Axiom Home Page Forums General Discussion Home Theater Frankestein Center Channel Greatness

Some of you know of my self confessed affection for modified Axiom made Merak center channel speakers. Let me tell you why, VP shaped anti standing wave cabinet, 2 x 6.5" drivers and a choice between a horn tweeter or a 3/4" titanium (same as used in the previous incarnations of the M2, M1, M0 speakers). So, tweaker that I am, I upgraded the capacitor with Audiocap Thetas, damped the box, and replaced the twin 6.5" drivers with Axiom aluminum drivers. Now, the 6.5"s are free ranging, and the tweeter is crossed over at about 3000Hz, similar set up to the M3.

Anyway, I really like these speakers, I won't tell you how I compare the sound quality to VP100/150s, except to say, I still use the modified Meraks.

Well, some months ago, I saw an auction on ebay for a pair of silk tweeters from the Reference 3a de Capo mm, (and the fancy cross-overs which go with them)) much larger than the 3/4" titanium but I knew they were crossed over at about 3000Hz and the de Capo also uses a free range main driver, so I took a chance. I think the pair cost me $50.00 or something like that. Had the Merak box routed out, the de capo tweeter fit, upgraded the speaker terminal plate and binding posts, added a supertweeter, flat to about 40KHz.

You know, luck counts in this world. This concatenation sounds great!!

Just thought I'd share my tweaker's delight.

cool deal on your 'new' center channel. i like the fact that you experiement with audio stuff to find the combo that best suits your listening tastes.

although i am just a simple plug and go kinda guy, it all still sounds pretty good to me!!

bigjohn

Nice work, 2x6!
Are you going to replace the horn tweeter in the office center also? I thought that that center was a little bit of a "shrieker". OTOH, maybe it was the insane volume you had it playing at?

Wow, although I don't have time for this sort of stuff, I followed what you said Heck, I don't even have time to finish my basement.

ps: are you going to change all the internal wiring to monster cable

G'morning!

I think I used Cardas silver wire from the new speaker plate terminals to the x-over.

Big Merak centers (twin 6.5" drivers) came in 2 flavors, the MC634 with 3/4" tweeter and the MC6H with a great horn (7"x3.5"). The Merak which now sports the Reference 3a tweeter started out as an MC634 with the 3/4" titanium tweeter. My previously favorite Merak was the MC6H with the big horn tweeter (still love that one, not shrieky Bigwill, No!). I looked around for a replacement horn which would fit, but all I could find was more of the same, i.e., a $3.00 horn tweeter.

Bigwill, time for you to come by and visit at the new hacienda. Ready? Dust off your favorite CDs and let's audition some stuff. I can tell you this for sure, as to the T Amp, Ah! CDP and modified M55s, you may think you're prepared for what you're going to hear, but I assure you, you are in for a jaw dropping surprise!

I'd love to stop by. Three day weekend coming up and I have absolutely no plans (other than hangin' at the house with a stein full of beer ).
Send me a PM or an email or something.

PM on its way! Oooh! Are you in for a surprise!

Yeooow! You did it, didn't you? You built MY Speaker!!!

You did it the Easy way!!(Yeah, Right!!)

I've been daydreaming lately....OK..OK!, for the last few years!! About a full-range center that'll match up with the rest of my speakers.

I know someone who works in a custom woodworking shop and has access to a really fine high precission bandsaw capable of producing accurate cuts thru MDF boxes to-on a good day-within .002" consistently!(he thinks) And better than that-reassembling them back together in whatever order required!

Now all I have to do is disassemble an M3, accurately measure the internal vol; accurately measure(by displacement)the single port to get it's effective I.D. and length; Do a bit of reverse engineering to come up with the Thiele Small Parameters; extrapolate to get the appropriate Vb to get, say, an f3 of about, oh, I dunno, about 58 with TWO of those lovely 6.5s!(That'l match up with my M50s quite well) Then cut two M3s apart at just the right dimensions to give a total assembled net vol, but still stay symetrical, to get that required Vb; glue them back together and start cutting ports at an appropriate starting length; start adding baffling, and begin taking speaker output measurements, continue cutting ports(so I cut it again, and it's Still Too Short!) and adding or removing baffling while chasing numbers to come up with something that may still not sound.....

Ooooor.....

Hey Ian!...Remember that Merak speaker you built a few years back...You know..the one with the two 6.5s?.....

It would be VERY cool to have an Axiom center with dual 6.5"'s A big honking center channel.

Hey F107+5

You're welcome to come on by as well!!

I like what you say about building a custom speaker box. The Merak is well built and has the Axiom shape, but could be larger for ideal sound quality from twin 6.5"s. It also needs a great puckered pongid rectum instead of a shiney little port. Rosewood would be nice.

Speaking of rosewood, I haven't set up the Thiel CS 3.6s yet, but if I could get my hands on another Merak or maybe just have a cabinet built, I could use a couple of 6.5"s I have and the remaining Reference 3a de Capo mm tweeter/cross-over for a real custom center channel. OK, now you've got me thinking ...

spiff, you're welcome to come by as well!

Oh oh, Throwing ideas back and forth can be a dangerous thing!

In particular, your phrase "...could be larger..."got me to thinking-seriously-that if I were to buy another M50; disassemble it completely and get an accurate box vol, then have a custom cabinet built, really!! that would have the same overall shape as the VP series, have a baffle the same width as the M50s but would be approximately 30" wide due to the component orientation I (think) I have in mind. (P=Pongo Port)

P M T M P


For M60 owners, perhaps a P M M M P with the center "M" being a 5.25" with the tweet being mounted on top in its own little enclosure and a single rear firing port, built to the same Vb as the M60!

