Home » Sponsored » Pi Speakers » B&C DE 250 and compensation
B&C DE 250 and compensation [message #53385] |
Tue, 07 April 2009 14:06 ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Russellc
Messages: 397 Registered: May 2009
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Illuminati (1st Degree) |
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Wayne, I've been using my B&C DE 250 DRivers, both on 290H and the JBL wave guide, and am finding the driver to have WAY to much volume, or whatever that causes a real in your face/pierce the head type of sound. Breakin and reversing the phase of the HF hookup helped some. My setup isnt bass or mids shy, JBL 4507 with either 2225H or 2235H 15 inch drivers. I noticed that the series and shunt resistor in your 4 PI crossover for the DE 250 are basically the same as I am using in the E'wave crossover, 30 and 15 ohms. ( 30 is series, 15 is shunt) With an L-pad, I must turn it down to the 10 oclock position or quieter to balance this driver with the woofer, which is 94 db for the 2235H and 97 db for 2225H. I notice that the 4 PI does not use an L-pad, and I have read and understand the reasoning behind that decision, but it seems like that driver should be SCREAMING at that setting, or perhaps your 4 PI crossover is less quieting to the LF band? The drivers otherwise show tremendous potential and I sure would like to harness some of that!Thanks for any explanation you can give, Russellc
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Re: B&C DE 250 and compensation [message #53386 is a reply to message #53385] |
Tue, 07 April 2009 17:11 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
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Wayne Parham
Messages: 18748 Registered: January 2001
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Illuminati (33rd Degree) |
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Remember that the Econowave crossover used on the AK site is a derivative of my π crossover. It's basically the same as what I'd use for an 8dB network, combined with an L-Pad for variable tweeter output. The L-Pad changes the scale of the R1/R2 values some, because its impedance combines with the fixed resistors. But the proportions are the same and when you analyze the Ewave crossover, you find its transfer function is nearly identical to a π crossover with 8dB tweeter circuit, with the L-Pad to provide additional variable attenuation.
The adjustable L-Pad gives the user some wiggle room, but it also means that only 8dB of HF augmentation can be provided. The AK/Econowave network was optimized specifically for the Selenium driver which has some breakup in the top octave, giving it some boost up there. If a full 6dB/octave EQ were given above 4kHz, there would be 12dB emphasis by 16kHz, and the Selenium driver would be too hot in the top octave. But the other side is that when a driver is used that doesn't have this kind of response, the top octave isn't given enough energy, and you lose some of the sparkle. Some drivers need a full 6dB/octave augmentation, which is what you would expect from mass rolloff. Without it, they'll be sort of shouty sounding. It's not as bad as no EQ at all, but it's about half of what you need. It's just not balanced EQ.
Most of my speakers use R1/R2 values of 16/16 or 25/16, which equates to 10dB or 12dB compensation, respectively. There are other values that can be used (see chart) but most of my speakers have combinations that require 10dB or 12dB compensation. The four π loudspeaker with JBL 2226 and DE250 uses a 12dB circuit, which provides nice smooth response. There is actually a slight on-axis drop in amplitude above crossover, but when you look at the total power response radiated at all directions in the pattern, it's a good match. Some angles have a slight rise in the crossover region, some a slight dip, with the average being as uniform power distribution as I have found in any speaker I've seen. It's a highly optimized crossover and is partly responsible for the speaker's good directional characteristics.
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Shouty highs [message #53387 is a reply to message #53386] |
Tue, 07 April 2009 18:26 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Champion
Messages: 40 Registered: May 2009
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Baron |
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Hi Wayne, This is probably a bit off topic - I am using the 3Pi with DE250 driver and found the midrange a bit thin and the high frequency a bit too shouty. Then I push them into the corner (about 1 feet away from the back wall) and toe them in at 45 deg. The system now has a much better tonal balance (actually quite nice!!!). However, my room is only ~10feet wide and I am sitting around 8 - 9 feet from them so the speaker axis actually cross in front of me by a large amount (probably 2-3 feet??). Is it an 'acceptable' placement? Or am I trying to hide a problem in the wrong way? Thanks.
