MCM 55-2421 came unglued in a T18. What alternatives??

[But it Hertz]

So My MCM 55-2421 woofer fell apart on me today. The glue holding the yellowish "sub cone" (don't know what you call it) between the magnet and the cone came unstuck making a horrible scraping noise.

I wasn't pushing it too hard. I had it limited to 20v and it is in my office... so no heroics going on. Certainly no burning smell apparent.

I'm kind of disappointed.

The BFM instructions say there is a choice of 3 drivers for the T18:

MCM 55-2421 - http://www.mcmelectronics.com/product/55-2421
Dayton Audio DCS205-4 - http://www.parts-express.com/pe/showdet ... er=295-200
Tang Band W8-740P - http://www.parts-express.com/pe/showdet ... er=264-854

Am I going to fall foul of any mounting hole differences if I choose a different driver? If so that would suck. Deeply.

Any other drivers to consider?

I'm of the opinion that I don't want to replace it with a cheap paper cone job.... it's just not worth the hassle. I want something decent to fit and forget.

Also, anyone know what MCM's returns policy is? I ordered it on 9/5/12 and it died tonight. I have the original packaging and it doesn't smell burned out. Do I have a case for refund?

Thanks in advance.

[Gregory East]

It sounds like you have a good case for a warranty replacement at least.

[shawn_g]

I've used the Dayton, the MCM, and the Infinity 860W in my builds. A lot of people like the JBL GTO804 as well.

Of the three I've used, the Infinity had the highest build quality, with the Dayton close behind. The JBL and Infinity specs are out of the recommended range, but the Infinitys sound great in my Table Tuba, plus they're only $40 on Amazon. As far as I know, the mounting holes should line up between the different models.

I haven't heard of any MCM failures like yours, so it might be wise to contact MCM like Gregory mentioned and see if you can get a replacement for free due to a manufacturing defect.

[AntonZ]

I have used the Tangband. Got one in my AutoTuba, another in a T18. Both working fine after a couple of years, the Autotuba has spend two summers and winters in the trunk, heat and cold, with no issues. The T18 lives in the house, no extremes. I like the smooth and deep bass of both, but they do not get pushed to their limits.

[But it Hertz]

Thanks guys, some great comments & suggestions here. I'll see how I get on with MCM tomorrow.

I took a picture so you can see what I'm on about. I'm holding the cone forward with my thumb. That's the ridge of glue you see there that came unstuck.

[biggerrigger]

That's a spider glue line attachment failure and it is very uncommon to have one fail like this and it is indeed a manufacturing failure. MCM should have no problem doing a warranty exchange for this driver after they see the picture of the failure area.

[But it Hertz]

Well that's good news (about the manufacturing fault). I'll report back here tomorrow after I have spoken to MCM.

So between these 2 drivers:

Dayton Audio DCS205-4 - http://www.parts-express.com/pe/showdet ... er=295-200
Tang Band W8-740P - http://www.parts-express.com/pe/showdet ... er=264-854

The Dayton is closer to the recommended specs and the Tang Band is much more expensive (better quality speaker??) but getting close to 20% on one of the numbers.

Anyone care to express an opinion on which one would sound better in a T18? I presume the Dayton because it is pretty much on the nail spec wise... and arguably better than the MCM 55-2421 that I'm replacing?

------

I liked the idea of the Infinity http://us.infinitysystems.com/product-d ... f860w.html because it looks like it would take more abuse being rated at 250W RMS.

But like sean_g says the numbers are off. I don't want to be "that guy" who asks stupid questions and then someone uses the "beating horse smiley" on me but the Infinity has a 4dB higher sensitivity despite being much stiffer sprung (approx half of the recommended Vas).

Infinity Sensitivity (2.83V @ 1m) = 91dB
Dayton Sensitivity (2.83V @ 1m) = 87dB

http://us.infinitysystems.com/tl_files/ ... _PI_EN.pdf

That seems counter intuitive to me.

I'm here to learn and I'm really enjoying my journey. Any insights would be gratefully received! Go easy on me please!

[Ryan A]

Those sensitivity numbers are wrong and irrelevant. In the AT the response and sensitivity of both drivers will be very very similar.

[But it Hertz]

Wrong? How?

I thought the sensitivity would be useful in comparing 2 speakers? One is more than twice as loud as the other for a given voltage. How is this irrelevant?

Could you please expand on your comments so I can learn from this?

[Ryan A]

It could be due to differences in how different manufacturers test. For instance full space/half space/in car/ 2.83v vs. 1w, etc.

The JBL is 91db and the TB is 84 db, or so they say.

It was tested and determined that in the Autotuba both drivers were within 1db or so for the JBL and TB with no noticeable difference in sound.

See this thread:

http://billfitzmaurice.info/forum/viewt ... hilit=tang

Page 4 1st post is where the actual comparison is.

[Bill Fitzmaurice]

Wrong? How?

I thought the sensitivity would be useful in comparing 2 speakers? One is more than twice as loud as the other for a given voltage. How is this irrelevant?

Could you please expand on your comments so I can learn from this?

Because it's a horn.

[But it Hertz]

http://billfitzmaurice.info/forum/viewt ... hilit=tang

Page 4 1st post is where the actual comparison is.

Excellent. Thanks. Just reading the whole thing now.

[But it Hertz]

Because it's a horn.

I'm finding this fascinating. I'd like to properly understand this rather than just do what you say. Well, as much as I can anyway.

So, I can find lots of data (and opinion) for loads of drivers for various (dare I say "Traditional") enclosures...... but not a lot out there that talks about horns with any clarity.

Do you have any educational material that will help me understand the basics of horns versus sealed or non sealed enclosures?

I have a friend who got really fired up about this when I showed him my progress so far and he started asking loads of mathematical questions about horns. I just said, woa... I'm just following plans... I'll maybe ask around for you.

He has a point though. It would be great to have a little better understanding for sure.

[But it Hertz]

It was tested and determined that in the Autotuba both drivers were within 1db or so for the JBL and TB with no noticeable difference in sound.

See this thread:

http://billfitzmaurice.info/forum/viewt ... hilit=tang

Page 4 1st post is where the actual comparison is.

OK, so the JBL and the Infinity have virtually identical specifications. So in theory the Infinity will perform the same as the JBL

(and as the same as the Tang etc etc),

Correct?

[shawn_g]

It was tested and determined that in the Autotuba both drivers were within 1db or so for the JBL and TB with no noticeable difference in sound.

See this thread:

http://billfitzmaurice.info/forum/viewt ... hilit=tang

Page 4 1st post is where the actual comparison is.

OK, so the JBL and the Infinity have virtually identical specifications. So in theory the Infinity will perform the same as the JBL

(and as the same as the Tang etc etc),

Correct?

Here's a thread I started to get an opinion on the GTO804 vs 860W. Bill said the difference between the two are too small to make a difference.
http://billfitzmaurice.info/forum/viewt ... =1&t=18421

If the drivers weren't so difficult to install, I'd pull one of the Infinitys out of my Table Tuba and do a side by side REW measurement in my T18 using the Infinity and the Dayton. One thing I just thought of is that you might want to check the max mounting depth on the T18. The Infinity mounting depth is a little deeper at 5 3/16" compared to the recommended drivers.