Polk SDA-2A vs Infinity RS IIIb

Bleiz · October 2023

Hello this is my 1:st post on this very nice forum, I'm based in Sweden and started this journey last Saturday having read up on the SDA-2A and similar models finding many interesting posts and threads on this model/tecnology.

My background in this field is an everlasting interest of good sound although I've never had the "real" high-end superstuff regarding amps + speakers, I attended a 1 year soundengineer course w. diploma back in 1987and got lucky to find work immediately afterwards at Polar Studios (Abba) in Stockholm + Sonet studios + Soundtrade studios before becoming a freelance soundengineer and later on building my own studios out in the countryside here in Sweden, now nr. 3 www.lakesong.se this site will however expire by the end of October so see the new site www.magictimbres.se if this is of any interest ;-)

Ok so let's get down to the boiling point here, last weekend I found an almost local ad for the SDA-2A for like 200 usd equivalent in Swedish currency in perfect working order, another guy beat me to it typically, these are very rare in this part of the world.

Googled on was searching for Q Acoustics 3050i and Fyne etc until I saw an ad for the Infinity RSIIIb 500 usd mint yesterday + refurbished which I will get on Saturday coming up, I understand these will suit my living room purposes for both enjoying normal stereo listening + at times for analytic trials of mixes done in the studio downstairs, this livingroom is ca 40 sqm and square leaning to rectangular in shape, wooden surfaces with some carpets.

In the studio I mix various material on the old JBL L19's which has never lied to my ears and during test-listening up until now in the living room I've had the B&W DM 602 S2 bookshelves on stands + an Audio pro sub for bottom slight "puff" for about 10 years.

The things that intrigued me with the SDA series speakers according to many posts and threads here seemed very interesting to say the least in terms of the sound described almost psycho-acoustical magic etc BUT I suppose the Infinity's will adhere more to my needs regarding "normal" but wide soundstage and fast bassresponse for the reasons mentioned above and so I will go for those for now for a starter :-)

Amp is HK670 integrated hope it will do for these speakers @ 4 ohm's otherwise please let me know of better alternatives.

Ok sorry for this lenghty post but I wanted to adress a bit where I'm coming from, all the best to you and greetings from Sweden***

SeleniumFalcon · October 2023

Hallå,
Välkommen till Polks forum!
Hello,
Welcome to Polk's forum!

dromunds · October 2023

The RSIIIb’s are good speakers. I’ve had both the SDA 2A’s and the RSIIIb’s have way better bass. The tweeters are also superior. I had other higher end vintage Infinity as well, such as Kappa 8 which surpassed the RSIIIb’s, but the latter are no slouches by any means. They like good power but those vintage HK’s are good just don’t go cowboy on the volume knob. I do t know what you mean by “refurbished” but the 2A’s have two crossovers which means a lot of money if capacitors and resistors need replacing but the RSIIIb’s also are very expensive to rebuild crossovers. Personally, I think the Infinities kick the snot out of 2A’s. EMIT tweeters are special and they put out the bass. The better the power the better they will sound.

invalid · October 2023

I'm sure the 2A's go a lot lower in bass though, every amp upgrade I've done makes them sound better and better.

F1nut · October 2023

Welcome to Club Polk

Bleiz · October 2023

dromunds wrote: »

The RSIIIb’s are good speakers. I’ve had both the SDA 2A’s and the RSIIIb’s have way better bass. The tweeters are also superior. I had other higher end vintage Infinity as well, such as Kappa 8 which surpassed the RSIIIb’s, but the latter are no slouches by any means. They like good power but those vintage HK’s are good just don’t go cowboy on the volume knob. I do t know what you mean by “refurbished” but the 2A’s have two crossovers which means a lot of money if capacitors and resistors need replacing but the RSIIIb’s also are very expensive to rebuild crossovers. Personally, I think the Infinities kick the snot out of 2A’s. EMIT tweeters are special and they put out the bass. The better the power the better they will sound.

Hi by refurbished I meant the bass elements have had their foams replaced recently, will do new foam-mats (?) around the tweeters/mids as they look bad/deterioated, as for the crossovers I don't know yet, have read some suggestions on another forum for caps + resistors replacement bypassing the pots but need to be sure which values for the flattest response.

You mentioned Kappa 8's as superior so I had to do a little search of course but guess those RSIIIb's will do for my needs and I don't want too much treble going on even though they might be "better" on resolution hi-freq.

Bleiz · October 2023

And yes I forgot to mention as some guys state bi-amping will be even better,
have never dealt with those things so far is the difference that big really?

halo71 · October 2023

I have 2A's and RSIIIa's. Which are pretty much the same as the IIIb. The IIIa' absolutely trounce the 2A's in every way. Better, deeper bass response, midrange. And EMIT tweeters are just fantastic smooth sounding to my ears.

Bleiz · October 2023

halo71 wrote: »

I have 2A's and RSIIIa's. Which are pretty much the same as the IIIb. The IIIa' absolutely trounce the 2A's in every way. Better, deeper bass response, midrange. And EMIT tweeters are just fantastic smooth sounding to my ears.

Aren't the RSIIIa's lesser priced normally, that of course is not necessarily meaning those are lesser in reproducing a "better sound in every way" than the RSIIIb's that also have the EMIT tweeters, what can I say as I've never heard any of them and I'll go for the b's this weekend and am sure they will upgrade the livingroomsound somewhat over my B&W DM602S2's.

Bleiz · October 2023

By the way I forgot to ask you people with experience of the RSIIIb's how about placement, a straight forward or somewhat toe-in like I normally prefer, I will have them in equitriangular distance in between and to my sweetspot of course.

Bleiz · October 2023

The RSIIIB's are in place today and I am very happy, best sweetspot not sitting in the sofa but standing up huuh as they are somewhat tilted upwards w. the stands underneath anyway any ideas regarding straight-forward placement or a little bit of toe-in? :-)

treitz3 · October 2023

Bleiz wrote: »

The RSIIIB's are in place today and I am very happy, best sweetspot not sitting in the sofa but standing up huuh as they are somewhat tilted upwards w. the stands underneath anyway any ideas regarding straight-forward placement or a little bit of toe-in? :-)

This is typical with these types of speakers IME.

Please allow me to offer you a very warm welcome to Club Polk!

Tom

Bleiz · October 2023

Today everything is in place and I thank you for the welcoming messages in this very friendly forum even though we sometimes "speak" about other brands than Polk and that is so exactly what I like about this place!

Have listened yesterday and today on my reference CD's (Steely Dan remastered among several)+ a bit of various music like Randy Crawford's "You might need somebody" and tried different toe-in placements to find a slight degree is just fine for this room + my ears, will skip the Audio Pro sub for now as I am very pleased with the sound coming out of these RSIIIb's :-)

nooshinjohn · October 2023

The Infinity's are excellent speakers, and will only sound better with better amplification and source equipment. Welcome to the rabbit hole, and to the club.

Nightfall · October 2023

Those are great looking speakers I'm sure they sound alright too 😉

I have the little bitty bookies, fan of even the small ones.

Bleiz · October 2023

Nightfall wrote: »

Those are great looking speakers I'm sure they sound alright too 😉

I have the little bitty bookies, fan of even the small ones.

Which boxes are these? ;-)

halo71 · October 2023

Bleiz wrote: »

Which boxes are these? ;-)

Kappa 5's I do believe.

gyosa · October 2023

Love those tweeters !
Used to have a pair of infinity RSa’s in college..

My Salk’s Raal ribbons remind me of those ….

Bk

Best tweeter ever !

Bleiz · October 2023

Hello again can't come to grips with the physical downside that occurs while listening the these RSIIIb's from a normal sitting position 3 meters away in this 40sqm room like I described earlier I have to stand up @ my sweetspot to get the full crispness of the EMIT's as they seem to be higher than my ears while sitting in the sofa, am not a midget 180 cm's tall.

Is there a way to get them to project a bit lower? If turning/mounting them sideways 45 degrees for instance do they project differently in horizontal rather than vertical ribbon orientation? Reflectors above the EMIT's would help or what, strange design to miss out on the treble in such a significant way which I've never experienced before. Should one place them straight instead of a slight toe-in like I have now?

Bleiz · October 2023

Could the above have anything to do with the deterioated refraction foam that will be changed soon, any effects from this and the EMIT's maybe getting more absorbed than intended, what is exactly the purpose of this foam?

pitdogg2 · October 2023

If the foam is deterioated then it cannot absorb more. If anything it will be brighter and more pronounced. The purpose is to absorb some of the waves that would be bouncing off the front of the cabinet and smearing the sound when the waves collide.

treitz3 · October 2023

You might try setting some shims in the back of each speaker to taste. You adjust toe in to achieve a perfect balance between brightness/overall tone and the phantom center image.

Tom

Bleiz · October 2023

pitdogg2 wrote: »

If the foam is deterioated then it cannot absorb more. If anything it will be brighter and more pronounced. The purpose is to absorb some of the waves that would be bouncing off the front of the cabinet and smearing the sound when the waves collide.

