Polk Audio RTiA7 Mod Thread

gp4jesus

gp4jesus wrote: »

consider this alternative:

http://www.polkaudio.com/forums/showthread.php?t=115762

...to dynamat

F1nut

PrazVT wrote: »

It looks like Trey will be using Clarity Cap PX with ESA bypass caps and Mills resistors. He's also upgrading the binding posts.

There's no need for bypass caps when replacing the others with poly caps.

If you take your driver and tap or knock on the side of the magnet shield it will ring.

Interesting. When I pinged my A7 driver baskets and shields I heard no ringing.

PrazVT

There's no need for bypass caps when replacing the others with poly caps.

I think you mentioned that earlier in the thread - honestly, I don't know enough to speak intelligently about it.

Trey - any thoughts on this?

VR3

The ESA series is far nicer than the PX line up - we have to use the PX line up because of size...

I understand the argument but there are many folks who disagree and agree with the above statement...

GR Research (Danny Ritchie) uses bypass caps on all of his capacitors in his crossover....

The negative (as far as some say) is it introduces artifacts because they are unequal values.

I have done this with LSi9 crossovers and RTia7 crossovers with no issues what-so-ever...

I think we will be fine. There is not much room to work on these crossovers so you cant use realllllllly good parts and keep them internal, thats why I like to use the bypass caps that are NICE to keep the quality level up.

For instance on a LSi9 crossover I am doing right now we are using the MR line as a bypass

PrazVT

Thanks for the explanation Trey. After doing a little reading, I think I understand this a little bit better. The argument against the bypass cap seems to be (and correct me if I'm interpreting this wrong) that whatever % of the main cap is bypassed is too small to make a difference since the most of the performance is determined by the main cap. It sounds like the argument for could be that if it's too cost /space prohibitive to use the poly you want, a higher quality bypass cap could bridge the gap. Trey seems to have come to a similar conclusion.

That being said, I'll let Trey do his thing. Interesting reading though.

jbooker82

gp4jesus wrote: »

consider this alternative:

http://www.polkaudio.com/forums/showthread.php?t=115762

Are you talking about the Armacell tape? I thought they use it for making gaskets to seal the driver and the cabnet, not for dampining vibrations on the basket.

PrazVT

Might as well get some dynomat coming and cover the baskets and the metal magnet shields of the drivers. That is what I did to kill time while they were down. My wife though I was going crazzy being with out them.

Do you have any pics of how you did it or the 'after' ?

jbooker82

I just bought a Dynomat Extreme Wedge pack. It comes with a small roll of 18"x32" long.

I cut a strip slightly wider than the width of the magnet shield. Wrap it around the magnet shield so it is even with the top of the shield (middle of the driver). Then work around the Then trace the bottom of the magnet shield and cut a circle out. I did mine slightly larger so the circle would slightly overlap the strip I wraped around the magnet shield. You can make the strips slight wider or the circle slightly larger. That way you have the material over lap a little.

Then I had a strip cut that was slightly narrower than the fingers of the basket. Cut up in to short pieces and apply to the fingers. Just don't put it on to high up where it will inter fear with the seal between the driver and the wood cabinet.

If you look at the magnet shields on the drivers You can see where they meet the driver basket there is a seam / gap. I covered those up with small scrap strips that were left over.

Here is a link to the stuff I bought. I just figured for $25-$30 bucks shipped it couldn't hurt.
http://shop.ebay.com/i.html?_nkw=dynamat+extreme+wedge&_sacat=0&_sop=3&_odkw=dynamat&_osacat=0&_trksid=p3286.c0.m270.l1313

jbooker82

I took the mid driver out to get some pics for you.

jbooker82

You cant use the scrap stuff to seal / dynomat the top of the magnet shield because it is goes up and then has a recess where the shield meets the basket.

On the woofers the magnet shield is flush where it meets the basket. I also cut out a hole in the dynamat. I didn't know if the hole was there for ventilation so I didn't want to cover it up.

jbooker82

jbooker82 wrote: »

You cant use the scrap stuff to seal / dynomat the top of the magnet shield because it is goes up and then has a recess where the shield meets the basket.

This is ment for the mid range speaker.

PrazVT

I took the mid driver out to get some pics for you.

Thanks for the pics and instructions jbooker82! The photos help alot! I'll order some dynamat today and will give it a shot this week.

PrazVT

While I'm at it...should I take the drivers out of my LSi9s and do those too?

