Subwoofer Amp Recommendations

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

http://www.crownaudio.com/pdf/amps/damping%20factor.pdf

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
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* 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.