Setting up 3 way JBL horns for correct polarity

[Doogster]

Hi chaps

I had a 2 way JBL horn system which I've now expanded to 3 way. It now sound way better (I had some sort of peaking/beaming with the 2 way, but the new setup has cured this). However, I'm a tad confused as to exactly how to wire it all up. Here are the gory details:

Bass - JBL 2235 15 inch woofer in 5 cu ft reflex box.
Midrange - JBL 2441 (aka 376) on 350Hz tractrix horn.
Highs - JBL 2404H tweeter.

Crossover is a 12db passive line level LCR design for bass (low pass) and midrange (band pass). XO for the tweeter is just a 3.3uF cap in series with the tweeter.

Crossover -3db points are 700Hz and 5kHz.

Amps are a huge mofo Perreaux SS for the bass, a 45 SET for the midrange, and a crappy receiver for the highs.

I'm confused about which polarity to use for each driver. Does a 12db PLLXO do anything to the signal that requires phase reversal of some of the drivers at any point? What about the tweeter? Is there an easy way to determine the polarity of the midrange driver and tweeter (it's easy with the woofer)?

Cheers. Doug

[Zilch]

You haven't mentioned the most significant variable, the vertical alignment of the acoustic centers of the drivers.

Assume it's the voice coils, as indicated by the front plates of the drivers.

The optimal phase is largely dependent upon the depth of your midrange horn....

Do you have an RTA?

[Doogster]

You haven't mentioned the most significant variable, the vertical alignment of the acoustic centers of the drivers.

Assume it's the voice coils, as indicated by the front plates of the drivers.

The optimal phase is largely dependent upon the depth of your midrange horn....

Do you have an RTA?

Hi Zilch

I intend aligning all three drivers so their voice coils/diaphragms are in line - I am still experimenting with this aspect of things at the moment.

Unfortunately I do not have an RTA. I only have a Rat Shack SPL meter which I understand is somewhat inaccurate.

Can you recommend an RTA-less way of aligning horns?

Cheers. Doug

[Zilch]

Can you recommend an RTA-less way of aligning horns?An alternative "listening" method is described in the 5235 crossover manual.

[sourceoneaudio]

Doogster (http://www.audioheritage.org/vbulletin/member.php?u=496)
Where are you pulling the signal for the tweeter from? If you are running a band pass on the mid you can't pull it from there. The signal would have to come directly from the input so you are getting all HF information. If you are running a 12db per octave x-over on the mid, and 12db on the LF the general rule is to run the mid or next 12db network out of phase. I have discussed this with other members on the forum, and pulled the information from my RTTI training manuals. The final result with no RTA is your ear.. If your amp is not stable to low loads just be careful of impedance dips, so as not to damage the amp. I don't think I would worry about the tweeter to much @ 6db per octave, until you upgrade the network to a 12 or 18 slope, 12 to keep it matched is the way I would go.


J/S-S1A :blink:

[Doogster]

Doogster (http://www.audioheritage.org/vbulletin/member.php?u=496)
Where are you pulling the signal for the tweeter from? If you are running a band pass on the mid you can't pull it from there. The signal would have to come directly from the input so you are getting all HF information.

Hi

Thanks for your reply. I am taking the signal for the tweeter straight from a separate power amp. The only thing in between the amp and the tweeter is a cap that introduces a 6db XO at around 5kHz.

Do you think a 6db slope is not steep enough for the tweeter? I intend building a dedicated tweeter amp (tube of course) that has very little output above, say, 1kHz. If that's the case, can I still get away with a 6db XO for the tweeter?

Cheers. Doug

[sourceoneaudio]

Doogster (http://www.audioheritage.org/vbulletin/member.php?u=496)
Hello, I would go no less than a 12db network. It is much safer and you'll end up with less garbage getting passed through to the driver. (cleaner sound reproduction) 6db networks can tend to be harsh.

