Probably this is a naive question, but is there a device like this Rolls SX95 but that takes a speaker level input signal rather than a line level input?
I want to use a subwoofer (non-powered, but yet to be built) with a pair of DML speakers using my old Sherwood 4109 receiver as the amp.
I'd like to be able to crossover from the sub to the DMLs around 100 Hz and have some independent control of the subwoofer output level. Having phase control and a few options for crossover frequency would be nice, but maybe not really necessary. Does such a device exist commercially? Could it be built cheaply?
Thanks,
Eric
https://www.amazon.com/ROLLS-SX95-A...ocphy=9007449&hvtargid=pla-663619777110&psc=1
I want to use a subwoofer (non-powered, but yet to be built) with a pair of DML speakers using my old Sherwood 4109 receiver as the amp.
I'd like to be able to crossover from the sub to the DMLs around 100 Hz and have some independent control of the subwoofer output level. Having phase control and a few options for crossover frequency would be nice, but maybe not really necessary. Does such a device exist commercially? Could it be built cheaply?
Thanks,
Eric
https://www.amazon.com/ROLLS-SX95-A...ocphy=9007449&hvtargid=pla-663619777110&psc=1
You can use some resistors make a 10:1 voltage divider circuit that accept speaker level signal to feed the Rolls SX95.
https://www.epanorama.net/circuits/speaker_to_line.html
But be careful some amplifier negative speaker terminals are not grounded (i.e. BTL and some class D amplifiers). It's better to use a transformer isolated speaker to line level converter like the PAC:
PAC SNI-35 Variable LOC Line Out Converter
BTW, most subwoofer amplifier in the market comes with speaker level input and all the adjustment features that you want.
https://www.epanorama.net/circuits/speaker_to_line.html
But be careful some amplifier negative speaker terminals are not grounded (i.e. BTL and some class D amplifiers). It's better to use a transformer isolated speaker to line level converter like the PAC:
PAC SNI-35 Variable LOC Line Out Converter
BTW, most subwoofer amplifier in the market comes with speaker level input and all the adjustment features that you want.
chrisng,
Thanks for your reply.
If I use the voltage divider idea, then wouldn't I have to re-amplify the output of the Rolls?
What I was trying to avoid was buying any other amplifier. I was hoping to buy a subwoofer driver, put it in a box, and drive both the sub and speakers with the only amplification being that already supplied by the receiver's built in amp. Just need a way to split/crossover and level control the already amplified signal. Perhaps this isn't "a thing".
Yes, using a sub and separate sub amp (or powered sub) with speaker level inputs is an option I was considering. But again, I was hoping to avoid paying for another amp.
And aren't the "crossovers" they include really just low pass filters on the subwoofer, without any filtering of the left and right speakers? Maybe the same is true of the Rolls unit too?
Thanks,
Eric
Thanks for your reply.
If I use the voltage divider idea, then wouldn't I have to re-amplify the output of the Rolls?
What I was trying to avoid was buying any other amplifier. I was hoping to buy a subwoofer driver, put it in a box, and drive both the sub and speakers with the only amplification being that already supplied by the receiver's built in amp. Just need a way to split/crossover and level control the already amplified signal. Perhaps this isn't "a thing".
Yes, using a sub and separate sub amp (or powered sub) with speaker level inputs is an option I was considering. But again, I was hoping to avoid paying for another amp.
And aren't the "crossovers" they include really just low pass filters on the subwoofer, without any filtering of the left and right speakers? Maybe the same is true of the Rolls unit too?
Thanks,
Eric
rayma,
I suspect you are right. I just want to be sure I'm not missing a simpler (cheaper) way.
The problem is the Sherwood 4109 receiver doesn't has pre-out.
If that's the case, you can try using a low pass filter connect from Sherwood 4109 speaker output to the subwoofer driver input. However, it will not give you any adjustment ability.
100 Hz Low Pass 8 Ohm Crossover
I think a active subwoofer with speaker level input and high pass crossover output for your speakers is an better option.
For example:
Definitive Technology ProSub 800
IT comes with a 80Hz high pass crossover.
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chrisng,
I actually already have a couple of those 100 Hz Low Pass "Crossovers", but they are really just filters (I think). But how would I combine the left and right signals (for the sub)? And where would source for the regular speakers come from? I've played with using the A speakers for the sub and the B speakers for the other speakers, but I have to choose which (L or R) to use for the sub, and the receivers high current protection circuit gets tripped.
