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Re: Back EMF? [message #67414 is a reply to message #67413]

Wed, 04 May 2011 12:24

Frihed89
Messages: 30
Registered: June 2009
Location: Copenhagen, Denmark

Baron

No problem. Troels has made some nice speakers. I simply showed him a pic of the Pi-4s, so he didn't have much to go on.

I am going to make these. My step son has agreed to make the cabinets. I'll do the rest, slowly, culminating in the purchase of the cross-over. Probably in the fall.

My new amps (2A3) don't get here until July or August.

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Re: Back EMF? [message #67418 is a reply to message #67414]

Wed, 04 May 2011 18:43

Matts
Messages: 359
Registered: May 2009

Grand Master

What amps are you using? I think the parafeed design typically has a little better damping than the classic single end, and also a better quality output xfmr is nicer, but you'd be fine either way with a well-designed amp. I also think that the "honest" xover design and the fact that there's no drastic dip in the impedance curve in Pi 4's is helpful with smaller tube amps. No offense meant with guru comment- I didn't know anything about the other guy- just kidding around. Hope that was clear by the smiley! You'll be quite happy with the Pi 4's.

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Re: Back EMF? [message #67423 is a reply to message #67418]

Wed, 04 May 2011 20:33

Frihed89
Messages: 30
Registered: June 2009
Location: Copenhagen, Denmark

Baron

Fi 2A3 monos. They are DC coupled but not parafeed.

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Re: Back EMF? [message #67436 is a reply to message #67423]

Thu, 05 May 2011 10:12

Wayne Parham
Messages: 18675
Registered: January 2001

Illuminati (33rd Degree)

You'll have no trouble at all driving four π speakers with that amp. They're about as tube-friendly as speakers come - very efficient and benign with respect to impedance load. Seriously, there are few other speakers that are as easy to drive.

This back-EMF thing has actually been a topic of several discussions, a particular focus of mine many years ago. It's a big issue for tube amps, and it's one of the things that my loudspeakers are particularly good at. Look back through the links from my earlier post, if you're interested. Seriously, we've got this covered. Cool

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Re: Back EMF? [message #67437 is a reply to message #67436]

Thu, 05 May 2011 10:34

Frihed89
Messages: 30
Registered: June 2009
Location: Copenhagen, Denmark

Baron

Thanks Wayne,

I will.

I take it that you think the JBL drivers are worth the extra €?

Also, I see you think that the smallest sonic improvement comes from better caps. But I wonder if someone hasn't fitted out the entire crossover in a way that might give additional benefits?

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Re: Back EMF? [message #67438 is a reply to message #67413]

Thu, 05 May 2011 10:36

Wayne Parham
Messages: 18675
Registered: January 2001

Illuminati (33rd Degree)

spkrman57 wrote on Wed, 04 May 2011 11:57

I have used the following small tubed amps on my 4-Pi spkrs utilizing 8 and 16 ohm 2226 drivers with no problems:

45/2A3/300B/Triode strapped EL34

I will re-iterate what Wayne has said in the past concerning the 2226 liking more wattage than what the little amps put out for max performance (10 % of max or 60 wpc).

I agree with that, but I will say that the dropoff in performance using little tubed amps under 10 wpc is not really that drastic. I don't know too many other 15" drivers that would work as well for me!!!

Just my 2 cents worth of course!

Regards, Ron

Absolutely, I agree. I use mine with 10-watters and have been very happy with them on 2A3-based 2-watters too. They're fine, sound great and are quite loud.

The thing about the 2226 at low power levels is not related to Zmax or back-EMF in any way. It's the fact that the driver was designed to handle a lot more power, and the electro-mechanical parameters shift at moderate levels. So at flea-power, the tuning of the system makes it lack bass a little bit. It will actually shift to have more bass at higher power levels. But the speaker was design with this shift in mind, and it never shifts into an underdamped (peaky) condition. It is always slightly overdamped, and shifts a bit under the curve, but never anywhere close to an underdamped condition. This is a very friendly alignment, tolerant of shifts.

