Tri-amped RTi A7

gp4jesus

Trey’s custom RTi A7 diffraction pads

F1nut

That's a lot of pad. Any impressions?

VR3

Looks great!

gp4jesus

F1nut wrote: »

That's a lot of pad. Any impressions?

Very inexpensive tweak!

Speakers more transparent, instruments more defined.

Any GRP and in particular, (on Sheffield) Dave Grusin’s “Discovered Again.” Like the musicians are in front in you, in the room!

gp4jesus

VR3 wrote: »

Looks great!

a credit to your dedication to your craft!

xschop

Decapitated this dedicated midrange....

xschop

If a 6.5" OD x 4.5" long cylinder can fit up thru the cabinet from top woofer hole to the midrange hole, then a schedule 80 pipe can be used to compartmentalize the midrange. You would only loose just a couple cube inches of volume...

gp4jesus

The “A7 schedule 80” mid* closure. Xschop’s (Rob) practical work around in place of a divider to separate the same* from the woofers. I believe for one to realize best results, they should pursue active bi-amping the woofers and mids plus upgraded mid/tweeter passive XO parts.

In pursuit of Rob’s brainstorm, I’ll take measurements of the space inside the closure brace that’s beneath the “mid port” and the upper woofer. Further, following reassembly, I’m gonna test via RTA if stuffing that mid port affects the frequency response much if any.

Thanks for your ideas, Rob.

Tony

xschop

Just suggested it as the piece of sch 80 I still have for 6500 gasket template also fits these RTiA mids perfectly. You could mount them by clocking 4 countersunk fasteners 45 degrees on the cabinet flange that sits right beneath midrange flange.

In this instance, you'd still want to foam the inside of the frame baskets and stuff the new cylindrical chambers with dacron/wool etc.

xschop

Also an interesting caveat about these mids is that the spiders look like they've relaxed at a slightly forward position by @ 0.050" (perhaps due to shared cabinet volume with woofers exerting pressure?)

That 0.050" difference is the only difference between a mw6500 phase plug and this one's required base length.

gp4jesus

Hmmm… I finished the pre-Tri amp “surgery” over 5 1/2 years ago - nearly half their lifetime w/me.

OTOH I uncovered the ‘A7s bass heavy/”spirited”volume “mid” driver problems shortly after purchase. That’s when I began some internal rewiring and trying other “band-aide” type tricks to cope w/the problems.

More later, gotta navigate

Gardenstater

xschop wrote: »

Decapitated this dedicated midrange....

Aluminum voice coil former with 4? holes to help cool the voice coil? How permeable to air is that dust cap?

xschop

ZERO permeability to atmosphere. It's like a butyl material and heavier than classic MW woven dust caps.

xschop

Ace was back at delivery work...Im going to try and re-align the flange on left that is .200" bent and the VC is rubbing, although magnets are not shifted (assuming since large magnet shield won't budge even with small prybar) I checked with shims as Coil clears either side except when relaxed also.

xschop

These uprights are weaker than classic MWs that can take more abuse.



I also find it interesting that the much thicker surrounds aren't actually glued on to frame like classic MWs. Both this one and good one can easily peel back the surround....



This came in handy in this situation.
Locked frame into my articulating vice without damaging the surround. Bent it back to 90 degrees vert. using a small prybar on the compressed frame pivoting off vice jaw base and VC looks like it's realigned about perfect. No rubbing while pushing on cone any direction...

Gardenstater

Yikes! Amazing! That's not for the faint of heart.

gp4jesus

xschop wrote: »

These uprights are weaker than classic MWs that can take more abuse.



I also find it interesting that the much thicker surrounds aren't actually glued on to frame like classic MWs. Both this one and good one can easily peel back the surround....



This came in handy in this situation.
Locked frame into my articulating vice without damaging the surround. Bent it back to 90 degrees vert. using a small prybar on the compressed frame pivoting off vice jaw base and VC looks like it's realigned about perfect. No rubbing while pushing on cone any direction...

May you have wisdom of Solomon coupled w/ strength of either Samson or the Hulk to complete this incredibly demanding task.

Tony

gp4jesus

The first “plugged” RTi A7 mid w/ painted trim ring. I found I prefer flat black. Even matte black to me appeared too glossy next to the Polk finish.


Another painted “detail.”

More pics of this ‘A7 w/ details & tips to Hurricane nut mids & woofers to follow. Earlier tonight I returned the above* ’A7 in its current state of mods to it’s rightful place as the “R” tower. My son helped me move the “L” tower twin to my shop to begin bringing it current w/ the former*.

xschop

Those look slick. The felts look factory too.
Polk should take some design cue here.

gp4jesus

xschop wrote: »

Those look slick. The felts look factory too.
Polk should take some design cue here.

Thanks but I can only take credit for providing the cash. Trey deserves most of the credit - he (laser) cut them! He also gets 5 stars for patiently working w/me on the shape.

LH tower in progress. I’ve applied the first coat to the Woofer trim rings. Meanwhile I’m about to begin filing flat spots on 12 H nuts.

Stay tuned!

xschop

Yes, Polk should hire Trey.

gp4jesus

Some tools and tips to Hurricane nut (H nut) your speakers:


a 9/64” tip & a Craftsman* cordless screwdriver. I use it* like a regular to crack the screws loose. Then at slow speed, have the motor do the rest.



