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 :p

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

[davef]

Hi Jay,


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?

You are most welcome!

Regarding your question, I believe what you are referring to regarding the vertical response of an MTM is lobing -- and this is actually an advantage of a vertically oriented MTM speaker (the reason why MTM are so popular) The erratic response you mention, which is designed to occur at a specific off-axis vertical angle, helps minimize the effects (reduce) floor and ceiling reflections for an overall more consistent polar response and greater detail on-axis by delivering a higher percentage of direct-sound to the listener. However, if you are already sitting in an off-axis position (rather than on-axis), there could be problems. It all depends what the vertical angle is...

Let me know how far back you will be from the speakers and how high above ear-level the tweeters will be. From this I can determine the angle. If you are within +/- 15 degrees (which is a large listening window) then no worries :)

Take care!

[Jay_WJ]

I'll sit 9 ft far from each speaker and the tweeter will be 13 inch above ear-level. According to my calculation, this will result in 6.9 degree off-axis, which is well within the +/-15 degree listening window you mentioned. So I don't need to be concerned. Right?

-- Jay

[curtis]

Looks good to me!! But I didn't check your math. :)

[Jay_WJ]

Dave,

Can I ask one last question if you're not bothered?

What is the electrical order of the crossover network for 170SE and 340SE, respectively? What are their crossover points?

- Jay

[curtis]

Dave,

Can I ask one last question if you're not bothered?

What is the electrical order of the crossover network for 170SE and 340SE, respectively? What are their crossover points?

- Jay
Dave has posted this in the past:



Crossover point (between woofer and tweeter) is not indicative of performance. Slope and Q, if understood, can indicate some level of performance (mostly driver integration and off-axis performance). A higher order crossover will generally provide better off-axis performance and higher power handling. The SE's use high order crossovers -- 4th order acoustic, variable slope filters.

I prefer not to publicly discuss info about our crossover networks. While there is no "magic formula" as GaryB stated, there are some "magic" techniques that I use and have refined over the past 20 years. Ever try asking Famous Amos for the recipe for his cookies

http://forum.ascendacoustics.com/showpost.php?p=19009&postcount=38

[Jay_WJ]

Understood. I know that information of crossover slope and frequency alone doesn't tell much about speaker performance. I was just curious how low crossover points were possible with SE tweeters to reduce lobing error and off-axis suck-out.

- Jay

[curtis]

As far as the center channel is concerned, my main seating position is about 10' from the speaker, and we sometimes sit as much as 4-5' from center and have no issues.

I would imagine that would translate pretty well for vertical off axis with the mains and critical listening, although it is not something that I have tested or felt the need to test.

Give the speakers a shot and if they don't work for you, then go with the 170's, and then you won't have to wonder any more. :) We have all been there on some kind of purchase or another.

[Jay_WJ]

Thanks for the information, Curtis.

[davef]

Hi Jay,

Sorry I missed these:


I'll sit 9 ft far from each speaker and the tweeter will be 13 inch above ear-level. According to my calculation, this will result in 6.9 degree off-axis, which is well within the +/-15 degree listening window you mentioned. So I don't need to be concerned. Right?

At 9 feet back and 13 inches above ear level, my calculations indicate an angle of 6.86 degrees. Absolutely nothing to be concerned with :) (BTW, your geometry was perfect)



What is the electrical order of the crossover network for 170SE and 340SE, respectively? What are their crossover points?

Please contact me privately. The electrical slopes used on our crossovers for the SE models are complex. They can be viewed as 4th order electrical on the woofers and 2nd order electrical on the tweeters (forming 4th order acoustic slopes) However, they are a bit more complex than this generalization.

[Jay_WJ]

Please contact me privately. The electrical slopes used on our crossovers for the SE models are complex. They can be viewed as 4th order electrical on the woofers and 2nd order electrical on the tweeters (forming 4th order acoustic slopes) However, they are a bit more complex than this generalization.
Thanks, Dave. No more question about this. I was just curious. Not a big deal.

Happy new year!