Changes to Klipsch Cornwall IIIs.

aceinc · « **on:** 18 Jan 2021, 05:15 am »

This is the natural continuation on a thread I started asking for opinions on sound deadening on a horn. Here I go into the changes I made to the speakers based on both that thread, and Tyson's thread on upgrading Forte IIIs.

I became the proud owner of a pair of CW IIIs earlier last year at a great price as part of a larger purchase. Depending on how you value the various pieces I bought, the price could be anywhere from -$1,500 to +$350. They are B-stock and were originally purchased in 2013. I have had them in a 11'x15' den in my home for a number of months and occasionally listen to them mainly with the Mono Block Tube Amps and Tube Preamp they came with. Although I also listen to them with the tube pre & an Adcom GFA 555 Series II I use for testing.

Since I have so little invested in them I thought I would have fun with them. One of the bases/risers is water or rodent damaged, other than that they are cosmetically in 9/10 condition. Speaking of bases, Klipsch wants $150 for one base finished in Cherry. Bob Crites wants about half that for a pair unfinished. Unfortunately the Crites pair seems to be an inch deeper (14-1/2" vs 13-3/8") than what is currently on the cabinet. I have sent an email to Crites, and was unaware in the size change for the CW III. I decided to fabricate my own.

My initial plan for the speakers is to make the cabinets more rigid, add additional "insulation/sound absorption" and deaden any squawker horn ringing.

During my testing I played various bass/drum pieces to see if the cabinet panels would be excited/resonate. Using touch (not very scientific) I could feel the top sides & back all vibrating during different passages. So I feel some bracing could improve things. Also unscientifically I tapped the plastic squawker horn and the sounds it made seemed like they would be in the midrange (800hz-5khz), so I felt dampening that would be a good idea as well.

I had a variety of ideas on how to brace the cabinets, including putting in "ribs" cross bracing, etc. In the end I decide to follow what Danny & Tyson did in the Forte thread.

Here is my testing environment. I close the curtain on the door for testing to help limit reflections.

aceinc · « **Reply #1 on:** 18 Jan 2021, 05:20 am »

The test of one of the speakers before any changes looks like this;

aceinc · « **Reply #2 on:** 18 Jan 2021, 05:37 am »

Below are images which shows;

Squawker & woofer treated to stop ringing.
Braces used for one cabinet.
Inside of cabinet before & after bracing (after removing foam, and before putting new foam in).

The squawker damping was applied to the panels which seemed to resonate in the bandpass. I intended to do the entire woofer in deadening material, but I did every other section first and the sound of the steel frame when struck with my fingernail went from almost a bell to somewhere between a tick and a thunk.

The angle braces I used were all from various pieces of 1.5" scrap lumber (yellow pine) which I had laying about. They were cut to 1.5"x1.5"x9.5" long and had a 45 degree angle cut in each end. I used 3 up each side and 2 on the top. There was already two 2x4 (nominal 1.5"x3.5") yellow pine braces connecting the baffle (motor board) to the back. The braces in the ports were fabricated out of some primed 3/4" pine I had laying about. These were the most painful to install.

I have not listened to the results yet, because the cabinets did have one issue I needed to deal with, the bases. When I purchased them the previous owner showed me one of the bases had been water damaged, actually both bases were damaged, the second was not as bad or obvious. They looked good unless you turned the cabinets over. I have fabricated one base and replaced it. The other base is built, but is waiting on the paint to dry and holes to be drilled. The new bases are made from 1x3 (nominal 3/4"x2.5") finger jointed and primed pine painted black Duratex which covers my inadequacies as a cabinet maker. This increases the cabinet height by ~1/2".

I ran REW on the same cabinet I had run previously (its base was the first one). There appear to be subtle differences in the waterfall plot at frequencies above 120 hz. Some of the slow decay has been reduced in the time domain which I believe will translate into a positive change during listening. I will upload those to the thread once I copy them from my notebook (or upload them straight from there).

Tyson · « **Reply #3 on:** 18 Jan 2021, 05:43 am »

Hell yeah!!!! Nice work so far

Hobbsmeerkat · « **Reply #4 on:** 18 Jan 2021, 11:48 am »

Very nice! Even if the crossover itself isnt upgraded, all that extra damping, bracing and new foam will definitely help stiffen up the whole assembly, and allow for a much cleaner sound!