Here is some parts and a schematic for you
Get your part from www.partsexpress.com (http://www.partsexpress.com)

Second Order Butterworth Alignment
C1= 2.81uf Parts Express PN. 027-416 2.7uf & 027-400 .10uf This will = 2.8 uf
L1= 0.36 mH Parts Express PN. 255-030 .35 mH

L-Pad (100 watt) if needed (if the tweet horn is to bright) 260-265

The caps recommended are Metallized Polypropylene, good quality, and the coils are 20 gauge air core. They have other caps better quality but cost tends to go up qwik. I use these caps, and I'm very happy with the quality and sound reproduction that comes out of them.
Make sure to order you free catalog when placing your order.

[Earl K]

Hi,


I'm confused about which polarity to use for each driver. Does a 12db PLLXO do anything to the signal that requires phase reversal of some of the drivers at any point?

Yes,
- Flip the polarity of the horn driver ( as compared to the woofer ).
- Do the preceeding only if you indeed have a 12 db PLLXO filter that is properly performing the crossover functions that you've described ( have you measured this PLLXO crossover to check its' performance ? ) .

FWIW :
- An analog filter will always produce the expected phase shifts ( if built properly ) whether the filter is acting at microphone , line or speaker level .

- The phase shifts are fully realized over in the "stopband" / not the "passband"( which is the one typically listened to ) . The transitional area between these 2 areas happens to be called the crossover region . In the "passband" ( a good 1.5 - 2 octaves away from the crossover point ) the phase shift is very negligible.



What about the tweeter? Is there an easy way to determine the polarity of the midrange driver and tweeter (it's easy with the woofer)?

- There's really no easy way to determine a tweeters' best fit / without some reasonably good measuring equipment ( ones' ears may qualify ) .

I've heard this method recommended ( but never tried it ) .
(i) Use an FM Tuner as a Noise Source by "tuning off station". The resulting noise is White Noise ( or Pink , I forget which it is ).
(ii) Run this noise source into both the tweeter & horn circuit.
- Start with tweeter having the same polarity as the woofer .
(iii) While listening to this noise source, flip polarity of the tweeter back & forth.
(iv) Use whatever polarity gives you the fullest "perceived" sonic signature in the crossover area .

Hint ; It's also been recommended that one can use a 18" by 18" ( or 2' by 2' ) piece of cardboard to create a sort of a mobile barrier ( planar horn surface ). Place this barrier ( in a vertical orientation ) just to the side of the tweeter & the horn bell, to help "unify" the sound of the two outputs. Play with the degree of "tilt" from being fully perpendicular ( cardboard edge towards your ear ) to 45° to 60° away from your ear ).


Crossover is a 12db passive line level LCR design for bass (low pass) and midrange (band pass). XO for the tweeter is just a 3.3uF cap in series with the tweeter.

- Your words imply that you have an inductor within your LCR type PLLXO. That means the inductor has to be a very large value ( in the "full" Henry range / as opposed to milliHenry ). I'm assuming the inductor is a potted ferrite core type / such as Marchand Electronics uses. Is this assumption correct ?
- Perhaps, you should publish some details about your PLLXO crossover ( ie; is it of your own design ? / or someone elses ? )
- What are the component values for this PLLXO ? .



:)

[sourceoneaudio]

Hi,



Yes,
- Flip the polarity of the horn driver ( as compared to the woofer ).
.



:)

And yes this is mentioned in my schematic calculation, sorry I forgot to mention it. Kinda of important. Pretty sure I mentioned it b4 though in above thread. Good luck and let us know how it sounds when completed.

J/S-S1A :blink:

[toddalin]

The easy way using your existing equipment is to simply play a tone at/near the crossover frequency and use your RS meter to determine which polarity on the horn produces the smoother curve (typically the louder volume). Then do the same for the tweeter.

Test tones can be from any available source such as an oscillator, computer, CD, or a musical keyboard.

[Doogster]

Hi,

- Do the preceeding only if you indeed have a 12 db PLLXO filter that is properly performing the crossover functions that you've described ( have you measured this PLLXO crossover to check its' performance ? ) .

