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Multi-Way Conventional loudspeakers with crossovers

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Old 21st September 2004, 08:19 AM   #21
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Quote:
Originally posted by Jennice
Why should less energy be transferred to the cabinet with this push-push design?
In push-push the two drivers are tightly coupled mechanically. They have equal but opposite motion. They therefore activly cancel each others newtonian forces so that this (mechanical) energy is not transferred to the cabinet.

The sane amount of acoustical energy is impaxting the enclosure - one of the reasons i like TLs is that they tend to be low pressure.

dave
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Old 21st September 2004, 08:36 AM   #22
Jennice is offline Jennice  Denmark
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Dave,

Do you mean that the push-push drivers should somehow be physically connected (glued baqck-to-back), or do you refer to theair in the enclosure when you say that they are mechanically connected?

If glued back-to-back, I can't see how it'll ever make it to the rear of the speaker, unless you have very funny looking cabinets.

Jennice
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Old 21st September 2004, 04:37 PM   #23
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Quote:
Originally posted by Jennice
Do you mean that the push-push drivers should somehow be physically connected (glued baqck-to-back), or do you refer to theair in the enclosure when you say that they are mechanically connected?
Some people go as far as gluing them -- i prefer to be able to disassemble them.

There are some few drivers designed so that a bolt can go thru the polepiece to attach the driver to the cabinet... a pair of those would allow very good coupling.

Click the image to open in full size.

More common is the use of a brace such as a dowl to connect the 2 drivers.

Click the image to open in full size.

If you add the ready rod to attach the fronts and pull the drivers together you get reaaly close to ultimate.

Just a 2x4 with hot glue used here:

Click the image to open in full size.

dave
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Old 21st September 2004, 06:13 PM   #24
Jennice is offline Jennice  Denmark
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Dave,

Thank you very much for the pic's. They say more than 10^3 words.

One question, though: How would you glue the second driver (on the speaker that is shown with the driver removed)?
If the glue hardens slowly enough, how do you ever get the driver out again, or is the spacing rod only glues to the one driver?
Is it made a tiny bit loner than the distance between the drivers, so that there is tension on it to begin with?

Jennice
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Old 21st September 2004, 07:54 PM   #25
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Quote:
Originally posted by Jennice
One question, though: How would you glue the second driver (on the speaker that is shown with the driver removed)?
If the glue hardens slowly enough, how do you ever get the driver out again, or is the spacing rod only glues to the one driver?
Is it made a tiny bit loner than the distance between the drivers, so that there is tension on it to begin with?
The trickiest thing is getting the brace the right length... if it is shorter, then you can add a spacer (on 1 sub we did, a single sheet of paper was all that was needed.

On the pictured speaker i used hot glue... it basically just holds stuff in place and doesn't really glue it. The driver easily comes out with a bit of a tug. (matter of fact the stuff is so wimpy you sometimes find yourself "gluing" it a couple times because it doesn't even hold the brace in place.

dave
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Old 21st September 2004, 11:06 PM   #26
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Thumbs up anyway....

I do recommend anyone to search and choose the drivers before to start any crossover choice or optimization.

This is specially true if you are newbie on DIY speakers matter. I do this because different brands (and models also) really have different response too.

If a midbass unit starts to roll-off at 3.5K and respond -20dB at 8K, you can not cross it near 3K or higher unless you want to sum driver's response to crossover one and get +20 dB/oct slope acoustic filter at low pass section.

I think MTM D'Apolito configuration is a good one since you know the features and use them. Uniform vertical response, combined with the fase relationship of second or 4th order crossovers (acoustic ones, of course) does very good results and the industry knows it. I'm trying to pick up the URL's where you can read about this and will post here soon.

I hope do not got you even more confused. Anyway I did learn it reading, reading and reading and reading
Internet is a great source of good information, since you are at right location.


My 2 cents...

Euclides.
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Old 22nd September 2004, 12:42 AM   #27
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Default links

here some links to read about


http://www.rane.com/pdf/note107.pdf

http://www.rane.com/library.html

http://sound.westhost.com/articles.htm

this well known but...

http://www.linkwitzlab.com/crossovers.htm

this also:

More xover questions



hope to help.

P.S. on above I meant uniform response as simetrical response of the polar lobes, as they are equal above and below the tweeter axis, and stucked by false cognate... "fase" as phase...
sorry my bad english...
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Old 22nd September 2004, 06:00 PM   #28
sbolin is offline sbolin  Thailand
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Hisatugo, thanks for all the links, very helpful...in making more confused!
The ESP article says that more than a 2nd order is useless, and impedience compensation is good. The rane article extolled the virtues of a 4th order LR crossover (active, though). Everyone has their own opionion, and usually they have some merit. As a beginner, it is difficult for me to gauge which is reasonable and which isn't. Good stuff...
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Old 23rd September 2004, 02:18 AM   #29
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Talking oh... sorry... (long answer)

As I would know, several opinions make this indeed.



I was trying to show you how important is to choose your drivers first. If you make this choice and have the data on hand, you will make all the decisions more confident.

There are drivers that fit well for 2nd order Xovers and others 4th order (acoustic I mean, if the driver roll off 1st order and you sum first order xover you get 2nd order acoustic response if things are right designed)

But I think more than 2nd passive is something difficult to realize indeed. Have you tried to simulate the circuit in some computer software? To get phase and response fit the requirements for linear and coherent is a real pain. To simulate response of the drivers is another pain. So you can imagine this in real life soldering, sticking, testing, hearing, soldering again and again and again...

So, If you don't mind I say it one more time: choose your drivers first and after that, have it on your hands. After that again, make some measures, if possible in the room you intend to hear them. The companies can NOT do this beacause they never know where their loudspeakers will play. BUT YOU CAN. This is an advantage, and if you move, you can modify it to new location.
Is this not good??


So with the measures on hands, (impedance, Qts, Le, RTA frequency response) you can sit down and think on how to cross it.

Unless you are at least an eletrical eng. student, I do sugest also to search for drivers and projects well known and already succesfully mounted. They include xover circuits, already tweaked to last note and you will not get in error. ( Mr. Linkwitz has very good ones). You will learn A LOT OF DIY audio with them.

The initial projects choosed and realized by this way will not discourage and you can start a new one with progressive challenges.

I also suggest you do not loose the focus of the project: is it to be a construction project OR is it a loudspeaker for music and pleasure project? You can do both but it will NOT be the first one that let you get both. Because you (and me too) will always think something could be better and the next project will be better and so on

If you intend to hear music do remember to consider you taste for music when choosing drivers also. Hear some of them before to buy... if possible of course. Or at least, follow recomendations of somebody with similar music preferences but with more experience with different drivers.

To construct good loudspeakers IS A REAL possiblity. They should satisfy nobody but ourselves (of course some friends are part of us ). I would consider me as a newbie here, as our fellows have years more of experience and critical reading this forum was a great source of good info. I constructed 8 pairs of loudspeakers since the first one, 6 years ago. They ended trash or sold... I have only the last and the new one.

This 8th pair intend to be the last as I think is time to spend energy on amplifiers and maybe the digital source now.

Good learning!


Best Regards. Sorry for long answer, took too much of your time.

Euclides.
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Old 23rd September 2004, 05:35 PM   #30
sbolin is offline sbolin  Thailand
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Hisatugo-
Thanks for the advise. I appreciate all the help I can get, I am new at this, but like to learn. Reading many opinions is good, it just seems that many are contradictory, and without any experience it is hard for me to judge the good ones from the bad.

Thanks again!
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