Tri-amped RTi A7

gp4jesus

My sig tells part of the story - finally tri-amped one of my 'A7s. Here's a few pics:

New bigger BPs for all drivers! Less loss for the woofers!


An upside-down rear shot of the upper A7 panel - more BPs to connect the M&T. Each 4 ohm woofer has it's own new BPs, too. Now wired in parallel (they come wired in series) and gave each their own channel.


The mid is isolated from the woofers! Another upside-down shot looking in (& up) through the mid driver opening, a first-draft/experimental divider! That green-ish stuff is mineral wool.

Nothing more than two 1/4" thick panels** sandwiching the internal rib/brace, held in place by friction & 2 wood screws. Black stuff is Armaflex. Between the panels, several smaller pieces of same** layered w/Armaflex. In spite of what might seem flimsy, it's quite solid.
** I cut an extra 1/4" wood template.

If I decide I like it, I'll replace it w/a wood insert inside the brace. If I don't, pop the upper woofer, w/a shorty Phillips, it's out in minute. I would add something across the rib/brace instead.

Regardless I plan to have E-templates available upon request by PM.

Some other Build Details:
1. all internal wire soldered to the drivers, BJC 10 to mid, Canare 4S11to tweet
2. Clarity Cap PX, 68uf DC blocking caps on tweeter
3. @ the BPs inside, larger, thicker, gold-plated spade lugs crimped & soldered
4. Amaflex on much of the cabinet surfaces; driver magnets & baskets covered completely.
5. mid mounted w/ hurricane* nuts* and machine screws. woofers to follow
* See Jesse's "Fun with Rti A Speakers."

Side note: Other 'A7 unmodified making comparison easy.

First impression: love the cleaner upper mids & highs. Better defined, thunderous lows.

Some suggested a divider would change the voicing - not by my ears.

Tip: Anyone considering triamping their 'A7s: you WILL need a LOT of "adjustability" to balance the mids & tweets. Like tweets @ -6dB, the mids @ +6dB. Parasounds w/their adjustable inputs will help if your EXO falls short.

Finally this will "knot up the knickers" of the "warm amp camp" for these and other RTiA series speakers: woofer level between MINUS 4dB to MINUS 5dB! I came to this conclusion w/the warmest amp on the unmodded channel, the most neutral on the other. To be frank between the big cables and the Rotel RB-98X's high current 200WPC into 4ohms, I'm not surprised.

Hope this makes sense & serves to inspire. Tony

lightman1

No worries, Tony. Some of the best speakers ever made were derived from the inspiration of an existing product.
Keep up the curiosity.

JCsound

Man, you are going all out!! I'm all about experimenting and seeing how one can make something better. Usually most mods I do I make sure they are reversible, that way in case I don't like it I can put it back the way it was. Many companies put out products out there knowing that they could be better but don't because of specific financial goals or issues with the bean counters prohibiting it. Please do a review and let us know your findings.

P.S I recently bought some speaker monitors that come tri-amped from the factory, and they sound very very clean. I can't imagine how the A7's or 9's will sound tri-amped.

gp4jesus

Most humble thanks!

Tune in Saturday PM or sometime Sunday. I plan to photograph & post as I progress through the other speaker. If time & energy allows I may triamp my 'A6 CC, too.

Meanwhile, have a great Thanksgiving.

gp4jesus

Well Saturday worked out about as good as I could have hoped.

Many more pics this go around.
A shot of one panel of the Divider: 1/4" plywood.


2 of them w/ add'l pieces & some Armaflex & 2 wood screws sandwiching the brace below the mid and...

...Tah-dah! After I finish the other speakers i will cut, carefully fit & glue a 1/2" thick insert inside the brace

Some pics comparing Polk's internal wire to mine. Mid - BJC 10 gauge...


...Woofers - 8 gauge...

...THE cheapest way to "warm up" an RTi A tower or Center.

Outside shot of new mid & tweeter BPs minus nuts...


...inside shot of same


Backside of woofer BP plate "first draft:"

A bit tacky but WAAY sturdier.

BTW: I forgot to mention in earlier post Build Details - note add'l hardware to securely mount all BPs. This leaves the gold hardware to secure spades soldered & crimped to new wire.

My eldest son and VERY worthy assistant Armaflexing the drivers...

...he came up w/a few of the final ideas and assembly technics.

DC blocking cap



New bananas on left providing better conductivity. Gold plated brass, much more surface area, tighter fitting, low $, & that outer sleeve is plastic - far reduced chance of short if handling w/amp on.


Completed rear view. Note BJC sonic welded spades on mids



Unfortunately by the time I completed ALL the connections, etc it was too late to enjoy "the fruits of our labors" not to mention 500+ WPC! Tomorrow after work...

Until then... Tony

polk500

Hey Tony, I had Trey do the crossovers hence they are Modify Rti A7.

Cheers
R

gp4jesus

Polk500: massaged by Trey - that says it all!

I've considered picking up where he left off - I have two stock A7 XOs. I expect to have a stock CSi A6 by Christmas. Likely I'll hafta wait until I retire (2 years 10 months)

Tony

F1nut

New bananas on left providing better conductivity. Gold plated brass, much more surface area, tighter fitting,

Tony, your comments got me wondering, so I grabbed one of my MIT banana plugs and a rather inexpensive Parts Express binding post I had laying around. I measured the OD of the banana post, not the spring area at .155. I measured the ID of the binding post at .160. I don't think one can get a closer fit. I noted that there is absolutely no wiggle, tight as a virgin's *****. I also noted that the ball tip of the banana post fits tight up against the bottom of the binding post hole, which is something your new banana plug cannot do. Therefore, with all factors considered, I believe the MIT banana plug has more surface contact than your new plug. That said and no offense to you sir, but I can see why your original plug was not up to snuff.

Here's a pic of the MIT banana.

F1nut

I forgot to mention there's a post connected to the ball tip that runs down the center to the base, so even greater contact mass than appears on the surface.

gp4jesus

Jess: no offense taken sir. We're striving for similar things. Life* forces us to take different paths to get there.
* my larger, more complex than average family

After close inspection, I stick by my assessment of my new to old on fit & surface area. My new ones "bottom" the like yours though w/ a tiny fraction of surface contact.

My old banana has ~ the same surface area as yours in the pic. That center post you described certainly provides greater strength & ups the conductivity a notch or two by comparison to my old.

Felice Natale (Merry CHRISTmas)
Luke 2:7-14

Willow

Too bad you have no clue what you are doing

gp4jesus

Willow wrote: »

Too bad you have no clue what you are doing

What qualifies you as THE expert? This "isn't my first (bi, tri, or quad amp) rodeo."

Willow

Don't get your panties in a bunch. Didn't you see the wink at the end...... Cripes. Chill

gp4jesus

I'm so sorry for missing that and over reacting. I'll take it as left-handed compliment, but a COMPLIMENT just the same and wish you a very Merry CHRISTmas!

Willow

All good. I'm actually amazed at what you did. I couldn't even dream of that.

gp4jesus

Mille Grazie!

If you note the post dates early in these threads, you'll see this was a looong time comin' (overdue really).

http://forum.polkaudio.com/discussion/100364/thread-for-the-passive-xo-gurus-rti-a7/p1

http://forum.polkaudio.com/discussion/99538/will-they-rti-a7-soften-over-time/p1

I had a lot of time to learn about a great many details before the planets were in alignment and the moon was the right color!!

Now that they match, transparency unmistakenly notched up. Can't wait for all added & upgraded stuff to burn-in. Still haven't CRANKED up any 2 channel - looking forward to that big time.

Tony

PS: next on my list: a tri-amped CSi A6 over Christmas (I hope) .

gp4jesus

I came across FS thread for AQ speaker cable. I noticed similar if not the same style bananas as my new ones.

http://forum.polkaudio.com/discussion/175188/audioquest-rocket-88-with-72-dbs-10-foot-pair-speaker-cables#latest

Felice Natale, Luke 2:7-14

gp4jesus

Finally got to enjoy some AWESOME 2 channel, listening to Mannheim Steamroller Christmas. Their take on "Carol of the Bells" w/500WPC on tap - NEVER sounded so 3D & transparent!

Either get busy to bi or tri amp, or I urge you to follow the likes of F1Nut*, Jbooker, Polk500, JCSound**, & any other member that has (or had another) mod their RTi A series XOs,
* definite out-of-the-box work!
** biamped A9 w/modded MT filters!!

Felice Natale, Luke 2:7-14

F1nut

Nice to see you enjoying the fruits of your labor.

gp4jesus

Thanks. Like an impoverished person, not "enuf."

More to come...

gp4jesus

Enjoyed immeansly an extended session of listening (loudly at times) & tweaking Wednesday evening.

Cables & blocking caps settling in. A 15" passive DVC fed by a stout 400 WPC serving sub duties. Input fed through a parametric EQ. Tweaks kicked up system performance another notch or two.

