Stereo Question: Low power requirements?

[Alan Wheeler]

How about the cannon ball firing part of the 1812 overture

Best done with a real Cannon :-)
I suppose that could be called a "Point source" :-)

[Alan Wheeler]

there is not much on the shelves of mass merchants in speakers and receivers

Speakers IMO have taken a major dive in quality. There is a lot of crap being mass produced. I don't get the thinking. Companies built years of reputation on being world leaders. In the very early days, Philips were amasing speaker makers. Companies like B&W, Infinity and so on, all made top of the line equipment. Today they all mass produce crap but still sell it with the understanding it is still top of the line. Warfedale is just a joke.
Plus there are a lot of high price boxes being made that are phenominaly expensive and have no reason to be. Sales are often made by the idea that price is reflecting sound quality. Every now and then, some company steps out of the mold and creates something that can grab you. But it is not often these days.
Oh yeah, that reminds me of yet another snake charmer. A set of speakers that RRP here in NZ was NZ$100K. Yep that's no typo. But you did get a pair of them :-) I was asked to take a listen to them. I asked him what was so flash about them that should command such a rediculous price. Oh well they are digital, he replied. Digital speakers??? Yes, they are completely digital. I had a listen and my results were, they sounded rather average to me. He was not a happy Lad. But then, if he didn't want to hear such an answer, he should never have asked me in the first place. And the idea that speakers could be digital just makes me laugh. He obviously does not understand some form of concept going on in side.

[Boracay]

Does anyone have any suggestions on which "Boom Boxes" might be best on a boat?

I walk through my local mega electrics store and they all look alike.

My little tape recorder/am/fm radio seems to run fine on four rechargable "AA" batteries for a few days but it is not going to blow me out of the cabin.

I should use "C" batteries but there are no rechargable ones available these days so I wrapped some cardboard around a couple of NMH "AA"s.

[Alan Wheeler]

which "Boom Boxes" might be best on a boat?

You are never going to get a "best" one. You need to listen to them and choose one that reproduces the sound you like to hear. That then has to be weighed against things like power consumption. Especially if it is battery powerd by D cells etc. Then you have to place those two against the space you have to keep it all in.
I reckon the MP3 player and those units you can fit the MP3 player into must be a real good bet. But not having played with or even listened to, I can not vouch for sound quality and ease of powering.

[Rick]

One speaker that comes to being very close to a point source is a plasma speaker. Tests were made in the early 60's using an oxy-acetylene flame, two carbon probes and a high voltage amplifier (like what a vacuum tube amp gives without the output transformer). The amplifier outut is wired to the probes located in the correct part of the plasma and the voltage modulates the plasma stream.

The sound was described as being fantastic with plenty of audio power. Oddly I've not heard of any further work being done with such speakers, have you Alan?
Rick

[camaraderie]

Here's something that might be of interest to those with portable boat sound needs.
Tivoli Audio, LLC - SongBook® Radio in Blue

[Paul Elliott]

Originally Posted by Rick

One speaker that comes to being very close to a point source is a plasma speaker. Tests were made in the early 60's using an oxy-acetylene flame, two carbon probes and a high voltage amplifier (like what a vacuum tube amp gives without the output transformer). The amplifier outut is wired to the probes located in the correct part of the plasma and the voltage modulates the plasma stream.

The sound was described as being fantastic with plenty of audio power. Oddly I've not heard of any further work being done with such speakers, have you Alan?
Rick

My son was telling me about this -- he had read an article on it somewhere, just a few days ago. I do remember this from years ago, and as I recall, in order to get *any* bass response the ionized flame had to be huge. It was considered a possible tweeter technology, but was really more of a gimmick.

Probably not my first choice for a boat's sound system!

[Alan Wheeler]

Oddly I've not heard of any further work being done with such speakers, have you Alan?

Yep, the Japanese trialed a version of it about 15 yrs ago or so. They used a carbon arc and the sound was modulated on the arc. It was really cool to watch, although you needed dark welding glasses as the UV was huge. The "speaker" was a pole with the arc ligt at the top of the pole. And a large cable running away from the pole to a room which remained closed up till and during the audition. The sound was OK in the upper range, but quickly attenuated as the audio range fell. There was poor mid/low performance and no low range what so ever. Then when the audition was completed, the door to the room was opened. I kid you not, but the room was stacked full of welders. The power required to do what they did would have browned out a small town.

