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Old 5th April 2005, 11:15 PM   #1
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Default Line array corner sub

Has anyone tried to build a line array corner subwoofer.

I know the point in making one would not be for increased sound directivity at the frequencies that it will operate in but it seems like a good way two get multiple drivers in an enclosure that would be relatively easy to place.

You could use like six or eight, eight inch drivers with more modest requirements. So they would be less expensive. Also, the floor comb filtering effect would be mitigated to some degree by having drivers placed at several distances from the floor. This could possibly help to some degree with room modes since the radiating area would be very large compared to a one speaker subwoofer.

Of course high SPL's would have less distortion and since more total air could be moved with each speaker using less motion it seems like the total transient response might be higher. If the drivers were critically damped the sound would be very good and very fast.

Feedback?

Hezz
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Old 6th April 2005, 01:41 AM   #2
mike.e is offline mike.e  New Zealand
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wavelengths ~8metres,driver spacing 0.3metres,no comb filtering.

1. Go to linearteam.dk
2. Download winisd pro
3. model up 8 of your favourite driver,consider the costs of each and box volume required vs buying one 12" high displacement woofer.

Cheers!
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Old 6th April 2005, 04:28 AM   #3
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Mike.e,

Thanks for the info. I have Winisd but not sure if it is the pro version. I've never tried to model a line array and this is area that I need to study up on. After having gone through some of the archives I have come up with a few ideas and I think I want to try and build this quazi line array hybrid. There seems to be good arguments both for using multiple small drivers in a sub and for not using them.

My goal is not high SPL's but high quality HT bass at moderate SPL's. That being the case I will try to get buy with good quality average x-max drivers with moderate amplification.

Although I see the possibility that multiple small drivers can have better definition in the higher bass range it seems impratical to expect them to get down in the 20 - 30 Hz range with any resonable output.

Also small bass drivers don't usually have a low enough Fz for really low tuning so I have hit upon this compromise hybrid system.

My room is not real large and I think that anything more than a good single 15 inch driver will overload the room. However, since it is always possible to turn down the volume I think a little more is better than not enough.

Here is a 3D mockup of my corner design. My idea is to use one 12 inch woofer in a Qts .7 tuned enclosure getting the lowest F3 that I can. The 12 inch will make up about half of the surface area of an equivalent 15 inch driver. I think that a good twelve inch driver with a strong motor assembly can have tighter base than a 15 inch due to stiffer and lighter cone. At least at a reasonable cost.

THe rest of the equivalent 15 inch surface area will be made up of three eight inch drivers vertically mounted above the 12 inch driver. These are the high transient response drivers and will each be mounted in a critically damped Qts .5 sealed enclosure. They are closer to ear level and my hope is that they will kind of fill in the slightly less defined bass that the 12 inch driver will output. The three 8 inch drivers will be 16 ohm if possible and be driven in parallel with one channel of a external stereo amp. The other channel will drive the 8 ohm 12 inch lower driver.

Hezz
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Old 6th April 2005, 07:02 AM   #4
hm is offline hm  Europe
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Default multispeaker bass

Hello,
you better take 1 or 2 6,5 " driver in a horn like
the free download SUBSEL.
Cheaper, faster, better control, in a corner more bass
than other constructions.
hm-moreart
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Old 6th April 2005, 07:53 AM   #5
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I think your idea seems good in principle to the layman, but the idea in theory and practice I think will actually be quite bad. Your stalling point is that you have a very narrow bandwidth for each set of drivers, and also a crossover between them. Crossovers are bad as they introduce phase and group delays.

Also it's a myth that smaller drivers are faster or have better transient response -- you will find that if you design your sub right with a single 12 inch it will be fine. Think of a how a big heavy Porsche can still stop, start handle better and go faster than a little shopping hatchback

Finally, you re trying to get fast bass and good transient response, then sticking the sub in a corner. You will make more difference than ANY sub design will ever make simply by placing the sub somewhere else in the room. Corner is the worst place to put a sub as it drives the most room modes and often sounds most uncontrolled -- totally negating all your effort in designing a good box.
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Old 6th April 2005, 08:33 AM   #6
hm is offline hm  Europe
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Default theorie und praxis

