Double Bass Acoustic Image Contra 310

[MT Spaces]

.... In fact, the output of the amp makes me now more appreciative and interested in the granular, sometimes obscure discussions of the high pass and notch filters. Can't wait to try the amp out in the real world.

Glad to hear you got the problem solved . I see you have the Series III Contra. As you play louder in "the real world", I think you will find that the high pass filter is real useful to get the low-end sound that you like for your bass via the pick-up. I really like my new Series III Coda (plenty loud!) and the filtering options. Try different filter settings and listen closely and .... Have Fun !

 

[onemother]

Bob,

Thanks for your good wishes. BTW, I see you're in Bozeman. In 2000 I spent 6 months in Missoula learning Celtic harp in a music therapy program associated with St. Patricks Hospital. Missoula's a great town, and I liked what I saw of Bozeman when I drove through it from NJ (also got to spend a weekend along the Gallatin).

I don't play the harp too much anymore - it sits brooding in a corner, next to my bass, which gets more playing time these days. But I'd like to get back to the harp. You have to lock down both a bass line and the melody/chords on top, though. Challenging.

Take care,

Doug

 

[mje]

Anyone who has been playing with a front firing speaker behind them for a long time will need a bit of adjustment time when using an AI Combo amp. It will never sound as loud to your ears since the speaker is not aimed at your ears. ...

This is a commonly stated belief- but i think it's a misperception. The downward facing woofer on the AI rolls off low enough (I believe it's 800Hz) that it's essentially an omnidirectional radiator. At those frequencies it makes no difference what direction the woofer is pointed, and you can demonstrate that with a sound level meter. An 800Hz tone has a wavelength of 1.25 meters; any radiator smaller than 0.625 meters (24") will radiate those frequencies in a non-directional manner.

What makes other amps sound louder is that (a) they're not as flat as the AI, or (b) the speakers are not flat, and are often highly directional. It's those peaks or boosted bass you perceive as more volume. Other cabinets are far more directional, too; if all you have is a single 15" or 12" (or even 10") speaker, the lows will be omnidirectional, but the mids will be highly directional.

I have an AI combo that began life as a seperate AI head. I've played it through the AI box, EA CXL-10s, a WM-10 speaker and an Aguilar GS-12. The flatter the speaker, the less there is the perception of "loudness". The CXL-10s are among the most efficient speakers you can buy, but the Aguilar and WM-10- which are at least 6 dB less efficient- sounded "louder".

 

[drurb]

An 800Hz tone has a wavelength of 1.25 meters; any radiator smaller than 0.625 meters (24") will radiate those frequencies in a non-directional manner.

Not 1/4 wavelength, as in 0.3125 m? [Geek alert: See image below (from E. J. Jordan's Loudspeakers)].

What makes other amps sound louder is that (a) they're not as flat as the AI, or (b) the speakers are not flat, and are often highly directional. It's those peaks or boosted bass you perceive as more volume.

That can happen but it depends very much upon where are those peaks in the spectrum.

The flatter the speaker, the less there is the perception of "loudness".

This is not really a truism. It would, however, often be expected to be the case. Again, it depends upon the spectral profile.

 

[MT Spaces]

... I spent 6 months in Missoula learning Celtic harp in a music therapy program ... You have to lock down both a bass line and the melody/chords on top, though. Challenging.

Yeah Doug I'll bet that the harp is a challenge. Heck, I only play bass and am challenged with the bass line, let alone the melody line . We've got one of the better celtic harp players in the country here in Bozeman .... Tom Robison. He is also a most excellent fiddler. In fact, the first "gig" with my new Coda amp was with Tom and others at a St. Paddy's Day fiddle tune and Irish song shindig. Good Luck with your new amp, I think you'll like it. You can always add a 4 ohm Wizzy 10 to it later if you really want to rattle the neighbors' dishes too !

Later ....... Bob

 

[bolo]

That may be true in theory, but could you say with any certainty that if I were to take the Contra and turn it upside down and pointed it toward my ears that the perceived volume would not be greater?

Actually I think the perceived volume might actually be less than what you are suggesting.

I could be flat out wrong, and I guess I could certainly drag out my Contra and try (if the kids weren't in bed), but I am drawing from a couple of points of reference.

Rick Jones told me face to face earlier this week that the downfiring driver needs an opposing surface close by to push against to load it the way it was designed. You can leave it flat, or prop up the front. You can leave it on the floor, or place it on a chair. But if you flip it on its back (which I have done), or flip it all the way over on its top as Bob was suggesting, than I would bet you would actually get less perceived volume, or at least a different and a thinner sound. As Rick explained it to me (I think), that's because the driver would not be loaded the way it was designed. It needs that surface close by to "push" against. Rick said they had experimented with different heights of the cab off the floor, and different heights produced different results.

