My B4N MTM project thread....(3 threads merged)

[mintos]

I recently put together a cheap pair of B3S MTM. Sounded great, but I wanted something with more bass so I was looking at the B4N and put together the following.

004-4 Yes Dayton DNR-4.0 4 Ohm 10W Precision Audio Grade Resistor
$0.98 $7.84
027-338 Yes 8.0uF 100V Non-Polarized Capacitor
$0.58 $4.64
027-427 Yes Dayton DMPC-6.2 6.2uF 250V Polypropylene Capacitor
$2.68 $5.36
255-024 Yes Jantzen 0.20mH 20 AWG Air Core Inductor
$3.24 $6.48
297-429 Yes HiVi B4N 4" Aluminum Midbass Round Frame
$16.83 $67.32
264-834 Yes Tang Band 25-1166SJ 1" Neodymium Tweeter
$19.49 $38.98
269-360 Yes Terminal Cup with Filter
$0.39 $3.90
Subtotal: $134.52

There's a .58 mh inductor from 2 of the 10 Terminal cups on sale.

The x-over looks very smooth

Any suggestions before I buy the parts?

[Undefinition]

I recently put together a cheap pair of B3S MTM. Sounded great, but I wanted something with more bass so I was looking at the B4N and put together the following.

The x-over looks very smooth

Any suggestions before I buy the parts?

The B4N will definitely deliver some surprisingly big bass. The design looks OK to me, however it's hard to make a call, since I don't know where you got the measurements and I can't see their phase interaction.

[ThomasW]

Might want to consider 6.5" drivers if you really want more bass.

[---k---]

6.5" are for wusses. Use 8" or go home.

[mintos]

This is just pure simulation from manufacturer's data. I'm also concerned with the side. It's just for a small PC desk.

[mintos]

In terms of design priority, I need it to be

1. Small
2. Cheap
3. Great Bass

8" or larger will meet only the lowest priority

[---k---]

I know that you said you wanted an MTM, but did you see the design that Paul just posted with the B4N. It is small, cheap and designed to sit on Paul's desk. Might be the ticket.

http://undefinition.googlepages.com/diy-overnightsensations

[mintos]

I saw it. I think the MTM design gives better bass and SPL. My simulated x-over shows spl at 86 avg vs 82. There's also more x-over parts in that design :/

[mintos]

The tweeter is in reverse polarity

[Bent]

using 2 - B4N's should help with the low sensitivity issue.

[mintos]

Crossover parts can play sounds?

I just finished soldering a crossover together and when I went to try it out, I noticed that there was sound coming from it even without hooking it up to a speaker! If I tried to turn up the volumn, my amp goes into protect mode. Did I make a mistake? What's making the music in the crossover?

[JonMarsh]

Without the speakers connected, you may be getting some high Q resonance- and phase shift- that could be the cause of your amp shutting down. BUT, it's more likely you made a wiring error.

And yes, crossover components can make sound- but if they do so, that means energy is going into physical processes that shouldn't be happening; this is one of the reason there's a market to make very high quality wound caps and inductors to prevent physical vibration, because if the energy is leaking off there partly, it's changing the sound delivered to the drivers.

Check your wiring carefully first.

[mintos]

wiring looks like the picture. Seems to work if I connect the speakers to it.

[jcocomo]

Mintos,

Don't run power into the cross over with out a load (speaker) connected. Your amp went into protect mode because it was seeing very complex impedences without the speaker attached to the output of the x-over. The sound you heard was likey the electrical energy through the coil. Vibrations of the windings are coincident with the electrical audio currents. Thus the windings or other vibrating parts will produce a sound wave that is representative of the electrical signal.
Cheers,
John...

[mintos]

oh ok... so long as it's not unusual I'm ok with that. Now the question is do I need to replace any parts? The ones in my picture with the red dots next to them are cheap caps and inductors. The .58h is the inductor off the speaker terminal part-express had on sale for 38 cents.

[mintos]

I put a speaker on it and turn up the volumn. My amp still goes into protect mode, but only at a higher volumn. Maybe I need to have all 3 speakers hooked up so the imp looks normal. All the caps are rated 100V or 250V and the inductors are 20 guage.

[Saurav]

You need all the drivers hooked up. If you just ant to play around, I think you could use 8 ohm resistors in place of the drivers, I *think* that should help with preventing the amp going into protection. If it's still doing that, you may have shorted something somewhere.

[Face]

What speaker is this, do you have an impedance curve? What receiver are you using? 20ga seems small for a woofer inductor.

Claritycap MR series and Duelund build their components to prevent resonance(what you're hearing).

[mintos]

I'm going for cheap (cost effective) so using 20 gauge inductors and cheap 100v caps to save cost. These speakers won't get more than 50watts. So long as the resonance issue is normal, I'm ok with that. yeah, thanks all. Since I don't have any testing equipment, I test by hooking my crossover to my amp. Then I play a song and see if the HP and LP sound like it's doing the intended work on a B3S. I switch the B3S between HP and LP, so I heard sound from the crossover when switching.

[benchtester]

Regarding the crossover playing sounds, I had a sand cast resistor that emitted the music audibly that was going through it. :E

[cjd]

If you don't want to put speakers on there at least put resistors of appropriate impedance across the intended speaker locations!

[AJINFLA]

If your crossover started playing mozart while you fed it tests tones, I'd be real worried. Otherwise, as suggested, place a load across it.

[mintos]

MTM crossover model, woofer offset issue

First, I don't have any measuring equipment, so all the FRD and ZMA I have is from spltrace and manufacturer's data. That said, I was modeling a crossover for the B4N in MTM config with speaker workshop when I tried out the offset input. I put in -4" and +4" centered on tweeter. That introduced two dipps in the previously flat reponse graph. I assume this is due two the two woofer canceling each other out. How do I get rid of these dips? Is it even audible? I uploaded the before offset and after offet crossover pics.

[Saurav]

The offset input in Speaker Workshop is in the horizontal direction, into and out of the baffle. What you just did is tell SW that one woofer is 4" behind the tweeter, and the other is 4" in front of the tweeter. In reality, both woofers are probably an inch or so behind the tweeter (depending on the depth of the drivers).

I found this website really helpful in understanding how to use SW:

http://www.claudionegro.com/

[mintos]

ahh.... that would explain it. So there's not input for vertical offset? Or does that have little impact on the response graph?

[Saurav]

Read the manual I don't remember seeing an input for vertical offset. There are different ways of measuring drivers, in one of them the vertical offset gets factored in automatically. Since you're working from 'stock' SPL files, you might be able to do some math and factor in the vertical offset in that value. Basically, for your listening distance, then figure out how much further the woofer is from the listener that the tweeter (which is a combination of the vertical offset and the driver depth difference), then put that in there. I've never done this, so I'm not sure how well it will work. Since you're not working with accurate phase measurements, maybe you don't really care anyway, so just using the driver depth might get you close enough. I'm not sure.