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Cure for brightness [message #64876] Wed, 24 November 2010 13:05 Go to next message
notben is currently offline  notben
Messages: 11
Registered: October 2009
Chancellor
Hello gentlemen.
I have been living with a pair of 2pi monitor speakers that I built with birch ply for about six months now. Overall, they have at least a couple hundred hours or more on them.
I absolutely love their detail and resolution. The response is quick, the bass is clean, the midrange is extremely detailed with excellent definition in what I call the transition zones ( around 250, 2k & 6K hz respectively ). Overall I am very pleased. I especially love tube rolling with these speakers because I can instantly hear the dominant characteristics of different tubes. Very revealing for a monitor speaker.

However I still find them to be a tad bright and even a little fatiguing. Here is how I have tested the speakers to see if it is actually the speaker. I have tested them with two tube amps and two SS amp, two different tube preamps and one SS tuner. I have run them in three different rooms: my music room which is lightly treated with bass traps and some ceiling treatment (this is also my guitar room), my study (which is a very flat and dead room ), and my living room ( which is tolerable at best).
I have also cycled through different speaker cables -- mogami, anti-cable, tributaries; and different RCA's -- anti-cable, monster, radio shack.
The brightness follows the speaker.

So now I want to try a few things to see if I can find the culprit or maybe tame it a little bit.
1. I am thinking about trying a different cap on the tweeter. It currently has the 10uf Solen that shipped with it. I may try an Obbligato Gold Premium, a Mundorf Supreme (if I feel like spending $90), or maybe a motor run if I can mount it in the speaker.

2. Could I have damaged one of the tweeters? I can't hear any difference between the two speakers. One of my preamps, a Bottlehead Foreplay, has separate volume controls and I can't hear any real difference between the two, but I don't want to rule out anything.
So, I could try a new or different set of tweeters.

3. The most drastic and time consuming thing would be to build some MDF cabinets to compare.

Any ideas or opinions of what I could try or test please share them. Thanks.
- Benton
Re: Cure for brightness [message #64877 is a reply to message #64876] Wed, 24 November 2010 13:58 Go to previous messageGo to next message
steve f is currently offline  steve f
Messages: 236
Registered: May 2009
Master
Hi Benton,

My best guess is to try to pad the tweeter volume down slightly. Very slightly; you will be surprised what a difference a decibel or two makes. I see no advantage in changing caps as the type of cap is more important than the brand. Don't rebuild the cabinet.

Steve
two π speaker response curve [message #64878 is a reply to message #64877] Wed, 24 November 2010 14:25 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18678
Registered: January 2001
Illuminati (33rd Degree)

The tweeter is actually just a smidge lower than the woofer in this speaker. One can surely attenuate it more with padding, to voice the speaker for personal taste. But I think it is probably worthwhile to point out it is already shelved down from the woofer by a slight amount.


http://www.pispeakers.com/Measurements/two_Pi_with_DX25_take_1.gif
two π monitor response curve

http://www.pispeakers.com/Measurements/twoPi_tower_response.jpg
two π tower response curve
Re: Cure for brightness [message #64879 is a reply to message #64877] Wed, 24 November 2010 14:29 Go to previous messageGo to next message
notben is currently offline  notben
Messages: 11
Registered: October 2009
Chancellor
steve f wrote on Wed, 24 November 2010 14:58

I see no advantage in changing caps as the type of cap is more important than the brand.

Which is why I am thinking about those different caps, all of which are different types. Motor run being oil, Obbligato a gold and oil and the Mundorf a polypropylene and film.
Re: Cure for brightness [message #64880 is a reply to message #64879] Wed, 24 November 2010 14:58 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18678
Registered: January 2001
Illuminati (33rd Degree)

Some oil-filled motor runs are pretty good, reasonably priced and tend to warm up the sound. I'd be interested to hear what you think of them. Be sure to get an oil-filled can, because there are other kinds of motor run caps these days, most of them using some kind of plastic dielectric. Some of them are pretty cheap and nasty. So when searching for oil-filled motor-run caps, don't just look for "motor run", also look for "oil" or "dielectric fluid".

I don't think you'll hear a difference with a Mundorf M-Series because it is basically the same as the stock cap. But the price isn't too bad either, about the same as the Solen that came with the kit. The Supreme and some of their other series are more expensive, and I'm not sure it makes sense to use in this speaker. Guess you could if you wanted to.

The Obbligato might sound different to you, but my guess is it will sound the same, or at least too close to call. It's like the Auricaps in price and, I suspect, in sonic character.

