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Thread: Positioning of ports and driver?

  1. #31
    Member Greg_M's Avatar
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    State of the enclosures.

    Here's where I am today.
    After the big move, the enclosures wound up in the garage. That's 1-7/8" Bloodwood from South America, on the fronts and 1" particle board on the rest of the sides.
    Backs and bracing pieces are sitting on top.
    As you can see, I've got 5 sides glued together and some of the bracing inside. I just need to get out the belt sander and make all corners/edges flush and the route a radius on them.
    Before we moved I still had the machine shop's CNC mills to play with so I cut out the speaker openings and drilled holes on the insides of the fronts for hold down screws.
    So here we are.
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  2. #32
    Senior Member RMC's Avatar
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    Hi Greg,

    Good idea to get the Dayton gizmo so that you know exactly what kind of TS parameters you're dealing with. Sometimes folks get surprises, not always pleasant ones, after some "modification" to a driver. I remember one here that I helped he did same as you: he got the DATS 2 at the time, measured the woofers he bought used, when he saw the results the adjectives about the seller started flying, bastard, etc. If I recall right he abandoned the drivers. Knowing ahead of time, before further holes are cut in speaker baffle like in your case, is way better since one may be able to salvage a project with some work around (vary vol. and/or tuning).

    Btw just learned from you DATS 3 is finally released, been waiting for it since V. 2 has been around for a while. Last time I checked it was still at version 2... Now V3 is on my near future shopping list.

    You indicate having downloaded Win ISD again. Which version? 2002, 2004 or 2016, hopefully the last one. Note that, contrary to many other programs, Win ISD uses a box loss assumption of QL 10 which is NOT standard practice, often too optimistic, and this affects low frequency response modeled. The recognized standard is QL 7 so its better that you change in the software the default 10 for 7. Easy, here's how:

    When you're in BOX tab look at bottom of screen and click on ADVANCED and a small window shows QL 10 and others, click on 10 and another small window shows 10 in blue, type 7 instead and close the window. Now you have QL7 for the moment. If you save a project with QL7 it should stay at 7 when you reopen that project (check it). HOWEVER, Win ISD always defaults back to QL10 when you open the software for a new project, so everytime you must not forget when in BOX tab to go to ADVANCED and change again QL to 7 instead of 10, a little pain in the ass...

    Your box pic shows the woofer cut out is lower than middle of the boxes so that should help you reduce standing waves in the cabs. If I were you I would avoid making any other baffle holes until you get a good set of TS from DATS 3 and do some Win ISD simulations. Regards,

    Richard

  3. #33
    Senior Member Ian Mackenzie's Avatar
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    Hi Greg,

    That looks like a nice project for your new home.

    I am not clear if you plan to use these enclosures inverted (from the pic you posted)?.

    My impression was your earlier plan was to use the woofer up to 600 hertz.

    Your plans for the mid/high frequency driver of your choice will dictate how you orient the enclosures.
    Ideally the woofer should not be far from the mid range driver or horn.

    Depending on the size of the horn you may wish to mount it on top of the enclosure. Or if the enclosure has sufficient depth mount the horn inside the enclosure. This will impact on placement of the ports on the front baffle.

    The 5 cu ft 3 tuning at 30 hertz is going to give you a smooth non drooping response with a -3 frequency around 35 hertz and will be -6 db about 32 hertz.

    If you have a larger than the recommended 5 cu ft 3 enclosure up to around 8 cu ft3 and tune according to your software the response will droop down but will extend lower. The port will be more active at lower bass frequencies due to the lower tuning frequency. The ports will play a more audibly aggressive role in the bass response on most program material with the recommended 5 cu ft 3 enclosure tuning.

    Placing the enclosure close to a wall boundary or a corner will compensate for the dropping response to some extent. Its entirely subjective.

    Depending on how your room reacts with the system and the enclosure placement you will find out fairly quickly what enclosure size and tuning you prefer just by listening to the amount of bass you hear subjectively. The tuning differences are quite obvious with the 2235H.

  4. #34
    Member Greg_M's Avatar
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    I could put the woofer on top or on bottom at this point. It's just a matter of where to put the feet.
    I had planned to put the woofer on the bottom, as they are sitting now.
    When I last worked this project I bought a pair of JBL 2380A horns and 2446 drivers.
    They are still waiting too.

    I had the woofers reconed at a JBL fix it place in Lynnwood, WA so hopefully they are close to factory specs. We'll see.
    I also have a pair of Altec 421As that I got for some reason, can't remember why now.

