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Old 13th March 2009, 05:10 PM   #1
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Default My System

Here is a picture of my main 2-channel system:


Click the image to open in full size.

The speakers are Lowther DX3's in MLTL's with FE206E's in 35 l BR's on top of them. The other pair are FE207E's in the same 35 l BR's, just different cosmetics. The tweets on top of the 207's are FT17H's.

The electronics are a 6BX7 p-p amp built by Jef Larson, a SI Super-T, a diyParadise Monica DAC, a Sound Blaster USB external modem and a Panasonic walkman. My "real" source is a laptop through the DAC's.

This is a basement room that is on grade on the right side.The room is 25'x15'x8' and the speakers are centered on the long wall. The front wall is cast concrete as is the floor. The right wall is all double pane glass. The other two walls are standard 2x4/dry wall. The ceiling is drywall on 2x10's.

The speakers are 8' apart and the listening chair is a high-back recliner 8' back. there is a sofa on the right angled at 30* and a futon on the left. The floor is carpeted.

With all of that background, here is an FR plot of the speakers:


Click the image to open in full size.

NOTE: There are no filters on the speaker. No BSC, no nothing. I do all on my EQ on the computer rather than passive at the speakers. The tweeters are not hooked up. I did sort of nomalize the plots in the midrange, as the DX3 is a couple of dB hotter than the two Fostex. The microphone is at my head position in the listening chair and the plots are ungated 24th octave smoothed.

Black=207
Red=206
Blue=DX3

I was pleasantly surprised at how well behaved the room is. Other than the peak at 40 and the dip at 60, things look pretty good. A bass trap is in order. The MLTL show a strong floor bounce, but the two BR's don,t(?). The rising response of the 206 and DX3 are clearly evident. One would expect a straight line decrease of something like 6dB/octave.

OK, so what does the tweeter do?

Click the image to open in full size.

This is the 207 BR with the FT17H. The FT17H is crossed in with only a cap.

Black=No tweet
Red=1uF
Blue=2uF
Green=3uF

I tried the FT7RP, but it didn't have enough oats.

Comments?

Bob
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Old 26th March 2009, 10:02 PM   #2
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Well, I like it cosmetically, for a start.

Hmm. The 1st FR plot is the kind of balance I tend to prefer for extended listening, rolling off in the highs. Bright systems just give me a headache. I'm with you on the digital Eq too -I'm increasingly wary of the passive circuits; they're just not precise enough, & I'm increasingly thinking they don't do the transient response any favours. At the very least, digital should allow for much finer / specific tailoring & adjustments.

Looks quite a nicely damped room anyway -the MLTLs look like they've got a similar narrow dip in the LF at about 45Hz[ish] that my last pair had -I've not quite figured where that comes from yet. Are the measurements taken for the speakers in the positions they're in in the picture, or were things swapped around a bit?

Interesting re the tweeter. Just to confirm, that's just a cap, no resistance or Eq applied?

Cheers
Scott
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Old 26th March 2009, 11:01 PM   #3
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From the charts the tweeter looks to me to be adding just the right amount of tweet. Many systems measured in Stereophile show much more pronounced high frequencies... possibly why so many hi end speakers sound spitty and fatiguing in an effort to sound detailed. Here we see using full range drivers we get the detail without the spitty hash.

Thanks for posting the measurements. I'd like to do that for my room and see what it shows.

Godzilla
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Old 26th March 2009, 11:03 PM   #4
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Quote:
The MLTL show a strong floor bounce, but the two BR's don,t(?).
Bob,

I am not sure that dip is entirely caused by floor bounce. I have calculated a null near that frequency with many of my ML TL models in the second half of my worksheets where the geometry of the box and of the room is included. However, when I remove the room effects sometimes the dip is reduced but not completely gone. I believe some of this dip is caused floor bounce while the rest is caused by destructive combination of the driver and port output which is a function of the distance between the two sources. If it was purely floor bounce, you should see a series of dips at regular frequency intervals.
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Old 26th March 2009, 11:24 PM   #5
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Looks good Bob... you have gotten pretty flat FR. Speaker sare nice.

The concrete floor and wall behind probably contributes to the bass extension.

dave
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Old 26th March 2009, 11:54 PM   #6
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Does moving the basket under the table alter the sound?

Just kidding.
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Old 27th March 2009, 01:35 AM   #7
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I'm having difficulty logging into diyaudio from sbcglobal. I can ony take a peek here at work.

Scott: No resistor, no EQ. I was surprised at how well the 206 works in a simple BR, but then, the Qts is way higher than published.

Martin: You are probably right about some combing between the driver and port. Your model assumes the port and driver are acoustically colocated and combined nearfield measurements won't see it.

Godzilla: Moving the basket does not have nearly the effect of adjusting the fake plant on the left.

Bob
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Old 27th March 2009, 01:57 AM   #8
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Quote:
Originally posted by Bob Brines
I'm having difficulty logging into diyaudio from sbcglobal. I can ony take a peek here at work.

Scott: No resistor, no EQ. I was surprised at how well the 206 works in a simple BR, but then, the Qts is way higher than published.

Martin: You are probably right about some combing between the driver and port. Your model assumes the port and driver are acoustically colocated and combined nearfield measurements won't see it.

Godzilla: Moving the basket does not have nearly the effect of adjusting the fake plant on the left.

Bob

So, would you say that the 206 does not need a tweeter while the 207 does? I was under the impression that the 206 needed a horn.
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Old 27th March 2009, 02:38 AM   #9
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Quote:
Originally posted by type



So, would you say that the 206 does not need a tweeter while the 207 does? I was under the impression that the 206 needed a horn.
It's not as simple as that. Un EQ'd, the 206 is shrill and abrasive. EQ it and it still needs a tweet. But then, that's what I hear. YMMV.

The 206 works better in a horn than the 207 and vis versa for BR's. All the plot above is saying is that the 206 does a pretty fair job in a 35 l BR. Have you noticed a subtle shift away from horns to BVR's?

Bob
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Old 27th March 2009, 03:21 AM   #10
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Do you normally listen to the 207e pictured with the tweeter or without? I was checking out your website and your FB-20 seems to be designed w/o the tweeter.
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