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

[But it Hertz]

I didn't say you can push it with impunity. As frequency goes down excursion goes up, with any speaker, and as it's a 40Hz design that's as low as you should run it unless at low levels.

OK, got it! Thanks for your time

[Ryan A]

Yes those drivers are beasts...the Infinity as well as the JBL. While it was ill advised to test to 30 volts in free air, it does speak volumes to the build quality of some "car" audio drivers I might add. Car drivers get a bad rap by some around here. The JBL gto804 (twin brother of the infinity) is good to 40 volts above 40 hz only in cab (don't dare try it it free air), and I'm sure the infinity could go similarly high. They will bottom very easily below 40 hz in the AT though (not sure about T18) so if you do plan to go that high you need a steep HP filter.

[But it Hertz]

Yes those drivers are beasts...the Infinity as well as the JBL. While it was ill advised to test to 30 volts in free air, it does speak volumes to the build quality of some "car" audio drivers I might add. Car drivers get a bad rap by some around here. The JBL gto804 (twin brother of the infinity) is good to 40 volts above 40 hz only in cab (don't dare try it it free air), and I'm sure the infinity could go similarly high.

Interesting. I can't wait to try it out. I'm sure I got away with it.

Just a couple more hours to go now. Got up early and did some dressing up of the baffle and did some more epoxy work so that has to dry. Mean while the driver is being broken in.

I should know how it sounds tonight. I hope it sounds as good as the 55-2421 after all this!!!

[Ryan A]

Don't forget to check for air leaks too before you do, especially around the driver gasket with your modifications. This can also lead to over-excursion very quickly, as well as significantly reduced performance.

[But it Hertz]

Don't forget to check for air leaks too before you do, especially around the driver gasket with your modifications. This can also lead to over-excursion very quickly, as well as significantly reduced performance.

Yeah, thanks. Will do. I'm hoping it will be good. The baffle will be perfectly smooth by tonight. I'll post a picture.

I have a rubber tube. I stick one end in my ear and then "sniff" around with the other. Works really well and I can check behind the driver as well. It was leaking in 3 places last night before I filled any holes.

This method is also great for detecting the source of strange noises under the hood BTW!

[Grant Bunter]

Some car drivers deserve a bad rap.
History says that, as a generalisation, their figures are over inflated and they don't hold up to long term use like pro drivers do.

Having said that, there are some excellent car drivers. Plenty of threads here attest to that.
IMO the issue is telling people that it's ok to use car drivers when the designer of the cab says that should not be done for a particular build type. A single bad review due to "outside the square" driver choice affects the designers bread and butter, not the builders.

But it Hertz,
Great recovery. Fill that void with a little PL and sand it flat again after setting.
And don't worry about the inside, once the access panel is back on you can't see it lol.

And you're right, if you don't care about replacing drivers because they are cheap and in the greater scheme of things it doesn't matter, it's only money. Different story if you spend big money on your drivers and it affects your income. Always good to learn though...

[Ryan A]

Some car drivers deserve a bad rap.
History says that, as a generalisation, their figures are over inflated and they don't hold up to long term use like pro drivers do.

A single bad review due to "outside the square" driver choice affects the designers bread and butter, not the builders.

You wanna talk about a bad review? You're looking at it in this thread, for the recommended MCM driver.

Sounds like you must've had a bad experience with a car driver in the past? Otherwise I'm not sure where you get your beliefs/knowledge from, but we've beat this issue to death...cheer up

[Grant Bunter]

Oh FFS,
It was a driver manufacturer fault that lead to this thread. Not the design. Or the recommendation for the driver.

Yes, I've had bad experiences with car drivers in cars, but not so with pro audio drivers in pro audio. That's not really the point though.

If the design calls for pro audio drivers, that's what I'll use.
After all, if you bought a commercial pro audio cab off the shelf, it would have pro audio driver in it. You wouldn't have the opportunity to choose a driver, and that cab would be designed around the driver installed in it. Hell, buy a preassembled car system and you don't get a choice either.

BTW, I'm not unhappy.

Apologies But it Hertz

[But it Hertz]

Apologies But it Hertz

It's all good

[bassmonster]

The JBL gto804 is good to 40 volts above 40 hz only in cab)

If this is true, that's pretty awesome!

[shawn_g]

[But it Hertz]

It lives!! The driver had about 18 hours break-in on top of the rude awakening I gave it yesterday.

Here is the finished baffle. I decided on a touch of bondo because I wasn't 100% happy with the sealing surface. I debated the wisdom of using bondo so close to the driver but I decided this is now my development sub and as such would make a great bonfire if it gives me any more trouble.



Did I say 10 minutes to change the driver? It was a RIGHT old PITA to get in there. It fought me every step of the way. Those t-nuts need to be bang on to get started and I really struggled to get them all started at the same time. It took me an hour to wrestle it in there... but there it is... home at last! Hurrah!



OHHHH FFS It leaked in the same 3 places as last night!!!! Turns out it was leaking from the joints in the gasket which is in 4 pieces. There is only one thing I prefer about the 55-2421 and that's the single piece gasket.

WHHYYYYY? Infinity WHHYYYYY? Just put a note in there to put some sealer on before install and save us all a load of hassle!!

I was in no mood to take it out and fix so in a huff I put a dash of PL over each gasket joint. I was CRAZED at this point. I don't mind admitting I did a little dance, stamped my feet and shouted at the walls.



Luckily the PL worked and I chucked on the temporary cover. This makes a huge difference to the sound.



So first impressions are very good. Obviously I'm going to say that after such a traumatic couple of days but I'm totally convinced it is a better T18 for it.

It needs more power to drive it but goes waaaaay louder than the 55-2421. It seems to dig deeper as well and feels more effortless. It is very difficult to put my finger on why I think it sounds better. I'm going to spend a week with it... I reckon it will take me that long to figure it out.

One really pleasing discovery though it that it appears to be a smoother curve. My office is 12' x 15' and the 55-2421 sounded very up and down in volume during a sweep. The 860w sounds more uniform. Next week I'll make some SPL charts with REW and post them here. I guess I'll take one from my desk and another one 1m from the horn mouth in the middle of the room?

I need to figure out what makes a valid numbers. Can I choose a frequency, give it 2.83V, measure at 1 meter and use my SPL meter to declare my version of sensitivity or is this fictional bullsh*t?

If anyone wants me to take a measurement in a particular way let me know so I can make it valid.

I have REW, a checkmate IEC651 type 2 SPL meter and a Behringer UCA202 USB sound card so I'm probably right at the bottom end accuracy wise but I hope a can produce some meaningful figures for the common cause.

I'm away this weekend so I'll pick this project up next week.

Over all thumbs up!

[But it Hertz]

Oh, and I would NEVER do a speaker model change again. Nooooooooooooooooo! Not worth it!!!

Although it is fair to say I do like the new sound. A lot.

[But it Hertz]

The JBL gto804 is good to 40 volts above 40 hz only in cab)

If this is true, that's pretty awesome!

This leads leads me to talk about another thread running in my brain:

After "enjoying" a BFM near social death experience last night... say someone gives you a subwoofer in a box but you have no idea what the design or driver is. How do you go about figuring out what your limits are without damaging it?

[Grant Bunter]

Has the driver or the box got any info on it?

You might track down (eventualy) that Brand X sub is loaded with blah blah driver, and get some TS specs if it has some and go from there...