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Author Topic: Servo-Drive Bass Tech 7 ?  (Read 24048 times)

Adam Mottley

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Servo-Drive Bass Tech 7 ?
« on: October 07, 2005, 09:21:41 am »

Hi guys,

What are the perils of buying these cabs used ? Four of these cabs are avalible locally for a great price. Reviews here on the LAB seem positive. What are the maintenance needs/pitfalls of the Servo system ?

Thanks,

Adam
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Tim Duffin

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Re: Servo-Drive Bass Tech 7 ?
« Reply #1 on: October 08, 2005, 01:35:45 am »

well..

1.  The first thing is that they are often too loud and people dont like them because they have very little distortion. Most customers are accustomed to cone breakup, intermodulation distortion, cabinet resonances and bleed to the rear of the sub, something which servodrives do not ever do. This being the case, I dont make much money from them because there is no demand except at HUGE shows where people can be seen fainting in front of them.

2.  The belts need to be replaced after they are worn (no big deal)

3.  I recently had one of the rubber plugs pull out from the center of the cone and punch a hole in the surround--little duct tape and a big fender washer fixed that one.

4.  I honestly do not know how much another entire module costs if one "lets the smoke out" of the motor assembly.  I have been told its ridiculously expensive.

5. They are heavier than you think.

6. other than that-- have fun, the spec of 150Db peak at 60Hz is no joke--they are very uncomfortable at that level.

T

Adam Mottley

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Re: Servo-Drive Bass Tech 7 ?
« Reply #2 on: October 08, 2005, 03:21:50 am »

Tim,

Yes, you are right about them being loud. I used to work a large club in southeast Alabama that had Servodrives powered with Crest amplification. Very large room (about the size of a small gym) and no issues with the "not enough bass" syndrome.

The reason for the post is that these cabs are priced riduculously inexpensive. They are at a reputable dealer, so I would *think* they are ok, serviceablity-wise. They look decent cosmetically (some normal scuff/scratches), but I have not powered them up. There are four cabs up for sale. $495 USD each.

I thought they would be a good set of subs to have around when doing larger outdoor shows, instead of front-loaded 2x18 cabs. The price makes it feasible to let them sit idle when not in use.

Any tips on what to look for in a Servodrive that's "just about gone" (major overhaul) or one that needs minor servicing (belts) ?

Thanks for the information.

Adam
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Timmahh

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Re: Servo-Drive Bass Tech 7 ?
« Reply #3 on: October 09, 2005, 09:47:39 am »

Adam, if you do a search of the forums, you ll find many previous post on them,  You may want to try to look for Servo Johns post. seems to me hes very mucy up on them.  for 500 each, if they dont need a major overhaul, how could you go wrong.  good luck and great base.
Timmahh
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The Guy

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Re: Servo-Drive Bass Tech 7 ?
« Reply #4 on: October 09, 2005, 11:30:43 am »

Adam,

For the VLF stuff there is nothing out there that will touch them.  Make sure your full range setup is up to snuff!  They are a SUB, not a bass cabinet.  The BT7's lack "punch" but have more "woof" than can be imagined.

Another note:  they do not need a ton of power.  When I mixed on a set, they were being powered by a Crown 1200, one box per channel.  If you try and power them like a conventional sub (i.e. 5000VZ, LAB, 9001, etc) you will let the smoke out for sure.  They don't let you know when they're out of gas.  I've heard its easy to break belts/burn up motors this way.

For $500 each, if they work, buy them NOW.

-JB
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Ivan Beaver

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Re: Servo-Drive Bass Tech 7 ?-SDL5's
« Reply #5 on: October 09, 2005, 03:22:46 pm »

Jim is right about the power.  I had some of the early SDL-5's-the predicessor to the BT7's. It was without a doubt the worst money I have ever spent in audio.  I spent more money on keeping them working than I did for the cabinets New!  The BT7's have a different drive system than the SDL 5's-so the timing belt problems are not an issue any more.  I started powering mine with a Crest 8001.  I had a couple of problems.  With just 1 per side I would overheat the amp and shut it down.  These things are a heck of a load on an amp.  When I solved the cooling issue by force cooling the amp, I would tear up timing belts and tear up the rotary to liner drive system with to much power-I even tore up a couple of cones.

