Speaker suggestions for Adcom GFA-5500? 4 ohm or 8?

ipsullivan

First off, I currently have a pair of RTA 11Ts powered by an Adcom GFA-5500, and I am using a Yamaha HTR-5860 as a pre-amp.

Will I see much difference in sound quality with 4 ohm vs 8 speakers? The 11Ts are 6 ohm, does this impose any issues since the amp is only rated at 4 and 8?

The GFA5500 is rated at 350 watts into 4 ohms and 300 into 8 ohm.

I am looking for something that can utilize more of the amp's potential, also in terms of size, I would like to stick with something similar to the 11Ts.

I am also considering a dedicated pre-amp but not sure if it would be worth the money at this point. But, that is discussion for a different forum.

Any suggestions/comments would be great.

Thanks,
Ian

ZLTFUL

Your 11Ts are great speakers.
Have you upgraded the crossovers?
Have you replaced the tweeters with the modern replacements available from Polk? (The Ts came with the SL2000 tweeter so the RDO-194 would be the replacement part)
Did you dynamat the driver baskets?
New gaskets?
How about Larry's Rings or Hurricane Nuts to make the driver mounting more rigid?
All of the above upgrades can have a dramatic effect at improving the sound of your great vintage Polk speakers.

The GFA5500 is also a fantastic amp. And I think you are misinterpreting how your amplifier is delivering its power to your speakers.
First, ignore that they are a 6 ohm speaker. Your amp is stable down to 4 ohms which means it has no problem delivering power to a 6 ohm load. An educated guess using my napkin math would put the power in the range of 260-280 watts being delivered to your speakers...but, and here is the key, that would *only* be at maximum volume.
The fact is, your speakers, even at what you would probably consider very loud volume aren't drawing all of that power. Low notes in the music draw spikes in that power but the midrange and high range of music really doesn't require a whole lot of power.

Perosnally, I would focus on upgrading your speakers. There is plenty of how tos here and none of it is difficult in the least if you can solder. And even if you can't, Trey (VR3) and westmassguy both offer crossover upgrade services from simply selling you the parts to full on plug and play crossovers.
The tweeters are available through Polk Customer Service. The number is under the Support--> Contact Us option above. Mention your membership in Club Polk, and they will give you free shipping (Helen is sort of the go-to girl for these kind of requests).
Dynamat can be had from local vendors as well as small kits on eBay or the like.
Rings can be had from Toolfan here on the forums or hurricane nuts can be purchased through Part-Express.

I would also consider a dedicated pre-amp. AVRs as pre-amps isn't a horrible idea but you have all that extra circuitry that serves no purpose for you.

Bear in mind that my 2 channel system is a pair of RTA-15TLs, the larger sibling of your 11s. And I am currently running them (fully upgraded mind you) on a 30 watt per channel hybrid tube amp. And I can assure you that clean, quality and high volume are no problem at all.

You have great speakers, you have really good power. The speakers can be improved...a LOT.

steveinaz

The impedance rating of speakers has nothing to do with quality, it's simply a by-product of the design used. However, 4ohm speakers do need a more robust amplifier section (higher quality amp), especially if you like higher volume levels.

When a lower impedance speaker (4ohm) is connected to an amp, it acts more like a short than a higher impedance (8ohm) speaker---therefore more current has to be availabe from the amplifier; usually higher current amps are more costly/more robust.

Also keep in mind the speaker impedance specs are typically quoted as "nominal" (meaning: average) thru the frequency spectrum. A 4ohm nominally rated speaker may dip all the way down to 2ohms at some frequencies (typically bass freq's), and as high as 16ohms in others. Another good reason to spend the cash on a good quality amplifier.

ipsullivan

ZLTFUL,

Thanks for the advice, looks like upgrading the 11Ts would be cheaper than searching for something else.

There is a guy locally, (Carl's Custom Loudspeakers) that does crossover upgrades. Replacing the caps and resistors he quoted me at $150, for the pair (six caps and 2 resistors). Is this reasonable? Not sure who's hardware he is using, will try to find out on Monday.

Looking into tweeters and dynamat also.

Thanks,
Ian

hertz9753

Also check with Trey. He does great mods and is a member here. http://www.vr3mods.com/

zane77

Definately give Trey (VR3) a shout, he has a lot of experiance with doing the crossover upgades and is familiar with the speakers you have, you won't be disappointed in his work. Let him know a budget and he will figure something out for you.