DCM TimePiece - A new project

[Blue Shadow]

Excellent technical discussion of the speaker. Here is some cosmetic evaluation. The cabinets, made from the same chipboard that the TF line is made. The secret to these speakers to have the smooth edges and a finished look is the use of the headliner material to wrap the speakers. You can see the leftovers all over the boxes on these speakers. The foam of the headliner material dies just a foam surrounds die and will need replacement. I believe that this material has some damping characteristics and helps eliminate diffraction.

The use of the chipboard, did they order that with less glue as it always seems to fall apart and pull off with the drivers mounted to the cabinet. We can continue to talk about the mechanical parts of the speakers and how inexpensive they might have been but the sound quality that is achieved from them is amazing. There was also some serious design coverups used to make their speakers presentable in the showroom. The headliner wrap under the grille cloth the solid wood or veneered end caps and such make them presentable. The sound is what sold them.

@-reverb- might want to get good info from this thread and build a pair of these. It doesn't seem that hard.

 

[dc270]

Good observations on the DCM, backing it up with measurements is a plus. Much like you I too am facinated how well DCM does so much with so little. Last summer I worked on a set of TW3's with blown tweeters. I was well fascinated with the design and looked into the TF 600's, 700's and even the 1000's. Again the drivers were some what minimal types- but they let the crossover design and cab design tell the honest truth about their sound potential. Incredibly well thought out!. Their work with diffraction & time/phase alignment is phenomenal They squeeze more out of a lemon than there is lemon!! Bass loading through a quasi 1/4 wave trans line-as they designed it, probably did call for the woofer with he QTS of one!. Seems they are stepping between two worlds of design theory! One thing you cannot argue-IT WORKS!
As for my TW3 project last summer I did fine that SEAS 4 ohm tweeter were a near perfect sonic replacement over the little Vifas. I just had to modify the tweeter bezels to fit the mounting wings. TW3's are an incredible speaker. When I gave them back to "Tomlinmgt", he liked them as well. While I really liked the TF 1000's, the TW3's blew me away yet more.
DC

 

[revox-b77]

I have never heard another speaker that does what the Time Windows/Frames can do. My wife refers to them as the "band in the barn".

 

[Donkey Karma]

Dc270. I also in the last couple of months dealt with a pair of 3's with dead tweeters.

In my case it was the leads from the crossovers BOTH having shorts.

The time alignment magic of Steve E is brilliance. Recapping was an epic battle. Found the build quality in the 3's a step up from the 1a's I was inside.

I have now been inspired to source an pair of TP's.

 

[baco99]

Quick update, I may have found a replacement woofer that will do what I need it to do in this box. The plan is to conduct some close mic measurements with an infinite baffle, then plug the original DCM and the replacement in the box and measure with an without the crossover. TSo, I should have three comparative measurements of this driver.

The driver in question is a real anomaly. I have done two speaker "clean outs" in the last 3 years. One was full of Morel gear with a few oddities, and the other was all AR/ Advent/ Jensen. I picked up one of these drivers in EACH of the cleanouts, 14 months apart, completely different owners and circumstances. The drivers are prototype AR 6" poly cone mid-bass made under contract by KSC industries, which by all accounts is no longer in business. The model # is FN165A3X10 and they are both date stamped 2003.10.13. So these drivers were made on the same day, as a customer order by AR, then over a span of 10-12 years were separated, only to then be reunited by me. WTF!?

They look to be of similar construction to the DCMs, so I measured them.

The specs are as follows:

Sensitivity: 87.2 dB
Re = 4.218 ohm
Fs = 63.93 Hz
Qts = .7699
Qes = 1.022
Qms = 3.116
Le = .2635
Vas = .4707 cu ft

As for anything I had "kicking around" they are the closest to being a match. The Fs is lower, but the Qts and Qes are within the theoretical range of working in this application. The Vas is double, and the sensitivity is 1.4 dB lower, but I'm going to measure them anyway. What's the worst that could happen!?

 

[-reverb-]

It's almost like they found YOU baco! Karma, anyone????

 

[baco99]

Here's an image and a schematic of the crossover. The woofer uses a simple 1st order choke with no attenuation. The tweeter is a 2nd order network with a 1.8ohm pad in front. What I can't quite determine is the circuit between the + of the tweeter of + of the woofer. It's not a notch filter. I think this is a "phase shifter", or a rudimentary time alignment/delay/advance circuit. Anyone have any ideas?

In essence tho, I shouldn't have to do much of anything to the crossover to swap these woofers.

 

[nexus]

the trouble with woofer substitutions is cabinet tuning. a simple acoustic suspension is possible to replace sometimes but the complex cab design Steve E. did will be adversely affected by any substitution.

you could swap the woofers and then seal the port turning it into an AS loading.

 

[dc270]

I am quest about that VAS being double, that is kinda critical thing you need in a 4th+ order design copy!
Have you looked around for something with near the same VAS and FS- get those two near to what the old drivers had and you should be doing much better..
DC

 

[Donkey Karma]

Brian, sorry the mid/woods I have are indeed Wharfedales, not DCM's.