[Alan Wheeler]

Another hugely interesting concept was conceived by a young engineer at Bose about 8 yrs ago now. He was playing with the idea of modulating Audio on an Ultrasonic carrier. Much like how Audio is modulated on the back of an FM carrier. He developed the ability to project two ultrasonic beams and at the point where they crossed, audio could be heard. The quality still had a lot of work to be done, but the concept worked. Just imagine being able to sit in the convergence area and hear high quality Audio and someone sitting just out of the area, not being able to hear a thing.
Well strangely, the US Navy bought all the rights to it and the concept was never heard of again. I remember we all were scratch our heads and coming up with conspiracy theories as to why the Navy would want it.

[Zach]

Well... I've been digging around through my box of random speakers. Found a couple of sets of varying size cheapies. Heading down to the boat this weekend, so no testing till next week.

Now I just need to go find a megaphone and copy the angle of the horn. (Guessing they have a little more cash outlay in research... and play around with various lengths. I'm thinking a smaller speaker, with a larger opening would produce a greater increase in volume compared to a larger speaker diameter to and only slightly larger opening.

Who knows, may end up with a set of air horns with some head phone speakers in the skinny ends...

[Alan Wheeler]

There are Horns and there a Flares and there are Wave guides. Each has a different reason for use. The flare of a horn is an Exponential curve. The size of the horn does not determine the loudness. It determines the low freq cut off point of the sound. The Horn mouth and length needs to be a sum of the wave length of the lowest operating freq of the box.
Box design is critical for all sorts of reasons. That graph of speaker impedance posted earlier, is determined by the act of the Box upon the driver.
Draw a circle, and then divide it into three by making a Peace sign, then write in one segment SPL, another segment frequency and the final segment box size. If you want to change one bigger or smaller, you as default change another. You can choose which other you want, but you can not keep both the others the same. One will always affect one other. What size box the speaker needs to do the job it is intended for, is determined by a whole lot of numbers that go into the driver design.
One other form of loading we talk about in speaker design, is spacial loading. A horn is what controls loading.
Sound is pressure. Rarefication and Compression of air. As the diaphragm of the driver moves forward, it compresses the air in front of it. A reduction in pressure is occurring behind it. If the driver is not mounted on a baffle(Panel) the air compressed at the front simply rolls around to fill in the void at the back. The result is no sound. Because that is not happening efficiently, we do actually hear some sound, but it isn't very loud. The Baffle makes the distance to the back of the speaker further and so the sound pressure arrives later and out of "phase" with the vacum at the rear and so we now hear the sound emanating from the front of the driver. But it will be mid/high freq only. Depending on the size of the baffle, low frequencies being long, will still wrap around behind the driver. eventually if we get a baffle large enough, all freq's will be blocked of. But we don't always have that luxury. Plus a few other important driver controls are required. So a box is a good way of sealing off the driver's front from it's rear. However, low freq's longer in wavelength than the size of the front of the box, still wrap around behind the box. If we were to hang a speaker box in the air, all sound radiates away in a law of -6dB of SPL for every doubling of distance. Now in the commercial world i was in, many of the top name boxes gave all their specifications in this way. Cheaper names often cheated by not giving you that information. So now, if you bring that speaker done and sit it on the floor, you now have the floor to stop the sound going anywhere underneath. So that sound that would have disapeared into that space now blocked off, now adds to the sound coming from the speaker. The space is cut in half, so we call that half space loading. If you now place a wall directly behind the speaker, we now have 1/4 space loading. If you place the speaker in the corner, you now have 1/8th space loading. All the time, the sound that would have been lost is now added to the sound emanating directly from the front of the box.
A horn does the same thing. However, it does also do one thing else. Well actually it does lots of things. But the main primary one is it couples the Voice coil of the driver to the Air. We call it an impedance coupling device. It couples the driver to the air.
So to wind all that up, if you place a horn on a speaker, yes it will make the sound louder. But it could (most likely) also make the sound very "barkey". Depending on throat size, You will loose a lot of low end sound. Horn loaded sub boxes are huge.

[Alan Wheeler]

This is the site of the Bass boxes I used in my big concert rigs.
The guy that designed these (one hell of a clever lad) also makes home HiFi boxes. They are the most amazing sounding boxes you can imagine and not badly priced. Let me know if you want to be introduced to the guy.
BASSMAXX

Caution, Playing with speakers can be dangerous. This is what happens when someone a little too nerdy gets a little too bored.
THE BIGGEST HORN SUB OF THE WORLD

[MidLandOne]

Originally Posted by Boracay

Does anyone have any suggestions on which "Boom Boxes" might be best on a boat?

I walk through my local mega electrics store and they all look alike.

I'm not sure if you had much response to this question. I am no audio engineer but enjoy recorded music within the realms of a moderate budget and limited space so will give an idea of what I do.

First no "boom box" is going to do a magnificent job, but will get by and you need to be able to listen to it out of the shop shelves before buying or at least with the right of return (we have local retail chains here in NZ that will let you buy and return any appliance if doesn't do the job, no questions asked) - but I suspect you know that.

