Allen Speaker What If...

[cantornikolaos]

Let's say in a hypothetical situation there is an Allen MDS organ with 2 channels. There are probably lots of those! What if I build powerful, custom-designed 10-way speakers instead of the typical 2-way or even 3-way speakers? With dedicated drivers for almost every octave you'relikely to get out of an organ, I think it would sound more clean. Anyone ever tried this before?

[michaelhoddy]

After a certain point, more drivers doesn't equal more even or extended frequency response. There are 2-way designs that are wonderfully flat and 4-way designs that are an absolute mess. The more passbands you have, the harder it actually gets to maintain even frequency response and especially phase coherency throughout, most notably through the crossover points. Good examples (and by "good" I mean top-shelf professional commercial makers like Meyer Sound) use as few drivers as are necessary to achieve the desired power handling, frequency response, and dispersion characteristics for these reasons.

Assigning "drivers to octaves" is not really possible- crossovers don't work in such a way that one speaker stops while another one starts as you go up the keyboard. There is actually considerable overlap even with very high-order crossover filters, which have their own problems in the time domain. Through the crossover, you have both drivers on either side of it sounding for quite some range past the crossover point. This is the main reason it's so hard to make a speaker which has truly flat frequency response without some combination of exceptional engineering and component quality, and/or electronic correction through the use of very sophisticated filters. The only way your scenario works is to assign "notes to channels," and this is indeed what companies like AOB used to do, where a given 61-note rank might have 5-7 separate speakers assigned to it, with about 6 notes assigned to each speaker sequentially with some repetition in the higher octaves.. This is of course expensive to do.

Many organ speaker designs are a real mess- very poorly thought out from an acoustical perspective. The usual Allen HC-14's or 15's which I would expect to find in an MDS installation are in the middle of the pack- not amazing, but not bad. If the organ sounds poorly, I suspect the finishing or voicing or acoustical environment or placement of the speakers is more to blame than the speakers themselves. This is regrettably often the case with the big-box electronic organ makers.

[jbird604]

Nik,

Some Allen models have four or more channels coming out of the cage that get mixed down to just two for a self-contained speaker system. You might investigate the possibility of re-configuring a given Allen so that it gets the most channels the model is capable of.

Your proposal for a different type of speaker does have its problems, as Michael notes. However, your heart is in the right place. In my experience, the best two ways to improve organ audio are (1) to use heftier amplfiers than the somewhat puny ones installed by default. Commercial amps with hundreds of watts of power are available for $299 from mail-order places. And (2) using multiple speaker systems on each channel with the speakers aimed in different directions.

Of course you can't drive an unlimited number of speakers from a single amp, but on a typical Allen an amp channel can drive two HC-15's plus two PP units (these are the little "presence projector" boxes with only a midrange and tweeter in them -- they draw so little current from the amp that you don't have to worry much about their effect on impedance). Aim the PP's to bounce off the walls and ceiling. This completely eliminates the "beaming" effect of some speakers. Of course this works better in an open and lively room, but it can't hurt to try even in a home setting. In a home, just adding an extension speaker to each channel of the internals does a world of good.

Beefing up the audio is definitely worth doing in many cases, though it won't make a silk purse out of a sow's ear. The smaller models just don't have enough circuitry to give each stop the individuality and clarity it needs when numerous stops are drawn. But whatever we can do to help is worth doing.

[cantornikolaos]

Maybe amps that don't mute the higher frequencies when used at volume levels lower than Full Throttle would help make it clearer and brighter and less muddy even with the same power and the same or similar speakers. Ever heard of Allen amps disproportionately reducing the volume of the "upperwork" of the organ? I read once about it. I'm pretty sure I'm experiencing it.

[John Vanderlee]

. Commercial amps with hundreds of watts of power are available for $299 from mail-order places.....

while that is true, be careful of their specs. I used a 500 watt RMS amp of a known brand only to find out it rolls off sharply at 20 Hz! That means it wont play a 16 Hz (32') C ! Many of those amps are made with guitarists in mind - that don't go that low.

[cantornikolaos]

I'm aware of that and would be looking for something that goes down to 16Hz if not lower. Sadly though, I doubt I'll get to experiment with anything soon.