Wiring Surround Sound Speakers - In Series or Parallel?

[Bonzo]

So just yesterday I purchased some used older model Definitive Technology BPVX speakers from E-Bay. They were the once upon a time top of the line surround style speaker from Def Tech, and they were made to match my mains both using the 6-1/2” cones and 1” tweeters. Assuming all goes well and there is nothing wrong with them, my plan is to add them to my existing theater system as side surrounds. I will then have a 7.1 channel system using 9 speakers and 2 subs. When I originally bought my current speakers in 2006, I didn’t have the funds ($1400) to buy these top of the line BXVP’s, so I went the best I could with the BP2Xs ($450). Later when Def Tech was closing these out, I bought 2 more BP2X’s to get me up to 7.1.

Now, for those who like to know more details, first a little history (Skip down the Real questions if you don’t care).

When I set up my BP2X 7.1 arrangement, I placed the surround speakers where I did for several reasons. First, the back wall ones were in the existing 5.1 location, and there isn’t any flexibility there, so they stayed. When I went to put up the new side wall ones, I had a few options, so I made stands and tried out different formations to see what I liked best. Def Tech recommends ½ way between the listening position and the back wall, while Dolby says 90 to 110 degrees behind the listening position. When listening to both placements, I did hear differences, so I needed to make a decision. The thing is, for TV, I do have the Dolby IIx processing, so even 5.1 stuff gets bumped up to matrixed 7.1. But for Blurays & DVD’s, since I have my player hooked up via 7.1 analog (not HDMI, which my receiver does not have), that processing (in my current set up) doesn’t work. The receiver doesn’t apply any processing to the 7.1 analog inputs. So if a Blu-ray or DVD is only 5.1, that’s all I get, 5.1. When I listened to 5.1 with the side surrounds half way back like Def Tech recommended, it was great. But when I listened to them where Dolby recommends, they were way to “up front” and discernible in the mix, and more, the entire back half off the room was missing the full sound it had before. I liked them up front okay when it was either Dolby IIx 7.1 from TV, and really liked them there for Dolby True or DTS Master 7.1, but not Blu-ray / DVD 5.1 only at all. So for placement I compromised and stuck with the Def Tech recommendation.

Fast forward to now and the future.

My future plan is to upgrade to using height channels such as Dolby Atmos and/or DTS:X. The current idea is to get an XMC-1 with these functions when it becomes available (which will also add the Dolby IIx to all incoming signals via HDMI so I don’t have to live with the 5.1 only issue anymore). But my current surround speaker placement isn’t ideal for height channels to be added to the mix. The rear height channels need to be sort of in-between the rear and side surrounds, and to get proper separation, there needs to be some space between them. My current set up does not allow for this.

I could just move my current side surrounds forward when I decide to switch and be done with it (although that would involve patching outlet sized holes). But, now, since the side surrounds will be much more “in the listeners ears” so to speak, I figured it would be cool if the side surround speakers got upgraded, preferably to something that would tonally match my mains even more closely than before. The BPVX is that ultimate matching surround speaker in my Def Tech system. So I bought some the only way I can anymore, used. I got them for about $520 ($1400 original price) so we’ll see how it goes. Finally, I figure using 4 speakers for the back can only help increase the back soundstage which can be somewhat limited in a 7.1 system. All should be good.

Now to the real questions regarding wiring in series or parallel.

If I want to use my existing XPA-5 amp to power all 7 theater speakers (Center channel and 6 surrounds), and not use my receiver at all (since I’m planning to swap this out once the XMC-1 has height channel capability), then for now I think need to consolidate 2 of the 5 channels to run the 4 back surround speakers. (1) 200 wpc for the center channel, (2) 200 wpc channels for the (2) new BPVX speakers, and then (2) 200 wpc for the (4) BP2Xs. (Of course when I make the jump to also having 4 height channels, then I will need to buy a new amp to cover that in some fashion).

To do this I can either wire the 4 back surrounds in series or parallel. From what I have read so far, both have some advantages and disadvantages. For my application, I’m leaning towards using the parallel method for a few reasons, and I’d like to know if the technical folks here think all will be okay to do so.

First, parallel is much easier to wire in my situation. The wires are all there in the walls, connected at the speakers, and the amp end connections are readily available. All I would need to do is combine the 2 right side red wires into one banana plug, and the 2 right side white/black wires into the other banana plug (and do the same on the left side), then stick them in one of the amp channel outputs. Sort of like making homemade bi-wiring. Compared to rewiring for series, this would be super simple.

Second, if / when I add an amp for the height channels in the future, this would allow me to easily disconnect this set up and go right back to using dedicated channels for each speaker (like buying a 6 channel amp perhaps).

QUESTIONS:
- Will running the (1) center channel and (2) side surrounds (both 8 ohm loads) simultaneously with (4) identical back surrounds (both 4 ohm loads) hurt the amplifier, or speakers, or have any other negative resistance related affects?
- Do my speakers present any particular problems doing this, or should they be just fine?
- Would running in series instead have any real positive upsides to make me go through all the extra effort to do it?
- What volume changes should I expect due to parallel wiring? I know I will have changes based on having 2 rights and 2 lefts and their placements.
- Do you have other recommendations other than what I am planning?