Have read that it must be open porous foam not blank and closed skin, or I'll just remove it...in my case like described lately I don't get clean treble unless I stand up, hence it is nowhere shrill or dispersed.

Gardenstater · October 2023

You might be getting some comb filtering in the vertical direction, which is causing some null regions and accentuated regions. That could be due to not having the fully intact anti-diffraction foam on the front baffle. That top edge is a fair distance from the tweeter and is a sharp 90deg corner and you might be getting out of phase reflections from that edge. When that combines with the direct wave from the tweeter it could be causing interference.

Bleiz · October 2023

Gardenstater wrote: »

You might be getting some comb filtering in the vertical direction, which is causing some null regions and accentuated regions. That could be due to not having the fully intact anti-diffraction foam on the front baffle. That top edge is a fair distance from the tweeter and is a sharp 90deg corner and you might be getting out of phase reflections from that edge. When that combines with the direct wave from the tweeter it could be causing interference.

Hi, regarding this antidiffraction foam, wouldn't it be better with some thin felt-like material w. selfadhesive for the said purpose? There are for example the thin grassrolls or sheets that you use for modelrailroad landscapes if you know what I mean, green instead of black foam but more of the properties intended is a wild guess.

Gardenstater · October 2023

Bleiz wrote: »

Gardenstater wrote: »

You might be getting some comb filtering in the vertical direction, which is causing some null regions and accentuated regions. That could be due to not having the fully intact anti-diffraction foam on the front baffle. That top edge is a fair distance from the tweeter and is a sharp 90deg corner and you might be getting out of phase reflections from that edge. When that combines with the direct wave from the tweeter it could be causing interference.

Hi, regarding this antidiffraction foam, wouldn't it be better with some thin felt-like material w. selfadhesive for the said purpose? There are for example the thin grassrolls or sheets that you use for modelrailroad landscapes if you know what I mean, green instead of black foam but more of the properties intended is a wild guess.

Grade F3 Wool Felt would be what I would use. It is a good density and should be more sound absorbent than lower density like F26. Higher wool content as well. Check out the informational chart at the top of this page: This supplier has it in 12" x 12" with adhesive backing. Color is gray. There is a member here VR3 that might be willing to laser cut it for you if you send him a PM.

https://www.mcmaster.com/products/wool-felt/

Bleiz · October 2023

[quote

Grade F3 Wool Felt would be what I would use. It is a good density and should be more sound absorbent than lower density like F26. Higher wool content as well. Check out the informational chart at the top of this page: This supplier has it in 12" x 12" with adhesive backing. Color is gray. There is a member here VR3 that might be willing to laser cut it for you if you send him a PM.

https://www.mcmaster.com/products/wool-felt/

[/quote]

Thank you this confirms the idea perhaps, as I'm based in Sweden I will look and share some material ideas next week, have a bit of surplus material in black from wall absorbing mtrl used in my controlroom.

audioluvr · October 2023

treitz3 wrote: »

You might try setting some shims in the back of each speaker to taste. You adjust toe in to achieve a perfect balance between brightness/overall tone and the phantom center image.

Tom

This ^^^. I'd put 1" risers in the back. Simple test to see if it improves your situation. I have to do the opposite for my Klipsch KG4's. I want a pair of speakers to hit dead center ear level from my sitting position with a beer in my hand and a few more in my circulatory system.

Bleiz · October 2023

Did put some equally thick books underneath the back and the towers are now a bit tilted forwards which doesn't look good at all but gives a perfect tweeter response when sitting @ sweetspot, however the bassresponse still sounds better while standing as it diminishes while sitting down again, it is really obvious and I don't really get the picture w. these speakers to be honest (RSIIIb) have tried different positions and am about 2 feet from the back wall + side wall just slightly toed-in, maybe I should try to get closer to the back wall 1 foot? Also find so far that getting the soundstage right is way eaiser with the previous B&W Dm602S2 on stands and there was never any of the above problems....my room is big enough 40 sqm but the bass law seem to be made for standing in the physics of these speakers really!

invalid · October 2023

Did you try them closer together?

Bleiz · October 2023

invalid wrote: »

Did you try them closer together?

Just slightly otherwise I'll need to sit so close and the furniture w. stereo + tv in between does not allow for less than 280 cm's / 9.2 feet (cone to cone) should I rearrange and go closer? Does probably not get rid of the fact that the bass sounds full only when I stand up and anywhere in the room in fact.

Polk SDA-2A vs Infinity RS IIIb

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