My first 3 way speaker build

[rpb]

Re: My first 3 way speaker build

What's your high pass on the mid? Does it use a rather large coil, or a small one? Playing with PCD on a different driver, it looks like a big coil helps get the impedance up. I mean something around 4mH when I say big.

[chrisn]

Re: My first 3 way speaker build

I noticed there are different advertised specs for that woofer, such as vas between 66-102: http://www.sbacoustics.com/index.php...29swnrx-s75-6/ Have you tried modeling your box with the various listed numbers? It's not unusual to pad the tweeter and the mid, and depending where and how you pad them can change the impedance and phase angle your amp sees. Split resistors for larger values, like 4 ohms on the amp side, and a similar amount the driver side, or a resistor in parallel (across the terminals of the driver) are different ways to match the drivers relative levels, Crossing to the mid higher could help too, and going second order electrical on the mid high pass if it isn't already. Rpb's advice above is right on.

[Sydney]

Re: My first 3 way speaker build

...To make these really sound good, I had to pad the mid with 7.7 ohms of resistance, and the tweeter with 11 ohms. Now they sound perfectly magical, but I don't think my amp can handle what I'm doing. These are terribly inefficient, after I listened to them for about 2 hours last night I could fry eggs on the amp I'm using to voice these (Adcom GFA-5500), it was almost too hot to touch....

That's not good - from a personal perspective, post amplification attenuation is like riding the brakes.

[isaeagle4031]

Re: My first 3 way speaker build

That's not good - from a personal perspective, post amplification attenuation is like riding the brakes.

The only way you would not have post amplification is if you can either find drivers that "perfectly match" spl wise (not going to happen, particularly in a 3way) or go active. Using resistors to level match and/or response shaping is quite common and really the best way from a passive crossover standpoint.

[Sydney]

Re: My first 3 way speaker build

...or go active. ...

:D

[mattsk8]

Re: My first 3 way speaker build

What's your high pass on the mid? Does it use a rather large coil, or a small one? Playing with PCD on a different driver, it looks like a big coil helps get the impedance up. I mean something around 4mH when I say big.

I noticed there are different advertised specs for that woofer, such as vas between 66-102: http://www.sbacoustics.com/index.php...29swnrx-s75-6/ Have you tried modeling your box with the various listed numbers? It's not unusual to pad the tweeter and the mid, and depending where and how you pad them can change the impedance and phase angle your amp sees. Split resistors for larger values, like 4 ohms on the amp side, and a similar amount the driver side, or a resistor in parallel (across the terminals of the driver) are different ways to match the drivers relative levels, Crossing to the mid higher could help too, and going second order electrical on the mid high pass if it isn't already. Rpb's advice above is right on.

I did model the box and it showed a 2.25 box would give me f3 of 25 Hz using SB's specs. The box I have now is 2 cf and should have f3 of 27 Hz using a 3"x12" port. The mid to tweeter is around 2.2k, the woofer to mid was 225, but I need to measure it again to see what the 4.0 inductor did.

But... I made very positive advancements last night . I put a 4.0mh in place of the 3.0 on the woofer, used a 200 rather than the 250uf, and still used the 2.4 resistor and the bass sprung to life (thanks again... and again Craig K for finding this out). I have the mid padded a bit, and the tweeter quite a bit (but a lot less than yesterday), now the bass is almost perfect (is the bass ever totally perfect in anything?). I'm super happy with where these are now, I think I need to just listen for a week or so at this point and digest what's there before I move into playing with the high frequencies. They're a tad thin in the upper midrange, but they're also new speakers and I imagine that 7" Scanspeak mid will take a while to break in when it isn't playing much bass at all. My amp didn't seem to mind this at all yesterday, and I had it playing for about 4 hours.

I really appreciate all the tips and suggestions, I love this forum. I've made a lot of good friends and met some really cool people . Now I see why people like a good TM or MTM, 3 ways take a LONG time and a lot of work :eek:. I was a tad nervous when I fired these up that I'd lit about $1000 on fire, glad it's starting to come together :D.

From what I hear so far, the really nice thing is that these drivers all seem to have plenty to offer. As much as I've practically damned that SB29 woofer here because of my lack of understanding, it really is a good driver. It doesn't miss any of the bass frequencies, it has a very smooth and consistent sound all the way into the 20s. Some drivers will be exaggerated in the bass frequencies somewhere, but then they'll be lacking somewhere else; but that isn't the case with these, they're smooth all the way through.

Now that I have the bass sorted out, I'm honing in on that SS HDS tweeter; not sure where I stand on that yet. It has detail like crazy, but I'm not sure yet if I'd like a tad more body in the lower end. I'll listen for a week, then go back to playing with it.

That's not good - from a personal perspective, post amplification attenuation is like riding the brakes.

That's a good analogy, it's like putting a 200 HP restrictor plate on a 500 HP engine. But,I'm glad that's sorted out now!!!

[Sydney]

Re: My first 3 way speaker build

...My amp didn't seem to mind this at all yesterday, and I had it playing for about 4 hours....
...But,I'm glad that's sorted out now!!!

So nothing is running hot?

