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Old 13th February 2003, 04:11 PM   #1
Oger is offline Oger  United States
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Default TB W3-871S project needs bass

I am working on a project using four W3-871S drivers in a sealed enclosure and need to add some bass. I am looking at the Peerless WF 210 or possibly the MCM 55-2185 (I can't find any specs for the MCM). Does anyone have any feedback for this kind of setup?
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Old 13th February 2003, 11:20 PM   #2
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I'm no expert, but I'll reply just to keep this thread in focus. I have a few of these drivers (871's) and I'm interested in most anything to do with them.

These are good as full range, have you considered bi-amping? Maybe with a sub using these: http://www.lambdacoustics.com/pricing.html That might eliminate the need to balance the bass driver's efficiency.

OTOH the Peerless WF 210 fits well with the frugalphile philosophy and might be appropriate for Bricolo's $150 project.

How are you going to arrange them? Four seems small for a line array, Dave (Planet 10) has suggested bi-pole to take advantage of push-push and (I think) eliminate baffle step compensation and lobing. How will 4 work?

There was this thread: Uber cheap, yet amazingly good.

And this one:is two full range drivers in one baffle a problem?

I'll bet if Halo were here, he'd suggest adding more information to get others involved. (even talking to yourself works for some) ;^)
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Old 14th February 2003, 04:25 AM   #3
Oger is offline Oger  United States
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Thanks for the reply. The initial thought behind using four drivers was simply to raise the sensitivity as much as possible and keep it at 8 ohms. I did not want to end up with a 16 driver line array so I opted for four (sort of a mini array). After listening to them for a while I was truly amazed with the midrange but felt the bass was seriously lacking. I admit I'm lost when it comes to baffle step so any advice is appreciated. I am open to any suggestions.
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Old 14th February 2003, 09:04 AM   #4
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Quote:
Originally posted by Oger
The initial thought behind using four drivers was simply to raise the sensitivity as much as possible and keep it at 8 ohms. I did not want to end up with a 16 driver line array so I opted for four (sort of a mini array). After listening to them for a while I was truly amazed with the midrange but felt the bass was seriously lacking. I admit I'm lost when it comes to baffle step so any advice is appreciated. I am open to any suggestions.
A mini-array might work -- people say good things about 4 of the 50 mm Bandor units in an array of 4, but the TB is almost twice as big -- i'd guess you would start getting comb filtering at about 7 k or so (you need something like 35mm driver spacing to hit 20k)

I have given quite a bit of thought to how to use 4 small drivers in a single box.

1/ build a bipolar MTM. If you can get a small enuff tweeter you might even get away with a 1st order XO at say 5 k (series would be interesting). The back speakers could just be run FR with no XO -- it wouldn't really need a tweeter (it also becomes convertable -- turn it around and you have 2 FRs.

1a/ A number of people have reported good results with 2 FRs running together so i wouldn't rule out trying just a bipolar MM

Rick Shultz hasn't stoppd playing and has come up with something specifically for the 871s. You could build a bipole of this to use up 4 TBs. Picture below

2/ inspired by the EPI minitower... an omnipolar tower... in this case a square prism, 22" high*, dimensions of 190 mm x 190 mm (all internal) with drivers mounted one on each face as close to the top as you can get them. Bottom is completely open and spaced off the floor. stuff evenly with 96 g of dacron wool. (this is using Rick Shultz's alphaTL scheme)

*(spaced off the floor with a stand they could hit 25-26" so provision for tilting them back might be suggested -- you could lift them up from the floor on a pole or something but you would loose coupling)

2A) if that is two squat you could build a pair of bibolar versions (same 22" -- but 134mm square) and stand one upside down (and rotated 90 degrees) to create the same effect but with a taller, skinner box. A 7" x 7" 4 ft high tower.
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File Type: jpg exolinear-871-tls.jpg (23.4 KB, 599 views)
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Old 14th February 2003, 10:40 AM   #5
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Oger,

Among other things, I built a pair of speakers using two 871ís per side. The top driver runs full range and the bottom has a coil and resistor on it.

http://www.bmeengine.com/tbspeaker/TB2.jpg

This combination sounds surprisingly good and does have certain benefits over any speakers I have heard that utilizes tweeters and mids.

That said, one of its short comings is that they really donít reproduce dynamics as well as I would like.

A person I correspond with on the web has built a pair much like mine, and also a pair that uses four drivers per side with no baffle step compensation.

He says the four driver speaker is exponentially better then the two driver setup and sounds better balanced overall. I plan to build a pair in the coming weeks.

For bass, I use a powered sub rolled of at 24db per octave at 100hz. This seems to match the TB speakers well and is very satisfying to listen to.

Branwell
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Old 14th February 2003, 05:18 PM   #6
Oger is offline Oger  United States
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Planet10,

Your ideas about an omnipolar tower are very intriguing. Do you have any more information about the EPI minitower?

What is the purpose of the open bottem?
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Old 14th February 2003, 06:26 PM   #7
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Quote:
Originally posted by Oger
Do you have any more information about the EPI minitower?
--
from EPI in the Early to mid '70s. All the drivers in the 2 big towers are still available today in improved form.

Tower 4 x 8" + 4 1" inverted domes something like 6' tall -- a set drivers on each face (sealed)
MiniTower 4 x 6.5" + 4 1" inverted domes something like 4.5' tall -- a set drivers on each face (sealed)
MictoTower a bipolar 2 x 5" Rola Full Ranges (TL/resonant pipe)
MictoTower II a fancied up MictoTower with the same 1" dome on the empty faces.

All square towers

--

The open bottom is the terminus of the TL.

dave
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Old 14th February 2003, 08:15 PM   #8
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You will still need something on the bottom with an XO no lower than 100Hz. Ideally some extended range woofers. Not subwoofers, but something good up to 1 kHz or so.

And one for each side. 8s or 10s.

On my single TB to woofer projects i'm going to use a pr of 4" RS40-1022s passively XOed with the 1 i won, and for the exotic one i have a vintage Ceramic Coral 8" FR/ExW. I'll have to do this XO active.

dave
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Old 14th February 2003, 09:29 PM   #9
Oger is offline Oger  United States
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Dave,

I was thinking about the Peerless WF 210 8" with a XO at around 300Hz. I'm trying to keep the total cost of drivers down and the WF 210 looked promising.
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Old 14th February 2003, 09:51 PM   #10
JoeBob is offline JoeBob  Canada
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I combined a W3-871S with a Stryke SA071 in my last project, I wanted to keep the woofer in the same price range as the tnag-band driver, and for the price the Stryke seemed like the best way to go ($10us when buying 8 or more of them, which I was). And the results are great (used in an open baffle, both W3-871S and SA071).
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