Looking for active bass equalisation - Any equivalents to "Golden Flutes" ?

[clubsport911]

I am considering active bass equalisation - the kind of device like the (now obsolete ?) Golden Flute. These are fitted between pre and power amplifiers with the specific aim of providing low frequency extension / boost.

I'm aware that these (Golden Flutes) are now out of production, but has anyone got any recommendations for similar devices I can obtain to achieve the same effect ?

Happy to DIY [to a certain extent] No effect above 100hz required (or even 60 to be honest !)

Thanks

 

[rcw666]

I have had a bit of a look on the net and can't find reference to the golden flute, exactly what did it purport to do?
rcw

 

[clubsport911]

The GF sits between pre and power amp and added a carefully engineered amount of low frequency equalisation. It did this with ( In theory) no effect to upper bass, midband or hf.

It was possible to adjust extension, curve and point of operation.

Interestingly, I only heard about these a few weeks back and found information pretty quickly !

In summary, it's a very high quality LF only tone control.

 

[Draki]

Maybe this: subwoofer equalizer, bass correction equalizer, bass boost

 

[ashok]

Allison seems to have had a similar device. It was called the Alison Electronic Subwoofer. I've heard one with an Allison speaker. Went quite low but didn't have 'slam' !
You could rig up a Linkwitz transform circuit.
Look here for the theory and the project and a spreadsheet for calculations.

ESP - The Linkwitz Transform Circuit
Linkwitz Transform Subwoofer Equaliser

 

[ashok]

Check this link for the Allison Equaliser . Scroll down .

http://www.roger-russell.com/equalizers/equalizers.htm

 

[phase_accurate]

The "Bassis" thing is actually something like the Linkwitz transform with adjustability via pots.
The main use of the LFT is closed boxes. There are of course other schemes as well like shelving filters, parametric EQ, Highpass filters with a hump etc.

The highpass for instance can be of advantage when protection from overexcursion is higher on your list than group-delay distortion. I once derived a circuit that did dynamically alter the height of the hump and the cutoff frequency.

Regards

Charles

 

[weltersys]

The GF sits between pre and power amp and added a carefully engineered amount of low frequency equalisation. It did this with ( In theory) no effect to upper bass, midband or hf.

It was possible to adjust extension, curve and point of operation.

Interestingly, I only heard about these a few weeks back and found information pretty quickly !

In summary, it's a very high quality LF only tone control.

What you describe and far more can be done with the MiniDSP, or most any DSP (digital signal processing) unit.

By inserting the DSP in a tape loop available on most receivers, separate power amps for the bass are not needed to effect the change.

 

[rcw666]

Perhaps you can indicate what sort of a set up you have.

The difficulty with and equalization of this sort is that you can very quickly run out of cone excursion and amplifier power.

Just taking any old thing and boosting the bass to fix it doesn't work very well at all. rcw

 

[clubsport911]

Perhaps you can indicate what sort of a set up you have.

Sure... I have a 400W MF amps (40A current output continuous), MF Pre-amp and KEF 105/3's. The 105/3's are bandpass Coupled Cavity Designs and also were configured to work with and without the KEF KUBE 200 active equalisation.

I could search forever to find a KUBE 200 or perhaps take advantage of higher capability (lower cost ?) more modern electronics that have even less insertion loss. I definately do not want to touch the midband. On my system, it's great.

Thanks

 

[clubsport911]

You could rig up a Linkwitz transform circuit.
Look here for the theory and the project and a spreadsheet for calculations

I like this ! Seemingly simple, but my only issues is somehow discovering the data on the drivers and cabinet.

The deisgners of the 105/3's are not exactly on display !

Good call though - thanks

 

[DreadPirate]

You could pick up an equalizer for some of the older Thiel speakers such as the CS3.5. These go for around $100. Some people ditched the equalizer and used the "Golden Flutes." It is possible that the GF were made for specific speakers, but I can't recall. This Thiel equalizer has a switch to boost 20 Hz or 40 Hz, see attached graph for measured response, pilfered from the stereophile site:

Thiel CS3.5 loudspeaker Measurements | Stereophile.com

 

[weltersys]

Sure... I have a 400W MF amps (40A current output continuous), MF Pre-amp and KEF 105/3's. The 105/3's are bandpass Coupled Cavity Designs and also were configured to work with and without the KEF KUBE 200 active equalisation.

I could search forever to find a KUBE 200 or perhaps take advantage of higher capability (lower cost ?) more modern electronics that have even less insertion loss. I definately do not want to touch the midband. On my system, it's great.

Thanks

The 105/3's frequency response being -2.5 at 49 Hz would indicate that even moderate boosting below that point would probably just result in over excursion, bandpass designs often roll off at 24 dB per octave.

Adding a sub for frequencies below 50 Hz would take care of the lack of LF without adding distortion.

 

[rcw666]

Yes an L-T transformed sub woofer is probably your best option.
rcw