Definitely looking forward to your thoughts once you get a chance to listen to them after the upgrades!

Upgrading my dad's cheap Technics 3-way speakers involved a lot of the same processes & it helped with a lot of the lower mid/base region.

Im still considering looking at upgrading the cheap 3-part crossover to something with better values and point to point assembly. But ive got enough on my plate to focus on for now..

aceinc · « **Reply #5 on:** 18 Jan 2021, 02:40 pm »

I have listened to the first speaker completed some, and the cabinet vibrations (via touch) during drum sequences is greatly reduced. I actually compared one modified to one unmodified. Observations;

The bass sounded deeper
The cabinet vibrations on similar passages was much reduced
Efficiency seemed the same

I did not try to carefully compare the two. Unfortunately These are large & heavy cabinets so moving them is a pain. I had them side by side in the center of the room about 5' from the listening positions. So critical listening was not possible. I will move them back to their original positions once the other base is complete, and see what the sound like. Again not an ideal room (11'x15') for these massive speakers.

aceinc · « **Reply #6 on:** 20 Jan 2021, 01:13 am »

I've got everything set back up and as I write this I am listening to The Dave Bruebeck Quartet, "Time Out." I have the Cornwall IIIs powered by VTA 130 watt tube monoblocks driven by a VTA SP9 tube preamp fed by a NEC CD-730 CD player. Haven't pushed any thing but things sound pretty clean. I think the soundstage is better. Boominess is nonexistent so far. The limitations of my 11'x15' is still an issue.

In the charts below, you will see there doesn't seem much noticeable in the SPL/Phase charts but the waterfall plots seem to tell a different story to my eye. The most noticeable changes are in the 200hz to 800hz range.

aceinc · « **Reply #7 on:** 20 Jan 2021, 01:16 am »

BTW, the charts were all done using an Adcom GFA 555 II, not the tube equipment.

aceinc · « **Reply #8 on:** 21 Jan 2021, 02:13 am »

Caveat, I am not an audiophile, nor do I have a golden ear and my critical listening skills are suspect as well. Do not expect traditional effusive audiophile blather in my comments below. Call me a philistine, I'm cool with that.

Having said all that, I spent a few hours listening to mainly jazz last evening starting with the Dave Brubeck CD mentioned in my previous post. I also played a Pioneer Jazz sampler disk, some cuts off of a Telarc Hybrid SACD, a few cuts of Nora Jones and a Sheffield Drum CD. The first thing I can say is that none of the music I listened made me want to turn down the volume or get up & leave. I know this is a pretty low bar, but previously this setup would sometimes have that affect on me.

I found the sound for want of a better term, coherent. There was definitely 3D soundstage on some of the pieces I played, other's not so much. One cut, from the Pioneer Jazz CD (I will find the track, but I will need to relisten to the whole CD) had a very interesting phenomenon where some of the instruments sounded like they were 6-'-7' in front of the speaker and just off to my left. I must admit I had never had that happen before.

So what do I think I have accomplished with the changes? Originally the speakers were both shouty/harsh and boomy. Now they are more neutral and well behaved. The bass seems deeper but not boomy. They are still as efficient as ever, but my ears weren't left hurting/ringing after listening to them. In looking at the Waterfall plots, some of the lack of boominess might be explained by by looking at the 50hz area, where things look a little better controlled.

Here is picture of my listening environment taken from the listening position which is ~10' from each speaker. The VTA & NEC equipment used is on the table. the Adcom and Emotiva equipment on the floor is some times used for testing. The black speakers which are not hooked up are KEF Reference 103/4 and 101/2. I used them as a baseline/comparison in my original listening, because in many ways they are on the other end of the spectrum from the Klipsch.

I will do more listening over time if there is anything of interest I'll post it.

Tyson · « **Reply #9 on:** 21 Jan 2021, 03:39 am »

Philistine!! Hehe, just kidding.

But seriously, the "does it make we want to get up and leave the room" is a perfectly valid test. Heck maybe even the best test.

