I tested the Dayton Audio DTA-100LF amp at home with the companion stereo amp this weekend.
Speakers used were a three way I built using the Dayton Audio 8" classic series woofer with a midrange and tweeter and a Cerwin Vega 15" 4 ohm driver with cloth surround in a 3 CU FT sealed cabinet.
Everything integrated perfectly and honestly I had never heard that CV woofer sound so good being used as a makeshift sub and I didn't need the Dayton Audio amp turned up above a little under halfway on the gain control. Crossover frequency of both amps was set to 75Hz.
I then tried it at work with the Sony Xplod and I cannot get the sub to integrate at all.
I noticed an issue when I fed a sinewave to the system at the crossover frequency.
There's of course a null when I have the gain and phase set right which is to be expected with the mains and sub being out of phase.
I also noticed that I can adjust the phase control and it sounds like the sub integrates with one speaker but not the other and when adjusted the other way it integrates with the other speaker but not the one.
I figure that's a placement or phase issue, however with the Dayton Audio 100 watt plate amp, an Adcom GFA-545II for the mains and a Kicker 18 dB/octave two way active crossover, it sounded like the sub was nearly perfectly integrated with the mains. Maybe there was some sort of phase shift going on in that setup that made the sub integrate better?
It was recommended for me to try this driver for the sub
https://www.parts-express.com/GRS-1...-Excursion-Subwoofer-4-Ohm-292-818?quantity=1
however if I just get a driver without solving the phase issue, I'll just have the same problem only with a different driver.
Speakers used were a three way I built using the Dayton Audio 8" classic series woofer with a midrange and tweeter and a Cerwin Vega 15" 4 ohm driver with cloth surround in a 3 CU FT sealed cabinet.
Everything integrated perfectly and honestly I had never heard that CV woofer sound so good being used as a makeshift sub and I didn't need the Dayton Audio amp turned up above a little under halfway on the gain control. Crossover frequency of both amps was set to 75Hz.
I then tried it at work with the Sony Xplod and I cannot get the sub to integrate at all.
I noticed an issue when I fed a sinewave to the system at the crossover frequency.
There's of course a null when I have the gain and phase set right which is to be expected with the mains and sub being out of phase.
I also noticed that I can adjust the phase control and it sounds like the sub integrates with one speaker but not the other and when adjusted the other way it integrates with the other speaker but not the one.
I figure that's a placement or phase issue, however with the Dayton Audio 100 watt plate amp, an Adcom GFA-545II for the mains and a Kicker 18 dB/octave two way active crossover, it sounded like the sub was nearly perfectly integrated with the mains. Maybe there was some sort of phase shift going on in that setup that made the sub integrate better?
It was recommended for me to try this driver for the sub
https://www.parts-express.com/GRS-1...-Excursion-Subwoofer-4-Ohm-292-818?quantity=1
however if I just get a driver without solving the phase issue, I'll just have the same problem only with a different driver.
I turned the sub 90 degrees so that it faces to the left under my desk and it seems to integrate much better.
Both mains are connected properly.
That's the first thing I checked and everything's wired properly.
EDIT:
Just tried the sub turned to where the driver faces the rear of the desk and it integrates even better to the point where I no longer hear the sub.
Now given the GRS sub is only $54.98 I may go ahead and try it and if it don't sound as good as the Xplod, I can use it somewhere else maybe in a larger cabinet.
Both mains are connected properly.
That's the first thing I checked and everything's wired properly.
EDIT:
Just tried the sub turned to where the driver faces the rear of the desk and it integrates even better to the point where I no longer hear the sub.
Now given the GRS sub is only $54.98 I may go ahead and try it and if it don't sound as good as the Xplod, I can use it somewhere else maybe in a larger cabinet.
Last edited:
Each "pole" of a crossover filter imparts a 90 degree phase shift:
6 dB/octave=90 degree
12 dB/octave=180 degree
18dB/octave=270 degree
24dB/octave=360 degree
In addition, each driver has an acoustic roll off that may be in the pass band which can add to the phase shift of the crossover filters.