I've used Audio Note capacitors, Mundorf Supremes, Jantzen Superior caps and Auricaps and find each of them to be nice, but then again at those prices, you would expect them to be. I tend to reserve these higher-priced caps for the speakers with premium driver options. The JBL and AE drivers are pretty expensive, and justify using capacitors in the $20 to $200 range, at least in my mind. The speaker drivers cost several hundred bucks, so a hundred or two hundred dollars spent in the crossover parts is probably well-deserved. But to be honest, I can't see spending more on the passive components than the drivers cost.

That said, none of the capacitors you've mentioned cost more than the drivers, and I wouldn't wince at their price tags. I think that Obbligato is the most expensive of the three you've mentioned, at about $25.00. The Mundorf MKP is about the same as the Solen, about $7.50. Motor runs can be bought for just about any price, from less than ten bucks to who knows what. But none of these is really outrageously priced. Might be worthwhile to try them all, especially if you already have them on hand.

Re: Cure for brightness [message #64881 is a reply to message #64880] Wed, 24 November 2010 16:06 Go to previous messageGo to next message
notben is currently offline  notben
Messages: 11
Registered: October 2009
Chancellor
Thank you Wayne. I think I am going to start with the motor run. I rarely hear of anyone hating them in crossovers, and for the money, it is one of the most economical places to start.

The trick will be deciding how to mount it, since the stock wiring is inside the box. I guess I could clamp it to the side of the speaker not insulated or maybe use some zip ties to keep it upright. I will report back.
Re: Cure for brightness [message #64886 is a reply to message #64880] Wed, 24 November 2010 22:22 Go to previous messageGo to next message
Bill Epstein is currently offline  Bill Epstein
Messages: 1088
Registered: May 2009
Location: Smoky Mts. USA
Illuminati (2nd Degree)
Your complaint reminds me of the Piezo tweeter days. I'd look at the room.

The Vifa XT 25 tweeter is 2 dB less efficient than the Alpha 8 as Wayne said and, compared to other domes, is in the less-fatiguing/detailed camp. The Zaphaudio test called it "the smoothest and most extended response curve....".

http://www.zaphaudio.com/tweetermishmash/

Get some good room treatment advice at the Rives Forum; for instance, 1" thick stiff fiberglass (Owens-Corning 604) panels offset from the wall 2" will attenuate frequencies from 1500 Hz up. Add drapes, try live-end, dead-end, move reflective surfaces like glass-covered paintings and mirrors, etc.

If you must re-cap, I'm a big fan of the copper Obbligatos as well as old Aerovox motor runs in the oval cans. Use'm in all my stuff.

Re: Cure for brightness [message #64889 is a reply to message #64886] Thu, 25 November 2010 04:15 Go to previous messageGo to next message
steve f is currently offline  steve f
Messages: 236
Registered: May 2009
Master
The fact that the speakers sound bright in any room you put them in is intriguing. I agree with Bill that room treatments bring significant changes.
Motor run caps (oil filled) will make the tweeters sound a bit warmer. I wonder if anyone has measured them vs. film types in a PI 1 or 2. Please keep us updated.
Re: Cure for brightness [message #64890 is a reply to message #64876] Thu, 25 November 2010 06:57 Go to previous messageGo to next message
AudioFred is currently offline  AudioFred
Messages: 377
Registered: May 2009
Location: Houston
Illuminati (1st Degree)
The tweeter in my One Pi's sounded bright to my ears. Installing a one ohm resistor in the tweeter signal path solved the problem. It can be inserted before or after the cap.
Re: Cure for brightness [message #64891 is a reply to message #64876] Thu, 25 November 2010 11:32 Go to previous messageGo to previous message
GarlandB is currently offline  GarlandB
Messages: 27
Registered: July 2009
Location: Natick, Massachusetts
Chancellor
Hi Benton and happy Thanksgiving to all,

Just a couple of ideas came to mind: You didn't mention your source? If your using digital gear then often a graininess can sneak through into the music from there. Many times we result to measures that depress or blurr the top octaves in a quest to tame "digititus". I have always had to deal with lesser quality CD source in my systems and only was able to really open up the upper frequencies by upgrading and modding my CD players. Now my somewhat tuned Cambridge Audio 640C vII {PS caps,Coupling caps, Opamps,etc) is nicely smooth but dynamic at the same time. This has allowed me to really hear what improvements in the following compnents actually sound like{ie. more musical}. See my post below on "more fun with caps". I really do agree with those who feel that there is a high freq. tizzieness with Solens and recommend film and foil caps over metalized film. Oil can sound good too. But if the signal coming from the source is distorted all you'll get more exposure of that from the clearer, truer performing caps.
Oops! I was going to write more but I have to get going on the Thanksgiving dinner!

So try better caps in your 2Pis but take a look at your sources too.

Garland
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