Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

The semi-infinite-baffle coax three-way project
The semi-infinite-baffle coax three-way project
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 24th June 2019, 07:35 PM   #1
Tfive is offline Tfive  Germany
diyAudio Member
 
Tfive's Avatar
 
Join Date: Jun 2018
Location: Straubing
Default The semi-infinite-baffle coax three-way project

Hi guys and girls!

I'm in the planning phase of a 3way semi-infinite-baffle speaker project.

The mid/high speaker chassis is currently the only thing that is set in stone, it will be a Thiel SCS4 chassis (because I own a pair of them already and I believe in the advantages of coaxes). The woofer I have in mind is the Alcone AC 10 HE. I want to use active crossovers, of course involving my own software Pulseaudio Crossover Rack :: T5! DIY Audio Software & Hardware .

Below I attached the planned layout in my living room and two renderings if the first rough cad model I did.

Regarding the speaker enclosures: I want to use MDF, 32mm thick walls, internally damped by bitumen and small 4x4cm pieces of floor tiles. Lots of crossbracing of course. The top is shown the way I plan to glue the 8mm thick panels together. Then they will be smoothed out completely by planing and sanding them.
Internal volumes will be around 6L for the SCS4 (still have to measure actual TSPs) and the Aclone wants to have around 26L for a Q of 0.7 - of course having a Linkwitz Transform Filter at hands i might go smaller even (as smaller volumes can be made stiffer more easily).

Regarding the setup in the living room: This is the only way I do not get in conflict with the door. The room is quite small an "echoy". In order to get decent imaging I realized that doing away with the space behind the speakers would probably be the best solution. The wall behind the listener (behind the couch) will be damped as much as possible.

What do you guys think of such a setup, can it work? What height above the ground for the woofer would you recommend - as shown pretty hight or rather lower? I plan to cross the woofer around 100Hz.

Looking forward to your comments...
Attached Images
File Type: png SIB 12-5C front.png (12.4 KB, 418 views)
File Type: png SIB 12-5C side.png (8.6 KB, 420 views)
File Type: png room.png (58.1 KB, 420 views)
Attached Files
File Type: zip SIB 12-5C.stl.zip (38.9 KB, 3 views)

Last edited by Tfive; 7th July 2019 at 06:49 PM.
  Reply With Quote
Old 24th June 2019, 08:02 PM   #2
Tfive is offline Tfive  Germany
diyAudio Member
 
Tfive's Avatar
 
Join Date: Jun 2018
Location: Straubing
PS: Dimensions of the enclosure are roughly 80cm wide, 40cm deep and 130cm high with the center of the SCS4 around 110cm (my ear hight when sitting on the couch)
  Reply With Quote
Old 25th June 2019, 11:15 AM   #3
ewollowe is offline ewollowe  Australia
diyAudio Member
 
Join Date: May 2014
Location: Perth, Western Australia
I like your design. Reminds me of something ejjordan used to recommend for their diy enclosures, flat against the wall with an angled baffle for correct loading and toe in.

I would have thought you'd be good to put the woofer closer to the floor as you're crossing over quite low, you should get a bit more boost and less floor bounce if I'm right?

Interesting looking software too!
__________________
Irishman downunder
  Reply With Quote
Old 25th June 2019, 01:54 PM   #4
Colin is offline Colin  United Kingdom
diyAudio Member
 
Join Date: Aug 2003
Location: UK
With the right speakers, wall-mounting is a valid approach and gets rid of any need for BSC. You may need some kind of eq to cope with the corner position. Alternatively, we've found that aiming at a Q of 0.55 to 0.65 helps a lot with positioning near corners.

What is the crossover point between the SCS4 and the bass driver?
__________________
EJ Jordan Designs
www.ejjordan.co.uk
  Reply With Quote
Old 25th June 2019, 03:54 PM   #5
Tfive is offline Tfive  Germany
diyAudio Member
 
Tfive's Avatar
 
Join Date: Jun 2018
Location: Straubing
Quote:
Originally Posted by ewollowe View Post
I would have thought you'd be good to put the woofer closer to the floor as you're crossing over quite low, you should get a bit more boost and less floor bounce if I'm right?
I was thinking about the same reasons as you. Didn't do it as i thought it would look a little weird. But the longer I'm thinking about this topic, the more i like the idea, especially as then the two internal enclosures would be spaced apart vertically by quite a bit reducing vibration transfer. And I can use the floor wall as the bottom side of the woofer enclosure too, thus coupling it to the floor.

Quote:
Originally Posted by Colin View Post
With the right speakers, wall-mounting is a valid approach and gets rid of any need for BSC. You may need some kind of eq to cope with the corner position. Alternatively, we've found that aiming at a Q of 0.55 to 0.65 helps a lot with positioning near corners.

What is the crossover point between the SCS4 and the bass driver?
I haven't measured TSPs on the actual SCS4s I have. Running a simulation with the provided TSPs yields a -3dB point of 96 Hz in a 6L enclosure with Q of 0.7. Maybe I will use this slope together with a 12dB/oct Butterworth filter to form a 4th order Linkwitz-Riley filter as highpass for the SCS4.

Then I would use a 96Hz LR4 filter for the woofer.

