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Old 21st January 2013, 09:54 AM   #1
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Default Fullrange Diy speakers for LM1875 amp

Hi!!
New member from Spain, first post here!

I recently built a stereo LM1875 based chipamp. Nothing special, the same circuit like the one in the chip's datasheet with a couple of modifications.

I'm looking for a speaker kit that would be a good match with this kind of amp. Around $500 or cheaper would be great. There are lots of possibilities out there, and I don't have enough experience to know which speaker design suits better.
Dimensions are a big concern :S I would need the cabinet to be smaller or around 40x25x30 cm

All types of music are to be reproduced with the amp, so speakers should be quite versatile, and there's no possibility to add a subwoofer in the system.

Thank you very much!!!
Congratulations contributing in such a good forum.

Kind regards,
Francisco Perez
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Old 21st January 2013, 10:04 AM   #2
xrk971 is offline xrk971  United States
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The smallish cabinet dimensions and all around use would seem to suggest an onken type enclosure or a folded MLTL for listening to wide range of genres. $500 is a pretty nice budget in diy, I don't think you will find yourself component limited. Welcome on board!
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Old 21st January 2013, 10:42 AM   #3
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Not anywhere near your budget, but these are huge value for the dollar, and can produce bottom end. They are really closer in performance than the price would suggest, the EL70s came from China vis North America so have a lot mor shipping embedded into them.

CHP-70 Gen1 (pair) - RumoH - Caps, coils and speakers

CSS EL70 (pair) - RumoH - Caps, coils and speakers

Alpair 7.3 and Alpair 6.2p would also be candidates.

dave
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Old 21st January 2013, 01:34 PM   #4
IG81 is offline IG81  Canada
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I like the Fostex FF225WK, which should do well in a reflex enclosure of ~30L. It'll need a super-tweeter, the affordable FT17H can do OK with a 1F cap. If you really need to spend all the budget, get a nice ribbon.

IG
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Old 21st January 2013, 02:28 PM   #5
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Ah ah
Nanook's beard is growing

A fullrange speaker should reproduce the entire audio range
Such speaker don't exist - at least for emotionally recreating the
sound as the original (venue)
The subwoofer serves for this purpose - since a dedicated unit
works better than a one-size-fits-all -
For reproducing the treble, the speaker needs to be light and little -
it is related to the wavelenght of the frequency...and the cycles that
are very intense. Not that a sub has not intense cycles..
Whatever...
3 is the magic number !
But having 3 speakers each having its own band to play, a divider network is required, and that adds more power to the total. It means that the voltage drop at amplifier's output would be much more than having a single driver...
Well,it depends
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Old 21st January 2013, 03:00 PM   #6
Nanook is offline Nanook  Canada
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Default the growing beard....fullrange or single driver fullrange?

Quote:
Originally Posted by picowallspeaker View Post
Ah ah
Nanook's beard is growing

A fullrange speaker should reproduce the entire audio range
Such speaker don't exist - at least for emotionally recreating the
sound as the original (venue)
The subwoofer serves for this purpose - since a dedicated unit
works better than a one-size-fits-all -
For reproducing the treble, the speaker needs to be light and little -
it is related to the wavelenght of the frequency...and the cycles that
are very intense. Not that a sub has not intense cycles..
Whatever...
3 is the magic number !
But having 3 speakers each having its own band to play, a divider network is required, and that adds more power to the total. It means that the voltage drop at amplifier's output would be much more than having a single driver...
Well,it depends
pico: I'm sure you can feel my migraine coming on...

FranciscoPerez:If wanting a single driver fullrange solution there are many choices. I have used planet10's modified MA CHR-70 drivers in his Onken style boxes to very good effect with almost any amp I have tried (numerous T-amps both large output and small, large-ish solid state, a low powered Stasis receiver, small tubes...) and none have failed to impress. Although only apparently 86 dB sensitive, they present an easy load. I have not found them wanting for bass (or myself).

A passive crossover converts about 1/2 the power supplied to it as heat and alters phase. So the MAs need to be considered against speakers with at least 3dB more sensitivity than they have. At 20-25 watts/channel (typical of LM1875 designs) and a low damping factor, the amp is very suited to single driver fullrange use. I am confident the modified MAs would be a great match, but other fullrangers that require much less electrical damping and are more sensitive such as various Fostex drivers (and others) should be considered.

Having said this,if bass headroom and greater bass depth is an issue one can use a good powered sub (whether commercial or DIY) or preferably 2 operating as a stereo pair. Dave has the "FAST" designs which are essentially as I have suggested, powered stereo pair (sub) woofers.

If you have the physical space consider a large-ish OB design, such as the Stereo Kingdom "Tube Heaven" design made popular by the JE Labs implementation. With these , as a minimum, a fairly large fullrange driver is required. I've used 10" diameter vintage instrument speakers with a 3dB/octave crossover and a salvaged tweeter mounted co-axially to very good effect. The critical thing is that these OBs are 35-1/2" (W) X 31-1/2" (H) X 10" (D), which can physically dominate a room very easily.
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Last edited by Nanook; 21st January 2013 at 03:04 PM.
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Old 21st January 2013, 08:28 PM   #7
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Oh sorry Stew
That smilie hurts me too
Quote:
Originally Posted by Nanook View Post
pico: I'm sure you can feel my migraine coming on...
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Old 22nd January 2013, 12:52 PM   #8
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Wow!! That's a lot of information! Thank you all very much!!!

I'm investigating a little bit all the different choices you gave me and let's see what I end up building!!!

Your help is much appreciated!!
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Old 23rd January 2013, 04:04 PM   #9
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Hi IG81!
I've read good reviews of the Fostex FF225WK, and the 30L size cabinet is ok.
I'd probably go with that!! Thank you very much!!

About the supertweeter, I find the FT17H good priced so would probably use that too.
Where are we supposed to place the supertweeter ? Inside the cabinet or outside it.
I've seen some designs where the horn tweeter goes outside the enclosure.

As you can see, I'm quite unexperienced with all these,
Sorry if my questions seem too obvious! Any info regarding this type of design, speaker damping etc would be great!!

As said, I'm giving your suggestion a try, hope I like those speakers!!
Thank you all very much!!
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