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SDL-5 Conversion Need some input

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Johnny Mc Combs:
Hi Guys, I have a pair of Servo Drive Loudspeakers SDL-5. Some years ago, I sank a few hundred bucks into making one of them run again. I was never as happy with the rebuild as I was with the original sound. I should have replaced the motors too. Now I am thinking about gutting the servo system from the cabinet. The limited space behind the 15" servo baskets makes it nearly impossible to replace them with traditional 15" drivers. However, I might be able to fit a pair of Lab 12 drivers in the same configuration as the OEM 15"s. To be honest, I don't want to spend the money on the 12's just to play a guessing game. I do not have any computer programs to plug the info into. I will be more than willing to drag one of these monsters out of storage to get measurements on the box if some one would be willing to help with a projected outcome of the project. Truth be known, someone out there has probably had this idea before. If so, how did it sound?

Art Welter:

--- Quote from: Johnny Mc Combs on March 15, 2011, 04:11:18 PM ---Hi Guys, I have a pair of Servo Drive Loudspeakers SDL-5. Some years ago, I sank a few hundred bucks into making one of them run again. I was never as happy with the rebuild as I was with the original sound. I should have replaced the motors too. Now I am thinking about gutting the servo system from the cabinet. The limited space behind the 15" servo baskets makes it nearly impossible to replace them with traditional 15" drivers. However, I might be able to fit a pair of Lab 12 drivers in the same configuration as the OEM 15"s. To be honest, I don't want to spend the money on the 12's just to play a guessing game. I do not have any computer programs to plug the info into. I will be more than willing to drag one of these monsters out of storage to get measurements on the box if some one would be willing to help with a projected outcome of the project. Truth be known, someone out there has probably had this idea before. If so, how did it sound?

--- End quote ---
I replaced the servo-drive assembly with EV150X speakers in a smaller SDL cabinet, it sounded fine, though I never heard the original cabinet before the disco had blown it up so have no direct comparison.

Lab 12s should work better than the EV150X (there were not made when I did the swap around 1991), but they will have a bit of the "droop" between 35 to 60 Hz like the Labsub.

Johnny Mc Combs:

--- Quote from: Art Welter on March 15, 2011, 04:43:46 PM ---I replaced the servo-drive assembly with EV150X speakers in a smaller SDL cabinet, it sounded fine, though I never heard the original cabinet before the disco had blown it up so have no direct comparison.

Lab 12s should work better than the EV150X (there were not made when I did the swap around 1991), but they will have a bit of the "droop" between 35 to 60 Hz like the Labsub.

--- End quote ---

Understand that I have never heard the  LAB 12. But all reports I have read say a LAB 12 cab has the equivalent out put of 4-8 traditional 18's. Is this true? (I know, it depends on the brand/model/config)
Also, define "droop". Thanx for the input

Art Welter:

--- Quote from: Johnny Mc Combs on March 15, 2011, 04:57:19 PM ---
--- Quote from: Art Welter on March 15, 2011, 04:43:46 PM ---I replaced the servo-drive assembly with EV150X speakers in a smaller SDL cabinet, it sounded fine, though I never heard the original cabinet before the disco had blown it up so have no direct comparison.

Lab 12s should work better than the EV150X (there were not made when I did the swap around 1991), but they will have a bit of the "droop" between 35 to 60 Hz like the Labsub.

--- End quote ---

Understand that I have never heard the  LAB 12. But all reports I have read say a LAB 12 cab has the equivalent out put of 4-8 traditional 18's. Is this true? (I know, it depends on the brand/model/config)
Also, define "droop". Thanx for the input

--- End quote ---
If the "traditional" 18 had very small Xmax, it is possible a Lab sub could put out as much LF as eight 18".

I have found four small dual Lab 12 ported cabinets (about the size of one Lab Sub) could put out more 40 Hz level than 8 Meyers 650P dual 18" cabinets.

The LabSub has slightly less output in the 35 to 60 Hz range than it does below and above, on a chart it looks like it is lower in that area, a "drooping" response.

Antone Atmarama Bajor:
You may try taking some measurments, and try to model the SD-5 in HornRESP thats a free Program.

David McBean comments on DIYAUDIO.COM and updates frequently.

Some one on DIY audio may also be able to help with some suggestions on how to model.

There is also AKABAK which is a free program but has a sort of steep learning curve, but is less limited than Horn Resp.

I think the Trick is getting the appropriate throat loading and rear chamber volume to fit in the box and give the driver surround enough room to not hit anything.

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