Biwired Speaker Load

[kevint]

I have a pair of Sound Dynamics RTS 7 floorspeakers.They are biwireable and have one tweeter with a crossover and 2 X 5" drivers with a crossover. My question is if I put both cabinets together and parallel wire all 8 binding posts will I have a two ohm load even with the crossovers?
I built a box to use this as a centre channel and wired it series parallel figuring that it would be an 8 ohm load. It sounds ok but I have to crank up the DB and EQ to max. on the receiver to match the level of my fronts. I did try it wired parallel for a minute and it sounded much louder.
Any other wiring suggestions?

 

[TLS Guy]

I have a pair of Sound Dynamics RTS 7 floorspeakers.They are biwireable and have one tweeter with a crossover and 2 X 5" drivers with a crossover. My question is if I put both cabinets together and parallel wire all 8 binding posts will I have a two ohm load even with the crossovers?
I built a box to use this as a centre channel and wired it series parallel figuring that it would be an 8 ohm load. It sounds ok but I have to crank up the DB and EQ to max. on the receiver to match the level of my fronts. I did try it wired parallel for a minute and it sounded much louder.
Any other wiring suggestions?

Bi-wiring will not change speaker impedance, or anything else for that matter. If you wire the speakers in parallel Bi-wired or not, the amp will see a 2 ohm load, which I would not recommend. Series wiring will significantly lower the sensitivity. I don't see how you can wire two speakers series parallel, that does not make sense. Forget the bi-wiring. From your description you have the choice of wiring in parallel or series and have a choice of 2 or 8 ohm.

By the way what you are doing is a bad idea. One speaker for the center channel will be best. By using two speakers you are going to have response irregularities due to comb filtering and lobing issues. Also you will not get more spl with series wiring, which is your only option, you will reduce it.

My best advice is use one not two speakers for your center channel.

 

[jamie2112]

I would not waste time bi amping it will produce no audible difference except like the good Doctor said your amp will be drawing a 2 ohm load which is not good for the AVR. And 1 speaker should be used with the center channel to avoid lobing and weird comb filtering....just like the Doctor ordered....

 

[OttoMatic]

From a quick Google search, it appears that these speakers are an 8 ohm load. Therefore, if you put a pair of them in parallel, your receiver or amp will see a 4 ohm load. These are nominal impedances, of course, so it's very possible that they will dip below 4 ohms somewhere in the frequency spectrum.

The load seen by the amplifier will not change if it's biwired or single-wired. You will have a 4 ohm load if you connect them in parallel.

Depending on volume levels and your amplifier (or receiver, as the case may be), it's possible you'll be safe doing this. If your amplifier isn't rated to run 4 ohm loads, it's probably not advisable, though I'm sure you can get away with it, especially at low volumes -- just keep an eye on heat and sound.

I agree with the others that bi-wiring won't make any difference in sound, but you can do it if you want. I also agree that you should only use a single speaker for a center channel application.

Good luck either way!

 

[TLS Guy]

From a quick Google search, it appears that these speakers are an 8 ohm load. Therefore, if you put a pair of them in parallel, your receiver or amp will see a 4 ohm load. These are nominal impedances, of course, so it's very possible that they will dip below 4 ohms somewhere in the frequency spectrum.

The load seen by the amplifier will not change if it's biwired or single-wired. You will have a 4 ohm load if you connect them in parallel.

Depending on volume levels and your amplifier (or receiver, as the case may be), it's possible you'll be safe doing this. If your amplifier isn't rated to run 4 ohm loads, it's probably not advisable, though I'm sure you can get away with it, especially at low volumes -- just keep an eye on heat and sound.

I agree with the others that bi-wiring won't make any difference in sound, but you can do it if you want. I also agree that you should only use a single speaker for a center channel application.

Good luck either way!

I would not rely on that Google search. His speakers are two and a half way. You have to regard those as four ohm, no matter what the manufacturer wants to state the "nominal impedance" is.

 

[OttoMatic]

I would not rely on that Google search. His speakers are two and a half way. You have to regard those as four ohm, no matter what the manufacturer wants to state the "nominal impedance" is.

Why is that? Depending on individual driver impedances and crossover design, I believe most any speaker could present an 8 ohm load (nominal).

