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Thread: 4430 port tuning with different drivers

  1. #1
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    4430 port tuning with different drivers

    First time poster, long time JBL fan.

    I'm planning to build a pair of DIY 4430's. They won't be clones, but they will be similar enough for me. I found plans for the cabinets on this forum from back in 2004, so building a version of the cabinets won't be a problem. I have all the components. Unfortunately my LF drivers are not 2235's. I have a pair old Alnico 2205A's that I'll be using.

    My question is about proper tuning of the cabinet with the 2205's. Do I need to change the port diameter and length to keep the frequency response the same, or at least similar? I've done a bit of research into how this is done, but it's a bit beyond me, I'm not confident I would come up with the correct measurements. If they need to change would any of you with the necessary knowledge consider crunching the numbers for me? With any luck I'll blow the dusty old 2205's up and get them reconed to 2235's... or something similar!!

    So, Alnico 2205A's, 5 cubic feet, 2 ports... need any more info?

    Thanks for any help.

    Gary

  2. #2
    Administrator Mr. Widget's Avatar
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    Here is a simple guide that can be used as a general template for your needs.

    https://www.jblpro.com/pub/manuals/enclgde.pdf


    Widget

  3. #3
    Senior Member RMC's Avatar
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    Hi Gary,

    If you look at the Enclosure Guide document referred to by Widget, the 2205 is more suitable for 4 cu.ft. tuned at 40 hz and the 2235 is more suitable for 5 cu.ft. tuned at 30 hz.

    The 4430 has 5 cu.ft. net, tuned at 34 hz and uses the 2235H. My advice is don't waste your time with a 2205 (which I own) in a box this size and tuning as your likely to be unsatisfied by woofer performance. You will have more chances of being pleased sonically with your project if you go ahead with reconing them as 2235H in that particular context.

    The 2205 performs better bass wise in a box of about 4 cu.ft. tuned around 45-50 hz, and it doesn't have the requirements to go deep in the low frequencies. You would get lower output in LF than a 2235.

    The 2205 is a sound reinforcement engineered driver not a hi-fi driver and your project revolving around a 4430 type is more related to hi-fi and requires a more hi-fi type woofer with deeper bass capability and improved linearity. If need be I could model it for you in speaker design software as well as port tuning.

    Regards,

    Richard

  4. #4
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    Thanks RMC,

    I've seen the guide widget linked to and thought it was odd that it suggested 4 cu.ft. for a 2205 or 2225. The enclosures JBL offers for those speakers that I've seen are 5 cu. ft, the 4507 and EN5. After doing a bit more research the idea of HiFi vs Basic sound reinforcement you were talking about makes more sense, might as well do it right so that's the direction I'll be going.

    I'll be looking for a used pair of 2235's. For some reason I'm not excited about reconing the old alnico 2205's.

    In the mean time, I think I'll build the cabinets to 4430 specs and if I don't have the 2235's by the time I'm done I'll drop the 2205's in temporarily. Would lengthening or shortening the ports improve frequency response?

    Thanks

  5. #5
    Senior Member RMC's Avatar
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    Hi Gary,

    I made some speaker software simulations for you as wells as calculations of the related vent lengths for these. Its quite possible you'll need to shorten vent lenght, depending on LF response you want with the 2205 in a 4430 cab. I have 5 pics of the LF responses and vent dimensions simulations for you.

    I'll be back tomorrow evening with all this, gotta go sleep now its well past midnight eastern time and I'm falling asleep already... "All good things come to those who wait" Regards,

    Richard

  6. #6
    Senior Member macaroonie's Avatar
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    Ports

    I believe that if you hunt about on the www that there exists such a thing as an adjustable port.

    https://willys-hifi.com/collections/...ble-large-size

    parts express got a couple also.

  7. #7
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    Quote Originally Posted by macaroonie View Post
    I believe that if you hunt about on the www that there exists such a thing as an adjustable port.

    https://willys-hifi.com/collections/...ble-large-size

    parts express got a couple also.
    I've tried the adjustable ports. Some things to keep in mind, make your opening in the cabinet a little larger because you will want to use tape as you adjust the length of the port(s). It is a repetitive process as you fine tune them. Once you determine the length, again, tape is your friend to define the final length before the ABS cement is use to seal and finalize the length (you need to make a "stop line" when you push them together.

  8. #8
    Senior Member RMC's Avatar
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    Hi Gary,

    The original 4430 cabinet has two vents, each with 4 1/8" inside diameter and a total length of 8 1/4" (including say 3/4" thickness for front panel).

    Note the simulations are done with the standard box loss of QL 7 and half-space loading (e.g. boxes on the floor, one boundary).

