Dennis Had Inspire Amps

[Wgarcia]

Maybe a simple question (and maybe already answered someplace) but how hot should my recent issue Fire Bottle get (not counting tube heat of course)? The thing sounds fabulous regardless, but the the transformers get a bit toasty regardless of how hard the amp is driven (not so hard really, at least from my perspective).

[BearCityUSA]

Originally Posted by beowulf

Thanks for sharing and I find your concept/thoughts on this very interesting as I am an Omega owner myself.

When the RS7 driver based speakers first came out there were 3 different flavors of drivers.

(1) the "Vintage" ones which did not have a whizzer cone,
(2) the "Standard" ones that did have a whizzer cone,
(3) the "AlNiCo" ones which also had a whizzer cone.

I was just wondering ... are your RS7 drivers the "Vintage" type (without a whizzer) or the "Standard"/"AlNiCo" type (with a whizzer cone)?

The "Vintage" ones that do not have a whizzer cone roll off a lot earlier (somewhere @ 17kHz) than the "Standard"/"AlNiCo" ones that roll off a bit higher (somewhere @ 20kHz).

I've owned and heard both the "Vintage" and "Standard" versions of the RS7 drivers and much prefer the "Standard" type drivers.

Beowulf,

Mine are the Standard type as you describe them with the Wizzer cone. Not Alnico.

Scott

[BearCityUSA]

Originally Posted by pstrisik

I'm very interested in the notch filter and hi pass filter diagrams. Sounds like fun to work with. As you may recall, I supplemented the low end with powered woofers (up to 250Hz) and up/rear firing tweeters with simple capacitor hi pass at about 14kHz. Seems consistent with both of your impression of what they need.

Can't PM here though. Catch me on the Omega circle? Or post them here?

Thanks....

Peter,

I do recall your "4 way" system and yes I think this DH unit is attempting something similar. Filling in the ends of the audible spectrum so to speak.

I inquired with Dennis and he said to go ahead and post this FOR ALL.

As to exactly what DH rigged up as the Contour Network. He has a 1.0mh inductor, a 75 ohm (5W), a 20 Ohm (5W), and a 4 mfd capacitor all wired in parallel. As I said before, Dennis specifically refers to this as a Contour Network.

"Just a short note … the network I slung together is called a contour network. Not to be confused with a notch filter. The contour network shelves a band of frequencies while letting frequencies below and above the design attenuation frequencies come through at the nominal input level."

Per Rosco's post there may be argument that the addition of the CAP makes this a Notch Filter. I will not be arguing this with a man with 60+ years experience. DH refers to it as a Contour Network (CN) so I will be from now on as well.

With a flurry of emails last week regarding this CN Dennis offered this:

"Have a look at a 1st order 6 dB crossover with a center frequency of 2K. 2K is where the human ear is most sensitive."

www.apicsllc.com/apics/Misc/filter2.html#first

Use 8 Ohms for both driver values and 2k hz to follow this:

"The cap is 10 MFD and the inductor is .6 mH and simply double the speaker impedance .. in this case 8 ohms [for the resistor]. Soooooooo, 1/2 the cap = 5 MFD/ double the inductor 1.2 mH and double the impedance of the speaker in use 8 ohms x 2 = 16 ohms.."

"The method for calculating the contour network is one half the capacitance … twice the inductance … and twice the speaker impedance. Therefore, to be more precise than the network I clouged together would be a 5 MFD cap, a 1.2 mH inductor and a 16 ohm resistor. This is a center frequency of 2K. Lower the resistor and the shelf is shallower"

So the values of the one DH "cloughed together" stated above (4 mfd, 1.0 mh, 16 Ohm) was with spare parts. These calculated values (5 mfd, 1.2mh, 16 ohm) are more appropriate for what he was attempting to accomplish. I am planning to order up some additional resistors to test a "shallower" shelf as well. I have read somewhere that using two 10W resistors in parallel works better than one. Dissipates heat better than a single. DH used the 75 Ohm and the 20 Ohm to get 16 ohm combined. I am not sure if that was intentional or if he was just scrounging parts.

Here is a cool website where you can see what this CN does to the signal. The "shelf" effect is pretty clear.

www.mh-audio.nl/parallelnotchfilter.asp

As for the crossover he sketched out for the additional tweeter. He suggested a 6 Ohm resistor in series with a 3 mfd cap. "If to bold try a 10 Ohm resistor instead." The tweeter was the Morel 378. Incidentally the same used in the Inspire speakers he and Allen (Analog Addict) designed.

For you Peter, and Rosco, and Beowulf,... Do you think this would be something to post over on AudioCircle? I do not want to start an argument or imply there is an improvement to Louis' speakers on his owner's threads,... but if others may want to play around and find a better synergy to their system, maybe... Your thoughts are welcome.

Scott

[BearCityUSA]

Originally Posted by Analog Addict

If you don't get back to RTP by Sept, I will be in Asheville for a conference 9/8-9 10, and would be happy to bring my PSE 45 along for a demo. I'm hoping my PSE 71-A will also be ready by then....

No plans on the schedule to be back in RTP before Sept so please do get in touch with me during your visit to Asheville. I would love to hear one or both of your PSETs as well. Look forward to it.

Scott

[BearCityUSA]

Originally Posted by zip

Anybody know the differences between the Had LP27 and the LP3 preamps ?

Sure would be nice if Dennis Had would have a website for information on his Inspire products !

Waiting days for email replies doesn't work well .........

I own both and they are both great but different. MY LP-27a is a Special Edition with all the upgrades. An absolutely wonderful piece. The best I can offer is that it is beautifully transparent. Also the 27 and 56 tubes are relatively inexpensive and according to Dennis should last for 15 years. He does spend quite a bit of time matching pairs in the pre hooked up to the scopes to get the sound and match he is after.

