Experimenting with Minidsp and Sure 4 x 100W amp

[DanP]

Do you ever do that thing where you want to experiment with something, but to do so, you need a bunch of other things in place, so you end up rigging a bunch of stuff to just get on with it and you end up experimenting with all the stuff you just rigged up as well? Well I just did that and was so surprised by all the various rigged elements that I had to post the experience.

So I've had a Minidsp I bought used from a forum member a couple of years ago and of course it has been on the shelf the whole time. I wanted to give it a try, so I jumped on line and purchased a plug in for $10, a little worried that the version would be incompatible (part of the reason I hadn't played with it yet). It downloaded fine and after a little messing around, I was up and running and could write to the Minidsp unit. Cool. Now I need a 4 channel amp and a 2 way speaker with no crossover.

I had posted before about the New Wave buyout speakers having perfect cutouts for the Seas L16RN-SL and the Seas H1212 tweeter which I had lying around. One speaker was already assembled with no crossover, so I finished the internal cabinet mods on the other one and installed the drivers. I plugged the ports as the box is only 1/3 cu ft and the Seas woofer wants a much larger vented enclosure. Cool.

I also had a Sure 4 x 100W amp (7498 chips) on the shelf that I picked up at the tent sale a couple years ago. I paid peanuts for it because one of the fan blades was missing. So I grabbed a 24V 5A power supply from a DTA-100 and fired it up. The fan spun up and the green light came on. Cool.

I had measured these drivers in this cabinet before, so I brought the files into PCD and applied all kinds of filters and delays to them in the active section until the FR was flat and the phase was tracking like a champ. It was sooooo much easier than applying the passive components. Once it looked good, I copied those parameters over to the Minidsp and loaded it up.

Now I got to hook everything up and hear the results of all my rigging. Cool.

It was outstanding right off the bat. With all these unknown variables in components and active xo process, I expected to have a disappointing first and maybe second impression right off the bat. Nope. It's not the best setup I've heard or even at my house, but for throwing old components from the shelf together with an undersized power supply and winging the xo, I was shocked how good it sounded. I knew the L16 has midrange distortion issues so I crossed at 1.5kHz and I think I missed most of it.

Then I pulled out the port plugs which left an 8dB peak at 90Hz! No problem, just dsp it flat and sync with the plug in. Then I shoved a smaller diameter, longer port right in the port hole (it was tapered and pressed in snug) to get the port to help with the lower frequencies and re-tuned with the Minidsp! So easy! So much fun!

So here's my wrap-up:

Sure 4 x 100W amp: Unbelievable for this application and the price. Very low noise floor and great dynamics, especially considering the PS was limiting the amp to probably 40W to each woofer and 10W to each tweeter.

Minidsp: I can't believe how easy this was to implement and how little it colored the sound. It literally takes seconds to implement a change as complex as you want and I heard no detriment adding large (>6dB) cuts or boosts. The $10 plug in had more than enough features to completely customize the 2-way speaker.

Seas L16RN-SL: This thing is a BEAST! I had no idea. It sits in a 5.75" diameter frame with an extra large cone stuffed in that space and a respectable 6mm xmax, but the xlim is 11mm and I'm pretty sure I went past that many times with nary a sound from the woofer. Holy moly - I couldn't hurt this thing. Zaph measured it as the lowest distortion woofer in it's category from 200Hz down and I totally believe it. Have you ever felt a palpable chest thump from a pair of 5" woofers at 8ft away? Me neither until now.

It's nice when every link in your rigged chain is stronger that you thought it would be!

Dan

[howard]

Thank you for posting this. I have a Minidsp that has just been sitting around for about a year. I also have a Rane 6 channel amp. Maybe this will get me going.

[ani_101]

The speakers that I got to grand rapids and Iowa were based on minidsp 2x4 and sure 4x100 amp. I used the 2x4 advanced plugin.

[donradick]

Thanks Dan - I've been thinking about using a Minidsp for a few years now.
One of the big unknowns for me has been the plugins.
Appreciate your "blow by blow" description.

[DanP]

No problem guys. There were a couple hiccups getting the hardware set up because it was a used unit and I had to move a jumper and press the reset button before it would sync. A couple quick google searches had me on my way though.

The plug-in is the actual software in it's entirety, which I didn't realize beforehand. So you download it and open it up and start playing with the curves. When you're ready to transfer it to the dsp unit, you just plug it in to the computer via usb and hit the sync button. It takes about 5 seconds to find the unit and sync the parameters. You don't have to disconnect it from the audio system or anything, although I have been powering down the audio system to transfer parameters - I'm thinking I don't have to though, and will experiment with that tonight.

The only downside is that you can't visually manipulate an actual FR curve. You just see and manipulate the graph of the tranfer function. However, both PCD and WinISD have active filter functionality so you can see the results of the filters on the modeled bass response (WinISD) as well as the measured FR curve (PCD). Without these tools, you would have to measure the speaker response as you make changes to see what's happening, which is the more accurate way to do it anyway.

Ani - your setup in Grand Rapids helped motivate me to dust off the parts on the shelf and get moving. Had I known how easy it was, I wouldn't have waited so long.

$200 and about a half hour of setup will get you legit, full blown dsp crossover and parametric eq capability AND a decent 4 channel amp to go with it. I'm not saying I'll stop making passive xovers because I still like having a fully contained speaker that you can plug into any amp and have it sound good, but this is the most fun you can get for $200 in DIY audio in my opinion.