And this loading is not exactly the same as floor coupling, at least as I understand it (and I could be wrong ...). The same loading would be in effect if you put the Contra up on a chair, as I do sometimes. As long as the driver is firing right into the surface of the chair, the proper loading is achieved for the driver and the cabinet with the way it is tuned to "work as designed." But up on a chair, it is decoupled from the floor (mostly, except whatever energy transmits through the legs of the chair).

But heck ... I could be all wet.

 

[drurb]

I could be all wet.

No, you are right on target.

 

[bolo]

This is a commonly stated belief- but i think it's a misperception. The downward facing woofer on the AI rolls off low enough (I believe it's 800Hz) that it's essentially an omnidirectional radiator. At those frequencies it makes no difference what direction the woofer is pointed, and you can demonstrate that with a sound level meter. An 800Hz tone has a wavelength of 1.25 meters; any radiator smaller than 0.625 meters (24") will radiate those frequencies in a non-directional manner.

What makes other amps sound louder is that (a) they're not as flat as the AI, or (b) the speakers are not flat, and are often highly directional. It's those peaks or boosted bass you perceive as more volume. Other cabinets are far more directional, too; if all you have is a single 15" or 12" (or even 10") speaker, the lows will be omnidirectional, but the mids will be highly directional.

I have an AI combo that began life as a seperate AI head. I've played it through the AI box, EA CXL-10s, a WM-10 speaker and an Aguilar GS-12. The flatter the speaker, the less there is the perception of "loudness". The CXL-10s are among the most efficient speakers you can buy, but the Aguilar and WM-10- which are at least 6 dB less efficient- sounded "louder".

I think Rick Jones would agree that in many cases the downfiring design is misunderstood somewhat. Some of what you are describing of front-firing cabinets having greater perceived volume is something I think he tried to explain to me, and this reminds me of one of the things he mentioned, called frequency "beaming". It dealt mostly with the directional properties esp. in the mids for say 8" and 10" drivers, just like you said.

To bad he was explaining it to me, who only has a feeble incling at best of these sorts of things. I nodded my head in agreement. I can sort of conceptualize what he meant, and I really appreciate him taking the time to try and explain it to me.

 

[bolo]

Get a little distance between you and the amp and you may find it louder than up close.

Yeah, I have found this to be true also. Rick Jones said the same thing to me in the demo room at AI headquarters earlier this week. And he kinda nodded in the direction of the front-firing 5" driver as he did so. He also suggested trying it with the legs extended to tilt the front up.

 

[drurb]

I think Rick Jones would agree that in many cases the downfiring design is misunderstood somewhat. Some of what you are describing of front-firing cabinets having greater perceived volume is something I think he tried to explain to me, and this reminds me of one of the things he mentioned, called frequency "beaming". It dealt mostly with the directional properties esp. in the mids for say 8" and 10" drivers, just like you said.

To bad he was explaining it to me, who only has a feeble incling at best of these sorts of things. I nodded my head in agreement. I can sort of conceptualize what he meant, and I really appreciate him taking the time to try and explain it to me.

Take a look at the picture I posted above. It shows that a driver will "beam" more the larger it is relative to the wavelength of the frequency it is radiating. So, a large driver that is forced to radiate mid and higher frequencies will beam them to a far greater extent than a smaller driver. That's one reason tweeters are small! Now as far as greater perceived loudness from front-firing cabinets goes, the beaming will not account for that unless they are pointed right at the player.

 

[mje]

Oops, right, a quarter wavelength, not a half. So a speaker 12" or smaller is omnidirectional below 800Hz, ceteris paribus.

Placing the woofer in the "down firing" position also has the effect of placing the source right at a room boundary, which goes a long way towards minimizing the interference you'd otherwise get between direct and reflected waves.

Tilting an AI combo up has a number of effects- as noted, it unloads the speaker somewhat. I wonder if there isn't a slight "horn" effect- the pressure below the speaker varies from the rear of the cab towards the front- which would act as an impedance converter, just as a horn enclosure does? It would be interesting to measure this.

Re my comments about flat systems not sounding as loud: That would only be true relative to the typical BG amp/speaker/combo, which is often voiced with peaks that do make them seem subjectively louder.

 

[drurb]

Oops, right, a quarter wavelength, not a half. So a speaker 12" or smaller is omnidirectional below 800Hz, ceteris paribus.

