DCM Time Window 7 - AMP & PREAMP

I’ve Found out that I’m the owner of 1 of only 200 pairs of DCM TW7 speakers ever made.
I am running 2 Carver A500x amps in mono block mode into these speakers. The speakers are rated at 700W max into 4 ohm. The Carvers in Mono Mode are 800W.

My question is …does anyone else have these speakers and what kind of amp are you using, and what are your thoughts on the DCM Time Window 7?
And to the Tube AMP experts I ask, how many watts would be appropriate for these speakers? They are efficient at 92DB, but they're still power hungry.

I am thinking of introducing a Tube PreAmp into my system and take the Denon out…any suggestions for something under 1k?

My system:
Denon AVR 3300, Emotiva XDA-1, Rotel 991 AE, (2x) Carver A 500x, DCM Time Window 7.

I don't know what amp to recommend but, the Carver amps your running is being driven to hard, running them in bridged mode.

In stereo mode they can run 4 ohm speakers. In bridged mode, they can only go down to 8 ohms, and that is risky for the amp, and speakers. I looked on the web and found the speakers, and they state 4 ohms. You may be better off running just one amp in stereo mode for now. Those amps are probably running hot and hard now.

That 700 watt maximum for your speakers is most likely for a short term (fraction of a second) peaks. The 400 watts per channel one amp can put out is continuous, and may be more than those speakers can handle. Sometimes a bigger amp sounds better, but just a fraction of the power is normally used. A lower powered amp can sound better in some cases too. [http://www.dcmspeakers.com/manuals/TimeWindowSeven.pdf] [http://thecarversite.com/manuals/files-manuals/Carver%20A-500x%20owner%20manual.PDF]
I remember the Time Windows fondly. I heard the 1As and the later Time Frames, but never your rare TW7s. I remember TWs as being unusually transparent and balanced, getting panel speaker sound out of cones.

Anyway, I think they present a fairly challenging impedance load and you might be better off with a good conventional A/B solid state amp. In fact, since you have some Emotiva gear now, maybe a pair of UPA-1 monoblocks would be in order.

If you want to get a good match from same-era electronics, look for a Heathkit AA-1600. Then have a tech check it over and restore it to spec if needed. It probably won't need much work; they're very rugged. I recently picked one up for $239 and I'm astounded at how good it is. It has just the characteristics the TW's would need--reasonable speed, low distortion, wide bandwidth, high current and damping factor, good extension, transparency, and very stable into reactive loads.
Hifihvn, I did some testing. for starter the THX gain on the back is set to 50%. I turned off the MONO mode but still left the connection in bridge mode style (speakers connected to the positive posts only)...all its happening is the sounds level drops by about 5 clicks on the volume. Right now I've left the Mono button off and am going to listen to it like this for a while.

I dont know about pushing the Amps hard, but these speakers have a thermal light bulb fuse and I've had it kick in and cut off the highs. essentially these speakers are great for listening and running loud, but they are in no way shape or form a party speaker. That thermal protection kicks in llike a tax auditor and shuts it down. I've been thinking about switching over to Tube, but a 100wpc tube amp will set me back 2K at the absolute least for an entry level amp. I guess for now I have to find a tube preamp first.

Johnnyb53, I checked out those Heatkits...eh too vintage. I've been thinking about Emotiva's XPA1's, their Flagship monoblocks.
when I first put my system together I had full matching set, all Carver gear. my Pre and CD broke and had to return them. I've been foundling w/the idea of going all out and getting Full Emotiva set, but the curiosity of Tube sound is stopping me.
Dfgkali, I'm not familiar with the amp you have now. But, I did have a Carver TFM series amp that came out right before that one. It was also bridgeable. When I tried it in bridged mode, it was not as clean and transparent, as it was in stereo mode. It took a couple of tries, but the results always favored non-bridged. This seemed to happen with any other amp I tried bridging that had the option. I don't even bother trying the bridge mode anymore, due to the similar results I've received, no matter what brand amps. The sound does have to go through a lot more parts in bridged mode. My amp looked a lot like yours, but it was made when Bob Carver himself was still there. I don't know if any sound changes were made between the two.

The THX logo doesn't mean too much. They just want an amp to be able to provide enough power for movies. Any good potent amp can pass this. Amps like Krell and others don't bother getting it tested by THX, but I'm sure they would pass. Some cheap amps and a lot of receivers may fail THX standards.

Doubling the power of an amp only gives you about a 3 decibel increase in sound. That's not much. I think if you wanted to actually double the volume, you need about ten times the power (in watts). So in other words, just one amp may sound better, and still give enough power. I guess you'll find out, since you already have everything to compare it. I wish I could recommend you a tube amp that would work, or another solid state amp. I hope you come out happy.
Hifihvn, thank you for all the information you've provided. I understand your logic and make sense to me. I've for now left the amp in non bridge mode and am enjoying it the same. going through some more CD's.
My next smaller system will be all Tube, and by small I mean monitor speakers and possibly an integrated Tube amp vs. separates, but class A/B for sure. I will be introducing a Tube Pre. to this system sometimes this year.
I like..make that love these speakers, and wouldn't want to do anything to harm them.