[mattsk8]

Re: My first 3 way speaker build

So nothing is running hot?

Not abnormally. Those Adcom amps are tough to monitor though because just sitting idle with the power on the thing gets pretty hot anyhow. It does have thermal protection, and "distortion" LEDs. But it isn't doing anything out of the ordinary, and I ran it pretty hard last night

[Sydney]

Re: My first 3 way speaker build

Not abnormally. Those Adcom amps are tough to monitor though because just sitting idle with the power on the thing gets pretty hot anyhow. It does have thermal protection, and "distortion" LEDs. But it isn't doing anything out of the ordinary, and I ran it pretty hard last night

That's good. I couldn't tell from the description the exact nature of the changes. I also underlined nothing to include resistors in the passive crossover as they can get HOT.

[mattk]

Re: My first 3 way speaker build

That's good. I couldn't tell from the description the exact nature of the changes. I also underlined nothing to include resistors in the passive crossover as they can get HOT.

Yes, there was even a thread a while back about resistors burning out (in a Statement, iirc). I keep playing around with a three-way design that would require me to pad the mid with 4 ohms, and if I do end up building it I'll be using multiple resistors to achieve the 4 ohms rather than a single, and might even heat sink them. I'm still trying to find a mid that fits the rest of my requirements but doesn't need to be padded.

[isaeagle4031]

Re: My first 3 way speaker build

Yes, there was even a thread a while back about resistors burning out (in a Statement, iirc). I keep playing around with a three-way design that would require me to pad the mid with 4 ohms, and if I do end up building it I'll be using multiple resistors to achieve the 4 ohms rather than a single, and might even heat sink them. I'm still trying to find a mid that fits the rest of my requirements but doesn't need to be padded.

About any mid is going to need to be padded imo. Once you apply the filters, you will get a band pass gain to some degree. If you place the resistor after the initial cap, you also greatly reduce the amount of energy the resistor sees. If you really do need a resistor before, amazon has 100w units available at very reasonable prices. In order to get the full wattage rating of any resistor, it really needs to be mounted to a heart sink.

[mattsk8]

Re: My first 3 way speaker build

About any mid is going to need to be padded imo. Once you apply the filters, you will get a band pass gain to some degree. If you place the resistor after the initial cap, you also greatly reduce the amount of energy the resistor sees. If you really do need a resistor before, amazon has 100w units available at very reasonable prices. In order to get the full wattage rating of any resistor, it really needs to be mounted to a heart sink.

Yes, there is 11 ohms of resistance in the Statements mids (not counting shunt), and 10 ohms in the tweeter (per crossover). I have 9 on the tweeter and 5 on the mid in mine. Not as bad as I thought. I have 50 watt 2 ohm resistors in the woofer shunt and that gets a little warm if I'm whaling on them, I will get some 100 watt ones for that. I like those aluminum zistor resistors from Meniscus, those are 25 watts and once I have this ready to solder I'll get those for the mid and tweeter in the final assembly.

[isaeagle4031]

Re: My first 3 way speaker build

The zistors are great pieces. Overkill for many builds yes, but the size of them, plus the heavy duty leads make them worth their price and even that is not extreme m

[Wolf]

Re: My first 3 way speaker build

About any mid is going to need to be padded imo. Once you apply the filters, you will get a band pass gain to some degree. If you place the resistor after the initial cap, you also greatly reduce the amount of energy the resistor sees. If you really do need a resistor before, amazon has 100w units available at very reasonable prices. In order to get the full wattage rating of any resistor, it really needs to be mounted to a heart sink.

The bold above is not entirely true. If you have a resistor and cap in series in a standard 12dB electrical network, then the cap and resistor are series components, and position makes no difference in terms of operation. Wired either way, the resistor will not see the entire bandwidth due to the cap in junction with it, and that the sound going through is AC.

Now- if you have the parallel resistor out front as well, positioned after the series resistor, and before the entire network, then the resistors will see the entire bandwidth of the audio signal.

Sandcast resistors are capable of full rating without a heatsink. Heatsinks can improve any thermally-coupled resistor's capacity though. Panel-mount units; such as the Arcol, Dale, Zisters, etc; derate without a heatsink applied. For example, a 25W panel-mount Dale is truly 10W without a heatsink attached.

Later,
Wolf

[isaeagle4031]

Re: My first 3 way speaker build

The bold above is not entirely true. If you have a resistor and cap in series in a standard 12dB electrical network, then the cap and resistor are series components, and position makes no difference in terms of operation. Wired either way, the resistor will not see the entire bandwidth due to the cap in junction with it, and that the sound going through is AC.

Now- if you have the parallel resistor out front as well, positioned after the series resistor, and before the entire network, then the resistors will see the entire bandwidth of the audio signal.

Sandcast resistors are capable of full rating without a heatsink. Heatsinks can improve any thermally-coupled resistor's capacity though. Panel-mount units; such as the Arcol, Dale, Zisters, etc; derate without a heatsink applied. For example, a 25W panel-mount Dale is truly 10W without a heatsink attached.

Later,
Wolf

You are right Ben. My wording was off. I was referring to the HP filter on the mid.