NHT diffraction foam fix.

[Daddyjt 9,805]

About the only Achilles Heel I’ve run across on the NHT speakers is the strip of diffraction foam that many models (2.5, 2.9, 3.3, etc) have running outside the tweeter/midrange drivers.  The foam tends to degrade and crumble over time, creating quite a mess. 
 

 

I have been experimenting with various materials, and I have settled on a solution - 1” wide x 1/2” thick adhesive backed felt.  I tried open cell foam, closed cell foam, EPDM rubber stripping, and felt.  I left one speaker with the stock foam, and compared it to the other with the various other products.  The felt is by far the best compliment to the speaker, even sounding better that the original foam - degraded as it was. 
 

The worst part of the job is removing the old foam.  It tends to come off in a crumbly, tar-like goo that’s just gross. I used denatured alcohol to soften and remove the base adhesive. the whole removal process is MESSY - be prepared. 
 

The felt came in a 10’ roll for about $20.  I cut the strips to length and rounded the top and bottom on my disc sander, and trimmed the stray edges. The felt is 1” wide, as I said - the original foam strip was 1.25” wide.  Therefore, I mounted the new, narrower strip the same distance from the drivers, leaving the extra 1/4” on the outside.

 

 

 

 

 

@PhilDent I will be sending you a set for your 2.9 pair.:-)

 

[PMAT 2,054]

Nice job. Looks good. 

[PhilDent 1,984]

On 11/5/2020 at 6:33 PM, Daddyjt said:

I will be sending you a set for your 2.9 pair.:-)

Sweet. My strips are pretty deteriorated.

if I remember correctly the strips on your 2.9s were aftermarket.

 

Edited November 7, 2020 by PhilDent

[dennismiller55 4,823]

Nice!

[Daddyjt 9,805]

7 hours ago, PhilDent said:

Sweet. My strips are pretty deteriorated. If I remember correctly the strips on your 2.9s were aftermarket.

Yes, the ones I just brought home from your place (Thanks again!) had closed-cell foam with such a low density that it might as well not even be there - but it looks really nice:-)

[Dadvw 2,891]

Good job Daddyjt! Boldly going where I will never go........grin

[PhilDent 1,984]

Got around to removing the gooey mess of the old NHT diffraction strips.

Thanks to Mark @Daddyjt they are now refreshed.

[Receiver2000 4,376]

Nicely done sir!!!

[Daddyjt 9,805]

43 minutes ago, PhilDent said:

Got around to removing the gooey mess of the old NHT diffraction strips.

Thanks to Mark @Daddyjt they are now refreshed.

Wasn’t that the gooyest mess!?  Looks good man:-)

[Sk1Bum 12,439]

Looking forward to getting these replaced...    Thank you Mark!

 

 

 

[RodH 4,866]

Question:

 

How much different do they sound without the fuzz strips?

 

Come on, you cleaned them off, did you not do a comparison? 😁

[Sk1Bum 12,439]

49 minutes ago, RodH said:

Question:

 

How much different do they sound without the fuzz strips?

 

Come on, you cleaned them off, did you not do a comparison? 😁

 

These old ears didn't notice any difference.

[RodH 4,866]

Some guys like the fuzz strip, some don't, others don't really care.....

[Sk1Bum 12,439]

1 hour ago, RodH said:

Some guys like the fuzz strip, some don't, others don't really care.....

 

I think they look better waxed clean. 

 

 

[Receiver2000 4,376]

Does the white strip show through the grille material?

[RodH 4,866]

Fishnet grills?

[Brian_at_HHH 2,720]

I'm going to guess, that like @Sk1Bum, with my ears, I probably won't notice any real sound difference, but I am convinced that the foam NHT used self destructs. 

 

I don't think I've ever seen a currentish picture of a NHT where they weren't in a semi- or mostly dissolved state.  Mine certainly are, and just the thought of something decent, in their place is something I'm looking forward to.

 

@Receiver2000, I'll try to take some pictures of the results, to post, so you can see if the "pantie lines" show.  

 

[Brian_at_HHH 2,720]

On 12/1/2020 at 12:03 PM, Receiver2000 said:

Does the white strip show through the grille material?

 

Sorry for the delay on finally responding to this, but I've now gotten that horrid slimy, gooey godawful mess off my speakers and Mark's felt solution in place.  I've dealt with some really gut wrenchingly gross things in my life, but I can honestly say, the feeling of that stuff was jus about the grossest thing I've ever touched!  Shudder!   🤮

 

Now that it's done, I can definitely say, that "no, one cannot see the light coloured felt through the speaker grills:

 

 

The fist picture shows what can (or rather cannot) be seen through the grill, and the second is a peak under that grill.  Now I did try to really enhance the 1st pic, to try and force even a trace to be visible, but Nada, nein, nope, nothin'.  

