2440 Terminal Binding Post inspection

[cvengr]

I decided to embark upon constructing/fabricating a set of 4355 lookalikes from spare parts and have enjoyed and appreciate the efforts of these outstanding forums. Please pardon my obvious lack of knowledge.

I've recently acquired a pair of 2440s with horn, only to discover one of the red terminal (binding?) posts loose and rolling around in the bottom of the shipping container.

There are some cob webs in the horn throat as well, however what appears to be a fine mesh screen at the bottom of the throats appears in good condition. Last user reported they had recently been tested and in good operational order.

I am tempted to dismantle the piece to determine how to repair the post, but am unaware if there is a gasket seal that might be damaged if I were to remove the horn and outer casing.

The loose terminal post appears to have a female threaded tap, however, the 2440 terminal space adjacent to the attached black terminal, is void a male post or bolt to screw the terminal back into place. I can view an off center nut or tapped female screw connector through the outer casing of the 2440 where the terminal appears to attach, but no obvious place to attach the post.

This leads me to consider either the piece has always been in disrepair, or that there might be a loose threaded bolt or nipple floating around the inside of the speaker casing, or stuck to a magnetic surface inside, so it might not be wise to energize the speaker until it is properly inspected.

I suspect this is a simple screwdriver and patience exercise, but I don't want to blunder into damaging the speaker inadvertantly by removing the housing if that is only performed when replacing the disphragm or any possible metallic gaskets.

Accordingly, I'm looking for an assembly diagram of the 2440, with replacement part nomenclature or part numbers, or am I making this too complicated?

Any corporate knowledge on this is appreciated. Thanks in advance for your patience in reading and considering this situation.

[frank23]

opening up the back cap of a 2440 is no big deal

just unscrew the four bolts on the back cap and then take of the back cap

as the internal wires are stiff and not too long, feel which way the back cap wants to go and take it off gently

apart from the back cap, there is nothing you can remove easily from a 2440

if you don't need to, don't take out the diaphragm if you've never done it before, it can be stuck to the poleplate and alignment pins

you can gently fasten all connections inside, just make sure the screwdriver and bolts are not drawn to the diaphragm because of the strong magnetic field

for cleaning the magnetic gap etc there are a number of "how to" descriptions in this forum, you might want to search for "sticky tape" I think

frank

[remusr]

....the webs & dust can be vacuumed from the internal horn with a micro-attachment for your home vac. The screen you see is in front of a phase-plug, not the dia so you can't touch delicate parts. You can run the vac brush across the screen but don't push on it hard as old ones could come loose. Then you gotta open it up as above.

[cvengr]

Thanks very much to both of you. There had been some past questions on binding posts without much/any feedback.

I recognize it has to be a dumb question, but I'd rather risk being thought stupid, than risk the bucks on errantly damaging the beast.

Before testing energizing the 2440, I've also picked up an M553 crossover to help filter the lows and highs out from the driver signal.

The M553 has balanced XLR (Cannon plugs) M/F receptacles/jacks.

My power amps have RCA/phono plug type connectors. Separate grounding/bonding at the amp.

I've noticed over the years that even the most expensive RCA/phono plug connectors can develop shorts or corrosion on some AL/Cu connectors, espeially with change of equipt temperature (thermal expansion) and even some shorting between connection within the insulation jacket and the connectors. Accordingly I tend to like the strain relief and simplicty of the XLR connectors.

I typically prefer upsizing the conductors from say24/26Ga for inexpensive patch cords to say, 22/18Ga with shielding, while the connectors themselves, I don't find to be as significant regarding type of material, because there is frequently 2-3 times the surface area for electrical connectivity than required at those connections even in soldered joints.

I'm curious if others on the forum have had some practical experience that leads them to favor the twin binding post vice XLR or 1/4" jack connections, and/or RCA/phono plug power connections, and why not just bond/gnd the heck out of everything?

Are there some components for which the floating ground is preferable?

[cvengr]

Well, my virgin entry into a used 2440 proved successful. I followed your recommendations with trepidation as the rear bolts sure looked like screws from the outside.

Once the lid was off, sure enough a small screw and rubber gasket for the terminal binding post were laying on the magnitized surface of the flange around the outside of the diaphragm. A simple screw reattached and all parts on hand from the bottom of the shipping box.

It pays to give attention to detail when unpacking those supermarket boxes used by e-bay sellers when they inexpensively ship their items.

[Rolf]

Good to hear the survival story.:D :applaud: :applaud: :applaud:

[cvengr]

Now for the next struggle. Testing the system and components.
I'll give it a shot to see if it works as its intended, then troubleshoot by system, then component.

The 2440s seem to sound just fine. At least operational. I have an old dbx 20/20 I will later run some testing on the system, but first checking out the other components.

I've triamped the system using a JBL M553 crossover after the preout of the preamp.

