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Post by jhelms on Jun 16, 2013 1:58:19 GMT
So I was sitting there listening to my trusty old Altec Lansing 251 PC speakers (cut down from 5.1 to 2.1). Bought two sets of these way back in the day - around 2003-2004. They are a very mellow - listen to all day sort of set. Rolled off treble above 15K makes it sound like you are listening to old tube gear and not harsh in any way. I actually have not found anything I like better after all these years for casual office listening as I have never felt fatigued with them. Long story short, a wild hair flew up my arse and I started thinking about a 5.25" neo sub I purchased awhile back sitting in the cabinet (tang band w5-1138sm). The stock altec's sub looked about 5.25". Hmmmm project on! Grabbed the set of 251's in the shop and tore them down, taking out the wimpy little stock sub. Had to do some cutting, drilling, add a gasket and fired her up. Whoa, cabinet flex and rattle... from a 5.25"? Yeah! Also massive port noise & whistle from a screen inside the port itself. This little sub is ridiculous! My hair was blowing back and forth from 2' away which would give anyone with a pulse a grin. After cleaning the screen out, polyfilling the box, adding internal bracing and sealing it all back up with gorilla glue, I am sitting here with the biggest s*it eating grin on my face. Bass has gone from rather muddy with what sounded like a 60-70hz peak, to tight, deep and clean (as can be from a project like this) 40hz rattles things on my shelves, again from a 5.25"!!! Very pleased with the results of this blind swap out. Zero calculation or measurements taken other than being able to A/B with the stock sub I still have. Response and musicality is on another level under 100hz. Makes me wonder what these little drivers could do in an enclosure designed specifically for them. What the 251's look like stock. I just do not use the surrounds or center. Funny looking 5.25" Tang Band neo subwoofer with massive surround. Little SOB is rated at 9.25mm Xmax - visually it makes you laugh when playing test tones. Looks like the little thing is going to pop out of the cabinet. Thank goodness the grill has clearance or the cone would knock it off. Driver usedComparing a stock 251 and the modified 251. With the grill on, the only thing you notice are the two mounting screws above the grill.
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solderdude
Administrator
measureutternutter
Posts: 4,882
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Post by solderdude on Jun 16, 2013 7:30:04 GMT
That is a nice subwoofer with a long stroke voice-coil. ( datasheet) Such a long voice-coil has the disadvantage of having crap efficiency (82dB/W/m) BUT for an active subwoofer this does not matter at all. The upside of a long voice-coil is it will remain linear with large excursions and thus have lower distortion. SPL, surface area and excursions are related. With the specified 80W max you can still reach a very respectable 100dB SPL (above 50Hz) When a port is used you could extend it a little lower and when placed in a corner or on the floor near a wall it may even do 105dB which is loud and enough for small and middle sized rooms when used as a sub below 200Hz Can't use it in a passive LS though because of it's efficiency..
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Post by jhelms on Jun 16, 2013 8:04:03 GMT
Thanks Frans, yes sir that is the one! The setup is active with sub level control which is why I decided it would be worth a shot to see how it would turn out. Supposedly the amplifier can produce 25wrms on the sub channel - just enough for low to mid volume (levels that are comphy listening to at a desk for long periods of time) And if I push it up a tad, she really does not do that bad loud. I originally picked up the sub to experiment with in my 93 mr2. But I ended up picking up a set of image dynamics 2ohm drivers for the car which worked beautifully (stock subs were 2ohm) The current small port is for sure not optimal and is tuned higher than I would like - if I get time, I will model the sub in this size enclosure with this port size and see what the result is. From playing test tones I assume stock tuning is around 55hz. As I said, for a drop in it is impressive but for sure not optimal. The little driver moves a lot of air and at high levels, port noise is evident but at normal volume it is clean. I guess with life it is the little things that put a smile on your face. For now - just enjoying the results! Always had a thing for long stroke subs with neo motors. I was lucky enough to own a pair of aurasound 1808's long ago. More bass than I could ever handle and more than the house could physically handle but made for some good fun splitting drywall seams
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Deleted
Deleted Member
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Post by Deleted on Jun 16, 2013 15:26:18 GMT
Wow, is that you being blown away literally in the avatar by the new fangle thing?