  5. #35
    Member Greg_M's Avatar
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    Quote Originally Posted by RMC View Post
    Hi Greg,

    Good idea to get the Dayton gizmo so that you know exactly what kind of TS parameters you're dealing with. Sometimes folks get surprises, not always pleasant ones, after some "modification" to a driver. I remember one here that I helped he did same as you: he got the DATS 2 at the time, measured the woofers he bought used, when he saw the results the adjectives about the seller started flying, bastard, etc. If I recall right he abandoned the drivers. Knowing ahead of time, before further holes are cut in speaker baffle like in your case, is way better since one may be able to salvage a project with some work around (vary vol. and/or tuning).

    Btw just learned from you DATS 3 is finally released, been waiting for it since V. 2 has been around for a while. Last time I checked it was still at version 2... Now V3 is on my near future shopping list.

    You indicate having downloaded Win ISD again. Which version? 2002, 2004 or 2016, hopefully the last one. Note that, contrary to many other programs, Win ISD uses a box loss assumption of QL 10 which is NOT standard practice, often too optimistic, and this affects low frequency response modeled. The recognized standard is QL 7 so its better that you change in the software the default 10 for 7. Easy, here's how:

    When you're in BOX tab look at bottom of screen and click on ADVANCED and a small window shows QL 10 and others, click on 10 and another small window shows 10 in blue, type 7 instead and close the window. Now you have QL7 for the moment. If you save a project with QL7 it should stay at 7 when you reopen that project (check it). HOWEVER, Win ISD always defaults back to QL10 when you open the software for a new project, so everytime you must not forget when in BOX tab to go to ADVANCED and change again QL to 7 instead of 10, a little pain in the ass...

    Your box pic shows the woofer cut out is lower than middle of the boxes so that should help you reduce standing waves in the cabs. If I were you I would avoid making any other baffle holes until you get a good set of TS from DATS 3 and do some Win ISD simulations. Regards,

    Richard

    I'll check out the version today.
    Is there a way to get version 7 somewhere and permanently install it?

  6. #36
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by Greg_M View Post
    I could put the woofer on top or on bottom at this point. It's just a matter of where to put the feet.
    I had planned to put the woofer on the bottom, as they are sitting now.
    When I last worked this project I bought a pair of JBL 2380A horns and 2446 drivers.
    They are still waiting too.

    I had the woofers reconed at a JBL fix it place in Lynnwood, WA so hopefully they are close to factory specs. We'll see.
    I also have a pair of Altec 421As that I got for some reason, can't remember why now.
    Well it sounds like your having fun.

    When your ready send me a Pm and l will help you with with the crossover network. I have measurements of both the woofer and the horn / compression driver and can punch out either a passive to active solution.

    That timber on the front panel is very nice. You canít buy affordable loudspeakers with that finish these days.

  7. #37
    Member Greg_M's Avatar
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    The pretty wood came from Edensaw, by Port Townsend, WA.
    http://www.edensaw.com/MainSite/Stor...egoryHome/1092

    I used to live about a half hour from there.
    It makes my mouth water to go to that place. They have exotic and domestic woods from all over the planet.
    I got that chunk of wood in one big piece. Enough to do both box faces and some left over for a turntable base. (another project).
    They do a lot of boat building up there in PT.

  8. #38
    Member Greg_M's Avatar
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    My WinISD program version is 0.7.0.950
    I was able to change QL 10 to QL 7 as suggested and when restarted it came up as 7.

    One question I have is what is 1st Port Resonance ?
    By changing port size it changes. What should I be aiming for there as a value?

  9. #39
    Senior Member RMC's Avatar
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    Hi Greg,

    Your Win ISD version is the 2016 one and that's fine (most recent).

    Even if QL7 came back that time, do check it periodically as QL10 WILL come back as default value (except in a saved project).

    RE first port resonance:

    From the help files of Win ISD ( open INFO at top, choose HELP, in the list of links then click Designing your box):

    "Here, you can decide how many and of what shape you want your vents to be on your box. The ports, of course, serve to "tune" your box to the frequency that you have chosen while you were designing your box in the Plot Window. The size and -3dB (cutoff) frequency of your box determine the size of the ports.

    1st port resonance shows frequency of first "organ-pipe" resonance. This helps you to estimate where port becomes undesired radiator.