VR3

I have some LSi9 drivers here and I dont think you will find any improvement

PrazVT

cool - I'll leave 'em alone.

gp4jesus

jbooker82 wrote: »

...Armacell tape... ...making gaskets to seal the driver and the cabnet... ...dampining vibrations on the basket[& cabnet]

I missread that thread. Sidenote to this topic: the CSi A6 top & bottom panels NEED dampening. While doing some wiring upgrades on mine I noticed they rang when tapped.

And,... ...Sorry for "beating a dead horse;" I urge all those that know the business end of a soldering iron replace/upgrade the wire between the XO and BPs on all your Polk speakers. If it were just 18 ga wire... ...instead that wire will break after a few bends demonstrating its grossly inferior quality.

cheers

VR3

This is exciting!

I finally get to build a Fortress Plus!

10" Rods, ESA tweeter network, SA midbass - will be 10" tall!!

AND! It is going to Australia!! My first "international" modification, not my first out of the country though, you Canadians ROCK!

mdale

Hi. About two years ago, I purchased my RTi-A7s without knowing what I really wanted. They looked nice, fairly affordable, and got good reviews. After two years of system improvements and tweaking, I'm fairly satisfied with their performance. My system is used 50/50 3.2HT/2.2music - but I really want the best musical quality possible. At times, the A7s seem kinda harsh, so I'm interested in VR3's crossover modifications. Therefore, I'm wondering whether any measurement data exists that compares the A7's performance with the original manufacturer's crossovers vs VR3's crossovers? If yes, how could I get a copy of that information? Thank you. - mdale

VR3

There is no exact comparison measurements. I can tell you that there technically should not be a measureable frequency graph difference of the parts.

The parts used in the stock crossovers, electrolytic caps, sand cast resistors tend to be a noisier component that can cause oddities in the high frequency response, causing brightness, etc

dromichet

I'm about 10 years late to the game but I thought of adding my experience with the cap upgrades.

I got my A7's from a friend for free and liked the sound although they seemed to be a bit harsh/inconsistent with female/male voices. I'm not an audiofile but I'll try to describe the changes as best I can.

I figured for a medium speaker I should go with medium caps from a reputable company that makes good caps. For the 8.2u, 10u, 15u went with Jantzen MKT and for the 18u went with Jantzen CrossCap. These caps are described to be entry-mid tier specifically made for crossovers. I've also upgraded the internal wiring to 12awg monster speaker cables.

I converted one speaker so I can easily A/B them. The result:

Very obvious. Total different sound. It took the mids from in your face and aligned it more with the rest of the sound. It boosted the bass quite a bit. I found that the original was too mid/high centric with the bass being lost somewhat. With the change, the bass stands out more, maybe it made it more balanced with the rest but at times seems to also overpower the mid and high. It also lost a bit of sparkle since it took the edge off the high and mid. It fixed the strings and trumpets which before could be a bit painful at times. After the change the instruments sound amazing. It also cleared up the voices, pushing them back a bit and giving them a bit deeper bassier sound. Overall, with these caps, it took the high/mid edge and brought in bass.

In my wife's words, she has a much better musical ear, the original has a live performance feel to it with instruments all over the place while the mods sounds like a studio sound where everything blends in better. She prefers the originals for voice and the mod for instruments.

Hope this helps future moders picking their caps for these speakers.

dromichet

I have upgraded the second speaker and left the internal wires stock - the first speaker internal wires were upgraded to 12awg monster speaker wire.

It brought the speakers closer together in sound however they're still different.

The stock wires still pushes the voice forward and overall more lean, maybe more balanced.

The monster wire brings the instruments to the same level as the voice and the overall sound is bassier, definitely preferring instruments especially strings. The reverb on the strings is a lot more pronounced making the sound seem fuller.

Not sure how else to explain it. Also having a hard time deciding which wires to keep since I like both.

Lets hope the difference I hear, which is very obvious, is due to the wires and not something else like the speakers themselves. Not sure if the manufacturing of these speakers is consistent across the line.

F1nut

Of course, the speakers are consistent across the line. I would never use Monster cable for anything.

VR3

Odd I haven't ever posted a more recent build! Little Rtia7 love!

PrazVT

Nice!

audioluvr

VR3 wrote: »

Little Rtia7 love!

That's not a little love! More like a Mona Lisa.

billbillw

Nice! A job for someone? Those are probably worth a lot more than I paid for my set of used A7. Those inductor coils alone...

VR3

Thanks guys!

The coils definitely add expense! They make a big difference getting rid of those super high gauge iron core inductors however!