Subwoofer for 2-Channel

Early B.

If you have a 2-channel audio system and connect the speakers to the subwoofer (the Polk method), then use the subwoofer's crossover and set it at say, 80 Hz, will the full signal still be sent to the speakers or will the amp only send signals greater than 80 Hz. to the speakers?

Thanks.

VR3

Amp sends a full range signal - (still using all its got)

Your sub will send 80hz on up to the spooks, 80hz on down it will hog to itself.

Basically you're running your speakers on small while running your amp on large. Its an oxymoron - but I like the way it sounds over a LFE cable.

adam2434

That depends on if the sub has a high pass filter on the speaker outs. Some do, some don't. At one time I had a Velodyne that had a selectable 80/100 Hz high pass filter that could be applied to the speaker or line level outs.

If the sub does not have a high pass filter, the speakers will run full range and you would adjust the low pass to blend with the natural roll off of the speakers.

Some subs, like the inexpensive Dayton's have a fixed high pass at 125 Hz, which is too high unless you have really small speakers. My point is that even if the sub has a high pass filter, it may not be ideal for your speakers.

Early B.

OK, next question -- will running speaker cables through a plate amp (or separate amp) color the sound? It seems to me that it would, since the signal has to pass through a bunch of additional electronics, especially if those electronics contain marginal quality components like those found in most plate amps. Is this correct?

John K.

EB, as Adam pointed out, unless the sub has a separate high-pass filter on its high-level speaker outputs(the majority of subs don't)the feed to the speakers is simply a full range pass-through. The internal sub crossover rolls off the high-end response of the sub driver; it doesn't affect the speakers, even when they're connected through the sub. So, the speaker cables aren't actually "run through" the electronics of the sub amp; it's simply wiring, and any "marginal quality"(unlikely)in the sub amp would have no effect on the speakers.

Tour2ma

Yup... and if the sub does have a separate high-pass filter, it's basically just an outboard cross-over. So while the signal to the mains would see additional electronic components, whether that degrades the signal is up to your ears.

Only other comment is that the filters are not barriers that block the entire signal above or below the set point, but, as JK put it, they "roll off" the signal.

adam2434

Another example of how you can get a high pass filter on your speakers:

Most current Velodynes (except the lower end models) have a fixed 80 Hz filter on the line level (RCA) outs, but do not have speaker level outs. In this case, you could run RCA cables from a preamp to the line level ins on the sub, then run RCA cables from the sub line level outs (high pass filtered at 80 Hz) to your amp. In this case, your amp and speakers will only see a rolled-off 80 Hz and above.

Then, you experiment with the sub's low pass filter and gain to get the best blend with your speakers.

I have a friend who does this with some tube gear, Vandersteen speakers, and a Velodyne sub. He loves the way it sounds and says that it improved the sound of his Vandersteens - probably because his tube amp is no longer driving the low bass.

adam2434

Building on the line level scenario above, if a particular sub did not have a high pass filter on the line level outs, FMODS are another way to achieve a high pass filter for your speakers. The FMODS would be plugged into the amp that's driving the speakers and would be connected to the line level outs from the sub.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=266-272

MLZ

For my 2-channel system with a receiver without bass management, I hooked up my main speakers as "A"s and the subfoofer to the "B" outs (until i got my HK 3380 which has a sub out)

Early B.

adam2434 wrote:

Building on the line level scenario above, if a particular sub did not have a high pass filter on the line level outs, FMODS are another way to achieve a high pass filter for your speakers. The FMODS would be plugged into the amp that's driving the speakers and would be connected to the line level outs from the sub.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=266-272

I assume this method will work only if the speakers are connected to the sub, correct? Is there another way to use the FMODS on an integrated amp without attaching the speakers to the plate amp of a subwoofer? I have a set of pre-outs, but no "main in."

adam2434

Early B. wrote:

I assume this method will work only if the speakers are connected to the sub, correct? Is there another way to use the FMODS on an integrated amp without attaching the speakers to the plate amp of a subwoofer? I have a set of pre-outs, but no "main in."

Actually, the 2 line level approaches I described don't require a speaker level connection to the sub at all.

They require you to put the sub "between" the preamp and amp, which, unfortunately, doesn't work with an integrated amp, unless it has a processor or adapter loop.

You should still be able to connect the sub to your preouts and dial in the low pass and gain to blend with your speakers. However, your speakers would be running full range, with no high pass filter.

