Lack of gain?

[ThorstenL]

Konnichiwa,

And so the old 'compromise' issue rears its ugly head again!

You could add the old dreaded "tonecontrols" to your system....

;-)

And another point, some CD's sound better and others worse. I suppose that being single, I could have two or three systems in different rooms for the various types of music I listen to!

Or use something like a Behringer EQ to change the sound according to taste....

BTW T, is it OK to play around with the values in that EQ circuit (within limits of course!)?

Sure. The capacitors determine the turnover frequencies, the one to ground becomes large in value to make the "lift" start at lower frequencies and smaller to start at higher frequencies. The Capacitor in parallel to the 12k Resistor becomes larger to make the HF lift start at lower frequencies and smaller to make it start at higher frequencies. The ratio between the resistors determines the amount of LF/HF lift, currently set to be around 6db maximum.

I'd suggest keeping the resistors fixed and experimenting and making the resistor switchable in steps of 0.5/1/2 (can be done using center neutral toggles).

Sayonara

 

[Nuuk]

Sure. The capacitors determine the turnover frequencies, the one to ground becomes large in value to make the "lift" start at lower frequencies and smaller to start at higher frequencies. The Capacitor in parallel to the 12k Resistor becomes larger to make the HF lift start at lower frequencies and smaller to make it start at higher frequencies. The ratio between the resistors determines the amount of LF/HF lift, currently set to be around 6db maximum.

And thank you once again T. That will save me a bit of research

 

[carlosfm]

Uncontrolled or slow bass usually means the amp is not man enough to drive the speakers, badly positioned speakers (near walls) or badly designed speakers.
In your case Nuuk, you just added a small bass lift.
Reposition your speakers or close the bass reflex port.

 

[Nuuk]

Reposition your speakers or close the bass reflex port.

Thanks Carlos - where do I find the port?

An externally hosted image should be here but it was not working when we last tested it.

 

[ronc]

Well you could cut a port near the bottom, advantages are, the OB is lighter by the amount of material removed, it gives something for the cat to crawl in and out of, you can look thru the hole for things you have dropped on the floor on the opposite side................uuuuuu i cant think of any more!!!!!!
ron

 

[carlosfm]

Thanks Carlos - where do I find the port?

An externally hosted image should be here but it was not working when we last tested it.

Is that a Motorola piezo tweeter?
I love those, with a good crossover.

Nuuk, why are you using that filter?
Did you feel lack of bass?
Isn't that woofer too big for a two way speaker?
Those tweeters shoud be crossed at around 5 to 6khz, they are very sensitive in the midband, it becomes nasty.
With that woofer and tweeter, it sould be a 3-way speaker.
I'm talking generically, of course, as I don't know your speakers.

 

[Nuuk]

Hi Carlos,

The Goodmans 201's are very good 'full-range' units and I was using them with the Motorola tweeters crossed over at 16K.

The beauty of the big drivers is that you can keep any crossover out of the 75-4Khz range.

I did find that on some types of music I could do with a bit more at the bottom end, hence I am trying the EQ kindly suggested by T.

Ron, would I need one cat or two if I cut holes in the baffles? If I found that I had more bass with the cats blocking the holes would I be in trouble for nailing them in there?

And does one breed of cat sound better than the others? I have a feline that you may be able to help me here!

 

[ronc]

While doing a scientific study on the aperodic loading of bass ports with cats i happened to notice that long hair cats had a much more profound effect on the impedance loading of the driver. Using SWAG (scientific wild *** guess) the theory is the longer hair causes a greater diffusion of the exiting pressure and a greater partical density.
NOTE! No cats were harmed during this study, however i did use up a large box of band-aids on myself.
ron

 

[GregGC]

While doing a scientific study on the aperodic loading of bass ports with cats i happened to notice that long hair cats had a much more profound effect on the impedance loading of the driver. Using SWAG (scientific wild *** guess) the theory is the longer hair causes a greater diffusion of the exiting pressure and a greater partical density.
NOTE! No cats were harmed during this study, however i did use up a large box of band-aids on myself.
ron

 

[Nuuk]

Ron, you make me feel so inadequate, not having an engineering background like your good self!

 

[ronc]

I did go to Texas A&M, i am proud to be an aggee,sorry,agie,sorry,agye,sorry..............proud to have gone to Texas A&M.
ron

In other news,i have gone to dual mono blocks with the pre in the middle. All using hammond alum cabs and am mounting all 3 cabs on a 1.5" thick (thats 35mm to yall euro dudes) wooden base and beveling the
edges at a 45 deg. angle then mounting 1.5"l x 1" dia. hard Cr. brass spikes to the bottom. I am painting all the cabs with heat resistant flat black paint and baking them to harden the coating (have to use the oven for something). Will post pics when finished. Gotta finish a set of mono blocks first as well as a set of monster horns for the Fostex Fe-168e sigmas.
ron

 

[carlosfm]

Nuuk,
Well... full-range drivers usually have difficculty on the frequency extremes.
For a sealed box, it seams to me that your big driver needs more volume, a bigger box.
You can try to add a bass reflex port.
Bass may become a little slower, but then Ron can send you some cats.

BTW why not use an old driver as a passive radiator?
Ah, forget it.

 

[Nuuk]

Carlos - it's an open baffle!

 

[carlosfm]

Carlos - it's an open baffle!

Then WHY DIDN'T YOU SHOW THE BACK?

Close the back door, man.

 

[Nuuk]

Then WHY DIDN'T YOU SHOW THE BACK?

Because I only had a picture of the front and side

 

[Nuuk]

OK chaps, I replaced VBIGC with OPA627BIGC so I could take a look inside the former.

And what did I find? The transformer for the valve circuit (not heaters) is putting out 27 volts on one side but only 5 volts on the other. No wonder it didn't sound right!

So can anybody tell me what is happening here. I have measured the voltages with and without the valve circuit connected. And the transformer was putting out the correct voltages when I put it in!

Suggestions/advice please.

 

[ofb]

that couldn't be anything other than a short in the winding, could it?

 

[Nuuk]

that couldn't be anything other than a short in the winding, could it?

Not unless they are putting things in transformers that I don't know about!

BUT the big question is what would have caused it? The transformer in question was not clamped down in the usual way so there should be no question that the windings could have been damaged.

 

[Ropie]

So are you saying that the problem has mysteriously righted itself? How are the V levels this morning?

 

[Nuuk]

Well, I was taking the transformer out for a closer physical examination when I noticed that one of the secondary wires going in to a connecting terminal block was loose.

I have put it back in the terminal block and now have 27-0-27 AC as expected.

I am surprised that the buffer worked at all!

Lesson - the biggest electronics mysteries are often down to something very simple.