What is missing from many 2 channel systems.

Clipdat

VR3 wrote: »

On most 2 channel preamps, the second set of outputs used for a subwoofer connection is a parallel connection to the main outs. Splitting this signal, in my experience, is detrimental to the overall sound quality of the system.

From an engineering perspective, what is the fundamental reason for this? I would have thought that since both the preamp's primary and secondary outputs are "firing simultaneously" then they'll both reach their destination(s) (main stereo amplifiers line in, and sub's line in) at the same time.

VR3

From my understanding, it ultimately will change the impedance seen by the preamp and the output voltage requirements.

I think you will see alot of people say it doesn't make a difference with just two amps running off a split output. I just have heard it to many times.

You get this weird compression, lack of spatial clarity, lack of dynamics.

Last time I experienced it was when Tom was using a Schitt preamp, we rerouted the subwoofers a different way and the sound was instantly back to normal.

My old candela preamp really showed this when using the second set of outputs

msg

VR3 wrote: »

From my understanding, it ultimately will change the impedance seen by the preamp and the output voltage requirements.

This is what I wondered about such connections, whether it had any significant effect.

Do you remember what the change was you guys made in the subs' connection that brought the sound back?

pearsall001

Running straight line out from the pre will make no difference at all, they are designed for that. Now if there is a splitter / splitters involved then yes there will be an impedance difference that could muck up the sound...to a degree. Other than that I'm scratching my head on this one.

VR3

There is no difference between a splitter and a pair of jacks in parallel to the outputs mounted on the back of the preamp, they just look more professional 😜

VR3

msg wrote: »

VR3 wrote: »

From my understanding, it ultimately will change the impedance seen by the preamp and the output voltage requirements.

This is what I wondered about such connections, whether it had any significant effect.

Do you remember what the change was you guys made in the subs' connection that brought the sound back?

I can't say I recall, but Tom lurks passively in the background like batman, he may respond

invalid

I would say it depends on the preamp involved, some preamps don't have a problem with it and others do. I do think that it works better to run a sub from the speaker outputs of the amp, then you get the sound characteristics of the amp.

mhardy6647

Splitting line level outputs is generally much less of an issue than combining line level outputs.

https://www.prosoundweb.com/rane-note-why-not-wye-or-y-for-that-matter/

VR3

Do you mean shorting a right and left together or combining two preamps or CD players into one input? Hmm, that sounds toasty

In pro sound, splitting signals are normal operation given all of the speakers and amps involved

mhardy6647

VR3 wrote: »

Do you mean shorting a right and left together or combining two preamps or CD players into one input? Hmm, that sounds toasty

In pro sound, splitting signals are normal operation given all of the speakers and amps involved

Yes, summing to mono.
The problem is that one channel tends to ("wants to") drive the other one. It generally won't do any harm, but it's not an audio "best practice". Thus the addition of resistors (or other impedance control) in a "proper" sum-to-mono box.

Splitting is pretty benign, as long as the "source" (i.e., the upstream component) can muster up adequate drive for the two parallel loads. Of course, splitting a signal in twain = 3 dB decrease in each signal level, all else being equal.

Thorton

VR3 wrote: »

This rough test of my in room response at the seating position.

Ignore the huge dip in the upper frequencies, for some odd reason the midrange test tone ends before the high frequency test tone begins.

I marked 30hz and 20hz on the chart for reference. I just don't see how a subwoofer would help me unless I just wanted a bass heavy sound, which I totally get people like. Almost every audio meet I go to I am turning off subwoofers.

Can you explain your graphs a little more? I’ve never seen a frequency plot start at 0db then drop.
1.) Is 0 dB the reference point?
2.) Based on the yellow sweep: 70-250 Hz would be about a -1 to -2 dB, 600-2000 Hz would be about a -13 dB and 7000-10000 Hz would be about a -25db. That is a very steep slope (based on your axis parameters) which I would think would be very easy to distinguish with the ears. Am I missing something? I’ve ignored the dip 5000 Hz.

VR3

That chart is based off of dbfs which you can read more about here

https://en.m.wikipedia.org/wiki/DBFS

The white line is insignificant

The yellow line is captured by peak level at that particular frequency

I won't pretend to be the expert on this type of chart, I have a mic on order that will allow me to take more credible charts.

There is also a very good chance my smartphone microphone has built in compatibility changing the readings

Thorton

I believe we definitely need to see the results with a calibrated mic. With the smartphone mic, your results show that there is a significant hump dominating the sound between 70-250 Hz. If you base that as the reference point, your low end at -3dB is probably 60-70 Hz. I’m not an expert either, just enough knowledge to make me dangerous!

In the end, if it sounds good to your ears....who cares.

VR3

Lol, i can assure you that's not my - 3db and my highs are definitely not - 24db 🤣

Here is the stereophile chart, you can see why they adjusted the bass circuit in the later builds

In room I easily dig into the mids 20s no problem

machone

invalid wrote: »

machone wrote: »

I added a Velodyne 8" sub to my 2.3TLs using high level inputs with the same speaker cable. Took a while to dial it in but it integrated with great results. Never took any measurements just used my ears.

I thought the 2.3tl's went down really low already, what do you gain with a sub?

They do dig deep and the sub reinforces the bottom. The combo works best in my room.

nooshinjohn

machone wrote: »

invalid wrote: »

machone wrote: »

I added a Velodyne 8" sub to my 2.3TLs using high level inputs with the same speaker cable. Took a while to dial it in but it integrated with great results. Never took any measurements just used my ears.

I thought the 2.3tl's went down really low already, what do you gain with a sub?

They do dig deep and the sub reinforces the bottom. The combo works best in my room.

I use a REL S5 with my 1.2TL’s. I have it dialed in the same way. It is completely inaudible, but it solidifies the bottom end. This has the added benefit of adding more clarity and definition to everything above it.

TEAforONE

I have a small dedicated listening room. 13'x9'x8'. I run 3 HSU subs. All older models. They are smooth,and really add to the body,texture of the music,as well as greatly expand the soundstage. I'm not necessarily a bass head,and they are crossed at about 50hz,and the volume is barely cracked on them. They just add so much to these ears,I wouldn't have it any other way.

I am,without a doubt,NOT a techie. As far as room sweeps,room correcting gizmos,and the such,not gonna happen here. I don't have the know how. I'm quite happy living like a dinosaur! However,I don't begrudge anyone for following their own path.

mantis

TEAforONE wrote: »

I have a small dedicated listening room. 13'x9'x8'. I run 3 HSU subs. All older models. They are smooth,and really add to the body,texture of the music,as well as greatly expand the soundstage. I'm not necessarily a bass head,and they are crossed at about 50hz,and the volume is barely cracked on them. They just add so much to these ears,I wouldn't have it any other way.

I am,without a doubt,NOT a techie. As far as room sweeps,room correcting gizmos,and the such,not gonna happen here. I don't have the know how. I'm quite happy living like a dinosaur! However,I don't begrudge anyone for following their own path.

There is no right or wrong way man. We all have to travel our own audio paths. I prefer to share what I learn with the class so if someone can improve their system then that makes me quite happy.

TEAforONE

mantis wrote: »

TEAforONE wrote: »

I have a small dedicated listening room. 13'x9'x8'. I run 3 HSU subs. All older models. They are smooth,and really add to the body,texture of the music,as well as greatly expand the soundstage. I'm not necessarily a bass head,and they are crossed at about 50hz,and the volume is barely cracked on them. They just add so much to these ears,I wouldn't have it any other way.

I am,without a doubt,NOT a techie. As far as room sweeps,room correcting gizmos,and the such,not gonna happen here. I don't have the know how. I'm quite happy living like a dinosaur! However,I don't begrudge anyone for following their own path.

There is no right or wrong way man. We all have to travel our own audio paths. I prefer to share what I learn with the class so if someone can improve their system then that makes me quite happy.

That is an absolute fact. There are so many folks out there that believe it’s “my way or the highway “. I know what I like, but that in no way,shape,or form is going to be what’s anyone else is going to like. You like subs? Cool! You don’t? That’s cool too! It always makes me cringe when people speak about their preferences as “absolutes .” I think the only absolutes in this hobby/sickness, are that our gear needs to have electricity. After that,it’s every man/woman for themselves.

Joey_V

Still looking for my JL CR1 to complete the sub portion of my system

mantis

Joey_V wrote: »

Still looking for my JL CR1 to complete the sub portion of my system

The CR1 is a nice pice of gear. I have used it many times to setup dual subwoofers in a room.