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fast_mick
06-18-2006, 02:44 AM
I have bought my first JBL speakers 4425, I would have liked the 4430 but they are rare in Australia and I am after a nice big sound. When I was younger about 25 years my next door had 4333's and it really created a huge impression on me.

I am looking to support these with a sub woofer as the bass wont be as substantial.

I have a crown PS400 amp and PSL-2 pre-amp and Luxman turntable

I have a ebay bid in on a M553 crossover.

Now do I go for active or passive subwoofers and what wattage/size do I go for. I would like my system to have a full balanced sound, so the subwoofers would supplement the sound but appear integrated, also do I go for 1 or 2 subwoofers. My budget is probably US$800-$1000 for the subwoofers.

Thank you in advance for any suggestions, I am really lost in/on this

regards
Michael

doodlebug
06-18-2006, 09:16 AM
I've got 4425s and understand that you might want to go straight to a sub but I'd suggest a few things to do first:

* Make sure the foam surrounds on the 4425s are intact. If there *any* tears or cracks, they're gone. Don't try to use the speakers until its repaired. Hopefully this has already been attended to.

* Next tweek: Replace the crossover caps - all of them at once. I did this to mine - about US$40.00 in parts. This really snapped the imaging into place and made the upper bass frequencies more clear.

* Lastly, experiement with placement on your room. I've gotten massive bass out of the 4425s - and that with tube amps. No telling what the likes of that Crown will do for you.

*While you're at these tweeks, I'd suggest replacing the push-on speaker terminals with some good quality binding posts. That way you can use larger guage speaker wire easily.

Then, if all else fails, go with a sub. My experience is that sometimes trying to integrate a sub into a speaker setup is more problematic than just leaving them alone.

Cheers,

David

Zilch
06-18-2006, 11:33 AM
For two-channel listening (as opposed to home theater,) stereo subs are preferred.

Several members have mated 4425s with Citation 7.4 subs. They're a modest size (~3.5 cuft) vented box using a single LE14 driver (LE14H-1, factory).

Discontinued years ago, the originals are hard to find, BUT they're a simple and rewarding DIY project; even vintage LE14As will work at modest volumes. A pair of those was just listed BIN on eBay for $75. Use 1" MDF to build the boxes solid.

Many forum members use LE14s for subs in other cabinets with good results, as well. You'll have most of your budget left over using this approach. :thmbsup:

Use the forum "Search" function to find the details on Citation 7.4; they're discussed and specified in several threads here.

For crossover, M552 would do it. I'd continue to use the passive crossover in the 4425s, and not try to biamp them above the subs. They have built-in compensaton for the biradial horn.

If you want to use more of the budget, acquire a pair of LE14H-3 woofers through JBL Consumer and use a 150-300 watts-per-channel amp to drive them.

Chas
06-20-2006, 10:09 AM
I can't comment on improving a pair 4425's specifically, though a capacitor upgrade of the passive internal network would probably be a good idea. But, I definitely would bi-amp them to a separate pair of subs around 50-200 Hz - (room and sub dependant). I wouldn't recommend using an active crossover for the high pass section, a simple, first order passive network using good quality capacitors in front of the power amp is a great way to go.

Use only the lowpass portion of an active crossover for the subs (preferably 24 db/octave - this seems to give the best result IMHO). It's a bit of pain to find the appropriate xover point for your room, due to non continuously adjustable H/P xover points, but the result can be very rewarding.

fast_mick
06-25-2006, 05:02 AM
Guys,

Thanks for your responses they have helped greatly. I had a look at the woofers to make sure they were genuine. One was a 2214 and the other was a 2214-H1, but I think they are identical sounding. The rubber surrounds were in excellent condition, almost new looking.

I have played the speakers now and the bass is good. I am just learning but I tested them with some LP's I know well. I tested them with Linda Rondstat's Poor Poor Pitiful Me, I really like the drum opening and sure has a kick, the bass was strong but not real low. I played Evon Elliman's I dont know how to love him from the Jesus Christ Superstar Sondtrack to test high end intensity and it was great with absolutely no distortion.

I have ordered some second hand Le14-h drivers to build the subs and hopefully get some lower bass. It will take about 6weeks for them to arrive from the states. Sea Mail becuase they are very heavy and airfreight is very expensive. It will give me time to make the boxes so no rush.

I will post again once its all working I may need some help setting the crossover points.

tks
Michael

duaneage
06-25-2006, 07:21 PM
If the surrounds are rubber and not foam you've a problem. Replacing the foam surrounds with rubber will drastically change the woofers and stiffen them too much.

Might be why the bass is lacking.

fast_mick
06-25-2006, 10:47 PM
Sorry the surrounds are foam

fast_mick
09-16-2006, 11:20 PM
I purchased 2 x 2nd hand LE-14H-1 from another forum member to construct subwoofers as per Zilch's suggestion the design is based on a citation 7.4 but the size turned out to be 3.2cuft (due to a cutting stuff up) and is tuned to 32hz (Winisd) the shape is a bit shorter but deeper than the Citation. I have a JBL M552 crossover set at 90hz. A QSC plx2 1802 powers the subwoofers while I have in the photo a Yamaha M-40 for the 4425. The Yamaha has been replaced with a near new Bryston 4Bsst.

I have set an extra 4db gain through the crossover for the subwoofers, I may have to revise this is the power amps have different input sensitivities which probably has to be equalised, maybe someone would like to advise about this.

Also I am running the QSC amp straight into the subwoofer with no passive crossover. The QSC amp has optional 30hz cut protection that can be switched on and I have done this. Again advice sought.

I was a bit worried about the investment in all this as when I checked the Freq. Resp. of the 4425 its rated at 40hz +- 3db. Therefore I was thinking will the sub have an impact as all I am adding is maybe 10hz on the bottom.

Well let me say the the impact is huge but the funny thing is you dont notice the sub, the sound just appears more full/thick and bigger with more resolution anyway the guys that have subs will know what I mean.

I have been reading up in some other posts and other boards and was wondering would adding a deqx preamp be desirable to bypass the passive 4425 internal crossovers ie 2 way with the third way going to my subwoofer. Would it be an sound improvement.

I cracked out all my old vinyl, to give it a run and messed up the room a bit. Hopefully the pic posted.

regards
Michael

Zilch
09-16-2006, 11:54 PM
Well let me say the the impact is huge but the funny thing is you dont notice the sub, the sound just appears more full/thick and bigger with more resolution anyway the guys that have subs will know what I mean.Yup, sounds like you've got it right. If you "hear" the sub distinctly, it's either playing too loud, the phasing is wrong, or the crossover is at the wrong frequency to blend well with the mains.

Several members are now using Citation 7.4s or equivalent under 4425s. It seems to be a particularly good combination. When it's all working right, the subs are seamlessly transparent, as you describe. :thmbsup:

Toeing the 4425s in as you've shown broadens the sweet spot, and reduces early sidewall reflections, both good things, in my view.

Since you used PVC, you might want to try another pair of ducts for 30 Hz tuning and see if you like the way that sounds as well....

[HEY, there's no celebratory BEVERAGES in the pic! :p ]