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In Reply to: RE: Depends on the main speakers posted by Tre' on April 15, 2017 at 07:41:37
You are absolutely correct.
Low frequencies are a huge amplifier current draw. Whenever we can take that load off the mains amp, things get better.
And, to an earlier point, filtering out the low frequencies from a mains "woofer" which isn't up to the task, allows that driver to perform better (more linearly) in its "good" range.
This isn't rocket science: Who here would even consider having a tweeter try to reproduce 300 Hz?!
:)
Follow Ups:
Ok, I appreciate the knowledge and responses (thanks) but to help me understand, are you guys talking about an in-line filter on the amplifier input, or something between the amp and the speaker? Are these available commercially, or am I better off constructing it myself.
The amps are beasts (Class A monos at 300/600 wpc into 8/4 ohms) but this is a new set-up for me (compared to running full-range speakers) so I am interested in anything that will further improve the bass.
to keep the low bass out of the main amp and therefore out of the main speakers.
As a purest, I can't take a line stage crossover in line with the mids and highs but just a high quality cap does wonders.
The filter slope is shallow (only 6db per octave) but it really helps a lot.
I built a 12db per octave Sullen-Key OpAmp based low pass filter to go between the woofer amp and the JBL 2231s (no where near as harmful to low frequencies) but just use one cap per channel as a high pass filter to keep the low bass out of the main amp.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
80Hz at 4 ohms high pass filter. I assume I could wire this directly in line with (only) the LF binding posts and perhaps place it inside the speakers just after the binding posts.
What does the coil do?
If I wanted to reduce the high pass frequency to something like 40 or 60Hz at 4 ohms, could I simply increase the capacitor size or would I need to do something with the coil too? I could use a higher quality cap if that would make a difference since everything from the high pass frequency to the speaker's crossover at 360 Hz will pass through the filter. The specified 250 wpc limit for the filter is only half what the mfg specifies for the speakers so could I increase this with a higher quality capacitor or would the coil need to be different? The schematic is available from linked website.
Thanks for any help.
Ok, so two options, a capacitor between amp and speakers (to augment the existing crossovers?) or a more active approach between the preamp and the amp as shown in Kingshead's post below.
Like you Tre', I would prefer not having anything in the path with the mid/high frequencies. I am however interested in the approach of placing a capacitor between the main amp and speaker that will only affect the low frequencies in my bi-wired set-up. Are you are talking about a capacitor placed between the pos and neg terminals (sort of like a zobel network without the resistor), or in-line capacitors? Additional LR5 measurement information and specifications are provided in the linked review.
The manufacturer's specs indicate the frequency response of my LR5s is 40Hz-22kHz, +/-2dB and, from the measurement graph below, it appears the low frequencies begin to drop off at about 60Hz. Even with this limited frequency response, the speakers are relatively inefficient at 86dB/2.83V/m, probably due in-part to the sealed box design.
Could you direct me to where I could find more specific guidelines to the placement and appropriate value of the capacitor you recommend?
The thing is, that ECU was designed by the manufacturer to work with the Modulus setup, but I'm sure the Modulus sub and its partnering control unit would work great with just about any speaker.
I have other subs though, and although nowhere in the same league (at 8% of the cost of the modulus sub) the setup I've settled on works very well. It's only in direct comparison to the Infinity that you realize they are what they are.
Pictured are a pair of inexpensive Dayton sub1200's being used as speaker stands. Setting them up this way in stereo their sum is greater than the parts would imply. Instead of sounding like a great pair of speakers with a killer sub, the presentation is more akin to Heresys on steroids, THEY JUST SOUND BIGGER.
Does this imply the Modulus system would be improved with a second sub? All I can say is Heeeeeeelllllllll yaaaaaaaaaaaa.
A cap between the main amp and the main speakers will not help the main amp and a cap that big won't sound good.
A cap between the preamp and the main amp would be a small, high quality film cap and it would help both the amp and the speaker.
Sorry for creating confusion.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
This is the ECU for the Infinity sub, notice the variable phase control, and the rear mounted dip switches for the high pass filter, it's connected between the preamp and power amp. Just a few of the features that make this servo sub so musical and easy to integrate.
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