MCM 55-2421 8” driver VS everything

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ACUA
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Re: MCM 55-2421 8” driver VS everything

#31 Post by ACUA »

Trying to read between the lines:
“Too narrow to provide adequate mouth area.”

too narrow to me would mean not enough mouth area, but “adequate mouth area” sounds to me like more is needed. Honestly I do not know what any of this means.

When I sum the sd spec of two 8” drivers it equates to less than a single 12” driver. This suggests to me that if I built two horn enclosures for an 8” that the total width of the two combined would be less slightly in width than a single 12” driver’s max horn width. The most correct cab widths to me on an 8” driver for a tuba45 horn is surely to be 9”-11” widths
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Seth
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Re: MCM 55-2421 8” driver VS everything

#32 Post by Seth »

Bill Fitzmaurice wrote: Sat Jan 15, 2022 8:30 am
Seth wrote: Sat Jan 15, 2022 3:00 am Bill, would it be too much to ask? Cab width range for a MCM 8" in a T45?
Too narrow to provide adequate mouth area.
So, the minimum width for a 10" driver (13 on a 12" panel width) would be too wide for an 8" driver?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: MCM 55-2421 8” driver VS everything

#33 Post by Bill Fitzmaurice »

The throat area would be too large. Make the cab narrow enough so that the throat area is small enough and the mouth area would also be too small. If it was practical to use an eight in a pro sound sub I'd have done it.

ACUA
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Re: MCM 55-2421 8” driver VS everything

#34 Post by ACUA »

:owned:

Ok so what about dual loading surely between 13-22in
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Re: MCM 55-2421 8” driver VS everything

#35 Post by Bill Fitzmaurice »

You could dual load, but it's still not a pro-sound driver built to withstand high level transient peaks.

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Re: MCM 55-2421 8” driver VS everything

#36 Post by Seth »

ACUA wrote: Sat Jan 15, 2022 12:08 pm :owned:

Ok so what about dual loading surely between 13-22in
Dual loaded would have to be at least 17 inches wouldn't it?
Bill Fitzmaurice wrote: Sat Jan 15, 2022 12:19 pm You could dual load, but it's still not a pro-sound driver built to withstand high level transient peaks.
It sounds like a T45 could be made narrow enough as a single 8" loaded cab to have an appropriate throat area, but would require being used in multiples to have sufficient mouth area. Is that a fair interpretation?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: MCM 55-2421 8” driver VS everything

#37 Post by Seth »

Strange Kevin wrote: Fri Jan 14, 2022 10:50 pm There was mention of building reducer plates to test an MCM in a cab you already have.
That was me. I built a 16" T39 for my Dad a couple years back. Next time I visit my folks, I'll pick it up and give it a whirl. While I'm at it, I may as well test and get a response chart for every driver I have that I can make fit in the cab. MCM 8, BP102, Delta 12LFA, S2012, 3012LF...
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: MCM 55-2421 8” driver VS everything

#38 Post by Seth »

I've spent the better part of the day working this all out and I must be missing something or not doing something right. I'm coming up with results that are a little tough to swallow. But I'm too burned out to search anymore tonight. Blah!

I took some rough, but fairly accurate measurements of the T45 Sketchup, divided it into 3 segments, and entered the path heights into a spreadsheet which multiplied them by various widths then converted them into the units asked for in Hornresp. I feel like I did everything right, but also feel like I'm missing something. Last time I tinkered with Hornresp, I vaguely recall needing to enter things in a specific way to account for there not being a throat chamber in the designes. But, I couldn't find what I'd read before. If any of you see a mistake, I'd be much obliged if you'd point it out.

Anyway, here's the results from what I was able to figure out. Looks good, but doesn't look altogether right.


18" vs 9" MCM loaded T45
MCM T45 9 vs 18.png

9" MCM vs 24" LAB12 T45
9MCM vs 24LAB.png

18" MCM vs 24" LAB12 T45
24LAB vs 18MCM.png

Data entry for 9" MCM Loaded T45
T45 9 MCM.png

Data entry for 18" MCM T45
T45 18 MCM.png

Data entry for 24" LAB12 loaded T45
T45 24 LAB12.png
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Seth
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Re: MCM 55-2421 8” driver VS everything

#39 Post by Seth »

Just out of curiosity, I went ahead and made this comparison.
24 MCM vs 24 LAB12.png
Can't be accurate, can it?

Might be worth tossing the MCM in one of your existing cabs 'n just see what happens.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: MCM 55-2421 8” driver VS everything

#40 Post by ACUA »

I am holding off until I am more sure of what width I need to go for my build.

I know that it is annoying when we try to manipulate Bill’s designs into something they were never meant to be. I understand that there are compromises in all things and we are likely to spend a bunch of energy uselessly.

I have seen a pair of auto tubas used out side but wall loaded do very well playing for a small crowd at a block party, not the proper use but was highly effective. I have used a home theater bass reflex 12” sub at a small dance for -40-60 people and no one know that something was wrong. I have had my pro audio rig set up in my home many times, not the intended use and I was able to get satisfying results. This is not any attempt to bastardize the designs or hard work that has gotten all of this this far.

Seth that peak we see at 40hz looks like what would happen if the driver could generate a mile of excursion. being that the response of the 9” wide cab for the MCM driver resembles the 24” wide lab12 loaded cab I bet that if you were to widen the lab12 loaded cab to like 50” that the 40hz peak would manifest in a similar way to the 18-24” wide MCM loaded graph. I would imagine a model of a 16” wide double loaded MCM configuration would graph the same but more spl.

Seth, I appreciate your efforts on this little adventure
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Re: MCM 55-2421 8” driver VS everything

#41 Post by Seth »

Image
ACUA wrote: Sun Jan 16, 2022 10:01 am Seth that peak we see at 40hz looks like what would happen if the driver could generate a mile of excursion.


It does look that way, but in reality it's a resonant frequency and there's very little excursion. All the peaks in the response graph are mirrored by dips in the displacement graph.
24 MCM displacement.png
24 MCM displacement.png (11.35 KiB) Viewed 1194 times


being that the response of the 9” wide cab for the MCM driver resembles the 24” wide lab12 loaded cab I bet that if you were to widen the lab12 loaded cab to like 50” that the 40hz peak would manifest in a similar way to the 18-24” wide MCM loaded graph.


Looks like you're right.
50 lab vs 24 lab.png

I would imagine a model of a 16” wide double loaded MCM configuration would graph the same but more spl.
9 MCM vs 17 2x MCM.png
Very similar. But like Bill's always said, the response seems to be smoothed a little on the 2x.



And, just because, here's one double driver 17" vs two 9" single driver
2x 9 MCM vs 17 2x MCM.png
Identical


Seth, I appreciate your efforts on this little adventure
I've been craving an adventure lately. :thumbsup:
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

ACUA
Posts: 552
Joined: Sun Sep 25, 2016 6:21 pm
Location: Tucson Arizona

Re: MCM 55-2421 8” driver VS everything

#42 Post by ACUA »

At the moment I am leaning toward a dual loaded 18” wide cab. That will be smaller, lighter and easier to handle for giging than my 24” wide lab12 loaded cabs. I can series wire the two drivers and will be able to feed the same 50v power as my Lab12 cabs, theoretically!!! The total cost of drivers for an 18” wide cab is $80.00 and my money is that this will beat a BP102 10”.

I again appreciate the content you have supplied. Seeing the data in the graphs is awesome.
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Re: MCM 55-2421 8” driver VS everything

#43 Post by Seth »

As far as width goes, it seems three inches more than the driver diameter/s is about the slimmest you can go without getting fancy with a beveled or stepped access cover and having to have everything 100% spot on accurate. One inch for the two sides, another inch for the access door flanges, and a half inch on each side of the driver for wiggle room/room for error (another inch). Might want to add another half inch for between the drivers of a dual loaded cab. That realistically puts you at 19-19½" for a dual loaded cab. An improvement in size for ease of handling, but doesn't seem like much compared to having 2 11" single loaded cabs.

Here's two 11" MCM cabs wired in series vs one 24" LAB12 cab, both at 50 volts
2x 11 MCM vs 24 LAB12.png



Again, I'm a fumbling n00b at using Hornresp and can't vouch for the overall accuracy of the charts I'm putting up. But, I think it's good enough to at least be able to visualize the effects of changes and identify trends.

ACUA wrote: Sun Jan 16, 2022 6:05 pm...my money is that this will beat a BP102 10”.
Here's the BP102 (in bold) vs MCM in a 13" cab.
13 BP102 vs 13 MCM.png
Looks like you may be right.

Also, on the Newark page I found that they rate the xMax as "8mm (one way)" for the MCM driver, where the data sheet just says 16mm. Happy to have cleared that up. But, it also brought up another discrepancy. The Data sheet states Fs as 29.1Hz, yet the driver data on Newark states Fs of 25.7Hz. So, who knows?

Really, I'm enjoying this as much as you are. Although, your thanks are certainly not unwelcome. :thumbsup:
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

ACUA
Posts: 552
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Location: Tucson Arizona

Re: MCM 55-2421 8” driver VS everything

#44 Post by ACUA »

I have settled on the narrowest I can manage two of the 8” drivers for my cab width. My plan is to build four total if this works well enough. The over all width is 18.5”. I have made some saw dust and divided up my sheet of plywood. it looks like I have enough material using up a few of my scraps left over from the Table tuba. At this width I will be able to get by with a single brace configuration. My 24” wide tuba 45 cabs took 3 sheets of plywood to build and this narrower configuration only takes two.

If I buy 8 MCM55-2421 drivers from Newark I get free shipping for a total of $240.00. The price of one Lab12.
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Re: MCM 55-2421 8” driver VS everything

#45 Post by ACUA »

Making more progress on the MCM55-2421 tuba45 build.

All the clamps!!!! :hyper:

With dual driver configuration I will have a brace between the drivers. After the glue dries for the supports I will router away the material so that the brace will fit. Since needing an additional driverack purchase of more drivers for this project is on hold.
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