More to Know about Differences b/w Ascend Models

[Jay_WJ]

So impressed with my recent purchase of a pair of 170SE, I'm about to order more Ascend's to complete my 5.1 system. With three models offered, I realized there are many options and I came to have a few questions about differences between the models. I think perhaps only the designer may be able to answer my questions. Dave, can you, please? Your response will be of great help for my decision (and maybe for others') !

My questions are:

1) As for the difference b/w the 170SE and the 340SE, I understand the use of dual woofers in the 340SE gives it better dynamics/power handling. But what I don't understand is the use of a different tweeter (smaller neo magnet vs larger ferrite magnet motor structure) in each model. Were there any specific reasons for using different tweeters when designing each model? I acknowlege that tweeters with larger magnet structure are preferred to ones with neodymium magnets in higher-end designs. If this is the case for the 340SE, were there any measureable/audible benefits of using the ferrite magnet tweeter when you developed the 340SE? Or simply assumed the benefits at an initial design stage?

2) I think, by design, the strength of the HTM-200 would be better off-axis response at midrange thanks to its small midwoofers. And of course its weakness is limited bass extension. Do you think that the quality of sound reproduction of its bigger brothers (170SE and 340SE) is still better even at midrange and treble? Does the HTM use the same Seas tweeter as the 170SE? Or does it use the old 170 tweeter?

Best,

Jay

[Quinn]

1. The 170 cabinet volume is too small for the "regular" magnet of the SEAS' tweeter hence the need to engineer the compact version.

2. The 200 does not have the SEAS tweeter.

[Jay_WJ]

1. The 170 cabinet volume is too small for the "regular" magnet of the SEAS' tweeter hence the need to engineer the compact version.

That may be one of the reasons. But that's not convincing enough to me. The volume occupied by the ferrite magnet assembly vs the neo one is still not that big relative to the total inside volume of the cabinet. Many small bookshelf speakers use a tweeter with a ferrite magnet.

[curtis]

I believe it is magnet strength rather than size, allowing higher power handling.

[Quinn]

The other thing is Ascend engineered the new tweeter so it would fit the old 170 tweeter cut out so that they could keep upgrade costs to a minimium for 170 owners to upgrade to the SE.

[davef]

Hi Jay,

Happy Holidays! I would be happy to answer your quesitons and I am pleased that you have been enjoying the speakers!

1) As for the difference b/w the 170SE and the 340SE, I understand the use of dual woofers in the 340SE gives it better dynamics/power handling. But what I don't understand is the use of a different tweeter (smaller neo magnet vs larger ferrite magnet motor structure) in each model. Were there any specific reasons for using different tweeters when designing each model? I acknowlege that tweeters with larger magnet structure are preferred to ones with neodymium magnets in higher-end designs. If this is the case for the 340SE, were there any measureable/audible benefits of using the ferrite magnet tweeter when you developed the 340SE? Or simply assumed the benefits at an initial design stage?

There is really no performance advantage between a ferrite or neo magnet when used in a tweeter. Many of the finest tweeters use neo magnets... A Ferrite magnet is much larger and will provide better heat dissipation because of the larger surface area while the neo is inherently magnetically shielded, no need for a bucking magnet and can. Neodymium magnets are also very expensive and are less predictable (tolerance wise) than ferrite magnets which lead to higher production rejects during manufacturing.

It is important to know that the tweeters used in the 170 SE and 340 SE use the same diaphragms (dome + voice coil). The only difference is the magnet assembly and the faceplate.

We developed the neo tweeter for the 170SE because it was important to be able to offer a drop-in replacement of the original 170 tweeter (with minor crossover changes). In addition, the close proximity of the tweeter to the woofer necessitated using the small tweeter faceplate which could not be used with a fully shielded chambered ferrite magnet assembly. The actual cabinet cutout for the magnet would be larger than the tweeter faceplate

I went with the ferrite magnet assembly for the 340 SE because I could offer a larger chamber which further lowers the resonant frequency of the tweeter and allows for a lower crossover frequency. This is an important feature to reduce off-axis lobing for the center version of the 340 SE.

2) I think, by design, the strength of the HTM-200 would be better off-axis response at midrange thanks to its small midwoofers. And of course its weakness is limited bass extension. Do you think that the quality of sound reproduction of its bigger brothers (170SE and 340SE) is still better even at midrange and treble? Does the HTM use the same Seas tweeter as the 170SE? Or does it use the old 170 tweeter?

The HTM-200 has never really received the love that I feel it deserves. I don't know of any loudspeaker this size that can compete with it. The HTM-200 uses the same tweeter found in the "classic" CBM-170. It is an absolutely wonderful tweeter and was the model used for developing the new SE tweeter. Do the tweeters offer the same performance? No -- the SE tweeter has considerably less distortion at high volume levels below 3 kHz and offers greater HF extension. Tonally, they are very similar but after extensive comparisons I prefer the SE tweeter.

Since you have a trained ear and are looking for pure accuracy, I feel you should stick with the 170 SE.

Hope this helps!

[Jay_WJ]

Thank you so much, DAve! It is wonderful to hear actually from the designer of the speakers I buy! Your response is very helpful and sufficiently detailed. I appreciate it.

I think I'm going with the 340SE's for mains and the 170SE's for center and surrounds. I have a little concern, by the way. In my setup, the tweeters of the 340SE will be a bit above my ear level. I read somewhere that vertical off-axis performance of speakers of MTM 2-way design is more erratic than that of speakers of TM 2-way design. Is this true?

[bikeman]

I read somewhere that vertical off-axis performance of speakers of MTM 2-way design is more erratic than that of speakers of TM 2-way design. Is this true?

Jay, could you define what you mean by erratic?

Thanks,
David

[Jay_WJ]

Here:

http://www.birotechnology.com/articles/VSTWLA.html

[bikeman]

Here:
http://www.birotechnology.com/articles/VSTWLA.html

I don't question the validity of the article but it's more than a decade old. Any follow-up articles that address the issue?

David