That ProSub 800 does look interesting. Where did you see that it has an 80 Hz high pass crossover? I could not find that anywhere.
It's a woofer/passive radiator design I don't see any reference to a port. Does that mean it's a "sealed sub". Or is it a different animal entirely?
My "fallback" idea was just to get a Polk PSW10. Would the ProSub 800 be a lot better than that? It's pretty much the same price. Way more power for sure.
Thanks,
Eric
I've not seen one commercially, but that doesn't mean something close doesn't exist somewhere.
Passive subs were a thing for a while, but when amps and active crossovers got cheaper they fell out of favor.
Assuming you only need to decrease the output of your DMLs something like the following will get you parts of what you're after:
1) fixed passive crossover on dual voice coil subwoofer
2) fixed passive crossovers with L-pads on DMLs (8 ohm L-pads are A LOT easier to find than 4-ohm)
You would not have phase or frequency adjustment, because that's too complex to do reasonably passively at speaker level.
At 80 Hz, 8 ohms, and 6 dB/octave, you need a 16 mH coil for the subwoofer crossover, and you'd need 2 since it's a dual voice coil. Those are typically about $20-50 each if you use an iron core, 16 gauge coil.
If you fudge that up to 85 Hz, you can use a 15 mH coil, and if you're willing to take some extra resistance in the coil, there are some 19 gauge iron core ones that are cheaper. It sounds like that's probably more up your alley.
Last time I tried to order coils, there were supply issues, so some values were hard to get. I don't know if that's still the case.
So you previously tried connecting the sub to left or right channel (but not both) speaker A output and your main left and right to speaker B output, with the 100hz low pass in place in front of your sub, and your receiver went into protection mode? Can you try just running the sub without the speakers connected but with LPF in place and see if the receiver goes into protection mode?
dkfan9
Correct. But it's not a big surprise, I think. Each of the speakers is only 4 ohms. IIRC the manual for the receiver says it wants 8 ohm speakers for one set only, and 16 ohm for and an B together.
But it works fine with a pair of 4 ohm speakers, but not the combo with the sub on one of the other outputs.
I know, really pushing it! That's why I was hoping there was a way to use only the A or B but not both.
Eric
One way to do that is using two subwoofer drivers instead of one. Another way is using a dual voice coil driver, but I don't have experience for that and not sure the result.
Those low pass crossover/filters should connected parallel to speakers, and you need to watch the output level not to trigger the amplifier protection. Therefore I suggest a active sub.
https://www.crutchfield.com/S-N7RviVdhRu1/p_735PSUB8B/Definitive-Technology-ProSub-800-Black.html
Sorry I don't have any experience with Polk PSW10, but from paper, its 50W output seems "light weight" pairing with your 100W receiver. And I not sure it has high-passed speaker connection.
Another subwoofer I know of is the GoldenEar ForceField 3 subwoofer comes with 150Hz high pass output connection.
https://www.crutchfield.com/p_317FF3/GoldenEar-ForceField-3.html?cc=07
IMO, the only way to find out which subwoofer sounds best is to try them in your room. It is fortunate that retailers are provide in home trial program.
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Didn´t read all the answers but if each channel had to feed its own subwoofer, easy peasy, just get the required 100Hz or whatever you choose crossover.
Mind you, 100Hz crossovers need large capacitors and inductors, so not cheap at all.
probably same as getting a power amp board and supply and doing it the right way.
Now if you want to combine "two into one", power amps do not like parallelling outputs AT ALL, even if only at lowest frequencies.
Some kludge might be designed, already rolling some ideas in my mind, but what for?
Definitely expensive.
If your receiver has no preamp out, you can easily attenuate and mix speaker outs to drive a sub amp.
Mind you, 100Hz crossovers need large capacitors and inductors, so not cheap at all.
probably same as getting a power amp board and supply and doing it the right way.
Now if you want to combine "two into one", power amps do not like parallelling outputs AT ALL, even if only at lowest frequencies.
Some kludge might be designed, already rolling some ideas in my mind, but what for?
Definitely expensive.
If your receiver has no preamp out, you can easily attenuate and mix speaker outs to drive a sub amp.
I'd probably try a dual coil subwoofer in a 4th / 6th order bandpass, designed to match the mains as close as possible.
Rob.
Rob.
Two+ problems make a passive sub crossover a bad idea.