 

[TLS Guy]

Why is that? Depending on individual driver impedances and crossover design, I believe most any speaker could present an 8 ohm load (nominal).

Not so! In a two and a half way the lower driver is cut in, almost always first order between 400 and 600 Hz. Now if you used 16 ohm woofers, the speaker would have poor sensitivity across a good chunk of the mid band. So you really have no option but to use 8 ohm drivers. So as the lower woofer is shelved in you can't avoid the impedance dropping to four ohms or lower.

When you do the calculations, you find that in the range where the two drivers are reinforcing each other, it generally consumes two thirds of the amplifier power. So that region becomes dominant in actually determining what the impedance of the speaker actually is from a practical stand point. Above the shelving, the impedance will usually be 8 ohms or above, which is how a "nominal" 8 ohm impedance is claimed. In my view that is highly misleading, if not dishonest.

 

[OttoMatic]

Not so!

Well, it's still possible, but with drawbacks in sensitivity (which I was going to note). I agree with what you are saying, though.

Above the shelving, the impedance will usually be 8 ohms or above, which is how a "nominal" 8 ohm impedance is claimed. In my view that is highly misleading, if not dishonest.

Yes, I think you are right in that it's dishonest. Speaker manufacturers should provide impedance plots instead of some meaningless "nominal" number.

 

[TLS Guy]

Well, it's still possible, but with drawbacks in sensitivity (which I was going to note). I agree with what you are saying, though.



Yes, I think you are right in that it's dishonest. Speaker manufacturers should provide impedance plots instead of some meaningless "nominal" number.

Yes, and manufacturers should also provide information on the phase angles, and show the relationship between power consumption and frequency for typical program. They could consider using the proposed speaker amplifier torture index, which would save a lot of explaining on forums like these.

While we are in the mood to explode myths, we should point out that setting speaker settings to small with crossover set to 80 Hz or less unburdens the receiver very little.

Reason one, is that there is little energy below 60 Hz, except for sound effects and the odd organ disc with big romantic works with a lot of full bore organ work on a large instrument.

Reason two, the tuning impedance humps occur in the region of crossover and below. Sealed speakers and TLs having one peak of impedance and ported two. So actually in this region relatively little is demanded from the amp. The real power is in the frequency range of 80 to 400 Hz, especially when speakers are properly diffraction compensated.

It is often stated that there is no correlation between the quality of a speaker and it being a difficult load. This is not actually true. It is not by chance, or the cussedness of the designers, that expensive speakers like the B & W 800 series place huge demands on the amplification provided.

 

[lsiberian]

some very good and helpful discussion. Well stated TLS

 

[kevint]

Thanks for all of your help guys.
I have a cabinet built with the 2 tweeters and 4 x 5" drivers installed. Unfortunately it turned out too nice to scrap and I haven't got the resources to buy a new centre at this time. Could I use one pair of the existing crossovers and come up with a solution?
I do understand that they are two and a half way. Could I make them two way?

 

[TLS Guy]

Thanks for all of your help guys.
I have a cabinet built with the 2 tweeters and 4 x 5" drivers installed. Unfortunately it turned out too nice to scrap and I haven't got the resources to buy a new centre at this time. Could I use one pair of the existing crossovers and come up with a solution?
I do understand that they are two and a half way. Could I make them two way?

No you can't use one pair of existing crossovers. Making them two way will make matters worse.

I can't find any details of those speakers. Sound Dynamics seem to be out of business.

Honestly, my best advice is to use one speaker only. That will give you the best results

 

[kevint]

I took your advice and found a reasonably priced used Paridigm centre.
I plan on doing up a set of cabinets for the garage with the Sound Dynamics.
Sound Dynamics were or are a division of Energy. I found them in a pawn shop and they looked like a well built speaker. Made in Canada. I did a little research and found that they retailed for around $750.00 in 2003.I got the pair for $35.00.
Thanks again.

 

[OttoMatic]

Good call on the Paradigm for the center. That will definitely work better than the other setup.

Have fun.

 

[TLS Guy]

Good call on the Paradigm for the center. That will definitely work better than the other setup.

Have fun.

I agree. The other plan sounded like an excercise in frustration. I think he made a wise decision.