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Thread: "Coloration" of horns

  1. #46
    pangea
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    Hi Tim!

    Thanks for your input! Feels good to know it wont be impossible to get some phragms in the forseeable future.

    I noticed the JBL 3107 is for a 8 Ohm driver. Is there an easy way to convert the network to a 16 Ohm driver?

    OK, it seems I wont be able to go on building speakers without some special tools like the LspCAD, tone generator, mic, SPL meter and soforth. What about a scope, do I need one of those, or is that only to show off among my friends?

    Any particular types of equippment you could recommend?
    What to think about and what to avoid?
    What does the pink noice generator do, that a ordinary tone generator doesn't do?
    What's the differens between a SPL-meter and a dB-meter?

    BR
    Roland

  2. #47
    Administrator Mr. Widget's Avatar
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    Originally posted by pangea
    Hi Tim!

    Thanks for your input! Feels good to know it wont be impossible to get some phragms in the forseeable future.

    I noticed the JBL 3107 is for a 8 Ohm driver. Is there an easy way to convert the network to a 16 Ohm driver?

    OK, it seems I wont be able to go on building speakers without some special tools like the LspCAD, tone generator, mic, SPL meter and soforth. What about a scope, do I need one of those, or is that only to show off among my friends?

    Any particular types of equippment you could recommend?
    What to think about and what to avoid?
    What does the pink noice generator do, that a ordinary tone generator doesn't do?
    What's the differens between a SPL-meter and a dB-meter?

    BR
    Roland
    Hmmmmmm.

  3. #48
    pangea
    Guest
    I know, I'm sorry, but the questions never seem to end. They just keep on popping up from out of nowhere in my head.

    BR
    Roland

  4. #49
    TimG
    Guest
    The 3107 was designed for a 2440 (16ohm) midrange mounted on a 2311 horn with 2308 lens, a 2405 (16ohm) supertweeter and a 2202A or 2202H (8ohm) midwoofer. The 2440 was always a 16 ohm driver and according to Giskard the 2405 was always a 16 ohm product as well since only one type of diaphragm was ever made for it. It seems that all the 3107s are gone from the tent sale, they will probably show up next week on ebay at an inflated price. If you search the forum you should be able to find the updated schematic for the 3155 crossover that you can build yourself. It was discussed a few weeks ago. The 3155 is the crossover from the 4355 monitor. The crossover points are at 290, 1200, and 10kHz. http://www.jblpro.com/pub/obsolete/4355.pdf

    All you need to get started measuring speakers is the software, LspCAD and Soundeasy are the most popular, a soundcard that can be used in duplex mode (I just used the SB Live as an example) and a panasonic microphone capsule mounted on a stick. The tone generators and measurement ability are part of the software packages. Both software packages include basic measurement systems. You don't need a scope or any other fancy laboratory equipment to take basic measurements. Both software packages also have user groups on Yahoo if you have questions. To make impedance measures you just need some resistors and some test leads. You can get started measuring speakers and desinging crossovers, assuming you have the ability to build boxes, for a little bit more that you would spend on one 2440 replacement diaphragm. If you decide you want to buy a software package, I can provide you with links to user guides for each program that walk you through the entire process.

  5. #50
    pangea
    Guest
    OK, Thanks again for your help and yes please I would love to have those links!

    I've tried to read the 3155 schematic pdf document, but it is very hard if not impossible to make out the details.

    Does anyone have an edited and perhaps also a "stripped" version of that particular network, with only the essentals in it?

    BR
    Roland

  6. #51
    TimG
    Guest
    http://www.audioheritage.org/vbullet...highlight=3155
    This is the link to the modern version of the crossover. You can buy all the parts you need for this from a variety of vendors. I would recommend madisound or partsexpress in the US, but I'm sure there is some place closer to you.

    Also remember, the 4350/55 is a 4 way design with an active crossover between the woofers and midbass. The link above explains how some other people have dealt with the crossover below 290Hz.

    I will look up those links for you later tonight.

  7. #52
    PSS AUDIO
    Guest

    There it is the 3107 schematic!

    Hi,

    Have a look at it, its quite easy to build, I may have the parts.

    If you need help or parts ask ALLBA, our distributor in Sweden for the parts, we can add them while their next shipment!

  8. #53
    pangea
    Guest

    Question I'm confused

    Why are all the x-overs, mentioned in regard to the 2445, in their schematics, drawn as 8 Ohm drivers, if and when they almost always have 16 Ohm impedance, for instance the 3155, 3107 and others?

    BR
    Roland

  9. #54
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    Re: I'm confused

    I've explained this before, here it goes again -

    This is the link to the Standard Test Fixture. You take a network to be tested and hook it up to this text fixture. You run a voltage drive on the network and check the results against the specifications laid down in that particular network's matrix.

    So for the 3107 at 800 Hz with the test fixture set to 8 ohms the MB (midbass) tap should read -4 dB and the MR (midrange) tap should read - 17 dB. This has nothing to do with the actual electrical "crossover" with driver loads and it has nothing to do with the actual acoustical "crossover" of the system. It's simply a standard, consistent way of measuring all the various networks.

  10. #55
    pangea
    Guest

    Re: Re: I'm confused

    Originally posted by Giskard
    I've explained this before, here it goes again -

    This is the link to the Standard Test Fixture. You take a network to be tested and hook it up to this text fixture. You run a voltage drive on the network and check the results against the specifications laid down in that particular network's matrix.

    So for the 3107 at 800 Hz with the test fixture set to 8 ohms the MB (midbass) tap should read -4 dB and the MR (midrange) tap should read - 17 dB. This has nothing to do with the actual electrical "crossover" with driver loads and it has nothing to do with the actual acoustical "crossover" of the system. It's simply a standard, consistent way of measuring all the various networks.
    This is getting more and more complicated and possibly even too complicated for my head.

    Does this mean it's OK to just use the component values in the "8 Ohm" drawings when using 16 Ohm drivers, Or should I simply give it up and bang my head against the wall?

    BR
    Roland

  11. #56
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    Re: Re: Re: I'm confused

    Originally posted by pangea
    Does this mean it's OK to just use the component values in the "8 Ohm" drawings when using 16 Ohm drivers, Or should I simply give it up and bang my head against the wall?

    BR
    Roland
    It isn't an "8 ohm" drawing. The 3107 network is designed for an "8 ohm" 2202 load, a "16 ohm" 375/2440/HL93/2311/2308 load, and a "16 ohm" 2405 load. The 8 ohm dummy loads are simply to give an idea what the voltage drive should look like for service purposes only.

    If it seems confusing then just block out everything else on the network service bulletin and concentrate only on the schematic. Keep in mind that these things aren't meant for public consumption. If you don't fully understand them don't sweat it. All you care about is the schematic itself and the values of the capacitors, chokes, resistors and how they are wired together. You already know what the originally intended drivers are and what their load ratings are.

    Now, if you decide to pop an "8 ohm" diaphragm into a 2440, THEN you will need to make adjustments accordingly. Different horns also present different impedence loads so if you are using a different horn you will need to adjust the impedance accordingly. Chances are the acoustical properties will be so hosed with a different horn that the impedance load won't matter anyway, but maybe you will get lucky. It does happen.
    Last edited by 4313B; 11-06-2003 at 09:13 AM.

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