RM40's Making a clicking noise at high volume 100+ db's

zybar · « **on:** 20 Mar 2004, 05:00 pm »

I was having a brief very loud listening session last night and swore I heard a clicking noise coming form one of my speakers. I immediately shut everything down and started thinks back up at a more moderate volume level and didn't hear anything. I slowly increased the volume, but couldn't reproduce the noise.

I know it isn't on the recording.

Any thoughts? (Besides it was all in my mind...)

George

Marbles · « **Reply #1 on:** 20 Mar 2004, 05:22 pm »

There has been talk of a speaker cable being too close to a woofer and the woofer striking said cable making a noise. Could this be it?

zybar · « **Reply #2 on:** 20 Mar 2004, 05:28 pm »

I don't think so...

I do have the Analysis PLus cable, but I tucked it away pretty good when I had to do surgery on the speakers.

Plus, I would think it would be easy to reproduce if it were the cable slapping against the woofer.

George

Brian Cheney · « **Reply #3 on:** 20 Mar 2004, 06:22 pm »

Might have been something in your room, in close proximity to the speaker. Wire slap can be an intermittant problem; some cable ties will solve that. Play the same material at the same level while standing next to the speaker and see where the noise comes from.

Redbone · « **Reply #4 on:** 21 Mar 2004, 02:52 am »

I'll bet that your amp was starting to clip. My QSC amp has clip indicators that start to flicker when I get up to that volume level. The 40s can really suck up the power.

Xi-Trum · « **Reply #5 on:** 22 Mar 2004, 06:51 pm »

I'm with Redbone. Your amp was clipping.

Redbone · « **Reply #6 on:** 22 Mar 2004, 07:35 pm »

George,

I was fooling with my 40s last night and although it is obvious, I never realized this before. The entire cabinet is open inside and sealed. If you press on the top woofer, the bottom one, a good four feet away, moves. The passive woofer absorbs all the motion from both the lower and upper woofers, which is why changing the putty affects the sound, a lot. Also, motion from the bottom woofer affects the top one and vice-versa.

By adding wool behind the NEOs, you can dramatically affect the interplay between the two active woofers and the passive one. This is why adding wool changed the sound in your speakers.

I have great respect for Brian's skill at constructing these speakers, choosing the method of "porting", and making them adjustable. Indeed all of the drivers do seem to interact, along with the cabinet they are in. Changing the putty or pots can affect more than just the driver that is directly associated with the device, the others are affected by proxy.

Again, I have great respect for Brian's choice in selecting and locating the drivers. All of the pieces must interact in concert to provide the final finished sound. The 40s truly are great speakers, and I am just starting to appreciate all of the different aspects that went into building and designing them. The bass is very tight and strong, but not boomy the way some us like it.

Now for a little analysis. The bottom woofer produces very little audible output, even at high volume. Two mods, putting a wooden reflector on top of the speaker or moving the top woofer to the bottom can both improve the sound. IMO, this is because the top woofer produces much more, and better sound. By moving it to the bottom of the cabinet it has more influence on the passive woofer and thus generates more sound. The floor (and the board mod) both help to channel the sound to the listener.

At the risk of pissing someone off, I am seriously considering replacing the bottom woofer with a high-end aluminum/magnesium 10" cone woofer, much like the ones in the SP Continuum. I realize that could adversely affect the whole presentation of the speaker but I like it better than adding subs. I'd appreciate any feedback you might have on this. Thanks.

Pete

Brian Cheney · « **Reply #7 on:** 22 Mar 2004, 07:50 pm »

The 10" lowbass Megawoofer is a far better driver than any commercial metal cone woofer. If you do the replacement you envision the sound of the speaker will be completely destroyed.

Redbone · « **Reply #8 on:** 22 Mar 2004, 08:02 pm »

Thanks Brian, you are probably right and I do respect your opinion. You have done a really good job designing these speakers and you know a lot more about them than I.

Last night, when analyzing this, it occured to me that both the bottom and top woofers exert air pressure on each other, with the passive woofer the slave that relieves the pressure. Since the two active woofers are not identical in design, performance or function, is it possible that they can interfere with each other in a negative way ?

Pete

ctviggen · « **Reply #9 on:** 22 Mar 2004, 08:18 pm »

I don't think so, as the passive radiator would take any discrepancy (by moving in or out). Even underdamped, the passive radiator should take the difference in air pressure (if there is any).

Horsehead · « **Reply #10 on:** 22 Mar 2004, 08:52 pm »

Quote from: Brian Cheney

The 10" lowbass Megawoofer is a far better driver than any commercial metal cone woofer.

After owning two pairs of RM40s and the SP Tech Continuums I would respectfully disagree with that statement. Yes, the 10" lowbass Megawoofer is a fantastic driver, but I think it is misleading to state nothing else commercially available competes with it. In my room, with my gear, the two 8" metal cone woofers have FAR better bass extension, dynamics, and attack then the 3 10" drivers used in the 40s.

This is just my opinion and not a "cheap shot" at the 40s because I don't own them anymore. I still consider the 40s one of the best speakers available today.

ctviggen · « **Reply #11 on:** 22 Mar 2004, 09:45 pm »

I thought there were two 10 inch drivers and one PR (which isn't a driver)? So, you're really comparing two 10s with two 8s (and I have no comment as to which is better). Just for the record.

Horsehead · « **Reply #12 on:** 22 Mar 2004, 10:29 pm »

"Drive complement: 10” PR, 10” WCF Megawoofer, 10” WCF midbass Four 8” Neodymium ribbon mids, two 1” spiral ribbon tweeters; single amp or biamp operation"

I guess it is technically considered a "driver" by the specs, but I see and agree with your point.

ctviggen · « **Reply #13 on:** 23 Mar 2004, 01:40 am »

I find bass to be very weird when it comes to speakers. My Linns have one 8-inch rear-firing woofer. If you get that speaker close to the wall, it'll blow you out of the room with bass. Yet, if you get it in the room (which I have to do, as they have to flank my RPTV), you'll not hear much bass at all. My friend has a set of speakers with two small (5 inch?) drivers for the bass, and those speakers can kick out the bass. We did a head-to-head between my Linns and his speakers, and his speakers we thought went lower and had tighter, better defined bass, but my speakers blew them away volume-wise. So, you can't really look at the driver size and say without hearing the speaker that one speaker is going to be better than another in bass reproduction.

ekovalsky · « **Reply #14 on:** 23 Mar 2004, 02:09 am »

Perceived in-room bass response is plagued by peaks and valleys, and many woofers put out huge amounts of distortion, probably in the range of 5-10% of total output. The latter is the reason why many subs take advantage of servo circuits, although they have their own set of problems.

High quality headphones are useful in hearing what flat bass should sounds like. Of course you don't get the visceral impact since there aren't huge waves pressurizing the room, but you also don't get the bloat and distortion.