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-   -   Newbie JBL horn question (http://www.diyaudio.com/forums/multi-way/37789-newbie-jbl-horn-question.html)

markzb 14th July 2004 11:42 AM

Newbie JBL horn question
 
Hello

Please forgive any shortcomings in my post. Im new to horn systems and hope some of you could offer some assistance.

I would like to try and venture into building a horn system for home use and it will be playing jazz and classical music.

As I am in a remote part of the world, and compression drivers are very heavy, it is very expensive to ship them here. And once I buy them, Im stuck with them.

Available locally are a pair of JBL 2445J 2" compression drivers.

What are your views on this driver? A most helpful gentleman in Australia who got me onto the idea of trying a JBL horn setup said that I should try if possible to get a pair of TAD 4001 drivers first if possible.

As these TAD drivers are not to be found used here, and perhaps are beyond my current affordability, I will be looking now at JBL units.

So....what are your views on this particular JBL unit.Is it a good sounding unit? Is it in the same ball park as that TAD4001?

Or are there perhaps certain models of other JBL compression drivers that you would reccomend.

Any suggestions appreciated on what to look out for!

Cheers

mark

Tim Moorman 15th July 2004 12:08 AM

JBL Horns
 
Hi markzb,

The 2445 is a good pro sound unit, but perhaps a bit harsh in a home system due to the titanium diaphragms.

I would consider the 2" JBL compression drivers with aluminum diaphragms such as the 2440/2441, or the older 375 model.
While not as extended in hf, they seem more relaxed through the mids. You will probably need to add a supertweeter or something like the JBL 2405 1" for output above 10K.

Some of the really old drivers like RCA used phenolic diaphragms, as well as some recent replacement diaphragms by people like Radian. Mylar has been used more recently in Community's M200, for example - a good sounding unit, but limited on the high frequncy extension to 4K Hz, perhaps. Most "affordable" 2" roll off rapidly above 8 or 10K.

The TAD 4001 are quite extended and smooth to my ears, but are costly due to massive build and beyrillium diaphragms. The lesser 2001 1" has fairly flat extension out to about 16K Hz, resonance around 380 Hz, and is much less money. Would work well on the right horn to perhaps 750 Hz with tube amps and fairly steep crossover slope.

Some of the new B&C designs look promising but I've not heard them. They now have a coaxial compression driver that would solve some problems with regard to dispersion, require one less horn, and with a response that looks good on paper.

HTH

Tim

mikee12345 15th July 2004 05:45 AM

since your in KL why not consider Paudio comp drivers? they are abit more unknown than jbls,but its worth considering.

Variac 15th July 2004 06:55 AM

Some of the the Paudio horn drivers have a very good reputation. Does anyone know which ones?

Some of their bass drivers horns drivers, and horns have specs very similar to certain JBL models- they are kind of clones

A problem is that they have so many models, it's hard to understand them all.....

Anyone a PAudio expert?

markzb 15th July 2004 09:15 AM

Thanks guys for your help so far.

I have learnt quite a bit already! And your friendliness is much appreciated.

Ok...so now I know that the diaphragm material makes a difference, and that perhaps titanium diaphragms are a lil too "sharp" on the ear. (for my application at least)

On this subject, I notice that some aftermarket suppliers are supplying various replacement diaphragm materials.

Thus, would it be correct to say that I could sort of "tweak" the sound to suit after I have put everything together by swapping the diaphragms with another type?

Why I bring this up is that, as I mentioned, whatever i get.......Im stuck with it. So if I can "experiment and taste" what other diaphragms sound like, then at least it wont be too much of a disaster if i dont quite get / choose the right pair of drivers.

My next question would be...does it really matter if you get 8 ohm or 16 ohm units? Can both be made to work equally well?

Thanks and lookin forward to further illumination in what seems to me to be such a fascinating subject!

Cheers

mark

Tim Moorman 16th July 2004 03:54 AM

Horns
 
markzb,

The driver impedance is not really significant if tube amps are used. They usually play well into the higher 16 ohm loads if the load is benign (without radical shifts up and down), and the output transformer has taps for the load.

When paralleling two drivers like bass woofers, the 16 ohm each nets an 8 ohm load and can be beneficial with solid state amps.

If wiring up a crossover, the higher 16 ohm driver impedance on a single unit will require more costly components due to the higher values needed to crossover at the same frequency vs an 8 ohm driver.

