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Multi-Way Conventional loudspeakers with crossovers

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Old 5th September 2008, 02:33 AM   #11
the joz is offline the joz  Australia
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Quote:
Originally posted by Pikefish
If your heart is set on building the subwoofers into the same cabinet as your tweeter (a bad idea if you believe in doppler/intermodulation/whatever they call it now distortion, and non-geometric subwoofer placement) you don't have to put them both on the front, apart from the bonus visual impact.
The recoil of the two subs pushing the box the same way will cause the rest of your drivers to move also (unless its back is bolted to a concrete wall?), the amplitude of this can be significant compared to hf drivers, and people complain about the effects of this.
If you have one on the opposite side of the other, you have no recoil pushing the box, and if one of them has its rear pointed outwards you can 'minimise even-order distortion' caused by the drivers differing behaviour when cone is traveling outwards and when inwards. I'm doing this on my current project, results to come.
At subwoofer frequencies they're pretty much omnidirectional anyway so it'll perform about the same, just won't look symmetrical, unless you mount them on the left and right sides of the cabinet.
Yes I hear where you're coming from,but what can I say I have my ideas set in motion now I'll have to see it through till completion.

What scares me is that some how sometime in the future I'll have to get this past the bride one more time,that is when I do another set of something.

Anyhow a pic of my existing subs,please don't ask why I need more bass...
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File Type: jpg ekta grands002.jpg (84.1 KB, 293 views)
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Old 5th September 2008, 07:58 AM   #12
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Oh well, nothing wrong with that, I'd then go for the "brute force" approach when building the cabinet, using thick heavy stuff rather than well braced light wood, it'll decrease the recoil velocity, and my favourite, make them harder to steal. Got wheelchair access?

I see you've got a titled baffle there, lining up the relevant acoustic centres right? I think the symmetrical array setup lends itself well to this approach, would look quite forceful, the big sub appearing to loom over the room.
The subs you've got look pretty nice, what are they, 18? Do you block a number of ports depending on what you're listening to?
Do standing waves make parts of the projectior screen go blurry?
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Old 6th September 2008, 06:44 AM   #13
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They'll be built like the subs with 33mm walls and heavily baced.
I wanted to post some pics but they need resizing,I'll try again later.
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Old 6th September 2008, 02:54 PM   #14
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Quote:
Originally posted by LineSource
If you accept LR4 or B3 or B5 slopes after reading JohnK's Music and Design Xover articles, a 3 way WMTMW with say 15" Lambda TD15S, ScanSpeak 6.5" Revalator, and Seas T25001 Millenium can get 20-20K with excellent phase coherence. Use the speaker budget$ on 5 instead of 7 speakers.
I agree, a 3way WMTMW is plenty. We've been discussing a high output, high efficiency 3way on a thread on AVS for quite some time now. http://www.avsforum.com/avs-vb/showthread.php?t=1035126 The thread covers lots of details about the drivers, orientation, separate subwoofer vs fullrange, development of our new 6.5", etc.

We're actually putting together a system using a pair of the TD12S's along with the new 6.5" midrange we're designing, and the Fountek NeoPro5i. I'm not convinced you'd really need the second midrange either. The WTMW design will be fine for most cases. This one is designed to be used with a subwoofer, as it is small though. Only around 3cf sealed total volume. The benefit to this system is the high efficiency, the whole system coming in at around 95dB 1W/1m and being capable of upwards of 120dB continuous at all points from 60hz on up. The woofers cover up to 300-500hz, the midrange then up to 3KHz and the ribbon tweeter above there. As an ideal option I'd look at something like the RAAL ribbon to cover the top end, although the NeoPro5i can work quite well.

For a similar system to go fullrange you could take a pair of TD15H's in larger vented enclosures . A pair of TD15H's i tuned to about 18hz can literally get you close to 120dB at 18hz without exceeding excursion or thermal limits of the drivers. You'd look at about 15cf total, a tower 20" wide, 72" tall and about 24" deep. Add in a 10" diameter vent about 28" long and you'll keep your vent velocity and compression quite low. The TD15H are fully capable of covering the range up to 300-500hz as they are +/-3dB all the way up to about 2KHz with extremely low distortion. The 6.5" midrange will have about 4mm Xmax so it will have plenty of excursion to cover down to 300hz if necessary and will be extremely smooth well past the 3KHz xover point. Pick your favorite high end driver and you're all set. You have a system that can easily recreate concert levels in any home listening room you could ever put them in.

Evolution Acoustics does the WMTMW design in their MM3 speaker as well: http://www.evolutionacoustics.com/mmthree.html This uses a custom made woofer we do for them along with some other quite expensive drivers, with amazing results. The cabinet is also about 6ft tall of stacked 18mm baltic birch layers!

Anyway, point being that choosing better drivers for the range they need to cover can make a 3way system much better than a 4way system in many cases. Don't discount the simplification of the crossover either, as the crossover is going to make or break your system. A 3way is much easier to design than a 4way.

John
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Old 6th September 2008, 10:12 PM   #15
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Yes John thanks for the info.
I was toying with idea of using PHL drivers aswell,this still may come about for a three way.
Your right about a High efficiency combinations,they do have a certain appeal.


Anyhow some pics of my subs internals just to show my bracing...
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File Type: jpg th_bracesandfrontbiggerpic.jpg (4.0 KB, 203 views)
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Old 6th September 2008, 10:22 PM   #16
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Quote:
Originally posted by Pikefish
Oh well, nothing wrong with that, I'd then go for the "brute force" approach when building the cabinet, using thick heavy stuff rather than well braced light wood, it'll decrease the recoil velocity, and my favourite, make them harder to steal. Got wheelchair access?

I see you've got a titled baffle there, lining up the relevant acoustic centres right? I think the symmetrical array setup lends itself well to this approach, would look quite forceful, the big sub appearing to loom over the room.
The subs you've got look pretty nice, what are they, 18? Do you block a number of ports depending on what you're listening to?
Do standing waves make parts of the projectior screen go blurry?

As you alluded too the subs are heavily braced and yes the drivers are 18" units.
They are JBL 2245's they are in 255 litre boxes each
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File Type: jpg th_subandbracingnofront2.jpg (4.0 KB, 191 views)
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Old 8th September 2008, 03:01 PM   #17
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Quote:
Originally posted by the joz
Yes John thanks for the info.
I was toying with idea of using PHL drivers aswell,this still may come about for a three way.
Your right about a High efficiency combinations,they do have a certain appeal.
The PHL looked to be the best available option, although it still had a fairly significant dustcap breakup. Going with a phase plug is the simplest way to fix this issue.

Quote:
Originally posted by the joz
As you alluded too the subs are heavily braced and yes the drivers are 18" units.
They are JBL 2245's they are in 255 litre boxes each
Just for comparison sake, the JBL 2245 at it's 9.5mm Xmax will displace 2.46L. A single TD15H at Xmax will displace 2.38L. That being said, with a TD15H in your main speakers you could expect nearly identical output from the mains as you get from your subwoofers now.

John
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Old 9th September 2008, 04:03 AM   #18
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So many options,you guys are meant to make it easy..haha!
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Old 10th September 2008, 09:13 PM   #19
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Anyhow 4 x Peerless 830847s have been ordered for my project,will keep you guys informed.

Just waiting for delivery now.
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