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Multi-Way Conventional loudspeakers with crossovers

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Old 31st December 2006, 10:15 PM   #1
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Default 'Tarantism' Construction Diary

Hey folks.

Why is it such a PITA when trying to decide what to build next? You generally want to build something better than your last or at least significantly different, which isn't always that simple. Then you've got to sit down and play around with driver choices which could lead you around in an almost never ending circle and finally you have to balance all this within in a set of constraints, goals and a budget. Talk about banging your head against a wall. But we all do this for love so I'll quit my moaning right there.

The first steps are probably the most important so its wise to spend as much time as possible here until everything feels 'right'. In this vein I've been quietly messing around with a few designs over the last couple of months including a brief play with a Manger which whilst stunning in some respects also proved difficult to live with so decided to stick with traditional drivers and what I feel comfortable and familiar with.

Here's a quick run through of the main idea's I looked at along the way before arriving at the final design at the bottom of this post.

It all started off with a good idea of what I wanted. The original goals were a 2-way MTM using a wideband driver to cover as much of the freqency range as possible. Something along the lines of a Raven 3.2MMX and a pair of TAD 10" mid/bass crossing at maybe 800hz but the costs were astronomical for the drivers alone and wasn't confident that the sound would match the cost.

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Still looking at the idea of a wideband+woofer but without the costs of Raven+TAD setup I then chanced upon the Manger which has always interested me. I'd now got a little more greedy and decided I'd like to have generous bass handling capability so as to do away with the need for subs. So stuck four Peerless XLS10 in each cabinet, the plan was to cross these at around 200hz with the Manger. Only problem was that the cabinet was simply huge in relation to my room. Deep bass needs volume but I couldn't spare this much.

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At this point things got a bit confused, which is never good, and I'd really thrown out any real semblance of goals and just wanted something suitably impressive. This was generally a mis-mash of huge 3-way WMTMW designs of which I had no hope of successfully integrating into any average size British living room short of one in a small mansion, which sadly I don't live in. They all looked impressive though and the design specifics worked at least on paper. But none had any feel good factor about them and the last of these concepts were simply an aesthetic extension of the last speakers I built.


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I lost interest for a short while, sold my Perceives, which were the last speakers I built, and bought a pair of commercials - KEF Reference 201. I also got back into home theater and decided I'd like to tailor my next design in that direction.

So now that I'd got some direction again I got thinking about a compact design that would fit the ideals of home theater speaker. I ended up settling on the Manger for each of the front channels with these all being housed in a single wall mounted enclosure. The Manger is really ideal for this application because you've got no horizontal arrangement associated problems, had I not used the Manger the design as a whole would have been far more cumbersome but instead it turned out simple looking but effective all the same.
To cut a long story short though, I ordered a Manger to try out and after some time experimenting decided that I'd have a tough time living with them. That's not a put down on the Manger, simply that it had a couple of traits that happened to be polar opposites to what my preferences were, so despite sounded pretty fantastic in some area's it was never going to be a winner for me.

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At this point I'd got fed up and simply bought a full 5.1 line up of the KEF Reference loudspeakers. These speakers are awesome for home theater, I love em to bits for that but then again a lot of speakers do HT really well. The fronts are also no slouch for music but there's nothing much that stands out, sure they do nothing badly but on the otherhand because they don't do anything standout it all makes for a rather pedestrian listen. They're still better than a good proportion than the overpriced stuff you normally find in commercial land though.

So with that said I thought at least I've got a nice listen to be carrying on with whilst I make more serious plans for the next project.

I've been working away on this design for the last few weeks now progressing it naturally, juggling compromises and driver choices. The first couple of designs were really a strong nod towards compact and much of the design was built around this. In the end I felt I'd compromised a little too much although it was a definite step in the right direction.

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After playing around with small details of the above design I ended feeling something different was needed without so much emphasis on compromises in order to obtain compactness.
Its here where I arrived at what will be my next project: The Tarantism. Strange word but I found and read the meaning of the word over on Answers.com:

Quote:
A disorder characterized by an uncontrollable urge to dance
It instantly seemed to sum up what I want from a speaker and so Tarantism it was.

I'm thoroughly pleased with the overall look and specifics of this final design. Its got that feel good factor which will allow to maintain momentum through to the end which is important with fairly ambitious projects.

Drivers:

HF, I went back to the RAAL 140-15D that I'd looked at previously.

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Mids will be covered by a pair of the 4" Scanspeak 12M/4831G00 in an MTM configuration.

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And bass will be taken care of by a pair of 8" Seas W22-EX001

Crossover:

I'd really prefer to wait until the drivers are here with me before making more firm decisions but 300hz and 1.5Khz don't sound entirely unreasonable. One of the reasons I went with the larger RAAL was to try and keep the XO point well down - directivity between the Scan 12M mid and the RAAL is well matched at this point and the the low 1.5Khz cross also means that the MTM configuration can be used to control the vertical dispertion of the mids which would give a better match to the RAAL's own vertical characteristics and all the while avoiding combing and lobing nasties almost entirely. The added bonus is that parallel wiring of the mids will net me a sensitivity which would put them on par with the RAAL's 95dB/1w/1m.

I'll be going passive this time as I'd like to unchain myself from using the PC or entirely digital routes. However I think the best approach would be to play around with a PCXO first off using traditional IIR filters, this would let me quickly gauge the best points and where things need addressing. Then afterwards do the usual measure drivers->import in LEAP, model passive XO based on experience with PCXO then produce said passive XO.

Cabinet:

Standard stuff here: All MDF, chunky 75mm baffles, heavy bracing and the usual high gloss silver/black finish.

Mids will be in a sealed enclosure. Each of the Seas W22 will be ported and tuned to around 32hz in a 40ltr enclosure making for good response down to 30hz.

And finally the design itself:

Click the image to open in full size.

Click the image to open in full size.

Its deceptive really because it looks rather large but actually is quite compact considering. I've stuck a wireframe of the Perceives in one of those pics just to give a rough idea of size. These are pretty svelte and I'm well pleased with the overall look.

I've got drivers inbound and plan to start construction towards the end of January when its slightly warmer and more hospitable outdoors. So will update when I have more to show.

Thanks for looking and hope you enjoy,
Ant
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Old 31st December 2006, 10:58 PM   #2
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Looks Great. You must have given much thought to this. Looking forward to your progress. What software did you use to draw the Speakers?
Regards Sam.
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Old 31st December 2006, 11:09 PM   #3
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Thanks. All the drawing were done in Coreldraw.
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Old 31st December 2006, 11:54 PM   #4
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Very nice looking, indeed. You could do very well in a marketing department.
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Old 1st January 2007, 12:05 AM   #5
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Thanks Horus.

Gotta say I'm with Bill Hicks when it comes to Marketing though:

http://www.youtube.com/watch?v=gDW_Hj2K0wo
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Old 1st January 2007, 01:09 AM   #6
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Great design.
Build it. Put a 50000$ price tag on it. I bet you'll be successful.
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Old 1st January 2007, 04:10 PM   #7
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Quote:
Originally posted by horus
Very nice looking, indeed. You could do very well in a marketing department.
That's not marketing, it is great industrial design.

Love the first set of images.

Wow!

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Old 1st January 2007, 08:44 PM   #8
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Very nice!

I really like Tarantism, great word. I'm sure it will fit well with those speakers.

Josh
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Old 2nd January 2007, 05:21 AM   #9
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ShinOBIWAN

"Up-against-the-wall" speakers might be a good marriage to your projection HT setup. A more rounded shape, like an egg timer sliced vertically to go flat against the wall, could have useful baffle step reduction and more consistent in-room bass modes. An hourglass half elipse shape might be more attractive than a simple trapazoid.
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Old 3rd January 2007, 02:26 AM   #10
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Awesome plan. Interesting driver choice. Two questions:

1) Do you have a plan to deal with the very poor vertical off-axis response of the tweeter or do you not view this as a problem?

2) Why passive xover? You seemed to be one of the largest proponents of digital active crossovers. Does this mean you will also not be implementing room correction with these speakers? I was under the impression you were also a big proponent of room correction.

3) Since the choice of 8" woofers limits the lower frequency response of these speakers do you plan to use them with a subwoofer? Any ideas for that design and what you would use as a xover?
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