Seas H1212

[Armand]

Hi all. Has anyone figured out how to remove the dispersion screen on these tweeters? A previous SEAS M-dome I used really opened up considerably when I removed the mesh screen, but it's removal was easy: it pulled right off. This looks a little more difficult. Thanks!

[JRT]

I have not tried to pull the screen off an H1212, and I don;t recall seeing any modifications to that. But I did want to mention that DLR has a page describing some modifications he tried on the Dayton RS28 that I think might be very applicable to Seas' H1212.

http://www.speakerdesign.net/dayton_rs/tweeter/reference_series_tweeter.html

Be sure to take a look at some of the other work he has done, some interesting stuff on wool felt, diffraction, tweeter mods, etc.

http://www.speakerdesign.net

[EdL]

I have pulled the hexagrid off. It surprised me how well it went.

Begin with a long, slender "tool". The tip needs to fit into the hexagrid openings on an angle close to the faceplate. I used the tip of the file on a set of nail clippers. Use a small piece of paper. Fold the paper to increase the thickness. Use it or similar material to pry against.
The hexagrid is set into an elastic adhesive in a groove that surrounds the dome. It will give up, slowly. Begin by selecting the point into which you can insert your tool and pry gently. You want to stop when you see the first movement of the grid. Move to a new spot, maybe 1/4" around from the first and repeat. It should become easier to move the grid as you progress around it. Continue in the same fashion around and it will separate.
Stop if you see any deformation of the grid. With care it can be removed without deforming it. This will allow it to be put back if you wish.
After removal the adhesive will remain in the groove. It can be removed in small pieces. Use a tool that is softer than the underlying plasctic to avoid scratching it. A tooth pick will work. Metal works too. It just requires more care.

[Armand]

Thanks Ed. Did you like what you heard after removal? Did you notice a decrease in dispersion?

[EdL]

Armand,
Haven't heard them yet. I just did this 2 nights ago in preparation for building waveguides. That will take awhile.
Beware-the lack of a phase shield may make the H1212 sound bright. It may be the "opening up" you are looking for.

See Ya!

[Jonasz]

Here's a little visual guiding for you. The text is in swedish but I bet you'll manage anyway!

http://www.faktiskt.se/modules.php?name=Forums&file=viewtopic&p=250608#250608

[Armand]

Thanks guys.

Jonasz: Can you tell me if that gentleman likes the tweeter better without the plug?

[Armand]

After much A/B'ing, I've found the tweeter to sound a tad bright without the phase plate. (At the same time, a slight spitty quality disappeared). What's interesting though, is that the FR plots indicate otherwise. See attachments. Thanks to Bjorn of SEAS for the plots. So what do you guys infer from these plots?

[cobbpa]

Hmmm...definitely interesting. Makes me consider removing it for center channel use. I don't know of much else to note since I'm not very experienced, but the way in which (without the plate) on-axis slopes downward while off-axis gets a boost is interesting.

[ThomasW]

For things like this using the cheap stainless steel dental pics sold by Harbor Freight tools makes life easier.. They're also handy if you want to descale your teeth as a DIY project.... :wink:

[Armand]

Hmmm...definitely interesting. Makes me consider removing it for center channel use. I don't know of much else to note since I'm not very experienced, but the way in which (without the plate) on-axis slopes downward while off-axis gets a boost is interesting.

This is probably responsible for the perceived brightness I noted (along with increased detail, I failed to add). This would make sense since my speakers are, unfortunatley, setup on the sides of and directly ahead of a 6 1/2 foot wide solid oak cabinet. I'll do more listening before I determine what I like best.

To remove the plate, I used a thin-tip needle nose. They came off easily with no deformation or glue showing. When you slip them back on, they fit in the original groove and basically recenter themselves.

[tktran]

As usual, this is exactly why I don't care for subjective opinions.

If you overlay the graphs over each other, you'll see after removing the phaseplate, the FR droops off, both on-axis AND OFF-axis (starting around 6Khz)
Also the ultrasonic resonance is both lower, and louder!

If it was better without the phaseplate, why would SEAS bother to install one?

[cobbpa]

Touche, tktran. I was looking only at the lines relative to each other. You're right. The only advantage off-axis looks to be 60* 15khz & up; hardly a gain. I was just decieved by all 3 lines being closer together; made me think too quickly that the off-axis ones had risend sifnificantly.

[Armand]

Well, if we listened to graphs, it would be easy. AR blew away the flat FR long ago. And there are many DYI'ers that don't like phase plates and think that the removal is beneficial. But guess what. I'm apparently not one of them. But not because of FR, I don't think.

That said, I had the opportunity to do more A/B'ing courtesy of a day off from work, so from my subjective notes: without the plate, the sound is definately tilted up. There's more detail with HF instruments but I also noticed a lack of focus as images were more spread out. Also, mass vocals in chorus examples sound thin and could no longer differentiate male and female voices. Apparently, the change even affected the midrange somehow. But HF intruments sound more detailed. Cymbals and triangles sound more real but not in the confined acoustic. They sound separated from the other intruments.

With the plate I hear a more coherent soundstage with a more laid back treble. Male vocals don't sound thin but there's less detail in HF instruments. But the HF instruments fit in the soundstage venue now.

Why I heard a tilt up in the high end, I don't know. But it sounds best with the plate, in my system, in my room. Thanks for the responses. And tk, you're right. Why would any MD manufacturer use a phase plate, because they all do? Because it works based on my ears. Sorry for the subjective opinion, though.

[beto]

Armand,
I removed the grill too and noticed exactly what you describe, verbatim, so I ended up putting the grill back as I like it better with it on... I agree with your subjective opinion as I had the same experience...

[Armand]

Now I know why they call it a phase plate. Things sound slightly OOP in the highs. That would explain the image issue. It would also explain why a FR graph wouldn't matter.

[EdL]

Very interesting observations. Is there any speculation about contributions of the hexagrid? Is the grid acoustically transparent?