Placing the woofer in the "down firing" position also has the effect of placing the source right at a room boundary, which goes a long way towards minimizing the interference you'd otherwise get between direct and reflected waves.

Tilting an AI combo up has a number of effects- as noted, it unloads the speaker somewhat. I wonder if there isn't a slight "horn" effect- the pressure below the speaker varies from the rear of the cab towards the front- which would act as an impedance converter, just as a horn enclosure does? It would be interesting to measure this.

Re my comments about flat systems not sounding as loud: That would only be true relative to the typical BG amp/speaker/combo, which is often voiced with peaks that do make them seem subjectively louder.

We are, once again, in violent agreement!

 

[Pat Harris]

I just got my Series III Contra on Friday and had a chance to do some rehearsing today with a big band. Here's my question:

Is this amp "for the audience" so to speak?

What I mean, is that the tone I'm hearing on the bandstand has this kind of low-midrange honk to it. Not boominess, but it's like some fequency that can't be tweaked out (at least just yet, I've got to experiment. I set treble and bass at 12:00 but the I put the mids at around 8:30) However, at around 20 feet away it was the best amplified tone I'd ever had.

I guess I was under the impression this amp had more of a uniform sound no matter where you are standing in relation to it? I'm still digging it, though.

 

[mje]

...
I guess I was under the impression this amp had more of a uniform sound no matter where you are standing in relation to it? I'm still digging it, though.

There's always the room to consider. Might be a resonance between two walls, or even just interference between the sound coming right from the bass and the sound coming from the amp. Is it just you who hears the honk, or is it audible out in the audience?

 

[Pat Harris]

In the audience, the amp sounds great. It's only when close to it that the low-mids take over the mix.

 

[Bob Branstetter]

I just got my Series III Contra on Friday and had a chance to do some rehearsing today with a big band. Here's my question:

Is this amp "for the audience" so to speak?

What I mean, is that the tone I'm hearing on the bandstand has this kind of low-midrange honk to it. Not boominess, but it's like some fequency that can't be tweaked out (at least just yet, I've got to experiment. I set treble and bass at 12:00 but the I put the mids at around 8:30) However, at around 20 feet away it was the best amplified tone I'd ever had.

I guess I was under the impression this amp had more of a uniform sound no matter where you are standing in relation to it? I'm still digging it, though.

IMO, a low-midrange honk is not normal. I keep my bass, treble and mid at 12 o'clock and get a wonderful sound both up close and away. Are you using the tilt legs? Is is possible that you've got the filters on? As stated in other threads, the AI combos do take a while to get used to. Regardless of the reason, a front firing speaker behind you is going to sound louder to your ear than a down firing AI combo. I also find that I can actually hear some my bass with an Contra or Coda rather than just what is coming from the pickup and speaker.

 

[Pat Harris]

After rehearsing again today, I'm coming to adapt to the sound the contra puts out. I really dig the amp, but based on reviews I had a different conception of the sound it puts out in my head.

Perhaps "honk" was the wrong word to describe the sound.

It's just such a transparent sound opposed to the SWR 350 and 4x10 rig I was using prior to this. I just need to get used to the more midrange in the tone, because what sounds a little throaty on the bandstand sounds absolutely killer in the house.

 

[Pat Harris]

Okay, new question:

Does anyone have a problem with the Contra SIII bottoming out on a low E? On a past gig, I had both the input volume and master volume at 12:00. As we're playing, I just lit into an open E and the cab or amp couldn't handle it. I don't know what the story is. It seems like the amp is way overpowered for the cab. I realize it's for clarity and tone, but I was only running at 50% power. In my experience of playing in a hall with a big band, I'm not so certain I was cutting through either.

Thanks,
Pat

 

[tornadobass]

I've wondered about this with my Clarus ser 3 and a Wizzy cab, but it hasn't happened yet. In part, watch out for really wailing on a string, especially open E. Turn on the HP filter to make the occasional big note a bit more tame...I've noticed that even at the lowest frequency setting (30hz?), that the speaker cone doesn't move as much with either my BugBass or American Standard with RSII pickup.

 

[Bob Branstetter]

Okay, new question:

Does anyone have a problem with the Contra SIII bottoming out on a low E? On a past gig, I had both the input volume and master volume at 12:00. As we're playing, I just lit into an open E and the cab or amp couldn't handle it. I don't know what the story is. It seems like the amp is way overpowered for the cab. I realize it's for clarity and tone, but I was only running at 50% power. In my experience of playing in a hall with a big band, I'm not so certain I was cutting through either.

Thanks,
Pat

I haven't had this happen to me on low E or even low C.