MCM 55-2421 8” driver VS everything

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

#16 Post by Seth » Thu Jan 13, 2022 12:33 am

AntonZ wrote:
Wed Jan 12, 2022 12:03 pm
Seth wrote:
Tue Jan 11, 2022 8:26 pm
I've got to imagine the biggest reason the option isn't talked about much has something to do with the "public image" of the designs. It's hard enough to get the average Joe to believe the "hype" while promoting the use of well known and trusted drivers, let alone trying to sell the validity a $35 off brand eight inch driver loaded cab to a serious gigging professional.
Bill has designed his PA tops with piezo drivers, which are widely frowned upon yet they perform well. I am pretty sure from that point of view he would not hesitate to use the cheaper drivers for PA subs if they were a viable option. I think they are OK for home use with occasional peaks, but a PA that has them running balls to the wall with hard voltage limiting makes for more thermal and mechanical stress on the drivers. They would not be reliable enough for pro sound use. That is just my uneducated guess though.
That's a good point Anton, about the piezo's :thumbsup:

After the beating I've given my MCM's, I'm inclined to doubt they'd fail in pro sound use. But really, there's only one way to find out. Question is, is finding out worth it? Or, is it more of a fun thought than a realistic quest?
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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AntonZ
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Re: MCM 55-2421 8” driver VS everything

#17 Post by AntonZ » Thu Jan 13, 2022 5:13 am

I have a few spares of the Tangband 8 (same reason as ACUA - I thought I might blow one but never actually did) as well as two 3012LF. The 3012s where intended for a pair of T39. That has been the intention for several years now. Time got in the way, or lack of time to put it more precisely. I do like the idea of building a T39 for 3012LF, then install the TB with a 12"-8" reductor plate. Don't know if a Tangband 8 would work at all in a T39 sized for a 3012LF though. The TB drivers work fine in T18, AT and TT but those are not pro sound subs.

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Re: MCM 55-2421 8” driver VS everything

#18 Post by ACUA » Thu Jan 13, 2022 9:20 am

My first thought is that since I already possess tuba45 subs than if I build some narrow ones I can still couple them together should I need to or want to. In hind sight, after mobile DJing for a few years now, baring the proclaimed pandemic, I would rather have the titan48 subs. The additional 3in of size is hardly anything, the loss of 5hz from 30hz to 35hz is only effected by a few songs and the effort it takes to get those frequencies excited does not justify the headache of dealing with noise ordinances that never fail to take effect. I also really like the Vplate concept. When I started out here trying to get into the pro world I was coming from the stereotypical car audio world where the absolute lowest frequencies were the most coveted. I have always enjoyed 12-28hz sound waves that take your breath away. As I age my desire for hifi is winning out and the tactility of the titan subs makes more and more sense.

It would be cool to put in service a ton of MCM 8” loaded titan48 cabs with a plexiglass baffle window to see those little guys do work.

I am likely to build a tuba45 for experiential sake. If it goes well I am considering building more then I will have options for gigs. I actually really like the idea of having some light narrow subs as well as my large one. I have done events where I did not even use a subwoofer and in that spirit having 4-8 mini tuba45s starts to make sense, especially if I can seamlessly couple them to my existing set. I envision having to be careful about my wiring configurations but that is half the headache, I mean fun. :fruit: I happen to have picked up last year an additional sub amplifier so I already have certain of the infrastructure for this endeavor. Perhaps for insurance I should see about including and adapter mechanism to accommodate a 10” driver should the MCM driver not yield. Then I could always spring for the BP102 driver and continue with my plans.

Well it is settled, I shall start laying the ground work. I now have to settle in on the optimum cab width. Between 13-16” for sure, this is pumping me up.
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Re: MCM 55-2421 8” driver VS everything

#19 Post by Seth » Thu Jan 13, 2022 2:05 pm

I've come from the same low frequency mindset, car audio background too. I initially wanted to build T48's, but ended up building T39's instead. I don't recall what exactly persuaded me to take that route, but I do recall Bruce, Grant, and a few others had some influence in making that particular choice. I think it may have been the fact that the first one I built was only going to see live music duty and didn't need the extension. I was pleasantly surprised that it produced many of the frequencies below it's highpass setting at an acceptably audible level when using a 24dB/octave slope. There's certainly a handful of songs that had frequencies that were not reproduced at an acceptable level. But, I was actively listening for a deficit. If I was using them for DJ duty, chances are the typical party person would never know the difference on most of them and I'd potentially remove a couple from the playlist where the bottom end isn't sufficient to keep the dance energy up. Ultimately no big deal. If you ever go the route of the Titan, I would give the 39 a serious looking at if I were in your shoes, intent on improving ease transport and handling.

When I get the rest of my planned cabs assembled, I'd enjoy giving you and Radian a visit so we can have a play day and all get a firsthand experience of all the different cabs we'll have. (BTW, do you have a link for the speaker stands/lifts you use?)

If you go 15 or 16 inch on the trial T45 cab, you'd be able to utilize an 8, 10, or 12 inch driver. No matter what you build, if you build 2, I'll donate my spare 8 to the cause and send it to you after I put it in the T39 for a test and data session. That way we/you would be able to compare the performance of two 8's against one 12.

Some numbers to chew on... the spec sheet for the MCM lists a "piston diameter" instead of Sd. Easy enough to convert 163mm diameter to an Sd of 209cm². They also list the xMax to be 16mm. I have a hard time believing that. I think they are either listing the full travel instead of one way excursion, they're listing xLim as xMax, or they're just calculating xMax in a way that's inflammatory. But, who knows, maybe 16mm is accurate? In any case, if it is accurate, that equates to a Vd of 334cc. The LAB12 is 659cc Vd (13mm xMax, 506.7cm² Sd), so 2 MCM's should equal one LAB12 in output potential... IF the xMax rating on the MCM driver is relatively accurate.

Another little detail just popped in my mind... With the added impedance of the cab, it might be possible to run eight 8's (series/parallel) on a single 4ohm rated amplifier channel, or 16 cabs on a 2 channel amp. That's kind of interesting to me.
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

#20 Post by AntonZ » Thu Jan 13, 2022 5:03 pm

You already have a T39 available Seth? You could easily make an 8"-12" circular adapter plate out of some spare ply and be the first to thump a T39 with an 8" driver. If you can, run it somewhat hard (with proper brick wall limiting, of course) and tell us how it works out.

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Re: MCM 55-2421 8” driver VS everything

#21 Post by ACUA » Thu Jan 13, 2022 5:11 pm

I built the stands myself. The one picture shows me flying both stacks in front of my house the other picture is the middle part of the stand. I built it out of L- channel and flat stock all 1/8in thick. The legs and neck insert and pin into the middle part. The winch mechanism is not as robust as it may aught to be so I put a loop in the cable so that once the speakers are at full lift I hook the loop to an arm I built onto the stand so that I can unload the winch while in use. The cable and winch are rated for 1200lb and my array is under 250lb. The top of the stand is 12ft. It’s some work but flying the rig is awesome. The rear leg and neck is 2x6 and the front legs are 2x4. Not sure what gauge but the wall thickness is roughly 1/16in. I have hung and or swing from the top trying the integrity. The legs span 7 ft wide and the rear leg is 8 ft from the front two legs. The center is plumb bob verified ti be just rear of center the triangle by 3 inches. The front legs have some adjustment about 3in for leveling.

I will build one cab to start if it goes well we can discuss what comes next. I would value a meet up someday, bring it on.
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Re: MCM 55-2421 8” driver VS everything

#22 Post by Seth » Thu Jan 13, 2022 5:49 pm

AntonZ wrote:
Thu Jan 13, 2022 5:03 pm
You already have a T39 available Seth? You could easily make an 8"-12" circular adapter plate out of some spare ply and be the first to thump a T39 with an 8" driver. If you can, run it somewhat hard (with proper brick wall limiting, of course) and tell us how it works out.
Yeah, that's what I was thinking. Seems too easy not to give it a go.
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

#23 Post by Seth » Thu Jan 13, 2022 6:18 pm

ACUA wrote:
Thu Jan 13, 2022 5:11 pm
I built the stands myself.
They are awesome. Looking at it, it looks like the legs could be made to fold down and the top fold back (if the winch wasn't there) for transport without disassembly. Something like that in aluminum would be sweet. I completely dig your design :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

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Re: MCM 55-2421 8” driver VS everything

#24 Post by ACUA » Thu Jan 13, 2022 10:10 pm

I cut the two sides out and laid out the one side. I shall dado this one but not the other side.
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Re: MCM 55-2421 8” driver VS everything

#25 Post by Seth » Fri Jan 14, 2022 12:44 pm

DANG! You're not fool'n around! No time like the present, I guess. Way to keep the momentum rolling. At this rate we (you) should have some results for us in a week or two! Nice :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

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Re: MCM 55-2421 8” driver VS everything

#26 Post by ACUA » Fri Jan 14, 2022 8:58 pm

A week, no, a few weeks yeah sure I will have one build to fit the little 8” driver that could.

