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In Reply to: Re: Tubes with B&W speakers? posted by Corbett on September 19, 2001 at 21:59:01:
Hello again,
At the time the measurements had taken place, there were well over
a hundred hours on them, with both music and noise as sources.
Some may argue that is not nearly enough time, where the manufacturer claims only 15 hours would be necessary.
I did notice changes as the surrounds and spiders loosened up,
but none in the top end.
It is my understanding that the NT tweeters are a Nautilus derivative,
and certainly not the real thing.
I also heard the 805,4 and 3 share a common tweeter, as do the 802
and 801.
It is interesting that you find the DM series top end over-emphasized.
I went from the 603.2 to the nt7 and 9, and found them brighter.
You must believe me when I say that I really tried hard to like
the CDM`s, but that never happened.
M.F.
Follow Ups:
Let me get my $.02 in here. I have a pair of DM 602.2's and they are not particularly bright IF they are matched up with the right pieces. (NAD C350, Sony XA1ES CD player, 12 gauge cables, Paradigm X-30 crossover, and the "right" interconnects) The sonic "signature" is very smooth in the highs, so I doubt the presence of a 4-5 dB peak at 10 kHz. I tried adding 5 dB with a graphic equalizer at 8 kHz and it ruined the sound. I, too, suspect an artifact of the measurement technique.You said it was a "semi-anechoic" environment. Like what? Outdoors? Sound absorbing panels around the speaker? Please give more detail. Next, where was the microphone aimed, and how far from the speaker was it? Also, which model of B& K microphone? Actually, I'd like to know the capsule diameter and whether it was a parallel or random incidence model? (directfield or reverberent field)
Hello Bald Iggle,
The speaker in question is the CDM-7NT, nothing at all like the DM series. Infact, I find the top end smoother on the DM`s, but less
detailed.
I conducted the test outdoors on a quiet night. Since the objective
was to measure the tweeters behavior, the shockmounted microphone
(omnidirectional capsule) was directed 0 degree`s @ 1 metre, with
test sources 20DB spl above noise floor.
M.F.
Michael,Thank you. Sorry if I sounded pushy. I'm not all that fAfamiliar with the CDM series, but I do know that the intro of the Series 2 DM's caused a sales problem for B&W on both the CDM and 800 series. Not enough improvement (if any) for the extra $$. Also the DM tweeter is recessed in a short elliptical horn where the CDM's is sort of semi recessed. A peak at 10 kHz implies a reflection at 1/2 or 1.5 wavelengths, or about 16 mm or 48 mm. Just about the edge of the tweeter housing or the top edge of the cabinet. I wonder? It would be interesting to place a baffle of sound absorbing foam or felt just in front of the tweeter with a 1" aperture to fire through and then measure the on axis response with any edge reflections eliminated.
I do have a test report on the CDM-9NT from the June issue of Hi-Fi News. They show a 1 dB dip at 10 kHz, but a peak of about 2 dB at 15-16 kHz. I(nterestingly, they thought the overall balance was a bit thick and slow, and the highs lacked something. No mention of brightness.
I have found my DM602.2's to be a little bright for my taste which was cured by cable and interconnect selection. I use the NAD C350 and dropped my Arcam 7SE in favor of my older Sony XA1ES which with the proper interconnect was smoother and tamed the highs. Since the CDM's are considered brighter than my DM602's, I probably could not bring them to the tonality I want. Doesn't square at all with Hi-Fi News' review.
Hi Again,
During the time spent with the CDM-NT`s, several inmates responded
to my distress call with some interesting advice.
After a while, I just admitted that they were not for me, and rather
than tweak, I traded them in for some JMlab Cobalts and havent looked
back since.
A speaker, or any other component HAS to put a smile on your ears
from the get go.
M.F.
Hey Michael, I remember your earlier posts now. :-)I'm glad you enjoy your new speakers.
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