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Discontinued commercial speaker fun... DCM TP160S

edited October 10 in Related
So as I mentioned elsewhere, I will be bringing a pair of commercial speakers to the IowaDIY shindig. I unboxed them last night (holy shit that shipped fast - 2-day shipping on a nearly 30# package, all-in for less than $80) and was generally impressed with their overall build quality. 

View from the front:

The drivers use typical cutout sizes - a true 6.5" on the woofer and a true 104mm on the tweeter. Pictures elsewhere show the tweeter to have a real motor - it isn't a typical $4 neo dome glued to a big faceplate. The woofer has a fake phase plug, but the woven cone is quite attractive If yellow is your thing), and the surround has a high-end look to it. It isn't your basic 1/2 roll, it actually has that "taper to the cone" look to it, reminiscent of the geometry used on, say, an Usher - if that makes sense. Overall, it is not a bad looking speaker out of the box, but the tweeter does look cheap.

From the back:

Port is undersized, but the binding posts are decent enough. Advertised as "45 to 20kHz". Otherwise, nothing else to note. 

So set my mic up, and took some squigglies. 

First up is the on-axis with and without the grill:

Care to guess which measurement includes the grill? Give up? The red. The red sweep used the grill. Seeing the lofting top end leads me to believe the claims of a copper cap in the tweeter are true. Otherwise, it appears minimal baffle step was used in the crossover, although top end energy is overall reduced with the grill in place - but the resulting emphasis at 1K and the peakiness in the 6-15k region may result in considerable overall coloration. The response is fairly smooth with the grill off, however. This is the only measurement I took with the grill on. If someone set these around some boundary reinforcement, toed them in, they would likely be pretty acceptable. Out on a stand, in a reasonably well set up listening space they would be shrieking harpies. 

Here is a distortion measurement, SPL accurate at 1M:

Largely second order dominant, with a rise in 3rd order in the 500 to 3k range typical of bread and butter woofers. These play very, very loud. At these levels, I generally have ear plugs in. Port chuff was a serious issue at this level, and likely to be noticeable on louder than average listening. In all honesty, I have measured DIY designs of my own using woofers that cost close to what this assembled pair cost that have worse distortion. 

Here are the horizontals out to `45 degrees:

Read into that what you will, but at no point do I see anything surprising, other than the blue curve (approximately 22.5 degrees out) might be the best bet for listening axis. There is a weird suckout there that fills in as you go further off axis. I should have averaged these curves out, but I didn't. So lay off me, guys, this is a damn hobby. I shudder to think what the grill did to the off-axis. The grills do look nice, however. 

I digress.

I took a single point about +30 degree in the vertical, to see if the crossover point jumped out. It did.

Looks like a basic 4th LR around 3200, but without extensive reverse engineering the design I can't say with any certainty what the slopes are. It just looks that way, that's all. 

Oh, and an impedance overlay:

Above the crossover point, you can see some more evidence that they are not full of shit on their claims about copper in the tweeter motor. Pretty well flat out to there ---------------------------->

Impedance alone:

Looks under-tuned at around 40Hz, if you subscribe to the 0 degree philosophy of determining box tuning. 

All in all, if a guy wanted to stick these in a corner they should perform pretty well. I'm not the guy to stick baby in the corner, so I hope to have an all new crossover for these. Maybe tomorrow I will pull the drivers, and get individual measurements, copy the stock crossover network, figure out the predicted bass response, and work up an improved crossover. Take some pictures of the internals, etc. Typical "kill 1/2 a bottle of pre-tariff single malt" stuff. 

Or, if someone wanted to just use a basic three band EQ and dial down the mid and treble band a few db, they would probably satisfy most normal people out on stands. These are a pretty good fucking value at the $80 clearance price, to be honest. At the original $300 or whatever, not so sure - that is an increasingly competitive slot to be in. 

I doubt I'll do any listening to the stock crossover, I've been doing this for a very long time and can basically hear them in my goddam head already, so I'll mock up a new crossover instead. 

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  • The grill really added a crapload of diffraction.
    Don, Donno, or "Hey you" all work for me, But never "Mr Johnson"
  • They are pretty and anyone that wants to step up from some fantastic 201's would be on a path of sonic nirvana.
  • Looking forward to more testing :)
  • OK, more testing.

    A couple pics of the drivers are in order... Start with the tweeter. Pretty bread and butter with the exception of the advertised copper cap being a real thing. 