What I do is play some CD's with which I am familiar and which give a range of instruments, voice, dynamic range, etc. While you may have different recordings in your collection the following are just examples of what I look for using a mixture of Country/American, Instrumental Rock and Popular Rock as examples (I think snippets of them can be found on the internet so's you can get an idea of what I am saying, but use a CD for the tests, of course) - if any graphic equaliser on the box, disable it -

Juice Newton - "Angel of the Morning". This track in my view is a good test and I have seen it used in equipment reviews, the high notes should remain crisp and natural without getting edgy and the full dynamic range be there - louds loud and softer softer. On the high and strong vocals all the percussion and accompanying instruments should all come through and be able to be picked out sounding as natural as possible, with the fast attack times of the percussion carried over.

Joe Satriani - "Always With Me, Always with You" this track is a very tricky piece and a good test as it explores the guitar. Unlike, say, Hendrix recordings, the CD's are well produced so should sound true. The quality of the playing should really come through and the clap and light percussion come through cleanly with the fast attack times preserved. If into Satriani then there are plenty of examples of his (eg Satch Boogie) where the music quickly falls apart and get mushy losing tightness on less than mundane equipment.

Michael Jackson - "Thriller" or "Dangerous" albums. OK you you don't have to like him but these albums are immaculately produced so you know what is going into the box is more than just OK. I will just refer to the "Dangerous" album (it was his first made specifically for CD). Jackson provides much of his own backing vocals so in a song like "Dangerous" both his lead and his backing vocals should be well seperated and identifiable when he sings over himself with the word "dangerous". The breaking sound sequence right at the start of "Jam" should sound like something breaking and the low level choral, whispered, industrial sound introductions to a number of the tracks should stand out although of low level. The percussion intro to "Black and White" should be crisp and the knocking on the door sound like real knocking, also the spoken voice sound as natural as possible - the rest of the track should come across as ultra tight (because it is, as are the others [sigh]). The atmosphere in parts of tracks like "Keep the Faith" and "Will You be There" should be well preserved. The deep bassy instrument backing in the likes of "Who Is it" should come across as true to tummy wobbling as possible but not muffled like a boy racers car audio turned up into distortion and it then have its later quiet presence behind the vocal parts and the whole not get muddy and loose sounding with the other instruments and his own backing vocals - the very crisply sung part of the vocals should come across that way (Much of "Give In to Me" is also good test for how well the various components of the music are kept apart without getting muddied together while fighting for their own presence). Some of the tracks have spoken voice and it should sound like a human - always a good test if the recording is known to be good. I am not a great Jackson fan but this whole album, if available, should come across as very tight and every component in way of voice and instrument clearly identifiable - the album is with little fault in that direction.

Better stop - as I say I am not an audio engineer, am just a listener (and did study the physics of music at university a bit ) and someone like Alan may be able to put me straight on some things or emphasise the worth maybe of some other. Not meaning you should use the above recordings, have only used them as the example of what I would look for using tracks with which I am familiar (and I should add that my music interests are more catholic than the examples might infer ).

[Alan Wheeler]

Midlandone has the right idea of using music you are familiar with. I have a few special test tracks. But they are special because they revealed possible "issues" with a system. Especially if i had to mix on some other companies system. But one track that is quite unique is Dire Straights Private Investigation. The part in the middle where the milk bottle breaks and the cat meows. That braking glass is very revealing. Rick mentioned about phase linearity in speakers before. This is a subject I won't go into hear, because it is so deep and complex I simply will only confuse...no... most likely bore you all. But in essence, Phase is best (I think best) explained like this. Picture a sine wave. Now picture two sign waves. Place a mark on the sine wave line. This will represent a start point in time. We will assume both waves have that timing mark in an identical place. Now if you place the second sign wave on top of the first sign wave and have the timing points lined up, you can say that both waves are in Phase. If you move one wave along slightly, the waves are now out of phase. If you continue to move that wave along, you will eventually come to a point where the two waves are now 180deg out and if it were sound, the sound would actually be canceld. If you move that wave along far enough, the waves will once again be in Phase, but the time will be out. OK, that is as far as I will go, but hopefully that makes the comments about Phase a little more understandable.
Now in stereo, a sound "image" is created by using time. I mentioned that a little earlier in another post. But there are even more subtle aspects going on. Especially in complex audio waves (like the breaking glass) phase correlation is essential to coherence of sounds. A poor system will not reproduce that breaking glass very well. A very good system will allow the glass to come to life and "image" itself in space.

[Sandero]

I don't know how one can evaluate natural sound when using over produced pop music as a standard. Can anyone explain that?