HQ Amp for the Autotuba

[Psyfur]

I have been working to optimize my car setup for dual AT's. I pretty much got the eq and crossover frequency set where I want it, now its just down to the amp. The AT's are loaded with high xmax dual 4 ohm coil drivers with 250w rms power handling. I got a MB Quart DSC 1000.1 to run the subs and the spec'd power is 350w@4 ohm, 500@2, and 1000@1. I have a deep cycle battery in my car and the amp is hooked up with 0 guage wire and a 10 farad cap. If I play a sine wave the amp sounds clean and seems to put out plenty of power but with music the results have been less than awesome. With dance music it sounds kind of lousy. Transients sound distorted even at lower levels. I played around with alot of settings and could not get what I want.

I said what the heck and pulled one my Bryston 4B's out of my HT stuck it in the car. The 4B is 250w@8 and 400w@4. Wham! There was the sound I want!!! I cranked it until the clip lights were just starting to come on and backed it down a hair. It sounded amazing no matter what kind of music I ran through it. I was measuring over 125 dB on kick drums from rock music. Dance tracks sounded perfect with lots of punch and deep bass to back it up. This setup yielded some of the best bass sound I have ever heard in my life.

So my question is what are the specs that make the Bryston so much better? It seems the power of the two amps is at least comparable so what should I be looking for in a 12v amp? The only thing I have seen that has similar specs to the Bryston is a Mcintosh car amp that costs lots of $$$. JL audio seems to have a few amps with good specs but most are class D and I haven't found many class D amps I like the sound of.

Per the AT plans a dual 4 ohm sub wired in parallel should be a 6 ohm load so two of those in parallel would be 3 ohms. Does anyone know of an amp that can do 500w@4 with the SQ to match?

[Bill Fitzmaurice]

So my question is what are the specs that make the Bryston so much better?

They're honest?
Auto-sound specs, for both drivers and amps, are pretty much a fantasy.

[jcmbowman]

I bought a Blaupunkt THA-1250 PnP for my AT hookup, and it performs beautifully. (it was a replacement for an older Infinity sub amp that decided to self-destruct during a long drive on a hot summer day.)

I've never been impressed with the MB Quartz stuff. Their ratings appear to be all based on "maximum output" figures, not RMS.

When you see two amplifiers with similar specs on paper, but greatly varying price tags, you can generally assume one of two things:
1) the cheaper one is cheaper for a reason.
2) the expensive one is from a brand that spends a -LOT- of money on marketing.

I find it's usually a combination of the two, which is why I stay away from any of the really low-end stuff, and also have no love for the big-name brands in car audio like Alpine, JL, and Rockford Fosgate...

I've never had a bad experience with blaupunkt or sony car amplifiers.

[Psyfur]

Thanks for the input. I'll check out the Blau amps. And yes, Bryston is very honest I have an interesting twist to the plot though. For a long time I've been running my car subs off of a cheap 100$ Kicker ZX300.1. When I hooked it up with MCM loaded AT's it didn't do well with the higher impedence of the cabs and ran out of gas quickly at it is designed to run 250w@2ohm. That's why I bought the MB Quart. I didn't even think to try out the Kicker amp with the new dual coil drivers. I swaped it back in and it sounds a million times better than the MB Quart. It certainly doesn't put out as much power but the kicks and transients sound really good. I swear the MB Quart amp sounds like its half a beat behind and distorted on techno. It sounds pretty good/very loud with sine waves and dubstep. The Kicker amp doesn't do as well with the sine waves but I believe that is because it is running out of gas. So I don't get it. Its not that the DSC isn't putting out rated power, it seems to just sound terrible. Is it engineered to only test out well with sine waves with no regard to how it reproduces actual music? Both amps are class AB but I beleive the MBQ has a pwm power supply.

[jcmbowman]

Thanks for the input. I'll check out the Blau amps. And yes, Bryston is very honest I have an interesting twist to the plot though. For a long time I've been running my car subs off of a cheap 100$ Kicker ZX300.1. When I hooked it up with MCM loaded AT's it didn't do well with the higher impedence of the cabs and ran out of gas quickly at it is designed to run 250w@2ohm. That's why I bought the MB Quart. I didn't even think to try out the Kicker amp with the new dual coil drivers. I swaped it back in and it sounds a million times better than the MB Quart. It certainly doesn't put out as much power but the kicks and transients sound really good. I swear the MB Quart amp sounds like its half a beat behind and distorted on techno. It sounds pretty good/very loud with sine waves and dubstep. The Kicker amp doesn't do as well with the sine waves but I believe that is because it is running out of gas. So I don't get it. Its not that the DSC isn't putting out rated power, it seems to just sound terrible. Is it engineered to only test out well with sine waves with no regard to how it reproduces actual music? Both amps are class AB but I beleive the MBQ has a pwm power supply.

I'm sure that the MB quart is designed to do well with large one note wonder boxes, and the clean output of sustained sine waves is just a side effect....

[Zack Brock]

What drivers are your AT's loaded with?

