Realistic Mach 2 mods

[Copa1934]

For confirmation...

Could somebody please repost it - I could not open earlier posted immage ...
I'd like to buy parts before opening box again PS. I found a link with very small immage - not legible though.- Thanks!

I'm attaching images of my xovers to compare to the posted diagram, which is likely correct. A couple of the coils I could not make out the values, do hopefully the diagram is based on coils that could be read.

Question. It appears, to me, that C2/4 could be combined, ie (1) 9.4uF? However, finding such a value turns up nada. Just thinking out loud.

Also, I got different readings on the respective fuses, does that make sense? If not maybe one is bad?

 

[RickeyM]

Look what ya'll made me do.

I stopped by a local source for used electronics today and spotted these

I really, really dont need any more speakers but the price wasn't bad and I just happen to have a NOS pair of RS 15" woofers (1301A) that I can drop right in. With all the posts about Realistic Mach's, I couldn't pass 'em up.
Guess who's gonna have a Spring sale on speakers I don't need ity:

The woofers I have aren't a direct replacement but they were free so it won't cost me anything to find out if they'll work. If they work out, more cash for other mods

These are going to get modded so I'll be re-reading these posts to glean all the info I can. That said, I wonder if enlarging the cabs ala member rntlee's Mach One mod would benefit the Mach Two? Any thoughts out there on this?

 

[Copa1934]

I stopped by a local source for used electronics today and spotted these

I really, really dont need any more speakers but the price wasn't bad and I just happen to have a NOS pair of RS 15" woofers (1301A) that I can drop right in. With all the posts about Realistic Mach's, I couldn't pass 'em up.
Guess who's gonna have a Spring sale on speakers I don't need ity:

The woofers I have aren't a direct replacement but they were free so it won't cost me anything to find out if they'll work. If they work out, more cash for other mods

These are going to get modded so I'll be re-reading these posts to glean all the info I can. That said, I wonder if enlarging the cabs ala member rntlee's Mach One mod would benefit the Mach Two? Any thoughts out there on this?

Keep in mind the Mach One's were air suspension and not ported. Air Suspension systems often require larger cabinets for like drivers. The Mach Two woofer measures fairly close to the Mach One though the suspension is slightly different, designed for bass reflex (ported) designs.

I'd test drive first before moving on. I believe in this post some have gone with smaller ports and others have plugged the port entirely. Still others added more filling. Don't forget to clean the pots, they likely need them.

Nice find by the way!

 

[RickeyM]

Comparing the specs I've found here, the Realistic 1301A might be better for ported than the original. The Qts is lower 0.58 vs 0.974 for the Mach Two woofer, Qes of 0.71 vs 1.254 for the Two, but the proof will be in the testing. I just have to dig those 1301A's out of storage. Later guys, I've gotta go check out the foam on these mids.

 

[Copa1934]

Comparing the specs I've found here, the Realistic 1301A might be better for ported than the original. The Qts is lower 0.58 vs 0.974 for the Mach Two woofer, Qes of 0.71 vs 1.254 for the Two, but the proof will be in the testing. I just have to dig those 1301A's out of storage. Later guys, I've gotta go check out the foam on these mids.

Ah the mids. I refoamed one of mine, left the other alone for the moment. Not a pleasant experience as the replacement barely fit.

 

[RickeyM]

Inside the Mach Two

This is what passes for damping material inside the mid cup.

This has definately gotta go. Either some wool or polyfil. Here's the crossover hiding up in there. At least it's too big to fit on the back of a terminal cup.

As I look at the material & construction of these cabinets, I wonder if instead of tryin' to fix 'em, would it be better to just build new ones? Larger volume, well braced cabs instead fo trying to re-engineer the old ones. Mirror image them as well. :scratch2::yes:
As they say MDF is cheap.

 

[Copa1934]

This is what passes for damping material inside the mid cup.

This has definately gotta go. Either some wool or polyfil. Here's the crossover hiding up in there. At least it's too big to fit on the back of a terminal cup.

As I look at the material & construction of these cabinets, I wonder if instead of tryin' to fix 'em, would it be better to just build new ones? Larger volume, well braced cabs instead fo trying to re-engineer the old ones. Mirror image them as well. :scratch2::yes:
As they say MDF is cheap.

Honestly I don't recall anyone complaining about the use of damping material. The only issue with the mid is the density may actually consume "physical" volume, but if the volume was calculated with this in mind you could seriously alter the mid performance. If someone can grab T/S params from the mid that would be very cool.

There was a post about fiberglass vs poly and the final results put fiberglass ahead. They do not have the same characteristics, which was clearly documented in the thread, here on AK.