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Re: Back EMF? [message #67439 is a reply to message #67437]

Thu, 05 May 2011 10:46

Wayne Parham
Messages: 18675
Registered: January 2001

Illuminati (33rd Degree)

Frihed89 wrote on Thu, 05 May 2011 10:34

I take it that you think the JBL drivers are worth the extra €?

Absolutely. They have shorting rings that provide flux modulation control. The improvement from that feature is huge.

Frihed89 wrote on Thu, 05 May 2011 10:34

Also, I see you think that the smallest sonic improvement comes from better caps. But I wonder if someone hasn't fitted out the entire crossover in a way that might give additional benefits?

Not sure what you mean. The crossovers are highly optimized and have a nice clean forward lobe. Even the stock build uses great parts, or you can substitute with upgraded premium parts. Honestly, this is a price-no-object solution, even though it's not particularly expensive. I don't think there are any "additional benefits" possible, this is a no-compromise solution.

The one area I would suggest you look for improvements is external to the main four π loudspeakers. Upgrade them with the premium drivers and you have the best you're going to get as far as mains are concerned. Where you can improve the system is by adding subs. Drive them with a separate amplifier and let them provide solid foundation and smooth room modes. See the last few pages of the whitepaper below for more information:

High-Fidelity Uniform-Directivity Loudspeakers

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Re: Back EMF? [message #67442 is a reply to message #67439]

Thu, 05 May 2011 13:31

Frihed89
Messages: 30
Registered: June 2009
Location: Copenhagen, Denmark

Baron

I intend to buy the higher price mid-range drivers and tweeters from Germany or the UK. Is that what you mean? I don't particularly relish spending a lot of money on cross-over caps. (The 2A3 that I am getting has no film caps at all. It is a single stage DC amp). Since I'll buy the cross-over units from you, already populated, I'll take whatever you give me. What are the standard grade caps ? Sonic-caps or something like that?

My amps are: 12W Class A PP triode made by Jef Larsen, a 10W 300B integrated made by Audio Note (UK) and 3.5 W 2A3 made by Don Garber (Fi).

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Re: Back EMF? [message #67443 is a reply to message #67442]

Thu, 05 May 2011 14:38

Wayne Parham
Messages: 18675
Registered: January 2001

Illuminati (33rd Degree)

Frihed89 wrote on Thu, 05 May 2011 13:31

I intend to buy the higher price mid-range drivers and tweeters from Germany or the UK. Is that what you mean?

Yes, the most important parts to upgrade are the midwoofer and tweeter compression driver.

Frihed89 wrote on Thu, 05 May 2011 13:31

I don't particularly relish spending a lot of money on cross-over caps. (The 2A3 that I am getting has no film caps at all. It is a single stage DC amp). Since I'll buy the cross-over units from you, already populated, I'll take whatever you give me. What are the standard grade caps ? Sonic-caps or something like that?

We maintain inventory of Erse, Solen, Jantzen (Cross-Cap and Z-Cap) and Auricaps. All are polys. When I get an order that specifies a particular brand, then I use them of course. But if not, I just use whatever I have most stock of. They're usually Erse or Jantzen Cross-Caps, but may be another brand. They'll definitely be high-quality poly caps.

Frihed89 wrote on Thu, 05 May 2011 13:31

My amps are: 12W Class A PP triode made by Jef Larsen, a 10W 300B integrated made by Audio Note (UK) and 3.5 W 2A3 made by Don Garber (Fi).

Excellent. Sounds very much like the amps I have in various rooms. I have an Audio Note Kit 2 (SET KT88), a Stoetkit (UL 6BM8) and an Image Audio (SET EL34).

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Re: Back EMF? [message #67469 is a reply to message #67443]

Fri, 06 May 2011 06:21

Frihed89
Messages: 30
Registered: June 2009
Location: Copenhagen, Denmark

Baron

What is the difference, if any, between a JBL 2226H and 2226J? Which one is the "right" one?

Is the "wave guide" (please don't eat me alive) for the tweeter on the Four- Pi available from commercial vendors or made to your specs? I am in Denmark.

What happens (both the good and bad) when you add a super tweeter on the top of the box? Will it help my dog appreciate music better? Or me? I suspect it requires a new or another cross-over, correct?

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