Challenge to Mach One owners

[jamesm007]

Parts Express now sells replacement woofers made especially for the Mach One.

Thanks for that reply, and I would like to make a new more clear post.


I needed all Mach Ones owners attention :nono:

I made a post about it with no replies except the above quote. I think there is a problem with the knowledge of the 4029 woofer.

This is what evidence is starting to show. I believe Parts Express made a big mistake maybe.

My woofer from an original 4029 I bought new back in ~1983 says 6 ohms on the back, and measures 6 ohms. I am reading of some who have the same 6 ohm driver. If there are 4 ohm drivers (still has the sticker that says 4 ohms on the woofer) than RadioShack made two versions. Can anyone show a pic of a 4029 woofer with 4 ohms on it?

I was thinking well maybe Parts Express measured at the crossover freg or... something different. But its business practise to state the nominal ohms of a driver so folks know. It should have been rated 6 ohms, unless they just went by what others say on forums. Many people just may have wrong info. I notice there are not too many original Mach One 4029 owners; as I am of almost 30 years and babied them for 30 years... and was into them for a long time and am again into them (a lifetime passion :sigh.


If you look at my pick of the crossover you will see it has very different values compared to the 8 ohm version from what I read(?), and is made for the lower impedance driver of 6 ohms. Replacing it with a real 4 ohm driver will cause problems. Its hard to figure the exact crossover of the Mach Ones (4029) woofer. Its a 2nd order crossover with a 33uf cap and 1mh coil, for 4ohms this would be 800Hz but its not crossed over that low (from actually speaker measurements; test tones, spl measurements) and is crossed over in the 1-2k range, and its rated by RS at 1.2khz. Speakers have dynamic impedance so I could not figure it out without more info.

The real point is did Parts Express copy the second generation Mach One 4029 woofer right? Or did they go by forum posts saying its 4ohms?

I do believe PE had one Mach One woofer and reversed engineered it, the first generation. I am not sure if they had a 4029 woofer, even if they did and every-one's 4029 woofers say 6 ohms it should have been labeled as such. Kinda crazy to argue about speakers I have owned for almost 30 years LOL.:thmbsp:

How many have 4029 Mach Ones with 4ohms on the back of the woofer? Could you show a pic?

It would be nice to compile one post with all the facts we know of the Mach Ones.

 

[jayczar]

Have you contacted parts express?

 

[jamesm007]

Have you contacted parts express?

If they made an error they would say it works and replaces it. The difference would be about 200hz lower of a xover for the woofer.

The question is still how many have 4 ohm 4029s or 6 ohm 4029s woofer in their Mach Ones. If all have 6 ohm drivers and they mine does measure 6 ohms as well as says it. Then the 4 ohm would alter the speaker, even if its a replacement. It would be better to re-foam yours if you can.

 

[jamesm007]

If they made an error they would say it works and replaces it. The difference would be about 200hz lower of a xover for the woofer.

The question is still how many have 4 ohm 4029s or 6 ohm 4029s woofer in their Mach Ones. If all have 6 ohm drivers and they mine does measure 6 ohms as well as says it. Then the 4 ohm would alter the speaker, even if its a replacement. It would be better to re-foam yours if you can.

Just spoke with Parts Express. They said yes the 4029 uses a 6 ohm woofer but there is no cross-over to it, so it won't matter . He said it just depends on if your amp can handle it. When I said it does use a 2nd order cross-over he said "oh, its not on our data sheets". Parts Express had bad info it seems. When I told him that would alter the cross-over point he said it would not be a big deal and said its just a replacement woofer.

Now I am not out to de-grade Parts-Express and really like them as a supplier of hard to find stuff, and have bought from them many years ago. I just want to set the record straight on the Machs and end the rumor of 4 ohm drivers. Unless proven other-wise, me and Parts-Express are in agreement that the 4029 used a 6 ohm woofer. Please keep this in consideration with respect to the crossover and voicing; a huge hole could result in a very critical area ~1000hz IMO.

And unless proven other-wise lets end the rumor of 4 and 8 ohm drivers, its 6 and 8 ohm drivers. With the 6 ohm edge wound voice coils used in the revised 4029 second generation Mach One Liquid Cooled speakers.:yes:

 

[Negotiableterms]

The Parts Express site clearly states that their woofer is only a replacement for the 8-ohm part found in the later production:

"Replaces the 4024 8 ohm version (1976-1981)"
http://www.parts-express.com/pe/showdetl.cfm?partnumber=290-184&source=googleps

They note that they also make the same woofer in 4-ohm, but they do not claim that it's a replacement for anything. They don't make a replacement for the earlier 6-ohm model.

