Improving my retro digital piano's audio reproduction.
This blurb is based on years of being a frugal fellow, not buying new musical gadgetry and preferring experimentation. I'm an appreciator of second-hand stuff that can be fixed and won't instantly de-value as I hand over the money.
I bought the Realistic graphic equaliser - model number 31-2000 from a dubious chap in Southampton in the 1990s, a shop called Music City, it was more shop than city, filled with power amps, speakers and old synths.
I bought the Realistic graphic equaliser - model number 31-2000 from a dubious chap in Southampton in the 1990s, a shop called Music City, it was more shop than city, filled with power amps, speakers and old synths.
The dual ten band Realistic EQ served me well, its 80s aluminium face is still elegant and the two zero-gain controls with informative level LEDs is futuristic technology, it uses inductors to select its frequency bands. I can't confirm that inductors impart an inductory sound with a vocal quality, but I may have imagined it. Ten band equalisation can help improve what comes from your speakers, but it's not optimal. The next section suggests that thirty-one bands target the more specific areas of tonal imperfection, and therefore more bands are better for taming the most challenging of instruments - the retro digital piano.
Behringer GEQ-3102.
A solution conveniently resided in my cupboard, collecting dust for 2 years, a part of a job-lot of stuff I acquired from a fellow - a Behringer GEQ-3102 equaliser, to me it's an almost modern non-inductor based piece of 2 unit rack-mount space-age wizardry from the early 2000s. It lights up like a Christmas tree, it has dual LED level meters and 62 illuminated sliders that require painstaking patience to adjust, and a fabulous adjustable low-cut filter (and a high-cut filter too). I unscrewed the rack-mount ends and crafted new aluminium flat ends, as the rack-mount ends chafed with my amplifier.
31 bands per channel seemed ridiculous, but offered the frequency accuracy that I needed. In short - remove the muddyness from the 160Hz area, reduce the clanging culprits within the 300Hz to 500Hz region, boost a bit of 2.5kHz and the turn the low cut (high pass) filter to 200Hz. It will steadily cut the low frequencies below the cut-off frequency, a tapering off known visually as the Bode plot. A normal graphic EQ wouldn't achieve this. Even though a piano goes low, it's not unnaturally bassy.
A speaker does not behave like a piano string, instead it can churn out horrible muddy rumble within its box, a piano string doesn't. The adjustable low-cut filter set correctly will greatly improve clarity and piano sound reproduction alone. The GEQ-3102 also gives you a choice of +/- 12dB or +/- 6dB gain / cut, independent left and right input level controls, switchable input or output level LED bar meters and EQ bypass buttons. Audio connections are made with 1/4 inch mono jack plugs or XLRs.
A speaker does not behave like a piano string, instead it can churn out horrible muddy rumble within its box, a piano string doesn't. The adjustable low-cut filter set correctly will greatly improve clarity and piano sound reproduction alone. The GEQ-3102 also gives you a choice of +/- 12dB or +/- 6dB gain / cut, independent left and right input level controls, switchable input or output level LED bar meters and EQ bypass buttons. Audio connections are made with 1/4 inch mono jack plugs or XLRs.
Speaker experiments.
Speaker choice is critical. Having become accustomed to the unremovable twangy mid-range dongs from the previously mentioned Kenwood speakers and Realistic EQ combo, I consumed a few bottles of ale and headed into the attic with vim and vigour. I targeted the pair of 70s speakers acquired from a car-boot sale in the early 90s for £1. Crafted by Lord Alan Michael Sugar's bare hands at his AMS Trading empire - the Amstrad Acoustra 2500 speakers were soon to be seriously molested.
These teak-finish speakers were rather weedy with their 8 inch parched paper drivers, the crossover's filtration was the worst I'd ever encountered, the front grill was geometrically outrageous and the method of connection was 4mm banana plugs! The 15mm thickness of the chipboard cabinets was the only strong point.
