Extremely difficult: Tweeter with best low-end performance...Please help!

[Jay_WJ]

I need to choose a tweeter for a 2-way standmount design. My goal is to build a high-end yet inexpensive satellite monitor that has lowest possible distortions. The woofer will be Usher 8945P 7". But it is difficult to choose a tweeter. The most important criterion for the choice is clean low-end performance because I'll use 1.5 kHz as an XO frequency for acoustic LR4. This will be achieved by electric 2nd or 3rd order on the tweeter, depending on the tweeter's natural slope.

The reason why the choice is difficulst is that there are multiple candidates! I cannot decide on one out of the following three:

1. Peerless HDS
2. Dayton RS28A-4
3. Seas 27TBFC/G (H1212)

I already checked with distortion measurements reported by John Krutke, Mark K, and Joe Rasmussen. My conclusion is that all these three are EQually excellent in their nonlinear distortions! The more I look at their measurement data, the more difficult to choose one! (Note: RS28As measured by John must have some problem since Mark K's more extensive measurement shows RS28s are as good as Seas and Peerless).

So, I have to consider other factors:

1. Peerless HDS tweeter

Pros: 1) Good off axis performance; 2) nice metal face plate

Cons: 1) Most costly out of three; 2) a 2dB dip at 6.5 kHz (not sure what kind of effect it'll have in real-world listening); 3) the low end starts to roll off from 2.5 kHz, which means a higher order XO will be needed to obtain good phase alignment with the midwoofer.

2. Dayton RS28A-4

Pros: 1) Elegant look of mesh grill and metal plate; 2) the low end runs flat to 1 kHz (easy to work with in my application)

Cons: 1) a wide 5 dB dip at top end (again I'm not sure what kind of effect it'll have in actual listening); 2) high frequency but mild breakup node (but I agree that it's not audible); 3) QC consistency problem reported (but I confirmed from Darren Kuzma that this problem was due to misspecified tooling and has been addressed after the first product batch); 4) 4 ohm load but it's alright in my application.

3. Seas 27TBFC/G

Pros: 1) Inexpensive; 2) no notable FR dip or bump

Cons: 1) Cheap look of polymer plate and Hexa grill; 2) peaky breakup node at 26.5 kHz (may not be audible)


That's all I can consider. But still can't decide!

Can anyone suggest other factors that can help me make a decision? Please help...

- Jay

[peter_m]

Originally posted by Jay_WJ


3. Seas 27TBFC/G

...breakup node at 26.5 kHz (may not be audible)...


- Jay

I would think you'd need dog or bat ears to hear that. Can anyone confirm this, I'm just the noob!

[Jay_WJ]

Originally posted by peter_m

I would think you'd need dog or bat ears to hear that. Can anyone confirm this, I'm just the noob!

Yes, I agree with you, although some people may say they have dog ears

[Jay_WJ]

Anyone has first-hand experience with one of these tweeters?

Anything to say about their sound characteristics that measurements cannot tell?

[Hartono]

try to choose the tweeter that don't need series resistance to pad down the volume. series resistor in tweeter degrade dynamic and sound quality audibly.

[Dave Bullet]

Peter,

Breakup modes show themselves further down the frequency spectrum. For the 27TBFCG - you can see the ultrasonic breakup appearing in Zaph's harmonic distortion 3rd order at 8.7KHz, then 5th order at approx 5.25KHz (= the approx 25KHz F1 breakup node)

Both F3 and F5 are significantly down in dB to not be heard over the signal so the breakup of the 27TBFCG should not be audible, although you could argue any harmonic distortion colours the sound.

Cheers,
David.

[tktran303]

I hate talking about first hand experience, because really it means very little.

It is the end product that matters, there are other confounding factors such as drivers, cabinet, crossover etc will influence the perceived treble quality.

Unless you experiment with the different 3 tweeters on the single woofer, and design 3 crossovers to match the basic parameters like FR/phase alignment, it is impossible to make valid comparisons.

I have the ZaphAudio L18RNX/P+27TBFC/G, and in THIS 2-way the treble quality is consistent with the measurements- so little extra colouration, there is very little to write home about it.

I always hear about airiness, shimmer, and floating treble, soo tangible, you-can-almost-touch-it treble when people talk about some great dome tweeters, and more commonly ribbon tweeter, and they argue that these tweeters are more realistics.

But I'd argue that these are distortion artifacts.
Ask yourself, when did you notice this kind of phenomena at a real-live (unamplified) concert?

Consistency wise, probably 27TBFC/G tweeters probably have the best low end performance. This is important if you don't have measurements gear that allows you to test for non-linear distortion performance.

[Jay_WJ]

Originally posted by Hartono
try to choose the tweeter that don't need series resistance to pad down the volume. series resistor in tweeter degrade dynamic and sound quality audibly.

Unfortunately, a series resistor is required in my design for any of these tweeters. BTW, I think people agree that a resistor is the least harmful component of a passive XO. An inductor is the worst. Am I wrong?

[tinitus]

Resistor padding often affects phase - its the worst, but impossible or very difficult to do a balanced system without

But if you cant beat them, join them - in other words, its possible to let the padding/phase(delay) work fore you, but its tricky

You could use this little 2" Jordan

http://www.ejjordan.co.uk/drivers/jxr6.html

Mounted in a very small chamber it might even almost roll off by itself

But then I would consider a bass like the 10" Seas CA26RE4X, or similar, preferably with good sensitivity

[Jay_WJ]

Originally posted by tinitus
Resistor padding often affects phase - its the worst, but impossible or very difficult to do a balanced system without

But if you cant beat them, join them - in other words, its possible to let the padding/phase(delay) work fore you, but its tricky

Various ways of resistor padding (a series resistor before the net, a series resistor after the net, two resistor L-pad before the driver, split resistors before and after the net, and so on) all change not only the level but also the FR shape of a tweeter in a unique manner, hence its phase response, too. But this effect on phase is subtle compared to the effect of change of inductor and capacitor values in the network. Moreover, this effect can be predicted by crossover simulation.