Page 1 of 4 123 ... LastLast
Results 1 to 15 of 51

Thread: Help in adding tweeter to horn speakers

  1. #1
    Senior Member
    Join Date
    Feb 2004
    Location
    Land of Sunshine
    Posts
    423

    Help in adding tweeter to horn speakers

    Hi,

    I've seen people adding JBL hi freq driver (2402, 2405 etc.) to horn speakers by connecting a capacitor in series to the +ve terminal of the driver.

    May I know:

    1. Whether the capacitor in series is performing the freq cut off function

    2. If so, may I know the value of the capacitors to achieve 18 khz, 20khz and 22 khz crossover respectively?

    Thanks.

  2. #2
    RIP 2009
    Join Date
    Feb 2004
    Location
    Rohnert Park, CA
    Posts
    3,785
    Why such a high frequency? The 2402 is virtually useless above 18K, and the 2405 barely...

    John

  3. #3
    Senior Member Don Mascali's Avatar
    Join Date
    Sep 2004
    Location
    Sarasota, Florida
    Posts
    494
    I use 2344A horns and 2426H drivers for HF and have added a 2404 UHF with a 2.2 mfd cap in series. JBL says the minimum impedance for these is 7.2 ohms. I'm not sure what the formulas say as to the "correct" value, but I've tried several values and these sound the best to me.

    I like the gradual (6db/octave) roll off as it seems to work well with my horns. I actively cross all of the other points so I don't have the HF roll off compensation for the 2344A/2426H combination which the guys have written tons about in the 4430 thread.

    Good luck,
    Don M
    4406, 4412A, L100, L100t3 (3 pair), L1, L7, 4645C, 4660A, 4695B, SR4735 and various DIY JBL Pro loaded systems.

  4. #4
    Administrator Mr. Widget's Avatar
    Join Date
    Apr 2003
    Location
    San Francisco
    Posts
    9,719
    Quote Originally Posted by ngccglp
    May I know:

    1. Whether the capacitor in series is performing the freq cut off function

    2. If so, may I know the value of the capacitors to achieve 18 khz, 20khz and 22 khz crossover respectively?
    It isn't quite that simple. I single capacitor in series with a speaker will provide a first order cut off... that means you will get a 6dB per octave roll off with the -3dB point typically considered it's cutoff frequency. To determine the value of capacitor for a given frequency you will need to know the impedance of the speaker (any type including horn tweeters) and refer to a chart or get the formula... do a google search there are dozens of places to find this info.

    Off the top of my head here is an example. For an 8 ohm speaker a 4 uF cap will give you a -3dB point of 5KHz, 2 uF will be 10KHz, 1 uF will be 20KHz.

    A first order crossover has such a gentle slope that even the 1uF cap will allow a significant amount of acoustic energy be produced by a tweeter that only has a response to 20KHz.

    In answer to the second half of your question, obviously all three values would be around 1 uF but I am confident you won't hear a difference between these three values... certainly not at those frequencies.

    It is convenient to talk about these networks as blocking the lows or cutting off low frequencies, but in reality it isn't that simple. If you really want to study the matter you will discover that different order crossovers have different effects of the phase of the drivers, and will affect their polar plots, and will have differing amounts of driver interaction.

    Widget

  5. #5
    Senior Member frank23's Avatar
    Join Date
    May 2005
    Location
    The Netherlands
    Posts
    356
    it is of course more complex than simply adding a capacitor in series

    but if you want to do it the simple way you have to consider 2 things:
    - cross over at least 1 octave from the impedance peak caused by resonance
    - match the sound level by adding a resistor deviding network between capacitor and driver

    if this simple method is performed right, it can be quite effective, especially because your ears are a lot less sensitive at 15kHz than at 1.5kHz, so any errors are not so prominent

    greetings, Frank

  6. #6
    Senior Member
    Join Date
    Feb 2004
    Location
    Land of Sunshine
    Posts
    423
    Thanks guys.

    My Altec A7 mid and bass drivers are all 8 ohms, but the tweeter is 16 ohms, can I still use the tweeter or must I really change the diaphragm to a 8 ohm?

  7. #7
    Administrator Mr. Widget's Avatar
    Join Date
    Apr 2003
    Location
    San Francisco
    Posts
    9,719
    The name plate may say 16 ohms but it is quite possible that at the crossover region the driver isn't actually 16 ohms... in any case it's impedance relative to the other drivers is immaterial. It's impedance must be taken into account in regards to designing it's high pass filter. (Choosing a cap in this case.)

    Widget

  8. #8
    Senior Member
    Join Date
    Feb 2004
    Location
    Land of Sunshine
    Posts
    423
    Thanks Widget,

    You are spot on, the value of the capacitor used by my friend is 1 uF.

    Any idea what value of the capacitor I should use if the driver is 16 ohms. I've been hunting around, so far can only find 2405 that are 16 ohms.

    Thanks.

