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Help with a 2-way monitoring system in a concrete box

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  • #16
    I got one of those (cheap-ish) SURE 4x100 boards a couple of years ago, and like it a lot.
    The sound is really very clean, but I have not pushed it hard.
    For use with a DSP active crossover, it's darn near perfect.

    I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
    "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

    High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
    SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
    My Voxel min sub Yet-another-Voxel-build

    Tangband W6-sub


    • #17
      Are you planning to fabricate the concrete enclosures? I have seen plans for enclosures that were based on concrete blocks with the center partition chiseled out, or on chimney flue tiles with wooden endcaps on either of these. Just something to consider. Volume can be reduced if too large by putting in wooden blocks or bricks to take up space if needed.


      • #18
        I plan on making a "negative" of the shown design with something like melamine and the inside cavity out of styrofoam for ease of demolding. I still haven't decided on the thickness tho, and certainly I could use wood inside to reduce the weight

        A list of the parts planned for the build:

        2 x Fountek Neo X 2.0 Ribbon Tweeter Black--------------------------------------------------------------------------------------(2 x $86.80 each)

        2 x Dayton Audio RS150-8 6" Reference Woofer----------------------------------------------------------------------------------(2 x $39.45 each)

        1 x MiniDSP 2 x 4 Kit------------------------------------------------------------------------------------------------------------------------($80)

        1 x WONDOM AA-AB33182 4x100W at 4 Ohm Class D Digital Audio Amplifier Board STA508 (TK2050)------($55.98)

        1 x Mean Well MW LRS-150-24 24 VDC 6.5A 150W Regulated Switching Power Supply with Power Cables-($22.90)

        1 x Acousta-Stuf Polyfill Speaker Cabinet Sound Damping Material 1 lb. Bag------------------------------------------($11.62)

        1 x Parts Express Gold RCA Jack Solder Type with Nut Pair-----------------------------------------------------------------($2.39)
        For the Input to the MiniDSP

        8 x Dayton Audio BPA-38G HD Binding Post Pair Gold-------------------------------------------------------------------------(8 x $5.00 each)
        2 pairs for each speaker (tweet and woofer inputs for each box) and a pair for each output of the amp

        2 x Banana Speaker Plug 2 Pair---------------------------------------------------------------------------------------------------------(2 x $9.95 each)
        For the wire ends

        1 x RCA AH1450SR 14 AWG Speaker Wire Spool 50 ft. -------------------------------------------------------------------------($14.41)
        for the speaker wire, Could I use a 16 gauge wire? and would this wire work for the power connections?

        1 x Dayton Audio EMM-6 Electret Measurement Microphone ----------------------------------------------------------------($45)

        Total of: ------------------------------------------------------------------------------------------------------------------------------------------- $544.7

        I understand the total power in watts RMS would be : 2x25w for the tweets and 2x40w for thw woofs for a total of 110W RMS needed from the amp, so the power supply would be perfect as well right?

        how would I go about including a subwoofer for the system??

        One last question, What would be a good wire to use for the connections to and from the MiniDSP? regular RCA cables?? what if I use the 14 gauge wire??

        Sorry for asking this many questions.
        Last edited by Antares; 11-24-2018, 06:47 PM.


        • #19
          150 watt smps is too small for the 4x100 board, order the 350 watt smps. You can also buy buck convertors off ebay for super cheap, use them to drop the voltage and run the minidsp off the smps which eliminates another power supply in the system.

          If you're wanting to cut costs, use the cheap rca cables to connect the mini. You can also use zip cord for speaker wire, and pillow stuffing or plain ole fiberglass house insulation (do not get fiberglass everywhere or you will pay!) in place of acoustic stuffing.

          Including subwoofer ... what are you feeding signals to the mini with? If it's a ht receiver it should have separate pre-outs for the sub. If it's a two channel preamp then you may have to use a spliter before the mini. If using a splitter it would be easier to go with a powered sub otherwise you will need a sub amp, a way to eq the sub (if you so desire) plus the sub itself.


          • #20

            This is the rs150p-8a in 10L. (.35ft³), I'm thinking it will model close to the rs150-8. This is the best I could do with 10L., keep in mind others here are a looooooot better at this than I.

            Sealed 10L.

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            Vented 10L. @ 56hz. If you tune higher you will start seeing a rise in the upper bass, some people prefer that, some don't.

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            • #21
              Kornbread I have to thank you for your help kind sir.

              ok so I will use the 350 watts smps,

              please excuse my ignorance, but on specs it says the MiniDSP is rated to run between 4.5 and 24VDC so wouldn't I just plug it to one of the power outputs and be done with it?? why using a buck converter?? would it be safer for the minidsp??? I undertand that a device will only use the amps it needs to run even if there are more on the supply right??