I think I currently like the front firing port ldea for the asthetic aspect, and ability to place it on top of the TV without it being effected by whatever may be behind it. (65" Mits, so a 30" wide speaker isn't too outlandish!) but don't yet know what I think I know, yet. Such as the effect of placing a port in such close proximity to the tweeters, and to the speaker baffle boundry (Although I do have a pair of speakers in the dining room system that have front firing ports that are actually touching the tweeters, and are right at the edge of the baffle. And they sound just fine) But then there's the question of time alignments....

The other problem may be even more serious....I LIKE the way my inverted M3 sounds!! I have it crossed at 60 so it's full range already, or at least as full range as an M3 can get sitting on top of an immovable TV! and, at least of great importance to me, there are no voice components getting into the sub(a pet peeve going back to HTIB days!)

One of these days I'm going to attempt to put one of my M50s in place of the center(On the floor! The TV would certainly sag!)and see how it sounds on dialog. I used the M50s in phantom mode just for fun, and found they did a pretty good job with voices, but it wasen't a very good test of strictly center sounds. I'm not sure that the M50s haven't been changed some over the last couple of years(Alan says "No")but the plot shows a significantly better presentation between 1 to 2K than what the plot for the M3 indicates. Plus, of course the bass hump is smoothed out as well.

So you have an extra set of 6.5s huh? Hummmmmmm... Say...did they come with a list of T-S parameters.......?

Fascinating!!
Rich.

I'm going to make a wild guess at the volume of an M50 at 3200 cubic inches. I dunno how many jelly beans that would be.

So I ran out to a 24 hr. wal mart and bought a couple cubic feet of jelly beans.

counted out exactly how many it would take to get 1.8519 cu. ft.(used a vacuform bag and forced them under water til I got the right displacement) Counted out exactly .5 cu ft additional, as a fudge factor.

Started filling the right M50 with jelly beans thru the lower front Pongo Port; when I could get no more in, I then sealed the front port with fiberfil(which I also picked up at walmart cause I lost my bag of Acustastuff when we moved)but fiberfil works in a pinch.

I then began filling the upper Pongo Port with jelly beans, continuing to keep an accurate count, until I reached the upper Pongo Port.

Then disaster happened!

When trying to figure out a good way to lay the speaker down from its' normal vertical orientation to a prone attitude to be able to fill the remaining internal volume, I realized, much to my horror, that while my attention was deverted away from the container that held the remainder of the jelly beans that were so meticulously counted, that the Grandkids had gotten up and....started eating....No!..Not the jelly beans!!

Minor disaster, no problem, I'll simply empty out the jelly beans already inserted and start counting again!

Major disaster!! What I had failed to notice was that while doing the calculations and filling the right speaker-while having appropriate background music somewhat heavy in bass-that, Yes, that's right, I had failed to procure a properly temperature stabilized brand of jelly beans! The heat produced from the drivers(including the tweeter!)was sufficient to fuse the beans in the immidiate vicinity of the drivers!!

The results of this mornings' misadventures?: My imaging, already rather poor simply because of poor room acoustics(which I'm slowly working on to correct) is now somewhat worse. I have a rattle near the lower mid driver(which I'm sure will correct itself with a little more bass output with accompaning additional heat generated-a real probability, as I had to raise the output to the right speaker in the receiver by 4db to cancel out the bean attenuation)

I used some of the remaining fiberfil to hold in the roach baits in the Pongo Ports since the soon to be decomposing jelly beans will certainly attract these unwanted critters, and we certainly don't want "them" in the house!

Well, no worries; I still have one more M50 I can fill at a later date! But now, it's time for breakfast...we're having un-temperature stabilized jelly beans and Canadian Bacon!

I think Ian would probably tell you the volume (in cubic inches not jelly beans) if you ask him nicely.

If you call Customer Support this probably won't be the first melted jelly bean call they have received...

In reality, using an M50 as a full range center is a fascinating one!

And no, really didn't fill one of my M50s with jelly beans!! Was just kidding, of course!!

I did have to do a similar excercize a couple years back though, when my youngest Grand daughter made a slight adjustment to the vol control; like all the way to "Max" and blew out about a two sguare inch piece of my dear old subwoofers(1946!)driver! I felt a historical obligation to re-use the ancient old cabinet to keep it in service for another 50 yrs or so.

To do so required a new driver, and to get one that worked well at the ideal acoustic suspension alignment of .707, I needed to find a quality driver that had the Thiele Small parameters that matched the requirements of a box with a net volume of 1.654 cu. ft.(liters or cu. ft. for some reason, are the usual units of measurement! Who knew?!)

A while later, during a brouse session at some of my favorite on-line electronics distributors,(while I was in the "Let's make it a bass reflex with a bigger box and a chunk of sewer pipe" mode) I found a 10' Axiom "look-alike" aluminum subwoofer driver, but didn't have the heart to plug the numbers into the calculations to see if it would work! I did buy the required 3.375 port tube though, to go with the 3.76 cu. ft. box that I still might have built by a friend who works in a custom woodworking shop. My current sub has a 3db down point of 38hz where the ported box would be 3db down at 25hz. (My M50s appear to plot 3db down at just below 60hz) These are all plot related numbers without any reguard for room gain.

My current sub gives more than just satisfying output, but without the real fear of re-igniting the neighborhood "Sub Wars"

I was looking closely at a passive AVS sub to go with my subs plate amp, but the wife thought that water tanks belong in the utility room, not next to the fireplace!
Rich,