I switched to Crown 2400's.  The sound difference was amazing, with the Crown winning out.  With my other bass cabinets (2x18") the sound quality was very close-so as not to be noticed-but with the servo's the difference was HUGE!.  The crowns also overheated (1 cabinet per side of the amp) and I solved the cooling issue with them also-and they still tore up cabinets-just not as fast-even with the PIP-CLP card in the amp and a front end compressor.  The Crown MA1200 is probably the best choice for the cabinets-powerwise and sound wise.

Don't get me wrong-when those cabinets were working-they were amazing-I just couldn't keep then working long enough.  THe BT7's go lower (due to a different horn design-The SDL5's were a W cabinet and the Bt7'S are basically a bent horn.

I later found out from Tom Danley that during the time I was having the problems, they were having problems with the manufacturer not making the belts to their spec.  A lot fo good that did me-I did not get any warranty work (I did not ask for any) and spent many thousands of dollars fixing them.

Those problems are worked out with the BT7s.  I imagine that they are still quite a load on an amp.
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Antone Atmarama Bajor

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Re: Servo-Drive Bass Tech 7 ?-SDL5's
« Reply #6 on: October 09, 2005, 06:18:55 pm »

     I have 4 Of them.  The only problem I have had with amps overheating trying to run them at 2 Ohms.  I've been powering them with a pair of CARVIN DCM 1500's  That gives me 500Watts a cab.  Limiters off as I have found the limiters are not properly calibrated and limit asymmetrical from channel to channel.

    Limiters are not recommended with BT7's anyhow.  It is important to not allow your amplifiers to clip with the BT7's.

 Even if you have a nice steep low pass filter crossing over the Subs Clipping the Amps generates High frequency harmonics.  As I understand it the belts and motor can't really react to very fast rise times so they start slipping cause belt friction and overheat really quick.

    So Clipping amps not good.  Hard clipping amps really really bad for the BT7s.

     If you get a chance to audition the BT7's I suggest PIMP by 50cent and Get Low By Li'l John and the Yin Yang Twins.  Both of them have some nice bass tones in the Low 30Hz'region.

    If anyone else has any suggestions for audition material there isn't that much music produced with much bellow 40 or 50Hz.

    You are getting a steal if you can get them for that much a box, regardless of the condition of the module ~1800$.  If you pass let me know I might want to buy them.

Antone-

   
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John Halliburton

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Re: Servo-Drive Bass Tech 7 ?-SDL5's
« Reply #7 on: October 09, 2005, 08:51:58 pm »

First, the Basstech 7 is rated at 400watts continuous, 800watts peak.  A 500 watt amp at 2ohms load is not what I would consider good.  I don't want to sound mean, I'm just trying to make a real world recommendation.  Switching to something like a Macrotech 2400, where you have one Basstech on each channel would be much healthier, and probably sound a bunch better.
To JimB's comments about not having a lot of punch(kick drum in the 70hz region is how I interpret that), I've not had that problem-I think the fact they have a lower cutoff than many other subs causes the balance of the sub to sound "different", and the lower distortion output probably contributes as well.
By the way, the 400 watt continuous rating is long term, pink noise, 30-100hz.  We used to hook them up in the "death room"(and believe me, that was aptly named), and the last time we tested any went 30 hours straight.  We stopped because we were tired of hearing it, even with a 30db drop outside of the "death room".

Best regards,

John Halliburton
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Chris Davis

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Re: Servo-Drive Bass Tech 7 ?
« Reply #8 on: October 09, 2005, 10:45:30 pm »

I have a couple and I have a friend who has a couple.  We kind of feed off each other in terms of equipment buying decisions.  Two of them placed together are bay-yad. Cool To this date we have not made a cluster of 4 because...a)we hardly see each other and b)there has never been any reason to. Shocked

Chris
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Antone Atmarama Bajor

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Re: Servo-Drive Bass Tech 7 ?-SDL5's
« Reply #9 on: October 10, 2005, 03:12:07 am »

I only ran the BT7's at 2Ohms once  @ 375Watts per cab.  We didn't have another amp at the time.  I run the BT7's with 500 Watts per cab.  No problems yet.

    The BT7 are rated at 800Watts "Peak RMS" for 15 Seconds
I think 500 is prety safe if I never run into clipping or heavy limiting.

Antone-
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