              I will use either a Focusrite Scarlett Solo interface with RCA LR outs or a Dj mixer (Traktor S8 from Native Instruments) with Master RCA LR and Balanced XLR LR outs

              And would you consider a better option designing a ported enclosure? as I would like the bass extension.

              and well it would take perhaps a year of me saving up again to get the woofer included in the system plus I think the speakers deserve a decent sub system.

              ohhh and I'm aware the MiniDSP comes with a volume control pot control, Could I use it as the main volume pot for the whole system??

              The idea is building an eternal concrete enclosure for the circuits as well, to keep the theme consistent.

              Already looking for subs...

              This post will continue on the Speakers Project Gallery in the near future. And thanks again to the amazing community here at parts express, would definitely recommend and help in any way I can.

              Heres a model of my bedroom.
              Click image for larger version  Name:	Room.png Views:	1 Size:	44.6 KB ID:	1394866
              my room is 3m L , 3.2m W and 2.2m H that is around 9.8 ft L, 10.4 ft W and 7.2 ft H

              The speaker would be place near where the cylinders are on a wooden or steel stand.
              Last edited by Antares; 11-24-2018, 09:37 PM.


              • #22
                Originally posted by Antares View Post
                Kornbread I have to thank you for your help kind sir.

                ok so I will use the 350 watts smps, but the MiniDSP is rated to run at 24VDC so wouldn't I just plug it to one of the power outputs and be done with it?? why using a buck converter?? would it be safer for the minidsp???

                And would you consider a better option designing a ported enclosure? as I would like the bass extension.
                No kind sir here, just a dirty ole man. Ask my wife.

                Darn, I never realized the mini could run on 24 volts. There are things you can do with the mini that are hard to do otherwise. To control excursion in the bass you could place a low shelf starting around say 40hz. Basically it acts as a low freq high pass for the woofer.

                7L. ported (.25ft³) Man that seems tiny ...

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                I don't always do things the right way and wonder about going to .5ft³ (14L.), or larger. With an Fb of 52hz and an F³ of 48hz it's not going to take a lot of power but using a low shelf in the mini and dropping output like a rock after ~40 hz might help just enough to make the trade off worthwhile. That's going to be a bit larger than the .3-.4 you originally planned for but might be enough bass to satisfy needs till the subwoofer gets built.

                Click image for larger version

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                Guys, am I going in the right direction with this?



                • #23
                  I don't have enough words to thank you Kornbread , mostly because I have English as a second language, hahaha.

                  and we might all be dirty but we can all be kind.

                  What about using a larger size woof, say 7" or 8" and have a better low end response, would it be a big issue on a room my size?, keeping in mind that eventually sooner or later I'll move? to a larger space hopefully...

                  Edit: Using a larger size woof might work for the project as the 7" 4 ohm reference is rated for 60W RMS-120W max, as for the paper cone 7" 4 ohm one is rated at 60W RMS-90W max.

                  and if it's a big issue controlling via DSP to correct for the issues of the room size, what about a 4 ohm 6" reference driver?

                  Used the parameters you show to compare with WinISD and here are the graphs. for a 4 ohm 6" reference driver.

                  14L - tuned at 47Hz - F3 46Hz -

                  Using a 2nd order HP @ 40Hz to prevent cone excursion as suggested and

                  a Parm EQ band @ 88Hz with 1dB gain and Q=0.9 to flatten

                  and 1W on the system input power on the signal tab on WinISD (which worries me)

                  Click image for larger version  Name:	Ported 6' Reference.png Views:	1 Size:	104.8 KB ID:	1394881
                  With the filters deactivated

                  Click image for larger version  Name:	Ported 6' Reference Filter off.png Views:	1 Size:	104.4 KB ID:	1394882
                  Excursion at 1W

                  Click image for larger version  Name:	Ported 6' Reference Cone Exc 1w.png Views:	1 Size:	112.1 KB ID:	1394883 Cone excursion at 10W

                  Click image for larger version  Name:	Ported 6' Reference Cone Exc 10w.png Views:	1 Size:	113.2 KB ID:	1394884 Excursion at 20W

                  Click image for larger version  Name:	Ported 6' Reference Cone Exc 20w.png Views:	1 Size:	109.7 KB ID:	1394885

                  I have an important question how do I make sure the amp board delivers say 1W or 1.8V and not any other Wattage?? Since I input 20W on WinISD and it already passes the excursion limit with these settings, and I know I won't be using the woofs nowhere close to 10W but how do I properly set the gain or the volume adjustment knob so the max output is say 8W/5v when measured on a multimeter??

                  Would this be set up using the DSP?? as in just lowering the volume to a channel or similar???
                  Last edited by Antares; 11-25-2018, 02:03 AM.


