Powering Polk RTia9's

[Fuelsrock]

I know there is a lot of info on this topic out there, but alot of it is dated. I just purchased these because they were beasts at a great price. I also purchased the CSi6 for the center. I have a Denon AVR AVR-x2500h that I intended on using, but understand that it might be underpowered for the towers. I would just buy a external amp, but the Denon doesn't have any pre-outs for the external amp. The guys at Magnolia are telling me to buy a Arcam avr390. They are saying that it would be enough to power my 5.1 system and be done. They were also the ones that sold me the Denon last year! This set up is just being used for Movies in a game room that is 18x18. No gaming and a little music. My sub is a PSW505 and the rears are PolkRM7 satellites. Thanks for the input!!

 

[Pogre]

Phew. Okay. How much is the Arcam he's suggesting, just out of curiosity?

Depending on your budget I like the Denon X3500 or maybe even the X4500. The 4500 has a touch more power and maybe a couple of extra features/channels. They're not current models but both are still current enough for today, imo. Those aren't bad prices for what you get. Both have the same Audyssey XT32-SubEQ for room correction and a full set of preouts should you want to get an amp down the road.

 

[Fuelsrock]

They want $1500 for the Arcam.

 

[Pogre]

*

They want $1500 for the Arcam.

*Gulp*

Well... it's a nice unit but that's a lot to spend on a receiver at 80 wpc. I think the Denon X4500 I linked above will do an excellent job with just as good sound quality for almost half the price! And hell, if you still need more power then you can pick up a couple of Outlaw monoblocks (I see those on sale at 3 for $799 or $899 all the time) or a 2 or 3 channel amp for your front stage. That's a good receiver with additional amplification for ~the same money as the Arcam by itself!

 

[ryanosaur]

Iirc, those rtia9s also have some bad phase angle/impedance shenanigans going on.
A good amp is recommended I think, but a good AVR with preouts is a necessity. Not using a robust amp and crushing the volume on those speakers can be a problem for an AVR, potentially.

 

[William Lemmerhirt]

I would buy a new sub first. Bet nobody saw that coming from me!!!

 

[William Lemmerhirt]

Could definitely buy a 3500, a used pro amp and an HSU mk5 for 1500! Would be badazz fo sho.

 

[lovinthehd]

I'd simply use the system as-is for a while and see if there are any actual amp shortcomings first in your use. Are there any particular issues at this time rather than listening to idiotic salespeople at BB or the typical Polk forum fan boi who swears massive amounts of power are necessary to operate these speakers? Sure, they may have some low impedance/phase angle issues to consider but we don't know your own listening levels or distance from the speakers, etc. Might try using an spl calculator like this to estimate an idea of your needs http://myhometheater.homestead.com/splcalculator.html. The Arcam wouldn't be my way of thinking, it's not a particularly powerful unit for the price, but pre-outs for amp flexibility is generally a good thing. I'd update the sub before the avr.

 

[Fuelsrock]

The speakers get here this week and can't wait. I haven't pulled the trigger on the Arcam yet and do intend to try the set up with the Denon 2500 first. I just don't want to burn up the amp or toast the tweeters in the towers. I will crank her up to 75 and if I don't like the level, I may have to pony up on the Arcam and hopefully that will give me the boost I want till I can afford a external amp. I am not hosting house parties, but don't want it to sound wimpy either. Thanks for all the input!!

 

[Pogre]

The speakers get here this week and can't wait. I haven't pulled the trigger on the Arcam yet and do intend to try the set up with the Denon 2500 first. I just don't want to burn up the amp or toast the tweeters in the towers. I will crank her up to 75 and if I don't like the level, I may have to pony up on the Arcam and hopefully that will give me the boost I want till I can afford a external amp. I am not hosting house parties, but don't want it to sound wimpy either. Thanks for all the input!!

Did you read any of our replies..? Nobody who posted here thinks the Arcam is a good option! It's too much for what you get. The 2 I linked above are much better value and have a little bit more power, and if you still think you might need more both Denons have a full set of preouts.

HD makes an excellent point too tho... you'll get more "wow" factor upgrading that subwoofer. It's not about having enough bass, it's about having good clean bass and that 505 is kinda meh. A good clean sub has a way of elevating your entire system. It was my number 2 biggest "wow" moment during my entire upgrade process. Everyone underestimates good subwoofage, me included (not anymore!).