Thank you again for the information.
Just to clarify something- a 3dBa increase in SPL (Sound Pressure Level) is double the loudness. dBa is a log scale so amplifier power must double in order to double the loudness of the speaker. It takes a just about a doubling of the loudness for our ears to perceive a change. It is important that speakers maintain a linear relationship of loudness output to power input. Overall average SPLs may not get that high when listening to music, but the peaks can require a lot of power and that is the advantage of having a high powered amp. It can generate those peaks to make the sound more realistic.
Take for example, a speaker with an efficiency rating of 89dB. That means it generates an 89dB SPL 1 meter away at 1kHz with 1 Watt input. Double the SPL, 92dB requires 2 Watts. Double again is 95dB and requires 4 Watts. 98dB, 8 Watts. 101dB, 16 Watts. You can see that since even loud listening levels are around 85dB average amplifier power needed is very low. The power is needed for the musical peaks. A bang on a bass drum, even a sharp clap can peak at over 105dB. The closer an amplifier can come to duplicating those real life high power peaks, the more realistic the sound is to us. But the other problem is that speakers start to become non-linear at some point around or above 110dB. Some speakers hit their maximum output there. It is hard to say, not many manufacturers publish maximum output or loudness vs. power curves.

There is a great thread on TW7's-- search for "Whatever happened to DCM's Steve Eberbach?" on the AVS forums. There is a guy there (Jamie Hauser) who not only owns a pair of 7s, he's probably one of the most knowledgable guys out there when it comes to sharing info about them (the only other person I'd consider more knowledgeable is the designer, Steve Eberbach, whom Jamie has talked to on numerous occasions regarding crossover design, rebuilding, etc).

Worth checking out.

-Russ in Napa
12-10-11: Dfgkali
Johnnyb53, I checked out those Heatkits...eh too vintage. I've been thinking about Emotiva's XPA1's, their Flagship monoblocks.
Did you specifically check out the AA-1600? There's not a lot to the styling: anodized black faceplate with removable handles. Still, it's an excellent neutral stable amp from the same era as your TW7's.

But the Emotivas are also a great value and should work well. And they're very cool looking with the blue light and all.
Here is a chart that may help.[http://www.sengpielaudio.com/calculator-levelchange.htm]
Wiki link.[http://en.wikipedia.org/wiki/Decibel]
Ooo..This is neat stuff.. Thanks :)
Ok, 3dB is double the Sound Intensity. It is still correct that it takes about a 3dB change in Intensity then, to perceive a change in sound level. 6-10dB which is double the loudness is a very big change. Think about normal conversation- it is 40-60 dB. Long term exposure to 85dB SPL will cause hearing damage. 100dB is standing next to a jack hammer. If someone must shout in order to be heard over your music, then it is very loud and likely approaching 75-80dB at the position where they are standing. Also consider that the sound Intensity then, drops 3dB every time the distance away from the speakers is doubled. So if sensitivity, for example, measures 92dB at one meter, then it drops to 89dB at 2 meters. And lastly, if each speaker is generating 92dB, I think the combined SPL is 95dB.
Okey all this is very good stuff...learning more than I had bargained for. So mg next question is : what is this DB rating that speakers come With. What am I being told that a speaker with 92 DB is better than a speaker with 87db?
What am I being told that a speaker with 92 DB is better than a speaker with 87db?

Not necessarily better, jut easier to drive to a volume level.

For example, a 87 db (at 1 watt, 1 meter) speaker can reach the volume you want with a 200 watt amp.

If you have a 90 db ( at 1 watt, 1 meter) speaker, it should reach that same volume level you want, needing only 100 (half) watts.

If you have a 93 db ( at 1 watt, 1 meter) speaker, it should
only need 50 watts to reach that same volume level again.

So, if these speakers were 100% identical in every way, including sound, looks, size, etc, I guess you could say the one with the higher rating can be better, since it needs less power, if everything else is equal. The all else being equal, usually doesn't happen. This just helps you find a speaker that can play louder for a given amount of power.

This Wikipedia link may help more. [http://en.wikipedia.org/wiki/Loudspeaker#Efficiency_vs._sensitivity]
Try the link again here.
I don't know the 7's but my brother got one of the earlier models which sounded very good with a Hafler amp. ...just guessing, I suspect that your speakers are better than the electronics you're driving them with. I was never fond of Carver's amps....
Thanks Hifihvn ...very cool and informative stuff :-)

Everyone have a Merry Christmas
Dfgkali--You know where to get a pair of these? I have a big DCM collection, and would love a pair of TW7'S!!!
DCMlover - how appropriate! you gotta send me a couple of pictures of the lineup.

How much would they be worth to you? I know 2 people who have a pair all 3 of us bought them together, I accidentally discovered them and everyone followed me.

Give me a number, I honestly don't know, I know I wouldn't sell my set for a penny less than a ridiculous amount! after all as you very well know there were only 200 pairs ever made and they're all paired with each other.

email me a picture/Direct to
I don't really know how much I would pay! I guess it depends on where you are located. I am pretty sure that if had a ridiculous amount, my wife would kill me for spending it on speakers!
I have a pair of TW7's that I bought from Steve at the CES show in las vegas. Were were new DCM dealers at the time. I have the matching center AND two pairs of OW7 Dipole surrounds to go with them.
Any updates on this thread?
I've absolutely loved my TW3's with a Sansui AU-719. It was supposed to be my "backup" system while my all-tube system was being worked on. Now I listen to the DCM almost exclusively.

Anyway, if someone in the SF Bay Area has Time Window 7's, I'd love to just listen to them someday. PM me; I'll bring beer and good records or something, hah.
Bought my DCM Time Window 7s on a 40% off whim when Incredible Universe went out of business in about 1996. I've kept them thru Yamaha to Rotel to Classe electronics(CP800, CA2300)and they just keep sounding better. Full range response, tight bass, super clear, with tons of space between and around the individual instruments and vocals.

After 18 years with these beauties I'm getting the itch to change. Thinking about a side-by-side with some B&W 802s and Wilson Sophia 3s at the local high end shop. 5x the $, so it'll be very interesting to do the blind test.

Anyone done a similar comparison?
Great thread - I've owned my TW7's since new many years ago. Currently using them with a 12 watt Unison Research SET amp and love them... I'm sure there may be better out there, but the pairing with the tube gear is sublime.