Anyone do a "free air" or infinite baffle subwoofer in their 6?

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DennisLJacob
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

That's not my car, but that is what it looks like before the hole. I was thinking about drilling a few large holes in the back of the plastic pod to port the space or maybe prevent the chuffing you mentioned. But then again, it could take a negative audio effect just as easily as a positive one. So I figured I'd see what happens first and then respond to what happens.

If I mount the driver backwards, the magnet would backup to the underside of the plastic pod that holds the center pillow/pad above the A/C unit.

By-the-way, the photo is of the link everyone refers to when asking about putting a sub in a NA M6. That individual cut the bottom of the plastic pod off and put a 8" driver into a 6" X 9" speaker box and then installed it. I don't recall the overall outcome, but that is something I considered. But when looking at the freq. response of the ScanSpeak driver, I decided to go this route instead.

So Brucey, taking your thoughts on mounting the driver backwards, I was thinking in making a sealed box, that it would be shaped somewhat like a letter T. Only the leg of the T would be rather short. That would be looking at it from a side angle. The leg would be the driver sticking out below the horizontal line of the tee. If I were to do a 1 cu. ft. sealed box, given my baffle width of 32" X 12", I'd only need a 5" or 6" inside depth for the box. I even thought I could install port/s that would fire into the cabin behind the rear seats. Though I wouldn't have much ability to lengths on the port.

In the interior photos, the blue masking tape is where the rear seats have their support locations. So nothing can go where the blue tape is. The rear seats rest up against the rear bulkhead in those locations.

So many options, with none of them tried.
1987 M6, 1998 Dinan SC MZ3 Roadster
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by francoid »

Wouldn't the T create weird echos?
In my case I listen mostly to classical, I don't need a sub, and that makes things ***much*** simpler! I'll be installing an amp and new speakers in the next 2 weeks.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by slofut »

Dennis, you have a nice hole there #-o , I would cut a nice piece of 3/4 mdf or plywood to bridge across the flat spots from the rear (screwed or bolted to the sheetmetal), recut the round hole and mount a high efficiency woofer designed to be used IB, from the rear pointing towards the front. Fill in the gaps between the board and the recesses in the metal with a dense foam. Since an IB woofer is mechanically and electrically damped all the inevitable and incalculable losses in the trunk wont really matter. With a decent sub amp it will sound great (the more power the better). Do some research on IB drivers, the more sensitive the better.
You'll be pleasantly surprised. BTW... I was rarely happy putting a tuned speaker box into another box of unknown characteristics (trunk). It's all a compromise though for the most part.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Slofut, thanks for the advice. I planned on building a thick baffle. My baffle will be 3 X 3/4" material. Two MDF boards plus a 3/4" plywood laminated to the back of the two MDF panels. I'll be mounting the baffle to the inside of the trunk bulkhead. I just finished routing the rabbet and through hole. So all I need to do is mount the driver and bolt the baffle up to the trunk. I will be doing several layers of dense rubber insulation to fill and seal the baffle to the bulkhead.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Brucey »

FWIW I'd suggest at least trying the IB setup (with the drive unit whichever way round makes most sense to you), because you are nearly there now, plus if you don't like it, you can always convert it to a sealed enclosure later without much additional work.

BTW if you go for sealed box, I don't think that the exact shape of the enclosure is all that important at low frequencies; the wavelength is usually longer than the box dimensions, so you don't tend to get standing waves inside the box as you would in a speaker enclosure meant for higher frequencies.

Looking forward to your report on how it all works out!

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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by kos »

My audio set up

I was running ported but switched to sealed

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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Hi Kos, boy you've done a lot of work on your big six. The paint work, the interior, the engine. Everything and your car looks like new. Pretty amazing.

So I fired up the system a week ago. I have to say, that so far the IB sub sounds like it is going to be a winner. It was cool to be sitting in the car with MBPro sitting on my lap making on the fly crossover changes and spl levels. Can't wait to bring in the RTA mic to do the more serious work. But I have a nasty hiss/noise coming out of the tweeters and mid woofers in front. I've pulled everything out of the loop to try to trouble shoot the problem. So far is looks like it could be the HU, but not likly. The next is it could be my speaker cable, though it is top notch product. The last item is the JL Audio XD800/8v2 amp. When I change the volume with the HU, nothing changes. So that seems to rule out the HU. I can mute the audio output of the MiniDSP unit, which should cutout the entire front end, which is HU and ICs. The noise doesn't change, so again pointing at the JLAmp. Crutchfield is sending me a new amp and a pair of isolaters. The tech guy didn't think is was either components. He blamed the noise on my ScanSpeak tweeters and drivers. Note I didn't buy those items from them. I suppose the SS drivers might be too resolving and hiss and noise crap might be showing up and being reproduced played through those drivers. Blaming the hiss/noise on high end tweeters seems like BS to me. But we will see.
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Mark Shutt
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Mark Shutt »

