Zaph's ZMV5 design

[454Casull]

Can anyone confirm that R4 is a 2.0 ohm MO resistor? I can't seem to find that value on madisound.

[gtforme00]

From the looks of the impedance curve it looks like it is a 2 ohm. They are out of stock on the Eagle MO 2.0, I ordered a 15W wire-wound. Maybe you were looking at the Mundorf section rather than the Eagle section?

http://www.madisound.com/catalog/pro...roducts_id=203

-David

[ashaw]

Do you know how one can obtain the MCM 55-3870 woofer in australia

[mtnickel]

I also got the 15w wirewound. Zaph posted info on the changes made. If you're anal, like he said, get 2 and parallel them.

On a side note, i even saved some money on the 12uF and 8.2uF as well...
got the surplus 10uF + 2 uF, and got 3 x 2.7uF for 8.1uF (close enough for me).
Savings aren't much over solen caps, but hey it's a budget system. they are poly and mylar too with plenty high voltage ratings, so should sound fine to me.

Mark

[Jay_WJ]

This design must be very nice for the price. The Vifa DQ25SC has excellent distortion performance according to Zaph's test and can be crossed at 2 kHz LR4. What a great neo tweeter at only $16! I actually use this tweeter for my upcoming 2-way design dubbed "Poor Man's High-End Monitor." Two people already started building the design. The build cost will be double the ZMV5's, due to the SB Acoustics 6.5" woofers, but it aims for significantly higher performance as well. This will replace my Dayton RS180S/Seas 27TDFC 2-way design in its price category. The info is at:

http://www.geocities.com/woove99/Spkrbldg/jays_blog.htm

In my design the Vifa tweeter is also used with LR4 at 2 kHz as in Zaph's design. But the topology of tweeter network is a little different from Zaph's. Although the Vifa has low distortions down to 2 kHz, its high resonance (1.4 kHz) point can be problematic to obtain a good target rolloff. Because the impedance peak at Fs is not that high, the traditional L-pad trick with a low shunt resistor value can be used to control this, which is what Zaph did in ZMV5. But this technique works effectively only when the required amount of padding is sufficiently large. In my design, the tweeter output needs to be 4 dB higher than that in Zaph's design. If I used an L-pad, I'd need to increase the shunt resistor value or decrease the series resistor value, or do both. But the problem is that the former way makes the L-pad less effective in controlling the impedance peak and the latter way lowers the system impedance too much. There is another technique that can be used in this situation. Using a very low value for the shunt coil in an electrical 2nd order filter effectively controls the impedance peak. This method is suitable for a tweeter with low impedance---otherwise, a shunt resistor is necessary. The Vifa fits well since it's a 3 ohm DCR tweeter. So, in my design, I skipped an L-pad before the tweeter and instead used a low 0.1 mH shunt coil. By selecting a suitable series cap value and using a single padding resistor before the whole network, I was able to achieve a nice, smooth LR4 rolloff. A Zobel with a small cap was also necessary for top octave response shaping. The chart below shows tweeter electrical transfer functions resulting from two appraoches: the L-pad method and the small shunt coil method. In the case of the L-pad method, I chose its values so that the shunt resistor is as small as possible while the target SPL is achieved without too low system impedance.




As you can see in the plot, the tweeter's resonance peak is reflected at 1.5 kHz on the transfer function obtained from the L-pad approach though it's not that bad. For the small shunt coil approach, however, this effect is virtually not present.

-jAy

[phobik]

I think my head hurts from trying to read and understand that.

So your design goes up there along Zaph's ZD5?
And I thought the new ZMV5 where actually my cheap-monitor--DIY-miracle come true.

Well not so cheap compared to HiVi, but eventually a much better contender to being some decent nearfields, as I can't hear any mixing&mastering subtleties with my current desktop speakers/cheap headphones.

But I don't really wan't to go above the 150$ for my first project, I'm trying to maximize bang for the buck, not also to avoid finish some cheap design only to find out it's very lacking for the purpose I want.

Does anyone know where to buy these drivers in europe by the way?

[jcandy]

Rather than starting a new thread, I thought I'd post a few photos of a recent ZMV5 build. I did this mostly as cabinet design test. The goal was to avoid the use of both MDF (because I value my lungs) and a table saw (because I value my fingers). Instead, I used the Festool TS 55 track saw and baltic birch plywood. The finish is nothing to write home about, but that was not the focus of the project. They are currently serving as my computer speakers (the reason why I chose to use a front port), driven by an Adcom GFA-535II, with an M-Audio 2496 DAC in the computer running linux!

The bass extension of the ZMV5 is limited when running full range, and they are a bit large for a 5" 2-way. Despite these caveats, I am very fond of them. Thanks to Zaph!

The Festool

Rear baffle attached with hex bolts (unfinished)

Finished ZMV5

Art photo