My Lp-3a is an upgrade of a 2013 LP-2 so it uses 9 pin tubes. I little different than the current production using oktals. The biggest difference to the 27 is the amount of Gain. The Lp-3a can be barn burner. Much of the 27's clarity is still there but it can really tear the shingles off. I plan to keep them both.

As for a web site and specs, doubt it. Dennis is retired and doing this for fun. He changes things constantly with his latest ideas and inspirations. Specs and websites could never keep up. I suggest contacting him again if he has not gotten back to you. I get the feeling his inbox is always pretty full and if he did not reply right away it can get lost in the shuffle. With some more info from you he can steer you in the right direction and even tailor one of his current units to your needs. Many here have customized units though the stock items on eBay are outstanding in their own right.

[pstrisik]

Originally Posted by BearCityUSA

Peter,

I do recall your "4 way" system and yes I think this DH unit is attempting something similar. Filling in the ends of the audible spectrum so to speak.

I inquired with Dennis and he said to go ahead and post this FOR ALL.

As to exactly what DH rigged up as the Contour Network. He has a 1.0mh inductor, a 75 ohm (5W), a 20 Ohm (5W), and a 4 mfd capacitor all wired in parallel. As I said before, Dennis specifically refers to this as a Contour Network.

"Just a short note … the network I slung together is called a contour network. Not to be confused with a notch filter. The contour network shelves a band of frequencies while letting frequencies below and above the design attenuation frequencies come through at the nominal input level."

Per Rosco's post there may be argument that the addition of the CAP makes this a Notch Filter. I will not be arguing this with a man with 60+ years experience. DH refers to it as a Contour Network (CN) so I will be from now on as well.

With a flurry of emails last week regarding this CN Dennis offered this:

"Have a look at a 1st order 6 dB crossover with a center frequency of 2K. 2K is where the human ear is most sensitive."

www.apicsllc.com/apics/Misc/filter2.html#first

Use 8 Ohms for both driver values and 2k hz to follow this:

"The cap is 10 MFD and the inductor is .6 mH and simply double the speaker impedance .. in this case 8 ohms [for the resistor]. Soooooooo, 1/2 the cap = 5 MFD/ double the inductor 1.2 mH and double the impedance of the speaker in use 8 ohms x 2 = 16 ohms.."

"The method for calculating the contour network is one half the capacitance … twice the inductance … and twice the speaker impedance. Therefore, to be more precise than the network I clouged together would be a 5 MFD cap, a 1.2 mH inductor and a 16 ohm resistor. This is a center frequency of 2K. Lower the resistor and the shelf is shallower"

So the values of the one DH "cloughed together" stated above (4 mfd, 1.0 mh, 16 Ohm) was with spare parts. These calculated values (5 mfd, 1.2mh, 16 ohm) are more appropriate for what he was attempting to accomplish. I am planning to order up some additional resistors to test a "shallower" shelf as well. I have read somewhere that using two 10W resistors in parallel works better than one. Dissipates heat better than a single. DH used the 75 Ohm and the 20 Ohm to get 16 ohm combined. I am not sure if that was intentional or if he was just scrounging parts.

Here is a cool website where you can see what this CN does to the signal. The "shelf" effect is pretty clear.

www.mh-audio.nl/parallelnotchfilter.asp

As for the crossover he sketched out for the additional tweeter. He suggested a 6 Ohm resistor in series with a 3 mfd cap. "If to bold try a 10 Ohm resistor instead." The tweeter was the Morel 378. Incidentally the same used in the Inspire speakers he and Allen (Analog Addict) designed.

For you Peter, and Rosco, and Beowulf,... Do you think this would be something to post over on AudioCircle? I do not want to start an argument or imply there is an improvement to Louis' speakers on his owner's threads,... but if others may want to play around and find a better synergy to their system, maybe... Your thoughts are welcome.

Scott

Thanks Scott! Quite a bit to digest. I may try the filter (CN) as Dennis designed it and see what I get with the SAMs alone. I don't know if I would use it along with the supplemental woofers and tweeters. Just playing and learning.

As far as posting on AC, Randy already started a thread - no replies to his post though. But you could email Louis directly and get his take on it. My guess is there might be a few that would be interested and may try it out, but most wouldn't take it on and/or wouldn't see the need.

[Rosco65]

Thanks for the reply Scott. I won't argue semantics with Dennis. I suppose that a notch filter is type of contour filter.

The filter you described shows a 9.5dB peak attenuation. It looks like the filter is flattening the response beginning at 700hz or so and bringing it back in over 10khz. That's one hell of a "BBC Dip".

I started a thread on AC. I'm not sure how Dennis would feel about the CN. He is generally pretty open to experimentation, though I wouldn't expect him to join in on the discussion.

I think a filter like this would be perfect in nearfield use and/or use when listening levels are lower. It is effectively a loudness filter. It would be interesting to compare this speaker-level filter with Bottlehead's "The Fix".

[Wgarcia]

Heat…the heat…normal?

[Analog Addict]

Originally Posted by Wgarcia

Heat…the heat…normal?

It's called a "Fire Bottle" for a reason. If you use the proper tubes and one of the transformers shorts out, catches fire, or melts its guts out, take pictures and contact Dennis. If it makes you nervous, get a small fan....

[BearCityUSA]

Originally Posted by Wgarcia

Heat…the heat…normal?

I may be wrong but trany temps as high as 250F are acceptable. My PSE runs significantly hotter than my KT and those tranys get to 130-140F. Helps keep me warm in the winter. If you can still touch them they should be fine.