BillFitzmaurice.info

MCM once measured and set me response and impedance charts of one of their house branded drivers. All I had to do was email and ask...

Thanks, Brent! I sent them an email and will post again when I get a response.

Kaptain John wrote: 55-2961


55-2972

I realize that these are not the ideal drivers for the Jack, but for the price, are either of them usable? And, what will be the result if used? Lower SPL? Poor overall sound? Smoke and fire?

Like Bill said, without them providing the spl charts, we have no way of knowing how it will really perform, but the simplicity of the designs (as opposed to the folded subs or dr's) is worth the risk in my case.

And I had not noticed the price on the 2972, except for half the qms being totally off, it actually looks alot like the bp102. I'd be tempted to actually try out some in my titans but having built six of them with the bp102, I don't think even that should be used in them but only the 3012lf and nothing less. So between those two I would still stick with the 2961 as it's closer to the beta specs than it is the 2972.

But if this helps, i've used my four jack with 1740's and I'm very happy with them. However, the 1740 was closer to the beta's than these are, but still, with some eq, my jacks still kick ass considering they were $14/woofer. I was going to upgrade them to beta's once went to speaker heaven, but since I got four of the 2961's, the beta's will have to wait.

EDIT: YAY! hopefully they get back to you with the charts.

Bill Wrote "Absolutely useless, as it only has 'A' weighting. Even 'C' weighting is marginal below 50Hz."

What would be a good value priced sound meter ??

Thanks Robb

[quote="Rockboy"]Bill Wrote "Absolutely useless, as it only has 'A' weighting. Even 'C' weighting is marginal below 50Hz."

What would be a good value priced sound meter ??

Radio Shack ANALOG Their older model if you can find one used, but even the new one is a good deal. I wonder if anybody has noticed that all of the digital ones have .1 db resolution but accuracy to only 2 db. Analog ones have the same accuracy but are (IMHO) easier to interpret because you don't worry about the noise factor of the decimal digit.

-rat

Kaptain John wrote: 55-2961
Re: 7.2
Le: .989
Fs: 52Hz
Qts: 0.29
Qes: 0.324
Qms: 2.6
Vas: 55.8L
Xmax: 3.5

55-2972
Re: 7.2
Le: .56
Fs: 40
Qts: 0.45
Qes: 0.55
Qms: 2.49
Vas: 82.27L
Xmax: 5

Ok, so I never heard back from MCM when I requested the response charts for these drivers, and I think the sale ends today. So I'm going to have to decide based on what I know (which is very litte) and what I've heard from everybody (which has been helpful). Both of these have a lower Qms than the Beta10, with the 55-2972 being the lowest. Both are 100W RMS. However, the 55-2972 has a higher Xmax, as well as a poly cone with rubber surround (as opposed to the 55-2961 that has a paper cone and cloth surround). And it is less expensive - only $10! So, I am leaning towards the 55-2972. I already have a couple of S2010s that will go into my first pair of Jacks. These MCM drivers will go into my second pair, which will likely be used in addition to the first pair, or perhaps as monitors.

Any final thoughts?

Kaptain John wrote:

Kaptain John wrote: 55-2961
Re: 7.2
Le: .989
Fs: 52Hz
Qts: 0.29
Qes: 0.324
Qms: 2.6
Vas: 55.8L
Xmax: 3.5

55-2972
Re: 7.2
Le: .56
Fs: 40
Qts: 0.45
Qes: 0.55
Qms: 2.49
Vas: 82.27L
Xmax: 5

Ok, so I never heard back from MCM when I requested the response charts for these drivers, and I think the sale ends today. So I'm going to have to decide based on what I know (which is very litte) and what I've heard from everybody (which has been helpful). Both of these have a lower Qms than the Beta10, with the 55-2972 being the lowest. Both are 100W RMS. However, the 55-2972 has a higher Xmax, as well as a poly cone with rubber surround (as opposed to the 55-2961 that has a paper cone and cloth surround). And it is less expensive - only $10! So, I am leaning towards the 55-2972. I already have a couple of S2010s that will go into my first pair of Jacks. These MCM drivers will go into my second pair, which will likely be used in addition to the first pair, or perhaps as monitors.

Any final thoughts?

Remember that both of those driver will not have the required rising response and the lower Fs of the 2972 will make the driver even more unsuitable for a full range design. And I just don't see an advantage to the poly cone and rubber surround as many pro sound woofer are indeed paper and cloth. Also, the Vas is larger. So all in all, like I said above, it would be closer to the p102, which is a driver that is not at all supposed to be used in the jacks. Also, the extra xmax would be nice, but with only 100 watts and rivaling the xmax of the eminence offerings, there shouldn't be any problems due to the xmax of the 2961.