The HP and LP filters may work better with an "underlap", like 60Hz on the sub and 80Hz on the top cabinets.
Your desk is also an acoustic filter, and room modes will boost and cut different frequencies depending on position of the drivers and where you are located. Different songs have different frequency ranges that may be "good" or "bad" depending on where you are listening.
Using pink noise as a source makes it more easy to track down the peaks and nulls.
6 dB/octave=90 degree
12 dB/octave=180 degree
18dB/octave=270 degree
24dB/octave=360 degree
In addition, each driver has an acoustic roll off that may be in the pass band which can add to the phase shift of the crossover filters.
The HP and LP filters may work better with an "underlap", like 60Hz on the sub and 80Hz on the top cabinets.
Your desk is also an acoustic filter, and room modes will boost and cut different frequencies depending on position of the drivers and where you are located. Different songs have different frequency ranges that may be "good" or "bad" depending on where you are listening.
Using pink noise as a source makes it more easy to track down the peaks and nulls.
Since an inductor can introduce up to 90 degrees of frequency dependent phase shift, you would want to use a non-inductive resistive load to test an amplifiers phase shift.
Moving coil speakers all have inductance which varies with frequency.
Worst case phase shift in class D amps are under 90 degrees, and so far above a subwoofer's pass band (a few degrees ~2kHz, 70 degrees at 20kHz) they would have no effect on the response.
At 0 degree (or 360 degrees, one cycle behind) phase difference, two sources add +6dB, at 180 they cancel.
In between, at 90 or 270 degrees difference, there is still a +3dB gain:
Best of luck phase aligning your system!
Art
Moving coil speakers all have inductance which varies with frequency.
Worst case phase shift in class D amps are under 90 degrees, and so far above a subwoofer's pass band (a few degrees ~2kHz, 70 degrees at 20kHz) they would have no effect on the response.
At 0 degree (or 360 degrees, one cycle behind) phase difference, two sources add +6dB, at 180 they cancel.
In between, at 90 or 270 degrees difference, there is still a +3dB gain:
Best of luck phase aligning your system!
Art
I think the main problem is the Xplod sub isn't efficient enough to be properly driven by the amp with its input sensitivity. Either that or the sub amp doesn't have enough gain adjustment.
Now the plate amp I was using which is 100 watts had plenty of gain adjustment and I was able to get the sub loud enough.
I may try that amp again just to see if the sub integrates properly then. It also has a 24 dB/octave low pass crossover.
Now the plate amp I was using which is 100 watts had plenty of gain adjustment and I was able to get the sub loud enough.
I may try that amp again just to see if the sub integrates properly then. It also has a 24 dB/octave low pass crossover.
I discovered one major problem. The variable high pass filter does have decent phase shift even when set full CCW which is off.
So I voided the warranty and proceeded to signal trace the input circuitry and found the input gets summed with two resistors then goes to an inverting OP-AMP stage which then goes to the high pass filter and the output of that goes to the plug that sends the signal to the front board with the crossover, level control and EQ controls on it.
The fix was simple.
I cut the wire to where there's enough so that I can solder it back stock and I soldered a very small gauge wire to the output of the summing stage and that wire which goes to the front board.
I noticed an immediate improvement, but it still wasn't right.
I then remembered my previous speakers had a cap in series with the woofers to form a 6dB/octave high pass as previously I didn't have an active crossover except what was on the plate amp.
I calculated and a 470uF cap would give a -3dB point of 82Hz.
Tried that and disabled the high pass on the stereo amp.
The sub now integrates so much better.
I'll order that sub tomorrow and see3 if it helps.
So I voided the warranty and proceeded to signal trace the input circuitry and found the input gets summed with two resistors then goes to an inverting OP-AMP stage which then goes to the high pass filter and the output of that goes to the plug that sends the signal to the front board with the crossover, level control and EQ controls on it.
The fix was simple.
I cut the wire to where there's enough so that I can solder it back stock and I soldered a very small gauge wire to the output of the summing stage and that wire which goes to the front board.
