MY DIY Sub

[micb]

Hi Guys, It has been a while since I have been on here.

I recently took my enclosure orginally designed for my car (I mapped transfer function of ther vehicle then desigened this sub system to match) and brought this box indoors as the response plots showed it would work very well indoors.

It has 2 RE Audio SR 10, which have 18mm linear one way xmax each, I have personally tested these drivers with 1000 WRMS each long term so I know they are up to the job both mechanically and thermally. Each driver is DVC 4 ohm so individual coils are wired in series to 8 ohms and then the pair of drivers wired parallel to a final load of 4 ohms.

The drivers have a low Qts thus do not require big enclosure and sound quite neutral with a nice walmth. The freeair FS is fairly low at 25hz so they do gain from low vent tuning.

The box dimentions are 2.6 cubic foot net, vent is tuned to 25hz, with 37.5 Square inches of port area, the vent is very large this was mainly to ensure vent noise is kept to a minimum and it was good and efficent port under high amounts of power.

I have a BK Elec BSBPV500 - 500 WRMS into 4 ohms so the drivers have 250 WRMS each.

How does it sound?

Well I really like the sound, music is clean, films wobble in the right places, my room is small and there is plenty of bass across the range.

From ear there is a shallow small roll off below tuning point, I have yet to hook up a SPL meter or REW etc to check the response. I do know that I played 16hz played loud the old wood door next to my room was moving back and forth and there was a lot of pressure in the room. A quick check of the SPL meter showd uncorrected in room level of 100db @16hz.

I think this will keep my bass fix needs happy for a while.

You can see in the pics I had a small sealed version with single driver, 1.0 cubic foot, Qtc of 0.62 and 500 WRMS, this sounded very good but is far less efficent (at least 6db measured).

It just goes to show keeping power the same but doubling cone area, box size and adding a low tuned vent really makes a difference in output.

Enclosure - Ford Orion Green hehe.


Amp.



Amp internals.



Beefy tord!

[pjpoes]

This is really a separate issue but I would be suspicious of the 16hz spl you mentioned. Typically at those frequencies the harmonics of the tone are what you are actually measuring. Especially given your tuning frequency. At 16hz the cone would be completely out of control and the woofers would be massively exceeding their xmax at that level. Then you have the spl meter itself, most do not measure 16hz very accurately. You really need to get a frequency response measurement of 16hz, and see what that looks like. You might find that there is doubling going on and is much higher frequency.

Otherwise, good work, looks nice. I like the amp, I saw one used on ebay once and debated for a while buying it. They look like really well made subwoofer amps. I wish they were more readily available here in the states.

[micb]

Originally posted by pjpoes
This is really a separate issue but I would be suspicious of the 16hz spl you mentioned. Typically at those frequencies the harmonics of the tone are what you are actually measuring. Especially given your tuning frequency. At 16hz the cone would be completely out of control and the woofers would be massively exceeding their xmax at that level. Then you have the spl meter itself, most do not measure 16hz very accurately. You really need to get a frequency response measurement of 16hz, and see what that looks like. You might find that there is doubling going on and is much higher frequency.

Otherwise, good work, looks nice. I like the amp, I saw one used on ebay once and debated for a while buying it. They look like really well made subwoofer amps. I wish they were more readily available here in the states.

Thanks for you reply.

Yes it likely some of the 16hz I could hear/feel is from the 32hz and 48hz harmonics above. I mean to get REW and see how it plots with a decent flat mic sometime.

The drivers are not near their excursion limits with ~250 watts each even below 25hz, the port roll off is actually surprisingly slow. I mainly think this is to do with the size of box with the vent so long and big. With 37.5 SQ ins of vent area, 55.5 inches long it is 1.25 cubic foot (~55 inches) i.e. almost as big as half the of the net enclosure airspace 2.6 cubic foot. It has quite a wide bandwidth from testing.

I used to run this enclosure in car with 500 WRMS per driver and I could play 18hz sine waves very close to flat out without hitting the driver limits. I'm bearly tickling it at home in comparrison.

What is really nice about the amp is the crossover it sounds great! I have had other plate amps and other active crossover in the past and they did not sound as good as this they were always too shallow for my tastes.