Subwoofer connection headache..

**David Meek** · 22 March 2005, 08:28 Tuesday

My FSR-15 works just fine without the return loop to the processor. I'd recommend running the B&Ws full range and crossing the sub (using it's internal X-over) just above the lowest functional output of the 703s. Doing it that way will eliminate the mains being constricted by the processor. Do you have an SPL (sound pressure level) meter and test tones? You'll need them to play with the X-over setting to get the smoothest response curve, but we all have to do that. :yesnod: Also, you definitely DON'T need a B&W sub to blend well with your other speakers - don't sweat that. I went with the Velodyne because it sounded better that the other choices at the time and it works very well with my Aerials.

**jclyle** · 22 March 2005, 08:49 Tuesday

Thanks for yoru reply! I will let the 703's run full range, hopefully the Velodyne will be a fast sounding sub, it has a Kevlar reinforced driver so that may help with a faster sound. Are you running a single RCA cable, or a pair of RCA's from your pre-amp? I don't have a pressure meter, but do have access to some test tones to help tweak the room.

**David Meek** · 22 March 2005, 09:00 Tuesday

I'm running L&R connections to the FSR-15.

I'd really recommend getting an SPL. It'll make an amazing amount of difference over what your ears will give you. For the results you'll get, it's a bargain at $30-40. I promise.

**jclyle** · 22 March 2005, 20:06 Tuesday

Originally posted by David Meek

I'm running L&R connections to the FSR-15.

I'd really recommend getting an SPL. It'll make an amazing amount of difference over what your ears will give you. For the results you'll get, it's a bargain at $30-40. I promise.

Where could I find one? Do you have any reccomendations on one to go with?

thanks!
Carter

**junior77blue** · 22 March 2005, 20:11 Tuesday

Radio Shack

They have a digital and analog. I use the analog...no problems.

**bigburner** · 14 June 2005, 20:38 Tuesday

Carter,

So how did you wire up your new sub, and which brand & model did you buy?

I have a Rotel RC-1070 pre-amp with 2 pairs of output RCAs. My dealer suggested wiring my new B&W ASW-750 to the second pair of output RCAs on the pre-amp, in the same way that you describe above. However after much research and experimentation I discovered that this advice is wrong.

I've wired the ASW750 so that the output of the pre-amp goes to the input of the sub, and the output of the sub goes to the input of my RB-1080 power-amp. This enables the high-pass filter on the 750 to limit the frequencies being sent to my B&W CDM9NTs to 80Hz and above (this is pre-set on the 750), thereby taking bass load off the 9NTs. I've set the low-pass filter on the 750 to 80Hz so that the sub only plays 80Hz and below. I've found that this results in the best stereo image because the sub isn't duplicating frequencies being played on the 9NTs. It also takes the base load off the 9NTs, enabling them to play at much higher volume without fear of distortion.

As the 9NTs were the previous model to the 703s (they are very, very similar) this is the approach that I would take in your situation.

**Taito** · 22 June 2005, 22:37 Wednesday

The disadvantage to doing it this way bigburner, is that the signal that goes to your mains is going through additional processing. As the sub would use active crossovers, this likely means the use of 1 or more op-apms per channel, let alone extra cabling. While this setup works for you, I doubt it is ideal for everyone.

The issue of the sub duplicating the mains lower frequencies can be neatly side-stepped by setting the LPF on the sub to approx 40Hz. Yes, your mains will be working a little harder (no harder than they were designed to work), and your sub will be doing less work can seem like a disadvantge (after all, you're paying it to work

), but this way, you get an extra octave of bass from your mains which is perfectly integrated with the higher frequencies.

Having the sub only cover on octave (20-40Hz) also has its advantages. There will be less issues with room modes that covering from 20Hz to 80Hz, and the sub will be able to play louder without it distorting (a balance between sub and speakers must be found).

Having said all of that, both approaches are valid, and Carter, I would recommend that you try both. For the cost of 1 more stereo interconnect, you can be sure that you are getting the best possible upgrade from your new purchase. EDIT: Actually, you wouldn't even need the extra interconnect.

-Ben

**bigburner** · 23 June 2005, 06:24 Thursday

Taito,

Very interesting. I went and checked my ASW750 Owner's Manual and it states quite clearly that the sub should be connected as I've described above. I also downloaded the Owner's Manuals for the ASW850 and the advice is identical. Are you able to post a cut-and-paste from your Owner's Manual or point me to a URL that recommends connecting and tuning a sub the way that you have described?