is the amp gain set to minimum? having it turned up near full will give the possibility to introduce noise floor (hiss). I would rule out the tweeters and speaker cable for sure!
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

I followed the JL Audio input sensitivity instructions to a tee. For 4 ohm drivers, JLA wanted 17.3 volts on output with the HU at 3/4 volume. I've turned the input to half that number and still have the noise/hiss. I'm hoping it is the amp at this stage. I have great experience with ScanSpeak drivers. So I don't think it is them. I'm using the same tweeter in a component setup that is in the rear shelf pods. It's a nice package. The tweeter is nearly a perfect fit in the door panel oem location. Though the mounting method is front machine screws vs. the oem that had rear mounting method. But I found some nice metric black allen head screws. So it still looks oem if you didn't know what the oem drivers looked like.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Mark Shutt »

what happens with the amp on minimum gain? you can also try it with RCA cables disconnected at the amp end to completely rule out anything preamp..
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

I can mute the MiniDSP output, that basically removes all signal output to the amp. But I'll try those two suggestions to see what happens. No matter what it might be, I'm thinking of changing out the HU interconnects going to the trunk for either hookup to the MDSP or amp. I think something that is better shielded might make a difference. Or at least help with that final little percentage points that take a normal system to a quiet system. I've tried shorter high end ICs to see if there was a difference. Even though I was tired and the wind had picked up when I did that test, it seemed to be a little bit quieter with the better ICs in the loop. Though being 1m long instead of 5m long could also account for the preceived differences. When I did the original testing, it was in the morning when my mind and head were fresh and the outside noise floor was less. Wind where I'm at can cause the noise floor to go up quite a bit.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Mark Shutt »

noise floor can be quite annoying when you just want to listen to something at moderate volumes, In the past I've found digital processors to be the main culprit (not every one though) but most of all level matching of gain controls.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Ya, I'm hoping the MDSP isn't adding noise to the overall system. Though when I've disconnected it and removed it from the loop, the noise was still there. The components I'm putting in the M6 is going to be duplicated to my MZ3. So I really don't want the front end to be the problem.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Brucey »

maybe it is a bit late now, but if you are going to have the same setup x2, is it worth building the system up on the bench to test for noise etc, before doing an install? That way you can test for effects of lead length etc and work out if there are inherent issues with certain combinations of parts before you install them?

BTW I have encountered situations where a preamp is OK, an amp is usually OK and some speakers are usually OK but when you connect them all, you get more noise than you would like. It isn't always apparent that this will happen from an examination of the test data with each, either.

You can also get strange stuff going on eg where the phasing of signals in a certain frequency range isn't perfectly matched when it is being reproduced by more than one set of speakers. This can produce more noise than normal, weird images in the soundstage, things like that.

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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

I'm sort of doing that. I've tried out another pair of ICs and that didn't change anything. Tomorrow I'm going to install a second MiniDSP processor to see if that makes a difference. Then the Pioneer HU has a "network" option to change the front/rear/sub outputs to front high/front mid/subwoofer outputs. I'm concerned with the DSP product, but will have to wait until tomorrow when I'm not so tired and worn out. Need fresh ears and quieter surrounding noise floor.

On speaker drivers, the M6 kick panel will be my rear speakers on the MZ3. The rear shelf mid-woofer in the M6 will be my front mid-woofer in the roadster. I was hoping to use the same ScanSpeak tweeter, but it is just a little too deep. So I'm using a Seas tweeter instead. Then I'm using Integral Audio's subwoofer package. It includes a form fitting sealed enclosure for the car and a Alumapro subwoofer matched to the enclosure size. So a little bit different. I'm using the same DSP unit though in both cars. I like the options it has, but I'm hoping it isn't the source of the noises/hisses.

