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Old 19th October 2018, 05:32 PM   #11
GM is offline GM  United States
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Quote:
Originally Posted by civil6 View Post
Thanks. The sub, satellites and receiver are rated for 8 ohm oper.

I'm pretty sure I don't need a "sub plate amp." I will reconnect using both speakers L/R into passive subwoofer terminal plate.

I find "powered" subwoofers overkill (way too much unused power)when using small satellites in my room.

Lastly, Should I be using a 4 or 16 ohm sub driver in order to "save" my receiver?
You're welcome!

The main point is that the sub must be electrically isolated from the stereo mains to not only perform correctly, but protect each component in the signal chain against a potential catastrophic meltdown if the house supply doesn't adequately protect the audio system from itself. A very real possibility depending on the house wiring, age, etc.. Worst case you could potentially have a house fire in the making if the receiver's fuse/whatever protection fails in some way to shut it down quickly enough.

If no plate amp, which has an adjustable XO, then as adason noted, some form of outboard XO is required.

The higher the resistance, the lower the current draw, so normally going higher is better IF the source [amp] is designed/rated for it [unlikely with modern mass market electronics]. Resistance sums in series, i.e. 8 + 8 = 16 ohms: https://www.electronics-tutorials.ws/category/resistor

Regardless, with a proper XO to isolate the mains from the sub, then the amp will 'feel' all three driver 'systems' independently of each other and now just a matter of whether the amp can provide sufficient power based on the position of the volume control, making you the primary protection 'circuit' .

GM
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Old 19th October 2018, 07:08 PM   #12
phivates is online now phivates  United States
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Does your passive sub terminal plate have two pairs of connectors or just one?
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Old 19th October 2018, 07:52 PM   #13
GM is offline GM  United States
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??? I looked for this earlier, but got no images, so do they really exist?

Anyway, for any future type of Qs, a basic primer I forgot to post earlier: The Difference Between a Passive and Powered Subwoofer

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Old 19th October 2018, 08:09 PM   #14
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Keep in mind that the folks offering this advice have been playing this game for quite some time - in some cases over 50 years. In short, you need to isolate/separate the frequencies over which the “sub” will be operating from the mains/satellites, as well as to combine the two channels to mono if the XO frequency is below the point at which localization would be a problem.

As has been suggested several times, the most practical method to achieve that and safely power the total system would be a separate dedicated amp channel for each woofer. Note that not all sub amps are “plates”, but those types often offer features that are specifically designed for cases exactly like you’re describing to us. Of course, you could also build a speaker level passive crossover to achieve the same results, but you’d still lack the ability to adjust the level of woofer to most seamlessly blend with the mains, and at the frequencies at which subs are generally rolled in (below 100Hz), I’d dare say that the cost of passive components for a stereo 2-way XO could make a plate amp much more attractive - particularly if attentuation is required if the woofer has higher sensitive than the mains.
There are several plate amps to choose from at Parts Express for less than $100 USD. Granted, it’s been quite a few years since I played with plates, or deeply dived into their spec sheets, so maybe another member could make a specific recommendation for some with High Pass foliters on the mains - a feature I’m sure I’ve seen in the past, but that would have been probably 10yrs ago.
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Old 19th October 2018, 08:29 PM   #15
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Greg - the Dayton SA230 cited in your linked page looks like a nice piece. I’d been quite happy with a pair of mono-ed APA150s driving dual subs in HT, as well as MA1240 running background music system in a restaurant for almost 5 yrs now without a glitch.
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Old 20th October 2018, 11:42 AM   #16
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I'll stay w/ passive sub. Thanks.
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Old 20th October 2018, 05:36 PM   #17
Lingwendil is offline Lingwendil  United States
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No Visible Cone Movement @ Startup
Quote:
Originally Posted by civil6 View Post
I'll stay w/ passive sub. Thanks.



Why not grab a 10$ class D module to run the sub? Even 20-50 watts is plenty if you're running it passive now it'll be a huge improvement.


Any passive solution will be wrought with compromise and may even damage the internal amplification.
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Old 20th October 2018, 07:23 PM   #18
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Randy - have you yet to research either the link offered by GM, or the subject in general? All the advice so far has been trying to impart that there’s more going on than just “load balancing” due to the nominal impedance and sensitivities of the drivers involved.

Even though you’ve only described a single sub, what you’ll be ending up with when successful is a two way system, in which the overlap between drivers operating at different bandwidths is generally kept to a minimum. I’m quite familiar with the FE127, and have used it full-range - i.e. with no high pass filtering - as well as assisted with powered subwoofers. Even though the 127, or any of the many models of Fostex I’ve played with over the years can be operated full range, there are definite benefits to be gained from high-passing them when adding woofer/subs.


Whether as “plates” for including in existing cabinet, or in separate chassis, all sub amps include at the minimum adjustable low pass filters and level controls - both essential features to smoothly integrate the additional bass energy into the system. Absent such low pass filtering, even if balance between main channels is some how achieved, you’ll almost certainly be getting a substantial amount of overlap between the mains and the sub, up to the top end of the latter’s frequency response. Many of the drivers designed for sub use may extend well into the lower mid-rannge, but not always with smooth response. Can you see where this is leading?
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Old 20th October 2018, 08:13 PM   #19
JMFahey is offline JMFahey  Argentina
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Originally Posted by civil6 View Post
Thanks. The sub, satellites and receiver are rated for 8 ohm oper. This is the 1st time I've wired in only (1) speaker to this sub in my stereo setup. The 12" sub speaker is draining power to the 4" Fostex? Makes sense. Power goes to sub spkr. before sat., and...no or little cone movement. I never considered it, however. That's why I asked. I'm pretty sure I don't need a "sub plate amp." I will reconnect using both speakers L/R into passive subwoofer terminal plate. I find "powered" subwoofers overkill (way too much unused power)when using small satellites in my room. Lastly, Should I be using a 4 or 16 ohm sub driver in order to "save" my receiver? Thanks to all respondents. I am obliged.
You can NOT repeat NOT do that.

Yoiu can NOT connect two amplifier outputs to a single speaker.

The "passive plate" you mention is basically a crossover, but meant to connect one amplifier to two speakers (woofer and satellite) , you are trying to do the exact opposite, and of course it won´t work.
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Old 20th October 2018, 11:03 PM   #20
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So, it also appears you’ve not yet taken your own advice from the Oct 27 /17 post in the Blue Plate Special thread in subwoofer forum.
The voices you’re now hearing are mumbling - “sooner or later”, or “horse to water” , I’m not sure.
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