Here are the specs of all 3 speakers being used.

(1) Existing C/L/R 3000 for Center Channel
Tweeter = (1), 1” Aluminum Dome
Midrange = (2), 6-1/2” Cone
Woofer = (1), 10” Cone (driven with built in 150 wpc amp)
Sensitivity = 91 db
Frequency Response = 45 Hz – 30 kHz
Nominal Impedance = 8 ohm
Recommended Cross Over Setting = Large Full Bandwidth
Power Handling = 20 – 200 wpc
Dimensions = 8-5/16” tall, 25” wide, 16” deep

(2) New BPVX for Side Surround
Tweeter = (2), 1” Aluminum Dome
Midrange = (4), 6-1/2” Cone
Sensitivity = 90 db
Frequency Response = 31 Hz – 30 kHz
Nominal Impedance = 8 ohm
Recommended Cross Over Setting = 40 Hz
Power Handling = 20 – 400 wpc
Dimensions = 22-1/8” tall, 11-3/8” wide, 7-3/4” deep

(4) Existing BP2X for Back Surround
Tweeter = (2), 1” Aluminum Dome
Midrange = (2), 5-1/4” Cone
Sensitivity = 90 db
Frequency Response = 45 Hz – 30 kHz
Nominal Impedance = 8 ohm
Recommended Cross Over Setting = 80 Hz
Power Handling = 10 – 200 wpc
Dimensions = 14-1/2” tall, 9-13/16” wide, 5-15/16” deep

Attached is a picture of my room layout and the plan. My old 5.1 set up only had the surrounds on the back wall labeled as SB2 and SB4 in this diagram. The current 7.1 set up has the 2 side surrounds labeled as SB1 and SB3 in this diagram.

Thanks in advance for any and all help you can provide with this.

Cheers ---- Bonzo

MEDIA ROOM 2.pdf (15.65 KB)

[mv]

Wire your speakers in parallel. Your amp will see a 4 ohm load, which is perfectly fine, and your speakers will receive roughly 150WPC. If you are using your Denon 3805, it has pre-outs...so you could run the two side channels off your XPA, and then your two back channels off your receiver. In a 7.1 setup, there will not be much difference in audible volume between what your receiver can put out, and the power your amp will make. Then you can still keep 7.1 channel sound instead of going back to 5.1 channel.

[Bonzo]

KeithL, any thoughts on this? I'd rather not hurt my speakers or my XPA-5.

Thanks ---- Bonzo

[KeithL]

Your XPA-5 will happily run 4 Ohm or 8 Ohm loads.......  so........

2 x 8 Ohms IN PARALLEL = 4 Ohms = just fine
2 x 4 Ohms IN PARALLEL - 2 Ohms = too low (the amp should work, but it might overheat, so not a good idea)
2 x 8 Ohms IN SERIES = 16 Ohms = OK (the amp won't mind a bit, but you'll get less output that way)
2 x 8 Ohms IN PARALLEL = 4 Ohms = just fine (you'll get the most power from the amp that way and have no problems).
And, if you put two IDENTICAL speakers in series or parallel, the power WILL divide evenly between them.

So, if you've got two 8 Ohm speakers then you should parallel them, and, if you've got two 4 Ohm speakers you should series them.
(Note that we've been talking PER CHANNEL here....
Feel free to mix 4 Ohm and 8 Ohm loads on different channel..... as with most amps, you'll get more power with 4 Ohm loads, but the amp will run slightly warmer...

Also, when you put two of the same speaker in series or parallel, other than the difference in impedance, they should act pretty much like one speaker.
And, when you put two different speakers in parallel, they'll each act the same as they do separately (but both added together).
HOWEVER, if you put two dissimilar speakers in series, you can end up with odd results because they interact...... (It may be fine or it may end up sounding slightly funny.)
If you put two dissimilar speakers in series OR parallel, the power will NOT divide equally between them.
In general, if you put two speakers playing the same thing next to each other they add together, which results in a slight increase in perceived loudness, but not usually as much as you'd expect.

As you've noted, from a wiring point of view, running a wire from each speaker separately back to the amp is the best choice.
That way you can wire them in parallel, or you can wire them in series, and you can change your mind later.

Oct 24, 2016 11:59:13 GMT -5 Bonzo said:

KeithL , any thoughts on this? I'd rather not hurt my speakers or my XPA-5.

Thanks ---- Bonzo

[Wideawake]

Boy, you've gone and made a mess of things, haven't you.

Let your Denon handle the new side speakers since they are 8 ohms. Your XPA-5 can handle the L/C/R and the 4 rears hooked up in parallel for a 4 ohm / ch load on the rears. You will not damage the amp or the speakers.

[Bonzo]

Thanks guys. Looks like I have a few options that work so I will consider my options and go from there. Speakers are on schedule to show up tomorrow so first things first.

[Bonzo]

Oct 24, 2016 13:52:13 GMT -5 KeithL said:

Feel free to mix 4 Ohm and 8 Ohm loads on different channel.....

Perfect. This was one of my main concerns. If I decide to run everything off the XPA-5, then I'll have 3 channels with 8 ohm loads and 2 channels with 4 ohm loads. As long as that isn't a problem than I'm golden.

Thanks for the detailed answer.