I am hoping to lower the cutoff freq of this crossover. is it possible to only change the large cap to do this or will it affect the entire range? Also what type of crossover is this? I meant to add that the capacitor I can read is the larger one, and its 10mF.
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This is the simplest kind of crossover - woofer is connected directly without any filter, for midrange there is only one capacitor (larger one) as a first order (6 dB/octave) high-pass filter plus one attenuating resistor, and for the tweeter one capacitor (smaller one) as a first order high-pass filter plus one attenuating resistor.
Why do you want to lower the cutoff frequency? On which driver - midrange or tweeter?
Why do you want to lower the cutoff frequency? On which driver - midrange or tweeter?
+1 with the understanding that the manufacturer deemed each needed a cut-off (4) octaves away (-24 dB), so 2000/2^4 = 125 Hz, 5000/2^4 = 3125 Hz, ergo unless only used at low peak power, then short of a lot of testing to find low distortion power limits, best to base your new lower XO points on at least 2nd order lower limits = 2000/2^2 = 500 Hz, 5000/2^2 = 1250 Hz.
It seems it cuts off dramatically at 40Hz. That's above a lot of program material, and these are really old, so its a good idea to replace and fine tune the caps. My mom just gave these speakers to me, and they have been unused for about 20 years.
You cannot lower the frequency response of the lowest octave driver (in this case the woofer) in a speaker by adjusting the crossover components.
You didn't state it explicitly, but it seems you are concerned by the bass extension of the speakers.
First, no speaker has a low cut off frequency, one for which below you won't hear anything. For a closed box, the SPL goes down with a 12dB/octave slope. As an example if the SPL at 60 Hz is 90dB, at 30Hz can be 78dB. The stated cut off frequency can be either where the SPL is down 3 or 6 dB from reference (it doesn't exist a rule for that), and depends entirely on the woofer parameters and the box size.
A 12" woofer in a suitable closed box should have plenty of bass. Play some tones at different frequencies, but keep in mind that bass notes can be "manipulated" by the room, in other words, if you move the speakers or you change position in the room, you can hear differently.
I don't have direct experience on this, but I suspect that a woofer not driven for many years, can have the suspensions hardened, altering the parameters, and thus also the bass behaviour.
Ralf
Hi Ralf,
These speakers are still flexible and really in great shape. I realize that there is no hard cutoff point in any speaker, it is just a coil, and the coil will do its thing even if the acoustics don't support it. I do hear a definite electronic cutoff though, and it is very apparent just below 40, as advertised, so it seems a capacitor is at work. 40 was always too high a point, for 5 string bass, and for the of sound from a double bass. It leaves some music missing a lot down there, especially a lot of classical music. Your observations of the nature of bass are great as bass is my thing, and I deal with all those aspects and more. These old Kenwoods sound great in every other way, so they are keepers, no matter.
JB
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I suspect there is too much mids and highs, overpowering the bass range - very common with those simple crossovers. Try substituting the capacitors with smaller ones, for example instead 10 micro Farads use 4.7 micro Farads capacitor - that should bring down midrange and help bass to pop up. Also, if needed, increase the value of the resistor which is in series with the 10 micro Farad. Then, if the high range is too powerfull, also use half of the current value of capacitor in the tweeter filter.
The amplifier is an Onkyo from 1978 or so. Japanese. I believe it has a deeper frequency response than 40Hz, but I should recheck that.
No need to check the amplifier, it is fine. Eventually replace the 2 big electrolytic capacitors in the power supply.
Well, if the capacitor is not in the speaker, it might be elsewhere? With REW or ARTA and two resistors (for a measuring bridge) you can measure the frequency response of the amp. I wouldn't state a 40+ year old one doesn't need to be checked. There even could be a highpass filter somewhere else in the audio chain (HTPCs with strange Windows audio settings?).
BTW in a lot of (older) recordings of classical works sub-40Hz was highpassed in the vinyl mix, record players don't like that territory. So you even have to check your source material.
Red,
The low-frequency acoustic rolloff of a sealed ("Acoustic Air Suspension") box like your Kenwood JL-776 is typically 12dB per octave, same as a second order electronic or passive crossover.
The JL-776 frequency response claims "40Hz to 20,000Hz", those frequency extremes are likely -6 to -10dB below the average mid-band levels.
The low B is around 31Hz, 1/3 octave below the low E (41Hz). Even if 41Hz was only -5dB as in the response of the Acoustic Research sealed acoustic suspension speaker below, 31Hz would be -11dB. At that low of a frequency, around -5dB will sound only half as loud to your ear. On top of that, because of the way hearing responds, (equal loudness levels) 31Hz actually needs to be another 4-5 dB louder than 41Hz to sound equal in level.
To sound equal to a "conversational" level of 60dB SPL (sound pressure level) at 1000 Hz, 31Hz needs to be around 100dB SPL.
The pair of Kenwood JL-776 woofers might come close to that level at one meter, but would require around a 12dB boost (equalization) at 31Hz to compensate for the roll-off. The Onkyo probably has a "tape monitor" loop that an EQ could be inserted in.
Unfortunately, since the woofers play all the way to past 2000 Hz, if they are boosted to that level, the clarity of the upper range will suffer, the bass will modulate the vocal range, a sound like they are gargling.
If you want to actually hear/feel the fundamentals of the low bass notes clean, you will need to add a subwoofer capable of playing that low at a usable (audible) level.
Art
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It isn't a gradual rolloff; I checked it with a signal generator and it about hits a wall between 40 and 30. These Kenwoods should be a little better down there.
Turntables hate those lows! Classical music has some good info in the sub bass range. I am a professional bassist and have some great speakers that go super low, so I have a lot of ways to test things. An external sub would be an easy fix, and might be the way to go, but I am feeling an electronic impass in the Ken's.
Thanks for good info!