There are speaker level "bass blockers", which are simple high pass filters typically used in car audio. However, I haven't heard of them being used for home audio.

Do you really want a high pass filter on the speakers, or is blending the sub at their natural roll-off OK?

Early B.

adam2434 wrote:

Do you really want a high pass filter on the speakers, or is blending the sub at their natural roll-off OK?

My bookshelf speakers roll off at around 40 Hz. I'd like the option of having them roll off at 80 Hz with a sub picking up everything else beneath it. Theoretically, (I think) this will allow the main amp to provide more power to the speakers and clean up the midrange because the drivers aren't pulling double duty and trying to inefficiently produce bass and midrange at the same time. Sounds like my setup doesn't allow for that. Thanks for your responses.

adam2434

Yeah, your best bet would be to find a sub with speaker level ins and outs with a 80 Hz highpass on the outs. As I mentioned above, some of the current, higher-end Velodynes have this feature, as do many of their discontinued models (my older VA-1012 did).

Good luck.

Early B.

Adam --

Just ran across this very interesting quote from a Soundstage review of my speakers (Taylo Reference Monitors) which answers a few of my questions about using a sub with a high pass filter ...

Later on in my listening sessions I added a Velodyne ULD-15 subwoofer to the system. The ULD-15 gives you no choice but to insert an 85Hz high-pass filter in the path of the speakers -- unless you have dual outputs on your preamp, as does my Class

adam2434

Regarding that Soundstage review, I think the amp quality/size/current is probably a factor - systems with lesser amps may benefit more from the highpass than better amps that have more than enough current and headroom to maintain control at high volumes.

I'm sure it is speaker dependent too, with better speakers being able to keep composure running full range at high volumes.

The thing that's always bothered me about running speakers full range with a sub is how low you need to set the lowpass. Say your speakers are flat to 40 Hz; you would probably want to set the sub's lowpass to somewhere in the 40-50 Hz range to minimize overlap. Most music doesn't have much content below 40 Hz, so it seems like the sub is being underutilized and is also not relieving the amp and speakers of any bass duty.

Early B.

adam2434 wrote:

The thing that's always bothered me about running speakers full range with a sub is how low you need to set the lowpass. Say your speakers are flat to 40 Hz; you would probably want to set the sub's lowpass to somewhere in the 40-50 Hz range to minimize overlap. Most music doesn't have much content below 40 Hz, so it seems like the sub is being underutilized and is also not relieving the amp and speakers of any bass duty.

Yep, that's precisely my dilemma. For 95% of the music I listen to, a sub is not necessary. It's that damn 5% where I'd love to have one. But is it worth the expense? For me, not at this time. Hell, I like my speakers so much, it may be more advantageous to trade up to Tyler Acoustics floorstanders. Hmmmm.;)

Tour2ma

adam2434 wrote:

Most music doesn't have much content below 40 Hz...

I'd say 30 Hz is a better figure. Unless we're talking chuch organs or synth's, there is precious little below 30 Hz in recordings, but there is an ever growing content in the 30 to 40 Hz range in recording since the 60's.



Click the pic for a nice read...

Early B.

I listen mostly to jazz. For me it's not worth the expense at this time to purchase a subwoofer to cover the spectrum of 40Hz - 30Hz. (In other words, I talked myself out of getting one.) Not sure if there's enough info between these ranges for the types of music I listen to. Tour -- do you know how low the upright bass goes?

One of my heaviest bass CDs is Santana's Supernatural. I was impressed with the bass output on my speakers with this CD. However, some of my oldies funk stuff could definitely benefit from a sub, but I rarely play those tunes.

adam2434

Pretty sure an open low E is around 41 Hz.

John K.

Here's a table of fundamental frequencies of musical instruments. Yes, the low E on the bass is at 41.2Hz. Pipe organ isn't included in the table and some can do 16Hz, or very rarely, 8Hz.

RuSsMaN

28-32 cycles, 3db down, you're golden for music.

Tour2ma

Nice link, JK. I had a page on discussing bass drum and upright bass, but few other instruments. Somewhat surprised to see that of orchestral instruments the Contrabassoon goes the deepest with the harp not far behind.

Of course roll out a piano and you have a new leader in the clubhouse... A0 - 27.5 Hz...

EB,
As you already know from the above replies, for jazz you're good to go.