- Your words imply that you have an inductor within your LCR type PLLXO. That means the inductor has to be a very large value ( in the "full" Henry range / as opposed to milliHenry ). I'm assuming the inductor is a potted ferrite core type / such as Marchand Electronics uses. Is this asumption correct ?
- Perhaps, you should publish some details about your PLLXO crossover ( ie; is it of your own design ? / or someone elses ? )
- What are the component values for this PLLXO ? .

:)

Thanks for your reply Earl

In answer to your questions - yes, I have measured the PLLXO on my scope with dummy loads. It measures exactly how I intended it to (with a lot of tweaking!).

Yes, I am using large value pot core inductores, a la Marchand. I used John Broskie's Glassware Filter Designer to get the basic values. I was limited by the inductors I had on hand (I have about 50 different types I got from a salvaged ex-telecommunications filter unit). I then tweaked the design for the real world using my scope and a signal generator.

Values are as follows:

Bass low pass - 710mH and 0.2uF cap, terminated with 2k resistor.

Mid band pass - 230mH and 0.1uf cap (high pass) / 130mH and 0.0068uF cap (low pass), terminated with 2k resistor.

I only use a cap at speaker level for the tweeter. However, based on advice from others on this forum I will experiment with another PLLXO section for the tweeter.

Regards. Doug

[Earl K]

In answer to your questions - yes, I have measured the PLLXO on my scope with dummy loads. It measures exactly how I intended it to (with a lot of tweaking!).

Okay, that's great .


Yes, I am using large value pot core inductores, a la Marchand. I used John Broskie's Glassware Filter Designer to get the basic values. I was limited by the inductors I had on hand (I have about 50 different types I got from a salvaged ex-telecommunications filter unit). I then tweaked the design for the real world using my scope and a signal generator.

Good stuff / sounds like I need to get out and do a bit more dumpster diving .

- Do your inductors look like the type that Marchand sells with their XM-46 kit ?
- Not that I've mounted an exhaustive search for those things / but up here in Toronto, I've never seen them for sale at my standard suppliers .



Values are as follows:

Bass low pass - 710mH and 0.2uF cap, terminated with 2k resistor.

Mid band pass - 230mH and 0.1uf cap (high pass) / 130mH and 0.0068uF cap (low pass), terminated with 2k resistor.

- What's the input impedance of your referenced amps ( Perreaux & Set45 ) ?
( Off-hand , I don't understand the values that you've used to arrive at your goal / but then , these things are pretty finicky)


I only use a cap at speaker level for the tweeter. However, based on advice from others on this forum I will experiment with another PLLXO section for the tweeter.

- The last time that I listened to a 2404h, I concluded that it was best crossed into somewhere past the 7 to 9 Khz area. ( Widget/Zilch did do a nice study on JBL tweeters, that's somewhere in the archives ). The "FR" curves that they ran pretty well sum up why these things sound nicer when they're crossed over higher up. This "complication" would of course require a reworking of your bandpass filter. Oh well . :o:

:)

[Doogster]

- Do your inductors look like the type that Marchand sells with their XM-46 kit ?

- What's the input impedance of your referenced amps ( Perreaux & Set45 ) ?
( Off-hand , I don't understand the values that you've used to arrive at your goal / but then , these things are pretty finicky)

- The last time that I listened to a 2404h, I concluded that it was best crossed into somewhere past the 7 to 9 Khz area. ( Widget/Zilch did do a nice study on JBL tweeters, that's somewhere in the archives ). The "FR" curves that they ran pretty well sum up why these things sound nicer when they're crossed over higher up. This "complication" would of course require a reworking of your bandpass filter. Oh well . :o:

:)

Earl

Yes, my inductors look just like the Marchand jobbies.

The input impedance of both amps is 100K.

You are right - the PLLXO values I've used are not textbook. They do deviate a little from what the formulae say. However, they have been thoroughly measured so I don't doubt their accuracy.