1. The sub requires a lot more gain than the rest of the band. So you would have to boost the bass big time. This is aggravated by the fact that woofers are not very efficient, so they need a lot more power and gain. This is the reverse of bi-amping, so for a 100W amp, most of the band is limited to about 10W.
2. Combining 2+ channels is a problem. If you could invert one channel, then you could run the sub in bridge mode. A 1:1 auto transformer can be used to invert one channel but transformers suitable for low frequency are huge.
3. Some people here seem to think a dual voice coil speaker looks like two resistors. No, it's more like two coils on a transformer. Connecting the two coils to two different channels is a bit better than shorting the amps together but not much better.
A summing sub filter is an easy DIY project, but you can buy them ready made, and such comes built into powered subs. If you want to build your own speaker but not the electronics, then an amp like the one in post#2 is the way to go. In the late 1960's I used about 4 resistors and 3 capacitors to make a filter from the speakers of mom's console stereo to a "Knight kit" tube amp that drove a sub that I built in high school. I wrapped it up in electrical tape with cables hanging out. It was something like, a pair of 1K resistors from each channel to a cap about 3.3uF, then a 4.7K to 0.33uF and finally 47K to 33nF and the sub amp (line) input. Each stage is 10x the impedance of the former so that you get a decent 18dB filter. You can change cap values to move the filter frequency, f=1/(2piRC).
1. The sub requires a lot more gain than the rest of the band. So you would have to boost the bass big time. This is aggravated by the fact that woofers are not very efficient, so they need a lot more power and gain. This is the reverse of bi-amping, so for a 100W amp, most of the band is limited to about 10W.
2. Combining 2+ channels is a problem. If you could invert one channel, then you could run the sub in bridge mode. A 1:1 auto transformer can be used to invert one channel but transformers suitable for low frequency are huge.
3. Some people here seem to think a dual voice coil speaker looks like two resistors. No, it's more like two coils on a transformer. Connecting the two coils to two different channels is a bit better than shorting the amps together but not much better.
A summing sub filter is an easy DIY project, but you can buy them ready made, and such comes built into powered subs. If you want to build your own speaker but not the electronics, then an amp like the one in post#2 is the way to go. In the late 1960's I used about 4 resistors and 3 capacitors to make a filter from the speakers of mom's console stereo to a "Knight kit" tube amp that drove a sub that I built in high school. I wrapped it up in electrical tape with cables hanging out. It was something like, a pair of 1K resistors from each channel to a cap about 3.3uF, then a 4.7K to 0.33uF and finally 47K to 33nF and the sub amp (line) input. Each stage is 10x the impedance of the former so that you get a decent 18dB filter. You can change cap values to move the filter frequency, f=1/(2piRC).
Attachments
And some people think companies like Acoustat and many others successfully used single, dual voice coil subs in 2.1 systems, so perhaps they're good enough for someone looking for a low cost/simple solution to a problem.
https://jlaudio.zendesk.com/hc/en-us/articles/204374150-Speaker-Wiring-Tutorial
"dual voice coil woofers were developed so that a subwoofer or center speaker could be driven from the left and right channels of the average home stereo amp/receiver. Since sub-bass frequencies are hard to localize, the dual voice coil subwoofer allowed sub-bass reinforcement within one cabinet and one speaker. This cabinet could be placed inconspicuously in a corner or along a wall of the listening room. The obvious benefits to this are space-efficiency and lower cost than two independent bass cabinets or a larger cabinet with two subs in it. Many popular home subwoofer / satellite speaker systems still use this basic configuration."
https://techtalk.parts-express.com/forum/tech-talk-forum/45171-dual-voice-coils-in-stereo
"The funny thing is that was what they were originally created for, now there's people who say this can't be done. 🙄"
- If this is running your main speakers, you can't do what you want actively. And passive subwoofer crossovers basically suck-I had to redesign an existing product once and found that due to the impedance curves of the subwoofer and woofers, it works poorly.
- If you want to use this as a power amp, that won't work either, because there is no main-in to the power amp. So any signal to the Sherwood won't be controlled by your main volume.
- Unless your main speakers (make? model?) have big woofers, you should be merciful and have a highpass crossover to cut out low bass.
Data point: for five decades I've been running bi-amped and tri-amped; you can put the sub anywhere in the room away from the main speakers without a bit of challenge to stereo localization on any non-trick music provided that your XO is below maybe 130 Hz, the slopes are more than 18dB/8ve, and the sub is pretty good for THD.
Can you achieve that?
B.
Can you achieve that?
B.