My Ampeg B100R is making a flabby flapping noise from the ports

[Bass 45]

Originally Posted by stiles72

Rich - Do you use the Ultra Lo and Ultra Mid switches ont he B-100R? When I use my B-100R, I go for a pretty deep sound as well regardless of whichever bass I'm running through it (P-bass, T-bird, Baby Bass) and I run with both the ultra lo and ultra mid engaged, and my bass knob is always at 3:00. Just curious if trying different settings with those switches changes things for you.

The settings you specified are identical to how I prefer mine (with low mid at 9:00 and the high mid at 3:00 or so - but these two knob settings change depending on if I am using an Ampeg or Fender bass).

The chuffing sound goes away with the Ultra Low on when the Bass is turned below 11:30. With the Ultra Low off, the Bass needs to be turned up to nearly max for chuffing sound to occur.

My girlfriend also owns a B100R. I should get them side by side and see if they react the same. I did have to reinforce a loose baffle board in her's a couple of years ago, but that was an obvious problem/solution.

[Bass 45]

Originally Posted by 1958Bassman

I would bet that this cabinet isn't designed to be used with a 5 string bass. When you send frequencies to the speaker and the port is tuned higher than the notes, the speaker acts like it's in free air and if you keep doing this, you'll blow the driver. If you remove the ports, the cabinet's response won't even be close to what you want/need for a 5 string bass.

You didn't have the 5 string when you used the B110R, did you?

I only use four string basses.

Thank you for the speaker warning though - it makes good sense.

[JimmyM]

Dang, sorry...forgot that it runs at 4 ohms. That does narrow your options, I guess.

[will33]

Yep, likely just reaching the limits of the cab design. Moving to a larger port would fix the problem, but, said larger port would have to extend deeper into the cab to achieve the same tuning and you're likely running out of room for it to go in there.

JimmyM.....the Faital 15PR400 that has peaked your interest is available in 4 or 8 ohms. The Emi. Legend CA154 is another good choice. Enough top to do justice to most styles but a "warm thumper".

[will33]

Oh....and the Faital just shines in smallish boxes...which the B15 is compared to common "full stack" piled up common 115 cabs which are closer to 4 cu.ft. or close to it. Tolerant of tuning variances too. If you were to choose one for your B15, it would be for it's very nice, smooth and more extended topend sound compared to your Deltas without giving up bottom end to get it.

[JimmyM]

Damn you Will! Got to keep making me want to spend money!

[1958Bassman]

Originally Posted by JimmyM

I don't think I could deal with a driver that only does 3k on the top end. Pretty sure the tweeter picks up at 4k so that would leave a response hole. I'd go Beta or Delta myself if you're looking for a speaker more tolerant of cranking harder that sounds right in Ampeg cabs and won't break the bank. The speaker in it is apparently rated for 150w thermal, which isn't bad and likely lighter than a replacement, but fartout power handling is likely going to be a little less than the head can deliver cleanly. Will the difference add up to a hill of beans for available volume on a gig? That I couldn't tell you but I wouldn't be looking for miracles.

A hole? It's not as if the woofer stops at 3K and the tweeter starts at 4K. If they're each -6dB at 3.5KHz, the response is flat, assuming their curves taper at 6sB/octave. Even if it's 12dB/octave, it's pretty easy to make up the difference but honestly, it's a bass and unless the strings are round-wound, the treble is cranked and the tone controls are wide open, and most of the playing happens in the higher registers, this "hole" will be unnoticeable to almost everyone who doesn't have an RTA.

Personally, I think the OP needs a HP filter. If he uses that, he'll be able to run it hotter, not have to back off the bass control and really dig in. The lowest frequencies are wasting power that could be used to high the level he needs/wants.

[1958Bassman]

Originally Posted by Bass 45

I only use four string basses.

Thank you for the speaker warning though - it makes good sense.

