Newbie Needs Guidance with OHM Conversion

[ShadowDancer]

Hi All,

I'm a newbie with only a small bit of electronics experience - generally enough to be dangerous, which is why I came here to speak to some of the gurus.

My wife and I currently own a motorhome with a SONY DAV-DX150 HTS installed in it. As you can imagine, the speakers are installed by design so there is little room for me to be able to change them out. We purchased a Panasonic SC-RT50 HTS in the hopes of replacing just the main Sony unit and leaving all the speakers. As I opened the box and started reading the manual (imagine that) memories of my teenage years suddenly entered my head as I realized that I should have learned much more about ohms and wattages. So here's my question... is it possible for me to adapt (in some fashion) the new unit to the old speakers. Obviously, the wiring is fine, but the Sony uses a 3-ohm speaker setup on all of it's speakers and the Panasonic uses a 4-ohm speaker setup for all except the front speakers, which are 8-ohm. I realize that even if there is some way to adapt them, that the sound may change, but I figure that I would decide on that after I first got them to work. The good news is that everything is still in the box except for the manuals and the main unit, and I haven't even plugged the main unit in yet. I guess some wisdom still remains...

Thanks in advance for all of your assistance.

- ShadowDancer

 

[Ampdog]

ShadowDancer,

I am not familiar with either of the AV units you mention, so my reply will be rather basic. Firstly, the stated impedance of loudspeakers is nominal. It varies considerably with frequency; a typical "4 ohm" type might go from say 3 ohms to as high as 20 ohms. Bottom line: Although the Panasonic will theoretically be somewhat overloaded by a 3 ohm system, that should not worry it. Music has a rather low average energy level anyway, so it should not stress the system (unless you really belt the neighbours away, in which case the amps would get hot anyway).

With a front speaker spec of 8 ohms they will be audibly louder, however. This you can set, but driving 3 ohm speakers from an 8 ohm output might just stress the electronics somewhat, especially at high output. Are the front speakers full-range? If not a series resistance of some 3 ohms might be the answer. (Some will frown on that - damping factor and all that - but that does not matter in the case of mid-high frequency units.)

But I am sure you will get further advice from members perhaps familiar with your units.

Regards

 

[ShadowDancer]

Ampdog,

Thanks for your reply. The specifications state that the speakers are Bass reflex, magnetically shielded. Speaker unit is 65mm (2-5/8") dia cone type with rated impedence of 2.7 ohms. The speakers in the new Panasonic unit are 2-way, 3-speaker system. The Sony system (old) is 133W per front channel and the new Panasonic is 190W per front channel - I figured just as long as I didn't push the volume I would be okay. Fortunately I don't need the volume as loud as I once did and the physical area wouldn't permit it anyway. I can scan and provide further full specs if you would like.

Thanks for your time, Ampdog!

 

[JKnPA]

Why........... ???

Just curious............. why are you changing receivers?
You new system looks like a good 'in-home' unit!

 

[ShadowDancer]

Hi JKnPA:

A VERY reasonable question. The Sony is indeed a good system, although it is lacking any additional inputs and/or outputs for integration with other components.

As you probably know, in a motorhome, space is hard to come by. There is a limited amount of space that I can add AV components to an existing enclosure that already exists. We have already added a number of misc components (satellite receiver, Verizon Broadband router, WiFi router, music bridge, etc) and are close to maxing out the space, not to mention the heat geneated by these gizmos may become a consideration. We still have another item or two that we want to add, one of which is a DVD recorder. The Panasonic unit comes with an integrated DVD recorder and as such also a TV tuner which the Sony does not. It also has additional inputs and outputs for other components where the Sony has no additional I/Os- it has one effectively one input and one output, which is already reserved for use bythe TV as it is currently wired. So using the Sony it becomes a challenge to incorporate the music bridge. Also, the Panasonic has a front input panel including a digital input for converting movies from our movie camera directly to DVD. The Sony has topmounted control buttons which with the way that this setup was designed is simply a MESS -- you can't see what you are pressing so you in effect HAVE to use the remote. I'm 6' and STILL can't see them (even WITH my glasses! ) Next, all of the other AV components (TV's, other DVD player in the bedroom, etc) are Panasonic and it would be nice to just have one remote rather than 3-4 with the acquistition of a new DVD recorder.

I hope that you haven't fallen asleep by now while reading all of this. Probably no single reason could justify the change, but in bulk, at least to me, it is worth considering, although without a viable workaround to the ohms and powering issue, I may have to pout my way back to Circuit City to return it. I appreciate having the opportunity to type out all my reasons; somehow it was theraputic.

So that's the story. Still in a quandry as to what to do, although I must admit that some of the terms and the math is starting to come back to me with Ampdog's reply. Not enough yet, though, to go it alone. Forums are simply wonderful for reminding myself how much I do not know and/or have forgotten. It's a healthy and sometimes humbling experience and I am always grateful for those who take time out of their lives to help.

Thanks for your post. I feel much better now.

- SD

 

[JKnPA]

Right............

I did notice the 'Panny' was a DVD recorder, so I assumed you wanted that function in your motorhome, but then you have the speakers from the
'Panny' doing nothing!
I was surprised to see that your Sony speakers are only 3ohms. I didn't think 'HTIB' units went that low?????
* Its always good to refresh our memory, and realize how much we have forgotten. I browse thru some of my 'tech'. books I had in college and wonder how I made it thru those courses now...........
** I find the 'crossover' (filter networks) circuit interesting and how they apply to the speakers being used. I never worked much with filter networks in my old job, so its all pretty new to me!

Good luck.....