Dan

[Bob Brines]

Once you sync the miniDSP to your computer, you are changing the filters in the minDSP directly from the keyboard. If you have REW loaded (probably others, but this is what I do) and a USB mic, you can run a measurement after each change. Not exactly what you want, but close.

Bob

[Wolf]

Since the introduction of the L16, I've always likened it to their version of the SS 15W/8530K00 Revelator. The size and parameters are similar. I don't believe I've had the opportunity to hear a pair yet though.
As you inferred though, it should be a beast.

Later,
Wolf

[bcodemz]

Since the introduction of the L16, I've always likened it to their version of the SS 15W/8530K00 Revelator. The size and parameters are similar. I don't believe I've had the opportunity to hear a pair yet though.
As you inferred though, it should be a beast.

Later,
Wolf

I don't think the L16 is comparable to the Revelator. While the Revelator is a fantastic generic purpose mid bass driver, the L16 is a unique small woofer specifically designed to be used <1000Hz only in a small 3 way and never meant for 2 way use with a tweeter. The L16-RNSL was specifically designed for Linkwitz's Pluto speaker (The SL stands for Siegfried Linkwitz) where he wanted a small woofer optimized for sealed use with outstanding sound quality and bass to be crossed at 700Hz with a 4'' full range driver. The driver sacrificed >1000Hz capabilities in order to achieve the bass and lower midrange quality that the L16 is raved for.

Dan: It's great to see people jumping on the active DSP speaker bandwagon. Spend some more time playing, and you might never go back to a passive crossover again. Hint, try a much lower tuning and use a low shelf filter to boost the bass back to flat, and be amazed of how much more bass and deeper bass you can get from a small bookshelf speaker.

[dcibel]

Since the introduction of the L16, I've always likened it to their version of the SS 15W/8530K00 Revelator. The size and parameters are similar. I don't believe I've had the opportunity to hear a pair yet though.
As you inferred though, it should be a beast.

Later,
Wolf

That's a bold statement, as the L16 is half the price of the Revelator. Looking through Zaph's measurements, the L16 looks very limited for midrange use, while the 15W has lower 3rd and 5th harmonics throughout, and especially above 1kHz. The Seas W15LY provides a better comparison to the Scan 15W/8530 in my opinion.

[Millstonemike]

The only downside is that you can't visually manipulate an actual FR curve. You just see and manipulate the graph of the transfer function. Dan

Do I understand you correctly ... you can tweak each filter function via its graph ala a graphic equalizer? But you can't see the overall "sum" of the filter functions. And the plugin doesn't have knowledge of the driver's FR (e.g., .frd graph). So you need to translate the filter function into something that ISD/PCD could model (or measure) for a "closed loop" type tweaking.

[Wolf]

There is a model that is not an 'SL', L16RNX last I checked, and I was focused on the bass range and performance. Being it's an aluminum cone, of course the bandwidth will be smaller, and more bass-range centered. And no- it's not quite half the price. Ratio in cost is about 0.56. The FR is decent enough to be able to xover it at 2k if you wish, as that is below breakup. The box models are very comparable to that of the 8530K00.

I don't see why I got the response I did here,
Wolf

[Bob Brines]

Do I understand you correctly ... you can tweak each filter function via its graph ala a graphic equalizer? But you can't see the overall &quot;sum&quot; of the filter functions. And the plugin doesn't have knowledge of the driver's FR (e.g., .frd graph). So you need to translate the filter function into something that ISD/PCD could model (or measure) for a &quot;closed loop&quot; type tweaking.

The miniDSP is not a modeling tool. It is an on-the-fly equalizer. I think that what you are wanting is to load a fr plot, add some filters and see a corrected fr plot. Doesn't work that way. The best way to do it is to run an RTA, apply a filter, run an RTA, repeat.

Bob

[DanP]

Since the introduction of the L16, I've always likened it to their version of the SS 15W/8530K00 Revelator. The size and parameters are similar. I don't believe I've had the opportunity to hear a pair yet though.
As you inferred though, it should be a beast.

Later,
Wolf

It's funny you say that as I have a pair of the 15W/8530K00 sitting on the shelf waiting to try. They are almost identical in size and from what I've heard, the bass capability of the 15W is amazing as well, but from an application standpoint, I would agree with the others. The breakup of the L16 translates down in the harmonic distortion to make it best suited as the bottom of a small 3 way. Even crossed at 1.5kHz as I have it, I fear I'm hearing some of those artifacts. I believe the 15W should be easily capable of normal 2 way duty. I'll find out soon enough.

Dan

[DanP]

The miniDSP is not a modeling tool. It is an on-the-fly equalizer. I think that what you are wanting is to load a fr plot, add some filters and see a corrected fr plot. Doesn't work that way. The best way to do it is to run an RTA, apply a filter, run an RTA, repeat.

Bob

Right. But you CAN see the sum of all your filters as a transfer function graph, starting from a flat line at 0dB and then changing as you apply filters.

Dan

[DanP]

Hint, try a much lower tuning and use a low shelf filter to boost the bass back to flat, and be amazed of how much more bass and deeper bass you can get from a small bookshelf speaker.

I used a shelf filter to account for BSC, but hadn't thought about using a second shelf with an EBS alignment. That's a very elegant way to do that and gets the port doing a little more of the heavy lifting. I could see a PR coming in to play in that scenario as well.

Dan