Subwoofer Amp Recommendations

I've added a stereo pair of VBT Magellan passive subs (fantastic, BTW)to my 2-channel system. VBT recommends using their 200S amp, which I have---and it is good---and I could get another for stereo, but as I'm using a Tact 2.2x, I don't need the crossover/volume functions in their amp, and would rather not have to put the signal through another set of electronics.

My considerations have ranged from the new Carver Pro amps (but I'm not happy about their connections as I'd need new cables or adapters) to used Adcoms/NADs/Aragons. I've also considered PS Audio and Sunfire, but not sure if I need to spend that much just for a bass amp.

A friend suggested the new Panasonic 45 digital receiver which takes a digital input (saving me the expense of a DAC, but I already have an extra anyway).

Your thoughts and experience would be appreciated.
I don't understand why a Carver amp would be a problem with connections. Pls explain details.
I'm using one channel of an older 250wpc Bryston 4B to drive my 12" NHT subwoofer and it's much better than the NHT SA-3 amp/crossover made for it.

If your amp is like the Carver Pro PM700/1200 which use XLR and 1/4" TRS input jacks for PA and guitar set ups and you only have RCA cables, you could get XLR to RCA adapters for it and avoid buying new cables.

Something like the NAD 208 might good as well.
If Aragon is in your list, dont even consider the others, I feel Carver and NAD are poor choices to even consider. Aragons are truely flat to 5hz with a great damping factor and excellent slew rate. Their design is also top notch and they are also a great amp to upgrade internally too if you ever felt the need. 8008BB or Palladium's would be the top 2 choices, both are balanced designs and accept xlr inputs. Palladium's are incredible amplifiers and excellent bass module amps being fully stable at any impedance load. And they actually put out more than their conservatively rated power fullbandwidth, both channels driven with very low THD and TIM.
Both the Talon ROC AK and Thunderbird models (the t'Bird is about $12,000 delivered with the amp) come with the new Crown CTs-600 amp with IQ-PIP interface card. This amp is digital, and has a parametric EQ built-in that you connect to and program with your PC (via TCPIP connectivity, like your Internet connection). It is a very small form-factor (19 x 3.5 x 14), rack-mountable design.

I just ordered a ROC AK, and have talked to Mike Farnsworth about this sub amp. He is very complementary of it. He has used the Crown analog 'car-battery' style amps for his subwoofers for years, and feels that this is the best so far.

The only concern I have about it is that it is fan-cooled (potential noise), though the fan speed can be programmed to vary based on thermal demand, so they probably do not run much at idle. The plus-side of this fan cooling is there is NO top-to-bottom ventilation needs, so you can stack them tightly in a rack without providing any vertical clearance.

We'll see how it sounds....
Ritteri...Why is slew rate meaningful for a SW amp? Is "flat to 5 Hz" really significant? If so, I suggest a Kenwood LO7M, or other DC coupled amp, which is flat to DC.
Cheap older amps simply won't cut it! Buy a pair of Janis 1/a's on ebay for $350/pair. Only 100 watts but clean and powerful down to the last octave. Your old carver will just muddy up things in the upper bass region and never get down to the 20-50hz region.
Slew rate is very important in my book. It has to do with the dynamic ability of an amplifier and how quickly it responds to sudden changes in signal.

Being flat down to DC I feel also is a good indication to of how well an amplifier can reporduce low frequency signals. Many amplifiers in the bottom of the frequency spectrum slope off in the last octave slightly giving a "dry" thin sound. But I have found that amps that can reproduce a flat signal down to DC basically have much better detailed bass that is rich sounding.

And just because an amplifier is rated to respond down to DC doesnt mean it can reproduce the signal in a linear fashion.

I personally wouldnt suggest an amp thats 25 years old btw. My father had an old pair of those he sold about 10 years back. Nothing special at all.
Ritteri...My point about slew rate is that a subwoofer signal does not involve any "sudden changes", so the ability of an amp to track such changes is immaterial.

The Kenwood LO7M is a true DC amp, with not a single capacitor in the signal path. If you put a steady voltage on the input, say +0.1vdc you will get a steady voltage say +20vdc, at the output. It is truly linear down to DC, unlike the Aragon which you say rolls off (probably minus 3dB) at 5 Hz.

Is response only to 5Hz adequate? Sure, but you are the one who raised the issue of bandwidth below 20 Hz. I am sure that your Aragon is a very fine amp, but its virtues would be wasted driving a subwoofer.
... for a description of damping factor and how it works try:
I'll second Eldartford's recommendation of the Kenwood L-07M. If you've never heard these as bass amps, you should. Absolutely fantastic!
Elgordo..."One man right (or even two men) is a majority of one". In their day the LO7M were considered the best. By now they are all well burned in...and still working!

