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Thread: 4628B make over

  1. #1
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    4628B make over

    I'm finally getting back to this project. i'm in the works of redoing 4628Bs the plan is E145-2118- ESS AMT-1A air motion transformer . the help I need for know is calculating the port length. what I did is carefully removed the front panel and replaced it with a new one flush mounted unitizing only the E145 and 2118 the problem was not much room on front panel for the port so I decided to side port it using the carrying handles cut outs on the side panels for the ports 2 ports one on each side . stock port measured 5 7/8 ID x 5 3/4 L i came up with 5.750 x 3.875 x 3.562 L 2 ports per cabinet my question is am i close to port tuning ? hopping Rob could shine in on this

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    Senior Member RMC's Avatar
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    Hi kartsmart,

    Sorry for not being the Rob you're expecting, but I may still shine on this....

    RE: "the help I need for know is calculating the port length"

    Your thing isn't rocket science, but first you have to calculate the right box volume. And determine what box tuning frequency are you expecting or looking for?

    RE: "what I did is carefully removed the front panel and replaced it with a new one flush mounted" Assuming you used the same front panel thickness and that your ESS Air Motion Transformer will be mounted on TOP of the box not in it, you have still changed (increased) the box volume considering the original 4628B front panel is recessed (yours is flush mounted) and no 2404 in the box (btw 4628B box volume is given at 4.5 cu.ft.-possibly net?- and no tuning frequency mentioned in Spec Sheet nor in Technical Manual).

    I can certainly help you if you're patient (busy these days) but for this thing to make sense you need a correct box volume to start with. Then, since you measured the vent we can find a tuning frequency using the JBL tuning chart I posted recently in "General Product information/Has Anyone Ever Seen These" thread with reverse engineering to figure the original box Fb, as a starting point.

    However, since Vb is changed the original Fb may not still be the best suited. So at that point my guess is that a remodel of the box in speaker software, such as Winspeakerz or Win ISD Pro I have, may be needed...

    Regards,

    Richard

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    Quote Originally Posted by RMC View Post
    Hi kartsmart,

    Sorry for not being the Rob you're expecting, but I may still shine on this....

    RE: "the help I need for know is calculating the port length"

    Your thing isn't rocket science, but first you have to calculate the right box volume. And determine what box tuning frequency are you expecting or looking for?

    RE: "what I did is carefully removed the front panel and replaced it with a new one flush mounted" Assuming you used the same front panel thickness and that your ESS Air Motion Transformer will be mounted on TOP of the box not in it, you have still changed (increased) the box volume considering the original 4628B front panel is recessed (yours is flush mounted) and no 2404 in the box (btw 4628B box volume is given at 4.5 cu.ft.-possibly net?- and no tuning frequency mentioned in Spec Sheet nor in Technical Manual).

    I can certainly help you if you're patient (busy these days) but for this thing to make sense you need a correct box volume to start with. Then, since you measured the vent we can find a tuning frequency using the JBL tuning chart I posted recently in "General Product information/Has Anyone Ever Seen These" thread with reverse engineering to figure the original box Fb, as a starting point.

    However, since Vb is changed the original Fb may not still be the best suited. So at that point my guess is that a remodel of the box in speaker software, such as Winspeakerz or Win ISD Pro I have, may be needed...

    Regards,

    Richard
    yes your correct on the front panel but with the extra bracing i used and ports made out of 3/4' stock box volume should me very close to original / as for the software i no longer have excess to . was hoping someone could help out there / rob seemed to aways thought the tuning of the 4628 could have been lower for home use thankx

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    Administrator Robh3606's Avatar
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    Not sure I am the right Rob but I use E-145's in 5 cubic ft tuned to 40Hz and even though they have usable in room response to about 40Hz they are down quite a bit. You are going to need subs under them they just cannot do 25-60Hz like a 2235 or an Le-14-3 for that matter. Post the internal volume and I will run it in software for you and post the results.

    Rob
    "I could be arguing in my spare time"

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    Quote Originally Posted by Robh3606 View Post
    Not sure I am the right Rob but I use E-145's in 5 cubic ft tuned to 40Hz and even though they have usable in room response to about 40Hz they are down quite a bit. You are going to need subs under them they just cannot do 25-60Hz like a 2235 or an Le-14-3 for that matter. Post the internal volume and I will run it in software for you and post the results.

    Rob
    your the one its the original 4826 boxes same cubic ft as for subs i got a pair of 2246 18" suds

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    Senior Member RMC's Avatar
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    Hi kartsmart,

    Just to give you some idea. Sorry for the not so good pictures...

    Quick modeling in Winspeakerz Vb 4.5-5 cu.ft, Fb 40 hz: indeed "they are down quite a bit." as mentioned, only 5 cu.ft. shown but I did model both, almost identical curves.

    For a flatter response shown on other picture, Vb 4.5 cu.ft, Fb 54 hz, F3 at 52 hz.

    Naturally, the type of response you want to achieve (e.g. for use of box as stand alone and/or with sub) will impact tuning frequency and evidently on the required vent dimensions...

    All modeling done here assuming half-space box placement and Ql 7.