 

[lovinthehd]

The speakers get here this week and can't wait. I haven't pulled the trigger on the Arcam yet and do intend to try the set up with the Denon 2500 first. I just don't want to burn up the amp or toast the tweeters in the towers. I will crank her up to 75 and if I don't like the level, I may have to pony up on the Arcam and hopefully that will give me the boost I want till I can afford a external amp. I am not hosting house parties, but don't want it to sound wimpy either. Thanks for all the input!!

Don't buy the Arcam, it's a waste at that price (IMHO of course), besides, the Arcam 390 is not a boost up in power. Keep in mind it takes a doubling of power to gain a mere 3dB advantage in spl. I wouldn't worry about burning up the amp or toasting the tweeters unless you're inherently stupid with gear. If it starts to sound bad, dial it down. Drunken parties can be hard on gear. The Arcam 390 is not a boost up in power.

 

[Gmoney]

The speakers get here this week and can't wait. I haven't pulled the trigger on the Arcam yet and do intend to try the set up with the Denon 2500 first. I just don't want to burn up the amp or toast the tweeters in the towers. I will crank her up to 75 and if I don't like the level, I may have to pony up on the Arcam and hopefully that will give me the boost I want till I can afford a external amp. I am not hosting house parties, but don't want it to sound wimpy either. Thanks for all the input!!

On Amazon, Onkyo’s THX-RZ820 new with a 3 year warranty going for 399.00! That AVR kicks out 130 X 2 @ 8 Ohms. Use the rest of your funds for a Sub upgrade. Or check out Accessories4less Denons 3500 going for 449.00 with a years warranty.

 

[jgstudios]

Iirc, those rtia9s also have some bad phase angle/impedance shenanigans going on.
A good amp is recommended I think, but a good AVR with preouts is a necessity. Not using a robust amp and crushing the volume on those speakers can be a problem for an AVR, potentially.

Interesting! Can you explain a bit more about the phase angle/impedance issues in the RTi-A9 speakers, What is it, and how a good amp overcomes this? I have a pair of A9s and have been contemplating adding a power amp to the setup for these since I got them, but they seem fine as they are with my older integra and pioneer elite AVR receivers. Due to my aging ears and my own particular sensitivity, I generally don't push my systems past 75 db where I sit, and that's only on rare occasions. As a bass head, the only thing I've found is the A9s really need a subwoofer to make the whole package come alive, but that's just how I like my music.

 

[PENG]

Fuelsrock said:
I will crank her up to 75 and if I don't like the level, I may have to pony up on the Arcam and hopefully that will give me the boost I want till I can afford a external amp.

I would suggest you take a good look of their specs and you will see that the Arcam won't make any difference unless you use your imagination.

From the Arcam UK website:
Continuous power output, per channel, 8Ω (AVR390)
2 channels driven, 20Hz - 20kHz, <0.02% THD - 80W
2 channels driven, 1kHz, 0.2% THD - 86W
7 channels driven, 1kHz, 0.2% THD - 60W
Residual noise & hum (A-wtd) - <0.15mV

Denon AVR-X2500H from Denon USA website product sheet info:
2 channels driven, 20Hz - 20kHz, 0.08% THD - 95W

In past S&V bench tested many Denon AVRs and their measured output with two channels driven into 8 and 4 ohms at 0.1% THD, typically exceeded their specs; and in the 5/7 channels driven into 8 ohms tests, they would be around 60 to 70% of their measured two channels driven output.

You can actually compared the bench test results of the Arcam AVR390 with your Denon AVR-X2500H from the German Audiovision.de, the measurements are for 6 ohm load for the 5/7 channel driven test and 4 ohm for the 2 channel drive tests, at 1 kHz. Unless I missed, Audiovision.de did not mention at what THD level they took their measurements. My guess is, 0.1 or 1%. Since both units were measured on the same bench using the same standards, it seems to be a fair comparison.

audiovision.de/arcam-fmj-avr390-test/
audiovision.de/denon-avr-x2500h-test/

AVR390...........................................................AVR-X2500H
7 channel: 67 W..............................................68 W
5 channel: 85 W..............................................82 W
2 channel: 106W...........................................146 W

The Bestbuy/Magnolia reps typically are not very technically oriented. It is natural for them to assume more expensive receivers not only have better sound quality, but also more powerful.

