Resistor run in parallel w/speaker wire

NJPOLKER

I gotta say I was real skeptial at first but not now. While at the Carver Forum I read where Bob Carver was at the Carver Fest. Bob said something like, by adding a 1.5ohm resistor in line with your speaker wire you can get your ss sound kinda tube like, or something to that effect. Well I had a couple of Eagle 2.5ohm 12 watt resistors I got from Madisound sitting around doing nothing so decided to experiment alittle. I took my 12 guage wire and soldered the resistor about a foot from the end closest to the speakers. I soldered it in the "red" side of the speaker wire only and taped it off with electrical tape. Hook everything back up and gave it a listen. At that time I was running the Adcom 5400 amp and the GTP450 pre-amp along with my Arcam CDP, average equipment I guess, except for my SRSII's which are outstanding!
Well, I gotta say everything seems to sound alittle better, more clear and detailed, soft/warm no matter what I listen to. I am still skeptial because thats the kind of guy I am. That being said I plan on trying a few more resistors with different values to hear for myself how they all sound or the difference they make. Oh yeah, the resistors do get real warm or hot depending on the volume I am using. I will try out 25 watters which should'nt heat up as much.
Maybe what I am doing is just making subtle changes to the sound and like what I am hearing just because I like to hear changes. Since the resistors are so affordable it is a cheap way for me to get my jollies.
Has anyone tried this?
Am I suffering an illness with tweaking my SDA/SRS?
I don't think I can leave well enough alone,yet!!
Maybe I have sniffed too much Dynamat

george daniel

Yep,, thats what he said,,I was there,,I don't remember the specific value,,IIRC it was 1 ohm,, Jesse was there, maybe he'll chime in when he arises;). Nope,, have not tried it,, would you describe the sound you are getting as tubey,warm?

NJPOLKER

Hey George,
I am not sure if I'd call it warm as in the warm sound from a tube because I have never heard a tube amp/pre-amp. When I listen to Mick Fleetwood hit the symbals and listen the The Voice by Celtic Woman, I think thats the name, I gotta say its more detailed with no shrill. I am not saying the SRSII's or the SDA2a's had a problem, both with RDO's and or the Peerless in the SDA2a's. Just saying they seem alittle nicer.

george daniel

Thats a pretty good description,, I've never gotten around to trying it,, keep us posted,please,,as Mr. Carver said something like the resistor inline would get you 80% of the tube sound,,or something like that. It's good to know that it's pleasing(the sound). What watt resistor did you use,if you don't mind me asking? I dont think that Bob ever specified wattage,,and that was a question that I forgot to ask,,I wonder if it even matters. Interesting little tweak though.

NJPOLKER

A 25 watt resistor is probably the way to go. The 12 watter I use works fine but gets hot.
Now that you mention it I remember now that it has been said he said 80% of the tube sound.
I do wonder what the difference will be when I go from the 2.5 ohm to trying out 1.5 ohm and 3.5 ohm.
Drew

Schurkey

What's the difference between an inserted ohm of resistance in the speaker wire, and Carver's famous ohm of output impedance in his TFM amps?

engtaz

1.5 ohm 50watt.

engtaz

hypertone

Don't you want to wire it up in series and not parallel?

mhardy6647

Yes, you have shot your damping factor to heck (not to mention wasting much of your amplifier's power output) by using Sideshow Bob's little trick :-)

In parallel, you'd suck the current capacity of your amplifier dry.

Ohm's... it's the law :-)

E = IR

NJPOLKER

hypertone wrote: »

Don't you want to wire it up in series and not parallel?

I think your right. I have it in series not parallel my mistake in wording it incorrectly.

NJPOLKER

mhardy6647 wrote: »

Yes, you have shot your damping factor to heck (not to mention wasting much of your amplifier's power output) by using Sideshow Bob's little trick :-)

In parallel, you'd suck the current capacity of your amplifier dry.

Ohm's... it's the law :-)

E = IR

Really? hhhmmmmmmm I better check on that before I screw something up!!
I am not sure what you mean by dampening factor, could you help me out alittle? Also same applies to the current being sucked out?
Thanks alot Drew

mhardy6647

Damping factor is the ratio of the nominal impedance of a speaker (load) to the an amplifier's output impedance. It was a widely quoted specification in the 1950s through at least 1970s, and still pops up (at least the concept does) today. An amplifier with a numerically large damping factor provides better control of a woofer at low frequencies (back-EMF generated by the woofer's voice coil can interact with the output section of the amplifier). A low DF amp and a high Qts speaker can produce soft, "flabby" bass.

