I have been sitting on a large stash of Scanspeak (12MU + 18WU) and RAAL (various) tweeters for close to 10 years now, with the intention of building a home theatre system.
Recently I have come across the Illuminator Centre http://www.troelsgravesen.dk/Illuminator-CENTER.htm Which is essentially what I want to build, but with a RAAL tweeter instead of a Scanspeak one.
Unfortunately I can't just change tweeters and be on my way since the shape of the RAAL in question https://www.raalribbon.com/products_flatfoil_140-15.htm
doesn't really lend itself to a straight swap out.
I could mount the RAAL tweeter horizontally but I fear what that might do to the response. I have a CNC so I could custom make something to mount it vertically.
If I am going to go to the trouble of deviating from the standard box is it worth my while adding more mids to the speaker? Bare in mind this is a centre speaker for home theatre where most of the content coming out of it will be dialog, and the RAAL have a fairly high sensitivity (95dB@1m/2.83v).
I use 2 of the 12MU's in each of my open baffle speakers, but they are open baffle not in a box. Why is it that most speakers only ever seem to have one mid driver?
Is there any reason I couldn't use 2 or even 4 mids (series / parallel) in the centre?
Recently I have come across the Illuminator Centre http://www.troelsgravesen.dk/Illuminator-CENTER.htm Which is essentially what I want to build, but with a RAAL tweeter instead of a Scanspeak one.
Unfortunately I can't just change tweeters and be on my way since the shape of the RAAL in question https://www.raalribbon.com/products_flatfoil_140-15.htm
doesn't really lend itself to a straight swap out.
I could mount the RAAL tweeter horizontally but I fear what that might do to the response. I have a CNC so I could custom make something to mount it vertically.
If I am going to go to the trouble of deviating from the standard box is it worth my while adding more mids to the speaker? Bare in mind this is a centre speaker for home theatre where most of the content coming out of it will be dialog, and the RAAL have a fairly high sensitivity (95dB@1m/2.83v).
I use 2 of the 12MU's in each of my open baffle speakers, but they are open baffle not in a box. Why is it that most speakers only ever seem to have one mid driver?
Is there any reason I couldn't use 2 or even 4 mids (series / parallel) in the centre?
Two words - Comb Filtering. Multiple drivers have to be very carefully considered with regard to spacing/crossover frequency if a radically uneven polar response is to be avoided. There will always be compromises that do not exist when compared with a single driver. What is the main reason for wanting to use two or four drivers?
Partially to try and make the drivers a little more even the 12MUs are only like 90dB, partially to bump up the volume in that range because it is a centre speaker. Forgot about comb filtering. So would you go with 2?, 3? or a single mid version of 4?
There is potential in number 4, after all the tweeter isn't round. I don't know that it will all simply go together but may be worth investigating.
I have 10 spare, but it might be worth considering if I should need them in other speakers.
I keep going back and forth what I am going to use in the surround sound speakers. I know I will use the RAAL 70-10's, but I am not sure if I want to cross over to 12MU's or 18WU's.
I woukd go with scenario 4 which should work very well, depending how far up you want to push the xover.
In fact, a centre channel shouldn't even be laying horizontally. It's only done to leave room for the screen in the typical configuration.
What do you think to the idea above of omitting the woofers? Just making it a tweeter / mid on top of each other. I could build the mid in a typical main configuration. It would make the cabinet narrower.
This is a little O.T. but why is it OK for a Home Theater system to be made up of many different speakers? I wouldn't even consider two different speakers for my stereo, so why is a mix of sometimes very different speakers OK for H.T?
For movies, certain audio channels only contain effects noises, bass, voice, so speaker distinctions are not that important if there are tonal disparities.
For multichannel music, it would be more of an issue.
On making a little 2-way center with the 12MU, it might work but maybe the 12MU doesn't do best going down so low. I don't know what frequencies they pump into center channels. If it's just voice, baritone fundamental is about 300hz, so you'd be exposing it to undertones thereof. Also, in the Seas Center design measurements, it looks like Troels is only running the mid from 1khz, so basically you'll be taxing the 12MU a lot more than its usual comfort zone. Hifi compass shows distortion measurements bottom out around 1khz.
The different speakers have different roles so it's probably fine, but I always run matching main five speakers or at minimum matching front 3 and 2 similar surrounds. I used 7 JBL lsr 6332's and it was pretty nice!
Mains and centre will comprise of the same drivers. Just looking for the best centre layout.
So would I be correct in assuming that you are saying that the centre needs to be able to play to 300Hz or below to be fully effective?