From the Xover, the low band is sent to a McIntosh 2300 powering 2- 2235Hs, Midband to a Yamaha M-70 powering 2-2202Js, and mid/high to a pair of monoral Kenwood L-07MIIs, one per 2440. I have some 2307s on the way with some of Mike Caldwells 2405 lenses and some spare Infinity tweeters to play with later.

1st attempt, the mid/low and mid/high work fine, although the mid low doesn't seem to be getting very low. Absolutely nothing out of the 2235Hs, although when I power down the system slowly and sequentially, I do hear a very feint click on the 2235s when the xover is de-energized after power amps are off.

2nd attempt I trouble shoot and flip the Mac and the Yamaha with crossover, meaning the speaker connections remained the same, but flip flopped low and mid bass, just a low power test to check continuity .. filters should keep everything within opperating range. 2235s are audible as midrange through the MacIntosh, though some corrosion on the rheostats seems to be a problem. Meanwhile nothing out of the Yamaha, so the low pass section of the crossover doesn;t appear to be allowing anything out, although it has some continuity as when xover de-energized a feint click is still heard. Keeping minimal power and powering back down.

McIntosh 2300 seems to be giving me problems along with the JBL M553.
The mac's volume/output attenuators appear to have corrosion on their rheostats. As I turn the knob, sound cuts out all together then back on. Wiggling the knob with a little finger pressure causes the dial to behave as though it's corroded or improperly connected.

Meanwhile the JBL M553 has both of its divide by 10 LEDs lit on the low pass. Manually set Xover set for first 190, the 200, then 400, in all cases the LED on both channels independently lit.

I've swapped a couple of patch cords, checking RCA connectors for corrosion, found a few with intermittant shorts/breaks, and swapping out.

Ist Preamp was a Yamaha C-2A using a tuner input and a phono input. Intermittant short appeared in its Stereo/Mono switch from apparantly corrosion.

Swapped to a backup Kenwood L-07CII preamp, and some shorting appears to have disappeared, but still am having corrosion problems somewhere in the connectors.

I've gone with all new XLR to RCA plugs/cabling to/from the M553 Xover, but they are only a foot long, so I picked up new RCA barrell connectors and extended with RCA patch cords.

The more I trouble shoot this and still have no bass, I now wonder if my Infinitys RSIbs were OK after all and maybe my problems are merely with the Mac and connections, and Preamp rheostat attenuators, ie corrosion in various places. I never have had great bass out of the Infinitys

I might be better off going all XLR connectors and making them accessible for maintenance, same for connections to the speakers enclosures. I'm ready to brush up on my RLC circuitry and simply make some clean new crossovers, re-conductoring and fimr up all points of connect and begin again.

Anybody else have similar problem with volume/attenuation control knob/rheostats corroding and giving similar headaches, or am I missing something simple and obvious? ????

[Zilch]

If /10 is engaged, M553 Low/Mid adjust range is from 18 to 200 Hz....

[cvengr]

Thanks, Zilch. I had read that, and suspected that was my next step.

I flipped the M553 xover and sure enough, the /10 switches were depressed, and I elevated them back up. I had checked them prior to energizing, but figured I was better safe than sorry and energized the first time with them depressed.

I wanted to at least hear if the components were functional, but carefully until the entire design is properly set up.

Of course, after taking 10 times the effort and time on each step of the setup, I was finally ready to power up. Carefully turned volumes down on all components, preamp output off engaged, speaker outs engaged on each power amp. Triamping the system with a McIntosh 2300 on the 2235Hs, one per channel (at first) These had just recently been reconed by Chris himself at CKSpeaker, then the Yamaha M-70 powering the 2- 2202Js (albeit 16ohm, but I received a fair prive and wanted to experiment with them before maybe rerouting to 128/Hs. On the 2440s with 2ft exponential horns and serpentine lenses I ran in series with a pair of 2407s powered by dual Kenwood M-07II power amps.

The signal came from either a tuner, turntable, or CD routed through a Yamaha C-2a preamp to the M553 xover.

1st attempt, I powered up the preamp, then power amps with outputs off, then powered up the xover only to hear an amazingly clear gunshot, then rapidly powered down the system. Of course after thinking a few very frustrating thoughts, I realized the preamp first, then xover, then each power amp slowly might be a better sequence of operation. It took me a week of trouble shooting and checking things before I felt confident enough to re-energize and pray no permanent damage had been done.

Everything seems to work fine now, other than my extreme hesitance to power up the system at all until I reason through the process again carefully, each step of the way.

I initially set the xover freqs at 290, and 1200 without the 2407s.

Later I shifted the lower crossover down a bit to about 150 and raised the mid to about 2000, using the 2202J s more thoroughly.

The 2407s overwhelm the rest of the system, but that was to be expected from their lower impedance.