To sum it all up: if doing a full range/top, get the 2961.

Too bad I couldn't get my order on friday to run side by side comparison with the 1740's and the beta in my wedges, at least like that I could have had some real input rather than just going by the sheet

EDIT: I guess if you got some of the 2972's you could build some omnidual10" subs. It should be a nice easy project. Or even go as far as doing singles and just slicing the omni in half

So I got my order yesterday and loaded a beta8 and the mcm8 into the wedges. (as expected) beta had every advantage by a long shot. The mcm did sound nice and all, but it just seemed like it was 6db softer than the beta.

So I figured these speakers (the 10") would be very nice for just a simple box with a tweeter, so that's exactly what I'm going to with all four of them. My brother has been wanting something exactly like that, so i figured they would be perfect.

Of course now that I had the chance to A/B them, I'll try to replace the 1740's with the beta's as soon as possible (or I guess until I blow them...)

As for the mcm8, It is also going in a tiny box with two piezos and a resistor.

Seis~
Thanks for the info. I decided against the MCM 10" drivers for now. And after reading your post, glad I did. Once I get the first pair of Jacks built, I'll start looking into building the second pair.
Thanks again for your input.

Hey guys, so just for reference I ordered 4 of those 55-2961 paper cone 10'' woofers from MCM. I plan on making Jack10's and maybe a W10, once MCM gets them shipping to me (which is apparently in mid November since they are now backordered). I'll report back when I get them and measure them. Perhaps the 10'' will be a good budget Jack speaker, since the ones I'm making are going to be outdoor installation jacks, so I figured a cheap speaker is better since it'll get ruined eventually.

I guess I'll just have to keep myself occupied building my new TT until they get here.

BTW, how does one normally measure just the speaker itself in order to get a usable response plot? I mostly want to check to see if the rising response of the MCM 10'' is enough to properly go in the Jack 10. I suppose once it's built, the lack of response in the 1-2kz range will be pretty obvious though.

Just to follow up, I received an email from MCM stating that the response charts for the 55-2972 and the 55-2961 are now posted on their website in the Datasheet PDFs located on the respective product pages. Here are the links:

55-2972
http://www.mcmelectronics.com/content/P ... 5-2972.pdf

55-2961
http://www.mcmelectronics.com/content/P ... 5-2961.pdf


The sale has passed, but figured if these drivers are acceptable, it would be good to know.


For comparison, here is the s2010 chart:
http://eminence.com/pdf/basslite-s2010.pdf

And the Deltalite II 2510:
http://eminence.com/pdf/deltaliteII2510.pdf

Kaptain John wrote:Just to follow up, I received an email from MCM stating that the response charts for the 55-2972 and the 55-2961 are now posted on their website in the Datasheet PDFs located on the respective product pages.


The sale has passed, but figured if these drivers are acceptable, it would be good to know.

The MCMs don't have the required rising midrange response.

Thanks, Bill!

As they look very much like the daytons from PE and after listening to them, I was sure they were pretty flat as they sounded much more "musical" than the beta in free air. Even the slight rise in the beta8 was very apparent. And thanks for the follow up; now I know what to expect from the cab I'm going to building which is a 2x10 direct radiating cab with a tweet on top and tuned somewhat low for full range.

Got a question now that I'm actually looking at the charts, if I were planning on using a CD and the HF horn and set the crossover at 1.2khz won't that end up minimizing the difference between the s2010 and the MCM? I mean, you may have a bit of a dip right around 1 khz, but it's not much more than -3 dB compared to the s2010 since the low-pass filter increases the sensitivity of the woofer just below the 1200 Hz, right in the area where it needs it.

And on a side note, the plans state that the HF horn gives similar results to the flat piezo array. What is the dispersion like on the HF horn (or flat piezo for comparison) in closer areas, something like 10-30 feet? I know that after 30 feet melded or flat doesn't matter, but is the HF horn a 'longer throw' horn? Can I use it for audiences as close as 10-15ft?

SeisTres wrote:now I know what to expect from the cab I'm going to building which is a 2x10 direct radiating cab with a tweet on top and tuned somewhat low for full range.

Did you order the 55-2961 (paper coned) or the poly 55-2972? How low are you going to tune it? I would think 60 hz would probably be about as low as you could go. Any idea what the Jack is tuned to? That may be the best frequency to tune it to... I may end up doing something similar so keep us posted if it works well.

I noticed this weird discrepancy; on the webpage it says:
Xmax: 3.5mm
but on the datasheet:
Xmax: 7mm

Somehow, 7mm of Xmax seems a little unrealistic...