These teak-finish speakers were rather weedy with their 8 inch parched paper drivers, the crossover's filtration was the worst I'd ever encountered, the front grill was geometrically outrageous and the method of connection was 4mm banana plugs! The 15mm thickness of the chipboard cabinets was the only strong point.
Peeling off the layer of fake teak was both liberating and therapeutic. Knowing that pianos don't have filters and tweeters, I chopped the speaker box in half, glued the top back on, tossing away the tweeter and the stifling crossover, and directly wired the speaker to new spring connectors on the rear. Lined with ineffective polyester acoustic wadding - a pair of matt grey cubes were born, metallic-pewter grills protecting the new replacement shining woofers - the Audax AP210Z0.
This speaker reproduces less of that nasty donging ringing tone that lurks within the 20 year old piano samples. This speaker is acting as 'dong' filter, the result is a warmer and more natural sound, free from the worst of the offending over-tones.
The frequency range of this Audax speaker is 29 - 4000 Hz, 70 watt RMS power handling and 6 ohm impedance. You don't need tweeters, pianos are mellow and acoustic, I've found that tweeters create an unnatural and unwanted twang, and frequencies over 4kHz are not of any use.
These speakers give the best piano reproduction I've created with a retro stage piano, I still use the small speakers on top at reduced volume as they provide a spatial effect, these are connected to the amplifier's 'B output', the woofers to the 'A output'.
Taking the speakers off the floor and sitting them on shelves miraculously reduced the bass which proved to be a great improvement.
Another development arose when my tormented autistic ears forced further investigations. I already learned that crossovers are the enemy of the essential midrange, and high frequency tweeters are bad news, but the speaker enclosure needs heavy duty lagging. By internally encasing the enclosure with literal loft insulation, the rumble factor was removed. Insulate so that all sides are covered and there's only a small space behind the speaker cone. This removes much nastiness from the lower end, which a real piano doesn't produce.
I'm currently theorising that good six inch speakers may be the optimal size, without the cruel crossover. One mustn't expect good piano reproduction at home with any speakers over eight inches, bigger is definitely not better.
However, my interest is now piqued by the DML concept. The Distributed Mode Loudspeaker uses a flat board as the 'speaker cone' with a molested coneless conventional speaker mounted behind the board.
The frequency range of this Audax speaker is 29 - 4000 Hz, 70 watt RMS power handling and 6 ohm impedance. You don't need tweeters, pianos are mellow and acoustic, I've found that tweeters create an unnatural and unwanted twang, and frequencies over 4kHz are not of any use.
These speakers give the best piano reproduction I've created with a retro stage piano, I still use the small speakers on top at reduced volume as they provide a spatial effect, these are connected to the amplifier's 'B output', the woofers to the 'A output'.
Taking the speakers off the floor and sitting them on shelves miraculously reduced the bass which proved to be a great improvement.
Another development arose when my tormented autistic ears forced further investigations. I already learned that crossovers are the enemy of the essential midrange, and high frequency tweeters are bad news, but the speaker enclosure needs heavy duty lagging. By internally encasing the enclosure with literal loft insulation, the rumble factor was removed. Insulate so that all sides are covered and there's only a small space behind the speaker cone. This removes much nastiness from the lower end, which a real piano doesn't produce.
I'm currently theorising that good six inch speakers may be the optimal size, without the cruel crossover. One mustn't expect good piano reproduction at home with any speakers over eight inches, bigger is definitely not better.
However, my interest is now piqued by the DML concept. The Distributed Mode Loudspeaker uses a flat board as the 'speaker cone' with a molested coneless conventional speaker mounted behind the board.
Zoom RFX-1000 effects unit.
With the Behringer EQ came a crackling Zoom RFX-1000 effects unit, which just needed the jack sockets re-soldering to the PCB.
