JBL 4425: oiling the veneer, and bass boom

I recently obtained a pair of 4425 Studio Monitors from the late 80's. Now that the woofers have been re-foamed, a couple of questions:

The cabinets are in great shape, but appear dried out. Should I use linseed or tung oil on the veneer, or what?

No matter where I put them in a large, vaulted listening room, no matter how high off the floor, there is a strong bass underline. A giant, one-note boom. Is this normal for a 4425? Could the refoaming or age of the speakers cause this?

Otherwise they're great home theatre speakers. Thanks.

For the wood finishing portion of your post, my preference is "Watco Danish Oil". You wipe it on, let it set a bit depending on temperature and humidity and then wipe it off. I usually do this a couple of times, followed by a good buffing of the oil residue that is left behind. If the surface is in decent condition, that is all it takes. You should use their "Natural" color unless there are scratches, then you might want to use their "Walnut" color.

As far as boomy woofers goes most JBLs are tuned to be a bit boomy. Are yours in original condition with the original woofers?

I don't know much about the 4425, but typically JBL tunes their systems with a bit of a bass bump. Retuning the port to a slightly lower frequency should help. This is done by lengthening the port... I wouldn't recommend that you do anything permanent, but it can't hurt to temporarily add an inch or two to see if it helps. Ideally this would be done while being fed from a signal generator in a test set up so that you can monitor the impedance rise on both sides of resonance.

Hopefully someone with experience with this monitor can add some helpful information here.

Yeah, you might want to measure the tuning frequency of those enclosures and make sure they are 34 Hz or lower. What is the port again? 2.5" diameter port x 6" duct? You might want to measure the free air resonance of those 2214H's as well.

Yes, It's difficult to adjust: loudness effect (medium frequency level is lack)
Solution: enclosure to heighten ( stand: 60 cm )
or upside down ( stand 1 meter!!!!!)


herve M
4425 old user

I'm not sure there is a big difference in what oils do for wood, but after using a number of other oils, I've become a fan of Tung Oil. It has the ability to be waterproof, stay in the wood longer then most other oils and hardens with age making the wood more resilient.

Tom

Tom,

What brand of Tung oil do you use? I believe all of the products labeled as "Tung Oil" have some percentage of Tung oil with a mixture of other ingredients. I haven't used any in several years, but I remember some working much better than others. For the most part they create a bit more luster than the "Watco Danish Oil" which is fine if that is the desired result.

Hey, Mr. Widget...

I've used "Jasco" brand Tung oil with great results. The bottle doesn't give details on %, so I assume it's 100%.

It's kinda "goopy" (eek! Giskard is bound to Thesaurus me! ;) ). I use paper towels to apply (wearing rubber gloves) and then rub off excess after a few minutes.

Depending upon the desired gloss, after drying, I rub with 0000 steel wool.

Just thought I'd toss this into the mix...

Carolax,

How long have you listened to the speakers since the refoaming? IME, having refoamed LOTS of drivers of all kinds (including several LE15s, my pair of L77s, several L166s. a pair or two of L112s, a couple vintage LE8s, etc), new foam sometimes has to "break in"- ie, it gets more compliant after being played a few hours at a decent SPL level. A foam surround with too much stiffness, can raise the resonance frequency and the Q of the driver, making them boomy.

If you haven't done something similar, I'd try playing something with good bass content, at a good high volume level (don't overdrive anything, of course) and let them percolate like that for an hour or two. Let them sit for a short while afterwards, and them see if they sound any better...

As for cleaning and wood rejuvenation- I've had good luck with Old English lemon oil, applied medium-lightly with a Scotchbrite scrubbing pad. Gets all sorts of airborne debris back out of the woodgrain, and BOY, they just look IRRIDESCENT afterwards. What depth and sheen!

I'd do this, before applying anything like tung oil... if the speakers later start to look dry again after the lemon oil, then I'd escalate to something like tung oil or whatnot...

Regards,
Gordon.

Mr. Widget, and others,
I use Waterlox "Original" sealer/finish which is thinned tung oil.
Though lemon oil can be good for cleaning old hardwood surfaces, "lemon oil" is almost always mineral oil with thinners and lemon scent! It dries out and often leaves the wood in need of a higher quality, penetrating oil that flows in to the wood fibers. I still feel that tung oil is the best for adding a rich, wood-enhancing oil to porous wood surfaces (like walnut).

Tom

First, until I ran across lansingheritage.com and this forum, I thought I was the only fan of old JBL's left on this earth. For a numer of years I worked for a JBL sound contractor and did some semi-pro recording. During those years I owned or used the following JBL's: 4310, 4311, 4320, 4315, 4343, 4350 (yikes!), 4410, 4412, and my current LSR-32's and 4425's. It's nice to know I'm not the only member of the cult!

I appreciate the company, and the sage advice (as opposed to cerulean advice?). I'm going to go slather my 4425's with tung oil, play some Moby real loud for a day or two to see if the 'wooferitis' gets the cure, then check to see if my wife is still living at home.

No matter where I put them in a large, vaulted listening room, no matter how high off the floor, there is a strong bass underline. A giant, one-note boom. Is this normal for a 4425?

Certainly not :)
JBL's literature recommend that "the monitor should be monted against a wall. Other mounting location, such as away from a wall or at the intersection of room surfaces, cause uneven bass response".
In my experience (43xx series) that point is important. Maybe try to play a record with huge bass and find the best point.

What amp are you using?

Myself owning a pair of 4430 monitors I found out that these monitors are really hard to drive in the bass area. Efficiency and therefore power is not a problem but you have to be careful selecting an amplifier with a low output impedance (equals high damping factor). Certain tube-amplifiers like single-ended triodes are not really able to control a heavy 15" cone (155 gr. for the 2235H). Something similar might apply to your 4425 speakers. I would try a power amplifier having a damping factor at least one magnitude higher than the one you are currently using.
If you look at the schematic of the current K2-S9800 dividing-network you will notice user configurable resistors in parallel to the bass driver in order to adjust damping. Adding damping resistors in the 4425-network is also something you could think about.

Best regards,

Norbert

Excellent point Norbert. I personally can't stress the importance of lots of amplifier control for JBL 3-inch and 4-inch coiled LF transducers. I've harped (:p) on this since the first forum. Tubes are fine for everything else, but they really don't belong in the VLF and LF unless someone is specifically going for that particular sound character.

IDF and Gordon are right. You have to "break in" refoams. Not quite the same as a recone with a new spider but nevertheless...
That's why I recommended that you might want to measure the free air resonance of those 2214H's. You might want to measure the tuning frequency of the enclosures as well. If the enclosures measure too high above 34 Hz you have a problem.

*****

I just examined the 4425 schematic and it already has 50 ohms of resistance across the 2214 which drops the impedance peaks; the largest from ~ 112 ohms down to a reasonable 35 ohms.

Good question about the amplifier. I'm using an Adcom GFA-5400 which I originally bought to power JBL LSR-32's, and which it has done very well. I also use an Audio Research LS2 preamp because there should always be at least one tube!

I'm going to borrow a different power amplifier this weekend and see if it helps. Adding resistors to the crossover sounds like fun...maybe next weekend :>)

I've personally never had any trouble driving JBL's with Adcoms... I'd be very interested to know if swapping out amps solves your problem :)