The spl calculator HD linked should give you a good idea of how much power you would need for the RTIA9 towers. The sad fact is, if the Denon cannot do the job for you, the ARCAM cannot do it either, that is for sure.

 

[Fuelsrock]

I guess I was "sold" in the Magnolia Sound Room then. He played a Arcam 390 at volume 65 and then cut it over to the Denon 2600 and the sound difference was night and day.

After the feedback I received from this post, I did more research on the Arcam amps and understand that although the power and sound are great, the system itself is glitchy. I don't want to spend that level of money and have the thing cut out intermittently. I found a Denon 4500 refurb for $899. I am still crossing my fingers that my 2500 will be fine for a while, but will pony up the extra G if I have to. I like how the 4500 has a pre-out too if I need it down the road. Thanks for all the input!!

 

[lovinthehd]

I guess I was "sold" in the Magnolia Sound Room then. He played a Arcam 390 at volume 65 and then cut it over to the Denon 2600 and the sound difference was night and day.

After the feedback I received from this post, I did more research on the Arcam amps and understand that although the power and sound are great, the system itself is glitchy. I don't want to spend that level of money and have the thing cut out intermittently. I found a Denon 4500 referb for $899. I am still crossing my fingers that my 2500 will be fine for a while, but will pony up the extra G if I have to. I like how the 4500 has a pre-out too if I need it down the road. Thanks for all the input!!

Hard to know what that comparison meant, or if they were on an equal basis let alone level matched....

 

[Pogre]

I found a Denon 4500 refurb for $899.

I linked you to a brand new one for the same price.

 

[Pogre]

Hard to know what that comparison meant, or if they were on an equal basis let alone level matched....

Exactly! All other things being equal there shouldn't be any difference in sq in a pure/direct mode. If there is a "night and day" difference one of the units was probably tweaked to sound better (slightly higher volume, DSP engaged on one but not the other, etc.). If anything, your 2500 has more power than that overpriced Arcam!

 

[PENG]

Interesting! Can you explain a bit more about the phase angle/impedance issues in the RTi-A9 speakers, What is it, and how a good amp overcomes this?

It is the phase angle between the applied voltage and the current drawn by the speakers. AC voltage and current are referred to as "phasors", (think vector on the mech side that most people understand). Phasors have magnitude and direction like vectors do, but the direction in this case is the "phase".

Phase Relationships in AC Circuits

For a moving coil loudspeaker, both the magnitude (in ohms) and phase angle (in degrees or radians), would vary with frequency. Below are the impedance plots of the RTi A1 vs frequency.

SoundStage! Measurements - Polk Audio RTi A1 Loudspeakers (3/2010)

Phase angle (in degrees):

and the magnitude in ohms:

I have a pair of A9s and have been contemplating adding a power amp to the setup for these since I got them, but they seem fine aIs they are with my older integra and pioneer elite AVR receivers. Due to my aging ears and my own particular sensitivity, I generally don't push my systems past 75 db where I sit, and that's only on rare occasions. As a bass head, the only thing I've found is the A9s really need a subwoofer to make the whole package come alive, but that's just how I like my music.

It depends on how far you sit too, but given that you don't push past 75 dB, based on the published specs of he RTi-A9 that says:

Sensitivity: 90 dB/W/meter
Nominal impedance: 8 ohms

so if you sit from say 15 feet, you need about 0.33 W to get 75 dB with just one speaker. For every 3 dB increase in SPL, you need 2X the power.

S&V's review (https://www.soundandvision.com/content/polk-rti-a9-speaker-system-ht-labs-measures) showed the RTiA9's bass response from 40-300 Hz very flat, so if you are a bass head, the only thing you can do is to use them with subwoofers. REQ such as Audyssey (with the Editor App), YPAO, Dirac Live can also help.

The measurements did show some nasty phase angles at below 70 Hz, so again if you use sub(s) and set the crossover frequency to 80 Hz, you will take care that potential issue too, at least to a large extent if not totally.

Phase angle issues will result in more power/heat the amp's output devices must dissipate for the same current draw by the speakers. External fans may therefore be needed to help remove some heat.

 

[lovinthehd]

One further thing about listening at an average 75dB is power for peaks, conceivably up to 20dB (100x the power) so that comes into consideration as well. When you say 75dB (and I mean OP, not what jgstudios mentioned for his use), is that an average or max level? Is it a number from your volume scale on the avr? If it is the volume scale, you're using the absolute scale where that's not an indication of 75 dB.....