Seas DXT vs Seas 27TBFC/G + WG300

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digitalthor

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Joined 2018
Hi everyone :D


I've been very interested in waveguide lately. But cant really seem to find my ground.
Since I have a small midrange and an existing 4 way design. I want to build something like it, but with a little different design and more constant directivity. So I found the Seas DXT that is so popular in Kii3 and Grimm Audio, which I also like to listen to, when I visited different exhibitions.
The DXT might be a little to small.... maybe. But I do have a 5" hard cone midrange for the project.
Then I saw on sound imports, that they have guide for waveguides - haha :p
SoundImports | "Wave guiding" your favorite tweeter. - SoundImports
What if I use the Seas Prestige 27TBFC/G with the Monacor WG300..... would that make a wannabe Seas DXT, but larger?
I can see on Heissmann acoustics, that the DXT can peform well. But since the price is very close - then I could not help to think that this combo might work really well.
Anyone seen someone do this?


Regards
 
Zvu

Zvu

Member
Joined 2009
With waveguide that large you have much better directivity control and boost under 10kHz so you can lower the crossover point substantially.

Since DXT doesn't have a ferrofluid in the gap (and not without a reason), i'd suggest Seas 27TBC/G instead of 27TBFC/G.
 
Zvu

Zvu

Member
Joined 2009
I'm using WG148R to cross to Seas L15 at 1650Hz. You definitelly do not need a waveguide that large if you're using a 5" midwoofer.

I wouldn't say DXT is easilly crossed at 1800Hz. I'd say that is tje lowest crossover point with that tweeter and demands steep filter to protect it from getting damaged.
 
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Zvu

Zvu

Member
Joined 2009
Ring radiator at the moment, but i have used Morels and Seas (soft dome) in past - i posted measurements of those. I tried to fit Seas 27TBC/G but eventually failed. Very tricky front plate with mesh that leaves quite a gap when removed.
 
giralfino

giralfino

Member
Joined 2009
The L15 has a very strong breakup at 8KHz. Without seeing any distortion plot, I'm a bit worried of a 1.6KHz high 5th harmonic breakup induced distortion, so maybe this is a good crossover point.
You probably don't need the WG300 with a 5" driver, and the WG148 should suffice. The latter can be mounted easily to tweeters with a flat faceplate, but the 27TBFC/G doesn't seem to fit because of the grille, you could have more luck with the soft dome equivalent TDFC.

Ralf
 
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digitalthor

Member
Joined 2018
giralfino said:
The L15 has a very strong breakup at 8KHz. Without seeing any distortion plot, I'm a bit worried of a 1.6KHz high 5th harmonic breakup induced distortion, so maybe this is a good crossover point.
You probably don't need the WG300 with a 5" driver, and the WG148 should suffice. The latter can be mounted easily to tweeters with a flat faceplate, but the 27TBFC/G doesn't seem to fit because of the grille, you could have more luck with the soft dome equivalent TDFC.

Ralf
Click to expand...
Thank you.
I have a fully active system, so with a DSP I should be able to tame the breakup - 6Khz lower than the cross-over-point??
Leaning more and more towards the DXT :)
 
Zvu

Zvu

Member
Joined 2009
giralfino said:
Most breakup induce odd (n) order distortion at 1/n of the breakup frequency. So for the 8KHz breakup I expect a 3rd harmonic distortion peak at 8000/3 Hz and a 5th harmonic peak at 8000/5 = 1600 Hz.

Ralf
Click to expand...

Quite right Ralf. 5th harmonic peaks at about 1600, so anything at or bellow that is worth looking at:

Disto-PC-L15.jpg
 
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ernperkins

ernperkins

Member
Joined 2009
Zvu said:
Quite right Ralf. 5th harmonic peaks at about 1600, so anything at or bellow that is worth looking at:

Disto-PC-L15.jpg
Click to expand...

That 5th harmonic peak is actually occurring at 5 X 1600 = 8000 Hz. That's because in most distortion graphs the frequency of each harmonic is divided by its order (D2 divided by two, D3 divided by 3, etc.) so it fits in the same frequency range as the fundamental. I call this frequency scaling, but others call it frequency normalization. The attached paper explains it better than I can: see section 2 and figures 4 and 5.

REW has a feature to show this. It normally plots distortion with the harmonics' frequency scaled, but has a "Plot harmonics at the harmonic frequency" option. That option removes the frequency scaling and plots the harmonics at their actual frequencies.
 

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Zvu

Zvu

Member
Joined 2009
ernperkins said:
That 5th harmonic peak is actually occurring at 5 X 1600 = 8000 Hz. That's because in most distortion graphs the frequency of each harmonic is divided by its order (D2 divided by two, D3 divided by 3, etc.) so it fits in the same frequency range as the fundamental. I call this frequency scaling, but others call it frequency normalization. The attached paper explains it better than I can: see section 2 and figures 4 and 5.

REW has a feature to show this. It normally plots distortion with the harmonics' frequency scaled, but has a "Plot harmonics at the harmonic frequency" option. That option removes the frequency scaling and plots the harmonics at their actual frequencies.
Click to expand...

Tomătoes - tomātoes

Good paper though. Thanks.

I won't be near my computer for a few days. Could you make a screenshot of that for the same measurement ?
 
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digitalthor

Member
Joined 2018
Accuton C82-T8.JPG


My Accuton midrange starts to look pretty good, compared to many modern drivers, which seem to have more complicated breakup modes - or am I missing something:confused: Cause the SB15CAC seem to have both a broader and almost twice as big a breakup, compared to mine :confused:
 
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Y

YSDR

Member
Joined 2013
digitalthor said:
View attachment 844925


My Accuton midrange starts to look pretty good, compared to many modern drivers, which seem to have more complicated breakup modes - or am I missing something:confused: Cause the SB15CAC seem to have both a broader and almost twice as big a breakup, compared to mine :confused:
Click to expand...

In the case of your Accuton driver the breakup starts below 5kHz, which is very low in frequency compared to newer hard cone drivers. So the breakup induced bad order (3rd, 5th..) harmonic distortions are in the middle of the main frequency range of the driver and if those harmonic distortions are not reduced somehow, they can be audible.

Maybe the SB metal drivers have broader breakup, but occurs higher in frequency (which is good because of the crossover attenuation and so) plus the induced harmonic distortions are greatly reduced thanks to the ribs and other features.

Anyway, the magnitude of the SB metal breakups are almost friendly, compared to SEAS metal cone breakups.
 
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digitalthor

Member
Joined 2018
YSDR said:
In the case of your Accuton driver the breakup starts below 5kHz, which is very low in frequency compared to newer hard cone drivers. So the breakup induced bad order (3rd, 5th..) harmonic distortions are in the middle of the main frequency range of the driver and if those harmonic distortions are not reduced somehow, they can be audible.

Maybe the SB metal drivers have broader breakup, but occurs higher in frequency (which is good because of the crossover attenuation and so) plus the induced harmonic distortions are greatly reduced thanks to the ribs and other features.

Anyway, the magnitude of the SB metal breakups are almost friendly, compared to SEAS metal cone breakups.
Click to expand...


Good point :)
They just both look like around 10dB breakup.... so magnitude is about the same - just higher in frequency - which I can surely see as a benefit - even though I can dampen the breakup easily with my DSP. A breakup at 8Khz makes a 3-IMD at 2666hz, which is above my intented xover - which is nice.
I also read that even though you dampen a breakup - it's stille there - it still rings - just less - and maybe not audible :cool:
 
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