    Short voice coil, vented aluminum former, no ferrofluid. Easy to take apart and re-assemble. 

    Looks cheap from the front, not a fan. Not a fan at all.

    There you see the copper cap and a wad of some kind of shit. I left it alone, put it back together. 

    However... if one is ok with the funny rotation/orientation the BeastMode DX25 drops right in:

    The 1" thick baffle is a nice touch, so there is that. Rest of the panels are about 1/2". No bracing, so that was a lie in the ad copy, unless they count glue blocks as bracing. 

    Woofer looks snazzy from the front:

    You can see the cool surround profile, and it is a stamped frame standard sized 6.5". The trim ring looks very nice until you get about 12" away, then it looks like plain old plastic. The fake phase plug is annoying, but otherwise a very decent looking driver at first blush.

    Side view:

    My cell phone photography skills are not always very good, but that is vented under the flat spider. I shined a small flash light through one of the vents, and spotted about 5-6mm of voice coil windings visible above the gap, as good an approximation of xmax as anything else I suppose. I could not bottom the driver out by manually flexing it, so the soft parts are doing their job. The frame is a cheap piece of shit other than being vented below spider and allowing the driver to hit Xmax without bottoming. I suspect a bumped backplate behind the bucker/cup. 

    Measured T/S parameters:

    Fs  = 66.12 Hz
    Re  = 3.03 ohms[dc]
    Le  = 83.43 uH
    L2  = 240.78 uH
    R2  = 7.59 ohms
    Qt  = 0.66
    Qes = 0.83
    Qms = 3.19
    Mms = 12.76 grams
    Rms = 1.661588 kg/s
    Cms = 0.000454 m/N
    Vas = 10.56 liters
    Sd= 128.68 cm^2
    Bl  = 4.408509 Tm
    ETA = 0.35 %
    Lp(2.83V/1m) = 91.82 dB

    Added Mass Method:
    Added mass = 25.00 grams
    Diameter= 12.80 cm

    Very sensitive, even for a 4 ohm driver. At least, somewhat more sensitive than many other drivers of this size. 

    Free-air impedance of woofer:

    Big ugly ~700Hz. Otherwise, not nearly as dramatic an impedance rise as some of the cheap shit I have looked at before. Indeed, LIMP says inductance is reasonably low. One for the 4 ohm design, I guess? Who knows. I'm less impressed with the inductance than I am with the huge ripple at 700Hz. Dammit.

    Now onto the stupidity of the design...

    Here is the driver modeled in the 12L, 40Hz box it came in:

    Should have sealed it, the F3 in 12L is around 75Hz that way. Perfect for integrating with a powered subwoofer. As it is, given the lack of BSC indicated in my measurements above and the anemic tuning, it is unlikely these will impress with their bass performance. Dumb design decisions. If these were my design, I would have gone sealed and thrown them over an 8" woofer. Or, tuned higher to take advantage of the ripple to offset the lack of full BSC to restore some oomph, like this:

    Or not. This driver just does not work vented in 12L, at all. The tower version of this 2-way looks to be about 30L, which is this:

    Boom. The plus side to the parameters of this woofer is that it exhibits great control below tuning. Here is the 30L excursion model:

    I bet in a tower configuration, you could really have some good times for very little money. The tower pair of these are about $150 right now. 

    The tweeter impedance:

    Here we have an otherwise nice looking plot almost ruined by a poorly utilized chamber. 900Hz FS. Makes me think I could redo the crossover much lower, but I suspect the addition of copper to this tweeter resulted in a rising response. You can see that in the excellent MCM Audio Select tweeters, a several db rise in the top octaves. Complicates things if you want to cross lower. As seen in the vertical off-axis snapshot I took, it is likely crossed at 3K in this design. 

    Now, I have a few thoughts on that. Since the woofer is very sensitive and is also capable of relatively quite a bit of throw and is anemic on the bottom end in this which will result in listeners cranking it to kind of restore that overall balance, crossing the tweeter at 3K instead of, say 1800-2000, could be a design decision intended to protect the tweeter at higher output levels. The excursion requirements at 95-100db are probably too great at 2K for the little guy. If we were to fully baffle step compensate this and eat up another 6db of woofer headroom as a result, we could possibly drive the crossover point several hundred hz lower, provided we take a few precautions, like a bare minimum of an L-Pad to flatten the rise at Fs. Cheaper to protect a cheap tweeter by crossing it high, though. Blah blah blah.

