Project M2 DIY Thread

[Robh3606]

Hello 4313B

Ideal didn't use DCR in the model figured I would wait and just wait and measure the coils when I got them and adjust as needed if there was a significant change.

Rob

[srm51555]

There is actually a very simple way to measure system/cabinet resonance with a minimum of SW & HW. If you can connect your computer to your preamp / power amp and play music from the computer you can do this.

Rob, Thomas, and friends,

I finally took a cabinet resonance measurement last night and found the cabinet looks to be tuned to 27hz +/- 0.5hz. Cabinet size and port information can be found in post 35.

For those who want to try this also, I initially used my Crown dci that has DSP built in and didn't receive a accurate measurement so I pulled out an A/V receiver and received more accurate results. I used an free download of signal generator POS recommended for my iPhone and a 50ohm resistor. Never realized taking this measurement was this easy.

Thanks,
Scott

[4313B]

I posted this in the M2 thread.

Using a volume of 5.2 cubic feet, a tuning frequency of 27hz, port diameter of 3” and the number of ports needed set at 2 using, the precision port calculator recommends this port http://www.parts-express.com/precisi...-tube--268-368 (and it's inner mate) to be set with a total length of 8.85.

Rob, Thomas, and friends,

I finally took a cabinet resonance measurement last night and found the cabinet looks to be tuned to 27hz +/- 0.5hz. Cabinet size and port information can be found in post 35.

For those who want to try this also, I initially used my Crown dci that has DSP built in and didn't receive a accurate measurement so I pulled out an A/V receiver and received more accurate results. I used an free download of signal generator POS recommended for my iPhone and a 50ohm resistor. Never realized taking this measurement was this easy.

Thanks,
Scott

Nice!

And it looks like you guys figured out two 16 uF capacitors in series for the biased version of the network.

[pos]

And it looks like you guys figured out two 16 uF capacitors in series for the biased version of the network.

SCR/Solen do have a 16uF cap in their catalogue, but I did use the same unbiased WIMA caps as in the original network because I wanted to have something as close as possible to the original, and in the end I will probably either remove most of that network from the signal path, or use another compression driver...

Another thing to consider with the charge-coupled approach here is that the caps are in front of a 9dB lpad and a 32 ohms driver (-6dB compared to a 8 ohms driver).
That is a 15dB hit in voltage swing, which translates to a 0.178 factor.
In essence, that means that one would need a 50V battery to replicate the effect of a 9V battery used to charge a cap in front of a 8 ohms driver without lpad.
Using a 9V battery here is equivalent to using a 1.6V battery for a 8 ohms driver without lpad.

[srm51555]

Another thing to consider with the charge-coupled approach here is that the caps are in front of a 9dB lpad and a 32 ohms driver (-6dB compared to a 8 ohms driver).
That is a 15dB hit in voltage swing, which translates to a 0.178 factor.
In essence, that means that one would need a 50V battery to replicate the effect of a 9V battery used to charge a cap in front of a 8 ohms driver without lpad.
Using a 9V battery here is equivalent to using a 1.6V battery for a 8 ohms driver without lpad.

This would be my case. I thought that doubling the value and doubling quantity was good on all capacitors in a network. Electronically, It should be the same as the original network or is this incorrect?

[4313B]

SCR/Solen do have a 16uF cap in their catalogue, but I did use the same unbiased WIMA caps as in the original network because I wanted to have something as close as possible to the original, and in the end I will probably either remove most of that network from the signal path, or use another compression driver...

Another thing to consider with the charge-coupled approach here is that the caps are in front of a 9dB lpad and a 32 ohms driver (-6dB compared to a 8 ohms driver).
That is a 15dB hit in voltage swing, which translates to a 0.178 factor.
In essence, that means that one would need a 50V battery to replicate the effect of a 9V battery used to charge a cap in front of a 8 ohms driver without lpad.
Using a 9V battery here is equivalent to using a 1.6V battery for a 8 ohms driver without lpad.

I will probably use a modified version of the biased 4367 network should I decide to follow through with the LCR plan.

[pos]

This would be my case. I thought that doubling the value and doubling quantity was good on all capacitors in a network. Electronically, It should be the same as the original network or is this incorrect?

Yes Two 16uF in series will be equivalent to a single 8uF cap.
The question is does a 9V battery provide enough bias to get a benefit at normal listening levels here?
It probably depends on what you call "normal"

[johanwholst]

I know it has been mentioned before, but when test mounting the waveguide today, I noticed that it is not flat. Seems like it is slightly curved and does not touch the baffle in upper left corner.
I have not bolted it down yet, and maybe it gets pulled straight.

What say you who have completed their builds with M2 parts?

[dprice]

I used gasket tape to seal between the waveguide and baffle. Not sure if the waveguide was flat or not since the cabinet frame hides that detail.

A little more info here...

http://www.audioheritage.org/vbullet...-DIY-M2-thread

Good luck!

[4313B]

Hello 4313B

Ideal didn't use DCR in the model figured I would wait and just wait and measure the coils when I got them and adjust as needed if there was a significant change.

Rob

I entered your network into LEAP along with my data and it came out great. Gotta love that top end from the Mg. Thank you for reposting this information!

[johanwholst]

Little update:
Glued up both cabinets this week, and cut thread for WG mounting.
I cut it using M5 and fastened with threaded rod and wing nuts. Fits perfectly, and the slight curve in the waveguide straightens out when thighen it slightly down.

Now remains sanding, priming and finishing. They will be playing music in a week!

[pos]

Yum

[4313B]

They should sound fantastic!

[johanwholst]

I believe so too! The whole construction just seems to look right.
Now it's just a matter of not rushing things in the end and put good effort in finishing, damping and sealing of waveguide.

[Robh3606]

I entered your network into LEAP along with my data and it came out great. Gotta love that top end from the Mg. Thank you for reposting this information!

Hello 4313B

That's great! Thanks for letting me know I am on the right track. Yeah you sure do have to like that top end!

Rob