[hartwerger]

I know this is going to be a strange post.  And, I know that its hard to diagnose an acoustic problem just from reading about it and not being there in the room.  So, if there are no replies, its ok, I do understand.  I just hope for future reference that you guys know that I am a normal person and not as far gone as this topic may lead one to believe.

Anyway, here's the situation.  Used to have Magnepan speakers, a dipole speaker and different wave dispersion than box speakers.  I now have Merlin speakers, a box speaker.  I played a disc the other day that I played many times when I had the Maggies.   There is a part on the disc where the kick drum would sound so real that it always got me to open my eyes to check to be sure the drummer was not in the room with me.  I played this disc on the Merlins yesterday and when it got to the part where you would hear the kick drum, I didn't hear the kick drum.  I'm not talking about it not sounding as good as it did on the Maggies; I'm talking about that I couldn't hear the kick drum at all.  It was like the kick drum had been erased from the recording.  I listened to that part on the disc many times over to confirm what I was hearing (or not hearing).  No kick drum.   But, when I got up to turn down the volume and walked slightly behind the speakers, there it was, the kick drum.  You could hear it (mostly feel it) behind the speakers, even to the side of the speakers, but once out in the front of the speakers, its gone.  Other than the missing kick drum, the recording sounded pretty good.  The bass sounded good and from what I can tell, the bass hits notes that are lower in frequency than the kick drum (though I could be wrong about that fact, I suppose).   Nevertheless, the whole phenomenon of this missing kick drum makes me wonder what other frequencies and sounds I may be missing.

So, does this missing kick drum sound like an acoustical problem or a speaker problem?  (Note:  the only change in my components have been the speakers; all the equipment that I had with the Maggies is the same.)  If it is an acoustic problem, any thoughts on what the solution may be?  I'm not much of a DIY guy and most acoustic room treatments are out of my price range.  I could afford a $100-200, but that's about it.  Any cheap experiments I could do before spending money on room treatments to be sure they might work?  Any thoughts, opinions, suggestions are appreciated.  Thanks.

[Daygloworange]

The only thing that I could think of that could cause a radical thing like that would be an out of phase problem. Check the polarity of your speaker wires. Doubtful that it could be possible, but perhaps there is a polarity problem with one of the woofers.

Very curious situation. 

Cheers

[gitarretyp]

That sounds like an acoustics problem (or possibly a polarity problem as dayglow pointed out). However, kick drums typically have a broad range of frequency output (square'ish wave), so an acoustic problem seems rather strange. Since you had dipole bass with the maggies, the room will be loaded very differently with the monopole merlins. Try listening a couple feet from you typical listening position. You probably just need to experiment with different speaker/listening positions.

[hartwerger]

Polarity problem I hadn't thought of, but I'm fairly certain everything is connected properly.  Of course, I suppose my amp may be inverting and my pre non-inverting which could cause a phase shift. 

I did experient with listening positions and that didn't help, at least not significantly.  There were some positions where I thought I was starting to hear the kick drum, but it was still a strain.

Thanks for the help.  Seems like I might have a bigger mystery than I thought.

[mfsoa]

Had something similar happen to me, but big difference was that my experience was in two different rooms:

John Scofield "Uberjam" - After the cool spacey intro, a very low, large-sounding drum starts to beat a pattern that continues throughout the song.

At home (VR4JR) this drum has a thick, large, resonant character though it is still low in the mix. More resonant than a kick drum. But there is the presence of a large drum with vibrating skins.

But at a store (Gallo 3.1, without an additional amp hooked up to the 2nd voice coil (I think this how it can be hooked up)) this drum sounded like a single knuckle rapping on a rigid wood surface.

I was truly amazed at this difference, even given the different rooms!

I don't know which is right, but I know which one I prefer!!   

[BobRex]

Are you sure the BAM is working properly (assuming you have the VSMs and not the TSMs)?

[nodiak]

I think it's most likely the box speakers interaction with the room. Placement might help or cure it. Dipoles in my room have been smoother in the midbass. Now I work around it with a seperate sub xo'ed in that region so I can dial it in, and keep the mains above it.
Don

[hartwerger]

The Bam should be working.  Had it upgraded a few months ago by Merlin.  The bass guitar was audible and sounded fine.  But the thud of the kick drum could only be heard from the side or behind the speakers.  That's what lead me to believe it might be acoustic.  Seemed like the speaker was producing the sound, but it was getting lost somewhere.  Now the polarity/phase issue I hadn't considered and may need some exploring.  Will have to wait until I get home from work though.  You can see by my posts that I'm really busy here at work. 

