Multiple different speakers same spot bass results

[ematthews]

So I marked out a spot on my floor to make sure all my speakers were placed in the same spot when I changed them out. Why is it then that some speakers have no bass in the center seating position and some have good bass response. My towers with the lowest rating bass response are very thin in this spot. While a set of Canton Reference bookshelf’s have fantastic bass in the same spot. Strange stuff. Reminds me of my Ascend RAAL towers where I couldn’t get any bass out of them in the same room. In fact every tower including my RBH almost have no response in this room. However the Revel F208’s has way way to much.

 

[lovinthehd]

Room modes in combination with the speaker's response/position I'd suppose. How about if you move your seat or rearrange the room? Measurements?

 

[ematthews]

I can do that and have just a bit. But I just find it strange that you get such a different response from all the speakers. Even the ones that a measured very close. I get more bass out of a bookshelf. First time I’ve ever had a bookshelf beat a tower. Lol. As a note. The two towers that have week bass in the center of the room have good bass when you walk over close to either side wall.

 

[KEW]

I can do that and have just a bit. But I just find it strange that you get such a different response from all the speakers. Even the ones that a measured very close. I get more bass out of a bookshelf. First time I’ve ever had a bookshelf beat a tower. Lol. As a note. The two towers that have week bass in the center of the room have good bass when you walk over close to either side wall.

I've often noticed heavy bass along walls (mainly at concerts). Do the Cantons also give you more (too much) bass near the wall?

Reaching for an explanation, it is possible that the reflection off the front and/or side walls is causing some cancellation (in the case of the Ascends and RBH's) or addition (in the case of the F208's), and the Cantons just happen to have things work out well.
Like I say, I'm reaching, but try moving them a foot forward and sideways and see if you get the same relative behavior from the same speakers.

 

[TLS Guy]

I can do that and have just a bit. But I just find it strange that you get such a different response from all the speakers. Even the ones that a measured very close. I get more bass out of a bookshelf. First time I’ve ever had a bookshelf beat a tower. Lol. As a note. The two towers that have week bass in the center of the room have good bass when you walk over close to either side wall.

This is not strange at all but from my research expected and common no almost invariably true.

First of all when listening to program how deep the speakers go has no great impact on whether the speaker has a good perceived bass response.

The issue is that speakers have a perceived lack of bass most often because the transition from half to full space radiation is not correct in the speaker, but most often it is not correct for that speaker in a given location because of boundary effect. For most speakers this affects the band below 600 to 500 Hz. What I'm talking about is baffle step compensation. What I have long discovered is that it is a matter of total luck whether the balance of dispersion and baffle step compensation will be correct in a room at a specific location.

So in my designs where the crucial crossovers in this range are active, I make baffle step compensation totally variable. Even my passive designs have had switches to make BSC adjustible to a degree.

Of course I make my designs low Q with highly accurate bass, and with superior dispersion and flat frequency response, but my active infinitely variable BSC control to optimize the half full space transition makes my systems optimized to their boundaries.

This is a big reason that I feel passive crossovers should be abandoned. I think it is long past time to put active crossovers in speakers and the amps in the speakers not receivers.

To illustrate the point here is a trace of my active center speaker with excessive BSC. This response is what I had to do so that Audyssey did not set a crazy crossover point.

Here is the appropriate control setting of BSC for this speaker in its current location.

Getting this correct has a massive impact on speech intelligibility. This is also enhanced by the fact that reproduction from this and the other speakers is non resonant as they are traditional reverse tapered aperiodically damped transmission lines. This is shown as the roll off below the 3 db point at 48 Hz is only 12 db per octave and not 24 db.

So I would expect and predict your observation.

In summary the results most achieve are way below what would be possible with significant change in current practice.

 

[WaynePflughaupt]

Is the room square or shoe-box? If so how close is your listening position to the dead center of the room?

Regards,
Wayne A. Pflughaupt

 

[Swerd]

So I marked out a spot on my floor to make sure all my speakers were placed in the same spot when I changed them out. Why is it then that some speakers have no bass in the center seating position and some have good bass response. My towers with the lowest rating bass response are very thin in this spot. While a set of Canton Reference bookshelf’s have fantastic bass in the same spot. Strange stuff. Reminds me of my Ascend RAAL towers where I couldn’t get any bass out of them in the same room. In fact every tower including my RBH almost have no response in this room. However the Revel F208’s has way way to much.

Another possible reason why some speakers have good bass and others lack it, when they were placed in the same spot is cancellation due to floor bounce.

The woofer sends sound directly to you, while it also sends sound down towards the floor (as well as up toward the ceiling). If the distances traveled by the direct sound and the floor/ceiling bounce are right, it will sound good. But if the distances are wrong, they will arrive out-of-phase at your ears. The resulting cancellation makes the bass sound weak.