Hello,
if you use a sub above 100 Hz than it is no sub.
May be your experience ís no large, do you ever listen to a
Klipschhorn or something equal.
My experience shows that in this case it will be the best way.
If you want 120 dB you better take a Shearerhorn,
if it is for HomeHiFi below 100 dB, my solution are much better
than every 12" in BR, think about moving mass etc.
below 100 Hz there is sound, contour, transparens and so on,
with large drivers you can´t get that, only more SPL.
Look the ALPHORN 135L brutto down to 30 Hz, Klipsch owner
are completly floored by listen to it.
If you will take the bass over 200 Hz than better take the
HELIKON with a 10" driver.
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Old 6th April 2005, 09:26 AM   #7
Cyrus_s is offline Cyrus_s  United States
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Default Re: Line array corner sub

Quote:
Originally posted by Hezz
Has anyone tried to build a line array corner subwoofer.

I know the point in making one would not be for increased sound directivity at the frequencies that it will operate in but it seems like a good way two get multiple drivers in an enclosure that would be relatively easy to place.

You could use like six or eight, eight inch drivers with more modest requirements. So they would be less expensive. Also, the floor comb filtering effect would be mitigated to some degree by having drivers placed at several distances from the floor. This could possibly help to some degree with room modes since the radiating area would be very large compared to a one speaker subwoofer.

Of course high SPL's would have less distortion and since more total air could be moved with each speaker using less motion it seems like the total transient response might be higher. If the drivers were critically damped the sound would be very good and very fast.

Feedback?

Hezz

What type of budget are we talking here?

IMO For the cost of 6-8 8" drivers, one can get 2 15" drivers and mount them IB in a ceiling or wall for modest SPL. The Qts of the drivers becomes your system Qtc. Near transient perfect bass.

Also IMO it's easier making an ugly manifold/line array that is hidden and doesn't impose as its not in the room.. as opposed to a large box that one must finish to match something in room.

The downside is that you can't move your sub(s) around. Although its only drywall.
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Old 6th April 2005, 06:38 PM   #8
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Ok guys,

A few things. First is that I have no options for subwoofer placement except in a certain corner. The corner is the best place for bass reinforcement but perhaps not for sound quality. The best place for any sub is room dependent depending on room mode boundries.

Next, I don't need anything more than 100 - 102 SPL. Also this is an attempt to build a good sounding sub with low cost drivers. Target budget is 25 - 40 USD for 8 inch drivers and 80 - 140 USD for the twelve inch.

I already have a couple of Dayton 8 inch drivers so they could be used.

The folded horn is a nice idea but I don't think that I have room for that as the size requirement is very specific and this thing tucks behind an existing keyboard rack that is sitting angled in the corner.

Where low cost drivers are concerned I am quite certain that the 8 inch drivers will have better tansient capabilities than the larger ones. At least if they are will designed inexpensive speakers.

It's been a long time since I've heard some Klipshorns. The ones I heard had slow ponderous bass in large quantities. Maybe with newer drivers they are better.

There will be no crossovers used as the design relies on the natural mechanical and electrical properties of the drivers to help with what they do best. Both upper and lower sections get the entire HT bass effects channel information and are likely to be crossed over at about 80-100 Hz since the front speakers will be nearly full range.

This is kind of like mixing a fat bass sound with a more delineated and better imaged one on a mixing board to get a certain effect. Creative tonal blending if you will.

The plan is two use a Pro stereo two channel amp that has level adjustment so that the upper and lower sections can be balanced for best integration.

Hezz
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Old 6th April 2005, 06:55 PM   #9
tiroth is offline tiroth  United States
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Isn't this the worst of all worlds? With all drivers covering the same frequency range, the sound will certainly be no better than the worst driver in the bunch. The FR will also likely end up rather odd because the 8" and 12" drivers will have different F3 and sensitivity, which will likely lead to exagerated 60-100Hz and an even sharper rolloff for the subbass.
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Old 6th April 2005, 07:07 PM   #10
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Richie00boy,

While your Porche analogy sounds good remember that the Porche cannot be built to do what it does at the budget car price.

The resources that I have are woodworking tools, creativity, and some acoustic and audio knowledge and experience. THe money resource for this project is limited both for drivers and amplification.

This is an attempt to get high end bass tonal quality as the first priority in a non negotiable space requirement at a budget price.

Hezz
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