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Old 16th November 2011, 02:55 PM   #11
tinitus is offline tinitus  Europe
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make it slim and taller
with a couple of wheels it will much easier to pull around
instead of carrying it
but if there are stairs, not so good

but building this stuff is definately not easy

not sure, but with a plateamp mounted in the speaker, maybe you can drive it with a small combo, from headphone out
then you have a small practice amp, and a powered speaker cab
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Old 16th November 2011, 06:30 PM   #12
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The plan is to limit the bass independently (ie, low pass into a compressor-limiter) of the rest of the mix, instead of brickwalling the output at 200Hz as ZT themselves have done.

See last page here http://www.ztamplifiers.com/pdf/ZT_A...Whitepaper.pdf - I'm hoping for better LF performance at moderate levels than this, but for loud low frequencies, more speaker will be required.

Chris
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Old 16th November 2011, 07:14 PM   #13
Nanook is offline Nanook  Canada
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Default Chris: Ok, now "clean" or "dirty"?

One of the things that can eat power is running clean. Dirty is essentially overdriving the output of the guitar? (I think, I am no guitarist). Also what bandwidth is typical of your instrument? (electric? bass? acoustic?). The Eminence Tonkerlite might be something to consider:

Nominal Basket Diameter 12", 304.8mm
Nominal Impedance* 8 ohms
Power Rating**
Watts 125W
Music Program N/A
Resonance 109Hz
Usable Frequency Range 70Hz - 5.5kHz
Sensitivity*** 101dB
Magnet Weight 4 oz.

There may be other candidates, I just chose something that had good sensitivity, that could handle the power ...(the Little Buddy 10" looks pretty good, but rated to 50W ). Don't ask me about tone, because that is an individual thing.

So here's something that should work well for you and is (perhaps) something you should consider. Get a more efficient 8" (or whatever size driver you have or slightly larger), and swap it into your existing practice amp (if good, but power limited). Have a look at some 8" "fullrangers" , they may just be what you need. A pair of Wil Burro "Betsy" drivers in an open backed cabinet or OB could be relatively inexpensive..then add a 100W/ch amp (kits are out there for "gainclones", class D and class T amps. that should be suitable. I have built and love the the 41Hz kits, but there are others out there).



Sub'ing a more efficient loudspeaker driver into your existing combo will allow you to see if 116 dB@1W@1m (40W into a 100 dB driver) is suitable. You can always use the new driver in a project amp if not suitable for installation into your combo, thus still economizing (and benefiting from any "tweaks" that you may have already done). This mod to your combo amp should be able to be done rather inexpensively and should be done so that it is reversible.

Nigel is absolutely correct. There is a fine line to be had regarding size and the ability to move air and efficiency. Surprisingly, a larger driver can be more efficient than a smaller one (and often is). Speakers that I use on my desktop are only 83dB@1W@1m, but they are less than 1m away...what I listen to in my living room are single drivers (usually), but their efficiency is nothing to get exicited about: 85dB, driven by a good, robust (McCormack) 100w/ch stereo amp, and 109 db is plenty loud enough for me.
tinitus has a good idea. If you must make an combo amp, perhaps 2 100db drivers (mounted closely together) driven by a 100W/ch, 2 channel amp in a tall cabinet that can be dragged around with castors (or oversize wheels if going up stairs) on the rear could be an effective solution. Why don't the others help out dragging the stuff more?

Eminence drivers are very good, but get yourself a guitar speaker type from them
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Old 16th November 2011, 08:06 PM   #14
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Originally Posted by chris661 View Post
instead of brickwalling the output at 200Hz as ZT themselves have done.
That agrees with what I suggested, you can get MUCH higher power handling from a driver with mid-range only and no bass content - and of course the small sealed enclosure further limits the bass capability, and helps to 'restrain' cone movement.

It looks a nice little thing, though I suspect it's far too limited for many users - but could be great for some players and styles of playing.

