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Thread: Pros and Cons of Generic Port Placement in a Multi-Woofer System i.e. 2235H

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    Member hightechhick's Avatar
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    Pros and Cons of Generic Port Placement in a Multi-Woofer System i.e. 2235H

    The goal of this thread is to discuss the pros and cons of generic port placement in a DIY speaker system consisting of two woofers per cabinet (one large box with an internal dividing partition) and its respective port system.

    I poked around for an existing thread that covered this topic, but I did not see anything. If I am wrong, please accept my apology.

    I just finished internal dimension drawings for a new DIY project that will have (per cabinet) a 2370A horn at the top with a 2425H horn driver, 2 each 2235H 15" woofers, and a 2245H in a "quasi-5th order" alignment cabinet tuned to 20 Hz.

    I have not cut any wood, so I am flexible to any design input!

    The entire unit is vertical to accomodate the room it will be used in (~3,000 square foot youth room with 5/8" drywall, drop acoustic tile ceiling at 12', and office carpet over concrete).

    Given: Each 15" woofer cabinet uses 2 each ports (4" ID x 11" long)

    Here is my question:
    If I have two 2235H 15" woofers in one cabinet, using a dividing partition, and mounted vertically, where should I place the 2 ports in each of the 15" woofer cabinets?

    Believe I have 3 options:
    1) Make both cabinets like the 4430's with 2 ports in each cabinet at 11 and 1 o'clock above the woofer.

    2) Make the upper cabinet like the 4430's and the lower cabinet with the ports at 7 and 5 o'clock. This would have the woofers close to each other with the ports above and below its woofer respectively.

    3) Make the ports close to each other (ports at the bottom of the upper cabinet and the top of the lower cabinet) making the woofers farther from each other.

    -Another variable are the 2235H cabinets will be sitting on a 12 cubic foot 2245H sub-woofer cabinet with one large port (9" diameter x 30" long - 2245H in a "quasi-5th order" alignment cabinet tuned to 20 Hz). Where should I put this port in respect to the two 15" woofer cabinets sitting on top of this?

    -Another side question:
    1) Is it better to build one huge cabinet vertically or 3 medium/large cabinets stacked and mechanically attached to each other? This will be used in a busy room and I like the idea on one huge beefy cabinet that will not be tipped over easily (or moved). I am currently planning to build "separate" boxes inside the one huge box. Any thoughts?

    I honestly do not know what to do in this situation as I have never built a multi-woofer system.

    Your help is always greatly appreciated!

    -Scott, N9ONK

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    Administrator Robh3606's Avatar
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    Hello Scott

    Have you looked at this in any box programs? Just seems odd to be using paired 2235's with 2245 under them as subs. You can put the ports anywhere they make sense depending on how the boxes work out for placement. You want the 2370 at or close to ear level so watch the stack height. You can also aim them but how well that works depends on the angle and how deep you seating area is.

    Modular is probably a better idea. It won't be any fun bracing a cabinet that size at it will get heavy as hell.

    Rob
    "I could be arguing in my spare time"

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    Member hightechhick's Avatar
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    Hey Rob,
    Thank you for your reply! This gives me much to consider.

    What is your favorite box design program?

    I am actually intimidiated by running a box program as I do not trust myself generating my own data. I really need to get up to speed in this area... I normally use existing designs and cautiously modify them. This is by far the largest and most aggressive speaker building project I have undertaken.

    I am actually relieved that the 2245H's are not necessary (I am getting this impression?). That would have been a design challenge in several areas.

    I agree that keeping the horn at ear level is very important. These will mostly be used while people are standing. Eliminating the 2245H's will greatly help this.

    They will need to be angeled in a bit. This is the current configuration of the speakers in the this area.

    Thanks again,
    Scott N9ONK

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    Administrator Robh3606's Avatar
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    The 2235 and 2245 share almost the same bandwidth down low. Obviously a 2245 will outperform a single 2235 but when you are using 2235's in pairs they are very capable down low. If you were going with an HT set-up you could use the 2235 for fullrange mains and the 2245 as the LFE's.

    You could still use them. You may want to change things around a bit. 2245's make killer subs. You could take a single 2235 in a small cabinet with the 2370 on top of the 2245's. That way you don't have 2 15's working up to the horn. A pair in a vertical array will start giving you problems above 800hz from lobing. Are you going for maximum SPL or a really nice sounding system??

    Try both the 2235 and 2245 in the program in different configurations to see how they look. How are you crossing this stuff over??