I have the service manual if anyone is interested. They are flat from DC to 50 Khz +0 -0.5 dB, and to 100KHz +0 -1dB.
Not too shabby.
Not too shabby on paper, but the Kenwoods had problem with induced noise and had a very poor quality control on their mfg. tolerances. Kenwood=cold solderjoint problems. And an amp thats 25+ years old isnt going to get any better. If they were truely that great, they would still be making them, or something that resembled their original design concept.

BTW slew rate is just as importnat for a bass as it is for midrange or treble. I personally like detailed bass that integrates seamlessly into the rest of the audio spectrum. Its a given fact that alot of amps with low slew rates have muddy bass in comparison.
Ritteri...I guess I must be lucky to have no noise problems or QC defects. (Many, many excellent products are no longer made. There is another thread about this).

I don't think that you can explain the need for high slew rate when processing a signal that has no steep wavefronts. Any rapid signal change has been routed to another amplifier by the crossover. If your SW amplifier did output a rapidly changing voltage (characteristic of midrange or tweeter signals) your Subwoofer driver would not respond anyway.
Buy the Adcom GFA555 mkII in the amp section of the Gon for 350.00.Tons of power and quiet.I use two in bridged mode on my Adire Tumults.
My brother's L-07Ms keep powering his subs year after after year with no problems and they run cool. Of course if one lives in wicked cold New Hampshire a warmer running amp is welcome.
I also think response to DC is important. I have an SVS 20-39CS passive sub. I've tried both a Tandberg 3006A (264W/4ohms) and an Aragon 4004MKii (400W/4ohms) driving it. The Tandberg is DC coupled, the Aragon is not. On scenes with subsonic bass, like the depth charges in U571, the Tandberg shook the house a lot better than the Aragon.
In response to the L07M comment, I own four of them and have NEVER had any problems. Coming up on a 35th anniversary, I'de like to see an amplifier beat that.
your choice will depend on how many watts you need. i currently have two ported 15" subs. they like 300 watts at 4 ohms. i am using 2 channels of a 5 channel sherbourn ht amp. i bought this amp cheap and i have 3 spare channels, i plan to add more subs in the future. if your subs are sealed or need eq you will need more watts.
Room size determines the true freq. responce of ANY subwoofer. There fore common sence dictates that SPL will rise as power output rises in a given room. While you may be able to "feel" something below 20Hz, you certainly will not be able to hear it- the human ear is not designed to do such a thing.

But is this always true? Not to my taste.

For Subsonic duties I use two AB International 1100A's bridged mono, for "stereo-bass". Seems to me your question is about subsonic truth to as low a point as you can get. This relys on far more than just an amplifier. Room acoustics, driver design and enclosure, and source material all provide various challenges for any music system and the listener. What some here refer to as "muddy", to another, may be considered "truth", it's all dependant upon your ears, and this is obviously subject to your own personal taste.

True bass IMO requires high SPL, why? Because most average listeners room size is not the same as that of a music hall, hence a greatly reduced standing wave must be made to "perform" the same in a much smaller enviroment- resolution- SPL. Efficient drivers and efficient amplification- your ears will thank you for it, and so will your pocket book.

Ask any sound engineer, when your at your next concert about setting up subs- you'll have to buy the coffee, and have a few hours of time on your hands.
Since this 1.5 year old thread has been revived, I thought I'd update you guys on my progress:

First, I bought another WBT amp (Bash) to run the subs stereo, but wasn't ever quite satisfied. So I bought a Carver Pro (Tripath) amp, which was better, but decided my Bel Canto Evo (borrowed from another system) sounded a bit better--so it stayed.

Sold the VBT amps and the Carver, and still using the Evo (for now--though I must admit I'm still considering an amp with more current at some point--Crown K2, maybe).

But then I realized that although the VBTs were very detailed and pretty extended, they just didn't move enough air for my taste and sounded a bit lean, even with the Tact equalization/room correction.

So I sold them and bought a pair of RBH 1010s (two metal ccone 10" a side). Now, that was more like it. Not quite as detailed, but definitely more air moved and more lively.

I have recently replaced my Talons with Selah Incredarrays (line arrays with 10 Seas excel mids, 8 Fountek ribbons and two Peerless 12" subs). Right now I'm bypassing these subs and still using the RBHs in the corners. I figure the corner-loading and the separate enclosures can't hurt (time-aligned with the Tact) though I'll probably try them both ways when I get a chance.

Pretty happy, but still wondering if for the same $$ as the Evo, I could get better for these subs.