Sorry. I will keep eyes out.

 

[KingBubba]

The tech knowledge in this thread is beyond me, but I am enjoying the discussion. Was there not also a companion to the TimePiece, the TimeBase that made the combo a satellite/subwoofer combination?

 

[baco99]

the trouble with woofer substitutions is cabinet tuning. a simple acoustic suspension is possible to replace sometimes but the complex cab design Steve E. did will be adversely affected by any substitution.

you could swap the woofers and then seal the port turning it into an AS loading.

That's what the mic measurements will be for, to determine if all these numbers and worry actually make a difference in the real world. Like I said, can't make this any worse than it is with one broken woofer.

 

[rvatfhunter]

I don't know what the measurements on the Timepiece are, but as a reference point (or replacement candidate), I took a DATS measurement of a woofer (160W1502) from a dcm cx27:

f(s)= 97.57 Hz
R(e)= 5.01 Ohms
Q(ms)= 7.605
Q(es)= 1.632
Q(ts)= 1.343
V(as)= 6.839 liters (0.2415 cubic feet)
L(e)= 0.7636 mH
SPL= 87.8 1W/1m
M(ms)= 10.55 grams
C(ms)= 0.252 mm/N
BL= 4.456

 

[baco99]

I don't know what the measurements on the Timepiece are, but as a reference point (or replacement candidate), I took a DATS measurement of a woofer (160W1502) from a dcm cx27:

f(s)= 97.57 Hz
R(e)= 5.01 Ohms
Q(ms)= 7.605
Q(es)= 1.632
Q(ts)= 1.343
V(as)= 6.839 liters (0.2415 cubic feet)
L(e)= 0.7636 mH
SPL= 87.8 1W/1m
M(ms)= 10.55 grams
C(ms)= 0.252 mm/N
BL= 4.456

Thanks!
I just realized I forgot to post the specs on the DCM woofer. I'll do that when I get back.

 

[baco99]

Re-covering with new headliner fabric.

Ugly as ever and ready for testing. This one has the OEM woofer installed.

 

[baco99]

Finally got the new mic up and running. Using REW v5 software with a Dayton UMM-6 USB calibrated mic. The room is "mildly" treated. In other words, it's not an anechoic chamber. The ambient noise level is around 26-30 dB. And there are room reflections. If I snap my fingers from 6 feet behind the mic, it will pick it up. BUT, it's a measurement and it tells us something.

What's interesting here is the bass, though the -3dB point is higher than expected, around 80 Hz, the bass rolls off very slightly, not like a traditionally ported enclosure. Also, note how smooth the midrange is from 300-6000 Hz, with only a small dip at the crossover point. Then the high end on these little mylar tweeters drops off quite a bit. I should have save the phase plot, but there's virtually no phase shift until you get to about 18kHz. That's one thing that makes DCM speakers sound so "natural."

Next, I'll re-assemble the other speaker with the replacement woofer and see what the results look like.

 

[baco99]

Well, here it is! Non conclusive, but compelling evidence that all those minor differences in T/S parameters don't mean much when it comes to actual measurable performance. Are there some differences? Yes there are. Are they significant? Not really, and both speakers sound remarkably exactly the same to my golden ears.

Some things to note:

1) Both speakers demonstrate the same type of gradual drop off below about 80 Hz and a slight bump around 65 Hz. The AR woofer seems to dip and bump a little less than the DCM one. Interesting.

2) Overall, the AR woofer seems to react better to this enclosure than the DCM one. The response from 100 Hz to 500Hz exhibits the same general dips and peaks +/- 3dB, but the AR woofer doesn't quite hit those extremes as much as the original. Interesting.

3) At the crossover point, the AR woofer does seem to interact with the tweeter differently. There's a more pronounced and wider dip at the crossover point than with the other speaker. I have to say, I can't really hear it, but it's there if you really hone in on the upper range of a piano or a harp. I don't find it distracting and in fact I actually like it more than the original. I think there's a phase anomaly happening at the crossover, but for some reason the phase feature on REW is not working today.

So, in essence, these AR woofers are a very suitable replacement for the originals. In fact, they may even exhibit more civilized behavior. Not sure what I will do with them when I am done

Hope you enjoyed the journey!

Full response of the AR woofer.

Bass response for the AR woofer

Bass response DCM woofer

Crossover with AR woofer

Crossover with DCM woofer.

 

[nexus]

glad it has worked out for you!

 

[baco99]

FYI, these speakers are being offered on Barter Town as an "Auction for AK" for anyone interested.

 

[Nakdoc]

We had a consigned pair of Time Pieces with the companion Time Base woofer towers a few years ago. While I never made measurements, (my home speakers are Time Windows) I would say the TP, operating by itself, had a pronounced mid bass hump, even when sitting on stands. Imaging was great. In combination with the Time Base, whose crossover is in series with the TP, the results were really fun! No mid bass hump! The bass response sounded like your graphs, only deeper. I would highly recommend the combination to anyone with any taste in music.