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Helium - a true micromonitor

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  • mga2009
    replied
    thanks scott! will add another two. regarding the port tube, can i make it in a different ID and modify the lenght? i couldnt find 19mm ID sch40 tubes in my country. regards Sent from my ONEPLUS A3000 using Tapatalk

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  • scottsehlin
    replied
    You need 4 of the 2.7uF caps. Everything else looks right.

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  • mga2009
    replied
    Just got the drivers and now I am buying the parts for the 8ohm crossover @PE.-

    Any final recommendation aimed to improve SQ is welcomed!

    Picture is the ND91-8 compared to the Dayton DS135-8 for a Matt Grant's Nexus TM. ND16-FA tweeter not shown.

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  • howey
    replied
    I'm intending to build these but to also incorporate a small sub and use the Sure electronics combination of JAB2 and JAB3 with DSP in 2.1 config to drive the whole thing. I can use the DSP to cross from sub to heliums. I'm just wondering if I need to do anything to adjust the passive crossover in the heliums to account for the DSP filtering the lowest frequencies away?

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  • scottsehlin
    replied
    I've only put resistors in series during prototyping, but it won't hurt anything. A 3 ohm 10 watt resistor will also work, I chose the 5 watt because it was smaller.

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  • mga2009
    replied
    Originally posted by scottsehlin View Post
    The driver spacing for the soundbar is close to the same as the original Helium, so it should work fine. The 8 ohm version of the ND-91 has a slightly larger optimal cabinet than the 4 ohm, but as a result can play a little deeper. The soundbar has isolated chambers for the left and right channel that would be 4" wide by 4.75" deep by 9" tall as stand-alone speakers. You could flip that around and make them 4" deep by 4.75" wide by 9" tall. The port for the soundbar is 3/4" schedule 40 PVC, 4 inches long.
    Scott,

    Thanks for your reply. Very clear explanation.

    Regarding the XO and the 3ohm resistor, I remember from school that if I install them in series they sum up the individual resistance, but I don't know if this will affect negatively on the SQ or any other spec of the speaker design.

    Thanks!

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  • scottsehlin
    replied
    The driver spacing for the soundbar is close to the same as the original Helium, so it should work fine. The 8 ohm version of the ND-91 has a slightly larger optimal cabinet than the 4 ohm, but as a result can play a little deeper. The soundbar has isolated chambers for the left and right channel that would be 4" wide by 4.75" deep by 9" tall as stand-alone speakers. You could flip that around and make them 4" deep by 4.75" wide by 9" tall. The port for the soundbar is 3/4" schedule 40 PVC, 4 inches long.

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  • mga2009
    replied
    Jeff, Scott,

    Thanks for your replies.

    Scott, so I just need to use the crossover design for the "Helium Soundbar" in the Helium standard cabinet. Regarding the XO, I noticed the 3 Ohm 5w resistor is no longer in stock in PE. Can I just use a 1Ohm and 2Ohm in series? Also, is there any chance to change the dimensions on the cabinet, keeping the internal volume (and the components location in the baffle)??
    I need them a little bit shallower and taller to get them behind my couch.
    Last edited by mga2009; 07-16-2018, 10:32 PM.

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  • scottsehlin
    replied
    Since I modeled that crossover, I voiced the Helium soundbar, which uses the 8 ohm version of the ND-91. The crossover will work for the Helium cabinet.

    Designer: Scott Sehlin Project Category: Home Theater Project Level: Intermediate Project Time: 8-20 Hours Project Cost: $100 – $500 Project Description: The Helium Soundbar is a DIY soundbar…

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  • Jeff F.
    replied
    Originally posted by mga2009 View Post
    Hi,

    These are 4ohm, correct?

    I am looking a set of satellites/surround to use my AVR, but I need 8ohm (6ohm at best) and found these while looking for JB's Quarks.
    The original design is 4 ohms. If you want to build the 8 ohm version see post #236. It has a revised crossover.

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  • mga2009
    replied
    Hi,

    These are 4ohm, correct?

    I am looking a set of satellites/surround to use my AVR, but I need 8ohm (6ohm at best) and found these while looking for JB's Quarks.

    Leave a comment:


  • Jake
    replied
    Originally posted by davidroberts View Post
    I have read through the tread and found several mentions of a MTM version. Does anyone know if these ever came to fruition?
    I actually Pm,d  Scott this very question recently. He said he hasn't done it, and referred me to page 7 of this thread as a starting point.

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  • davidroberts
    replied
    I have read through the tread and found several mentions of a MTM version. Does anyone know if these ever came to fruition?

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  • Matt Clara
    replied
    Made some progress...
    https://i.imgur.com/2jQsYRn.jpg

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  • scottsehlin
    replied
    Originally posted by tktran View Post
    To give more room for the crossover, could one of the new ND series passive radiators be used? Which model do you recommend, and how many (1 or 2) per cabinet?
    I would go with MattP's approach in his recently published "Passive Aggressives". It uses the ND91-4 and the same cabinet with dual ND90PR's. Matt indicates he added all of the included tuning weights to get to his low 60's tuning.

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