    I'll let you continue your ride with the real fellow you were looking for. Regards,

    Richard

    EDIT Order of pictures incorrect, the second one should have been first


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    Administrator Robh3606's Avatar
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    Hello Kartsmart

    I did it in WinIsd and Bassbox Pro I trust Bass Box more as you can include the fill and I have ended up with Fb within 1/2 hz when all was said and done. You can easily verify Fb with a simple impedance sweep. Just look for the lowest value between the peaks and that's it. The Fb I used was 55Hz. Box 4.5 cubic ft. Let me that was right. I will post both just for fun. You have to remember to change Vas to the correct value as it is wrong in the T/S table. The correct value is 427 liters. In BBP they come out to 3.06 inches long so 3" long longer in Win Isd at 5" I would defiantly use the BBP but you can always try both and do an impedance sweep for the actual Fb measurement. I assume you are crossing them at about 80Hz or so?

    Rob
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    Quote Originally Posted by Robh3606 View Post
    Hello Kartsmart

    I did it in WinIsd and Bassbox Pro I trust Bass Box more as you can include the fill and I have ended up with Fb within 1/2 hz when all was said and done. You can easily verify Fb with a simple impedance sweep. Just look for the lowest value between the peaks and that's it. The Fb I used was 55Hz. Box 4.5 cubic ft. Let me that was right. I will post both just for fun. You have to remember to change Vas to the correct value as it is wrong in the T/S table. The correct value is 427 liters. In BBP they come out to 3.06 inches long so 3" long longer in Win Isd at 5" I would defiantly use the BBP but you can always try both and do an impedance sweep for the actual Fb measurement. I assume you are crossing them at about 80Hz or so?

    Rob
    thanks Rob for your efforts and help / i'm in the process of putting on a high gloss black finish on cabinets now so it might be a little while again thanks

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    Quote Originally Posted by Robh3606 View Post
    Not sure I am the right Rob but I use E-145's in 5 cubic ft tuned to 40Hz and even though they have usable in room response to about 40Hz they are down quite a bit. You are going to need subs under them they just cannot do 25-60Hz like a 2235 or an Le-14-3 for that matter. Post the internal volume and I will run it in software for you and post the results.

    Rob
    I swapped out the E-145 for TAD 1602 with good results . so its tad 1602 2118 mid and the amt for the top i like what i here ,sounds promising . now i would love to get it all passive x-over any help ?

  10. #10
    Administrator Robh3606's Avatar
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    'I swapped out the E-145 for TAD 1602 with good results . so its tad 1602 2118 mid and the amt for the top i like what i here ,sounds promising . now i would love to get it all passive x-over any help ?"

    If you have it running in an active set-up and you like the way it sounds, measures well, you can use the active voltage drives as a starting point. You would probably need to tweak it with a set of measurements and crossover sims.

    To start from scratch you would need to measure the drivers mounted in the cabinet and use a crossover simulator for the rest.

    Have you tried to find any TAD designs that use that driver combo? That would greatly simplify things with a good staring point.

    Rob


    "I could be arguing in my spare time"

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    I believe the only passive crossovers that do exist for the TAD woofers are the 650hz-filters. These had been used in the 2-way monitors... But if I remember correctly, they run the TL-1601 and not TL-1602 unfortunatelly.
    But 650hz crossover-point should work great with 2118 as well. In the 4628 it is crossed at 800hz, right?
    Maybe you can modify the TAD-crossover from 650hz to 800hz...

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    Quote Originally Posted by Robh3606 View Post
    'I swapped out the E-145 for TAD 1602 with good results . so its tad 1602 2118 mid and the amt for the top i like what i here ,sounds promising . now i would love to get it all passive x-over any help ?"

    If you have it running in an active set-up and you like the way it sounds, measures well, you can use the active voltage drives as a starting point. You would probably need to tweak it with a set of measurements and crossover sims.

    To start from scratch you would need to measure the drivers mounted in the cabinet and use a crossover simulator for the rest.

    Have you tried to find any TAD designs that use that driver combo? That would greatly simplify things with a good staring point.

    Rob


    • Posted by Tre' (P) on October 5, 2013 at 17:00:22In Reply to: RE: YUP posted by Ed Schilling on October 5, 2013 at 09:34:08:

    "Well, I say "not in the signal path" because the Coil and cap are across the voice coils as a "shunt" (I guess is a [COLOR=#009900 !important]good word[/COLOR]) and not "in line" with the voice coils as in a parallel network. " Ed, the cap IS in series (in line) with the Heil and the coil IS in series (in line) with the 126.


    The red is the signal path for the HF and the green is the signal path for the LF.
    At 10000Hz the coil's reactance is 80 ohms while the Heil's is 3.7 ohms so the 10k flows through the Heil, not the coil.
    At 10000Hz the caps reactance is .8 ohms and the 126's is 8 ohms (or whatever it is) so the 10k flows through the cap, not the 126.
    At 100Hz the coils reactance is .8 ohms while the Heil is 3.7 so the 100Hz flows through the coil, not the Heil.
    At 100Hz the reactance of the cap is 80 ohms while the 126 is much lower so the 100Hz flows through the 126, not the cap.
    It's really just as simple as that.
    The cap is in series with the Heil and the coil is in series with the 126.
    The real advantage of a series [COLOR=#009900 !important]crossover[/COLOR] (as you have already said) is that changes in the impedance of the drivers does not change the FR.
    And that's a good thing.
    Peace.
    anyone understand the concept here ?

  13. #13
    Administrator Robh3606's Avatar
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    It's a simple 1st order series 6db crossover. That said I have never used them always parallel, every JBL crossover is parallel as are most others. With the Heil there would be no advantage because the impedance is so flat. With the woofers as an example you can just add a zobel in a parallel network to counter the inductance/impedance rise depending on the coils inductance and the crossover point.

    I have no experience with them so I can't really say anything beyond that.

    http://sound.whsites.net/parallel-series.htm

    Rob
    "I could be arguing in my spare time"

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