Hello All! I have a 1960's Silvertone stereo hiFi with 4 6BQ5's(2 per side)I run my TV/DVD/VCR/TAPE etc. through it,but first into a Marantz Equalizer.I crank the bass frequencies all the way up and it sounds amazing but the speakers can't handle it at higher volume.Can I place a 4 ohm subwoofer in series with the 8 ohm speaker which will make it 12 ohms or will this stress the tubes or transformer.Or could I place 2 4 ohm subwoofers in parallel and then in series with the 8 ohm speakers which would make 10 ohms. In other words does the impedance have to be exactly 8 ohms or can you go up or down a few ohms without ruining the tubes etc??I want to build a couple huge vented speaker enclosures that will produce the 16 to 100 Hz frequencies without distortion.This stereo is actually quite loud for about 15 watts per side.I recently watched a Fred Astaire/Ginger Rogers DVD "Let's Dance" and the music sounded amazing and punchy with the bass cranked up!Love it!!

:Hello All! I have a 1960's Silvertone stereo hiFi with 4 6BQ5's(2 per side)I run my TV/DVD/VCR/TAPE etc. through it,but first into a Marantz Equalizer.I crank the bass frequencies all the way up and it sounds amazing but the speakers can't handle it at higher volume.Can I place a 4 ohm subwoofer in series with the 8 ohm speaker which will make it 12 ohms or will this stress the tubes or transformer.Or could I place 2 4 ohm subwoofers in parallel and then in series with the 8 ohm speakers which would make 10 ohms. In other words does the impedance have to be exactly 8 ohms or can you go up or down a few ohms without ruining the tubes etc??I want to build a couple huge vented speaker enclosures that will produce the 16 to 100 Hz frequencies without distortion.This stereo is actually quite loud for about 15 watts per side.I recently watched a Fred Astaire/Ginger Rogers DVD "Let's Dance" and the music sounded amazing and punchy with the bass cranked up!Love it!!
:Whoops! Movie was "Shall we Dance"

Inaccurate impedances make for less than optimum matching and efficiency. However, it shouldn't do damage with a low power amplifier like this.

Going way up in impedance can damage the screen grids, as they'd be taking most of the current instead of the plate, but you have to go up to like 100 ohms to do this.

Shorting the output transformer secondary won't damage a small amplifier like this, but might blow out a really powerful one.

...So yeah, you have some room to play with. Decreasing impedance is much more of a critical issue with transistors, as they can be overloaded.

T.

:Hello All! I have a 1960's Silvertone stereo hiFi with 4 6BQ5's(2 per side)I run my TV/DVD/VCR/TAPE etc. through it,but first into a Marantz Equalizer.I crank the bass frequencies all the way up and it sounds amazing but the speakers can't handle it at higher volume.Can I place a 4 ohm subwoofer in series with the 8 ohm speaker which will make it 12 ohms or will this stress the tubes or transformer.Or could I place 2 4 ohm subwoofers in parallel and then in series with the 8 ohm speakers which would make 10 ohms. In other words does the impedance have to be exactly 8 ohms or can you go up or down a few ohms without ruining the tubes etc??I want to build a couple huge vented speaker enclosures that will produce the 16 to 100 Hz frequencies without distortion.This stereo is actually quite loud for about 15 watts per side.I recently watched a Fred Astaire/Ginger Rogers DVD "Let's Dance" and the music sounded amazing and punchy with the bass cranked up!Love it!!
:
Bob Z

:Hello All! I have a 1960's Silvertone stereo hiFi with 4 6BQ5's(2 per side)I run my TV/DVD/VCR/TAPE etc. through it,but first into a Marantz Equalizer.I crank the bass frequencies all the way up and it sounds amazing but the speakers can't handle it at higher volume.Can I place a 4 ohm subwoofer in series with the 8 ohm speaker which will make it 12 ohms or will this stress the tubes or transformer.Or could I place 2 4 ohm subwoofers in parallel and then in series with the 8 ohm speakers which would make 10 ohms. In other words does the impedance have to be exactly 8 ohms or can you go up or down a few ohms without ruining the tubes etc??I want to build a couple huge vented speaker enclosures that will produce the 16 to 100 Hz frequencies without distortion.This stereo is actually quite loud for about 15 watts per side.I recently watched a Fred Astaire/Ginger Rogers DVD "Let's Dance" and the music sounded amazing and punchy with the bass cranked up!Love it!!