This is an excellent effector and covers most FX needs, if you don't mind the simpler hands-on approach, there are no programs or presets here. I also own the Zoom 1201 and the 1204, the RFX-1000 is my preferred box of tricks.
I switch between the tremolo effect for electric piano and the excellent 'Wide Mix' or 'Cabinet simulator' effect for acoustic piano. Wide Mix adds a very notable brighter and livelier spatial stereo dimension to the piano and Cabinet excites certain frequencies. In my circumstance, switching in the Wide Mix effect is like hitting a figurative 'Super Stereo' button and adding a magical depth. Probably not as wonderful as a dedicated stereo expander, like the Behringer Edison - but it's a bonus boost.
A very underrated and forgotten device that has many gems within, and a rather green theme. Oddly, it doesn't have an effect bypass button, it needs a foot switch, so inevitably I made an external non-latching mini-button to plug in and probe with a finger.
I switch between the tremolo effect for electric piano and the excellent 'Wide Mix' or 'Cabinet simulator' effect for acoustic piano. Wide Mix adds a very notable brighter and livelier spatial stereo dimension to the piano and Cabinet excites certain frequencies. In my circumstance, switching in the Wide Mix effect is like hitting a figurative 'Super Stereo' button and adding a magical depth. Probably not as wonderful as a dedicated stereo expander, like the Behringer Edison - but it's a bonus boost.
A very underrated and forgotten device that has many gems within, and a rather green theme. Oddly, it doesn't have an effect bypass button, it needs a foot switch, so inevitably I made an external non-latching mini-button to plug in and probe with a finger.
The inhibiting inductor.
Another debatable improvement I devised involved experimenting with my in-line inductor invention which is inserted between the small speakers and amplifier, as these still produced some twangy overtones.
You can make your own inductors to insert into your speaker wiring using 0.5mm diameter enamelled copper wire (24 swg or similar size) wound onto a 9.5mm diameter ferrite, 35 or 40mm long, with an insulating layer of tape around the ferrite. You'd need an LCR meter to acheive 2mH though. Miniature or SMD (surface mount devices) with low power handling won't cope.
My dalliances with filtration have shed light on this type of filter, it's an R-L filter where L is the series inductance and R will be the parallel resistance of the speaker.
More inductance will further reduce the upper frequency range, becoming more muffled.
Less inductance will open up the upper frequency range, becoming brighter.
I find that this device mellows the piano sound from the small 'spatial' speakers, but unfortunately it cuts the jinglyness from the DX7, hence the bypass switch.
I found that putting the inductors between the piano and graphic EQ had no effect at all, owing to the higher load resistance of the EQ. If I was Gary Barlow I'd just buy some top of the range gear.
The inductor experiments were a means toward minimalism that just secreted my problems under my metaphorical carpet. I pushed the boat out and obtained an obscure Behringer Modulizer, it contains a splendid 'stereo imager' and other psycho-acoustic effects. This spreads the sound outwards whilst adding some midrange clarity, but also adds yet another ancillary item to the outboard gadgetry collection.
My dalliances with filtration have shed light on this type of filter, it's an R-L filter where L is the series inductance and R will be the parallel resistance of the speaker.
More inductance will further reduce the upper frequency range, becoming more muffled.
Less inductance will open up the upper frequency range, becoming brighter.
I find that this device mellows the piano sound from the small 'spatial' speakers, but unfortunately it cuts the jinglyness from the DX7, hence the bypass switch.
I found that putting the inductors between the piano and graphic EQ had no effect at all, owing to the higher load resistance of the EQ. If I was Gary Barlow I'd just buy some top of the range gear.
The inductor experiments were a means toward minimalism that just secreted my problems under my metaphorical carpet. I pushed the boat out and obtained an obscure Behringer Modulizer, it contains a splendid 'stereo imager' and other psycho-acoustic effects. This spreads the sound outwards whilst adding some midrange clarity, but also adds yet another ancillary item to the outboard gadgetry collection.