Driver suggestion for ESP Linkwitz Transform project

[stajo]

Hi there,

I'm getting curious of trying out Rod's Linkwitz Transform project, but unlike him, I think he used a 15" in a 60 litre box, I am thinking of putting multiple 8ish drivers in an "array" in each corner of my listening area. I am planning 4 drivers per corner, one by the floor, one by the ceiling and two on equal distance in between for odd-numbered mode cancellation. I will drive all 8 in sum signal mono and low pass around 100 Hz and the 4 drivers in each corner will share a long and narrow boxing. I might even try port holes between the drivers or slave elements but thats way ahead.

So, before I run and buy alot of test sample drivers, which might not turn so good out I wonder if this community as any suggestions of suitable 8ish drivers? In general the driver shall have a strong cone that dont produce flapping overtones have a god XMAX. He writes about that under Loudspeaker Driver Selection in the article.

Heres a link to Rod's project page Linkwitz Transform Subwoofer Equaliser and here is a text in that article on how to test if the driver is suitable: "A simple test for drivers is to apply a signal at 20Hz from a clean audio oscillator. Using an amp of about 100W or so, and with the driver mounted in an enclosure of no less than about 28 litres (1 cubic foot), increase the level until the amp starts to clip - this will be immediately audible! Just below the clipping level, listen carefully for any audible frequency that is not 20Hz (which itself is virtually inaudible). In particular, if you hear 40Hz or (more likely) 60Hz, the speaker is distorting, and generating harmonics. With a good driver, you should be able to see the cone rushing back and forth, but should only feel the air movement - no audible harmonics should be heard."

Suggestions of 8ish inch drivers to test, anyone?

 

[DPH]

In essence, a LT is a base boost/shaping filter, so the system must natively be able to *do* what you want it to. With arrays of 2x 4x8's and, assuming a modest room size, you shouldn't be hurting for displacement, but more is generally better here. Picking something with a decently linear motor is the next thing.

But, really, play around with the box design, *then* figure out if/how much of a transform you really need (and can afford power/displacement-wise).

 

[stajo]

Yea, I dont know yet how much transfoorm I will need. The space avaliable is around 20*30 cm and I have 230 to to the ceiling so that is around 138 litres minus the box material per 4 8inchers.

Any driver suggestions DPH?

 

[DPH]

At 8x, I'd be looking through all the various parts dealers (I'm not sure who's "cheap" for you in Sweden), and see if there's a buy out. Even Dayton's least expensive 8" woofer (from Parts Express) would work pretty well.

Can you pretty easily get automotive woofers, e.g Alpine or JBL? Usually they have cost and displacement on their sides. You're looking essentially at 1 cu ft/28 L per driver. Vented with low, low tuning + LT might also be workable!

 

[stajo]

I do have some connection on the swedish beyma and faital wholesaler that I can try

http://www.supersonic.se/category.html/8-hogtalarelement

 

[DPH]

The Faital 8RS250 looks decent. You'd definitely need to vent + LT though to get much bass. Would get pretty loud though. Both companies make lovely drivers, but 8"s for low frequency output, not so much.

 

[stajo]

Thanks. It seems like a low Fs and a low VAS is hard to find in one driver. What is the more important parameter if going for more LT and less venting, ie forcing the driver to play lower with brute force, ie amplifier power.

 

[bjorno]

Hi stajo,

for your design without Requirements other than 2.3 m Ceiling Height and 16 Drivers:

FWIW:

b

 

[stajo]

Hi stajo,

for your design without Requirements other than 2.3 m Ceiling Height and 16 Drivers:

FWIW:

b

Thank you Bjorno, impressive, I will study this extensive material, and a neat little driver you have found

I was almost giving up on 8's and was looking at 12", 2 per corner, one floor and one ceiling instead but this really opens up!

Maybe Ill give you som more room data also, and new box size measures, how about that?

PS. Jakan?

 

[bjorno]

Hi stajo,

Sorry for the delayed answer: Been recovering from 'Sick Bay', for a couple of Weeks.

Quote:
'Maybe Ill give you some more room data also, and new box size measures, how about that? '
Lets give it a try!. New input Data?

b

 

[Deafuser]

Infinite Baffle. More fun ;-)

 

[scottjoplin]

That's like a red rag to the IB/OB Police!

 

[stajo]

Lets give it a try!. New input Data?

Great, hope you feel better. Omw home from a swim. Btw got 12 of them drivers. Seems to work without overtones all the way to xmax in a closed 48 l box. I happened to hit that

Will post room data in short

 

[stajo]

Ok, did some control measures to an early drawing over my listening room. Where there is wall and windows I took an approximate medium. There is some openings to hallways and kitchen. 235 floor to ceiling. X marks my usual listening position. Where the speaker signs are I am planning 4 eight inch bass drivers, one by ceiling, one by floor and two inbetween with equal distance, ie some 70 cm between them. I also plan two drivers along the ceiling inbetween the ceiling corner drivers and same by the floor. 12 drivers total around that wall in symmetry.

If this concept works to some satisfaction i plan to do alike in the other dimension, but maybe without the midwall drivers. We will see, open to suggestions.

I will try to give each driver equal to around 50 litres each.

 

[bjorno]

Ok, did some control measures to an early drawing over my listening room. Where there is wall and windows I took an approximate medium. There is some openings to hallways and kitchen. 235 floor to ceiling. X marks my usual listening position. Where the speaker signs are I am planning 4 eight inch bass drivers, one by ceiling, one by floor and two inbetween with equal distance, ie some 70 cm between them. I also plan two drivers along the ceiling inbetween the ceiling corner drivers and same by the floor. 12 drivers total around that wall in symmetry.

If this concept works to some satisfaction i plan to do alike in the other dimension, but maybe without the midwall drivers. We will see, open to suggestions.

I will try to give each driver equal to around 50 litres each.

Hi stajo,

Sorry but 'Been very busy this week' but I haven't forgotten your 'thread'.
Since you posted a layout picture of your Room, I've struggling with low success to fit and Simulate 12 48 L boxes in your Room because of the Window and the Door on the narrow 3.66 m Wall.

I think you should Post a new Picture where all distance coordinates to the Driver centers can be found counted from a coordinate System at X=0,Y=0 and Z=0.

BTW, Do you know about this approach:

Double Bass Array (DBA) - The modern bass concept! - AVS Forum | Home Theater Discussions And Reviews

b

 

[stajo]

Thank you Bjorno. I will make a closer schetch of how my very hobbyist approach for mounting the drivers is thought for now. Alternatively I dig more in to the link you sent me since, as far as I understand, that is a mountingwise simpler solution, but gives the same(ish) effect. It just comes a DSP in the plot.

As you see on the room layout, "front and rear" wall, ie the shorter walls is not ideal for mounting big ztuff on since its windows for most of the wall. Thats why my plan was to decorate the corners with drivers. But I could well enough fit a good number of small subs to the side (long) walls, except then for door openings.

That is actually my extended plan. Just this DBA array thing uses the side walls as mirrors where I instead was planning drivers in the corner. This, among other sources, was my source of inspiration: The placement of a subwoofer by a funny guy I and probably you know

Now Im on my way to a concert so I'll refine stuff later on when theres time. Please evolve your thoughts around DBA, or other arrangements for that matter, if you feel like it.