Hi Chris-
I spent years hooking up series and parallel speaker systems. Usually this was to add speakers in other locations. The good thing is that tubes are REALLY forgiving. With transistor amplifiers, especially with a floating ground, some type matching transformer arraingement was required.
So- can you connect your speakers in series-parallel as long as you don't go below the rated output of the amplifier? Yes
Will this give you the results you are looking for? I don't think so- for the following reasons- Without some type of crossover the subwoofer is still going to be seeing all of the frequencies of the other speakers. Unless there is a crossover inside the subwoofer, it will be just like another speaker. Also, as you have already noticed, it takes A LOT more energy to reproduce low frequencies. You can't get more output from your amp than you are already using. I second the recommendation to get an external powered subwoofer. I don't remember your amp, but it would be nice if it has a pre-amp output. That way the volume of the sub would be consistant with the volume of the amp. If not, you'll have to use a tape, or line, out. There are some excellent subs for sale on eBay and Amazon. I bought a cheap little Yamaha for my bedroom surround system and was amazed at the result.
I hope this helps,
Terry
:

I think that an extra subwoofer would increase the bass ideally, without robbing power from the hi-fi, but 15 watts should be enough to get plenty of bass from the speakers already within the set. Is there something wrong with them? Perhaps change the woofers to better ones of the same impedance. Does the unit itself have a crossover for the speakers? How are the electrolytic capacitors, if any? Feeding the woofers through chokes and the tweeters through capacitors will assure maximum efficiency in audio distribution. Appropriate values must be chosen so that the crossover doesn't create any unnatural peaks or valleys.

A very simple crossover is to simply feed the tweeter through an electrolytic of your preferred size. This will feed the tweeter only treble, and shunt quite a bit of treble around the woofer, but more ideal isolation is would be to add a suitable choke to the woofer. There are books that explain values and ideal frequencies in detail.

I can tell you that all of my radios with about 10 watts of p-p output (6V6, 6K6, 6F6, 45, etc.) have more than enough bass--enough to make the neighbors complain, unless you really want to crank the thing up to deafening levels, though you can get the same result by sitting closer to the radio.

T.

:I think that an extra subwoofer would increase the bass ideally, without robbing power from the hi-fi, but 15 watts should be enough to get plenty of bass from the speakers already within the set. Is there something wrong with them? Perhaps change the woofers to better ones of the same impedance. Does the unit itself have a crossover for the speakers? How are the electrolytic capacitors, if any? Feeding the woofers through chokes and the tweeters through capacitors will assure maximum efficiency in audio distribution. Appropriate values must be chosen so that the crossover doesn't create any unnatural peaks or valleys.
:
:A very simple crossover is to simply feed the tweeter through an electrolytic of your preferred size. This will feed the tweeter only treble, and shunt quite a bit of treble around the woofer, but more ideal isolation is would be to add a suitable choke to the woofer. There are books that explain values and ideal frequencies in detail.
:
:I can tell you that all of my radios with about 10 watts of p-p output (6V6, 6K6, 6F6, 45, etc.) have more than enough bass--enough to make the neighbors complain, unless you really want to crank the thing up to deafening levels, though you can get the same result by sitting closer to the radio.

The enclosure doesn't amplify. It simply prevents negative feedback between the front and the back of the cone, and allows the speaker to work most efficiently at moving all of the air in the room in a uniform manner.

T.