[cliffy]

I would post your question/problem on AudioAsylum's General Speaker Forum. 
Bobby P. from Merlin is very responsive to posts there.

Hope that helps.

[TomS]

You might tell us about your room dimensions, where the speakers are placed, and the listening position.  I have VSM-MX/SBAM with lots of Realtraps, but never had anything like you're describing happen in my situation, even without the treatments.  As always Bobby can you help you any time on the phone.  Tom

[gitarretyp]

Polarity problem I hadn't thought of, but I'm fairly certain everything is connected properly.  Of course, I suppose my amp may be inverting and my pre non-inverting which could cause a phase shift. 

I did experient with listening positions and that didn't help, at least not significantly.  There were some positions where I thought I was starting to hear the kick drum, but it was still a strain.

Thanks for the help.  Seems like I might have a bigger mystery than I thought.

Amp/preamp inverting phase is not the issue as both channels would be inverted. If it's a polarity issue, one channel's woofer is is wired opposite the other's --doubtful since the phase problems would extend pretty high in a two way design. You could check this by either inverting the speaker wires on one channel, or try operating one channel at a time. If one or both channels produce audible kick drums when operating independently, it could provide some input regarding room acoustics, also.

[bpape]

My guess is that it's one of two things or a combination of both.

- SBIR issues due to wall proximity causing a cancellation at that freuqency.  This can be due to distance to front and/or side walls.

- Seating location if you're sitting in a null at that frequency range. 

You can check to see if it's the SBIR issue by simply pulling the speakers out a foot or so which would shift the frequencies impacted.  If this is the case, some thicker absorbtion directly behind the speaker should help.  Ditton with the side wall to driver center distances.

Also check the seating position if it's different than where you were before with the Maggies.  Squat down maybe a foot closer or farter and say 6" off center so your head is at the same level and listen.  If the drum is back, then this is at least part of the issue.

Bryan

[mark@marktwain]

Squat down maybe a foot closer or farter

FARTER  Ya think that's what the missing kick drum was Bryan?? Sorry I couldn't resist.

Mark

[AB]

I had a very similar experience not too long ago.

There I was, sitting enjoying some music probably just like you were, when I decided to change the CD that was playing. I got up, went around behind my listening spot to where the CDs are stacked and what did I hear back in that corner? A very strong kick drum that I DID NOT KNOW WAS EVEN IN THE MIX. I was floored. I thought I was hearing everything.

This started a moderately frustrating room acoustics journey that I am happy to say is now finished.

I had every corner bass trapped. I had the front ceiling/wall corner trapped too but even with these bass traps I was missing that kick drum. Did I over trap the room? I was convinced this was not the case. I even went on line and googled a bunch of info on kick drums - frequency, attack and decay, anything to help me understand what was happening. All that only helped reassure me that I had a room problem.

I pretty much decided there was nothing I could do to directly effect this phenomenon without just trying to sort my room out in general just a bit more.

I bought two RealTraps Diffusors to see how these would benefit the room. I knew these wouldn't bring that kick drum back into the mix but they were part of what needed to be sorted out. Foremost I had a strong comb filtering problem. It was much more distracting than the missing kick drum and I was hoping the diffusors would fix this.

With the diffusors in place I was forced to reposition my speakers to get back my solid center image and in doing this I noticed the kick drum was ever so slightly back. I could hear it at my listening spot. It was not hitting me in the chest like it should have been but at least it was there.

But with the diffusors in place and the new positioning of my speakers I had made the comb filtering worse! I was beside myself but at least I knew then what was happening - I had first reflection problems. I believed that these were not a problem in my room because of a large opening just outside the right speaker ( no wall, no reflection) and a large window treatment just to the outside of the left speaker. Well, I couldn't have been more wrong. I added two RFZ panels to these areas and that was that. With a bit more repositioning of the speakers I had the kick drum back in full and the comb filtering thing was gone as well.

I can only assume that the room issues forced me to have a speaker setup that was putting my listening spot in a kick drum frequency null or that the first reflections plus this combined to create a very strong, very broad null. I cannot say what exactly allowed the drum to be heard again as it was a step by step return. I can say I did have the speakers positioned all over the place in an attempt to get a good room response and nothing worked - I had to treat the room.

It sounds to me like you have the same problem I did. I would start moving the speakers around. I expect then that you will get your kick drum back but loose something else in the effort. Your room is forcing you into compromises.

[hartwerger]

Thanks everyone for all the thoughts and suggestions.  Although I didn't try repositioning the speakers last night, I did listen hard to many other recordings and glad to report that not all kick drums play at the same frequency as the one that is missing on the other disc.  Could hear kick drums loud and clear on many other CDs.  So, it must just be this one particular frequency that is getting lost somewhere in the mess I call my listening room.  Particular thanks to AB for his reply about his own experience.  I was beginning to think I was going crazy until AB shared his own similar experience.   Not exactly happy to hear that room correction can be so difficult, but I was anticipating an easy solution either. 

For anyone else you may want to chime in, here's some additional information about my room.  First, the room does have a large bay window off to the side of the left speaker, but the room does pass the slap echo test; doesn't appear to be an overly live room, but far from dead.  Dimensions are approximately 14x18 with the speakers on the short wall.  Speakers are approx. 4' out from the wall behind them (measured from the front baffle) and are about 6 1/2' apart (I don't know the distance from sidewalls).  My listening position is not set in stone as I've been varying it lately, but for consistency sake, I'd say its b/w 7-8' from the speakers.  The remainder of the room is a bit too complicated to describe and maybe one day I'll post pictures just to get some opinions for improvement and treatment.  Without getting into any monotonous detail, I'll just say that behind the speakers there are built-in cabinets and bookshelves which may or may not be creating some acousitcal problems (the only reason I mention this is simply to point out that I do not have a bare wall behind the speakers and the cabinets and bookshelves cannot be moved so if they are part of the problem, the only solution may be to change my room).  Anyway, not sure any of this helps, but there for the taking just in case. 

Thanks again to all.  Keep on enjoying the music.

[bpape]

Yeah - farter, that's the ticket!   

Unfortunately, the clap test does nothing to reveal how the room is responding in the bottom end.  It also is kind of a flawed thing since the source of the clap is not where the source of the music is coming from.

In any case, you didn't say where the seating was in relation to the room length and width.  It could be a cancellation off the back wall which is very common.  It could be that you're sitting in a width null.  Could be a combination of both.

Bryan

[Ethan Winer]

Could hear kick drums loud and clear on many other CDs.  So, it must just be this one particular frequency that is getting lost somewhere in the mess I call my listening room.

I agree with the others that the problem is almost certainly room acoustics. Especially if you have no bass traps now.

Bass drums encompass a wide range of fundamental frequencies, from as low as 30 Hz to well above 100 Hz. And as you may know, room peaks and nulls can be very narrow and highly localized. So it's not uncommon for a bass drum on one recording to be plenty loud, and another to be lost completely. It all depends on the drum's fundamental and how it aligns with your room.

--Ethan

[hartwerger]

I believe that I'm sitting a little over a third into the room (from the wall behind me).  What I find most fascinating about this experience is how dramatic the differences are in room interaction  b/w dipole speakers and monopole.  I could hear the kick drum fine with the Maggies.  Because the room is a shared family room, extensive room treatments are probably not going to be acceptable.  However, I have received permission to use tri-corner traps or treatments (the corners where the walls and ceiling meet).  My only concern is whether I'll create more problems than I solve by starting with such treatments especially when I'm limited in how extensive I can get involved in such treatments.  I'm sure I'm not alone in this dilemma.   

[bpape]

Try sitting/Squatting at 62% of the room legth and about 6" off center as I not so elequently said before.  See what that does to help the situation.

Also, in addition to dealing with the corner bass absorbers, seriously see if you can sweet talk the signficant other into a 4" thick bass absorber centered on the rear wall behind the listening position.  You can hang a tapestry or whatever over the front and it will still work fine.

Bryan

[AB]

Hi Hartwerger,
My room is 14 wide by 18 deep too. My speakers were about 6.5 feet apart but are now 8.5 feet apart.
The speakers baffles are 4 feet from the front wall. My listening position is at about 9.5 feet from the speakers baffles as a leg of a triangle. I don't know what the distance is from the plane of the baffles.
The speakers are about 2.5 feet from the side "walls".

Treating the room wasn't difficult, it was just a process. Step by step I was dragged into it and at each step there were improvements that disproved my skepticism. With every step (added piece) I said, "Well, I'll be damned."

I would move those speakers more to the outside. As I wrote, I suspect you'll end up with first reflection issues with them closer to the side walls but at least you'll have an idea of how the wider positioning effects the bass response.