Too bad you got an unknowledgeable person on the phone.

 

[JohnVF]

The response of these speakers, when I had them, was not what I remember as being ruler flat in the first place. But the big debate will go on whether I'm a fan or not, so carry on.

 

[jamesm007]

????

The Parts Express site clearly states that their woofer is only a replacement for the 8-ohm part found in the later production:

"Replaces the 4024 8 ohm version (1976-1981)"
http://www.parts-express.com/pe/showdetl.cfm?partnumber=290-184&source=googleps

They note that they also make the same woofer in 4-ohm, but they do not claim that it's a replacement for anything. They don't make a replacement for the earlier 6-ohm model.

Too bad you got an unknowledgeable person on the phone.

You are looking at the wrong page, Parts Express makes two woofers for the Mach One. They make the proper 8 ohm version and a 4 ohm version suppose to be in latter models. Problem is they had bad info, latter Mach Ones used a 6 ohm woofer. Take a look, they do claim it replaces the 4029 woofer

"Modern reproduction of the famous Mach One design
Resurrect your Mach One speakers from the Seventies!
Same voicing but up-to-date materials and technology
2-1/4" copper voice coil on brass former
Replaces the 4029 4 ohm version (1982-1984)
Also available in an 8 ohm version
Great results in custom acoustic suspension designs, too!"

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-182

They make a number of claims. The 6ohm version was in the latter Mach Ones, he did know that. There are no 4 ohm Mach Ones, only early 8 ohms and latter (1982-1984) 6 ohm versions used in the Liquid Cooled, foam surround woofers.

Read the page for the 4 ohm version.

 

[jamesm007]

The response of these speakers, when I had them, was not what I remember as being ruler flat in the first place. But the big debate will go on whether I'm a fan or not, so carry on.

Its not about being ruler flat. Its about people spending a lot of money and building a speaker with a big hole in its sound. The Mach Ones which I have owned for decades (and know very well) did not have any holes in its response and was good enough. If you put in a 4 ohm driver instead of the proper 6 ohm driver what will that do to the 2nd order cross-over.

Look Parts-Express sells replacement woofers for the Mach Ones, that alone should say something about how popular these speakers were/are. Thats almost unheard of. Radio Shack was bigger than JBL and Advent put together and did not have to buy drivers from anyone, they could custom make thier own if need be. Although they did buy to save design costs and if the price was right.

Anyways the thing I am trying to do is make people aware of the fact there are two woofers an 8 ohm and a 6 ohm, no 4 ohms so far. Unless some persons can start showing them in thier second generation Mach Ones

 

[JohnVF]

Fair enough. I just don't think it's right to judge a company's product or design information based on one conversation with a guy who happened to answer the phone. Call up my company and ask the receptionist how many frames per second the director of photography was shooting on shot 11a last thursday. She'll hang up on you. You don't even have the woofer in hand to measure, for all you know it's labeled wrong on the website.

Anyway, I don't want to waste any more of my life on Mach Ones...wasted about 10 years with them already! I'll back out now.

 

[Reel 2 Reel]

Oh..c'mon...dont make me have to tear my machs apart to see...(like waaaaay too much work ) all i know is they work!..

 

[jamesm007]

Fair enough. I just don't think it's right to judge a company's product or design information based on one conversation with a guy who happened to answer the phone. Call up my company and ask the receptionist how many frames per second the director of photography was shooting on shot 11a last thursday. She'll hang up on you. You don't even have the woofer in hand to measure, for all you know it's labeled wrong on the website.

Anyway, I don't want to waste any more of my life on Mach Ones...wasted about 10 years with them already! I'll back out now.

I like Parts Express...

But its not your money or my money. If they are labeling it wrong that's part of the reason I called, and this may slowly move the rudder at Parts Express so they label it right. How can you even calculate a crossover for it. If a mistake was made its not fair to people to have poor sound,,, its just not.

Many folks never had them and now want them and many still enjoy them. My main speakers are not Mach Ones. But some guys/gals still rock with them. People usually perceive others as having a self interest, and a selfish one. Believe it or not my interest is in others.

 

[mashaffer]

Good detective work. If it is 2nd order LP on the woofer I would guess that a slight adjustment to the cap value should get things in the "close enough" range.

mike

 

[jamesm007]

Good detective work. If it is 2nd order LP on the woofer I would guess that a slight adjustment to the cap value should get things in the "close enough" range.

mike

I'm rusty at cross-overs, and it was just a hobby. Back in my day I used a calculator, now I see free programs...

If you could give a few values for people to put in place of the cap that would be :thmbsp: :thmbsp: I say a few as they can listen and decide which they like best, or at least get it in the ballpark better than it is now if it really is 2 ohms lower than should be.

here are the values for the 2nd order low-pass: Edit I need to recheck the values, I may have traced the wires/terminals wrong.