The P Audio stuff does look good, but I've only heard an 18" woofer of theirs - no compression drivers. The woofer was in a well designed bass horn sub and sounded good, but horn mounting is the least stressfull, lowest distortion method of useage and should sound good. High excursion and compression are virtually eliminated, distortion kept to a minimum.

Tim

markzb 16th July 2004 01:58 PM

Tim

Many thanks for your advice. You sure seem to know lots about this horn and jbl stuff!

My next question, If I may ask you kindly Tim, concerns the frequency of coverage of our horn, or more correctly the lack of it further down.

From what I have read about these compression drivers is that they go down to the region of about 800 to 500 Hz.

Now, I love the sound of Baroque instruments. And of these instruments, quite a few go down below this region. The oboe for example goes down apparently to 250 Hz.

So.....what would you say is the best approach to take of where our midrange horn aboves starts to fall off?

Pardon my ignorance, but for deep bass and some high energy jazz and just generally cranking the volume up, I would imagine you would want to use say a 15" driver.

But surely such a driver would not match the midrange horn and compression driver we would be using.

Or am I wrong? Perhaps you just need to put a horn in front of that 15" driver and that matches our midrange horn and compression driver well enough.

I hope my question is coming out clearly! How do we bridge the gap? Is there even one to bridge?

Regards

mark

vuki 16th July 2004 08:32 PM

How about Ebay? In last 12 months I managed to buy nice set of Altec high frequency drivers/horns and bass drivers for a pair of 2way speakers for <$1000. :D
It's not really "cash & carry" operation, but it's well worth the effort. Shipping to Malaysia via USPS surface mail isn't so expensive...

hunter audio 17th July 2004 06:54 AM

hi

ref P - Audio versus JBL , most of the P-Audio standard size compression are modelled on the JBL

but here is the problem

the Titanium used by Jbl is - approx 1 mil thick (size in inches)

the Titanium used by P-audio is approx 4 mil thick (inches)

rest of it is more or less cloned - (i also have doubts of the quality of steel used by P - audio to JBL )

well with this thicker diaphragm they sound no where near the JBL s

if you are facing budgetry problems - a Selnium is better in this respect

you could also go in for Fostex - since its a Japanese co. it may be available easily in Austarlia - and are extremely good - balanced and smooth

and they have 2 very good super tweeter bullets

suranjan

transducer design engineer

Tim Moorman 17th July 2004 12:12 PM

Horns and Woofs
 
markzb,

My preference is to use a midbass horn followed by the mid/hf horns. The system then becomes very large, complicated, and is difficult to implement. But it will yield fabulous sound if done properly.

Always a problem getting cones to match up well with horns, but not impossible. The best advice is to use woofers and crossover points to match up well with the pattern control of the horn at the crossover frequency, and try to use woofers of very high efficiency.

I look at the bass reproduction as a necessary part of good sound but also as a way to muddy up the midbass if not done well. Usually, if a large driver is producing 30 Hz, you are going to be asking for IM distortion and other problems if the same unit has bandwidth into the mids and upper mids, like 1500 Hz - 2K Hz. So limit bass woofers to bass and don't run them up high.

Though it makes for more expense, use (2) 15" bass woofers, like the JBL 2226, followed by a 10", like the now obsolete JBL 2123 mid, or 12" like the 2204 midbass, followed by your 1" or 2" mid/high frequency horn. Look at TAD 2001, the JBL 2404, 2425 in 1" drivers, even the Altec MR902, plus all the other suggested companies. Crossover points at around 250 Hz and 1250 Hz, or use 100 Hz if a sub amp/ crossover is preferred, and the mid driver will cover the lower range to 100 Hz.

You can horn load the midbass later if you so desire, but I wouldn't be to anxious to run a 2" mid compression driver really low, like 350 Hz or something, because they will sound pretty bad, and have no power handling near resonance. Takes a large horn as well. You can go to 500 Hz with a 2440//2441, but you won't gain much.

I would buy used drivers from a reputable source like a pro sound shop that can actually check them out. Ebay is trouble, unless you can get a guarantee of some kind. Good stuff can always be resold.

My guess would be $250 each for the bass woofers used, $200 each for midbass, $250 - $450 mid/high driver, and $150 for the horn. Boxes, crossovers, and amps are all additional.
You will need to consider the cost and difficulty carefully.

Also, nothing says that you can't start out as a simple two way, just like the vintage systems, and run the 15s up to the horn at 1000 Hz or close. I'd start with the bass first, though, and do it right. Then just add to the other system components as you get the urge, or the funds.

Good Luck.

Tim


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