Which driver is in this cabinet? If the tuning is right and you play a lot of double stops, you're producing sub-harmonics and overtones- any time two notes are played at the same time and the amp is being run hard, i.e., running out of headroom, the amp will run into Inter-Modulation distortion and produce not only the notes you want, but also the sum and difference frequencies. If you play low E and B, your fundamentals are 41.2Hz and 64Hz, with the sum of 105.2Hz and difference of 22.6Hz. If you think your cabinet is made to produce anything at 22Hz and do it well, guess again. This is the reason I think ALL bass amps should have a high pass filter. Ever been in a car that competes/competed in sound-off contests? The equalizers, crossovers and amplifiers often have a high pass filter (many times, it's set at 25Hz), so the amp doesn't have to deal with frequencies that are A) inaudible, B) not usable and C) impossible for the drivers to deal with and survive. When I did car audio, I saw a ton of woofers that puked because some nimrod played a CD with stupidly heavy bass that was far below the port tuning. Once you send signals that are below the port tuning, all bets are off and the driver's performance will be far from what you want, paid for and what the manufacturer designed it for. If you run the amp AT clipping, it doesn't mean the distortion is particularly audible. It may sound like "grind", but it's causing things that we can't even hear because they're either being masked by what we CAN hear, or they're just below our hearing limits.

[JimmyM]

I want at least 4k in my woofer in every cab I own, and if I get less, it sounds dark to me. I don't use or like tweeters so I want it to come out of the woofer.

[anderbass]

Originally Posted by Bass 45

Good point about the frequency range - but I am limited to 4 ohm options to match the original. Also, there is no tweeter in this model - so it is important to get some upper frequency response from the woofer.

Hey Rich, I've got a 4-ohm EVM 15B In one of my B100R combos. I think it sounds quite a bit better than my other B100R that still has the stock speaker. You'd be welcome to cruse over and take a listen/compare sometime if you'd like.

[AstroSonic]

The B100R is a well engineered combo amp and a remarkable performer. However, it was made to a budget. Its performance is a result of a unique set of well chosen engineering/performance compromises. Changing drivers will almost inevitably result in a tone that is different from that of the B100R. Adding flared port terminations inside the cab will resolve the chuffing issue at low cost and effort. High pass filtering could also be helpful. Changing C3 (the input coupling cap) to 0.01uf/100v will bring up f3 from about 7Hz to 35Hz (down about 9db at 17Hz). Not as good as a state of the art 3rd or 4th order HPF, but useful, and with minimal cost and modification to the amp.

Not much that can be done about getting the cab's f3 into the low 40's (or even 50's), as long as you stick with a 15 inch driver. The major problem is the limited cab volume (about 1.9cf). I spent a lot of time looking into this and found no 15 inch drivers that will produce deep bass (41Hz within 6db of midband spl) and high efficiency in a cab this small. Hoffman's Iron Law at work. Many drivers will 'work', and will sound 'better' to some, but none with deep bass extension. (Please prove me wrong on this. I would love to upgrade.) The way around this is to take a deep breath, and (OMG!) look into 10 and 12 inch drivers. There are a few that will allow about equal efficiency to stock, but provide a substantially lower f3, with fb in the 40-45Hz range. The overall tone will be different - there is more to cab performance than a low f3 and non-farting Xmax (within the amps power capability). It won't sound like a B100R anymore, but chances are many will find the tone to be an improvement.

For those who want to maintain the tone and overall performance of the B100R, adding interior port flares and some high pass filtering are useful modifications.

[Bass 45]

Originally Posted by 1958Bassman

Which driver is in this cabinet? If the tuning is right and you play a lot of double stops, you're producing sub-harmonics and overtones- any time two notes are played at the same time and the amp is being run hard, i.e., running out of headroom, the amp will run into Inter-Modulation distortion and produce not only the notes you want, but also the sum and difference frequencies. If you play low E and B, your fundamentals are 41.2Hz and 64Hz, with the sum of 105.2Hz and difference of 22.6Hz. If you think your cabinet is made to produce anything at 22Hz and do it well, guess again. This is the reason I think ALL bass amps should have a high pass filter. Ever been in a car that competes/competed in sound-off contests? The equalizers, crossovers and amplifiers often have a high pass filter (many times, it's set at 25Hz), so the amp doesn't have to deal with frequencies that are A) inaudible, B) not usable and C) impossible for the drivers to deal with and survive. When I did car audio, I saw a ton of woofers that puked because some nimrod played a CD with stupidly heavy bass that was far below the port tuning. Once you send signals that are below the port tuning, all bets are off and the driver's performance will be far from what you want, paid for and what the manufacturer designed it for. If you run the amp AT clipping, it doesn't mean the distortion is particularly audible. It may sound like "grind", but it's causing things that we can't even hear because they're either being masked by what we CAN hear, or they're just below our hearing limits.