**Taito** · 23 June 2005, 09:00 Thursday

Bigburner,

I am unable to post a cut-and-paste from my owner's manual, because I have not bought a sub (although I am giving very serious consideration to building one).

Originally posted by bigburner

I have a Rotel RC-1070 pre-amp with 2 pairs of output RCAs. My dealer suggested wiring my new B&W ASW-750 to the second pair of output RCAs on the pre-amp, in the same way that you describe above. However after much research and experimentation I discovered that this advice is wrong.

My suggested method of setup appears to be the same as that of your dealer

Originally posted by David Meek

My FSR-15 works just fine without the return loop to the processor. I'd recommend running the B&Ws full range and crossing the sub (using it's internal X-over) just above the lowest functional output of the 703s. Doing it that way will eliminate the mains being constricted by the processor.

and the same as David uses.

I was not saying that your setup is 'wrong' as you have said of your dealer's advice (which I would not call wrong), but pointing out its disadvantages. Both setups will work.

It may be that B&W recommeds your setup because the majority of stereo preamps do not have 2 sets of stereo outputs (as the 1070 does). Or, that it should be easier to achieve a satisfactory (but not necessarily optimum) result that way.

I hold by my suggested means of setup for the reasons stated in my last post. While I can't display a user's manual that I don't have, I can say that my suggestions are based on a very good understanding of electronics and electronic systems. If your experience tells you that your setup works better for you in your system than my suggestion (and I suggest you try it if you haven't), that's fine. You are welcome to your opinion and can be happy that you have your system setup in a way which most suits you.

Carter, I still urge you to try both approaches and decide which is best for you.

**autio** · 23 June 2005, 10:39 Thursday

http://www.hometheaterhifi.com/volum...rs-9-2002.html check out this link!

**bigburner** · 24 June 2005, 01:53 Friday

1. The ASW750 is the recommended sub for integration with 7-series speakers, i.e. 703s and 704s in a 2.1 configuration.

2. The high-pass filter on the ASW750 is pre-set to 80Hz.

When you combine these facts it means B&W think that 80Hz is the ideal crossover for 703s and 704s in a 2.1 configuration. In other words, you will get the best out of your system if you avoid sending frequencies below 80Hz to your 703/704 speakers. I have faith that the people who design and build these speakers know more about it than I do.

My interpretation of autio's document (thanks for that autio - very informative) supports this view I think, even though it is geared for HT.

I'm pretty new to this, so I'd welcome counter arguments. Perhaps I've misunderstood B&W's intentions??

**Taito** · 24 June 2005, 21:49 Friday

Bigburner, I have recently done a lot of reading on the subject. Your way is very popular with a lot of maufaturers. So, without hooking a sub with speaker-level inputs of a LFE channel, it seems there are two choices:
1) Run the preamp outs to only the sub and run the power amp from the sub's outputs (your way).
2) Run the mains full range, ie. preamp to power amp (not filtered) and preamp to sub.

Either way will have its advantages and disadvantages.
1) Advantages: less work done by mains and power amp for a given volume level. Ensures (more or less) 'cooperative' hand-over of bass duties from mains to sub.
Disadvantages: Additional circuit(s) in signal path for mains -has potential (but will not necessarily) to increase noise floor, add distortions and reduce dynamic range of signal. If sub is not up to the task (B&W sub would be fine), can put too much load on the sub resulting in worse bass overall.

2) Advantages: No additional processing on signal being sent to main speakers, Sub has to cover a narrower frequency range and so will (should) do a better job of that range. Sould be more difficult to detect the location of the sub by listening.
Disadvantages: Can be more difficult to integrate sub with speakers properly, will miss out on advantages of (1).

As with anything audio, there are trade-offs involved with either path.

If you are happy with the way your system sounds, and can't localise the sub (ie. can't point to it by listening to it), Great. It will cost you nothing but time to try both approaches, and I really would like to know which you prefer and what you noticed about the sound of each setup if you have time to try it out at some stage.

Perhaps I jumped in too strongly on the negatives of your setup without looking at the positives. If I offended, I apologise.

Regards, Ben.

**bigburner** · 26 June 2005, 06:58 Sunday

Taito, I am definitely not offended! This is a really interesting subject and I don't believe for one second that I have a monopoly on subwoofer wisdom. Quite the reverse in fact...

My decision to wire my sub up the way I have is linked directly to my reason for purchasing a sub in the first place. My reason is that at higher volumes I just wasn't getting the bass I wanted from my CDM9NT fronts. Also, on one occasion my 9NTs began to clip at high volume. [This was Jon Cleary's "The Absolute Monster Gentlemen" which, although it is a wonderful album, has bass that has been overmixed to an extreme degree.] At that moment I decided to buy a sub.

