John Curl's Blowtorch preamplifier part II

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Your not designating a cone size for that bass driver Frank? You want something big or something smaller for a mini-monitor or a full size 15" bass driver or even an 18"? I once made a little 3" cone driver that surprised the Sh*t out of me with the bass response but it sure wasn't going to get very loud, had a 3/4" long gap length with a 1/4" length voice-coil. I've been thinking about revisiting that design for a small desktop speaker but increasing the diameter to 4".
 
Any size will do, whatever it takes to get the job done. I note on the drivervault website that the most competent driver as measured using his setup appears to be the AE Speaker IB15,
Anything better around?
I just snagged these for $60.00 from an ex DJ....''Towtallee aaawessome basss mate"

subs - 2.jpg
Aus made 15" Lorantz (JBL 2235 copy) in reasonably cubic enclosure with 3" deep slotted port along bottom edge, no internal damping.
I will use these as speaker stands for the Behringer active 8"' two ways.
Fun times ahead. :cool:

Dan.
 
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Frank,
My take on this is you have two problems with most bass speakers, Either you normally have a short coil in a short gap which means as soon as you push the speaker to have any high excursion the coil is coming out of the gap or you have a long coil in a short gap and the motion is asymmetrical about the resting position due to the way the flux field is uneven on each side of the gap and you also throw so much of the power in the coil away as most of the coil is actually outside the gap. This is a major reason that I went the other way and gave up efficiency to rather have linear motion with a short coil in a long gap, the flux density if consistent during full motion. Of course you still have the uneven restorative function of the suspension but at least you have eliminated one of the non-linear functions with the long gap. Everything is always a trade-off.

Take a look at some of the B&C drivers.
 
Sounds promising ... but I see these measurements here, DIY TC Sounds LMS-5400 18" sealed 100L - Home Theater Forum and Systems - HomeTheaterShack.com, which seem to indicate that below 30Hz the distortion performance tails off.

It's obviously not a trivial exercise to get superclean all the way down, once a bit of level is also required.
My new boxes internal volume (not subtracting woofer volume) is 137L.....internal 630Hx520Wx420D, 17mm good plywood, carpet on the outside. :cool:
No doubt they will require tweaking, but they are a good starting point for proper bottom end, and who could refuse the price ....$60.00 :rofl:

I am running an Edirol UA-25ex USB sound card XLR out feeding the Behringers which have switchable low cut.
I just now confirmed that the Edirol optical out will feed my DEQ2496 which can then feed any stereo amp I feel like trying...no mono bass for me.
The DEQ provides a wealth of processing types to help in getting the subs to have any hope of integrating well....parametric, graphic, dynamics, width, delay etc.

You can get bass cheaply, look on Gumtree classifieds. ;)

Dan.
 
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Frank,
My take on this is you have two problems with most bass speakers, Either you normally have a short coil in a short gap which means as soon as you push the speaker to have any high excursion the coil is coming out of the gap or you have a long coil in a short gap and the motion is asymmetrical about the resting position due to the way the flux field is uneven on each side of the gap and you also throw so much of the power in the coil away as most of the coil is actually outside the gap

Take a look at some of the B&C drivers.

Did that, but didn't really stand out, from any others in what was easily seen. But, looked around a bit more, and this unit looks very promising, Data-Bass.

The distortion measurements indicate that it can plumb to 20Hz frequency levels with no sudden change in characteristics, a good sign,

Data-Bass
 
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You can get bass cheaply, look on Gumtree classifieds. ;)

Dan.
Dan, I appreciate that one can put together very good value for money bass - but I would be coming at it from the quality angle: let's try and make the bass distortion to be as low as reasonably possible, so that only what was on the recording is heard, nothing extra added. I've heard far too much overcooked bass over the years, don't need more of it ...
 
Distortion comes down to cone travel mostly.
In my lounge room environment that has neighbours I'm not looking for 330px-Sensurround_logo.png .
With appropriate power and eq/dsp to match with the B2031's, there should be well ample 20Hz, enough to find room rattles.
I will see how this setup goes during the next week or so.
Maybe they will be acceptable with tweaking, or may progress to different/bigger cabinets and better crossover setup.

Dan.
 
Bass is cheap ....

My 2 cube pioneer box + my 10" tangband + my 200W BJT PA.
And a 17" sewer pipe for tuned port.
Very clear , with almost the same relative SPL <25hz. That 25hz
can rattle any object to the floor within 5 meters any direction.

Some things even fall in the corners of the house (standing waves).
110-115db LF is quite sufficient for a medium size room - movies and
music.

Outside , the tourists might hear what sounds like distant thunder.
Perfect.
OS
 
Did that, but didn't really stand out, from any others in what was easily seen. But, looked around a bit more, and this unit looks very promising, Data-Bass.

The distortion measurements indicate that it can plumb to 20Hz frequency levels with no sudden change in characteristics, a good sign,

Data-Bass

I thought the Dayton 18" ultimax was max. :eek::eek:

That is one hell of a 24". Walk-in closet box with a 300mm port , you
could launch basketballs across the room. tune it to <15hz.

OS
 
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Sounds promising ... but I see these measurements here, DIY TC Sounds LMS-5400 18" sealed 100L - Home Theater Forum and Systems - HomeTheaterShack.com, which seem to indicate that below 30Hz the distortion performance tails off.

It's obviously not a trivial exercise to get superclean all the way down, once a bit of level is also required.

Use two of the 18 inch TC-Sounds in a isobaric or push-pull arrangement to reduce harmonics to very low level. Esp even order.


THx-RNMarsh
 
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Jan, you asked something along the lines of ' what is the group delay at 20Hz associated with a mechanical cartridge/arm resonance having a peak amplitude of +6dB at 10Hz? '. The answer I calculate is c 4.6mS.

At 20Hz in that system, amplitude response of headshell movement to forced stylus motion is c -9dB, phase response c -160 deg.

OK so this is present in the system just because of the mechanical construction*. Now if we add a subsonic hipass at say 10Hz make it 12dB/Oct, how much would that add to the GD?

* That was one of the big advantages I noted with the ELP laser player - no tonearm,cartridge or combined resonance at all of course.

Jan
 
Admitting, once in a while, being wrong would also help. Small things, like the Bybee BS, high open loop bandwidth benefits, the audible effects of wire materials, indiscriminate ceramic capacitors scaremongering, to name a few.

Wide open loop bandwidth is wrong? Pray explain why, I'd really LOVE to know, because for the last 35 years or so some of such amps tended to sound better to me than most of the high GNFB types.
 
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