Cleaner, clearer, more pleasant to listen to, tighter bass, deeper bass. Those changes all mirror what I heard with the cabinet work on my Fortes. Really, the Klipsch Heritage speakers have good bones. They just need a little TLC to hear what they are really capable of.

aceinc · « **Reply #10 on:** 21 Jan 2021, 04:28 am »

Tyson, I have a thread going over on the Klipsch Forum as well (they have 2MB picture limitation) and it was suggested I could tame the dip at 5khz by changing/adding a capacitor. I may try this as well. I'd be interested in you and/or Danny's thoughts on this;

https://community.klipsch.com/index.php?/topic/197645-cornwall-iii-journey/&tab=comments#comment-2578411

persisting1 · « **Reply #11 on:** 21 Jan 2021, 05:37 am »

aceinc,

What dampening material did you use on the horns? Sorry in advance if i missed it.

S Clark · « **Reply #12 on:** 21 Jan 2021, 05:52 am »

You could experiment with large value caps across your woofer terminals to bring down that low bass boom.

Hobbsmeerkat · « **Reply #13 on:** 21 Jan 2021, 12:42 pm »

Quote from: persisting1 on 21 Jan 2021, 05:37 am

aceinc,

What dampening material did you use on the horns? Sorry in advance if i missed it.

Its a generic byutal-based dampener i had recommended that is essentially dynamat. Ive used it for a few different projects now.

https://www.amazon.com/dp/B01KZ5X7KO/ref=cm_sw_r_cp_apa_fabc_FzxcGbT28B41Y?_encoding=UTF8&psc=1

aceinc · « **Reply #14 on:** 21 Jan 2021, 02:26 pm »

Quote from: persisting1 on 21 Jan 2021, 05:37 am

aceinc,

What dampening material did you use on the horns? Sorry in advance if i missed it.

I don't believe I mentioned it, Noico 80 mil 10 sqft car Sound deadening mat, Butyl Automotive Sound Deadener, Audio Noise Insulation and dampening;

https://www.amazon.com/Noico-deadening-Automotive-Insulation-dampening/dp/B01KZ5X7KO/ref=sxts_sxwds-bia-wc-nc-drs1_0

10 square feet was enough with plenty left over.

And yes Meerkat recommended it.

aceinc · « **Reply #15 on:** 21 Jan 2021, 02:29 pm »

Quote from: S Clark on 21 Jan 2021, 05:52 am

You could experiment with large value caps across your woofer terminals to bring down that low bass boom.

The bass boom is gone (at least significantly attenuated) after bracing the cabinet and other mods.

dB Cooper · « **Reply #16 on:** 21 Jan 2021, 02:42 pm »

A very easy and effective way to accomplish this is with Plast-i-Clay (permanently soft modeling clay) or similar. Easy to apply (and remove, if desired). Maybe easier and possibly motre effective than the auto mat because the clay can make better contact with the irregular surfaces. Instructions are in Vol 1 issue 1 of the old Audio Basics newsletter, published by Audio by Van Alstine and available on their website. You may not need them though; it looks like you already know what to do and not to do.

The bass 'boom' may be a room effect though; possibly exaggerated by the corner placement (no other option in that space from the looks of it).

S Clark · « **Reply #17 on:** 21 Jan 2021, 06:39 pm »

It is most certainly a room effect. According to the graph shown, even after bracing there is a 10 dB rise around 80 hz. That a big rise. My room has a rise at 120 hz that required corner bass traps as well as adsorption panels. I could hear it clearly in jazz recordings as the bass player walked down a scale.... bum, bum, bum ,bum, BUM,BUM, bum, bum

aceinc · « **Reply #18 on:** 21 Jan 2021, 10:47 pm »

Quote from: S Clark on 21 Jan 2021, 06:39 pm

It is most certainly a room effect. According to the graph shown, even after bracing there is a 10 dB rise around 80 hz. That a big rise. My room has a rise at 120 hz that required corner bass traps as well as adsorption panels. I could hear it clearly in jazz recordings as the bass player walked down a scale.... bum, bum, bum ,bum, BUM,BUM, bum, bum

If you look at the before & after waterfall plots which were taken from one speaker in the center of the room. You will notice a ~50hz "lobe" in the before which is much smaller in the after. This is what I think is giving me the apparent reduction in "boominess."

Doublej · « **Reply #19 on:** 22 Jan 2021, 12:02 am »

Do you have any way of displaying a difference on the waterfall plots so one can see just what has changed?