Project M2 DIY Thread

[sebackman]

Hi Scott,

Excellent. I would be really good with some comparable measurements. I will start measuring on the “Compact Monitor” in a week or so.

Maybe I’m breaking in open doors here, but anyway.

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.

Install a single basic resistor 10W (or higher) with 30-100 ohms in series with the speaker cable from the power amp to the speaker. Just add it in series with either of the plus or minus poles on the speaker. This is to take out any unwanted measurement errors from the power amp.

Connect a basic volt meter after the resistor right across the plus an minus poles of the 2216Nd. The volt meter can be any basic volt meter as long as it can do AC. If you don’t have one it can be a real “el-cheapo” for a basic check, get it from Home Depot or similar. If it can do RMS AC measures it is better, but not really needed for this.

Then you download a sine generator (app / program) to your computer from the Internet and install. Make sure you can hear the signal in you speakers. There are many to choose from and I don’t really know the difference. I normally use an analogue calibrated tone generator… Old School… But my fellow JBL nut's over here do this all the time with their computers.

Then with your computer slowly sweep a sine wave signal (does not have to be loud at all) from say 20Hz to 50Hz. At the frequency point where you get the lowest voltage reading across the 2216Nd on the volt meter is where you have the system resonance in the cabinet.

Simple as that. No mike or other SW & HW needed.

It would be nice to see where you came out. Give the excellent quality of your work, probably spot on.

Kind regards

//RoB

[pos]

Another (less precise, +/- 1Hz) method is to use a signal generator (I use a simple iphone app called "signal gen" for this) while touching the cone and find the frequency for which the cone movement is at a minimum (and air movement from the ports maximal).

With this method I found my current M2 build was tuned to around 24 or 25Hz (the tubes are too long, I prefer to aim for a lower tuning frequency and then cut them step by step...).

[srm51555]

Thank you both. I'll be trying both methods, but probably the one POS recommended first because painting the kitchen is taking all of my time.

[SMT]

Looking for suggestions from the genius and knowledge that frequents this forum. I have been thinking of doing a 5.0/.1 system of JBL M2. The biggest hurdle is crossover/DSP $$$. Obviously a 5.0 setup would require a minimum of 10 channels,though more would be preferable for possible expansion and allowance for subwoofer(s), of low latency crossover/dsp.


I also have the challenge of wanting to route my cable box and Oppo blu-ray sound through them as well.

Any recommendations for a low expenditure way to accomplish this and minimize the DAC/ADC conversions? I would like to run my home theater as well as multi-channel music(I have written off DSD for now as it would just be to expensive, from a server through these, also have a vinyl setup as well, I suppose mini-dsp? Some Pro audio interfaces exist but i am unsure of how i would get the cable box and Oppo blu-ray routed and not suffer video/audio sync issues. Maybe a Lynx AES sound card? I dunno...

I currently us JRiver MC on an audio server. Home theater is currently an Oppo BDP-105D and a Sony STR DA5300ES and a Time Warner cable box.

Thanks in advance for any suggestions.

edit: An analog crossover would be acceptable in the interim, though I lack those skills as well.

[sebackman]

Hi SMT,

This is probably way OT…

You already have the base. The BDP105 can take SPDIF, USB and HDMI in from your external units and output both multichannel HDMI and SPDIF working as a digital switchboard. With that you don't really need a preamp. And the digital volume is pretty decent if you run 24bit.

This is all fine for digital 2 channel but as the BDP (or most other DVD’s) cannot output decoded digital 7.1 (or whatever HT format you use) you have a couple of choices to make. If you can stay in the analogue world from the DVD and accept an ADC conversion for HT use that is one route. If you want to completely avoid ADC you can either get a DVD that can output decoded HT 7.1 digital via SPDIF or AES (ie a Oppo BDP-93/103D with a Vanity card installed = decoded digital HT SPDIF out or a Meridian 621 decoder).

-Or you can introduce a HT processor that can decode the digital MUX (multichannel) SPDIF signal from the DVD and send it on as separate SPDIF channels after decoding, like a Meridian pre. That is what I do.

When it comes to DSP the BSS units can do both analogue and digital in. -And a mix of them. All cards are 4 channels and can be mixed and expanded as needed. You have in total 256 channels to play with. All base units can do 16 channels in or out (4 cards x 4 channels). You can interconnect more units via Cobranet or BluLink to get the combination you need. I use 8 channels digital in (2 cards) and 16 channels analogue out (2 cards = 8 channels and a BLUBOB = 8 channels) from a BLU800.

