textbook plan with TB tweeter and M4N

[mikem]

Hello here is my textbook plan. Any thoughts? I already have the TB and the M4N is on ebay for $6.25.

Two Hi-Vi M4N in series 16ohms
One TANG BAND 28-847SA SHIELDED NEODYMIUM DOME TWEETER 8 ohms
Crossover @ 2500Hz, 2nd LR

C1=4.0uF

L1=1.0mH

C2=2.0uF

L2=1.0mH

L-pad @ 8db, R1=4.8ohms R2=5.3ohms
Thought about a zobel on the M4N’s
Haven’t thought about box dimensions yet and probably will be ported if I can figure that out.

Thanks

[shawn_a]

It's not the ugliest I've seen but it's gonna be a fun one to tame with a textbook crossover. Whatever gets your kicks but I was messing around with the M4N's I got from the same seller (very good service FWIW) and I can tell you from my experience it was not looking very promising when it came to a nice and simple crossover. I'm still going to use mine but it looks like the filters are going to cost me more than the drivers.

Also, if you can I would highly suggest using the M4N's in parallel rather than series. They have a low sensitivity as it stands and they will need all the help they can get when it comes to BSC.

shawn

[unknownuser]

Provided Link: xover


Thanks for the info. I saw this design. What if I used the same setup with the M4N's as this and created a new design using the TB with it?
hongrn would you mind if I used some of your design?

Yeah I know the inductors are exspensive for this.

btw what does BSC mean?


(Originally posted by: MikeM)

[shawn_a]

I'm sure Uncle Hong won't mind one bit about mods to his design. He might even pop his head in and help out a bit.

First off, BSC is the abbreviation for Baffle Step Compensation. Read this little anecdote by the resident xover guru, Curt C., to get a better grasp on what it is and why it's something that needs attention.

<A HREF="http://www.geocities.com/cc00541/bafflestep.html">http://www.geocities.com/cc00541/bafflestep.html</A>

Now as far as the modifications needed to Hong's design you will probably need to do a small bit of reworking the high-pass at the bare minimum. Embarassingly enough, I haven't gotten around to reading his complete description of that project. I'm behind on everything now so it's on my list of things to do. I'm not very familiar with either the tweeter Hong used in his design or the one you plan to use. However I'm guessing that you might be able to cheat things a wee bit and use his low-pass section as-is. A lot of help I am, I know.

shawn

[Chris Roemer]

> Hello here is my textbook plan. Any
> thoughts? I already have the TB and the M4N
> is on ebay for $6.25.

> Two Hi-Vi M4N in series 16ohms
> One TANG BAND 28-847SA SHIELDED NEODYMIUM
> DOME TWEETER 8 ohms
> Crossover @ 2500Hz, 2nd LR

> C1=4.0uF

> L1=1.0mH

> C2=2.0uF

> L2=1.0mH

Your "textbook" xo will actually cross your driver config at 7.6 kHz.

If you really meant to double the LP coil (making it 2mH to account for the 16 ohm load) you'd then be crossing at 6.9 kHz.

> L-pad @ 8db, R1=4.8ohms R2=5.3ohms
> Thought about a zobel on the M4N’s
> Haven’t thought about box dimensions yet and
> probably will be ported if I can figure that
> out.

> Thanks

[Chris Roemer]

> Hello here is my textbook plan. Any
> thoughts? I already have the TB and the M4N
> is on ebay for $6.25.

> Two Hi-Vi M4N in series 16ohms
> One TANG BAND 28-847SA SHIELDED NEODYMIUM
> DOME TWEETER 8 ohms
> Crossover @ 2500Hz, 2nd LR

> C1=4.0uF

> L1=1.0mH

> C2=2.0uF

> L2=1.0mH

Like I was saying, your textbook xo will actually cross these drivers near 7 kHz.

