604 in HUGE cabinets

[bowtie427ss]

There used to be a member here, Selmer Dave i think, who built 20+ cuft boxes for his 604's with very good results.

[GM]

Same problem. Low Q and big cabinet mean no bass. What's that the point of reaching to or below the Fs if you can't hear it?

That's fine if you are prepared to add EQ and run out of umph really quick.

Consider a normal sized cabinet and adding a woofer designed to do what you want. The 604's I know aren't designed for that.

These drivers were originally designed to be driven with a ~matching impedance, ~doubling its Qts which if done with the proper coupling results in a ~current driven system where the speaker?s frequency response ~ mirrors its varying impedance, ergo can have considerable LF efficiency if tuned to Fs in a sufficiently large cab.

If some form of EQ is used with a very low output impedance, then more power is required, though with an acoustically large cab?s extra tuning capability it can be better blended to the room?s gain curve, reducing power/excursion consumption.

With all that in mind, using GPA?s 604-8G II specs, a T/S max flat alignment = ~33.9 ft^3 net Vb/24.8 Hz Fb, but for most efficient electrical coupling it would have to be slightly under-damped with an actual Fs tuning. These tunings though would typically be too high and may even need to be sealed for best room blend.

The pioneers decreed that the ?best? vented alignment was a net Vb that increases a driver?s Fs 1.56x in a sealed cab, then vent it to an Fb = Fs alignment or ~ 11.35 ft^3 net Vb.

Of the two, the larger cab has a bit more output around/at Fs which may/may not be worth the all the extra size/cost to the builder depending on room conditions and whether or not it?s misaligned to a lower Fb.

FWIW, in my own builds/recommendations, I generally ?draw the line? at Vb = Vas in these situations as an acceptable trade-off or ~16.35 ft^3 in this case.

GM

[604man]

Consider mounting your 604's near the top of your cabinets, The center of my HF horn is 45 in. above the floor. See the photos in my post.
Let us know how the project is going.........GC

[tomt]

These drivers were originally designed

agreed.

originally the high efficiency speakers were driven by amps w/ low damping factors.

you know.

tube amps.

and some (amps) had variable damping factor adjustment controls.

so one might get some bass.

as the low efficiency/east coast/Boston sound came into vogue,

w/high damping transistor amps replaced most other amps.

and a high damped amp,

with high damped speakers,

makes little or no bass


since i've been reading Japanese stereo magazines

(not really read, i look at the pictures and schematics)

numerous articles, mostly in this magazine > ?A?C?G?[?o?? < - link


shows ways that several enthusiast have achieved bass in high damping speakers

those that use high efficiency speakers (and they are legion)

build their own amplifiers,

most are 1.5 watt, or near about variable damping amplifiers.

most are solid state.


the lower efficiency brigade, place motional feedback sensors in their drivers,

or build the drivers from scratch,