I have no complaint whatsoever from the 9NTs when played at low to moderate volume. I listen to a lot of music at that volume and they sound very convincing. However they were at risk of not cutting the mustard at party time, and a bloke has his reputation to maintain.

So I really had no choice in order to achieve the objective that I wanted.

During experimentation I didn't notice a lot of difference between the two ways of wiring the sub, although I did NOT wind up the volume until the 9NTs clipped! If the high pass filter on the ASW750 is degrading the signal to the amp in some way then I can't detect it, or my system is not sophisticated enough to show it up.

What I did notice were the dramatic changes to the sound when experimenting with the low pass filter setting on the ASW750. As you would expect, at higher frequencies (110Hz +) the source of the bass became detectable, and the stereo image deteriorated.

After reading your recent posts I tried another experiment. I turned off my amp (to eliminate the fronts) and wound the low pass filter on the sub down to 40Hz, so that I could hear what actually comes through at that frequency. Well I can tell you that on the few tracks I tried there's not a lot. I suspect that HT is quite different (dinosaur footsteps etc). I didn't spend too much time on this experiment because it's not very musically rewarding!

If / when I upgrade my speakers I think that my approach may well change. With more sophisticated fronts it may make more sense to wire up the sub the way that you prefer.

**Taito** · 26 June 2005, 09:22 Sunday

I remember the first time I 'bottomed out' my speakers. Not pleasant... not pleasant at all. Sub aside (as I don't yet have one), our 2ch systems are not so dis-similar. Good choice in electronics BTW :T . I also have the 1070/1080 combo for amplification. My speakers, however, are JM Lab Cobalt 826S's. Yet they too, are a 3-way with the same driver layout as yours (TMWW). (At the same price point as 704's)

I would say it's more a case of B&W's crossover not degrading the signal much than it is your system not being sophisticated enough to hear it (at least I hope so

).

Unless you're dis-satisfied with your system, I can't see the need for you to upgrade for a long time. You have some good kit! As for me, A turntable is likely on the horizon, but that's another story.

Happy listening, Ben

**javis** · 21 July 2005, 08:40 Thursday

bigburner,
I am expecting delivery of a velodyne DD15 next week. I bought it for virtually the same reasons as you described. I have spoken to the velodyne tech on a few occasions who suggests categorically I set it up exactly as you have described for optimal results. I figure they have to know their product and so I will do the same. I beleive I will need to purchase 2 sets of high quality cables that don't come cheap!. Would you agree?

**akhter** · 26 July 2005, 15:52 Tuesday

Originally posted by autio

http://www.hometheaterhifi.com/volum...rs-9-2002.html check out this link!

Great article. Although I never read it anywhere, various experimenting lead me to believe in the configuration of the last line in the article.

Alternatively, setting center and surrounds as "Small", the mains as "Large", subwoofer as "None", and implementing an external two channel crossover to the subwoofer is a valid, and in some situations an advantageous way to go.

**bigburner** · 27 July 2005, 04:33 Wednesday

javis, have you got your new sub yet? You definitely need two sets of cables, but whether they have to be expensive is another question. I'm all for thick copper and gold plated plugs and shielding, but I'm afraid I haven't yet been convinced of the need to sell my first born to pay for them. However, given how passionate some members are about their interconnects, I'm keeping an open mind on this one.

**maddog** · 27 July 2005, 08:16 Wednesday

Originally posted by Taito

Bigburner, I have recently done a lot of reading on the subject. Your way is very popular with a lot of maufaturers. So, without hooking a sub with speaker-level inputs of a LFE channel, it seems there are two choices:
1) Run the preamp outs to only the sub and run the power amp from the sub's outputs (your way).
2) Run the mains full range, ie. preamp to power amp (not filtered) and preamp to sub.

Either way will have its advantages and disadvantages.
1) Advantages: less work done by mains and power amp for a given volume level. Ensures (more or less) 'cooperative' hand-over of bass duties from mains to sub.
Disadvantages: Additional circuit(s) in signal path for mains -has potential (but will not necessarily) to increase noise floor, add distortions and reduce dynamic range of signal. If sub is not up to the task (B&W sub would be fine), can put too much load on the sub resulting in worse bass overall.