                  • #24
                    Unfortunately the discounts are no longer shown on the website :c

                    even tho it said until 25/11/18 :c

                    opened the black friday coupon page and still up, hopefully promo still applies....


                    • #25
                      While there are woofers larger than 6" that should play high enough in frequency to mate well with the 2.5-3k handoff point, as a general rule of thumb, the larger the woofer the harder it is for it to play higher in freq before breakup. Not to mention center to center distances between drivers (what about dispersion characteristics guys?) that's why donradick . suggested those ~5" woofers.

                      You can move the speakers around in the room till you find the place they sound best.

                      I am not familiar with prosound gear.

                      Nor did I realize the mini had a volume control. Maybe I need to read more instructions.

                      Another driver I have worked with that might be good in this situation is the FaitalPro 5fe120. IMO, having both the 5fe120 and rs150 in current speakers I'd say the 5fe120 has a much smoother sound while the rs150 is more the analytical type. The 5fe120 is easy to work with and seems to dig deeper in the bass before giving up. Hate the cheap stamped frame the 5fe come with though.

                      Stop worrying about wattage.

                      This is the 5fe120 with xt25.

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                      • #26
                        These 5fe120, Do have a higher and relatively flatter Fr above 1kHz before breakup

                        And I know I should not worry about wattage but, wouldn´t these be underpowered with the chip amp I plan on using? as they are rated for 80W RMS?

                        Sorry if I am misunderstanding all the wattage situation. and yes they seem to be a better fit for the project.

                        For future reference where can I find further info on wattage and speakers, a ton of info online is really that helpful in this subject.

                        Here's a list with the chosen parts for the project. trying to get as close to $500 as possible.
                        • 2 x Fountek Neo X 1.0 Ribbon Tweeter Black ------------------------------------------------------------------------------------------($78.90 each x 2 = $157.80 )
                        • 2 x FaitalPRO 5FE120 5" Professional Midbass Midrange Woofer 8 Ohm ---------------------------------------------------($40.00 each x 2 = $80.00)
                        Edit: now thinking of using the Tang Band W4-1720 4" Underhung Midbass Driver as donradick first suggested at $55.79 each. = $111.96. I wish I had the extra for the Esoteric dayton's tho :c
                        • 1 x MiniDSP 2x4 Kit Digital Signal Processor Assembled Board ---------------------------------------------------------------($80.00)
                        • 1 x WONDOM AA-AB33182 4x100W at 4 Ohm Class D Digital Audio Amplifier Board STA508 (TK2050) ---------($55.98)
                        • 1 x Mean Well MW NES-350-24 24 VDC 14.6A 350W Regulated Switching Power Supply ------------------------------($35.97)
                        • 1 x Dayton Audio EMM-6 Electret Measurement Microphone --------------------------------------------------------------------($45)
                        I will use binding posts for each driver, so 2 pairs per speaker and RCA ins for the DSP
                        • 4 x Dayton Audio BPA-38G HD Binding Post Pair Gold-----------------------------------------------------------------------------(4 x $5.00 each x 4 $20.00)
                        • 4 x Dayton Audio BPA-38G HD Binding Post Pair Satin Nickel-------------------------------------------------------------------(4 x $5.00 each x 4 $20.00)
                        • 1 x RCA AH1450SR 14 AWG Speaker Wire Spool 50 ft. -----------------------------------------------------------------------------($14.41)
                        • 2 x Banana Speaker Plug 2 Pair-------------------------------------------------------------------------------------------------------------(2 x $9.95 each = $19.90)
                        • Total: -------------------------------------------------------------------------------------------------------------------------------------------------$529.06
                        • Total with the Tang band's --------------------------------------------------------------------------------------------------------------------$561.02
                        I would really appreciate if someone tells me if I'm missing something or if I should change anything on the list.
                        Last edited by Antares; 11-25-2018, 01:19 PM.


                        • #27
                          added this last post to confirm I will make the purchase with the Tang Band drivers. and to confirm that at the moment of this post I got the discount available to me during Black Friday 2018. total of $492.28 with the $50 off applied.

                          Thanks a lot for your help.


                          • #28
                            The umm6- usb mic will plug into your usb port and gets its power from there. Very convenient for getting measurements.

                            Binding posts and plugs can add up quick. Monoprice has the cheapest bananas I've found.


                            • #29
                              I forgot to mention that I have a focusrite audio interface with phantom power, that's the reason I listed the EMM-6 XLR.

                              and damn they sure add up, 40 dollars in posts :c

                              But I couldn't see a better way to connect the speakers, as I intend to place these inside the mold before pouring the concrete, or I could build a mesh and spread a really dry concrete mix as well instead of using a poured mold.

                              Would the concrete cab be a good Idea after all?? or should I stick with what's been proven to work?? MDF most likely.

                              If I don't jump into the the water I would never learn how to swim right???