Film-Tech Forum ARCHIVE: Surround: coaxial or not?

This is topic Surround: coaxial or not? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=012213

Posted by Hans Van Meenen (Member # 10131) on 10-24-2017, 05:01 PM:

My QSC 1150 LCR replaced my hifi speakers some time ago in my living room / home theater, and that was a ver good decision.

Now I start to think about replacing some surrounds. I have Kef LS50 that I want to replace by cinema surround speakers, but I'm not sure if I should choose QSC 8200 or go for more expensive coaxial surrounds like QSC's SR-1290.

Output of either is more than enough, only interested in sound quality. Distance to MLP is arounf 10'. My guess is the 8200's are perfect, but just wondering what advantage coaxial speakers could give, I see them more and more, also at other brands, cfr JBL SCS-8.

Will coaxial be better for atmos ceiling mounting, with a shorter listening distance of approx. 8'?

Posted by Jay Wyatt (Member # 8768) on 10-24-2017, 07:21 PM:

As far as I understand coaxial speakers have all transducers operating at the same point/axis, so time alignment issues are mitigated. Additionally, you generally get symmetric dispersion patterns which make it a bit easier to 'point and shoot" in ceiling mount scenarios.

If you're a member you can lookup AES 9695 for some more info.

Posted by Steve Guttag (Member # 268) on 10-24-2017, 10:31 PM:

The best surrounds I've ever heard/measure were Altec 604s in Altec 620 cabinets. The 604 is a coax. I cannot speak to the QSC sonic quality but the coax speakers in the QSC lineup are supposed to be superior to their normal surround speakers and are geared towards Atmos with 4-Ohm impedances for better amplifier power transfer since it is typically just the one speaker per-channel in Atmos.

Posted by Marcel Birgelen (Member # 6801) on 10-25-2017, 01:31 AM:

A coaxial speaker in terms of design, is closer to an ideal point source than a "normal" speaker. The closer the distance to the speaker, the more effective such a design will be.

Creating a good coaxial speaker design isn't easy though, and many of the cheaper designs do have issues, where one driver can severely impact the other and therefore produce a less than ideal representation.

Like Steve mentioned, one of the more legendary coaxial speaker drivers is the Altec 604, but for surround speakers in a home cinema setup, they might be a bit too bulky, even if you put them in a slim cabinet.

Posted by Hans Van Meenen (Member # 10131) on 10-25-2017, 03:51 AM:

These Altec speakers are really too large. If anybody has experience with the QSC coaxial then I'd appreciate to hear your experience. Same about the JBL SCS8 which might be more popular.
I guess especially for atmos height speakers at home coaxial might be better.

Maybe a silly question: when I look at many pro coaxials, I don's see the tweeter.... am I missing something? It often looks like a regular woofer.

Posted by Steve Guttag (Member # 268) on 10-25-2017, 09:02 AM:

One "trick" some coaxials do is to use the cone of the woofer as an extension of the "horn" of the HF so you may not see a traditional horn. EAW on their CR-82i hid the horn behind the dome even. The dome of the cone, if you paid attention, was very "think" and acoustically transparent. Those worked out well.

For home Atmos, I'm thinking some of the better ceiling speakers may do the trick (like JBL Control Contractor series).

For my home theatre, I'm thinking strongly about using 604s for the stage channels and something akin to the JBL Control 1 for the side/rear surrounds. I've always liked them.

Posted by Hans Van Meenen (Member # 10131) on 10-25-2017, 09:59 AM: