I have a pair of 15 inch un-enclosed musical instruments [from MCM Electronics] which I bolted to the ceiling joists in my semi-finished basement listening area. They are angled to beam at the sweet spot on the floor as I lay down on my back listening to music. They sound great, and are better balanced tonally,and more efficient with a current source amp than with an ideal voltage source amp. I am clumsy at woodworking. The boxes I built were ugly. The above was my simple solution to Infinite or Open Baffle. The two corners of this room behind the raw drivers have diy suppressors of standing waves per the teaching of the patent granted to Threshold Corporation; inventor Nelson Pass.
Most probably the impedance versus frequency plot of the Fostex driver in the Arpeggio speaker [Figure 08, without Zobel] is like the one that you have.(s)Was goign to ask you that as well. Double Zen
Ilquam, Read Arpeggio speaker article on main page. Very good read, as commented by Nelson.
Ihquam,
Maybe you should let the amp burn in for a while.
Somethings get better with time.
I would try adjusting output current and feedback too.
I read the Stereophile article: B&W Compact Domestic Monitor 1 loudspeaker Sam Tellig, December 1998 | Stereophile.com and they tested your speakers with a SE 300b tube amp and found the "Bass was surprisingly tight—so long as I didn't push the volume levels."
Rush
I suspect the most of the time "burn-in" is one's ears getting familiar with the sound rather than components actually changing. OTOH, some components (like unsealed resistors) might undergo a change in moisture content.
Rush and lhquam: May also consider using a power resistor in parallel with the loudspeaker to knock down or diminish the specific high impedance values. Is it safe for Teaser-6 to drive a net 2-4 Ohm load? Noting that the minimum impedance of B&W is 5 Ohms? Mr. Pass was first to write about this tweak of the loudspeaker in an article on www.firstwatt.com.
I believe so as on page 4 of the article He suggested to parallel 47 Ohms with the current source amp [Teaser-6 is a very mild case of it] which is simultaneously // to the load. Maybe in reference to the high impedance peak of the woofer at its resonance. Thus, a possible peak loudspeaker impedance of 47 Ohm [in B&W] will be knocked down to ~24 Ohms. Its 5 Ohms minimum is less so perturbed.
Isn't the reason for the 47 ohm parallel resistor to reduce the maximum voltage requirement of the transconductance amplifier? If the amplifier has any negative feedback, the voltage will be limited by the (non-simple) effect of the feedback network and the load resistance.
I am not skilled enough to answer your question. Calculate the effective impedance versus frequency of the loudspeaker with //47 Ohm or lower value resistors across it. This is the new load which Teaser-6 sees. It'll have a similar general shape as the parent with more attenuation of the high impedance peaks relative to the base 5 Ohms. The resistor will share output power with the loudspeaker to waste relatively more at high impedance relative to that at low impedance. Also, I maybe wrong. Shotgun approach will be to //with 47, 25 Ohms etc and hear difference if any.
What is your expection for Zo of Mr. Pass's F6?not needed with F6
it's having lowish output impedance , so no use of wasting power on parallel resistor
except if someone want some SE bias, but then resistor must be placed in other position ....
That is the Sound I like most....! Combined with Zen Pot.....
this time , it was mu without ...follower part
Mu (negative) - Wikipedia, the free encyclopedia
Mumm is the word for the value of Zo of Mr. Pass's F6.
All of my listening to the Teaser-6 has been with a 50 ohm + 10 ohm feedback network, giving a measured gain of 4.7. The bias current is 1.3A with 25 volt power supplies. I have not experimented with running it open-loop.
I added an additional 50 ohm parallel resistor at each speaker and it seems to help a bit.
Here are some bench measurements:
Teaser-6 right channel.
Output Impedance Test:
60Hz in, 4V peak out into 8 ohms, Fluke reads 2.84V AC
60Hz in, into 4 ohms, Fluke reads 2.40V AC
This gives 2.84 ohms output impedance and a damping factor of 2.4 into 8 ohms.
Frequency Response Tests:
100Hz in, 4V peak out on scope
No measurable low freq roll-off down to 10Hz
50ohm/0ohm feedback network - open-loop with 50 ohm parallel load
60Hz in, 4 volt peak out into 8 ohms
Fluke reads 2.84V AC
0.185V peak input -=> Gain = 21.6
60Hz in, x volt peak out into 4 ohms
Fluke reads 1.54V AC
Response tests
100Hz in, 4 volt peak out on scope
No measurable low freq roll-off down to 10Hz
10kHz 3.475V peak out -1.22dB
20kHz 2.725V out -3.33dB
31.25kHz 2.0V out -6.0dB
I added an additional 50 ohm parallel resistor at each speaker and it seems to help a bit.
Here are some bench measurements:
Teaser-6 right channel.
Output Impedance Test:
60Hz in, 4V peak out into 8 ohms, Fluke reads 2.84V AC
60Hz in, into 4 ohms, Fluke reads 2.40V AC
This gives 2.84 ohms output impedance and a damping factor of 2.4 into 8 ohms.
Frequency Response Tests:
100Hz in, 4V peak out on scope
No measurable low freq roll-off down to 10Hz
- 10kHz 3.9V peak out, -.22dB
- 20kHz 3.65V peak out, -.79dB
- 40kHz 2.9V peak out, -2.79dB
- 83kHz 2.0V peak out, -6.0dB
50ohm/0ohm feedback network - open-loop with 50 ohm parallel load
60Hz in, 4 volt peak out into 8 ohms
Fluke reads 2.84V AC
0.185V peak input -=> Gain = 21.6
60Hz in, x volt peak out into 4 ohms
Fluke reads 1.54V AC
Response tests
100Hz in, 4 volt peak out on scope
No measurable low freq roll-off down to 10Hz
10kHz 3.475V peak out -1.22dB
20kHz 2.725V out -3.33dB
31.25kHz 2.0V out -6.0dB
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Not my experience. Don't know the reason, but my system sounds better after 2 hours from cold. It also sound better weeks later when something major has been changed.
Friends have said the same thing. Don't want to hijack the thread with VooDoo.
It may be the sweet spot is more solidly settled in. (If that makes any sense?)
But in your case the sweet spot may not have been found yet.
Rush