Along the way, while listening to just the woofers, I discovered different LR response. Right channel seamed to have more slam. May be due to either
1. different stuffing arrangement or
2. a 981 driving the left and a 980 driving the right.
I plan to swap those amps next session.

Merry Christmas.

PS: triamped CSi A6 in progress. Should finish mid day tomorrow.

gp4jesus

I've determined Rotel's RB-980BX is the preferred 900 series* amp to drive woofers.
* versus the RB-981

Early New Year's Eve afternoon wife took several distractions & interuptions (kids) w/her somewhere allowing over 2 hours of peace.

I swapped the 980 w/the 981 several times; switched the L*&R** towers to the right & left sides of the room respectively also - right side is ~3' from an outside wall affecting response. In the final stages I placed them side by side, changed XO settings, and had my son* do the switching*. That* made "biased listening" impossible.

They DO sound nearly the same otherwise. The 980 has "it" in the lowest register that the RTi A7 is capable.

Happy 2017! Tony

gp4jesus

Recent discovery: both Rotels run cooler driving 4 ohm woofers @ high volume than band limited 8 ohm @ moderate volume.

gp4jesus

Watching "Days of Thunder" on Blu-Ray @ -11... ...priceless!

gp4jesus

Just upgraded to a DSP laden EXO. Near unlimited XO & EQ tweaks.

Choices include but not limited to:
Gains +/- 12dB & adjustable delay/time alignment for each driver
6, 12, 18, & 24 dB slopes, butterworth and/or LR filtering, and, between drivers, overlap or a gap
EQ to your hearts content! Graphic & 8 bands of full parametric plus 2 shelving settings w/user-selectable corner frequency & slopes.

If all that is too much let the built-in "Wizard" set the driver gains, delays & system EQ for you! Connect the calibration mic, place @ your "hot seat", let the "Wizard" do the rest!

Tony

PS: moving soon

F1nut

Don't drive yourself crazy, Tony.

gp4jesus

Am I driving myself crazy, Jess? My bad.. Perhaps I'll put it in park by the end of the year.

First impressions: more transparent & cleaner especially in the upper octaves.

Listened to Boston's first album. Hardly an SDA experience w/an old recording but I couldn't miss how many of the guitar solos are layed on top of the mix.

I plan to save the remaining tweaks, running the Wizard to get "its opinion" & system mods for after the move. We close on the 17th.

Cheers. Tony

gp4jesus

Moving this weekend. Dismantled my system last weekend. I MISS my LCR's mids, highs, & transparency not to mention the authoritative thump from my big sub and its power.

Running 2.1: Rotel 980BX driving unmodified RTi A3s & 1' cube Audio Pro sub.

Can't wait to get moved.

Tony

gp4jesus

99% moved in; ~85% moved out

Power distribution: 3 dedicated 20A feeds.

LCR: reconnected w/an upgrade: separate dedicated L & R P'sound 1000s for mids & tweets!

Rear channels not mounted much less connected to date, however... New house has different listening area arrangement w/frequent floor traffic across same. Does not allow ANY on-the-floor wiring from front-to-rear. That said I hafta run it through the crawl space w/WAF touches.

Tony

gp4jesus

Long overdue update (C. July).

Completed crawl space signal feed & power distribution for surround* channels - mounted same*. Wife LOVES the clean work.

Added EXO to tweak dedicated surround L&R subs* - added another dimension to my system.

Since then picked up two MORE of these 27hz gems*, one for each corner taking things up yet another notch.

Happiness is multiple subs.

gp4jesus

The latest rendition of my signature tells the power amp config actually for about the past 3 years. In posts above over 3 years ago I had P’sound 1000s for the mids and tweeters.

A long unmentioned detail about RTi A7s for which I MUST say I AM SORRY... The woofers are 8 ohms each. Of course in series, as that’s how they’re wired, they load your amp/AVR at 16 ohms, netting between 10 & 11 ohms below 125 hz. Some time after I completed the above work in, about 3 years ago, I checked the woofers w/meter to learn they are in fact 8 ohm drivers.

For over 10 years I had erroneously posted they are 4 ohm drivers (in series 8 ohms). I often expressed great concern for loading amps & especially AVRs at 4 ohms below 125 hz as the 8 ohm mids are in parallel w/the woofers below that frequency.

I would encourage anyone not afraid of work that’s considering active bi or tri amping on any loudspeaker to forget your fear, drop your guard, and get to work. The results are their own reward!

Tony