    Try downloading Win Isd. It's free, very easy to use and gives you good results. All the standard JBL woofers are already loaded so all you have to do is but in box size and tuning to get started.

    http://www.linearteam.dk/default.aspx?pageid=winisd

    Rob
    "I could be arguing in my spare time"

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by hightechhick View Post
    I honestly do not know what to do in this situation...
    Your honesty is appreciated. I agree with Rob, if cosmetically you can live with modularity, in the long run you will be happier with a few big heavy boxes instead of a couple of real monsters.

    As Rob said, the port placement almost doesn't matter... ideally you will not place a port too close to a cabinet side as it will change the effective length of the port... usually two inches away from any sides is considered safe.

    As far as whether or not you'll need the 2245s? If this is a real HT system, you will need some sort of sub(s), if it is for music playback the 2235s will certainly fill the bill.

    Now about that 2370... must you?


    Widget

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    RIP 2011 Zilch's Avatar
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    Find Guido's vertical 4435 project thread here, and consider using 2234H rather than 2235H, which are interconvertible.

    I don't believe the 2245H subs are necessary, but if you find you want them anyway, build (and locate) them separately.

    I agree with Mr. Widget that 2370A is not an optimum horn choice, though I admit I still haven't tried the revised comp filter posted elsewhere in this forum. Three-way, that may be less of an issue, but even in that case, there are better options....

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    Senior Member SMKSoundPro's Avatar
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    Dear Scott,

    These are the boxes I built with the goal being a good speaker for general PA and music playback. I cloned the SR4733 using two 2225 woofers, a 2245 on a 2385 horn and added one working bullet and one one fake bullet.

    I drive them with a three way crossover and Crown amps. These boxes really get it on for the dance floor and "talent" show stuff and seem fine for karaoke night as well. I guess just a good all-around speaker box. The size is reasonable in my book and were quite simple to build.

    Photos are attached. I then stacked them on top of two double sub cabs with 2241's driven by its own crossover at 80 hz. It really fills in the bottom!!!
    Attached Images Attached Images     
    One step above: "Two Tin Cans and a String!"
    Longtime Alaskan Low-Fi Guy - E=MC▓ ▒3db

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    Member hightechhick's Avatar
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    Quote Originally Posted by Robh3606 View Post
    The 2235 and 2245 share almost the same bandwidth down low. Obviously a 2245 will outperform a single 2235 but when you are using 2235's in pairs they are very capable down low. If you were going with an HT set-up you could use the 2235 for fullrange mains and the 2245 as the LFE's.

    You could still use them. You may want to change things around a bit. 2245's make killer subs. You could take a single 2235 in a small cabinet with the 2370 on top of the 2245's. That way you don't have 2 15's working up to the horn. A pair in a vertical array will start giving you problems above 800hz from lobing. Are you going for maximum SPL or a really nice sounding system??

    Try both the 2235 and 2245 in the program in different configurations to see how they look. How are you crossing this stuff over??

    Try downloading Win Isd. It's free, very easy to use and gives you good results. All the standard JBL woofers are already loaded so all you have to do is but in box size and tuning to get started.

    http://www.linearteam.dk/default.aspx?pageid=winisd

    Rob
    Hi Rob,

    Lobing!?! I have never heard of this problem before...

    Thanks for the link! I learn free software much easier than the expensive stuff ;-) This looks like a critical design tool that I need!

    I am not familiar with the HT acronym.

    My goal is a really nice sounding system located in a large and rather reflective room.

    I am using an electronic crossover with variable crossover points. Each driver will have its own amplifier.

    I have built the 2245H in a quasi-5th order box twice from the old article in Audio Magazine. If memory serves a boost of 6db at 20Hz makes the box flat to 20Hz (I like Virgel Fox pipe organ music).

    Thanks again for your patience and GREAT help,
    Scott, N9ONK

  9. #9
    Member hightechhick's Avatar
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    Quote Originally Posted by Mr. Widget View Post
    Your honesty is appreciated. I agree with Rob, if cosmetically you can live with modularity, in the long run you will be happier with a few big heavy boxes instead of a couple of real monsters.

    As Rob said, the port placement almost doesn't matter... ideally you will not place a port too close to a cabinet side as it will change the effective length of the port... usually two inches away from any sides is considered safe.

    As far as whether or not you'll need the 2245s? If this is a real HT system, you will need some sort of sub(s), if it is for music playback the 2235s will certainly fill the bill.

    Now about that 2370... must you?

