2245 cone questions

Hi,

I am keeping an eye out for a pair of 2245Hs, & noticed this ebayers 2245 auctions. I am unable to bid as I am in Australia, but he mentions some things about the cones that I seek clarification on.

In This auction;

http://cgi.ebay.com.au/ws/eBayISAPI....ory=47095&rd=1

,he mentions "USES THE ORIGINAL WHITE BACK CONE". Is this a valid method of determining an original 2245 cone?

In another of his auctions,

http://cgi.ebay.com.au/ws/eBayISAPI....ory=47095&rd=1

,he mentions "USE ORIGINAL JBL CONE KITS THAT ARE THE NEWER GLASS FIBER/PAPER COMPOSITE MATERIAL". Is this composite material cone kit for a 2245, or are they meant for a 2241 or somesuch? What effect may it have on the T/S parameters?

Thanks in advance & regards,
Phil

Hi Phil,

I'll take a stab at this one. Others on the forum will know more about this subject, but that little line on the bottom of all of JBL's data sheets about reserving the right to make improvements...

To my knowledge, the first 2245s used a heavy coating of white aquaplas on the back side of the cone to add mass and stiffness. Later ones used gray colored aquaplas and possibly a different paper composition. These very well may have come from a different vendor. JBL had cone vendor issues during the run of 2245s.

As far as the latest ones using glass fibers, I have no idea, but it certainly is plausible.

To my knowledge, all of the 2245s have the same TS parameters.

Widget

I was wondering if/when this thread would show up...

The parameters are different but if you design around the original parameters for a target enclosure size around 6 to 12 cubic feet you should be good to go. That size volume completely dominates the high compliance 2245H, regardless of whether it is the old cone, an interim cone, or the newest cone.

I can't say I would recommend running an old cone on one channel and a new cone on the other channel. Match both channels.

If that isn't good enough then you will have to measure the parameters yourself. Be warned that the 2245H with it's extremely high compliance is one tough cookie to measure. Basically it's just a massive super sensitive microphone.

HI guys,

Thanks for the replies, & sorry for the tardy response.

Given that my initial use for 2245s will be to place them in the sealed off bottom section of my A7s, you have put my mind at rest.

They now have 077 "crystal" slots for the top end, it seems appropriate to have more JBL for the bottom end.

So much for two-ways!

Regards,
Phil

How large are the sealed enclosures for the 2245H's?

Can you call an A-7 a sealed box? I realize you can plug the port, but with all the flexing of the sides I doubt it is really a sealed box.:D

I reckon on a volume of roughly 270 litres before bracing. I am bracing extensively using Corian stiffeners on the walls, then joining all walls with 1 1/2" dowel. I will then add damping material & finally cladding the entire cabinet in 1" Corian. I can't imagine an enclosure that will flex less.

Anyway, after bracing etc, I will have easily 250L to play with. I can fill it as need be. I initially intend to have a sealed enclosure, as it should be a bit more forgiving of straying from ideal dimensions.

If it all comes to naught, I will have some nice drivers to start again. Put those slots back in my L65s where they came from.

Regards,
Phil

I was kind of joking about the flexing. Certainly a heavily reinforced cabinet will only be an improvement. What are you crossing over to? The 2245 is not a great driver above about 300Hz.

As far as the volume goes, 250ltr sealed will yield a -3dB of about 65-70Hz and a Qtc of 0.46.

A 135mm X 135mm X 127mm port will yield a -3dB of about 37Hz with a 28Hz tuning. If you are plus or minus 10 liters it only changes about 1Hz.

I would seriously consider adding the port.


Widget

Phil,

I quiet hello from down under.

I would be interested to know your plans for the 2245.

I've been through a few hoops with these drivers myself of late..

Try a local search also, a Pro Hire place in Adelaide had some not long ago. I git mine from Cannon Sound.

As to the tuning, the above applies but it depends on what you are doing with the driver.

Ian

Hi Mr Dubya,

I realised you were joking of course, I've been skulking the back alleys of this forum for a while & "know" the personalities, even if they don't know me. I am bi-partisan when it comes to J.B's legacy; Lansing is my _middle_ name.

It's all a bit of a pipe dream to make use of 2245 drivers for this project, they are a bit hard to come by in this hemisphere. I am currently using a REL Storm as a sub, & it seems kinda silly to use a 10" as a sub & a 15" as a midbass!

My intention would be to xover at roughly 200Hz, about where the front loaded horn of the 828 is running out of puff.

If I ever track down a pair, I will certainly take your calcs under advisement, & will, I'm sure, be asking more q's here. A couple of the guys over at Todd White's forum have made this mod with success, it seems.

Regards,
Phil

Sorry Ian,

I missed your response whilst composing one for Mr W.

Well, in essence I intend to block off the bass reflex portion of a pair of Altec 828 enclosures to make an enclosure for the 2245s, actively crossed over at 150-200Hz. I am very open to suggestions as to how best to implement this.

Funny you mention Cannon sound, I picked up a spare 2405 from them about a year ago, & had an enjoyable half hour pottering their graveyard of drivers. I seem to recall a bunch of 2245 baskets with shifted magnets, but nothing that could be re-used. I'm sure you know the cost of replacement cones over here, & that it would be cheaper to buy a complete used pair in good condition.

I'm not owed an immense amount of money by my Altecs at the moment, so if it all doesn't work out, it's not the end of the world. As it stands at the moment though, I'm having a lot of fun, & learning a lot at the same time. I reckon they sound pretty damn nice actually!

I've enjoyed reading about your project, maybe one day we can catch up. Bags not bringing my speakers 'round to your house though!

Regards,
Phil

Enjoy the Journey Phil.

Ian:)

Mr. Widget is right. If you're going to cross over so high then you may want to go vented in order to maintain balance. Either way it's quite easy to try sealed first and then vented.