Project M2 DIY Thread

[pos]

Hello Scott,

Assuming the same impedance and SPL/W curves as the D2430K, here are equivalent networks that should result in same high-pass frequency and overall sensitivity (ie noise) :

32 ohm driver ( 20 ohm load,  9dB attenuation): R1=13  (30W)  ; R2=11   (10W) ; C=8
16 ohm driver ( 10 ohm load, 12dB attenuation): R1=7.5 (75W)  ; R2=3.3  (20W) ; C=16
 8 ohm driver (  5 ohm load, 15dB attenuation): R1=4.1 (160W) ; R2=1.1  (30W) ; C=32
 4 ohm driver (2.5 ohm load, 18dB attenuation): R1=2.2 (350W) ; R2=0.36 (40W) ; C=64

As you can see resistors rating go up like crazy...

Alternatively you can use an autoformer (like the ones found in cheap in-wall volume controls) to simply turn the 5 ohm load into a 20 ohm one and use the original passive network.
By the way, Truextent diaphragms also come in 16 ohm, and that is probably a better choice than 8 ohm in your situation.

[srm51555]

Hello Scott,

Assuming the same impedance and SPL/W curves as the D2430K, here are equivalent networks that should result in same high-pass frequency and overall sensitivity (ie noise) :

32 ohm driver ( 20 ohm load,  9dB attenuation): R1=13  (30W)  ; R2=11   (10W) ; C=8
16 ohm driver ( 10 ohm load, 12dB attenuation): R1=7.5 (75W)  ; R2=3.3  (20W) ; C=16
 8 ohm driver (  5 ohm load, 15dB attenuation): R1=4.1 (160W) ; R2=1.1  (30W) ; C=32
 4 ohm driver (2.5 ohm load, 18dB attenuation): R1=2.2 (350W) ; R2=0.36 (40W) ; C=64

As you can see resistors rating go up like crazy...

Alternatively you can use an autoformer (like the ones found in cheap in-wall volume controls) to simply turn the 5 ohm load into a 20 ohm one and use the original passive network.
By the way, Truextent diaphragms also come in 16 ohm, and that is probably a better choice than 8 ohm in your situation.

Thanks Thomas! Those values do rise significantly. For the autoformer would I be choosing the tap to create the 20 ohm load with 9db of attenuation and then hooking up the 2450 on the other side of the windings or would it be installed someway different?

Thanks,
Scott

[pos]

You will need to put the autoformer between the driver and (unmodified) passive network.
Set it to -3dB to accomodate a 16 ohm driver, -6dB for a 8 ohm driver, and -9dB for a 4 ohm one.

[Flodstroem]

Hi POS,

If Vb=130 Lit, Fb=27Hz, with TWO vents Dia=76mm, then Lv=198mm, owing to BB6.

regards
ivica

Is this the original dimension of the M2 bass reflex port??? If not, where can I find it?

[dprice]

Is this the original dimension of the M" bass reflex port??? If not, where can I find it?

Not exactly. The M2 port is curved or tapered and is likely a custom JBL part. See post # 842 in this thread for a photo.

I believe POS was giving the dimensions for straight 3" port with flared ends...an "off the shelf" solution.

[srm51555]

Is this the original dimension of the M" bass reflex port??? If not, where can I find it?

Member Valentin posted some info here.

Still grateful that he took apart a $5K speaker for us.

Thanks,
Scott

[Flodstroem]

Thanks for the reply, that cleared things out. So an internal dimension of the M2 cabinet is 46 x 17" 3/4" x 11" and two ports that are 60-70 mm in diameter (smallest part) and having a length of 16 cm (6.3"). If counting with the multiplying factor from the white paper the length of a straight tube would be approx 1.2 times the 16 cm curved tube, approx 19 cm? (this is only for my own simulation with the 2216Nd and 2269H)

[Flodstroem]

Here is a couple of simulations done with 2216Nd compared with 2269H in an original dimension M2 cabinet
The weight/volume of the damping material used in the original M2 is however unknown for me so I have only used the same value for al my calculations shown in the calculation files.

If comparing the two simś I cant find any big difference only that the the 2269H show op a slightly better lower bass extension lower rms displacement including better group delay. So wheres the drawback for to use the 2269 instead of the 2216 besides the price........... ?2216Nd original M2 cab sim.pdf2269H in 0riginal M2 tuning.pdf

[bubbleboy76]

Here is a couple of simulations done with 2216Nd compared with 2269H in an original dimension M2 cabinet
The weight/volume of the damping material used in the original M2 is however unknown for me so I have only used the same value for al my calculations shown in the calculation files.

If comparing the two simś I cant find any big difference only that the the 2269H show op a slightly better lower bass extension lower rms displacement including better group delay. So wheres the drawback for to use the 2269 instead of the 2216 besides the price........... ?2216Nd original M2 cab sim.pdf2269H in 0riginal M2 tuning.pdf

What about directivity?
As I understood it, one of the key things in the design of the M2 is the matched directivity at crossover.

I do not think 2269h will sound good up to and beyond 800Hz, do you? It is not made for that purpose. In that case, why not use 2269H all the way up to 20KHZ instead?

[Flodstroem]

I do not think 2269h will sound good up to and beyond 800Hz, do you? It is not made for that purpose.

Hmmm, I was looking at the specs of the ASB7118, thats why I decided to do some simś Also Im not sure the cabinet of the M2 has some negative limitations due to frequency response on the 2269 ?

[hlaari]

2269 are good up to around 300Hz like 2245 in 4345 monitor
you can see that in the transducer info

I would never use 18" woofer up to 800Hz that would never work well
the weight of the cone are 294 grams, and 2269 is perfect driver for subwoofer



Ari

[Flodstroem]

Thanks for your inputs guys. I got your points her. Whats confusing me is that nothing of your comments can be seen in the plot, and the plots are based on the T/S parameters for the drivers. I also did a simś of the 2215H in an M2 cabinet and the same could be seen in that plot, very similar to the 2216Nd. And I know that the 2215H is good for a a frequency response well up to 800 Hz.

Probably Im going to use the 2215H until I can afford the 2216Nd, or Nd-1? Is the Nd-1 not suitable for the M2 build? I have ben aware of that the Nd-1 is not used in the DiY M2 project, is that right?

I havnt yet done a sim for the Nd-1 but maybe I should..........

[Kalle]

Thanks for your inputs guys. I got your points her. Whats confusing me is that nothing of your comments can be seen in the plot, and the plots are based on the T/S parameters for the drivers. I also did a simś of the 2215H in an M2 cabinet and the same could be seen in that plot, very similar to the 2216Nd. And I know that the 2215H is good for a a frequency response well up to 800 Hz.

Probably Im going to use the 2215H until I can afford the 2216Nd, or Nd-1? Is the Nd-1 not suitable for the M2 build? I have ben aware of that the Nd-1 is not used in the DiY M2 project, is that right?

I havnt yet done a sim for the Nd-1 but maybe I should..........

Hi,
I got a M2-clone. From what I heard the 2216nd-1 is made for passive speakers (to go deeper) wihtout DSP-power. Personally I think the 2216nd in the M2-cabinet is amazing. It goes deep and plays very dynamic/realistic. I don`t think you can compare a driver from the seventies to a ultramodern high end. A sim don`t say it all. It is just a sim. The 2216nd is well worth its pennies I don't think you will be disappointed!

Regards
Karl

[Flodstroem]

You are right about that Karl, a sim doesnt tell everything, but a lot
Especially this one from Martin King that also take advantage of the enclosures internal shape and dimensions, damping material weight and positioning, speaker positioning and porting positioning...............

Yes, my sims verify that what you say about the 2216Nd-1, it goes a little bit deeper in the lower bass area (I have post the sims for the 2216Nd-1) so You could compare both speakers.

Im not going to swap the 2216Nd for the 2215H Im only going to use the 2215 until my wallet has grown a little bit bigger

I also hve the LE14H-1, 2245H, 2235H (soon also LE14H-3) but no one seems to fit the M2 enclosure better than the 2215H
2216Nd-1 Original M2 cab sim.pdf

[johanwholst]

I have used 2215h with M2. Remember to route out a bit extra for the inner baffle hole as the diameter of the 2216nd basket is slightly smaller and 2215h would not fit if you build your cabinets after 2216nd specs

2215h is a good sounding woofer, and it sounds allright all the way up to the M2 wg crossover, but 2216nd was definately an upgrade