The tone of the noises, change. They aren't one note, almost like a radio station going out of range. The antenna is not attached - for I didn't want to inject another factor to consider or have to remove from the loop of gear. I've tried bluetooth via iphone and iphone head phone output. I've tried good old redbook CD, computer sourced music output from my MBPro. Then I've disconnected all of these sources to see if one or the other is causing the problem. So far nothing has changed. So the reason to think head unit or amp. Speaker cables and pulling out drivers would be a real pain that I'm hoping to not do.

These issues surely put a damper on the progress of a install job. Everything stops until the issue is figured out. Glad I haven't ordered the second HU or amps for the MZ3. Waiting on this issue for now. Though I may throw this gear in the other car and see what happens there. If it works in that car, then I have something else going on.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Mark Shutt »

What DSP are you using?
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

The company is Mini DSP. The processor I'm using is there automotive model C-DSP 6 X 8. Here's a link:

https://www.minidsp.com/products/minids ... /c-dsp-6x8

My only functional complaint is that it doesn't do 6 analog channel input. I think they should change the name or be more upfront about only 4 analog inputs and a 2 channel digital input. The digital isn't toslink fiber optic either. The only HU I've seen with digital output is the high end Sony and it's digital output is fiber optic. I think Helix has an amp with digital input, but don't recall what restrictions that input had.

I've also added their UMIK-1 mic, which comes with a specific unit calibration file. There are a number of software companies that allow their software to run with the unit too. So depending on how deep you want to go into processing - this unit can do it. I know I'll do basic setup first, but on a rainy or snowy day, I can see sitting in the car doing speaker driver tests and getting further into perfecting the sound and processing. I came close to buying the Helix system, but their calibrated mic setup just added a whole lot more to the bottom line. Plus with doing two systems at the same time - it looked to be expensive. But and that is a BIg butt, if the unit is contributing to the noise issues, it will get the boot. It will mean Helix time with possibly Helix amps or combo product. They are just coming out with a 8 ch processor/amp if I recall. I'd prefer it to be 10 channel, but I ended up doing a Madisound/ScanSpeak combination with a passive crossover for the rear shelf speakers. So I don't need 10 channel for the M6 (or the MZ3). Here is that setup link:

https://www.madisoundspeakerstore.com/a ... audio-kit/

I have a similar model of SS drivers in my mini monitors at home. That model is the 15W/8530K-00. That is the model woofer I'm putting in the MZ3 kick panel location. I prefer the 8530 over the 4531, but for the rear shelf speaker - they are probably way too nice to have back there anyway. But the woofer was a near perfect fit with minor trimming for the speaker grill slot on the pod to fit back into its little grove. The tweeter does the same with a little ingenuity with mounting method. They both fit into the oem rear shelf pods nicely. No one would no that different drivers were under the covers. For the M6 front kick panel, I'm using the SS 10F/8414G-10 4" full range driver here:

https://www.madisoundspeakerstore.com/a ... ull-range/

It isn't going to play any bass, but it fits and it has a decent off axis freq. response from 200 Hz to nearly 4kHz. So I'll have to rely on the SS subwoofer to fill in for bass. I'll probably know that the bass is coming from behind me, but I wanted to keep the oem look and positions. I also wanted a driver with something other than a untreated paper cone. This one has a fiberglass cone. I'm using the same SS tweeter that comes in the madisound/SS kit for the front door locations, the D2004/6020-00 here:

https://www.madisoundspeakerstore.com/s ... 0-tweeter/

For the subwoofer I'm using this SS driver:

https://www.madisoundspeakerstore.com/a ... lack-cone/

It's not too large and it is the only subwoofer driver I've found that rises above it sensitivity spl rating below 100 Hz. So for signal processing all I'll really need to do is cuting peaks in it's freq. response. It is also fairly flat up to 1kHz before it peaks up a few db and then drops off. It may not be the best driver for a IB setup, but if it doesn't work out, I built my baffle and mounting to be convertible to a sealed enclosure. I'll have to add 5 sides, but that is doable if necessary. Based on trial runs, I don't think I'll have to worry. I'm not a hip hop guy. I'm old school Pink Floyd, Genesis, Phil Collins or Peter Gabriel. Roger Waters too - what a mind and imagination he must have.

So that is what I'm doing/using and working with. More than you asked about. It's turned out to be a much more complicated process and it's taking a lot longer to implement and assemble. Trial and error too. Did I answer your question?