    Widget

    --------------------------

    Hello Mr. Widget,

    Very good on the first two paragraphs, thank you.

    I am not familar with the HT acronym (high tech? high performance? highly tuned?).

    From what I have read so far, I am now leaning toward building two 2245H's in 12' boxes tuned to 20Hz from the old Audio Magazine article (1980's?) with a pair of 2235H's above them in separate boxes. I have one 2245H in the room in question now (~3,000 sq. ft.) and while frightning in a house (knocks rust off iron pipes, destroys filament lamps, etc.), one is just above marginal in a huge room (IMHO).

    Please expand (educate me please) on your 2370A concern. I selected this horn because it has the same driver as the 4430. Obviously the actual horn is different than the 4430. I was thinking a non-bi-radial horn would be more directional and less reflective in a large room (office carpet over concrete with hard drywall and drop ceiling). My design goal is to closely duplicate the sound of the 4430 monitor in a large room. I do not like harsh sounding horns. Is this where I am heading? I purchased a parametric EQ with hopes of flatening out the known peaks of this horn.

    What would you use for 800Hz and up for this application?

    I have drivers on the shelf, but I have not commited to the final design.

    Thanks again,
    -Scott N9ONK

  10. #10
    Member hightechhick's Avatar
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    Quote Originally Posted by SMKSoundPro View Post
    Dear Scott,

    These are the boxes I built with the goal being a good speaker for general PA and music playback. I cloned the SR4733 using two 2225 woofers, a 2245 on a 2385 horn and added one working bullet and one one fake bullet.

    I drive them with a three way crossover and Crown amps. These boxes really get it on for the dance floor and "talent" show stuff and seem fine for karaoke night as well. I guess just a good all-around speaker box. The size is reasonable in my book and were quite simple to build.

    Photos are attached. I then stacked them on top of two double sub cabs with 2241's driven by its own crossover at 80 hz. It really fills in the bottom!!!
    Hello,
    I love your shop! It looks like you have lots of fun building. My shop is about the size of a one car garage, but I can expand into a larger hallway for cabinet assembly.

    Crown amps are among my favorites, too. I knew an engineer who left RCA to work there many years ago (northern Indiana?), and he still may be there.

    Your pictures are great! I plan to put mine on here once I get started.

    Thanks again for the reply,
    -Scott N9ONK

  11. #11
    Member hightechhick's Avatar
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    Quote Originally Posted by Zilch View Post
    Find Guido's vertical 4435 project thread here, and consider using 2234H rather than 2235H, which are interconvertible.

    I don't believe the 2245H subs are necessary, but if you find you want them anyway, build (and locate) them separately.

    I agree with Mr. Widget that 2370A is not an optimum horn choice, though I admit I still haven't tried the revised comp filter posted elsewhere in this forum. Three-way, that may be less of an issue, but even in that case, there are better options....
    Hello Zilch,
    If I am trying to duplicate the 4430's sound in a large room (office carpet on concrete floor, hard drywall walls, and drop ceiling, what would you recommend for 800Hz and up in a ~3,000 Sq. Ft. room?

    Thanks,
    -Scott N9ONK

  12. #12
    Senior Member duaneage's Avatar
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    I think you should work on the room first. The acoustics are bound to be difficult to say the least. Consider room treatments, bass traps, anything at all to deaden the room a bit. You'll be happier with the results.

    I've built countless systems in my garage and they always sound bad out there. In rooms with carpeting, furniture, etc, they sound so different. I would spend more time studying where the problems lie in your room.

    There are simulation programs that can predict room response, some are even free. you need to look at reverbration times, decay, and dimensions. To eliminate standing waves, for example, you need to choose speaker placement and traps carefully, testing the results.

    Great sound is not just a matter of monster woofers, huge amps and big bucks.
    Why buy used when you can build your own?

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    Senior Member Doctor_Electron's Avatar
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    Quote Originally Posted by hightechhick View Post
    I knew an engineer who left RCA to work there many years ago (northern Indiana?), and he still may be there.
    I think it was Elkhart, unless they had facilities other than those where they made those cool reel-to-reel decks.

    I had two 2235H's in 5 ft3 cabs, with 2380 horns / 2440 drivers, and 2405's on top...
    I used the old JBL two-way electronic crossover (not super "fi" IMO) and modded 3107 xovers.

    Those 2380 / 2440 mids were cabable of generating serious pain if not kept at a reasonable spl. Earl Klugh's bassist Hubey Crawford, "popping" his bass, could knock dust loose around the (much smaller than your) room, but it also sounded great.

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