Headed to the lumber yard for a sheet of 5ply. I dado routed the base side today. Pretty straight forward.

When comparing the tuba45 to the table tuba, the horn of the table tuba starts out at like 3/4-1” where the tuba 45 starts at 1.25” to me this would mean that there aught to be more cone pressure potential on the table tuba than the tuba45.
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Re: MCM 55-2421 8” driver VS everything

#27 Post by Strange Kevin » Fri Jan 14, 2022 10:50 pm

Hey ACUA,
Wanna say I fully support your experiment here!
Good Luck!

There was mention of building reducer plates to test an MCM in a cab your already have.
I did just that for my TTLS, I got lucky and found a deal on a NOS Eminence HL10c, so of course I'm gonna use it!
But still wanted to test a spare MCM driver to compare.
so I took 5 minutes and threw one together.
Here's some pictures,

Obviously, You can take 5 more minutes and put together something much more presentable, but I wasn't too concerned with how it looked at the time...
Front side. 10" to 8" adapter plate.
Front side. 10" to 8" adapter plate.
Back, 10" to 8" adapter
Back, 10" to 8" adapter
In the unlikely event you're not satisfied with 8" drivers in your new T45s, you may consider cutting the baffles for a 10" driver and using a similar reducer to keep the option open for a BP102 or something else in the future.
Just my 2 cents.

Good luck man!
I'm keeping an eye on this one!
Authorized Builder - Phoenix AZ.
Main Rig - 6 DR200s - 6 T48s (30")
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Re: MCM 55-2421 8” driver VS everything

#28 Post by ACUA » Fri Jan 14, 2022 11:44 pm

First of all, last month when I bought plywood the prices were back to normal. I spent $28 a sheet for rough grade 1/2in 5ply. Today I had to spend $48 for the same grade plywood. Darn, first world problems. Anyway I got a sheet so I can make with the sawdust.

Still trying to work out the optimum cab width. The sd specs
12” - 78sqin
10” - 53sqin roughly 65% the area of the 12”
8” - 32sqin roughly 62% the area of the 10”

Tuba45 cab width ranges
12” - 15”min and 24”max
10” - 13”min and 18”max, min is 86% the 12” spec and max is 75% the 12” spec.

linearly, the cabinet widths for an 8” driver would then be:
8” - 11.25”min and 13.5”max
I also observe that the min of the 12” driver configuration is 62% the max, the min of the 10” driver config is 72.5% and based upon my calculations for what the 8” cab widths should be the min is 83% the max, increasing about 10% each time. I am certain that little to none of the math for this stuff is linear in function, but by working with the percentages maybe this is close.

To me 16” wide is too wide. My gut feeling is 14”total cabinet width for the little driver that could. I have no idea how to properly derive the proper cab width. Shooting in the dark with a trebuchet!
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Re: MCM 55-2421 8” driver VS everything

#29 Post by Seth » Sat Jan 15, 2022 3:00 am

To add some ingredients to the thought soup;
For the cabs that have 8" and 10" options, the widths are as follows
TT
- 8" -- 12 to 18
-10" -- 16 to 22
TTLS
- 8" -- 12 to 18
-10" -- 16 to 22
AT
- 8" -- 13 to18
-10" -- 14 to 19
TrT
- 8" -- 5 to 10
-10" -- 7 to 10
T18
- 8" -- 13 to 18

There's no 10" option for the T18, but I threw it in there anyway. Just another data point to consider.

Just as an observation, the AT's 10" widths (14 to 19) are closest to that of the T45's 10" widths (13 to 18). Could that possibly indicate it's 8" widths could be close too? Perhaps. Or perhaps not. Hmmm. (we need a head scratching smilie/emoji, or maybe stroking the chin)

Since these are a different design, I suppose we could/should calculate the throat area of the small end and take that into account too. Although, it really wouldn't hurt to just ask Bill if he wouldn't mind running a couple simulations and give you a ballpark width range.

Bill, would it be too much to ask? Cab width range for a MCM 8" in a T45? Oh, wait. You'd have to calculate all the areas for the different widths to run each sim, wouldn't you? Maybe it is too much to ask. No sweat if you're not in the mood.

I may be able to fumble my way through it with some rough measurements off of the Sketchups I unfolded a while back. I'll give it a shot in the morning and see what I can come up with.
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

#30 Post by Bill Fitzmaurice » 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.

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