You'll likely want to plug in the T/S params, I believe published in this thread, to get some idea of the working volume. I know it was larger, like 9cuft! Not sure I'd aim for that large a cabinet. If you do it, sure would make for an interesting post. The drivers are pretty decent and the tweeter is quite well regarded.

Note: The ring the xover is mounted on is the cutout from the woofer opening. Not many people catch that.

 

[RickeyM]

Honestly I don't recall anyone complaining about the use of damping material. The only issue with the mid is the density may actually consume "physical" volume, but if the volume was calculated with this in mind you could seriously alter the mid performance. If someone can grab T/S params from the mid that would be very cool.

Not to be un-scientific, but I would just change the stuffing in one and compare it to the other one left stock Maybe I'll just keep an eye out for a pair of those Realistic dome mids :scratch2:

Enclosure size and porportion wize, that enlarged Mach One cab just looks plain mean. But then again, that big mid horn up there probably has something to do with it. I think it would be a case of build the bigger cabs, play around with adjustable ports and see what works.

 

[Copa1934]

Not to be un-scientific, but I would just change the stuffing in one and compare it to the other one left stock Maybe I'll just keep an eye out for a pair of those Realistic dome mids :scratch2:

Enclosure size and porportion wize, that enlarged Mach One cab just looks plain mean. But then again, that big mid horn up there probably has something to do with it. I think it would be a case of build the bigger cabs, play around with adjustable ports and see what works.

Can't wait to hear more on your project.

Got my caps ordered, hoping they arrive before the coming weekend.

 

[Copa1934]

Not to be un-scientific, but I would just change the stuffing in one and compare it to the other one left stock Maybe I'll just keep an eye out for a pair of those Realistic dome mids :scratch2:

Enclosure size and porportion wize, that enlarged Mach One cab just looks plain mean. But then again, that big mid horn up there probably has something to do with it. I think it would be a case of build the bigger cabs, play around with adjustable ports and see what works.

By the way, I'd think hard about that dome mid. You could run into power handling issues with it diving to low. RS has the specs on their web site and the power handling drops off significantly as the frequency drops (xover point that is). Info here...
http://support.radioshack.com/support_audio/doc14/14234.htm

 

[RickeyM]

What's the power handling of the stock mid?

A thought just struck me. I don't recall evr seeing a pic of Mach Two's with the grills on. Do the original grills just fall apart or does everybody with "Two's" like to show 'em off?

 

[Big Tuna]

This is what passes for damping material inside the mid cup.

This has definately gotta go. Either some wool or polyfil. Here's the crossover hiding up in there. At least it's too big to fit on the back of a terminal cup.

As I look at the material & construction of these cabinets, I wonder if instead of tryin' to fix 'em, would it be better to just build new ones? Larger volume, well braced cabs instead fo trying to re-engineer the old ones. Mirror image them as well. :scratch2::yes:
As they say MDF is cheap.

There are different types of MDF and not all of it is cheap. There's a reason mfr's use it instead of plywood. It has much better damping characteristics and it absorbs transients with less vibrations than plywood.

 

[Big Tuna]

What's the power handling of the stock mid?

A thought just struck me. I don't recall evr seeing a pic of Mach Two's with the grills on. Do the original grills just fall apart or does everybody with "Two's" like to show 'em off?

Yeah, we like to show them off and no they don't fall apart, they are solid frames with cloth. The ones that fall apart are the speakers that utilize the open cell foams, like Marantz first gen HD's, Imperials, XXM series, Superscope S series, JBL L-100's and a few others.

 

[RickeyM]

There are different types of MDF and not all of it is cheap. There's a reason mfr's use it instead of plywood. It has much better damping characteristics and it absorbs transients with less vibrations than plywood.

Unfortunately, the Mach Two cabs are made from partical board. The stuff is lighter and less dense than MDF. It breaks more easily and is even more succeptable to water damage than MDF. The only reason to use the stuff is to cut costs. Nobody trying to make an even halfway decent enclosure would use it.

Even tho' it's not the original finish, I've been eyeing some nice Cherry veneer if I go ahead with the bigger boxes :thmbsp:

 

[Copa1934]

Unfortunately, the Mach Two cabs are made from partical board. The stuff is lighter and less dense than MDF. It breaks more easily and is even more succeptable to water damage than MDF. The only reason to use the stuff is to cut costs. Nobody trying to make an even halfway decent enclosure would use it.

Even tho' it's not the original finish, I've been eyeing some nice Cherry veneer if I go ahead with the bigger boxes :thmbsp:

Particle board? Not sure I'd qualify this as particle board, has too smooth a finish (on the inside) to be particle board. Mach Two's, like their earlier brethren, were made with real wood veneer. If in good condition it would be a shame to not re-use the cabinets and simply reinforce them. I have JBL's and they look more like particle board than the Mach's do, though I can't honestly say I've seen the inside of JBL's from the same era as the Mach Two's. MDF isn't all the same, there are different grades. Besides, what wood supplier would put high quality veneer on cheap particle board? That would be cutting corners to the extreme. I realize it's not great, but it's certainly not bad, compared to a lot of other brands that sell for more money.

 

[jjtucker2]

OH boy, a Mach thread...........

I will be watching to see if there are any contributions in the new cap/xover area. I like mine, but I agree that the mids kind of suck compared to the rest of the package, but still better than the 1's (sorry Copa). I have not refoamed them yet, but everything else has been replaced. I was going to try to stuff the polyfill into the ports, but once I moved them to the CR-2040, it seems the boominess subsided quite a bit. I was running them on an STA-2300 and they sounded great, but not as nice as the Mach 3's for the small room they were in. Much better in the larger room on the Yamaha which seems to control the bass much better than the 2300. I might try to stuff the 3's with polyfill and see if that helps. Both speakers share the same cabinet and woofer and boom.

I, too, wonder what these would sound like in a bigger cabinet. Anyone have any dimensions in mind?

It is awesome to see an interest in this line of speakers. I think these were the best the Shack (had) made.

 

[Big Tuna]

Unfortunately, the Mach Two cabs are made from partical board. The stuff is lighter and less dense than MDF. It breaks more easily and is even more succeptable to water damage than MDF. The only reason to use the stuff is to cut costs. Nobody trying to make an even halfway decent enclosure would use it.

Even tho' it's not the original finish, I've been eyeing some nice Cherry veneer if I go ahead with the bigger boxes :thmbsp:

Particleboard and MDF is the same thing, wood particles/fibers, chopped, formed and pressed together, hence MDF, Medium Density Fiberboard, LDF Low density Fiberboard, and HDF, High Density Fiberboard. Almost all speaker mfr's from the lowliest of low cheapies to the most exquisite expensive monsters, still utilize a particular grade of MDF because it has the best neutrailty for resonant frequencies and the best damping characteristics. It's just a coincidence that it's cheaper to use than Plywood. I have seen $20,000 JBL Speakers that were made with MDF Fiberboard, and then they were laminated with a type of lexan, then powdercoated to look like a Beautiful black Piano.

 

[bryblob]

I bypassed the fuse bulbs in mine and cut down the port. I probably shouldn't have done it, but I was giving these to a friend and wanted to try it as was suggested earlier in this thread. I honestly couldn't tell much of a difference with cutting down the port, but I thought I heard better clarity with the fuses bypassed.

 

[Copa1934]

I bypassed the fuse bulbs in mine and cut down the port. I probably shouldn't have done it, but I was giving these to a friend and wanted to try it as was suggested earlier in this thread. I honestly couldn't tell much of a difference with cutting down the port, but I thought I heard better clarity with the fuses bypassed.

As I understand it the bulbs work like varisters, though I don't understand the technical speak of it. Supposed to reduce the signal getting to the driver as more power is fed and I believe at the same time reduces the output. Many people have commented that bypassing does boost high end, though many will also remind people that doing so also removes some protection for the tweeter. Fair trade if you don't push them too hard too often. I guess.

 

[Copa1934]

Particleboard and MDF is the same thing, wood particles/fibers, chopped, formed and pressed together, hence MDF, Medium Density Fiberboard, LDF Low density Fiberboard, and HDF, High Density Fiberboard. Almost all speaker mfr's from the lowliest of low cheapies to the most exquisite expensive monsters, still utilize a particular grade of MDF because it has the best neutrailty for resonant frequencies and the best damping characteristics. It's just a coincidence that it's cheaper to use than Plywood. I have seen $20,000 JBL Speakers that were made with MDF Fiberboard, and then they were laminated with a type of lexan, then powdercoated to look like a Beautiful black Piano.

If you check with several online wood related posts Particleboard and MDF aren't quite the same thing. There are different qualities in joining, cutting and holding strength. I personally still build from plywood. I can read all the hype on the planet about PB and MDF but have yet to see any manufacturer build the same speakers from the respective products, put them in a blind test and see who, if anyone, can "hear" the difference. Till I read such a conclusive report I'll keep using plywood. Oh, I do, from time to time make exceptions and use PB, but rarely.

Having an "inner" core for the JBL's you mention makes perfect sense because of the resonant qualities of Lexan, not a good thing. There are viable exceptions to everything.