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View Full Version : Using woofers without filtering.



beppe61
11-18-2006, 12:10 PM
Dear Sirs.

I understand that some JBL vintage monitors have no crossover on the woofers.
Like for instance my little L16.
I would like to get some opinion on this solution (pro and cons).
Moreover I would be very interisted to know which model of woofers in the JBL vintage production are suitable to be use without an inductance in series.
Which kind of properties they should have ?
I think that this solution can give a very transparent sound (no passive components between the woofer and the power stage).

Thank you very much indeed.
Kind regards,

beppe

morbo!
11-18-2006, 02:25 PM
I would start with foobar

http://www.foobar2000.org/

And it`s digital x-over

http://xover.sourceforge.net/

It`s all free and the learning curve isnt too step
if you never done this kind thing before

Not exactly what you were after but bi-amping kiks ass any day of the year

soundboy
11-18-2006, 05:44 PM
You could use a 4301B crossover.Just add the parts to the woofer side on the L16's....and re do the values on the tweeter....same drivers. The woofer filter was no doubt left out for cost reasons...the L16 was the low end of JBL (still better than some other's "high" end, I feel) Problem is, no crossover on the woofer means a lot of things, like listening to the usually large breakup peak at 2.5K or so....some worse than others. Personally, I would rather filter it out. My 4301's sound wonderful with claritycaps. They sounded great even stock, just a little too veiled without bypassing or replacing the caps. I have been looking for a set of L16's so I could do just that. The L19 is the same crossover save for a 18uf cap on the woofer shunt, as opposed to 16.5uf on the 4301. It's also electrolytic, where the 4301 is mylar. Most likely, my guess is that was the value that was cheapest by the lot...they are all built to a price point, otherwise they would have used the same in both speakers...
As for JBL vintage woofers that can be used without a crossover...well, all of them can...actually the caberet series did that a lot, same for a lot of the pro stuff....but it's a different animal with different intended use....in a home, it would tear your head of, from experience, I speak. I personally wouldn't use a 10" above 1200hz, a 12" above 800hz, and a 15" above 300-500hz, and an 18 above 80-125hz max....That's just me, because of the midband colorations for critical home use. This all moves up an octave for pro use...IMHO.
Anyway, with the relative low cost of excellent audio capacitors nowadays, a correctly designed passive is hard to beat. I use active in pro stuff, and in my sub at home....but they are used in regions where the driver's are smooth and pretty flat response wise. It's a bit of a job to use an active with all of the tweaks that were designed in a passive to smooth and flatten each driver so they blend correctly and seamlessly. Ok, I will shut up, this has all been talked about a ton on here. I surely would keep those little L16's, though, they are worth the trouble. The tweeter is actually nice with decent caps ahead of it, surprisingly so.:bouncy:
PS The L100 woofer rolls off pretty smooth. It doesn't have any filtering. It also fights with the midrange driver, causing all kinds of havoc...but it was designed that way...probably so we could all fight about it's merits 40 years later...but what fun it is...

beppe61
11-19-2006, 04:08 AM
Thank you very much Sirs for your kind and valuabble advices.


My real question is that if a woofer does not show any particular out-of-band peakes can it be used unfiltered ?

Its natural decay on higher frequencies could be "seen" as a let's say 6dB/octave filter ?

The positive part of this modification is that this could dispense with using an often critical inductor in series with it.
I read that inductors in series with woofers tend to slow them. The attack is less pronounced.
On the contrary I read that caps, if of high quality of course, are less detrimental to good sound.



Another example of use of an unfiltered woofer are the JBL 4312s.
From what I understand the 4312 have an extremely exciting, transparent and and "live" sound, something that I am missing now.


Of course the first step would be selection of the right woofers.


Thank you very much again.
Kind regards,

beppe

soundboy
11-19-2006, 10:20 AM
From what I have seen, the 123 type woofer does this well...same woofer as L100....but it is actually more like a 12 db rolloff after it peaks....most every woofer I know of, unless it is a poly cone, has a pretty good rise/break up before rolloff....they all get beamy above the point the soundwaves are longer than their width...for a 12 this is about 1200hz...many many speakers have been built over the years doing just what you are describing...but I feel they were out of cost considerations/lack of engineering/ in a lot of cases (cheap). The L100 did it purposely for a certain sound....and a lot of great rock and roll memories were created with that speaker. You just have to choose the right driver. Most of, if not all the pro JBL drivers I have used have a HUGE peak in the upper mids E140/145/130/120 etc...do a search and look at some graphs....great for bass guitar and crispness....but not my idea of transparent for audio reproduction, without a low pass filter...and the home drivers, unless coated with aquaplas, mostly exhibit the same..
As far as inductors "slowing things down"....not in my 30 years of experience. If you use good quality parts, any DC resistance can be figured in to your box tuning/size....again, do you want something shouting/honking at you when you are directly on axis, or do you want flat uncolored sound? Simple, really....good luck to you

beppe61
11-20-2006, 01:20 PM
From what I have seen, the 123 type woofer does this well...same woofer as L100....but it is actually more like a 12 db rolloff after it peaks....most every woofer I know of, unless it is a poly cone, has a pretty good rise/break up before rolloff....they all get beamy above the point the soundwaves are longer than their width...for a 12 this is about 1200hz...many many speakers have been built over the years doing just what you are describing...but I feel they were out of cost considerations/lack of engineering/ in a lot of cases (cheap).
The L100 did it purposely for a certain sound....and a lot of great rock and roll memories were created with that speaker. You just have to choose the right driver. Most of, if not all the pro JBL drivers I have used have a HUGE peak in the upper mids E140/145/130/120 etc...do a search and look at some graphs....great for bass guitar and crispness....but not my idea of transparent for audio reproduction, without a low pass filter...and the home drivers, unless coated with aquaplas, mostly exhibit the same..
As far as inductors "slowing things down"....not in my 30 years of experience.
If you use good quality parts, any DC resistance can be figured in to your box tuning/size....again, do you want something shouting/honking at you when you are directly on axis, or do you want flat uncolored sound? Simple, really....good luck to you

Thank you very much Sir for your advice.
Of course I would appreciate very much an flat uncolored sound, i.e. a realistic one.
I think that this is the true aim of high fidelity after all.
The use of an high quality inductor seems always mandatory then.
I clearly understand now that it is a really bad idea not using it.

Kind regards,

beppe