Good old tube amps with little or now negative feedback had (EDIT) fairly high output impedance (often 0.5 or 1 Ohm). This would correspond to a DF or 4 or 8, respectively, with an 8 ohm load (e.g., a nominal 8-ohm loudspeaker or a resistive 8-ohm dummy load).

In today's parlance, this would be very low damping factor. The trick used to decrease output impedance of amplifiers is either to parallel more low-impedance output devices (e.g., transistors in an direct-coupled amp or tubes in an OTL amp) and/or to use gobs of local and/or global negative feedback (which can cause all sorts of distortions in the time domain if done recklessly).

Sideshow Bob Carver says you can mimic that "tube amp sound" by adding resistance in series with the power amp output; essentially decreasing the damping factor and 'warming up' the bass. Is this equivalent to good tube amp sound? I'd say no, but I am biased ;-)

I am in fact doing Carver something of a disservice; he worked hard to mimic the 'transfer function' of a good-sounding tube amp in the SS domain; Stereophile famously endorsed his results in single (double?) blind tests as I recall.

Adding resistance in parallel will decrease the load impedance seen by the amp, possibly to dangerously low levels for the stability of the amp in question.

Resistance in parallel follows Ohm's law thus:
1/Rt = 1/(1/R1 + 1/R2 + ... 1/Rn) for "n" resistances in parallel. This would also hold for impedance (impedance is the AC analog of DC resistance)

If, for example, you parallel a 1.5 ohm power resistor across an 8 ohm speaker load, the resultant impedance felt by your amp will be: 1/Rt = 1/(1/1.5 + 1/8) or Rt = 1.26 Ohm.

This low resulting load impedance is fairly close to a short circuit across the amp output. Many amps will run out of steam (so to speak) trying to produce the high current levels such a low impedance would demand from an amp at any given volume level (compared to a higher impedance load).

mhardy6647

The Carver/Stereophile amp test:
http://www.nationmaster.com/encyclopedia/Bob-Carver
http://en.wikipedia.org/wiki/Bob_Carver
http://www.carveraudio.com/CarverChallenge.pdf

(EDIT: it was a single-blind test)

NJPOLKER

mhardy,
Thanks for your response and I will read it in the am when I can comprehend it better.
Thanks again and always
Drew

ps: are you a Red Sox fan, they will in the world series next year I guarantee it!!!!!

TNRabbit

I don't see how INCREASING the resistance can shoot your damping factor; DECREASING resistance will for sure blow the damping & make the bass more "muddy" IMHO. The amp will see a mild increase in resistance (1.5 ohms to be exact) from the basic speaker resistance. Yes, this will place a larger demand on your amp for the same output. However, that will only matter if you run your amp above 80% most of the time. FYI: Bob also said to bump up the bass about 1 dB in conjunction with this mod to give you "90%" of the tube sound.

mhardy6647

DF = load impedance divided by amplifier output impedance. Inserting DC resistance in series with the load increases the latter (i.e., the denominator) and the DF is reduced as a consequence. There's nothing magical about the Damping Factor calculation, and there's considerable controversy as to how much DF is enough.

Marty913

NJPOLKER wrote: »

mhardy,
Thanks for your response and I will read it in the am when I can comprehend it better.
Thanks again and always
Drew

ps: are you a Red Sox fan, they will in the world series next year I guarantee it!!!!!

Are you going to do some more test (listening or otherwise). I'm curious as to your sound observations after listening for awhile, heat effect if you move to a 25/50 watt resistor. and of course amp effect due to the damping factor change. Interesting discussion and a lots less violent than some other resistor mod discussions.

NJPOLKER

Well, today I cut off the end of the speaker wire thus eliminating the 2.5ohm 10 watt resistor and reattached the speaker wire to the binding posts on my SRSII's. After listening to the same songs I've been concentrating on for awhile I have to say mhardy is on target.
To my ears it seems when the resistor was in place it filtered out some of the highs and probably everything else but not as noticable to me. When I say filtered out its not in a bad way just kinda tapered off some of the highest of the highs. Also I noticed the resistor ate up some power from my Carver M-1.5t which has a ton of power.
At this point I will try a 1.5ohm at 25 or 50 watt when I get around to it. As long as I didn't damage anything I am happy I tried this out if for no other reason I learned alittle more about Hi-Fi
One more thing
My stereo system has never sounded better.It seems to be sounding better and better all the time.
Drew

ShinAce

If I need to test the specs on a speaker, I sometimes add a 1k ohm resistor in series. with the speaker. As long as the amp is solid state, this works fine and causes no problems.

Adding resistace will in fact yield a lower damping factor for the woofer and a higher Qts(SQ afficianados take note).