  9. #9
    Senior Member spkrman57's Avatar
    Join Date
    Feb 2005
    Location
    Columbus, Ohio
    Posts
    2,018

    For 16 ohm tweeter use...

    Try a .47 ufd cap.

    ROn

  10. #10
    Administrator Mr. Widget's Avatar
    Join Date
    Apr 2003
    Location
    San Francisco
    Posts
    9,719

    Ah, the 2405

    One of the frequently corrected JBL facts is that all 077s and 2405 have the same impedance and use the exact same diaphragm regardless of the rating on the foilcal. Actually as you will see from my plot they do vary, but it isn't due to the name on the back, it has to due with winding tolerances and the loading of the horn. In any event here is a plot of the impedance curve of four samples of JBL Slot tweeters. Two were 077 and two were 2405. As you can see they vary a bit. For your purposes I'd go under the assumption that they are 10 ohms. I think 1uF will be a fine starting point. There is no harm in messing around with other values. I wouldn't use a first order network on these for pro sound, but for home use, to misquote JBL you will experience discomfort before the tweeter does.

    Widget
    Attached Images Attached Images  

  11. #11
    Senior Member
    Join Date
    Feb 2004
    Location
    Land of Sunshine
    Posts
    423
    Thanks guys.

    I borrowed my friend's 8 ohm 2403 to try and with 1uF cap in series, the sound seems just about right to me.

    Will the 16 ohm 2405 driver sound twice as loud as the 8 ohm driver? I intend to only connect 1 uF cap in series to the driver.

  12. #12
    RIP 2009
    Join Date
    Feb 2004
    Location
    Rohnert Park, CA
    Posts
    3,785
    Quote Originally Posted by ngccglp
    Will the 16 ohm 2405 driver sound twice as loud as the 8 ohm driver? I intend to only connect 1 uF cap in series to the driver.
    What Widget was trying to point out is that ALL 2405's ahould be considered 8 ohms, regardless of what they say - they're the same diaphragm.

    John

  13. #13
    Administrator Mr. Widget's Avatar
    Join Date
    Apr 2003
    Location
    San Francisco
    Posts
    9,719
    Well sort of... I was saying that in fact they should all be considered 10 ohms.

    But yes, we have gone on and on about this, I personally have posted it too many times, but there are several vintage JBL products where the actual impedance was somewhere between 8 ohms and 16 ohms and the labels on them seemed to change with the times... i.e. when 16 ohms was popular they were rated as 16 ohms, and later when 8 ohms was more popular they changed the rating... only the rating... the devices were not changed.

    Therefore the LE15A, LE85, 077, 2405, 075, 2402 and a few others are all the same whether it states 8 ohm or 16 ohm. I am not saying that the LE15A has the same impedance as the LE85, but rather all LE85s have the same impedance even though older ones say 16 ohms and newer ones say 8 ohms.

    Clear as mud?

    Widget

  14. #14
    Senior Member edgewound's Avatar
    Join Date
    Jun 2005
    Location
    Southern California
    Posts
    2,776
    Another approach would be to measure the DC resistance of the voice coil to make sure it's in the same neighborhood as the nominal impedance printed on the label. 077, 076, 2403,2405, 075, 2402, 2404H-1 can all be fitted with either D8R075, D16R076 or D16R2405 diaphragms...all annular ring radiator types. Usually, a crossover network design program will ask for the DCR and Inductance of the voice coil, and also ask what type of filter you want to use...Butterworth, Bessel, Chebychev, Linkwitz-Riley....


    Maybe that'll muck up the mud some more for you, maybe it will help

    Good Luck

    Edgewound

  15. #15
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,963
    Quote Originally Posted by edgewound
    077, 076, 2403,2405, 075, 2402, 2404H-1 can all be fitted with either D8R075, D16R076 or D16R2405 diaphragms...all annular ring radiator types.
    With respect to mechanical fit and impedance, yes.

    That is not to say they are the same in all other respects, tho, just so nobody is misled in that regard.

    Edge: What's the difference between 2404H, 2404H-1, and 2404H-2?

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. adding a tweeter to Altec Valencia's.
    By bottleneck in forum Lansing Product Technical Help
    Replies: 14
    Last Post: 09-08-2005, 03:35 AM
  2. Adding a Super tweeter to 4430's
    By pelly3s in forum Lansing Product General Information
    Replies: 21
    Last Post: 03-16-2005, 05:53 PM
  3. Adding a tweeter to Altecs
    By rloggie in forum Lansing Product General Information
    Replies: 17
    Last Post: 12-30-2004, 10:14 PM
  4. List of JBL info
    By Donald in forum Lansing Product General Information
    Replies: 3
    Last Post: 10-27-2004, 04:17 AM
  5. Help... Olsen horn tweeter needed (vintage)
    By GordonW in forum General Audio Discussion
    Replies: 3
    Last Post: 02-23-2004, 02:45 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •