Advice sought for classical music project?

[Dave163]

Hi, I'm hoping some kind folks will be able to provide me with some pointers for a project that I'm building. Basically it's an electronic organ, with the sound created by PC software, to go in my home (room size 4x4x3 meters). The finished thing should look a bit like this:

[IMGDEAD]http://www.sdewit.nl/elec/johannus/monarke/rubens.jpg[/IMGDEAD]

My plan is to use the two organ pipe "towers" either side of the keyboards to hide speakers. Actually they are a bit bigger than what the photo suggests, they are 8 feet high, 2 feet deep and 20 inches wide, and the decorative pipes start 30 inches above the ground.

There are a few design caveats and parameters. I'm using an eight-channel soundcard and for starters I have an old 8 channel amp (actually a PA amp, but it's silent and can output around 100W per channel at 8 ohms). Two channels are for rear surround speakers, leaving up to six channels available for the main speakers.

If I go for multiple drivers rather than full range, do I actually need any crossover circuitry, since the input to the speakers is entirely digital via the soundcard and I have multiple sources and amp channels available. Is there freeware that can send specific frequencies through specific channels, which would be amplified via the amp channels and sent to individual drivers? Wouldn't this be a great way to "tune" the speakers to the room and iron out any imperfections? Or should I be looking at full range speakers?

Finally, bass must go down to 16Hz even if it's pretty quiet.

Some of my thoughts:

In a "real" organ the sound comes from above the player, and is pretty omnidirectional. Should I mount the speakers towards the top of the towers? Flat against the back wall of the tower? Pointing backwards to maximise reflections? Pointing up towards the ceiling? Would an open baffle increase the soundstage? What drivers would you recommend?

How about a line array of perhaps a dozen full range 4 inch drivers either side? Would that give better spacial presence and greater dynamic range?

Should I go for a separate sub in the corner of the room (or base of one of the towers)?

Clearly there's a few different ways it could be done - maybe buy a secondhand sub off Ebay so the DIY speaker part doesn't have to go right down to the very bottom for instance - but in total I'm limited to around £500 / $800 max so money spent on a professional sub would reduce what is available for the other speakers. On the other hand if I can get away with a digital crossover by using the six channels from the soundcard, that buys more driver or cabinet.

As the speakers are covered by a row of decorative metal organ pipes, I don't frankly care if they are made of MDF, PVC drainpipes or alienjuice, it's the sound that is everything here. How they look isn't an issue, it's how to get the most authentic sound from them that matters.

Final thought is for the rear surround speakers: I'm thinking either an "off the shelf" el cheapo bookshelf, or full range driver in DIY bookcase cabinet but open to suggestions.

Thanks for your advice and I'll keep you updated with progress.

 

[wakibaki]

Interesting project.

First, you say you intend to use an 8-channel computer soundcard. How do the keyboards and stops interface to the soundcard? What is actually going to produce the tones?

This is crucial to the whole design. You might need to enlist some help, either in terms of specialist software or hardware to get a really satisfactory result. One possibility might be to steal the internals from say, some Yamaha keyboards.

I've got to go out now, but I'll come back to this...

w

 

[theresa]

Home Page
The above links to SoundEasy. It is capable of turning a soundcard into a active crossover.

 

[sreten]

Hi,

Are you sure the basically superfluous decorative parts are not going
to "sing" along with whatever the speakers are doing rather more
enthusiastically than you'd like, they could be a real problem.

16Hz is certainly doable in that space, e.g. look up sonotube subs
eg. El Pipo at Pass Labs, but there are quite a few other TL type
designs that go that low on the web.

The speakers proper : with 6 channels of amplification lots of
possibilities. For the speakers what matters ? The sound sat
at the organ or the sound in the room or both ? A line array
will have severe comb effects at the seated position.
http://www.humblehomemadehifi.com/Pipeline.html
How loud should it go ?
As much as possible or lower with better quality ?

FWIW big (they have to be big) drivers that will do 16Hz properly
are not cheap, commercial HT subwoofers basically don't do 16Hz.

rgds, sreten.

 

[Dave163]

Many thanks for advice so far.

To Wakibaki, there are a few different "virtual organ" software programs; they all expect you to have MIDI-enabled keyboards, pedals and (where the stopknobs would go on a real organ), one or a pair of touchscreen monitors. My PC output is via an eight channel sound card, and since I also have an eight channel amp, I figured that I could either use four channels and off the shelf front and rear speakers, or for the same cost take the DIY route and be creative, e.g. with six channels operating six front drivers (sub, woofer and tweeter either side for instance) using digital crossovers that could be tweaked to whatever room it happens to be in.

Thanks Theresa for the link to digital crossover software. Would I need to wire anything like a resistor in series (or parallel) with my drivers if I went for digital crossovers and multi-channel amp, or is that not necessary (obviously taking precautions to ensure I match the correct amp output to the correct driver and don't overdo the power...)

