Hi,
I've been lurking here for a while, and know some of the members on different forums. This looks like a pretty friendly environment for DIY newbies, so I figured I'd sign up. I hope to learn a lot from the time I spend here.
Anyway, on to my questions. My system currently falls kinda into the hi-eff/SET paradigm. Here's a not-too-recent shot of the speakers:
Changes since the picture was taken: The upper baffle is upside down now and reversed, so the tweeter sits below and to the outside of the midrange. Also, there are a couple of layers of polyster batting on the top surface of the cabinet.
Details: The woofer is my old Adire HE12.1. So it's an Eminence Beta 12CX in a ~ 24x14x15 sealed cabinet. The midrange is an Audax PR170M0, and the tweeter is a Fostex FT17H. Crossovers - active LR4 at 80Hz to the sub (NHT1259 in a sealed cabinet), active LR4 at 500Hz between the woofer and the midrange. The XO between the midrange and the tweeter is passive - 12uF/8ohm zobel and a .20mH coil on the midrange, 2uF cap on the tweeter. Amps: A Gainclone (~ 25W or so) on the woofer, and a 3.5W SET on the mid+tweeter. The mid/tweeter efficiency should be around 95-96dB.
This has all been set up by ear (i.e. handwaving and guesswork) and running sims using Speaker Workshop on manufacturer-supplied FR/impedance plots. I've run some minimal measurements on the final speakers using an SPL meter, but nothing worth mentioning. I have the parts to build a microphone and preamp, and will get around to doing that some day. Yes, I know I should do that before asking for advice
Anyway, questions. The thing I've been dissatisfied with is the treble. I really like the sound of the midrange driver, but I've heard smoother treble in many speakers. Now I have a pair of Fountek JP-3.0 ribbon tweeters that I plan to try here. These should match the efficiency of the mid fairly well. I plan to start out with the same XO. I'll probably also start out by mounting the ribbons on the same baffle (assuming they fit), probably directly above the existing tweeters (remember that the baffle is flipped).
Does that sound reasonable? It will place the ribbon at ear height, which is important based on everything I've read. It will also place the ribbon almost beside the midrange driver - I'm not sure if that will be a problem or not. Should I put together a new baffle for this? If I do, what kind of mounting would be recommended as a starting point? Maybe put the mid above the ribbon, but lined up with it vertically? Should they be in the middle of the baffle or offset to a side?
Assuming I get my measurement jig set up, any advice on measuring the ribbon tweeter? I know I shouldn't send a low frequency to it, and should always keep a cap in series. I can run FR measurements on it that way, I guess, but wouldn't that affect impedance measurements? Also, about measurements in general - I don't have the luxury of mounting these on a stand in the middle of a field. Can I get useful results using Speaker Workshop with a microphone in my living room?
OK, that's all the questions in my mind at this point. I'll probably think of more as I go along. And once again, hello to everyone here.
Saurav
I've been lurking here for a while, and know some of the members on different forums. This looks like a pretty friendly environment for DIY newbies, so I figured I'd sign up. I hope to learn a lot from the time I spend here.
Anyway, on to my questions. My system currently falls kinda into the hi-eff/SET paradigm. Here's a not-too-recent shot of the speakers:
Changes since the picture was taken: The upper baffle is upside down now and reversed, so the tweeter sits below and to the outside of the midrange. Also, there are a couple of layers of polyster batting on the top surface of the cabinet.
Details: The woofer is my old Adire HE12.1. So it's an Eminence Beta 12CX in a ~ 24x14x15 sealed cabinet. The midrange is an Audax PR170M0, and the tweeter is a Fostex FT17H. Crossovers - active LR4 at 80Hz to the sub (NHT1259 in a sealed cabinet), active LR4 at 500Hz between the woofer and the midrange. The XO between the midrange and the tweeter is passive - 12uF/8ohm zobel and a .20mH coil on the midrange, 2uF cap on the tweeter. Amps: A Gainclone (~ 25W or so) on the woofer, and a 3.5W SET on the mid+tweeter. The mid/tweeter efficiency should be around 95-96dB.
This has all been set up by ear (i.e. handwaving and guesswork) and running sims using Speaker Workshop on manufacturer-supplied FR/impedance plots. I've run some minimal measurements on the final speakers using an SPL meter, but nothing worth mentioning. I have the parts to build a microphone and preamp, and will get around to doing that some day. Yes, I know I should do that before asking for advice
Anyway, questions. The thing I've been dissatisfied with is the treble. I really like the sound of the midrange driver, but I've heard smoother treble in many speakers. Now I have a pair of Fountek JP-3.0 ribbon tweeters that I plan to try here. These should match the efficiency of the mid fairly well. I plan to start out with the same XO. I'll probably also start out by mounting the ribbons on the same baffle (assuming they fit), probably directly above the existing tweeters (remember that the baffle is flipped).
Does that sound reasonable? It will place the ribbon at ear height, which is important based on everything I've read. It will also place the ribbon almost beside the midrange driver - I'm not sure if that will be a problem or not. Should I put together a new baffle for this? If I do, what kind of mounting would be recommended as a starting point? Maybe put the mid above the ribbon, but lined up with it vertically? Should they be in the middle of the baffle or offset to a side?
Assuming I get my measurement jig set up, any advice on measuring the ribbon tweeter? I know I shouldn't send a low frequency to it, and should always keep a cap in series. I can run FR measurements on it that way, I guess, but wouldn't that affect impedance measurements? Also, about measurements in general - I don't have the luxury of mounting these on a stand in the middle of a field. Can I get useful results using Speaker Workshop with a microphone in my living room?
OK, that's all the questions in my mind at this point. I'll probably think of more as I go along. And once again, hello to everyone here.
Saurav
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