> L-pad @ 8db, R1=4.8ohms R2=5.3ohms

If you parallel the Hi-Vi's, you can open up the tweeter 4 dB. RS = 3, RP = 10

I get a 3rd order xo. Try:
HP: 17uF, .19mH, 13uF with L-pad

LP: .50mH, 55uF npe, .20mH with a Zobel
> Thought about a zobel on the M4N’s

Yup, try a 4 ohm resistor and a 25uF npe cap.

> Haven’t thought about box dimensions yet and
> probably will be ported if I can figure that
> out.

Hope you've got a good sub.

> Thanks

[mikem]

maybe I will rethink this plan. This is good advice. That's why I love this board.

I'll need to reconsider the benefits of these cheap drivers vs the work they will need.

Thanks again

[hongrn]

Mike,

Let me suggest an xo with this tweeter, and I'll get back to you.

Hong

[Chris Roemer]

> maybe I will rethink this plan. This is good
> advice. That's why I love this board.

> I'll need to reconsider the benefits of
> these cheap drivers vs the work they will
> need.

> Thanks again

I've fiddled around with PE's f.txt and z.txt files (as .frd and .zma) using the FREE standalone "XOverSim", off the "FRD Consortium" site.

I've managed to come up with an xo that's 86dB +/- 1.5 dB from 120 to 19,000 kHz.

HP: 2nd order (6.8uF npe cap, .90mH #20 coil)
w/ notch filter (3.3uF npe cap, .05mH #18 coil, 3.3 ohm 10w resistor - all in parallel)
and just before the tweeter, a 1.8 ohm 10w resistor for attenuation

LP: 3rd order (.60mH #20 coil, 47uF npe shunt cap, .15mH #20 coil)
w/ notch filter (47uF npe cap, .20mH #20 coil, 1.2 ohm 10w resistor - all in parallel)
and Zobel: 4 ohm 10w resistor in series w/22uF cap

If you take a look at the response curves (in the PDF files) for these 2 drivers, you'll see that they both have very wide bandwidths, but they are FAR from flat. If you can open the f.txt files for them and cut and paste the freq and SPL (dB) columns into a spreadsheet (even MS Works would be fine) you'll see that PE's actual measurements fluctuate even more wildly.

The M4n has some horrible junk going on from 5-6kHz and an even stronger "ringing peak" at 13kHz (this kind of stuff is very typical for metal cone drivers, even PE's aluminum and RS series have these problems). Even a 2nd order doesn't have the strength to push this junk down to where it doesn't interfere with the tweeter response range. Most 2-ways HAVE to use a Zobel 'cause w/o one the "impedance rise" of the woofer makes its value 3 to 4 times what it's nominally rated at. The Zobel and 3rd order xo suppressed that 13k peak, but I had to add the notch filter to reduce another spike near 1.5kHz in the crossover band.

That tweeter also has a broad but rather non-flat response. It's really only "full on" (rated dB) from about 6 to 18k. From there down to about 3.5 kHz there's a bit of a dip, then a rise from there down to 2.5 kHz. I used the notch filter to drop that 6-18k "hump" down to the level at 3k, then just rolled it off 2nd order below that.

I figure about $6 in parts for the LP, and $10 in parts for the HP, totalling $32 for xo parts for a pair of speakers. Dayton's -070 silk dome is around $15, and the 6.5" -305 or -306 can be had for under $20. That's what make the BR-1's such a good value, and these drivers can get by with about half the xo parts count.

If you move ahead with your parallelled M4n's, I'd suggest a 1 cf box with a 3"d x 11" port. That will tune the box to 38 Hz, but will still have about a 4dB rise at 90 Hz. That's because the Hi-Vi's really have an awful high "Q" (1.08) for a vented box, although that's what they recommend for this unit.

To get the lowest bass (vented) from the smallest boxes, you should be looking at woofers with a Qts in the range of .30 to .42 or so.

[mikem]

Thanks I appreciate it. I don't have software or knowledge yet on other than what I read in books and those free online crossover calculators.
But you got to start somewhere.

[mikem]

Thanks for working out a possible solution. $32 is not bad for the x-over parts. Hope it did not take you too long to figure out.

[mikem]