I'll bear your suggestions on the 2404s in mind. I wanted to cross over at 5kHz because I had some peaks in the 2441 around 5kHz which I wanted to cure by crossing over where I did (that's probably not the best reason to cross over, is it!). Ideally I would have crossed the 2404s in at 7 to 10kHz and implemented a notch filter in the 2441. Or maybe the peaking I experienced with the 2441 was because I was running it without a tweeter (ie. from 700Hz all the way up to where-ever). I went with a PLLXO to simplify things. A 3 way PLLXO with PLLXO notch filter is going to take up a lot of real estate.

Do you think a 6db XO at 5kHz for the 2404 is OK, or should I use 12db as others have suggested?

Cheers. Doug

[sourceoneaudio]

Using a 6db :barf: network, and if you had a way to measure it via pink noise you will see all kinds of issues at the x-over point, not a sharp enough slope. Kind of like cutting a fine cheese with a butter knife, not clean, and all kinds of S&%^ sticks to the blade. Trust me you will be very satisfied wit the out come. Much smoother and a better transition from driver to driver. Plus if your any kind of a high volume listener it is very unsafe, you will either blow up the caps or the driver which ever decides to fail first. Good luck.

J/S-S1A :blink:

[Earl K]

Hi There,

The input impedance of both amps is 100K.

- A 2K terminaton ( load ) resistor ( 1% tolerance, I'm assuming ) across a 100K load ( unbalanced ) , gives a new working load impedance of @ 1960.8 ohms .

Values are as follows:

Bass low pass - 710mH and 0.2uF cap, terminated with 2k resistor.

(A) Thanks for that ! I would have expected that the usable range of cap values would be ; .082 to .066 uF, used with a 710mH coil ( to give an @ F3 of 700 hz ) .

(B) Running the numbers for the individual elements within your low pass filter gives individual F3(s) of @ 440 hz ( coil ) & 406 hz ( cap ) .

- With these 2 F3(s) so closely stacked on top of each other / I would have expected that you would be measuring some significant peaking ( high Q resonance ) in this FR area before actual attenuation takes palce .

(C) Bear with me here while I run through some math & buildup procedures .

(i) Since the 710 mH coil is your given.

- I would first test the accuracy of two assumptions. These are the net load impedance and the real value of the 710mH coil. I would do this by measuring for the F3 point of a single inline coil ( in this case, 710 mH ). The reference voltage would be set a good two octaves away ( in the passband ) from the expected area of the attenuation . 100 hz fits this criteria .
- eg. Use a 1 volt reference set to 100 hz. Sweep up in frequency till voltage drops to .707 volts when measured across the net load ( 2K resistor in place ). This voltage drop equates to the 3 db down point.

- Assuming all is well ( with the assumed load impedances and coil value ) , then an @ F3 right around 440hz ought to be measurable.

Some Math :
(ii) I'm going to play around with math that uses reciprocals, so ;
- 700 hz divided by 440 hz ( the first given pole in the filter ) gives 1.59 .
- Its' reciprocal is .62857 ( or .63 if you prefer ) .
- 1.6 ( I rounded up ) times 700hz is 1120 hz. This is the frequency where the second poles' theoretical F3 should occur ( when measured separately ).
- .625 times 700hz is 437.5 ( this closely approximates the F3 point of our 710mH coil working into a 1961 ohm load )

NUMBER CHECK:
- 1120 times 437.5 = 490000 . The square root of 490000 hz is 700 .
- For those who don't realize it, taking the square root of the product of the individual F3(s) , ( stated in hertz ) will give the F3 point of any 2-pole filter from this class. Since 2-Pole ; LR, Bessel & Butterworth filters are all derived from reciprocals they all fit this classification.

Reciprocals Used in calcs for some Common 2-Pole Filter Types :
- The respective ( rounded ) reciprocal #s are ;
Bessel at 1.74 & .57
Butterworth at 1.41 & .71
LR at 2.0 & .5
- Ours' is going to be ; 1.6 & .625

(iii)
- One can utilize our new " weighting numbers" ( ie; 1.6 & .625 ) to derive the filters' coil & cap values .
- One can see that the resulting filter will have a transform that is somewhere in between that of a 2 pole Bessel and that of a 2 pole Butterworth filter .