Thank you for the interesting comments.

The low pass filter is a good idea.

Personally, I am a pretty traditional bass player. I don't usually do double stops or slap or strum - just regular old rest stroke/finger-style.

I have heard what you mean when two loud/low notes are played at the same time - very hard on a speaker.

[Bass 45]

Originally Posted by AstroSonic

The B100R is a well engineered combo amp and a remarkable performer. However, it was made to a budget. Its performance is a result of a unique set of well chosen engineering/performance compromises. Changing drivers will almost inevitably result in a tone that is different from that of the B100R. Adding flared port terminations inside the cab will resolve the chuffing issue at low cost and effort. High pass filtering could also be helpful. Changing C3 (the input coupling cap) to 0.01uf/100v will bring up f3 from about 7Hz to 35Hz (down about 9db at 17Hz). Not as good as a state of the art 3rd or 4th order HPF, but useful, and with minimal cost and modification to the amp.

Not much that can be done about getting the cab's f3 into the low 40's (or even 50's), as long as you stick with a 15 inch driver. The major problem is the limited cab volume (about 1.9cf). I spent a lot of time looking into this and found no 15 inch drivers that will produce deep bass (41Hz within 6db of midband spl) and high efficiency in a cab this small. Hoffman's Iron Law at work. Many drivers will 'work', and will sound 'better' to some, but none with deep bass extension. (Please prove me wrong on this. I would love to upgrade.) The way around this is to take a deep breath, and (OMG!) look into 10 and 12 inch drivers. There are a few that will allow about equal efficiency to stock, but provide a substantially lower f3, with fb in the 40-45Hz range. The overall tone will be different - there is more to cab performance than a low f3 and non-farting Xmax (within the amps power capability). It won't sound like a B100R anymore, but chances are many will find the tone to be an improvement.

For those who want to maintain the tone and overall performance of the B100R, adding interior port flares and some high pass filtering are useful modifications.

All very insightful stuff there!

That would be very cool if someone found the perfect 12" neo with a large Xmax that would make the B100R an even more impressive sounding and portable combo. Heck - then there would be space for a horn too!

Someone else besides me is going to have to do it first though. I recently sold my PF500/115HE and then purchased my B100R so I could pay bills with the $ difference (gigs have been a little slow lately)

[Bass 45]

Originally Posted by anderbass

Hey Rich, I've got a 4-ohm EVM 15B In one of my B100R combos. I think it sounds quite a bit better than my other B100R that still has the stock speaker. You'd be welcome to cruse over and take a listen/compare sometime if you'd like.

Sounds like a plan. I'll give you a ring soon.

[Bass 45]

Well, I finally had a chance to tinker with my B100R yesterday - and it seems I have remedied the chuffing problem.

It turns out that the undesired sound was coming through the 3/8" speaker wire hole between the cab and the amp chassis. This somewhat unidirectional sound was coming out the back and I had assumed it was coming from the ports.

I used a silicon based caulk to plug the hole and let it sit overnight and the combo sounds fine now.

I have no idea what change occurred to make the chuffing sound start a few weeks back. There was no evidence of the speaker wire hole being plugged before - but I suppose there could have been something in there that fell out.

While I had the speaker out yesterday, I figured I would try a 1970 CTS four ohm speaker that I had hanging around. The speaker has a ribbed cone and an aluminum dust cap. I believe it was originally mounted in a solid state Leslie cab.

The CTS sounds great in there - very much like the original - and it looks cool with the aluminum dust cap It really can kick out the lows - and it sounds clear. It difficult to point out any differences without being able to compare the CTS with the original Eminence side by side - but I thought I would mention it in case anybody needed a cheap replacement (there are often people selling these on Ebay).

Thanks again everybody for all the insightful input!