I suspect you're really want to see one 'used in anger' at a gig, and probably do extensive testing before you bought one - I'm presuming they aren't cheap?.
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Old 17th November 2011, 07:53 AM   #15
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Hi Nigel,

The limited bass response doesn't bother me much: the combo I use has a low Q speaker in an open backed cabinet, and the tone controls (set flat) have bass cut and treble boost. The upshot is that the LF output is mostly harmonics.
ZZ Top have reputedly used the ZT Lunchbox at gigs, though they were televised so stage volume was low. There are those (on the forum I was reading) that suspected the little amps couldn't possibly be making all that sound, and others that said the amps were great and nothing more would be needed.
The amplifiers themselves are a little over 250 for the little one, 350 for the bigger one (single 12", reputed to hit 131dB). I could try one at the music shop, but not at its proper volume.


Nanook,
While I appreciate your suggestions, the idea of a larger speaker is going away from the original design intentions somewhat: this is an amplifier that must be small and portable. As a teenager on a budget, the idea of replacing the speaker to see what happens isn't really an option. Eminence (and other) guitar speakers come in around 70 here, which is more than I'd be willing to spend just to try it.
This really is a no expense expended project - I even have a suitable linear PSU here.

Chris
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Old 17th November 2011, 02:26 PM   #16
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by chris661 View Post

Eminence (and other) guitar speakers come in around 70 here, which is more than I'd be willing to spend just to try it.
you can get a 100watt Beyma 10" fullrange at 35GBP
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Old 18th November 2011, 08:25 PM   #17
Nanook is offline Nanook  Canada
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Default small, loud, cheap...and in the UK

Quote:
Originally Posted by chris661 View Post
Nanook,
While I appreciate your suggestions, the idea of a larger speaker is going away from the original design intentions somewhat: this is an amplifier that must be small and portable. As a teenager on a budget, the idea of replacing the speaker to see what happens isn't really an option. Eminence (and other) guitar speakers come in around 70 here, which is more than I'd be willing to spend just to try it. This really is a no expense expended project - I even have a suitable linear PSU here.
Chris
So finally the complete situation is stated. Thanks. So currently you have a 40 W single channel amp. And all you want is something to play louder, not necessarily better, and with low budget. (I am assuming you can afford a 50) My suggestion was for a good driver that could be loud enough ....

See if you can borrow a friend's amp or one from a music store. Beg, borrow or steal a SPL meter or see if one of the music store guys will come out to a practice with an amp and SPL meter. Then you can find out how loud you really need it and then go from there.

After that help can be had that will address the better defined project parameters and a reasonable budget can be created. It may be that the best alternative is to retrofit a more efficient driver into your existing combination amp.
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Old 18th November 2011, 08:33 PM   #18
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Originally Posted by Nanook View Post
See if you can borrow a friend's amp or one from a music store. Beg, borrow or steal a SPL meter or see if one of the music store guys will come out to a practice with an amp and SPL meter. Then you can find out how loud you really need it and then go from there.
If you need an SPL meter to tell if you're loud enough?, then perhaps music isn't for you?
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Old 18th November 2011, 11:13 PM   #19
Nanook is offline Nanook  Canada
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Default need an SPL ...

Nigel: I suggested this so that chris661 could know what his design parameters would be and what 110dB, 120dB, (@1W@1m) actually sounds like.
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Old 23rd November 2011, 08:31 PM   #20
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Originally Posted by Nanook View Post
So finally the complete situation is stated.
I'm sorry - I wasn't aware I had been vague. Wasn't intentional.

As a loudness reference, we've gone loud enough to make my ears distort. This was in a room of around 6' by 12', with an acoustic drum kit, another guitarist, bassist, and singer.
My amp was clipping square - 111dB plus the additional loudness of all the harmonics. I read somewhere that a square wave of equal peak voltage to a sine wave has twice the power. So could we say 114dB?

I'm still searching for a suitable power amplifier - I've got (for nowt) a 24v SMPS. Weighs next to nothing, so I'd like to continue the switch-mode theme with a similar power amplifier. This would keep weight down and efficiency up (you've heard it all before).

Assuming bridged operation, 48v peak output = 34v RMS = 144w (using V^2/R) into 8ohm.

This would be enough to get over 114dB (just about) clean.
I suspect the difficulty is that I want to keep up with a bigger amplifier that's being used with distortion, while keeping my own sound clean.

Chris
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