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DIY MTM Tower speakers
http://dcaudiodiy.com/phpBB3/viewtopic.php?f=4&t=1301
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Author:  mix4fix [ January 6th, 2019, 4:09 am ]
Post subject:  Re: DIY MTM Tower speakers

mix4fix wrote:
Would a 5 inch x 7 inch thin piece of wood plaque be enough for it?

Found it at Walmart.


It would be cheap. Or...

2-way-speaker-crossover-pc-board-for-5-x-7-terminal-cup--260-116
https://www.parts-express.com/pedocs/sp ... -47130.pdf

Or...

Use those crossover boards as suggested.

Author:  mix4fix [ January 8th, 2019, 7:34 pm ]
Post subject:  Re: DIY MTM Tower speakers

Stuart Polansky wrote:
Steve,

Once you get all of the crossover parts, please measure them physically. If you send me the dimensions, I'll be happy to lay out the build in CAD to help you put them together on perf board.

Stuart


10uF
Dimensions: 22 mm Dia. x 45 mm L

20uF
Dimensions: 27 mm Dia. x 55 mm L

2.5mH
Dimensions: 2-1/2" D

0.60mH
Dimensions: 2-1/4" D

2.4 Ohm
Dimensions: 48 mm L x 10 mm W x 10 mm H

Author:  Stuart Polansky [ January 9th, 2019, 6:25 pm ]
Post subject:  Re: DIY MTM Tower speakers

mix4fix wrote:
Stuart Polansky wrote:
Steve,

Once you get all of the crossover parts, please measure them physically. If you send me the dimensions, I'll be happy to lay out the build in CAD to help you put them together on perf board.

Stuart


10uF
Dimensions: 22 mm Dia. x 45 mm L

20uF
Dimensions: 27 mm Dia. x 55 mm L

2.5mH
Dimensions: 2-1/2" D

0.60mH
Dimensions: 2-1/4" D

2.4 Ohm
Dimensions: 48 mm L x 10 mm W x 10 mm H


I did get the PM Steve.

The forum doesn't allow more than a single PM attachment, so I am posting it here for you to download.

Attachment:
Steve-XO-connections.PNG
Steve-XO-connections.PNG [ 55.5 KiB | Viewed 1120 times ]


Attachment:
Steve-Board.PNG
Steve-Board.PNG [ 36.76 KiB | Viewed 1120 times ]


Attachment:
Steve.PNG
Steve.PNG [ 59.2 KiB | Viewed 1120 times ]

Author:  HAL [ January 9th, 2019, 9:20 pm ]
Post subject:  Re: DIY MTM Tower speakers

Looks good.

Just a thought, but to minimize the inductor mutual coupling, you might turn one 90 degrees and use wire ties to hold it to the board.

Author:  Stuart Polansky [ January 10th, 2019, 12:06 am ]
Post subject:  Re: DIY MTM Tower speakers

HAL wrote:
Looks good.

Just a thought, but to minimize the inductor mutual coupling, you might turn one 90 degrees and use wire ties to hold it to the board.


Rich,

Will the fields of those two inductors interact to a significant degree with that distance between them?

Author:  HAL [ January 10th, 2019, 12:16 am ]
Post subject:  Re: DIY MTM Tower speakers

If the large inductor has a metal core, the magnetic field strength can be pretty high.

It is hard to tell without an EM field model or measurements, so I tend to err on the side of just minimizing the interaction with separation and orientation.

Here is a guide I use when I have tried passive crossover layout. I tend to use #6.

Attachments:
image.jpg
image.jpg [ 32.27 KiB | Viewed 1102 times ]

Author:  Stuart Polansky [ January 10th, 2019, 8:38 am ]
Post subject:  Re: DIY MTM Tower speakers

Thanks Rich,

Great post and information. Saved the chart.

Steve, take note. You can make the board ~3/4" longer and move the inductors farther outboard, or, as Rich suggested, rotate one 90 degrees in the pictured axis.

I had the inductors placed ~7.2" apart center-center. Rich's chart suggests 7.88" minimum.

Stuart

Author:  Cogito [ January 10th, 2019, 9:50 am ]
Post subject:  Re: DIY MTM Tower speakers

Stuart Polansky wrote:
Thanks Rich,

Great post and information. Saved the chart.

Steve, take note. You can make the board ~3/4" longer and move the inductors farther outboard, or, as Rich suggested, rotate one 90 degrees in the pictured axis.

I had the inductors placed ~7.2" apart center-center. Rich's chart suggests 7.88" minimum.

Stuart


See, what I said is true.

You guys did not bother the threads before complaining about me, Tom and Walt. If you were really interested in the subject being discussed, you would have seen the 2nd post from the top on page 10 and the discussion that followed. A good rule to follow: If you dont read the content in the thread, dont complain about the thread.

Author:  Stuart Polansky [ January 10th, 2019, 12:00 pm ]
Post subject:  Re: DIY MTM Tower speakers

Wrong on every count. I DID read the entire thread, including the second post on page ten.

Of course, and in close proximity, 90 degree angles between inductor or transformer cores is required. I never disputed that.

Here is the issue: when is it required? At what distance, frequency and current is it prudent? Must the inductors used in crossovers of speakers placed ten feet apart be placed at 90 degrees from each other? Of course not. Must transformers in monoblocks, sitting four feet from each other be at right angles? Obviously not. Do inductors three inches apart on the same chassis? Of course they do.

BUT, at some combination of distance and field strength, it doesn't matter. That's the issue. Rich has provided a handy rule-of-thumb guide to the issue, at least as far as air cores are concerned.

In the drawing I made for Steve (which FOR THIS VERY REASON I would have only sent by PM, save for the single file limitation) the inductors are spaced at 7.2" Rich's drawing suggests a 7.88 minimum. I bet it would be sonically indistinguishable either way. But you are welcome to prove me wrong

You prove the wisdom of those who avoid posting on this site by your post attacking me over nothing.

Author:  Pelliott321 [ January 10th, 2019, 12:04 pm ]
Post subject:  Re: DIY MTM Tower speakers

I would keep the cover external until you are satisfied with the sound

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