Dennis
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Here are some photos of the rear shelf speakers.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

more rear shelf photos
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Mark Shutt
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Mark Shutt »

if you want to rule out the DSP as the problem you could make some muting plugs out of old RCA ends and plug them into amplifier, if all is quiet after fitting muting plugs then either headunit or DSP or wiring is to blame.. I take it the noise is there with engine off?

this is what a muting plug looks like.

Image
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Thanks for the suggestion. I haven't even started the car with the new system install running. Better do that today too.

I don't even have seats in the car. I'm sitting on moving pads piled high with a 4"x8"x 16" high timber for a seatback. So I'm really in the trial stage trying to make sure everything is working proper before putting seats and panels back in place.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

Mark, I love your color combination. I was real close to buying a friends exact same color combo as yours. The blue and white interior is my second favorite color combo. My first obviously is the red with white interior. I love it so much that I'm considering changing the interior of my red exterior with black interior MZ3 to red and white leather. I looked at buying a black with white interior M6 and it did nothing for me. The black made the white look dirty. Too much of a black/white contrast. So if I do the MZ3, I'll use red as a buffer between the black and white. There has to be a buffer color - in my opinion. Anyway great color combination you have.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by Mark Shutt »

thanks! I do love the colour combination, it does look well especially in the sunlight 8) all this talk of audio systems and all I have in mine at the moment is an Alpine 7803ms and 4 Kenwood speakers, 6x9 in rear and 4x6 in front, the fronts are dreadful and do very little! I have a mountain of old school hi-fi stashed away but can't bring myself to start chopping up my car!
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by DennisLJacob »

I'll tell you it was difficult for me to do that first cut in the rear bulkhead for the subwoofer. If I was thinking of selling the car in the next year or two, I wouldn't have done it. But since I'm planning on enjoying this car for a long time, it just became a little bit easier. If you're anal like me, you'll do a professional job and even a purist would be happy. Doing the job right with the best products at the time - should out weigh the negatives of making a cut. I didn't do any cutting elsewhere except for the sub. But knowing that the front little kick panel drivers are not going to provide any bass - what choice do you have? Granted the rear shelf gives a little opportunity to generate some bass, but how much can you expect from a 5.25" driver? Even your 6x9 is limited to a hint of bass, not enough in my opinion.

However, if audio isn't important to you over the sound of the great 6 under the hood, then it isn't an issue. I'm a audio guy, with music being pretty important to me. So I wanted to have something excellent in the car. If you ever decide to do a sub, just make sure you have the right tools to do the job. That requires a circle cutting jig for making the metal cutout in the bulkhead. I used a Rotozip tool with their circle cutting jig. Then I switched out their pivot pin for a long bolt. I used the longer bolt to keep my center possition intact while circumnavating the uneven surfaces of the stamped bulkhead. Having a round, clean cut goes a long way to ease the pain of making such a hole in the car. Then if you want, use a edging material to protect the cut edge from looking unfinished. I found a truck trim edging material that would go over the metal and the extra oem mat noise insulation sheet. Do the job how the factory would have done it if car audio was important 30 years ago.

It was harder for me to drill the tiny holes in the door panel for the replacement tweeters. The oem tweeters where held in place from the rear of the panel. The tweeters I wanted to use, use three tiny holes. I found small black allen head bolts and nylock nuts on the back to hold them in place. It's not the same look as oem, but nice enough to not distract from the overall finish.

I wouldn't be too hard on yourself for your current setup. I'm sure when it was done, it was the best available with given components. If I had not known about the ScanSpeak 5.25" driver, I would have been looking at 6x9 speakers too. The owner of Integral Audio has been a great help to me in ideas and products to look at. So professional help/knowledge is available and worth its weight in gold. The internet - 99% improvement on finding information and recommendations from others. Do's and don'ts are pretty helpful. If this system finds its way, then I'll post a new topic with details and photos. But not until it meets my standards and doesn't have any flaws. I think the two concerns for most will be the 4" kick panel speakers, the subwoofer install and the MiniDSP with my current choice of amplifier and head unit. I''m hopefull the noise issue gets resolved quickly. Or at least identified so it can be eliminated permanently.
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Re: Anyone do a "free air" or infinite baffle subwoofer in their 6?

Post by francoid »

I can't find 4x6 I like. Some have tweeters that protrude so I can't use the stock covers, others are way too low on max RMS power, and many are just junk. Did you find something that works?
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