 

[mashaffer]

Getting close to bed time and a full schedule for a couple of days but I think what I would do is use the basic capacitive reactance formula to get a ballpark idea and then use LTspice or similar to tweak it.

Xc=1/(2*pi*f*c)

So using the existing crossover values and find the frequency where Zc=driver Z. Then put that frequency in with the new driver Z and solve for C. This should get you in the right general range. Now simulate using the existing crossover component values except use the newly calculated C. Now tweak the C using standard values until you get the original crossover point.

There are also probably online calculators that would be easier than Spice assuming that the original crossover is a simple 2nd order and not something fancy.

mike

 

[jamesm007]

BTW

I see your an administrator. I noticed just now making a donation you guys are just a couple of miles from me. I use to go to the Gramophone and still go to Woodward Camera. Years ago in the good ole days I lived in all the shops around there (down Woodward toward maple... you know . Interesting. I did not know you were so close.

For what is worth... (nothing) lol

 

[RayW]

A problem with this whole thread is that a 4 ohm speaker isn't 4 ohms and a 6 ohm speaker really isn't 6 ohms. It's just a nominal value so that they can be binned and hopefully keep an amp from cooking. In order to see if the PE woofer will act the same in the crossover you need to run an impedance sweep on both it and the original and see what the impedance actually is at the crossover point. You can't accurately simulate a crossover using the DCR.

Chances are you're going to be well into the inductive rise of the coil and it will be much higher than 6 ohms. You might get into an issue of sensitivity at lower frequencies where a true 4 ohm speaker will draw more current, and consequently more power, than a true 6 ohm but most likely they aren't truly 4 or 6 ohm drivers.

 

[fastbike]

Even better, given the general practice for multiple versions/suppliers by Realistic, of making a judgement made based on one pair of Mach Ones (and acting like a world ending crisis).

 

[HomeBody]

A problem with this whole thread is that a 4 ohm speaker isn't 4 ohms and a 6 ohm speaker really isn't 6 ohms. It's just a nominal value....

Very True. You can test using a DOM and get one reading...then push on the speaker cone and witness the values rise.

Chances are you're going to be well into the inductive rise of the coil and it will be much higher than 6 ohms. You might get into an issue of sensitivity at lower frequencies where a true 4 ohm speaker will draw more current...

My first guess would be to err on the side of caution and opt for the 8 ohm driver.

 

[dc270]

Perhaps PE can post an impedance sweep on their Tech Talk?
DC!

 

[jamesm007]

Even better, given the general practice for multiple versions/suppliers by Realistic, of making a judgement made based on one pair of Mach Ones (and acting like a world ending crisis).

Kinda not fair. I posted pics of me rebuilding my Machs and my history of them of almost 30 years. During those years I have done a lot of research on them. I knew there was two versions really but did not know all the technical stuff of the different ohms as I only researched my 4029s and not as much info was avaliable. But the Shack did have a parts list and only listed one woofer. When I learned years latter that there are replacement woofers for the Mach Ones and the 4029 I was .

However doing my homework including calling Parts Express who indeed verified the 4029 uses a 6 ohm driver but there data sheet says the Mach One 4029 does not use a cross-over, well not for me, but for others who may buy this driver I wanted to let know its according to Parts Express of the wrong impedance. I did my home-work.

For some person scraping up money to buy a driver and finding it was a bit wrong it could be a very big deal, its not my money nor any-ones but the buyers.

How to convey the information? I felt it was as fair as possible, 1) I did research and could find no one with a 4 ohm driver 2) I asked Mach One owners if any owned a 4 ohm driver, at the suggestion of one I called Parts Express 3) I called Parts Express who to my disbelief confirmed the 4029 used a 6 ohm driver, but no cross-over for the woofer.

Now folks know the truth. Personally I don't care as I mine are in very good shape, I will just re-foam them and my main system consists of definitive tech towers and a sub, I don't listened to the Machs its for fun project as I have had them almost 30 years.

But how else to convey and make sure folks knew, as that woofer was being pushed as a drop in replacement for the 4029. And it may well work. But at least you know before you spend.

I fully know the impedance changes with drivers I designed and built speakers and cross-overs (for a hobby) years ago, but its still going to affect the cross-over as you have three woofers one a nominal 4 the other 8, and the right driver has a nominal impedance of 6; at 1khz its probably not going to be at the right value. I can in the future do an impedance sweep of my 4029 woofers and list it. Vifa and most companies list the impedance curve so you can know.

Its all :thmbsp: folks to those who have interest.