(iv) Using 1.6 & .625 as our weighting ( multiplier ) numbers ( when plugged into standard formulas for deriving coil & cap values for an F3 at 700 hz ) result in component values of, 713.3mH & .0725 uF ( respectively ) .

Sorry if I bored you with this exercise in derived math / but / math doesn't lie ( though in this case its' practitioner could always be missing a relevant formula / or missing information that will skew realworld results ).


You are right - the PLLXO values I've used are not textbook. They do deviate a little from what the formulae say. However, they have been thoroughly measured so I don't doubt their accuracy.

- I am wondering outloud about those working values in your PLLXO and how they're able to work for you / though I've only looked at the lowpass circuit for the woofer.

- I'll always defer to accurate measurements.

:)

[Earl K]

Do you think a 6db XO at 5kHz for the 2404 is OK, or should I use 12db as others have suggested?

If it was my project ( & because I like large format drivers on round horns ) ,
- I would run the 2441s all the up to a fairly linear point ( say 10 to 12K ) on that horn . I would do this even if it meant the creation of a HF compensation circuit ( hopefully not needed ) and the insertion of a series LCR notch filter strapped across the driver.
- I'd also first try out a gentler slope in lowpass section of the bandpass on the midrange horn ( I'd attempt to add the natural 6 db acoustic rolloff in the HF to the 6 db electrical rolloff ).
- Note: To be able to use a ( Speaker Level ) LCR you would need to add a 12 to 16 ohm inline resistor so that the LCR notch could actually resonate & then attenuate .

- Then I would cross the 2404 in with a 3 or 4 pole ( speaker level ) circuit . I would create either a classic 3 or 4 pole filter. Or maybe 3 pole "bump filter" which has a bit of EQ in it ( resonant bump filter ). JBL has shown the way in how they used to employ these resonant filters on UHF devices within their "Legacy" 43xx ( big box ) products.





:)

[Doogster]

If it was my project ( & because I like large format drivers on round horns ) ,
- I would run the 2441s all the up to a fairly linear point ( say 10 to 12K ) on that horn . I would do this even if it meant the creation of a HF compensation circuit ( hopefully not needed ) and the insertion of a series LCR notch filter strapped across the driver.
- I'd also first try out a gentler slope in lowpass section of the bandpass on the midrange horn ( I'd attempt to add the natural 6 db acoustic rolloff in the HF to the 6 db electrical rolloff ).
- Note: To be able to use a ( Speaker Level ) LCR you would need to add a 12 to 16 ohm inline resistor so that the LCR notch could actually resonate & then attenuate .

- Then I would cross the 2404 in with a 3 or 4 pole ( speaker level ) circuit . I would create either a classic 3 or 4 pole filter. Or maybe 3 pole "bump filter" which has a bit of EQ in it ( resonant bump filter ). JBL has shown the way in how they used to employ these resonant filters on UHF devices within their "Legacy" 43xx ( big box ) products.

:)

Hey Earl

Just thought I'd touch base with you. I finally have the 3 way PLLXO set up (I even made up a proper chassis for it). Everything sounds very balanced - certainly a lot better than it was. After some tweaking I will try out your suggestions.

However, there is one nagging thing - the 2404H tweeter. It is very hissy. So much so that it is distracting. It doesn't matter what amp I use. Is this normal for this tweeter? Any suggestions for how to tame the hiss?

Cheers. Doug

[Earl K]

Hi Doug,

Nice Work !

As far as I know , you're the first poster here at LHF, to design & construct his own full blown PLLXO setup ( 2 or 3 way ) . So, Congratulations !


However, there is one nagging thing - the 2404H tweeter. It is very hissy. So much so that it is distracting. It doesn't matter what amp I use. Is this normal for this tweeter? Any suggestions for how to tame the hiss?

- The above text is a little vague for a proper response !