Views of jig using channel locks, & 2 parallel clamps to hold two H nuts, w/one of those 8-32 screws through them. A mill **** file makes quick, easy work to file a flat spot…

…a bit bigger than 9/16” across. This needs more filing.



you’ll need a #7 drill bit as the original holes are too small


Drill gently. Getting too aggressive makes an off-set hole…


…then carefully shave the rough stuff w/ small sharp knife or utility knife blade.

Cont’d in next post

F1nut

A Dremel with a cut off wheel works a helluva lot faster for cutting off that piece of flange. If you try to install hurricane nuts for the bottom port I suggest finding someone with very small hands. I tore my hand up installing mine.

gp4jesus

These slip join piers are helpful during the actual H nut install


If you’ll look very closely at the thin part of the nut, you’ll see a diagonal swirl of metal going left-to-right down the side. During install, that causes the nut to rotate clockwise. So if you begin…


…w/ a tiny bit more than you see showing here…


…when inserted, it should look like this.

I hope this makes sense. I discovered I could use 2 #8 washers & an 8-32 screw to “pull” the H nut up into the hole.


This example is partly finished. Note the washers under the screw head.

1. Tighten the screw w/your fingers until the H nut makes contact underneath.
2. use the Craftsman like a regular screwdriver to turn the screw
3. After about 2 full turns, grab wide part of H nut w/ the slip joint pliers.
4. As you further tighten the screw very slowly begin to rotate the pliers clockwise (you’re almost finished) keep an eye underneath. Slight over or under rotation of the wide part is ok.


a test fit minus trim ring to make sure the screws go in easily. Remove screws then…


…float the ring above the front baffle while putting the screws in just a couple of turns. Once they’re all in, turning easily, the ring should drop into place. Continue by giving each 1-2 turns, then move to the next. I used the tip holder to finish “hand tight.” Then used the Craftsman I gave each by hand no more than about 1/4 turn. Then move on to the next driver.

I neglected to mention at the top of this series of posts, I had decided to finish “H nutting” the woofers after remounting the now “H nutted” & plugged mids. I chose to document the process for those that have considered doing this and some of the tweaks they’ve read about on the forum.


Enjoy! Tony

gp4jesus

F1nut wrote: »

A Dremel with a cut off wheel works a helluva lot faster for cutting off that piece of flange.

Yeah…but I already had the file. 3-4 maybe 5 minutes tops. I realize a Dremel is a useful tool though.

F1nut wrote: »

If you try to install hurricane nuts for the bottom port I suggest finding someone with very small hands. I tore my hand up installing mine.

I’m certain you’re right about that. I looked at that…again. If you had not noticed I limited the port to paint.

My Center is next. Very soon BTW

Meanwhile in a few years after “the herd thins…”
I’ll relocate the system to a different (bigger) part of the house…
I’ll expand to 7 channels and…do a few things I’ve dreamt about for 30+ years and…



…well…we’ll see.

Cheers Jess. Tony

gp4jesus

So. Was all the work worth it? You bet it is!

I’m also more satisfied w/their appearance, too now that more of the formerly silver is black, save for the tweeters and their bezels. Stay tuned to my CSi A6 thread.

I tested the improvements listening to Dave Grusin's "Discovered Again" on Sheffield. I experienced sounds, musical textures, & details I never heard before! "Plugging" in addition to the incredible “bang for pennies” "foaming*" of the frames are both worthwhile. For any music lover using RTi or RTi A series speakers, get in touch w/ the man - Xschop! He’ll hook you up.
*find Gardenstater’s Foam thread

Some details about the session:
1. To minimize distractions, I limited output to just the mids, EXO'd 125 & 2.2K. Tweeters* and woofers** kept silent by either disconnecting* or leaving the power** off**.
2. I played it on my 10 year old Samsung Blu-ray player, requiring me to force the Outlaw to 2 channel. My Philips CD player would caused the Outlaw to default to the same. Further my CD player's digital out jack has become intermittent but I’m confident I can repair it.
3. It's tough to get the living room to myself. In my hurry I forgot to allow time for the amps to warm up before the session. Next time…

The only variables from "pre-plugged" are the phase plugs, a 😬😢bare* floor* (it's complicated*) & one of the '7s already had an H-nutted mid. Per George, while the mount is more secure, they affect driver coupling only slightly, if at all. Soooo...

I look forward to future similar listening sessions of just mids w/ other material eventually full range.

I neglected to mention in the H nut series, I believe Polk never intended for their screws to ever come out. Voice of experience - they’re VERY easy to strip! ALWAYS hand tighten. Should you decide to “foam” and “plug” your mids, a single removal and careful remount w/no future tweaks planed should not compromise the closure screw holes.


Divertiti ad ascoltare!
(Enjoy your listening!)

Tony

xschop

Any detection of low-mid bass attenuation?

gp4jesus

No. Consider…

My pre-plug listening test using the same
CD,
BDP
XO frequencies
only the mids powered
one mid was “foamed,” one was not.

The ONLY frequency response difference I could hear was an undeniable raspiness at the top of the unfoamed mid’s range. That detail aside, I also listened to each channel separately. I repeated the same w/my 16 year old daughter w/out telling her why.

We agreed the only difference we heard was
a raspy top end from the unfoamed mid.

You can read my post “plug” comments in an earlier post.

I hope that answers your question, Rob

Tony

xschop

Good deal. Nothing like real world experimentation.

Gardenstater

As expected! Thanks Tony!

Polyurethane Open Cell Acoustic Foam. The smallest thickness they have data for is 1/2". Imagine what 1/4 or 1/8" would be like.