[cryingday]

I was doing a google search on how to repair my velodyne ct 150 when I came across a post on this forum. I'm a newb when it comes to DIY projects so I'm wondering how easy or complicated it is to replace the built in amp.

The person who replied suggested using a 300W BASH® Subwoofer Amplifier from oaudio. This got me to thinking in a more is better sort of way. Could I get away with using a more powerful amplifier, say a 500w? If so are there any pitfalls or warnings I need to be aware of, like setting my carpets on fire?

Thanks for your help in advance.

Cryingday

 

[fbov]

I'm seeing two issues:
- form factor
- feedback.

There are many choices in the 200-300W range for plate amps intended for subwoofers. I can just about guarantee that none of them will be a drop-in replacement, and I will guarantee that none are equipped to interface with Velodyne's feedback circuit. You will find a lot with similar features, but this is a fairly old product line, so its features may not be commonly needed anymore (thinking filtered main speaker outs here).

That said, the sub will likely work without the feedback loop connected, and if you have basic woodworking skills, it's not hard to fill the old amp cut-out and cut a new one. The BASH amps (both PE and O-audio) are good, but PE's 250W is a close match to what you had. What it comes down to is the relative features... if you use speaker level signal as the input, you need speaker level inputs for example. Many people do all their filtering on the AVR and bypass the amp internal filters, making a filter bypass important. You get the idea....

I was planning to link to choices from PArts Express, but their web site has a problem with slow/no response to simple things like sort requests...

Have fun,
frank

 

[Mike P.]

The CT 150 is a sealed design and chances are the original amp had some degree of boost in the 30 hz range. Since the measured response of the sub starts to drop off at 25 hz a replacement amp is going to need a sub sonic filter in the mid 20 hz range. The Bash 300 is up to the task if you're willing to change 2 resistors. The amps default subsonic filter is 17.7hz but it can be changed to 25 hz wth 2 db of boost in the 31-35 hz range.

With the sub being 15 years old I would not recommend a 500 watt amp.

 

[cryingday]

Thanks for the quick reply gents.

Frank,
I tried looking over parts expresses replacement plates in the 250w range and they were all discontinued. The closest that I could find was the Dayton Audio MCA2250E 2.1 Channel Class D Plate Amplifier. Am I missing something?


Mike,
Thanks for the heads up against going 500w. It was just a passing thought, lol. How hard/dangerous is it for a novice to replace the 2 resistors in the bash 300w you mentioned? I'm trying not get myself killed and am so far succeeding. Barely...

cryingday

 

[Mike P.]

The Bash 300 would be your only option for this sub due to the requirements I previously stated. You would need to find someone experienced with soldering, you don't want to make a mistake and fry the amp.

But first things first. Since the sub is old, what shape is the drivers surround in? Is it showing any signs of deterioration?

 

[cryingday]

Hi Mike.

First thanks for your help. I have only taken the subwoofer in to a local repair shop and their diagnosis was that the amp has gone bad. Since, they asked me how to spell Velodyne, it doesn't give me a lot of confidence in their work so I took back possession of the CT-150.

I know someone who's very well versed with the use of a soldering iron so no problems on that front.

As far as what shape the drivers are in, I don't know. I can remove the amp plate any time and check. As far as I could tell from what the repair shop explained to me when they took a look at the subwoofer, everything looked good.

What should I look for when I remove the amp plate? If there is any deterioration, what would be some obvious signs?

Again thanks for helping out a complete newb.

Day

P.S. I was looking through Parts Express and found Yung SD300-6 300W Class D Subwoofer Amp Module with 6 dB @ 30 Hz and Yung SD300 300W Class D Subwoofer Amp Module No Boost. Could I use the Yung SD300 with 6db @30Hz boost? Or is the one without boost better for someone w/ almost no experience soldering stuff?

 

[Wardsweb]

Pull the grill off and take a look at the surround. Is it intact?

As for Parts Express, I think the SPA250 or the SD300-6 may be options. I've re-routered subs before to retrofit plate amps.

Where are you in Texas? I have a M&K V1B 12 just sitting here.

 

[cryingday]

Hi Wardsweb. Glad to see a fellow Texan here.

I'm, unfortunately for the purposes of this thread, in Ft. Worth.

