LM3875 for bass only.

brommermartin · 21st February 2010, 02:46 PM

I have build the LM3875 inverting with e88cc buffer including the big powersupply from chipamp.com.
How can i improve the bass response further , the bass speakers are 16 Ohm.
I will build a regulated powersupply with the LM338 hope that this will make it sound a little bit better.

Any surgestions

Minion · 21st February 2010, 03:53 PM

Well You could add a Bass Boost feature or an EQ .......

brommermartin · 21st February 2010, 04:00 PM

What i really want to improve is the tightness of the bass response.

infinia · 21st February 2010, 04:06 PM

Quote:

Originally Posted by brommermartin

How can i improve the bass response further , the bass speakers are 16 Ohm.
I will build a regulated powersupply with the LM338 hope that this will make it sound a little bit better.

Any surgestions

Sorry 16 ohm speakers do not produce the most power from these chips.
So to compensate you have to provide the chip amp with nearly the max supply voltage. If you build a Vreg then the regulator needs to drop more supply voltage, giving the chip less V and power from a existing transformer!. So No... not the answer you hoped for.

petemoore · 21st February 2010, 04:11 PM

It' is either a performance which the rig is capable of but isn't being utilized yet.
Or there's a weak link in the rig which prevents the performance you desire.
You said speakers, what is the effeciency might be the question, my experience is that if I like the sound of a speaker and it's relativley effecient, simply doubling what I have here is an option to consider if the alternative is to attempt to make an amp or speaker ''surpass itsel''f.
Speaker/Cabinet choice, then amp [we all know what's the best alternative here], or amps, what's in front of the amp...
Preamp, here's a good place to see if the aforementioned links can handle making more of what you want, just the way it is.
If the links were here, the end of the chain [speaker or source] is where suspicion and planning would begin.

brommermartin · 21st February 2010, 04:47 PM

For the regulated powersupply i have a 250va 2x30vac transformer for each channel.
The effeciency of the bass units are 99.362 dbspl , the units are 15 inch from my Oris 150 horns.

infinia · 21st February 2010, 04:52 PM

Contrary to some peoples views, Power amps don't change bass speakers sound too much. They provide V, I, and damping factor. Take a closer look at the speaker/box design to see if the chip amp as designed can handle the job at hand esp at max SPL. Otherwise as some suggested, EQ can give you much more variability in bass sounds.

Tightness is somewhat a vague term but I attribute that to an amps control or damping factor. Increase feedback to provide higher damping factor by decreasing overall CL gain. Sometimes less amp conrol is really what's needed to give a bass speaker a little more bass. Insert a smallish resistor in series to change speakers box Q.

bobodioulasso · 21st February 2010, 06:28 PM

Bass reproduction needs power. As you are using a 16 ohm speaker, the best could be to build another 3875 ( output only) and bridge them.
The load would be so seen as a 8 ohm one.

Redshift187 · 21st February 2010, 10:07 PM

What schematic does your LM3875 circuit use?

woody · 21st February 2010, 10:42 PM

What type speakers are they horns, open baffel, infinite baffel ect. Were they designed to be run from an amplifier with a low damping factor?

21st February 2010, 02:46 PM	#1
brommermartin diyAudio Member Join Date: Sep 2009	LM3875 for bass only. I have build the LM3875 inverting with e88cc buffer including the big powersupply from chipamp.com. How can i improve the bass response further , the bass speakers are 16 Ohm. I will build a regulated powersupply with the LM338 hope that this will make it sound a little bit better. Any surgestions

21st February 2010, 04:52 PM	#7
infinia diyAudio Member Join Date: May 2005 Location: Californication	Contrary to some peoples views, Power amps don't change bass speakers sound too much. They provide V, I, and damping factor. Take a closer look at the speaker/box design to see if the chip amp as designed can handle the job at hand esp at max SPL. Otherwise as some suggested, EQ can give you much more variability in bass sounds. Tightness is somewhat a vague term but I attribute that to an amps control or damping factor. Increase feedback to provide higher damping factor by decreasing overall CL gain. Sometimes less amp conrol is really what's needed to give a bass speaker a little more bass. Insert a smallish resistor in series to change speakers box Q. __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

21st February 2010, 10:07 PM	#9
Redshift187 diyAudio Member Join Date: Aug 2008	What schematic does your LM3875 circuit use? __________________ Tyler

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21st February 2010, 03:53 PM	#2
Minion diyAudio Member Join Date: May 2006	Well You could add a Bass Boost feature or an EQ .......

21st February 2010, 04:00 PM	#3
brommermartin diyAudio Member Join Date: Sep 2009	What i really want to improve is the tightness of the bass response.

21st February 2010, 04:11 PM	#5
petemoore diyAudio Member Join Date: Jan 2010	It' is either a performance which the rig is capable of but isn't being utilized yet. Or there's a weak link in the rig which prevents the performance you desire. You said speakers, what is the effeciency might be the question, my experience is that if I like the sound of a speaker and it's relativley effecient, simply doubling what I have here is an option to consider if the alternative is to attempt to make an amp or speaker ''surpass itsel''f. Speaker/Cabinet choice, then amp [we all know what's the best alternative here], or amps, what's in front of the amp... Preamp, here's a good place to see if the aforementioned links can handle making more of what you want, just the way it is. If the links were here, the end of the chain [speaker or source] is where suspicion and planning would begin.

21st February 2010, 04:47 PM	#6
brommermartin diyAudio Member Join Date: Sep 2009	For the regulated powersupply i have a 250va 2x30vac transformer for each channel. The effeciency of the bass units are 99.362 dbspl , the units are 15 inch from my Oris 150 horns.

21st February 2010, 06:28 PM	#8
bobodioulasso diyAudio Member Join Date: May 2008	Bass reproduction needs power. As you are using a 16 ohm speaker, the best could be to build another 3875 ( output only) and bridge them. The load would be so seen as a 8 ohm one.

21st February 2010, 10:42 PM	#10
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	What type speakers are they horns, open baffel, infinite baffel ect. Were they designed to be run from an amplifier with a low damping factor?

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