Adire: voice coil wiring / PE Amp: 'rumble filter' (1 Viewer)

[Adam.Heckman]

First question for the experienced:

Could anyone post a picture of how to wire the DVCs on the Tempest in parrallel? I just got mine, made the box, mounted the 250W PE amp and I thought I wired the voice coils correctly, but every time I tried it, nothing happened. Odd. If somebody could include some pictures detailing how it's done correctly, I'd appreciate it! (BTW, it runs great with only one VC wired up. However, I'd like the extra power of halved resistance.)

Also:

As mentioned, I purchased the PE 250W plate and I was wondering what the high-pass on it was. I ran some signal sweeps to the speaker and I was wondering what frequency they rolled it off at.

Any and all help on either of the questions is greatly appreciated!!

Oh, and even though it's on one voice coil... the sub is AMAZING. I made a sealed mid-q mdf box. Incredible.

 

[Patrick Sun]

Just connect to one set of voice coils as you have done.

Next, just run a piece of wire from the already wired voice coil's positive connector to the other voice coil's positive connector. If you'll notice with voice coil has 2 sets of connectors for each voice coil, this makes easy to connect the other voice coil in series or parallel.

Then, just run a piece of wire from the already wired voice coil's negative connector to the other voice coil's negative connector.

That accomplishes parallelling the voice coils.

If you heard nothing previous, you criss-crossed the connections (positive to negative, negative to positive) and it resulted in the voice coil's operating exactly out of phase (one voice coil is going in, while the other voice coil is going out, thus negating any movement from the driver's cone).

 

[Chad Kuypers]

This is the measured frequency response of the 300-794 that many people use. You might be surprised:

http://www.mfk-projects.com/images/SUBFREQ.gif

Hope this helps.

 

[Ryan Schnacke]

Are you sure that's not the 300-796? It sure looks like it's got 4-5dB of boost at 31Hz which is exactly what the 300-796's rumble filter will give you. In fact, if you check out the graph that PE provides for the 300-796 (look under specifications -> manufacturer's specifications, last page) you'll see that it looks almost exactly like the graph linked above.

The PE graph for the 300-794 looks very different. Much flatter, as you might expect. It has a Q=0.71 alignment (no boost) and a corner frequency of 19.4Hz if I remember correctly. I've created an Excel spreadsheet that calculates these values for the Sallen-Key filter that's used in the 300-79X series of plate amps. I'm happy to share it if anyone's interested.

 

[Chad Kuypers]

Yes. Take a look here at the page that appears before the measurement above:

http://www.mfk-projects.com/dpl_12_measurements.htm

There also used to be another website that measured this amplifier and had pretty much the same graph. It had posted resistor values to flatten the frequency response. That website is no longer up, and I don't remember the values. I stopped using these amplifiers for ported enclosures when I read about this information at the site.

My old computer that ran my LMS software died last week. I am getting a great new computer that should be here sometime next week. When it arrives, I will reinstall my LinearX software and take some measurements of that amplifier. I have a couple of them laying around here somewhere, so hopefully I can find out for sure!

 

[Michael R Price]

Yeah, I thought the 300-794 used to ship with the EQ boost by default, and now they ship it with no boost (20Hz rolloff)? I wish there was an easy to way to just bypass the rumble filter and crossover altogether.

 

[Adam.Heckman]

Thanks everyone for the input. I have the sub up and running on dual voice coils, and it's now calibrated to my system which really tamed it. I watched Matrix Revolutions without calibrating and I darn near shook the walls down. However, it blends much better now and sounds so much more natural. Haven't tried music yet.
This weekend I'll be creating a CD of tones and measuring them to see the response of the speaker. However, I'm using the Radio Shack analog SPL meter. I have heard that this isn't too accurate under a certain freqency. Is this true? And if so, is there any way to measure the sub within a college student budget?

Thanks, again, everyone.

 

[DarrenK]

Hi,

Regarding the frequency plot that was posted of the plate amp. That response curve is for what is the #300-796 amplifier, which is the one with the bass boost.

Back in the day, we only sold one version of the amplifier, and it had bass boost on it, and its part number was #300-794. Then we started shipping the same amp without any boost. Hence, we brought the boosted version back in as a separate part number. However, its been probably over 3 years since we made the transition, and the current #300-794 does not have the boost. So, if this guy has had the amplifier around for a while, then his measurements may be accurate, but they don't reflect the current stock of the amplifiers.

#300-794= Flat
#300-796= Boost

See ya,

Darren
Parts Express

 

[Chad Kuypers]

Thanks Darren!