Sreten, I'm aware there is a risk of resonance in the decorative metal pipe features, stuffing them with something solid might help but equally might the resonance enhance the room? I'll only know once they are in place. El pipo is too long for my room, though I could fold a PVC drainpipe a couple of times. Would that be superior to an MDF transmission line or quarter wave cabinet - I read somewhere that PVC converts acoustic energy to heat or something that makes it a good choice though it isn't often used due to getting funny looks if you have a big sewer in your living room. Here looks aren't important, so what would be a good design and materials for a sub based on a TL?

Room size is small (living room) so sound quality is more important than quantity. But huge dynamic range with an organ and big "presence". I thought line arrays worked best in the nearfield so that both seated at the console or sitting in the living room one would experience the same effect. If that's not the case, how else could I maximise the stage effect? I did wonder about having the speakers at the top of the towers, or pointing up towards the ceiling or towards the back wall. Would open baffles be a more suitable design than a line array? Closed box? Horn? Open to suggestions! I'm looking uppermost for good sound when seated at the instrument (maybe 4 foot from the towers either side), and secondly for sound quality in the room.

 

[sreten]

Hi,

Quoting from the line array link I posted, changing cm to metres :

A rule of thumb is that the listening distance should more than two times the
height of the array. In this case the the distance between the centres of the
two outer drivers is 1,2m, so the listening distance should be at least 2.4m,
preferably a little more (I listen at 3.2m).

My advice, being no fan of artifice, would be to ditch completely the
useless bits and faithfully replicate the central control / playing section.

To this either side add a a pair of serious, properly designed speakers,
though I'm thinking organ piped shaped to be apposite, something like
like these B&O's but a far wider and somewhat taller aspect :

BeoLab 8002 - Bang & Olufsen

Something that could work well in this context with added
subwoofer, basically mounted on the end of top of the pipe is :

But TBH the above is serious quality and not cheap, can be done cheaper.

But whatever, with a few more bits you'd have a great music replay system as well.

rgds, sreten.

 

[Dave163]

Thanks Sreten.

I would envisage the centre-to-centre distance to be around 2.1 m, if I'm sitting midway between the two speakers. From what you say, line arrays are out, but the bottom speaker you show looks rather like a line array with its column of several drivers all closely stacked together. I'm probably missing something.

So back to deciding on the best type of speaker for reproducing a large soundstage, preferably with the sound appearing to come from above and in front of (but to the sides of) my head. Transmission line, horn, cabinet, open baffle? Closed cabinet or TL for the bass and something else for the other drivers? Any suggestions for drivers? If I don't need a crossover circuit or amplifier then I can put all my money on the drivers and an MDF or PVC box, but there are so many different DIY options, none of which I'm likely to be able to audition, so it's a bit hard knowing which of many possible routes to go down. Advice very much appreciated!

 

[sreten]

Hi,

That speaker is a 3-way, with a MTM mid/treble layout and
4 bass drivers wired as one large long but thin bass driver.

Your right, there are many design choices out there, and I
cannot make them for you, especially as bass end needs
special attention to get to 16Hz cleanly.

And your total budget makes things very difficult.

I also have no idea of your real technical skills.

http://www.diyaudio.com/forums/subwoofers/55377-folded-sonotube-tl-sub-complete.html

Might be of some interest, you'd need two of them,
the longer you make them the lower the tuning.

With subs, possibly a sealed version of this :
ZA5.5tt - MMTMM 2.5-way vertical array
Zaph|Audio - ZA5 Speaker Designs with ZA14W08 woofer and Vifa DQ25SC16-04 tweeter

It would take some skill to derive the correct active filters.

rgds, sreten.

 

[chris661]

Here's an idea (and it is a pretty wild one)

Assuming (and it is a large assumption) that the 16Hz pipe plays 16Hz, plus some harmonics (32, 48, 64Hz etc), why not use a single, high power 15" driver in a bandpass enclosure, tuned to 16Hz?
You'd need a regular subwoofer to cover the notes from 32Hz upwards, but having two different subs with different design criteria is easier to do than a single driver covering all the notes down to frequencies that low. Anyway, like I said, just a thought. With all those amplifier channels and crossover capabilities (see Foobar2000), it could be something to try.

 

[sreten]

Here's an idea (and it is a pretty wild one)

Assuming (and it is a large assumption) that the 16Hz pipe plays 16Hz, plus some harmonics (32, 48, 64Hz etc), why not use a single, high power 15" driver in a bandpass enclosure, tuned to 16Hz?
You'd need a regular subwoofer to cover the notes from 32Hz upwards, but having two different subs with different design criteria is easier to do than a single driver covering all the notes down to frequencies that low. Anyway, like I said, just a thought. With all those amplifier channels and crossover capabilities (see Foobar2000), it could be something to try.

Hi,

A vented box tuned to near 16Hz would work, though I cannot see the point
of a bandpass, a normal box will go higher, not needing the extra subwoofer.

I do not believe two different subwoofers are better/easier than two the same.

rgds, sreten.