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Speaker setup [message #53388 is a reply to message #53387] |
Tue, 07 April 2009 19:02 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
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Wayne Parham
Messages: 18748 Registered: January 2001
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Illuminati (33rd Degree) |
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You've set them up exactly the way I would.There are a lot of things that can cause a little (or a lot) of excessive sibilance. Of course, the speaker, it's tweeter and network are the obvious ones. The DE250 is a little hotter than the PSD2002, so sometimes people forget to change tweeter resistors when upgrading, which causes a bit too much treble. Other causes are lively rooms and source material, things like that. If you've stayed with the plans, used the right components, you can rule out the loudspeakers. They're properly matched. That leaves the room, setup and source material. In your case, I'd say you've found your answer. By having the speakers setup the way you have, you've reduced early reflections and improved imaging at the same time. This configuration works best in most cases, making the most natural sound.
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Re: Speaker setup [message #53389 is a reply to message #53388] |
Tue, 07 April 2009 19:14 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Champion
Messages: 40 Registered: May 2009
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Baron |
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Thanks Wayne, that sounds good. I have read your message a few times but I wasn't sure how much in front of the listener should the axis crossover (is it a few inches or 1 feet or 3-4 feet)? It is good to confirm with you that I am not doing something weird. I was impressed with the speaker at the beginning but got tired easily, but now it is much more comfortable to listen to. BTW, what are the correct resistor values? I got the crossover and the DE250 from you together last year and wonder if the resistor is already tweaked for the DE250? Many thanks!
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Re: Speaker setup [message #53391 is a reply to message #53389] |
Tue, 07 April 2009 20:52 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
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Wayne Parham
Messages: 18748 Registered: January 2001
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Illuminati (33rd Degree) |
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If you bought the crossovers from me, I would have asked what tweeter you were planning to use and populated the board with the appropriate parts. I'm pretty sure I would have put the right parts on the board, especially if you bought the drivers from me at the same time you bought the boards. I think I remember your order.
For PSD2002: R1a & R1c - 20Ω R1b & R1d - 30Ω R2a, R2b, R2c & R2d - 16Ω For DE250: R1a, R1b, R1c & R1d - 30Ω R2a & R2c - 12Ω R2b & R2d - 16Ω To be very honest, in a three π speaker with a DE250, the weak link isn't the tweeter, it's the woofer. Not knocking the Delta 12LF at all, it's a nice sounding woofer, very smooth, and some people prefer it. To me, the Delta 12LF sounds very rich and warm, but it doesn't have the upper midrange smoothness of the JBL 2226. When I take speakers to shows and listen to them non-stop for a whole weekend, I find the 2226 doesn't leave me fatigued at all. When I take a speaker with the Delta 12LF or Omega 15, they sound nice but I notice I'm fatigued after about a full day or two. The combination of a properly-designed shorting ring and a well-damped cone in the JBL 22xx woofers come together to make the midrange and upper mids very smooth. I haven't found any equals yet. Hence, the upgrade path I recommended yesterday.
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Re: Speaker setup [message #53400 is a reply to message #53391] |
Thu, 09 April 2009 00:50 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
Chris R.
Messages: 82 Registered: May 2009
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Viscount |
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You wrote: > When I take speakers to shows and listen to them non-stop for a > whole weekend, I find the 2226 doesn't leave me fatigued at all. > When I take a speaker with the Delta 12LF or Omega 15, they sound > nice but I notice I'm fatigued after about a full day or twoDo you notice the same thing with the 3-way design with the Omega? The "below ~300Hz" output is certainly there, but doesn't seem to have any character that would get annoying after a while. I really love my 3-way setup. Not exactly a 7Pi, but close.
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Re: Speaker setup [message #53403 is a reply to message #53402] |
Thu, 09 April 2009 10:28 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) |
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Wayne Parham
Messages: 18748 Registered: January 2001
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Illuminati (33rd Degree) |
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Actually, the cabinet volume is fine for the 2226, it's the Helmholtz frequency that's wrong. The three π and four π speakers are slightly different size, but either could be used as long as the port was right for the woofer chosen. So you would need to change the port if you changed the woofer.The problem is it's hard to resize a woofer hole and/or port and do a good job. You're limited on the tools you can use. So I understand your dilemma. Sorry, but I know of know drop-in replacement woofer you can use for an upgrade to your three π speaker. Might be worth looking at AE Speakers, to see if they have a woofer or can make one for this application. On first glance, the TD-12S specs look right.
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