I am in the process of building my first low wattage class A amp and so I thought it would be good to also build an efficient pair of speakers to go with it. It's been a long time since I've build speakers and its time to upgrade (really I am looking for any excuse to build stuff).
I came across this design which looks very interesting. Efficient and relatively inexpensive.
Speaker Project - Rockin' It Old School -- 12/31/2013
Other alternatives I've been thinking about:
-ZDT 3.5
-Something fullrange
-Has anyone built those speakers? Impressions?
-How might they compare to the other options?
I came across this design which looks very interesting. Efficient and relatively inexpensive.
Speaker Project - Rockin' It Old School -- 12/31/2013
Other alternatives I've been thinking about:
-ZDT 3.5
-Something fullrange
-Has anyone built those speakers? Impressions?
-How might they compare to the other options?
Attachments
Hi Chatziva good seeing you around!
I haven't studied your links but my 1st impression is that design is low to average eff. it's a numbers game thing! "the gain" is by operating at 4 ohms on the woofer see the resistor pads on the mid range killing real eff.
also investigate 4 ohms on Class A designs
I haven't studied your links but my 1st impression is that design is low to average eff. it's a numbers game thing! "the gain" is by operating at 4 ohms on the woofer see the resistor pads on the mid range killing real eff.
also investigate 4 ohms on Class A designs
Hello Infinia! Nice to see you too!
What do you mean by "the gain is at operating at 4 ohms on the woofer"?
What do you mean by "the gain is at operating at 4 ohms on the woofer"?
^
since most amplifiers hold voltage constant say at 2.8V RMS , when you attach a 4 ohm speaker the power increases by 3 dB over an 8 ohm speaker with equal efficiency. So when looking at speaker sensitivity make sure it is the power you are comparing otherwise its a false eff. gain.
since most amplifiers hold voltage constant say at 2.8V RMS , when you attach a 4 ohm speaker the power increases by 3 dB over an 8 ohm speaker with equal efficiency. So when looking at speaker sensitivity make sure it is the power you are comparing otherwise its a false eff. gain.
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I see. The mid driver has 94db sensitivity and the woofer & tweet 92db so presumably the L-pad only drops 2 db to bring everything to 92db?
I will sim the xo/spk but I think it looks like a predominantly 4 ohm speaker. If so I will get that 3db gain you were talking about.
So overall I think it should be a pretty efficient pair at >92db, no?
I will sim the xo/spk but I think it looks like a predominantly 4 ohm speaker. If so I will get that 3db gain you were talking about.
So overall I think it should be a pretty efficient pair at >92db, no?
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sensitivity is changed by a voltage divider 20LOG(X/(X+Rpad))
where X= impedance of the speaker in parallel with any zobel
so looking at the mid X~8 ohms, 20LOG( 1/2) = - 6dB
so the whole speaker eff can be roughly estimated by reducing the midrange sensitivity downwards by 6 dB. or 94-6 ~88dB
which IMO is decent if the woofer gain is several dB higher for bass to appear. or good reasons for selecting a woofer @4 ohm!
BUT class A is limited by bias currents and may be unhappy to drive a 4 ohm woofer
where X= impedance of the speaker in parallel with any zobel
so looking at the mid X~8 ohms, 20LOG( 1/2) = - 6dB
so the whole speaker eff can be roughly estimated by reducing the midrange sensitivity downwards by 6 dB. or 94-6 ~88dB
which IMO is decent if the woofer gain is several dB higher for bass to appear. or good reasons for selecting a woofer @4 ohm!
BUT class A is limited by bias currents and may be unhappy to drive a 4 ohm woofer
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Chatz, where did you find that crossover? I've never seen one posted for that design before. It does look like a decent low cost rocker project. That woofer is very popular.
David
David
Thank you for the explanation. Just a question, so why would a 4 ohm woofer would be better than a 8 ohm one?
The amp I am building is an M2 clone from Nelson Pass. It should be happy driving 4 ohms.
I just googled it before but seems can't find it now...sorry. I quite like how they look.
because of the sensitivity advantage I explained earlier above and to support BSC on speaker designs. E.g the woofer needs to be from 6 to 4 dB more sensitive to the upper drivers.
Got it thanks! So going back to the original question, I think it's game over for these as they are not perhaps as efficient as I first thought.
Now that's efficiency! The 4π kit particularly with the D&C DE250 & JBL 2226 drivers look sooooooo good!
The Eminence combo with Omega 15'' & PSD2002 also looks nice.
Another cheap combo could be PRV Audio D290PY & 15W800A 15"
I somehow feel that a midrange is needed though in all instances
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