- Do you mean the tweeter circuit is annoyingly hissy / without program ( music ) playing ? If so, look to your electronics ( gain of preamp / amps / as the culprit(s) )

------------------------------------------/ or /

- Do you mean that the tweeter is hissy when music is playing through it ?

--------------------------------------/ If so then : /

- Just what are the LCR values in this tweeters' PLLXO ?

- What gain setting are your amps set to ?

- A Hunch ( based on your other PLLXO values ) : You may have made this ring radiator device ( which is IMO, already overly resonant below 10K ) , even more resonant by building a PLLXO that could be ringing ( if its' multipole filters are mathematically to close to each other ) .

- IME ; all JBLs' ring radiator type tweeters suffer from this characteristic of being overly resonant below 10K. That is the most significant reason I can think of, to severely limit their response curve to above 10K.
- ( IME: 5K to 10K is an extremely sensitive area for the ear when it encounters undue resonance ; ie , one wants a device with well behaved damping reproducing this range . )

- The solution ? Cross above 9 or 10K. Or to maintain a 5 K point,( & it's conjecture only ) eBay a pair of 2407 drivers / then mount them into some tiny wavequides ( or even just parallel slots, a la Smith Horn tweeter ) and then enjoy the sound of damped Mylar .

:)

EDIT: ( added sometime later )


- The hiss problem could also be a bad FR curve .
- What does the response curve look like ( for just your tweeter setup ) ?
- Here's one FR plot ( done by Mr. Widget ) of both the 2404 and 2404-1 tweets. IME ; this is not a listenable curve .
http://audioheritage.csdco.com/vbulletin/attachment.php?attachmentid=8617&stc=1&d=1119511300
- Depending on what sort of response you're now getting, you may want to try some extra, HP filtering on those 2404H(s) . I just did that with the single 2404H that's here. The filtering was at speaker level & only single pole .
- It wasn't until I got the cap size down to about a .1uF cap that I thought what was coming out of the tweeter was worth keeping around ( & blending into the overall ) .
- This was done by simply listening to only the tweeter .
- This simplistic approach was also done with a Fostex N945 ( a bullet style tweet ).
- I do believe that each range should be listenable in it's own right before being allowed to contribute to the overall .
- Whether or not there's enough level to work with, is beside the point . It's the EQ contour ( at this point ) that's most important at the starting point .
- That's why I've tried to get across a multipole ( 3 or more ) filter keeping the most audible portion of the passband, to over 9 or 10K , is the best way to use these things.
- Yes, with 2 uF inline with either of these 2 tweets ( my starting point in cap size ), everything coming out sounded like some form of distorted noise . And yes, lots of hiss .
- RTAing either of these tweets ( with the .1 uF ) inline cap showed an EQ contour that was : @ 3 db down at 5K, with a gentle upwards slope to 12K, & then a plus 4 db spike at 16K. Overall a pretty decent looking ( & sounding ) curve.
- Do the same exercise. Get a computer based, RTA measurement setup , if you don't already have one...

:p

[louped garouv]

However, there is one nagging thing - the 2404H tweeter. It is very hissy. So much so that it is distracting. It doesn't matter what amp I use. Is this normal for this tweeter? Any suggestions for how to tame the hiss?

Cheers. Doug


how much power are you feeding the 2404H in relation to the other drivers?

just out of curiosity....

[Robh3606]

However, there is one nagging thing - the 2404H tweeter. It is very hissy. So much so that it is distracting. It doesn't matter what amp I use. Is this normal for this tweeter? Any suggestions for how to tame the hiss?

How much attenuation do you have in line?? They are something like 110db @ 1 meter. If you don't have them padded down a bit I can see the hiss level from them being distracting.

Rob:)

[louped garouv]

How much attenuation do you have in line?? ...

If you don't have them padded down a bit I can see the hiss level from them being distracting.

Rob:)

generally and theoretically speaking, is it better to pad down via a circuit or reduce power being fed?

