Found a great little bass extender

[rabbitz]

I've placed this in the loudspeaker forum as I thought this could benefit a lot of loudspeaker builders. This circuit is available in kit form at this site.

I was looking for something to add some lower bass to a large pair of bookshelf speakers (Peerless 850122 woofers) that's used secondary system. The idea was to have extra extension when playing some DVD's with good musical soundtracks (not action flicks as there's a HT setup for those). The system does not warrant a small sub, even though it had one in the past that was rarely used, so this seemed a good solution. Bass extenders I have heard in the past tended to sound like a bad loudness button.

The BassXt was first tested with a small loudspeaker that's in an undersized box where the F3 is 62Hz but 48Hz in the correct size box. The woofer is the PAE 14WG08 (Vifa BC14WG49-08) which has limited power handling so would be a good candidate to see if there would be any over driving. Not only did the BassXt restore the lower end bass, it improved on the larger box extension as well as controlling the woofer better. There were no crazy excursions and it was very well controlled. So the bass went lower and the power handling capabilities went up. The tonal quality of the bass was very good (depends on the driver of course) and natural with no boom or one note qualities. The same happened when tried with the Peerless 850122 woofer design and the F3 went from 47Hz down to well below 40Hz which is enough to enhance the selected movies where I wanted better bass from the soundtrack. This speaker now sounds more like a floorstander with a fuller sound in the bass.

In these speakers, it was not implemented to replace a subwoofer, but to extend and enhance the bass capabilities that were already there. I'm sure that port tuning (lower Fb) to give a under damped response would have even more gains but no port re-tuning was done during my tests and final use.

The circuit and layout is extremely simple with a 12VAC (plug pack) in, power switch, in RCA and out RCA. In the final application it's placed in the tape circuit so hitting a monitor button on the amp will put it in or out of the signal path. In the first test it was placed between the CD player and the pre amp but one will be built into the pre amp so it can be switched in as required.

I am not affiliated with the designer but I got quite excited with the results so thought this could be a great solution for those looking for a bit of extra bass extension. It worked out cheaper than a small woofer and the box was built from scrap material.... woohoo.

[rabbitz]

Made from scrap material and am stoked with the results sonically and visually.

[tinitus]

Interesting ...... could you please tell about the controls, how they work

[rabbitz]

There's some info on it here.

Each pot does the adjustment of a 6dB peak between 20 - 50 Hz on each channel to restore the F6 to flat. As the pot changes position, the resistance is changed and alters the active filter network. There is a steep sub-sonic filter that works in conjunction with this to stop the driver going nuts with too low frequencies.

[sreten]

Hi,

To make it more flexible you should tune ports lower when using
such a device, though it should be fine with sealed boxes.

The whole thing can be modelled in WinISDPro.

/sreten.

[Andy G]

But Peter, if you built the cabs the right size in the first place ;-)))))

[PeteMcK]

I think this is probably a good alternative to the Linkwitz transform circuit? Someone posted circuit details of a similar unit here on DIY Audio (maybe the same one?)
I think this unit would be good for cheap guys like me, who have drivers with large Vas, but don't want to go the expense & effort of building large cabs (but you knew that already, eh Andy...) e.g. I have a pair of Peerless 840146s which have Vas of 144 L, currently in 40 L cabs. For me it's a lot easier to make a small circuit such as Greg's than to build 90-120 L cabs (OK, my woodworking ability sucks too...)
cheers,
Pete McK

[Spasticteapot]

Yet another reason why my next pair of speakers will have an active crossover, and be bi-amped.

(I also found that LM3875's are now cheaper than most good-quality inductors - and, if all else fails, paying $50 for the 41hz Amp9 will give you four channels in a tiny package.)

[richie00boy]

I would not say this circuit is suitable for too-small closed boxes, as unlike the Linkwitz Transform is does not correct the large resultant peak in response, in fact it would probably add to it to a degree.

[freddi]

very nice for our old friend the assisted 6th order reflex - some cases just step down Fb by 1/2 octave..

can it be purchsed with box and jacks?