    The first pic (# 486) shows the expected low-frequency response of a 2205 in 5 cu.ft. tuned at 34 hz, so a 4430 box. Note the low end is pretty rolled off with -5 db at about 45 hz. This illustrates the lower LF output I mentioned previously. Two or three boundary box placement (floor and back wall, or corner placement) may increase the lows and make the response flatter (room gain is free).

    Second pic (# 487) also shows the required vents length for the above case. Note the vent length indicated by the Winspeakerz software I used to simulate these is the exact same as the JBL number for 4430...

    Third pic (# 488) shows this time LF response curves with 2205 in 5 cu.ft. box tuned at 45 hz (lower curve) and at 50 hz (upper curve) on same graph. The response drop around 100 hz on both curves is typical, showing the 2205 is overstretched in that box volume (i.e. the shoes are too large for it). Typical because such curves often happen when a driver is asked to perform in a cab which in reality is too large for best performance.

    So my previous mention (post # 3) that the 2205 performs better LF wise in a box tuned in the 45-50 hz range is in the ballpark, and the curves would be flatter had the enclosure volume been about 4 cu.ft. instead of 5 cu.ft., the rated 97 db sensitivity line on the graph being the reference level.

    Fourth pic (# 489) gives you the vent dimensions for the above 45 hz tuned box (showing part of the LF curve behind) if you decide to go this way, and the fifth pic (# 490) are the vent dimensions for the above 50 hz tuned box (also showing behind part of the LF curve) in case you prefer that one.

    Personnaly, I would tend to go with the 50 hz tuning curve because at least part of the bass range, say 50-70 hz, is at about the same level (within 1 db) as the driver's reference level. Other reasons apply to that preference, but too long to explain now.

    BTW though Macaroonie's extendable/retractable vent idea seems quite appealing, in practice I tend to agree with Sguttag. I don't really trust these vents re air leaks or possible rattle noise. Never used them.

    There you have it, sort of "all dressed" I guess. Regards,

    Richard


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  9. #9
    Administrator Robh3606's Avatar
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    You are building a system basically from scratch. If you run a 2235 in a box program take a look at 5 cubic ft tuned to 30 hz. Go from there.

    Rob
    "I could be arguing in my spare time"

  10. #10
    Dang. Amateur speakerdave's Avatar
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    If you have some clean 2205's, that is, not wrung out and preferably having lived in a domestic environment, AND they have the original cones, I agree completely with your being reluctant to recone them with 2235 kits. They are a unique driver, not just an Alnico 2225; they have a somewhat more relaxed suspension, and some people like the way they make bass. Study the data sheets in the SPECS section of the JBL library and the numbers for three drivers on a theille parameter chart: 2205,2225, 2234. I believe you will find the 2205 fits in about midway (2234 is 2235 without the mass ring).

    Besides, you want ferrite frames for 2235's anyway. 2235's don't come up for sale often. The quickest route to some 2235's is probably to track down some 2225 frames, which are exactly the same as the 2235 and are very numerous. Have them reconed with genuine 2235 kits, and Bob's your Uncle.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Quote Originally Posted by RMC View Post
    Hi Gary,

    The original 4430 cabinet has two vents, each with 4 1/8" inside diameter and a total length of 8 1/4" (including say 3/4" thickness for front panel).
    Hi Richard,

    is this verified? I recall enclosure drawings here at this site that call for 102 mm/4" internal diameter ?

    Best regards!

  12. #12
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    I can confirm 4.125” diameter by 8.25” long on my OEM pair.

  13. #13
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    Ok, then I'll have to rethink my project, as plumbing tubes of this dia aren't available over here .

    Otoh, is there a way to calculate the correct length for 4"/102mm tubes?

    Best regards!

  14. #14
    Senior Member macaroonie's Avatar
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    2235 my $0.02

    I have 2235H running below a B&C 2 " comp driver in 2380 horns in an active set up.
    My experience has been that the 2235H is not happy at all in the region of the 800Hz crossover point. It stands to reason , the mass ring will simply not let the bass cone move at that frequency. Over a period of time I have adjusted the X/O downwards to just over 600Hz , the horn plays well there and the 2235 is not attempting to play beyond it's means. Below that the horn / CD reaches it's bottom limit and that is clearly audible.
    In simple terms the 2235 makes the overall sound muddy , dark , foggy call it what will.
    Unfortunately the 1" horn in the 4430 will probably not be very happy below 800 Hz.
    For the above reasons 2234 is probably your best bet , or if you must go 2235 then find a driver / horn that will go lower than 800Hz.


    PT HF1010 + 2450sl maybe ??

  15. #15
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    Remember that in the 4430 monitor that runs the 2235H the xover frequency is 1 kHz, not 800 Hz!

    But some say that the huge 4435 with it's two 2234H's (2235's without mass rings) have either better bass response (due to 2½ way layout) and better mid resolution. Both might be well explained by your arguments.

    Best regards!

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