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Old 18th March 2004, 11:31 AM   #121
rabbitz is offline rabbitz  Australia
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Quote:
Originally posted by weeghel
thanks
I checked the wiki out yesterday, but hadn't seen this page. I guess it's the vifa newbie project? Not much info on there yet.

I've been looking for an excuse to start a new speaker project, maybe this is one
It's this one.

http://www.diyaudio.com/wiki/index.p...Vifa+P13%2FD27
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Old 19th March 2004, 12:18 AM   #122
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Thanks, rabbitz. I guess I'll play around with WinISD...
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Old 6th April 2004, 02:57 AM   #123
Jay is offline Jay  Indonesia
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Hello All,

How is this project going (Especially the Rabbitz' P13WH+D27TG)? Are there enough newbies interested? If there is such a good interest I think I will want to buy the drivers and build and share my design here. I'm pretty sure that my crossover will beat the 5uF crossover

Well, I haven't made the design yet, but I have a crossover design concept that is almost always successfull. I like transient. And speakers like P13WH+D27TG+5uF is often favoured by tube lovers, which I believe will like the quality of my crossover.

The problem is, I don't like small bookshelves. But I have made one small speaker using the crossover design concept and it was a success so I'm confident I'll make it again.

And I'm now trying to beat the daline 3.1 (to my favor, I already beat it, but I want a speaker that favors many people). I don't like the Focal 5W4211, but I will let you know when I'm done (and there is interest from people)...

Jay.
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Old 6th April 2004, 03:28 AM   #124
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Can you tell us anything about the XO... i was listening to a set of P13/D27 dalines on Staurday that just used the 5 uF cap -- they were pretty good.

dave
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Old 6th April 2004, 09:49 AM   #125
Jay is offline Jay  Indonesia
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Well, since Dave asked...

THE CROSSOVER

There is nothing special with the crossover design concept, except for my imaginations
when I tried to implement new (often stupid) ideas. I said it is a concept because the
imagination and also the implementation is quite different if one is ever exist. The idea
centers around the "reason" of choosing a high "virtual" crossover point. This crossover
further had different implementations:

1) "Third order" fullrange. This turns a standard woofer into fullrange driver. The easiest
A/B comparison is the driver itself when fed as fullrange. If you feed a standard driver
with fullrange signal, usually the midbass is over exposed and the resonance at high
point rolloff is bad. With this implementation, a tight bass can be achieved. If 5K is
enough for you, you don't need a helper tweeter (I found it difficult to design a tweeter
crossover that locks the tweeter in. But it is possible!). And I found that even weak,
cymbal and triangle sound is often more accurate than in complex crossover.

2) Second order series crossover. If you're not familiar with series crossover, it is a
highly drivers-dependent crossover.

3) Similar with the second implementation but with a resistor (minimum of 10 Ohm) in
place of the capacitor. The direct advantage is the NATURAL sound and the great
TRANSIENT. How to cope with the disadvantage is the design challenge. Good
enclosure (floorstander) is mandatory to take advantage of the bass characteristic.

SUGGESTED IMPLEMENTATION FOR THE PROJECT

The last implementation is the one I suggest for the "newbie" project for several reasons:

1) P13WH+D27TG+5uF has been suggested as refference and my suggested crossover
is very close in character with the single cap crossover (You know, comparing it with 4th order
speakers like The Esquire is sometimes like comparing an orange to an apple. I mean, with
high order crossover you get a smooth response but often bad transient and clinical sound).

2) It is also very cheap. You don't need high quality big inductors. Because the values
are relatively small, you can wind your own inductor using big copper wire from high power
transformer. The problem is you will need an inductance meter to match between the left
and right (Anyway, you will need the inductance meter)

3) The crossover can be tweaked by newbies with low fault tolerance. But because existing
theories don't help much (except for driver response graph and Fs may be) IMO this require
a good ear which usually is not possible with newbies OTOH, enclosure can be a problem.

4) This doesn't require a hi-end amplifier. A tone control or bass processor can be used with
minimum damage. But in the audio chain the source is the next important thing after the
speaker. Here we have many (clean) FM radio stations. If the same situation applies to you,
you can hear a "real" sound using cheap radio system

Frankly, I guess the D27 is not good enough for this implementation. But who knows?

QUESTION ABOUT INDUCTORS (OFF TOPIC)

I have spent some time working with inductors and component orientation in the crossover,
but unfortunately not enough time and effort to draw a conclusion. When I read about
speaker project, I have never read about this either.

Originally, I tried both ways of inductor orientation. And I found that the bass sound was
smoother when you feed the woofer with the inner end of the coil. I thought that like
capacitors, inductors should pass the current from outer end to the inner end (But
what if the inductor is put in the "negative" end??)

Based on limited observation, I have been long using inductors in the positive side with
inner end of the coil towards woofer (or ground). When once I realized that the analog
signal is AC, I started to question this. I don't have enough time to further observe this
but in this crossover I use different orientation than what i usually stick with! I don't
remember how I came to this orientation but I don't have time to reconfirm.

WARNING

I'm also a newbie. I don't know much about speaker design theories. I have experiences, but
as a hobbiest I tend to take the "out of the box" way than studying the "not so complicated"
theories or doing the plug and play approach.

That's the first warning (interpret it by yourself). The second is you should guard your own
tweeter. I've never used high power amplifiers, especially when working with crossovers.
I used amplifiers with sufficient output protection.

Anyone challenged? Please tell me what you think.

Jay.
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Old 6th April 2004, 01:42 PM   #126
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Jay, I think that was the idea that x .onasis had in mind that people would build this thing and tweak and report their findings which would be great assistance to newbies. What was listed was a starting point that should sound good and act as a datum.

I sent x. onasis a series xo to try. I don't know if he has tried it yet as it was an alternative to the 5uF cap xo.

Have fun.
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Old 6th April 2004, 03:23 PM   #127
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Yes rabbitz sent me his xover design. I've got the parts and will implement it soon and report on the sound.

I someone in a hurry to know? There seemed to be dimished interest in this project. Without reading back thru the thread, my observations are as follows.

They're small, so you're tempted to place them near a monitor...sheilding is an important consideration.

With the single cap, the first impression was very detailed mids, upper mids and highs. Surprising clarity and soundstage and SPL's for small bookshelf sized speakers. Bi-amping another step up in detail, plus the ability to tune for taste and room. Clearly (to me) where xover money should be spent.

Bass is not there, so a sub is necessary and that integration must happen pretty high. I wonder why a three-way using these drivers isn't a common DIY project, well, not that I know of anyway.

I haven't yet built the Alpha TLb, but I can see the potential for a great speaker. However with price the formost criteria, it wont be the "bang for the buck" 4 TB 871s in the configs we've seen posted here deliver, or the full range delivered by Stryke towers using single SA 071 & Tw1. (even if the xover is the most expensive part) Yet the Stryke's are not as efficient, and that is certainly a consideration.

My experience with full range drivers is still limited, but frugally, (say $125 or so for a completed pair) the mini array with the 871s is my reference. For two-ways, my advice would be to get (or build) an active crossover if you're new to speaker building, and want great sound from inexpensive drivers, which is what this thread is partly about.

That said, The "Esquire ala Rabbitz" is a decent, small speaker, and with a nice finish will always have a home.

I'm still interested in further ideas with the Vifa drivers. Is there a reccommendation we find another design using the P17 rather than the P13?
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Old 6th April 2004, 08:29 PM   #128
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I'm certainly interested! Please post your findings, x. onasis; I am in a hurry!

I was a little skeptical about the single cap...does the tweeter sound harsh? A question to ponder: Will the P13 sound better in the midrange with a low-end cutoff?

Another design idea would be dual P13s for better bass, maybe MTM.
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Old 6th April 2004, 08:37 PM   #129
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Quote:
Originally posted by coolkhoa
Another design idea would be dual P13s for better bass, maybe MTM.
Or bipolar... no baffle-step, push-push loading, and still retain the ability to XO with a single cap. An MTM would require a lower, more complex XO

Click the image to open in full size.

Can't remember the name OTTOMH, but an Aus 2.5-way MTM with 4 x P13 (be better with the bottom drivers on the back -- but then you wouldn't see them in the showroom )

dave
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Old 6th April 2004, 09:36 PM   #130
DeonC is offline DeonC  South Africa
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Question Re. 2.5-way?

Hi Dave

What about a 2.5-way? With the proposed baffle width (170mm), the baffle-step frequency will be circa 2kHz. So the upper P13 can have a 1st order XO at 2kHz, the lower P13 run full-range, and the proposed 5uF cap on the D27TG.

Furthermore, how about changing the tweeter for the Vifa XT19TD00-04 " Dual Concentric Tweeter? Or any of the Dual Concentric Tweeters for that matter? Should be a killer speaker.

Enjoy,
Deon
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