 

And just for giggles, here's one of my impromptu cat-scratch-excluders.  I'm just using a melamine shelf (poorly positioned here) to protect the side woofer, when not in use. Try to ignore all the reflectons of @#$^ in and around the speakers - that's the downside of a shiny black finish.

 

 

BTW, just a reminder to anyone doing this kind of work:  brass screws look very nice but brass is DECORATIVE ONLY - DON'T TRY TO USE IT FOR STRUCTURAL PURPOSES.  You would think I would know that by now, but the allure of "Oooooh Shiny!!!!" got me once again!   Doh!!!!  Trust me, here, just don't do it.  Nice shiny stainless STEEL looks Perfectly good - really!  Brass bad, Steel GOOD!  Just repeat it as a mantra when building things.    

 

Lesson learned again ... until next time..  🤪

 

Thanks again to @Daddyjt for the fantastic solution to that awful, self dissolving foam that NHT used!   

[Daddyjt 9,805]

Awesome Brian! Glad they made it up there without surffering the same treatment as @Sk1Bum suffered!  I gotta say Brian, you must REALLY love your cats, lol!

 

@RodH , yes - the strips do make a difference - mostly in off-axis listening. They tend to smooth out the highs, and they also help to create that great front-to-back soundstage. 

[oldtexasdog 2,481]

Hmm Very Interesting? 

I was not aware of these speakers. Looked them up and they seem very reasonable in price and as several of you seem familiar with them thought I would ask what their redeeming qualities were?

 

[Daddyjt 9,805]

It’s a bit of a winded read, but this shootout it what solidified these as my favorites.  Their imaging is spectacular, and the level of clarity is superb. Usually the level of clarity I find in the NHTs is accompanied by a bit of fatigue (Klipsch is a good example of this), but I can listen to the NHTs for hours with zero fatigue. The bass response is nothing short of incredible in its depth and detail, with no boominess.  I have already sold my Kappa 9s, and I’ll probably be parting with the Legacy’s soon as well... 

 

 

[Sk1Bum 12,439]

I went and looked at the 3.3s I have on what I read here about the imaging, bass, clarity, and I have to say I am not the least bit disappointed. The 3.3s are a huge improvement over the Infinity RSIIIb's I had as front speakers in my home theater. The more I listen to these, the more I like them. As Mark said, no fatigue, they love the M1.0t mkII opt002 amp, and I plan on testing them with a pair of M500t mkII's biwired.  

 

The only drawbacks I've found so far are the shape and the weight. The 3.3s are almost 130 lbs each, so I won't be moving them down a hallway to check them out with my main stereo rig.  The weight might no be so bad, but the shape is damn cumbersome, making it all but impossible to move them without help. These 3.3s are 31" deep, 44" tall (with spikes), and about 6" wide. The outriggers are a must for stability.

 

They do sound great though. My first listen to them was in the previous owners garage, with a stock C11, M1.0t mkII opt002, and an oppo 103. It was very impressive. The soundstage is the most impressive attribute to me, because of it's depth. Then when I hit the SH button on the C11, I knew I was taking them home, even if the previous owner wouldn't budge on price.  When the previous owner hear it, I was afraid he might change his mind about selling.  

 

They don't have the clarity of my Martin Logans, nor do they have the bass impact, but the Martin Logans are helped with a 500 watt (1K watt peak) 12" sub.  

 

If you can find a nice pair of 3.3s under $1500, I'd call it a good deal. They don't come up for sale very often, and they're usually in the $1800 range for a nice pair. 

[Brian_at_HHH 2,720]

17 hours ago, Daddyjt said:

Awesome Brian! Glad they made it up there without surffering the same treatment as @Sk1Bum suffered!  I gotta say Brian, you must REALLY love your cats, lol!

 

Well, in this case the protection is not optional - my main floor is all open concept, no no locking the bad little beggars out.  And speaker grills like the NHT's are at an Oh-so-perfect height and are a perfect texture to be irresistible scratching posts.  If I don't do something to protect them when they are not at cat-scatteringly high volumes 🙀, they would be shredded in no time.

 

And yes, my 3 little demons are basically my only real family these days so they do get spoiled - but not to where the kids are allowed to play with dad's stereo!  😸