[Robh3606]

generally and theoretically speaking, is it better to pad down via a circuit or reduce power being fed?

That’s a really good question and I am not sure I can answer it. Any of you Professional Sound guys want to tackle this one??

Every thing has a residual noise floor. With no signal that is what you are hearing. The lower this is the better for obvious reasons. I try to use the multiple gain stages I have available to get the lowest noise floor I can buy manipulating the gain levels in the amps, crossovers and Eq’s. For us the S/N is probably the most important issue than maximum driver output. With professional SR they need Max Output with the best S/N they can manage.

One of the advantages of an active system is you don’t waste power in the passive networks. You use the gain structure in you crossover and amps to set the driver levels. The problem with this is any residual noise in the chain is not attenuated like it would be in a passive set up. You don’t loose power but you pick up noise for the trade. If you had a noisy 2404 you could drop in a 10Db passive attenuator providing you have the gain available to make it back up. But more gain equals more noise :banghead:

You have to balance this all out and see what works the best for you. Chances are you will end up better off with the passive attenuator in place but it all depends of how quiet the gain stages are. With my compression drivers I have to use passive compensation which helps knock the noise level down a bit. When seated I can’t hear the system on with a mean sensitivity of about 98-100db per watt. It was a real PITA to get it set-up this way. Without the passive compensation on the compression drivers I can hear the system.

Rob:)

[Doogster]

How much attenuation do you have in line?? They are something like 110db @ 1 meter. If you don't have them padded down a bit I can see the hiss level from them being distracting.

Rob:)

Rob

I am not padding them down at the moment. What would be a good value to try? I think I have some L-pads hanging around somewhere.....

Incidentally, today I replaced the 2404Hs with Fostex FT17H tweeters. The hiss has decreased dramatically, but then they are much less sensitive drivers. I actually prefer the sound of the Fostex drivers now that I've listened to both. The Fostex sound more mellow (yes, I have adjusted the levels for difference in sensitiviy) than the JBLs.

Cheers. Doug

[Doogster]

how much power are you feeding the 2404H in relation to the other drivers?

just out of curiosity....

Hi

I haven't measured what I'm giving them, but I have set the levels by ear to what I think sounds natural. I am using a 20 watt tube receiver at the moment (the other drivers are being driven with a 1 watt SET amp and 500W SS amp for the bass).

Cheers. Doug

[Doogster]

Hi Doug,

Nice Work !

As far as I know , you're the first poster here at LHF, to design & construct his own full blown PLLXO setup ( 2 or 3 way ) . So, Congratulations !

- Do you mean the tweeter circuit is annoyingly hissy / without program ( music ) playing ? If so, look to your electronics ( gain of preamp / amps / as the culprit(s) )

------------------------------------------/ or /

- Do you mean that the tweeter is hissy when music is playing through it ?

--------------------------------------/ If so then : /

- Just what are the LCR values in this tweeters' PLLXO ?

- What gain setting are your amps set to ?


Hi Earl

Thanks for your reply.

I might take a pic and post it if anyone's interested what it looks like.

The 2404 is hissy without anything playing. I think it's the whole replay chain that's less than pristine. I use a homebrew tube linestage, phono stage and power amp, all of which use AC on the heaters. It's the monstrously high sensitivity of the 2404s that's causing the problems.

See my post below to Rob - I have now replaced the 2404s with Fostex FT17H tweets, which are about 12 db less sensitive, and the problem has decreased dramatically (there is still some residual hiss, however). I would still like to experiment with the 2404s, but after attenuating them.

These JBL drivers are so sensitive I will have to restructure the gain of my preamp. I currently have all the amps set to very low gain because anything higher prevents me using my linestage properly (as it stands I can't turn the volume past about 8!).

Cheers. Doug

[louped garouv]

my master volume control pot rarely goes above "4"

;)

[Robh3606]

I am not padding them down at the moment. What would be a good value to try? I think I have some L-pads hanging around somewhere.....


I would drop them at least 10db, Try them attenuated to match the Fostex's.

Rob:)