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Post by SpiritShadow on Dec 21, 2014 20:24:32 GMT
I was wondering if anyone had upgraded their 251, sounds like you did it successfully. I'm hoping to do the same. Parts Express wants 60 bucks for the speaker but it sounds like it's worth the money.
However I wonder if you could possibly elaborate a bit with regard to your "polyfilling the box" and "adding internal bracing." Can you describe what you did? It would sure help me to know what I might need to buy before I start. Thanks in advance.
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Post by jhelms on Dec 21, 2014 23:07:57 GMT
- I noticed I had removed the original photos from the server so I uploaded them again. - It is a bummer, that sub used to be about $30 before neo material mined it china went through the roof! - I actually have 3 sets of 251's run as 2.1 speakers in the house now as they do great and are dirt cheap (last set I bought for $20 locally) I have a set in the wifes office, one set in the bedroom hooked to the bedroom TV and another set in my sons room. 2 of the 3 are modded now. - For internal bracing, I cut small 90degree corner pieces our of .5 MDF and gorilla glued them inside the cabinet just so that it holds it together. The sub occasionally blows the grill off the front of the box but does not rattle. On the polyfill, the old general rule is 1 lb per cubic foot, but in this case there was not any measurements involved so I just stuffed the box, keeping as much as I could away from the amplifier board
When one can mod a set of these for less than $80 including the cost of the sub and speaker set, it is the bargain of the century for cheap FUN sound. No audiophile here... just FUN out of a tiny system.
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Post by SpiritShadow on Dec 22, 2014 4:12:32 GMT
Outstanding. Thank you very much for the photos as well, they do indeed help. I will order the sub-woofer and proceed as outlined, you've just saved me a lot of time fooling around and I'm MOST grateful for your insights.
The only place I'd differ with your comments on the 251's would be when you said "No audiophile here." Like you, I have several sets of 251's, including one installed on my boat (28ft cabin cruiser). Although lacking in decibels, the perceived audio quality is very good. They have nice clarity and body, I would call it "excellent" for certain material, especially acoustic guitar and piano jazz. I've had many complements on these speakers, including one in particular from a pretty distinguished pro audio guy who sets up studios. He was surprised when he learned what the systems were and what I'd paid for them ($35, $45 and $50 respectively). I'm a guitarist and I sometimes play my acoustic on the back deck when docked. Occasionally I play recordings of new compositions just to see how they come across. More than one person has wandered over to listen to me play, only to discover I was working on the engine or cleaning fish -- and they were hearing a recording.
I'm sure I could find louder, audiophile-grade speakers for lots more $$$, but being a cheap SOB I prefer to go with what works and what I can afford. I spent considerable time finding just the right sweet spots for each set of speakers (which took some doing) -- but once in place, the 251's fill the bill admirably.
I'm really looking forward to the sub upgrade. Will let you know how it goes.
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Post by jhelms on Dec 22, 2014 7:37:56 GMT
Enjoy the mod - glad someone else has found these little gems and will get to have some fun with them as well! They definitely are a super bargain especially with the simple mod.
Not sure if the magnet will fit as I never tried it, but there is a non neo version of the sub that costs 1/2 as much. May make the set even a better bargain. Part number is W5-1138SMF
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Post by SpiritShadow on Dec 22, 2014 21:29:58 GMT
Ordered the W5-1138SMF for $28 and a bag of polyfill & cleaned off my workbench. Should know soon...
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Post by jhelms on Dec 22, 2014 23:02:44 GMT
Right on - keep me posted!
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Post by SpiritShadow on Dec 25, 2014 16:56:57 GMT
Best wishes for a very Merry Christmas, hope you all have a wonderful holiday weekend.
The package from PE arrived in record time. The new Tang Band W5-1138SMF speaker alone weighs more than the entire Altec subwoofer assembly. Haven't taken it apart yet, we'll see what the weekend holds, should be an interesting project.
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Post by jhelms on Jan 6, 2015 15:03:48 GMT
Any updates? Did the big magnet fit at all?
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Post by jhelms on Jan 27, 2015 19:30:36 GMT
SpiritShadow - Ever get yours modded?
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