    Very important here is to make your ports large enough, so that peak air velocity won't exceed 5% of sound velocity in air. That is, about 17 m/s assuming normal environmental conditions. You can check it by using "Rear port - Air velocity" graph, by first setting simulation power to anticipated maximum power, see "signal"-tab. In this case, Pe is 125 Watts. "

    In practice you don't really choose a specific value of 1rst port resonance, but that sophistication isn't a bad idea re woofer crossover frequency:

    For example, I modeled quickly 2235H in 5 cu.ft. with Fb 30 Hz and the 1 rst resonances were: 1 X 5" tube gave 840.5 hz, and 2 X 4" tubes gave 561 hz. The 5" one having a higher 1 rst resonance would give increased XO frequency flexibility, without having port resonance in the way... Gotta go. Regards,

    Richard

  10. #40
    Member Greg_M's Avatar
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    I got the DATS V3 test gizmo and did a test of my re-coned JBL 2235H (once I figured out how to run it). I also tested a Klipsch 10" K-1036.
    Here is a dump from the V3 software.
    I'll enter these values in to WinISD and see if it makes a difference.


    * This data was exported from the Dayton Audio Test System: DATS
    *
    * Piston Diameter = 342.9 mm
    * f(s)= 27.59 Hz
    * R(e)= 6.107 Ohms
    * Z(max)= 148.5 Ohms
    * Q(ms)= 8.941
    * Q(es)= 0.3834
    * Q(ts)= 0.3676
    * V(as)= 187.1 liters (6.606 cubic feet)
    * L(e)= 1.6 mH
    * n(0)= 0.9769 %
    * SPL= 92 1W/1m
    * M(ms)= 213.1 grams
    * C(ms)= 0.156 mm/N
    * BL= 24.26
    * K(r)= 0.05604
    * X(r)= 0.5535
    * K(i)= 0.0164
    * X(i)= 0.7138
    *

  11. #41
    Senior Member RMC's Avatar
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    Greg,

    For comparison purpose the following are the parameters given in the official JBL table:

    MODEL FS QTS QMS QES VAS EFF PE XMAX RE LE SD BL MMS FLUX
    2235H 20 0.25 2.5 0.28 458.7 1.3 150 8.38 6 1.2 0.090 20.5 155 1.2

    Some show quite sizeable differences between your actual numbers and those from JBL, doesn't necessarily mean the driver is worthless, but simply that its different from an original one, therefore may require some box adjustments.

    Qts is pretty high which normally leads to larger appropriate box, however Vas is pretty low which normally leads to a smaller box size, so the latter compensates somewhat for the former (these two are appropriate box size influencers).

    Double check your DATS measurement procedure just to be sure you got this right. Did DATS make you do a driver "conditioning" period before measurements? Usually driver parameters are taken after a couple of hours of driver suspension "loosening" for example ("Thiele/Small parameters are measured after a 2 hour exercise period...")

    As I said before I haven't followed your project from the beginning but maybe your recones are not original ones with such differences? Or no driver conditioning was done? Regards,

    Richard

  12. #42
    Member Greg_M's Avatar
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    Quote Originally Posted by RMC View Post
    Greg,
    Some show quite sizeable differences between your actual numbers and those from JBL, doesn't necessarily mean the driver is worthless, but simply that its different from an original one, therefore may require some box adjustments.
    Richard
    Yes it is a re-coned driver. It was done by Morgan Sound in Lynnwood WA.


    Quote Originally Posted by RMC View Post
    Greg,
    Did DATS make you do a driver "conditioning" period before measurements? Usually driver parameters are taken after a couple of hours of driver suspension "loosening" for example ("Thiele/Small parameters are measured after a 2 hour exercise period...")
    Richard
    No DATS did not suggest conditioning, but I did do the measurement twice because I goofed it up the first time.
    The measurements were slightly different the second time so probably there is something to your suggestion.


    Quote Originally Posted by RMC View Post
    Greg,
    As I said before I haven't followed your project from the beginning but maybe your recones are not original ones with such differences? Regards,
    Richard
    I bought the speakers used and took them in and had them re-coned myself.
    When I opened the box today the receipt was still in there. They've just been sitting on the shelf since 2013. They are virgins.


    I wonder what frequency they should be run at to condition them?

  13. #43
    Member Greg_M's Avatar
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    I have it hooked up at it is vibrating away at 40 cps.
    It's not very loud (probably a good thing) but it's as loud as it will go.

  14. #44
    Senior Member Ian Mackenzie's Avatar
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    Itís basically a new unused driver which can take forty hours of continuous use to break in.(as published by Jbl).

    Mount it in a vertical position if you can so the cone mass is not weighing on the spider and surround.

  15. #45
    Senior Member RMC's Avatar
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    Greg,

    Who did the recones isn't really the issue here, but rather what recone kit was used, original JBL or aftermarket? Since you still have the receipt maybe its written on it the recone brand or part number? Even on the back of the cones there could be some indications like a part number?

    Richard

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