Thanks for all your suggestions.
I have 5 Kenwood L-07M amps driving Revel F30s, M20s, and a C30. The F30s are providing reasonable bass for now (no subs yet). The monoblocks with short 1-meter Kimber 8TC cables deliver power and speed - and the cable layout is pretty clean compared to running miles of beefy speaker cables. It sounds great and is really clean. And reliable. The L-07Ms almost are never powered down - they stay on for weeks at a time, and one of our cats likes to sleep on them during the Winter. So not only are the Kenwoods reliable, but they are slightly abused and still keep on kickin' butt. I've got an L-07T that is still doing duty as well.
As originally posted by Danner

This is a good yet basic explanation of damping factor. Crown fails to mention one important factor. It is impossible to achieve the damping factor figures that they quote without some help from additional circuitry. That circuitry and help comes in the form of negative feedback. The more negative feedback that you use, the lower the output impedance. At the same time though, the more negative feedback that you use, the slower the circuit becomes. That's because there's more "error correction" taking place, which takes longer to process and more time to impliment. This is part of the reason why amps using no or very low negative feedback have slightly soggier bass response, but do SOOOOOO much better at preserving liquidity, transient response and harmonic structure throughout the other frequency regions. That is, compared to a high negative feedback design, which tends to sound dry, brittle and closed-in in comparison.

As far as the frequency response goes, an amp that is DC coupled will always demonstrate better transient response with less ringing. Many people equate bass ringing with greater bass weight, which it is, but it isn't "clean" or "real" bass. It is an artificial distortion or a "error of commission" i.e. signal introduced by a component that can't be found on the recording. On top of that, placing the DC blocking cap in series with the output not only introduces time smear, but also limits current capacity.

The drawback to not having the DC blocking cap is that the amp can leak a MUCH higher level of DC if not properly calibrated and / or if a problem develops. This can smoke ( quite literally ) your speakers*. This can happen extremely rapidly or very slowly, depending on the amount and consistency of DC leakage taking place.

The end result is that one has to choose what type of sonics they want, what type of trade-off's they are willing to accept and then fork over their cash. Sean

* Seeing your woofers light on fire is first extremely shocking and then "kind of cool" after the fact. One of my friends purchased a new bass guitar amp. After hooking it up to his dual 15" cabinet, the speakers literally shot flames out of the dustcaps after a short period of time. The amp was leaking a very high level of DC. After taking the amp back to where he bought it from ( Guitar Center ), they gave him another identical model.

Rather than test the amp at the store, he took this amp back home and hooked it up to one of my bass cabinets that he was borrowing. I guess that they figured that there was no chance of two amps in a row being bad. Instead of lighting the drivers on fire, this one simply sounded very distorted. That's because the DC was producing a steady-state push on the cones, causing it to act as if it was partially "bound up". The reduced excursion capacity of the cone caused the bass to sound "warbled", so they knew something was wrong.

After checking the dustcaps for heat, they found them to be noticeably warm but not smoldering. The second amp was probably putting out slightly less DC voltage AND the drivers in my cabinet were also much more robust than what he was using in his.

My friend then proceeded to return this amp to Guitar Center to get a refund. Guitar Center gave him a hard time about it initially, but gave in when he started talking about filing a lawsuit to seek damages pertaining to the other equipment that was damaged due to their negligence in selling faulty equipment. While he ended up eating the cost to repair his own speakers, he was also conscientious enough to buy me another pair of brand new 18's in case mine were damaged by the heat. While i didn't appreciate him "taking liberties" with my cabinet and a possibly defective amplifier, he obviously thought more of our friendship than i initially gave him credit for.

Between replacing his drivers and mine, that whole "new amp" fiasco ended up costing him about $750 in damaged speakers. A costly mistake on his part that i'm sure he'll never forget. Both in terms of his wallet AND in seeing his speakers light on fire : )

PS... This took place probably 15 years ago and the amps were Gallien-Krueger's. Turns out that the whole production run was defective from what we later found out.

Amazingly enough, I bought a pair of L-05Ms on A'gon a couple of weeks ago, with an eye toward using them to drive my BESL passive subs. I ran across this thread just today...
Sean...The DC blocking capacitor of the typical power amplifier (non-DC-coupled), is at the INPUT, not the output. The only power amplifier that I know of with a series capacitor output is (was) the Dynaco ST120, their first solid state amplifier, the circuit of which resembled "a preamp on steroids".

The output stage of any solid state power amp is DC coupled to the load, and can apply DC to the speaker. A pot is usually provided to trim the DC output down to a few millivolts. An excessive DC output which could damage a speaker would only result from a malfunction of the amplifier.

In the case of a DC coupled amp, dangerous DC output can be generated without any failure of the amplifier, simply by inputing a snall DC voltage. For this reason DC coupled amplifiers, like the Kenwood LO7M tyhpically include a circuit that monitors the output for excessive DC, and shuts it off if necessary. The Kenwood LO7M does this with a relay. Some AC-coupled amplifiers also include such protection...example is my CarverPro ZR1600 digital amplifier.