I just want to comment on the claim that method (1) can "reduce dynamic range of signal". Every article in a published audio magazine that I have read claims that the opposite is true. Additionally, I have a Rotel RSX 1055 A/V receiver which does the crossover and sends <= 80 Hz to my SVS sub and > 80 Hz to my main speakers, and I will tell you that without a doubt the sound stage is twice as big with far greater dynamic range in the highs in comparison to when I use just the mains without a sub and require them to play the low notes. (I am talking about 2-channel music, not HT here.) Not high-passing the mains defeats the primary advantage of using a sub. Allowing your sub to play just the low bass and your mains to play just the upper bass, mids, and highs is (obviously) a form of bi-amping. In fact, the Rotel manual that I have even talks of this.

To my ears, the only downside to using a sub and not letting your mains play the low notes is that you do lose a little definition in the bass. Both in terms of sound and the sound stage. Of course, this is primarily do to phase and timing issues between the sound output of the sub and your mains.

IMO, the ideal setup for 2-channel music would be to have a very capable amplifier and a pair of truly full-range mains and not use a sub. I'm talking about an amp that can yield the maximum soundstage that your speakers can produce. But, if you don't have that, configuration (1) will give you a bigger soundstage and far better dynamic range with only the sacrifice of a little definition in the bass. (Or at least that's what I hear.)

- maddog

**bigburner** · 04 August 2005, 03:39 Thursday

maddog, you and I have similar views on using a sub in a 2-channel music set-up. Like you I have found that setting the crossover at 80Hz gives the best results.

I really enjoy my sub but like you I'd really prefer a pair of floorstanders that can deliver the bass that I want. Using a sub is a good compromise if you haven't got the budget for those. I like the look of the B&W 802D as my floorstanders. Beautiful but expensive. Have you seen misterdoggy's new ones at http://www.htguide.com/forum/showthread.php4?t=14949 ?

The trouble is I’d probably want a high-end sub to complement them!

PS Where is your sub positioned relative to your mains?

**maddog** · 04 August 2005, 12:33 Thursday

bigburner, I currently have my subwoofer in the left corner of the same wall as my television, front speakers, and audio rack. My setup is in my den, which is 19x26x10. My gear is on the 26 foot wall. That wall has 19 feet of wall for my gear. After that is a doorway and then a few more feet of wall to the right of that. I am using the following article as a guideline for corner placement:

http://www.rivesaudio.com/files/spkr_plcmt.pdf

I have not, however, experimented with placement in the middle of the front wall (the 26' wall) since I don't have any room for the subwoofer there due to it's size and the size of the equipment that is already there. The only other place that I tried it was in the corner on the back wall behind the listener's position. I tried it there because the people at SVS said that behind the listener was a good place for it. But, in my case, the sound was very directional there. The subwoofer just did not "disappear" when it was behind me. But, the corner placement on front wall works pretty good in my setup. Only about 1% of the time does it sound like the bass is coming from the left half of the room where the subwoofer is. The other 99% of the time the subwoofer just "disappears" and the bass sounds like it's being produced by the other speakers. So, the corner placement seems to be working pretty good for me.

BTW, MisterDoggy's setup with those 802D's looks pretty sweet. I've never heard 802's, but they are definitely some of the best looking speakers I've ever seen. Very stylish.

**javis** · 07 August 2005, 05:07 Sunday

bigburner,
Got my second DD15 yesterday as the first one had a problem with the test sweep. That is to say it just didn't work.
In between waiting for conformation that the unit was faulty and it's replacement I received my two sets of RCA cables.
I hooked everything up using method (1) and although I only spent a minimal amount of time on it there is an immidiate problem I fear I am facing (or that I need to solve).
As with this type of cable set up the sub incorporates the use of it own 80hz high pass crossover. I am under the understanding that this is a fixed scenario that can not be altered. I am acheiving an almost flat system response from 15hz to just below the 80hz mark. I then get a spike of over +8db at 80hz (the crossover point) which tappers back out at 100hz. The main speakers are acheiving this as I have dropped the sliders on the DD's equalizer to -12 on 80hz & 100hz to no avail.
If you or anyone else can help me out on this one I would appreciate it as I am very much a novice.

**tboooe** · 09 August 2005, 11:03 Tuesday

javis, I am very interested to see what you come up with. I too am seriously considering getting a dd10 or 12. I have not yet decided which connection method I should use though.

Which main speakers do you have?

**javis** · 17 August 2005, 23:08 Wednesday

tboooe,
After spending alot of money on two sets of (3 meter) quality RCA Cables, I found that no matter how much I played around with settings it simply sounded crap. I then proceeded to hook it up using L&R RCA Sub Input to Denon 3805 A/V LFE preout. I set the speakers to small, crossover at 80Hz, played around with the DD15 Eq and presto. We have lift off!

Subwoofer connection headache..

Subwoofer connection headache..

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