I noticed an immediate improvement, but it still wasn't right.
I then remembered my previous speakers had a cap in series with the woofers to form a 6dB/octave high pass as previously I didn't have an active crossover except what was on the plate amp.
I calculated and a 470uF cap would give a -3dB point of 82Hz.
Tried that and disabled the high pass on the stereo amp.
The sub now integrates so much better.
I'll order that sub tomorrow and see3 if it helps.
When a driver is put in a sealed box, it's Fs (free air resonance frequency) is raised to Fc (closed box resonant frequency). It's Qts is also raised to Qtc, high values of Qtc cause an underdamped peak in response at Fc, which may be perceived as "boomy", "loose" or "one note", as the response drops steeply below Fc, and "rings" after the signal stops, regardless of amplifier damping control.
A Qtc of 2 will cause a peak of +6dB, values a bit under 1 will have no peak at Fc, and a less steep drop below.
Manufacturers may use inexpensive drivers with weak magnet structures in small cabinets for more "boom for the buck".
A larger sealed cabinet volume will lower the Qtc and the frequency where response starts to drop.
Apparent sealed cabinet volume can be increased by ~15% by adding damping material like dacron or fiberglass, though too much stuffing will reduce apparent volume.
The problem was that I was used to how the sub sounded with the extra space taken up by the plate amp.
Odds are if I had used something to take up as much space as the plate amp did, the sub would have integrated better.
That said it took listening to the sub yesterday with the caps used on the mains as the only high pass for me to get used to how the sub now sounds and today I tried the crossovers in the amps without the caps used for a high pass and I realized that the sub was integrating much better than I initially thought it was.
Two things I think are working against me. The heavier cone and stiffer surround given this is a car audio sub.
The GRS sub should have a lighter cone and a not as stiff surround which should make it better.
The driver will be here Tuesday so I'll take the box home and put the new driver in and see how well it sounds at work Wednesday.
Also the box being thinner doesn't help things so once I get the money I'll see if I can find a 1 CU FT sealed box for a 10" driver.
Odds are if I had used something to take up as much space as the plate amp did, the sub would have integrated better.
That said it took listening to the sub yesterday with the caps used on the mains as the only high pass for me to get used to how the sub now sounds and today I tried the crossovers in the amps without the caps used for a high pass and I realized that the sub was integrating much better than I initially thought it was.
Two things I think are working against me. The heavier cone and stiffer surround given this is a car audio sub.
The GRS sub should have a lighter cone and a not as stiff surround which should make it better.
The driver will be here Tuesday so I'll take the box home and put the new driver in and see how well it sounds at work Wednesday.
Also the box being thinner doesn't help things so once I get the money I'll see if I can find a 1 CU FT sealed box for a 10" driver.
I got the sub finished tonight.
Am testing it with the Dayton Audio 100 watt plate amp.
At first I thought the sub wasn't doing much until I realized I was only hearing the bass and not the sub in much the same way as it was when I was testing those two Dayton Audio amps with my mains at home and the CV woofer.
I'm looking at the sub, I know the sub is working as I can see the cone moving, but I do not hear the bass coming from the sub at all. It integrates as well as the four bucket subs in my system in the house. When I turn the plate amp off it's just like I turned the bass control down.
I'm simply dumbfounded at how good this sub sounds in the frequency range it can reproduce.
I haven't been this dumbfounded about any speaker except when I got the four bucket subs set up in the house a few years back.
Am testing it with the Dayton Audio 100 watt plate amp.
At first I thought the sub wasn't doing much until I realized I was only hearing the bass and not the sub in much the same way as it was when I was testing those two Dayton Audio amps with my mains at home and the CV woofer.
I'm looking at the sub, I know the sub is working as I can see the cone moving, but I do not hear the bass coming from the sub at all. It integrates as well as the four bucket subs in my system in the house. When I turn the plate amp off it's just like I turned the bass control down.
I'm simply dumbfounded at how good this sub sounds in the frequency range it can reproduce.
I haven't been this dumbfounded about any speaker except when I got the four bucket subs set up in the house a few years back.