::I think that an extra subwoofer would increase the bass ideally, without robbing power from the hi-fi, but 15 watts should be enough to get plenty of bass from the speakers already within the set. Is there something wrong with them? Perhaps change the woofers to better ones of the same impedance. Does the unit itself have a crossover for the speakers? How are the electrolytic capacitors, if any? Feeding the woofers through chokes and the tweeters through capacitors will assure maximum efficiency in audio distribution. Appropriate values must be chosen so that the crossover doesn't create any unnatural peaks or valleys.
::
::A very simple crossover is to simply feed the tweeter through an electrolytic of your preferred size. This will feed the tweeter only treble, and shunt quite a bit of treble around the woofer, but more ideal isolation is would be to add a suitable choke to the woofer. There are books that explain values and ideal frequencies in detail.
::
::I can tell you that all of my radios with about 10 watts of p-p output (6V6, 6K6, 6F6, 45, etc.) have more than enough bass--enough to make the neighbors complain, unless you really want to crank the thing up to deafening levels, though you can get the same result by sitting closer to the radio.
:

:::I think that an extra subwoofer would increase the bass ideally, without robbing power from the hi-fi, but 15 watts should be enough to get plenty of bass from the speakers already within the set. Is there something wrong with them? Perhaps change the woofers to better ones of the same impedance. Does the unit itself have a crossover for the speakers? How are the electrolytic capacitors, if any? Feeding the woofers through chokes and the tweeters through capacitors will assure maximum efficiency in audio distribution. Appropriate values must be chosen so that the crossover doesn't create any unnatural peaks or valleys.
:::
:::A very simple crossover is to simply feed the tweeter through an electrolytic of your preferred size. This will feed the tweeter only treble, and shunt quite a bit of treble around the woofer, but more ideal isolation is would be to add a suitable choke to the woofer. There are books that explain values and ideal frequencies in detail.
:::
:::I can tell you that all of my radios with about 10 watts of p-p output (6V6, 6K6, 6F6, 45, etc.) have more than enough bass--enough to make the neighbors complain, unless you really want to crank the thing up to deafening levels, though you can get the same result by sitting closer to the radio.
:
:Like I said in the beginning, I've installed many systems, Including A LOT of home theater systems. I actually have two subwoofers in my living room, one in my bedroom, and my landlord laughed when I showed him one I'm hooking up in my bathroom. (You have to understand I have a small one bedroom apartment, not a large house) There's only one way you're going to get a lot of bass, more power! A 100 watt powered 10" subwoofer is going to work better than a 15" 30 watt speaker, especially if part of that power is powering the other speakers. It's a problem of diminishing returns. No matter how many 10" or 12" or 15" speakers you hook up to your amplifier, you still only have "X" amount of power in watts. Sure, if you want to drive your amp into distortion you'll have more power, but the cost of fried tweeters will soon eat up the difference in how much you'd pay for a sub. Consider yourself lucky. Back in the "day", having a powered subwoofer required a separate amp, active crossover and speaker cabinet. Now, for $60 on Amazon, (usually with free shipping), you can REALLY rattle the windows.
::
:

:Hello All! I have a 1960's Silvertone stereo hiFi with 4 6BQ5's(2 per side)I run my TV/DVD/VCR/TAPE etc. through it,but first into a Marantz Equalizer.I crank the bass frequencies all the way up and it sounds amazing but the speakers can't handle it at higher volume.Can I place a 4 ohm subwoofer in series with the 8 ohm speaker which will make it 12 ohms or will this stress the tubes or transformer.Or could I place 2 4 ohm subwoofers in parallel and then in series with the 8 ohm speakers which would make 10 ohms. In other words does the impedance have to be exactly 8 ohms or can you go up or down a few ohms without ruining the tubes etc??I want to build a couple huge vented speaker enclosures that will produce the 16 to 100 Hz frequencies without distortion.This stereo is actually quite loud for about 15 watts per side.I recently watched a Fred Astaire/Ginger Rogers DVD "Let's Dance" and the music sounded amazing and punchy with the bass cranked up!Love it!!
:
If you have a scope see if it is the amplifier that is distorting at high volume with bass turned up or the speaker. My guess would be the amplifier.
15 watts is loud at midrange, but if you are playing loud enough for your neighbors to hear it may not be enough for the bass.
Bob Z