The AC10HE has a simulated -3dB point of 60Hz in a closed box, which I want to extend down to around 30Hz by using a Linkwitz transform filter. Q on the low end slope then is adjustable.

So what kind of EQ are you referring to regarding the placement in the corner? And why is a Q of around 0.6 better, any references?

Any recommendations on a 10" or 12" woofer? The Alcone was chosen at least 30% for its matching looks to the SCS4. Another contender is the Dayton DA270-8, also a 10" aluminium cone. I attached a new rendering with the speakers now in the correct left/right placement and the woofer pretty close to the floor. Also note regarding looks: the color will be in the light gray regime, 1) to match the speakers and 2) because it will blend in more nicely with the relatively bright room colors. Might even consider plain white.
Attached Images
File Type: png SIB 12-5C front2.png (12.3 KB, 324 views)
  Reply With Quote
Old 25th June 2019, 04:39 PM   #6
kipman725 is offline kipman725  United Kingdom
diyAudio Member
 
kipman725's Avatar
 
Join Date: Jun 2007
Location: Warrington
Send a message via MSN to kipman725
If your ceilings are not very high you may want to take this even further and mount the speakers in the upper corners. That way your minimising power input for a given bass SPL and ensuring your first damaging room reflection for imaging is as the maximum possible distance.

I wouldn't worry too much about the bass frequency response of the different drive units as this is the most easily correctable characteristic with DSP. A Q=0.6, 0.7, 0.5 bass alignment is immaterial compared to the room response. What is more important is the maximum power input, piston size and excursion as these three parameters define the maximum output at a given frequency for a closed box.

The choice of bass driver depends a lot on the intended cross over frequency. Most metal cone drivers need to be crossed over quite low to avoid the under damped breakup which manifests as a big spike in the frequency response.

The bass driver should be positioned within 1/4 of a wavelength at the crossover frequency if your aiming for wide dispersion. This is a fun program for seeing how two sources affect dispersion:
Tolvan Data

*just saw your planning to crossover at 96Hz, I wouldn't recommend this as it severely reduces the total power handling of your speaker and increases distortion. I would have thought 400 Hz and up would be more appropriate.

Last edited by kipman725; 25th June 2019 at 04:42 PM.
  Reply With Quote
Old 25th June 2019, 06:46 PM   #7
Tfive is offline Tfive  Germany
diyAudio Member
 
Tfive's Avatar
 
Join Date: Jun 2018
Location: Straubing
What's the advantage of the top corner of the room vs the bottom corner?

Regarding the crossover frequency between woofer and midrange:
1. I want to handle the coax as much of the frequency range as possible for imaging reasons
2. The SCS4 is a quite capable speaker of it's own, it's used in full range shelf speakers and can handle quite some power.
3. I can space the woofer further away and have a more even baffle next to the coax
4. I'm not concerned about SPL at all. normal listening will probably not exceed 80dB, 90dB would probably to loud for my neighbours

Will look at the software you recommended once I get home today evening, thanks for that tip!
  Reply With Quote
Old 25th June 2019, 11:08 PM   #8
kipman725 is offline kipman725  United Kingdom
diyAudio Member
 
kipman725's Avatar
 
Join Date: Jun 2007
Location: Warrington
Send a message via MSN to kipman725
The upper corner is away from clutter on the floor. I was referring to the speaker only having to radiate into an 8th of a sphere. I have heard this arrangement before and it works quite well as the human ear is poor at recognising the vertical height of sources.

Higher SPL capacity will result in lower harmonic and intermodulation distortion at normal listening levels. I use a 15" mid bass which crosses to 4*4" midranges which are hornloaded at 500Hz and can't discern the crossover frequency with an on axis frequency response measurement.
  Reply With Quote
Old 26th June 2019, 10:02 AM   #9
wolf_teeth is offline wolf_teeth  United States
diyAudio Member
 
wolf_teeth's Avatar
 
Join Date: Mar 2006
Location: Indiana
I'm with kip- 300-500Hz will likely blend better, and reduce IMD on the mids.
Wolf
__________________
Photobucket picture pages: http://photobucket.com/Wolf-Speakers_and_more
Writeups/thoughts/blogs: http://techtalk.parts-express.com/blog.php?u=4102
  Reply With Quote
Old 26th June 2019, 02:55 PM   #10
Tfive is offline Tfive  Germany
diyAudio Member
 
Tfive's Avatar
 
Join Date: Jun 2018
Location: Straubing
crossing around 400Hz (Where 1/4 wavelength would be ~21cm) and placing the woofer in a corner somewhat contradict each other, am I missing something?
  Reply With Quote

Reply


The semi-infinite-baffle coax three-way projectHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Open Baffle vs Infinite Baffle. DrDyna Multi-Way 37 30th November 2017 09:20 AM
semi-Infinite baffle for Lowther DX45? audiocats Full Range 20 16th April 2014 03:14 AM
Semi-open/Infinite baffle speaker project harruharru Multi-Way 12 11th January 2013 09:55 PM
help w/ infinite baffle sub HIPCHECK Subwoofers 5 16th December 2005 12:19 AM
Infinite Baffle. Best bet if possible? Hybrid fourdoor Multi-Way 50 9th July 2004 08:52 PM


New To Site? Need Help?

All times are GMT. The time now is 11:16 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki