Project M2 DIY Thread

[lesliew]

very interesting posts, thanks lesliew.

I entered those settings for the 708's & 705s into my Q-SYS dsp and there was a significant improvement in the cohesiveness between them and the M2s when compared to the PEQ's that have been floating around on the web. It appears that JBL omitted the input filters from the DCIn amps probably due to DSP resources. Maybe the reason why they locked the files so that enthusiasts couldn't compare them.

I probably should load those PEQ filters for the M2 into Q-SYS and do some A/B comparison between the FIR filters.

[rodec]

I entered those settings for the 708's & 705s into my Q-SYS dsp and there was a significant improvement in the cohesiveness between them and the M2s when compared to the PEQ's that have been floating around on the web. It appears that JBL omitted the input filters from the DCIn amps probably due to DSP resources. Maybe the reason why they locked the files so that enthusiasts couldn't compare them.

I probably should load those PEQ filters for the M2 into Q-SYS and do some A/B comparison between the FIR filters.

Then, I've entered notnyt's config and it improves for me the global response:
http://www.audioheritage.org/vbullet...l=1#post422419

Thanks again to have pointed it out, great.

And double effect, I will move to an easier user experience with Audio Architect (instead of LA), and then will be forced to upgrade the BSS microsoftware that would even make an improvment (pure speculation).

[nyt]

These are the M2 settings

[lesliew]

@pos

Question for you, I believe your rephase FIR filters for the M2 was based on actually measuring an M2, but was this an M2 connected to a DCIn amp or a BSS unit, and if DCIn amp do the findings of notnyt (possible omission of input filters in the DCIn amps) make adjustments of the FIR filters necessary.

Sorry if this sounds like a very basic question,but I do think I hear a difference switching between FIR & these PEQ's. I think the jury is still out on this as they are waiting on a JBL engineer to report on whether or not the filters are omitted or just not displayed in AA.

[sguttag]

@pos

Question for you, I believe your rephase FIR filters for the M2 was based on actually measuring an M2, but was this an M2 connected to a DCIn amp or a BSS unit, and if DCIn amp do the findings of notnyt (possible omission of input filters in the DCIn amps) make adjustments of the FIR filters necessary.

Sorry if this sounds like a very basic question,but I do think I hear a difference switching between FIR & these PEQ's. I think the jury is still out on this as they are waiting on a JBL engineer to report on whether or not the filters are omitted or just not displayed in AA.

I was under the impression that the FIR filters were based on measurement of the output of the Crown DSP with the M2 settings active in order to provide an identical transfer function. The speaker itself was not measured. The settings were further compared to a BSS unit, as documented here:

http://www.audioheritage.org/vbullet...l=1#post393277

Settings are going to vary between DSP types. For instance, the shelving filters on the QSC Q-SYS are nowhere near the same as the BSS/Crown settings to achieve the same (measured) response. The PEQs did seem to match up pretty well though.

This document, I believe, spells out the process in which the FIR filters were developed as well as conventional IIR filters can be implemented (it is in POS's signature so it is easy to find!).

https://docs.google.com/document/d/1...+++&rm=minimal

[pos]

Initial rephase settings were directly translated from Crown official M2 settings, as reported by member 4313B.
These were later adjusted to fit the actual measurement (in fact two independent measurements) of BSS units running the official M2 settings, as per sguttag's link.
I am confident that these FIR settings will accurately reproduce what the BSS unit does (if enough taps are available of course), and do so with less quantization errors (convolution vs biquads...).

Now for the Crown vs BSS transfer function, I cannot comment until I can get an accurate measurement of the output of a Crown amp with the appropriate load...

I would be interested to know what is considered the canonical correction for the M2 between the BSS and Crown, ie what unit was used during the multiple measurements, listening sessions and adjustments that took place during the M2 design process...

[Flodstroem]

Finally after some year of thinking I have started to build my M2 clones. But it will not be an exact M2 clone but more an "M2-B" where "B" stand for "big" or extended low frequency. The cabinets are a little bit larger than the originals by approx 3" (75 mm) in depth. The front dimension ar e the same. And.......... there will not be the original drivers mounted bat merely a better (I think) woofer (and CD?). I will use the 1501Al-2 as the woofer and the 2451J-SL for the WG. Because of the woofer I made a lot of simulations for to get the best enclosure dimensions and lowest bass for to avoid the use of a sub. For the moment the cabinets has just been glued and screwed together. To day I also ordered some walnut veneer because of the WAF didnt like black speakers I have newer done a veneer job but Im looking forward to it, stupid dont you think? Just now Im waiting for the ordered sanding machine that I will receive next week. I have read a lot of veneering here in many threads so Im prepared.......... I think
Hers a picture of the today project:

[sebackman]

Me too....

[Flodstroem]

Me too....

[srm51555]

Nice work both of you!!!!

[Beatelund]

Me too....

And with some paint on

[Flodstroem]

Me too....

Howe are making the M2 grilles ? I have search the whole thread by now and I have found nothing about how to make them?

[Odd]

Don't answer your question but here are more pictures of the original.

JBL M2 Grill

[Flodstroem]

Don't answer your question but here are more pictures of the original.

JBL M2 Grill

Thanks Odd, it explained a lot.
JBL do make the grill frames mostly by plastics nowadays, like the grilles to the L100T (have a pair). But very hard to copy by plywood

But Im going to try to make mine out of 4 mm plywood.

[Mr. Widget]

If the originals would fit your design, I would think it’d be cost effective to simply order them from JBL.


Widget