

Comments appreciated.

While a 5.1/etc HT system is not exactly a FAST configuration, it does allow experimentation with different driver / enclosure types at each location. My early trials of dialing in current rig took the opposite approach (i.e. multiple small sealed SDX7 woofers and vented mains and center) . Perhaps the lower XO points employed ( circa 100 or so) are at play, but I found the combination of sealed and ported simply didn't integrate as well as did later all vented enclosures - Alpair7s in the front row, and dual 8" OEM (Eastech) corner located woofers.

My only exposure to integrated FAST systems were the little 2-way Tysen with sealed SDX7 and small highly damped TL with Fostex FF85K, biamped at approx 330Hz - the XO transition was fairly innocuous; and a Lowther/Tone Tubby(?) OB at an audio show. The latter system not only kicked a$$, but would also tear your line of credit a new one.

[planet10]

Originally Posted by silverhairbp

There are as many octaves below 120hz as there are above 120hz.

Bill, old age must really be creeping up on you. below 120 Hz is ~ 2.5 octaves... 120 Hz plus 2.5 octaves is response up to 640 Hz.

20-40
40-80
80-160
160-320
320-640
640-1.28 kHz (some rounding usually happens here to make things fit)
1.25-2.5 k
2.5-5k
5-10k
10-20k

My goal with helper woofers is to try to get to 25-30 Hz F3 which is close to Bills 20 Hz F10.

To really get the ommff to do those organs and really dynamic drums, one needs to look at a set of subwoofers <50 hz placed in the room to counter the major resonces (i am sitting on 4 SDX10 to slot in below the 8 SDX7 )

dave

dave

[vinylkid58]

Originally Posted by planet10

My goal with helper woofers is to try to get to 25-30 Hz F3

That's what I thought.

jeff

[soren5]

Originally Posted by chrisb

Perhaps the lower XO points employed ( circa 100 or so) are at play, but I found the combination of sealed and ported simply didn't integrate as well as did later all vented enclosures

So are you suggesting that general speaking sealed goes with sealed and vented with vented, but you shouldn't combine? It never occurred to me that this would be an issue. Considering that there are many ported subs out there, which have been successfully mated with existing setups (sealed or vented), I would think that a combined sealed+vented FAST system wouldn't be a problem as such.

Mind you, I still have little practical experience in the field of speaker building, so I really appreciate all kinds of inputs here

[tuxedocivic]

Originally Posted by chrisb

Since you ask "why" - for me FAST is about reducing distortion and improving midrange dynamics and resolution/inner detail , and while not highest on my priority list, increasing attainable SP levels.

Ah, an excellent point. One I've used myself, but obviously overlooked it in this discussion. Thank you.

[silverhairbp]

Originally Posted by planet10

Bill, old age must really be creeping up on you. below 120 Hz is ~ 2.5 octaves... 120 Hz plus 2.5 octaves is response up to 640 Hz.

20-40
40-80
80-160
160-320
320-640
640-1.28 kHz (some rounding usually happens here to make things fit)
1.25-2.5 k
2.5-5k
5-10k
10-20k

My goal with helper woofers is to try to get to 25-30 Hz F3 which is close to Bills 20 Hz F10.

To really get the ommff to do those organs and really dynamic drums, one needs to look at a set of subwoofers <50 hz placed in the room to counter the major resonces (i am sitting on 4 SDX10 to slot in below the 8 SDX7 )

dave

dave

Dave,

Your goal is very much aligned with mine. I prefer sealed box designs that provide a more gradual rolloff but accomplish the same result. It also makes the cabinets a bit more simple to design and implement. When someone has my level of cabinet building skills, a sealed box is about the limit.

Below 120hz there's 60, 30, 15, 7.5, 3.75, 1.875, .99, .495.... etc. out to an infinitesimally small number. This results in the same number of octaves below 120 as above. Infinity.

I would expect 4 x SDX10 would provide reasonablly deep performance in the right enclosure. The swept area is a little bigger than what I'm currently using for deep bass.

I'm still using a pair of Nick's old Lambda SB12s each in around 4 a cu ft sealed box. Properly placed at the midpoint of the long wall, they go too deep for me to measure (I can only measure to 20hz) and pretty much take care of any deep stuff I can throw at them. But they are positively awful at higher frequencies. Low order crossovers are totally out of the question, fourth order active crossover and bi-amping is needed at a minimum.

Below a certain point, room and speaker placement come heavily into play in terms of how to get deep bass. Though a nice array of large drivers helps, sometimes it only takes a bit of extra room boost to get satisfying results.

[silverhairbp]

Originally Posted by soren5

So are you suggesting that general speaking sealed goes with sealed and vented with vented, but you shouldn't combine? It never occurred to me that this would be an issue. Considering that there are many ported subs out there, which have been successfully mated with existing setups (sealed or vented), I would think that a combined sealed+vented FAST system wouldn't be a problem as such.

Mind you, I still have little practical experience in the field of speaker building, so I really appreciate all kinds of inputs here

I have had little success in mixing sealed systems with ported systems. The phase is severely lacking in whack if not completely out of whack.

[jimbro]

How about mixing blh with ported? In whack or out?

[silverhairbp]

Originally Posted by jimbro

How about mixing blh with ported? In whack or out?

Not sure (what's blh?). I've only tried to mix tuned port enclosures with sealed with unwhacked results.

[planet10]

I've had good results mixing aperiodic (or near aperiodic as in the miniOnken) with sealed, with aperiodic, and with TLs.

dave