[petegt]

I have an alpine mrd-m300 mono amp for my TAT loaded with jbl 804 200w rms driver. The amp can put out roughly 100w (measured with 30hz sine wave) which seems good as it is rated at 100w rms at 4 ohms @ 12 volts and the nominal impendance of the TAT with a 4ohm driver is 8ohms (I am running the amp indoors with a modified pc power supply so its dead on 12 v sometimes dipping to 11v when turned up). Overall the amp does a very good job, i feel the TAT has got abit more in it but it gets really loud.

Will try putting 2 TATs in the car soon

[Drey Chennells]

TAT19_016_phixr.jpg (79.59 KiB) Viewed 2124 times

We've built several TAT19/10" (DCS255) and in our shop bus I've got a Hifonics Titan 500x1 on the TAT(1-2) and 100x4 midbass on up. Previous setup used 3 12" aperiodic. They were tight but the TATs detail and effortless quality is very impressive. I got my amps (factory refurb) for around 200 total..they have control everywhere you could want including variable subsonic HPass..

[Psyfur]

Thanks to everyone for all of the input.

What drivers are your AT's loaded with?

My AT's are loaded with Ascendent Audio Assassin 8's.
http://billfitzmaurice.info/forum/viewt ... =5&t=11511

I think I'm going to try a JBL BPX500.1. I talked to a JBL tech guy and got some "honest" specs. The amp will put out 500w+ into any load 1-4 ohms with a 12v supply. It has 12/24 dB/octave low pass/high pass and DBO. DBO is an adjustable frequency and filter Q high pass. Seems cool to be able to increase the Q of the subsonic filter to bump the freq at cutoff and then roll off sharply after that. Also this amp has some Crown amp technology in it and runs fairly efficiently. Like a Crown amp it can do parallel and series bridge modes for max power into multiple impedence loads. It seems like the high voltage mode will be good for the AT's. There's a bunch on Ebay for 200$ but I found someone local that can hook me up with a new one for a good price. I should have it at some point today so I'll let y'all now how it sounds.

review: http://www.audiogearreviews.com/reviews ... Px5001.asp

[Drey Chennells]

the JBL BPX500.1 appears to be a great amp, it was my other choice..

[Psyfur]

Just got the BPX500.1 hooked up. I haven't really had a chance to dial everything in perfectly but got it pretty close. This is a mean sounding amp! It has about the same punch and kick as the Bryston. The transients sound good and are fairly well defined. It definately sounds a bit more gritty and dirty than the Bryston. To be fair though one is a pricey high end solid state and the JBL is a mid-priced car sub amp.

I tried wiring it as both parallel and series mono, with series mode kicking out more volts and sounding better. I measured 27v output while the amp was still sounding clean which would be around 500w with my setup. I didn't feel like pushing it past that, as it was somewhat LOUD . All in all I feel like these amps are a steal at 200$. It does sound alot like a Crown pro amp to my ears and matches the character of the AT's very well.

[Tom Smit]

I measured 27v output while the amp was still sounding clean which would be around 500w with my setup.

I was just wondering if you had measured the voltage output on the other amps.

[Drey Chennells]

Nice. Question for you though man,

with series mode kicking out more volts

... at the same gain your voltage would normally go up when decreasing the impedance right, so in series voltage would go down unless you raised your levels compared to parallel.
Your amp would have to run at 1.5ohms to get 486 watts out of 27 volts..at 4 ohms 27 volts gives 182 watts, so I'd want to know whats the measured impedance, then add a bit for the horn loading. Also I'm sure youre aware of it but be sure to hi pass!

[Psyfur]

I was just wondering if you had measured the voltage output on the other amps.

I have been driving around with a volt-meter on my dash . The MB Quart amp was putting out around 25-28v. To my ears it didn't sound that great above 20v, and dance music transients sounded bad even at lower voltages. The Kicker amp was putting out close to 20v and still sounding pretty good. It could do more but started sounding really horrid. The Bryston 4B was king outputing over 30v and still sounding perfect. I had it wired with one sub on each channel.

Nice. Question for you though man,
... at the same gain your voltage would normally go up when decreasing the impedance right, so in series voltage would go down unless you raised your levels compared to parallel.
Your amp would have to run at 1.5ohms to get 486 watts out of 27 volts..at 4 ohms 27 volts gives 182 watts, so I'd want to know whats the measured impedance, then add a bit for the horn loading. Also I'm sure youre aware of it but be sure to hi pass!

With parallel/series I was refering to the bridge mode of the amp not the subs themselves. It is my understanding that the parallel bridge mode on the amp delivers more current for lower 1-2 ohm loads and the series bridge mode delivers higher voltage for 2-4 ohm and higher loads. I could be totally wrong about that though. I have two dual-4 ohm drivers and have kept all coils wired in parallel. I measured the drivers and they read 2.1 ohm on one meter, and 2.8 on another meter per driver. Their both cheap meters so I'll try to borrow a better one from work.

Your right about the 27v. I came up with 243 watts at 3 ohms and doubled it for two cabs. However the 3 ohms is for both cabs so it would be 243 total and I shouldn't have doubled it . The 27v was measured with music though. Just for fun I went out and put on a 63 hz test tone and cranked it and got 38v. I very quickly turned it down as it sounded scary and I couldn't tell if it was the cabs distorting or everthing rattling. I have my HP set at around 25hz.

How can I take measurements to generate an impdence curve for these boxes? Is there and easy way to do it with test tones/sweeps and a volt meter?