I pulled off the front grill and found the surround in perfect order. I'm such a new member to this forum that I don't know if I can post a picture of what I see. To clarify as best as I can without pictures, I see a round, 1/2 dome in the center of the front face. It has no/zero dents and the surrounding area is smooth as well.

From what I see of the subwoofer's exterior and from what the repair shop told me when I tried to get them to repair my subwoofer, I believe that the problem lies with the built in amp. When I bought the thing 10 years or so ago, I connected it to my home theater receiver and let it sit. I've hardly ever moved it so the exterior is about as pristine as can be.

Thanks for your help.

Day

edit 11/06/12
While browsing through Mike P.'s sig links, I found a picture that best describes what I saw when I took off the front grill. It's in post #29, picture #2 of this thread : http://www.hometheatershack.com/forums/creative-sound-solutions/5774-dual-sdx15-project-3.html

 

[Mike P.]

As for Parts Express, I think the SPA250 or the SD300-6 may be options.

The HPF's on both those amps could be an issue with the CT 150. At least the Bash ampvcan be modified for a specific frequency.

 

[Wardsweb]

The HPF's on both those amps could be an issue with the CT 150. At least the Bash ampvcan be modified for a specific frequency.

My bad, I stand corrected.

 

[bgarcia17]

The CT 150 is a sealed design and chances are the original amp had some degree of boost in the 30 hz range. Since the measured response of the sub starts to drop off at 25 hz a replacement amp is going to need a sub sonic filter in the mid 20 hz range. The Bash 300 is up to the task if you're willing to change 2 resistors. The amps default subsonic filter is 17.7hz but it can be changed to 25 hz wth 2 db of boost in the 31-35 hz range.

With the sub being 15 years old I would not recommend a 500 watt amp.

My search shows this to be a vented design, and the amp does employ some type of feedback to reduce distortion. I suggest a search for an exact replacement on ebay, or contact Velodyne for repair. They may charge you a flat rate which may be cheaper than a decent replacement.

 

[Mike P.]

Yes, you are correct, an image shows a slot port. Strange the OP never mentioned the fact when I said it was sealed. Regardless, I would still recommend the Bash amp with a modified HPF for a replacement.

 

[exm]

I am not sure if it's possible for this model, I just want to point OP to my thread where I actually disabled the plate amp and used an external amp for my Kef subwoofer.

 

[cryingday]

Let me see if I understood you both correctly:

I should go with the Bash amp because it can be modded to fix/fit any problems specific to the CT150? That way I don't waste money on an amp that I can't use?

Thanks so much for being very patient with my noobness.

Day

 

[bgarcia17]

The BASH amp is good because it's easy to mod if needed. Being that this is a ported sub, it would be good to know what the tuning frequency is. That's a good place to start for the amp mods.

I saw a post where some guy powered this sub with an external amp when his amp died, and he was happy with the results. So I don't think you lose much by not having the distortion-reducing feedback.

Have you checked with Velodyne just to see if it's possible to repair your amp, and what the cost would be?

 

[Mike P.]

The BASH amp is good because it's easy to mod if needed. Being that this is a ported sub, it would be good to know what the tuning frequency is. That's a good place to start for the amp mods.

Agreed. If you could tell us the internal width, height, and length of the port it would be a tremendous help.

 

[cryingday]

Hi bgarcia17! Welcome to the discussion.

I'm very curious where you read about someone powering his CT150 with an external amp. I like to keep my options open.

I did indeed inquire with Velodyne as to how much to repair my sub. The quote I received was $230 to service the amp, $406 + shipping for a replacement amp. And now you know why I'm on this forum seeking advice.

I will get cracking on getting the measurements. Please advise me where to start the measurements. I assume you want me to remove the amp (i.e. Unscrew it) from the cabinet and measure the amp's dimensions. I could also, to the best of my abilities, try to measure the remaining room within the enclosure.

As always, thanks for your help.

Day

 

[mlc3i788]

My Understanding is the port is tuned to 25 HZ is there still a need to change the resistors? Im in a similar situation.

 

[Mike P.]

Are you sure it's 25 hz? have you measured the dimensions of the port?

 

[mlc3i788]

Well I actually pulled that off some specs on the web but i can measure it when i get home. I now have a bash 300 and the box for the CT-150. Looks like i'm going to need a new driver as well. Any ideas for something below $200.