All four 2407s measure 4.3ohm DCR
2440s measure 7.8 and 6.5ohm respectively (not very well matched, but I have enough separation in controls to compensate crudely.
2202Js measure in at 10.9 and 11.3ohm respectively.
2235H measure 5.9 and 6.5 respectively

I had preferred to use the 2405s and have an order out for a pair, but decided to experiment with the e-bay 2407s until I could afford the former HF tweeters. Ebay seemed to artificially raised the 2405 pricing for about 6 wks and now has settled back down. Four went today for 2@$162, $138, and $125 respectively (boy, I was tempted to bid).

FWIW, all the speakers came through shipping intact, although a heads up for those 2407s coming out of LA via ebay. They are fair deals, but ask the seller (Gonzales, I think) to be sure to pack with something more substatial than bubble wrap. The fronts and wire mesh have gotten scratched up a little from shipment. The magnets were all stuck together when they arrived, even though they had been packed individually, each doubly wrapped in bubble wrap and packed in styrofaom peanuts in one box. Recommend separating them by cardboard within the box in the future for any other observers. Damage was cosmetic, it appears, although it probably doesn't enhance the EM fields for the magnets to have stuck together a while. I suspect the magnetic domains haven't been terribly effected, but probably not the best packaging method for the type of device being shipped.

I'm now in the process of looking at enclosure configurations, passive xover options, and horn loading characteristics.

I began asking some peers if they had played with sound design. One of my associates had previously designed some showrooms for SoundLabs as an architect and had designed the showroom walls to be sand loaded (so that's why they sounded so much better in the showroom, eh?). I saw the same method used in some older Tannoy enclosures recently on e-bay. Another associate picked up my copy of Mathematical Methods in Theoretical Physics by Morse & Feshbeck ad remarked Morse had nearly been his doctoral thesis examiner at MIT. We discussed a few things and I had been studying acoustic principles from his former professors and their past publications, but then came to realize their emphasis is probably more concerned with acoustics of intensities greater by several orders of magnitude, although an interesting study. Another associate had recently designed and specced out some audio PA systems for a military function, using Technomad and Community speaker systems which claimed to have used on Trident subs, Navy cruisers and Space Shuttle launch gantries, so I figured we have sufficient specification for some robust environments. I had previously experimented with transducers, beryllium and titanium alloys from single crystal to various metallurgical compositions, and have been impressed by the older JBL components. It's been a pleasure experimenting with the signal processing, wave shaping and xover freqs with these components.

I've also read some recommendations of mounting the woofers about 3 ft above floor level for improved performance.

Given the above, has anybody here found the mounting of the 2235Hs 24" to 38" above floor level to actually improve their perceived response, or does the floor provide essentially a half wave reflection to improve the bass line? Obviously room acoustics may prevail, however, the wife prefers a speaker enclosure that can double as a bookshelf or something she can place nick-knacks upon, in order 'to become beautiful', whereas my perception of beauty is in the open front of the baffle exposing the cones and horns. (arrggghhh)

Accordingly, the controlling constraint might not be a physical characteristic of the speaker, but an aesthetic issue outside the aural domain. So, I've gone back to another associate who is an architect, reviewed some of his history of architecture texts regarding the italian rennaisance, studied some of Andreas Palladio's work, reviewed the funicular, and ran across the Karlson Horn.

Half of me says keep it simple and keep to a 4350/4355 clone design focusing on simple care in replication. The other half, says, go ahead and experiment to possibly improve on a good thing (then again if it ain't broke, don't fix it).

I've read some of the comments by Greg Timbers graciously posted on these threads regarding the original 2350/2355 xover designs and tend to think a custom built set will be better anyways, although, RTA measuresments and newer preamp/digital signal processing might overwhelm those efforts by an order of magnitude.

I suspect that over the past 40 years there have been some knock-down gorgeous armoire type enclosures built for these systems, which make the enclosure as attractive a living room piece, as the art of building the speaker components has become, but haven't seen much elsewhere.

Any recommendations regarding alternate designs to the Paragon, using these components in a a higher class enclosure and implementing the shape and form inherant in the Karlson Horn or free form enclosures, or how to match the horn loading of various components in those designs?

[Zilch]

That eBay seller has been told the same by just about every buyer. Never gets it. May be he wants some cosmetic shipping damage to cover up the fact that they're not as new as claimed in the listings.

******

2407Hs are also very high efficiency.

They need horns to control the dispersion, and to load them properly, as well.

Try the $10 JBL 90° x 50° PT waveguide and/or $38 OASR with them....

[cvengr]

Thanks, Zilch

Out of curiousity, I haven't found the 2202Js elsewhere. Do you know if they were they any less a speaker for reproduction than the 2202H?

[Zilch]

They are the same, except for the impedance.