Speaker Impedance help

alfana

Hi all, i have a blown 4ohms tweeter (S20SND2 90420) from RT15, and I found a replacement polk tweeter (SL5000 with 45 watts RMS - 90db 2200 kHz. to 23 kHz.) but it is 8ohms. It is a tad bigger (1") than the old tweeter (3/4") but I managed to intall it to the speaker cabinet anyway.

I hook it up but the tweeter sounds lounder than the woofer and the hiss is not as bright as the old tweeter. I'm not happy with the sound.

1. Does it sound lounder because the impedance is 8 ohms not 4 ohms as the old one?
2. Can I place an 8ohm (8.2ohms) resistor in parallel to bring the 'total' impedance to 4ohms and will this make it sound brighter?

Any help will be appreciated. TIA.

zingo

You will need to buy a replacement RT15 tweeter if they still sell them. An SL5000 is completely different electrically and will not match the other drivers in the speakers, or the crossover circuit.

tonyb

Alot of trouble for a cheap speaker dont you think ? Lots of speakers out there on craigslist than can probably be had for the price of a tweeter or even free in some cases. Even new, monitor 30's or 40's are pretty cheap these days, I wouldn't waste my time on rt15's that need work.

[Deleted User]

Hello alfana,
Welcome to Polk's forum. I agree with the recommendation that you try and get the correct replacement tweeter. Give Polk a call at 1-800-377-7655 or send them an email to: polkcs@polkaudio.com. But, to answer your question you probably need to "pad" down the tweeter's response to reduce the tweeter's level to better match the mid range driver. Try putting a small value resistor in series with the positive wire going to the tweeter not in parallel. There should already be a resistor on the crossover circuit board that you could experiment with increasing the value.
I hope this is helpful information.
Regards, Ken

alfana

thanks for the reply guys.

i know i should not sink money on these speakers but they do match the set i have and like the cherry color. they do sound very nice also. I have th RT15 (1999 assembly), and I know there is modern R15, are they comparable? I already contacted Polk and was quoted $40 per tweeter + shipping, i rather spend $2 on resistors.

so to 'pad' the speaker does it mean put the resistor before the speaker (splice middle of white wire) or after the speaker in series (splice in middle of black wire)?

When i put it in series, wouldn't this increase the impedance to speaker (8 ohms) + resistor (x ohms)? I thought i have to match the 4ohms which it replaced.

I will try this tonight and hear what it sounds like.

Any other ideas?

F1nut

Any other ideas?

Find another pair on eBay, CL, etc.

goofyGAguy

alfana wrote: »

I have th RT15 (1999 assembly), and I know there is modern R15, are they comparable?

Not even close!

dudeinaroom

Putting an 8 ohm resistor in parallel will bring it back down to 4 ohms and give you the proper crossover point, but may make the tweeter even louder. Putting xohm resistor in series is roing to raise the impedance, and also make the crossover point even more out of alignment with the mid/bass driver.

alfana

goofyGAguy wrote: »

Not even close!

So how do they compare? both are bookshelves.

Find another pair on eBay, CL, etc.

hard to find same cherry color, but i can transfer the speakers so I will look around.

putting an 8 ohm resistor in parallel will bring it back down to 4 ohms and give you the proper crossover point, but may make the tweeter even louder.

i will see what the effects are for series and for parallel connection. this will just be for curiousity/learning now...


i will just hunt for a replacement RT15 somewhere. how much do you think they will go for?

goofyGAguy

alfana wrote: »

So how do they compare? both are bookshelves.

A Dodge and a BMW are both cars. RT series speakers are crisp and clear. R series sound like someone threw a down comforter over them.

alfana

goofyGAguy wrote: »

RT series speakers are crisp and clear. R series sound like someone threw a down comforter over them.

i've never heard of R15's....that's part of the reason i want to save these RT15's...

Tbone289

Putting a mismatched tweeter in one is not "saving" them, IMO. The tonal balance and image will always be off, regardless of if you match the impedance or not.

[Deleted User]

Hello,
The goal is to turn down the tweeter's output since it is now louder than the mid range driver. That's what resistors do, they reduce the energy flowing through them. You might want to start with a 0.5 Ohm resistor in series with the tweeter's positive wire (find the wire that leaves the crossover and goes to the tweeter, connect the resistor so the signal goes through the resistor and then to the tweeter's terminal). If the reduction isn't enough then use a 1.0 Ohm and see what that does.
Regards, Ken

alfana

Thank you all for the reply. I found the fix, this should work for other people as well. The sound is back to where I am really happy with.

The solution: I placed 1ohm in series, then I placed a 4.7ohms parallel with the 8ohm tweeter. Not only did this fix the loud tweeter in relation to the woofer, but it also made the tweeter bright as it should be. Overall impedance is 4ohms (just like the original blown tweeter). This cost me $5.