When you tested your floor stander vs. the book shelf speaker, how high above the floor were the woofers? Try raising or lowering the bookshelf speaker and see how that affects the bass sound. You can also try moving the speaker or yourself back or forth to affect that.

Diagram of direct sound vs. floor bounce

In the red trace, the big suck out at about 100 Hz is caused by floor bounce cancellation

 

[ematthews]

I think you are right on the money. The bookshelf speaker's woofer is about 24in off the ground. The floor stander is about 8 in or so.

 

[Swerd]

I think you are right on the money. The bookshelf speaker's woofer is about 24in off the ground. The floor stander is about 8 in or so.

There's always going to be floor bounce no matter how high or low the woofer is. The cancellation you get depends both on the woofer's height and the distance between you and the speaker.

 

[WaynePflughaupt]

Is the room square or shoe-box? If so how close is your listening position to the dead center of the room?

Regards,
Wayne A. Pflughaupt

 

[ematthews]

12X14. I sit longways. Speakers are about 8 feet apart and I sit about the same length away.

 

[WaynePflughaupt]

So basically dead-center in the room. I kind of figured that was the case.

First addressing your opening post:

Why is it then that some speakers have no bass in the center seating position and some have good bass response. My towers with the lowest rating bass response are very thin in this spot. While a set of Canton Reference bookshelf’s have fantastic bass in the same spot.

However the Revel F208’s has way way to much.

Rated extension has no bearing on the speaker’s bass output.

Assuming this is a “shoebox” room with all opposing boundaries parallel, the problem with rooms like this is that dead-center is a “bass hole.” I’m going to hazard an educated guess that with any speakers in the room, you’ll hear bass output increase as you move from the listening position towards any room boundary.

So if your listening position is “locked in,” you need to make sure and get speakers with greater bass output than would otherwise be needed.

Regards,
Wayne A. Pflughaupt

 

[ematthews]

I’m wondering if putting the speakers on the long wall would work a bit better. I would then be sitting up against the opposite wall which may put me a little closer. I know it’s not the best room but it’s all I have. When I was using a sub in the corner things were better of course.

 

[ematthews]

So basically dead-center in the room. I kind of figured that was the case.

First addressing your opening post:


Rated extension has no bearing on the speaker’s bass output.

Assuming this is a “shoebox” room with all opposing boundaries parallel, the problem with rooms like this is that dead-center is a “bass hole.” I’m going to hazard an educated guess that with any speakers in the room, you’ll hear bass output increase as you move from the listening position towards any room boundary.

So if your listening position is “locked in,” you need to make sure and get speakers with greater bass output than would otherwise be needed.

Regards,
Wayne A. Pflughaupt

Oh. And yes. All speakers I have used have much better bass towards the walls.

 

[ematthews]

And as a note. Just hooked my SVS sub back up. Put it towards the center of the speakers and Bam!!!! Huge bass in the center void. I just may end up using a sub. It does sound a bit sloppy however but the low end is there. Just need a sub that I can get a seemless dial in on. It’s a bit tough.

 

[AcuDefTechGuy]

The issue is that speakers have a perceived lack of bass most often because the transition from half to full space radiation is not correct in the speaker, but most often it is not correct for that speaker in a given location because of boundary effect. For most speakers this affects the band below 600 to 500 Hz.

This is a big reason that I feel passive crossovers should be abandoned.

If the main problem is the bass (below 600Hz), then why not just make the bass active? Why do you have to make the midrange and treble active?

 

[ematthews]

Interesting stuff. Active speakers look to be on the uprise too.

 

[NorseMythology]

Interesting stuff. Active speakers look to be on the uprise too.

Great idea IMO. Then the amp and speaker can be engineered specifically for one another.

 

[Kvn_Walker]

Another possible reason why some speakers have good bass and others lack it, when they were placed in the same spot is cancellation due to floor bounce.

The woofer sends sound directly to you, while it also sends sound down towards the floor (as well as up toward the ceiling). If the distances traveled by the direct sound and the floor/ceiling bounce are right, it will sound good. But if the distances are wrong, they will arrive out-of-phase at your ears. The resulting cancellation makes the bass sound weak.

When you tested your floor stander vs. the book shelf speaker, how high above the floor were the woofers? Try raising or lowering the bookshelf speaker and see how that affects the bass sound. You can also try moving the speaker or yourself back or forth to affect that.

Diagram of direct sound vs. floor bounce

In the red trace, the big suck out at about 100 Hz is caused by floor bounce cancellation

I also have a small listening room which limits my placement options, and experience this suck-out to some extent with my towers. What about using area rugs or carpet squares in front of the speakers to "catch" the floor bounce? I could get away with a large center rug over the hardwood floor if need be.

 

[ematthews]

I also have a small listening room which limits my placement options, and experience this suck-out to some extent with my towers. What about using area rugs or carpet squares in front of the speakers to "catch" the floor bounce? I could get away with a large center rug over the hardwood floor if need be.

I’m already in a carpet room. Would adding an additional area rug help out?