    So anyways, tomorrow I hope to grab individual in-box measurements and see what that scary 700Hz bump is all about. 

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  • I got a pair of these too. They sounded pretty good ( a great $80 deal!) and wasn't much impressed with the bass plus I felt so much vibration from these cabinets. So I got some dowels and braced the side walls with 3 of them. Much better, deeper, tighter bass. Doing the knock test, it just seemed like all the sound went right through the light, almost inch thick walls, so I took some non-drying clay and tried to coat as much of the walls (especially the front baffles) to reduce the vibrations as much as possible. (Newton's second law of motion.) I also coated the woofer basket and the metal cover surrounding the tweeter magnet. Now, these put out tons of bass! Much tighter - bass sounds like bass! The highs are more prominent - which given these tweeters - I'm not so crazy about. But I would super highly recommend bracing these puppies as much possible. It really does make these a MUCH better speaker. (I'm pretty sure dampening the cabinets reduces that 140hz hump  -which I pretty much heard before I worked on these.)
  • Excellent info @jr@mac

    Thanks for digging into these and sharing all the info. You don’t see this kind
    of effort on most forums. So to see it here is just awesome. Thanks and see you very soon!!
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  • I affirm the same Bryan.  Thanks JR. 
  • Bryan@MAC said:
    Excellent info @jr@mac

    Thanks for digging into these and sharing all the info. You don’t see this kind
    of effort on most forums. So to see it here is just awesome. Thanks and see you very soon!!

  • So, I rolled the dice and ordered some woofers from AliExpress to try:

    Uses a standard 165mm frame, and looks nice. I will do some more work on stock drivers, but if these measure up, should work much better. 

    I'll likely use the BeastMode tweeter, as well.
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  • That looks like a nice unit. 
  • It appears nice on paper, I'm looking forward to it 
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  • Is the new DA25 vintage looking enough? 
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  • That is the legendary Radio Shack 40-1011A poly woofer.

    I like it. The cabinet already has a "vintagy" look to it, this woofer and tweeter will only serve to compliment that. Recover the grills with some tweed and bam.
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  • Tweed grills - you could hang them on the wall in your "Rec Room"  like my dad did!
  • Home sick today, between sneezing fits I played with this some more. The drivers are not actually that bad - other than the woofer having altogether useless TS parameters for this enclosure. 

    Woofer distortion. It is SPL accurate to about 2/3 of a meter. 

    As you can see, it wasn't loud enough to stress it. At all. It also has a fairly smooth response considering the cabinet it is in.

    Here is the tweeter:

    This was pretty well bleeding ears territory and the tweeter took it like a champ. Crossing at 2K would be no problem, might even be able to push it a little lower but in this cabinet, the diffraction hump becomes problematic at the lower frequencies. It is likely a super flat response driver on a huge baffle. 

    Here are the raw drivers, gated, 1/24th octave smoothing:

    Easy enough to work with. I am generally impressed with the drivers, in fact the DCM woofer would make a fine upper midbass/lower midrange in something. Squish a cheap dome mid between this woofer and this tweeter, sealed, and add a couple 12" subs kind of thing. 

    Anyways, dicked around in Xsim a bit. Tried all my usual tricks, ended up with one stupid simple version (not tested yet, I also accidentally measured the woofer in reverse polarity, lay off - I'm sick and somewhat delirious):

    Here is the modeled response with that network:

    Modeled reverse null:

    Modeled impedance:

    As you can see, it would be a cheap crossover at a commercial level - no idea why the original designer did not come up with something similar. I will be pulling the factory crossover out and see what they did.

    If I find the energy, I will dig those values out of my bins and take some measurements. I am pretty run down, though. 

    Anyways, likely not going to use these drivers for anything else. I am waiting on the Aliexpress drivers to arrive, and will likely pair them (if they are worth a shit) with the BeastMode DX25. I might also work something up with the Radio Shack woofers pictured above. They look right at home in this kind of old fashioned looking box, dontcha think?
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  • Threw this crossover together today. Other than being really tepid on bass (until I shoved them against a wall), they are good enough. I ended up plugging the port, and that "naturalized" the bass (I guess?). They are now parked, waiting for the new woofers. 
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  • Are you done with being sick JR ?
  • Not quite, hopefully back to 75% tomorrow.
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