Hence, you can get a BSS with both digital and analogue in. Two channel digital (use 2 out of 4 channels on one digital input card) for 2 channel all digital listening direct from the DDVD (SPDIF, no pre). And add two 4 channel analogue input cards for HT use and feed analogue direct from the DVD (RCA or balanced, no pre). This gives you room only for one additional card in that chassis to add one card with 4 analogue channels out. But you can add an extra chassis (max 16 additional analogue outs from 4 cards) or one or two fixed output units (BSS BLUBOB) that hold 8 analogue outputs.

ALL the BSS’s does have a very good volume controls built in on the analogue output cards. Control them from a wall controller or your iPad.

I use a Oppo BDP83 (soon to be shifted to a BDP93 with a Vanity card to get the HD audio that normally only goes through HDMI) feed digital multichannel SPDIF to a Meridian G68 for HT decoding and from that onwards 7.1 digital SPDIF ( 4 leads) to the digital inputs in a BSS BLU800. All DSP processing is done in that unit and I have added a BLUBOB to get more analogue outputs before hitting the power amps. One BLU160 or BLU800 can do all the DSP you need for 5.0/5.1.

What I suggest you should be looking for is a used BSS BLU16, BLU80, BLU 160 or BLU800 unit and get one or several digital input cards as how you decide to go per above. The analogue setup is on par with most (ADC) DSP solutions on the market, or correctly setup may even be better. The digital solution is better.

Good luck with your design.

//RoB

[SMT]

Rob, big thank you for your detailed response and suggestions! Lots of good info. I was unaware of the Vanity cards, very interesting option.

And yes, my apologies for meandering off topic.

Shane

edit: well, that is embarrassing....*Apologies

[bubbleboy76]

I use the VanityHD in my Oppo 103.
I love it.

[johanwholst]

My temporary M2 bastard moved up to our living room today. Cabinet is a reused 140l box designed for 2225, but fits 2216 good enough for now. tuning to 30hz. horn in a provisional stay on top.
Will commence work on a proper cabinet next week, and will in the meantime work on dsp settings and try out the 2450 with truextent as an alternative to D2
Hypex DLCP does crossover duty and crown cts1200 on 2216 and day aleph J on D2.
Easy to like sound, on nice to work on a two ways compared to my four ways active horns that will rest in the basement for some time.

[honkytonkwillie]

It's really hard to see your speaker in front of that spectacular view out the window. Looks like Alaska, where I live.

[johanwholst]

Photo taken like that deliberately. They are not much to look at, but hope to build a box that would justify placement with that kind of view.

[hlaari]

Nice view

it will be nice to visit you in the summer, then you will be finish with the new M2 enclosure
I promise to take some interesting parts with me



Ari

[srm51555]

Looking good

.... try out the 2450 with truextent as an alternative to D2

I also look forward to your thoughts on this combination in comparison to the D2

[sebackman]

Hi,

Maybe POS has had the time to do some lab measurements of the D2 on the M2 waveguide. That would be interesting to see.

Regarding other drivers a modern 4" core with a 476Nd diaphragm seems to measure the best and may be the best alternative for a 2-way setup. The Be's from Truextent falls off much earlier and will need more Eq/DSP or a tweeter as in the other K2 models.

I have not tried the Mg diaphragms in the unobtainable 476Mg. Member 4313b has a pair with a pair if M2 wg's to go together I don't know if he has had a chance to messure the combo.

Kind regards

//RoB

[johanwholst]

I have previous experience with 2450be on PT f95 Hf. It is totally free of breakups up to 16k, but require quite heavy EQ to play that high. We have more or less concluded that a tweeter introduces more problems than advantages combined with the pt horn and 2450be and that flat to 16k gives my ears all the sparkle and spaciousness I desire from a Hifi setup. Could be due to many years playing with guns and chainsaws

I hope to conclude likewise with the m2 waveguide as the two way concept is so attractive to me, and the 2450 with truextent is a really sweet sounding driver.
Hope to experiment this week and will post my subjective impressions compared to D2.

Again setbackman, thank you for your extensive measuring of different driver with the m2 guide!

one last question: is the 476nd diaphragm "obtainable"? would it fit 2450/2451? you certainly mean nd and not mg? (that was three questions...)

[hlaari]

one last question: is the 476nd diaphragm "obtainable"? would it fit 2450/2451? you certainly mean nd and not mg? [/QUOTE]


I think at Rob is talking about 475Nd diaphragm

there will be interesting to measure 476Mg on M2 waveguide
I think at there would be ok to try my 1501Al-1 in 140 - 180l box tuned around 25Hz


Ari