What "dig" at Alpine? I made no slanderous comments about them. People have tested them and come up with actual data backing my statement. I don't care for them because of problems they have had mainly output voltage.

If you’re referring to my comment "How many think Alpine HUs don't clip because they are a “good” band (lol well some people think they are)?" I know a lot of people consider Alpine to be a good brand which is why I brought it up, but the reason good was in quotes is because it is a relative term...and it wasn't being compared to anything here. If you are referring to the later part of the statement it was just a joke for the most part as many people here and in other places know I don't like Alpine.

Honestly I can't stand Alpine and would never run one in m truck, but many people do like them; I was basing my statements on facts not my personal opinion of them. My point was just to say the almost all HUS out there clip no matter the quality of them. Hell, I love Eclipse but even their decks do clip at max volume, and even a good bit before that, it may not be audible but they still clip and even clipping that is not audible can damage a speaker over time. As for the Alpines some have been know the clip prematurely and there is a lot of talk about it in the car audio threads, again I am not certain of the model numbers, but I'll see if I can't dig them up. Also, Clarion, a brand I consider to be pretty good….I am sure their HUs clip before full volume. It is more common to find a HU that clips (usually around 3/4th volume) than not.

So don’t take remarks personal just because you own the HU, it was not intended to offend anyone who owns an Alpine. Hell, a lot of people don’t like Focal, but that does not bother me. My speakers suit MY taste and that all that matters. So if you’re happy with what you own then that is all that matters.

 

The 7897 was the one with the output problems there was an extensive post done on it, hopefully I will get emailed the link tomorrow.

”The testing I saw reported on a forum was done with the sub out at 15, and the sub out put out 1.7 volts just before the front/rear pre outs clipped very hard. The sub out did max at 3.5 volts, but you could only get 1.7 "useable" volts imo....just clarifying the test that is mentioned(and referred to incorrectly many times) on the forums.”

http://www.caraudioforum.com/showthr...5&pagenumber=4

All HUs no matter their brand including Eclipse have or have had their problems, but again the reason I bring up Alpine in this discussion is because of the clipping issues and "quality" decks. Again my comments about Alpine where not meant to be a "knock" on Alpine, but rather to illustate that most decks clip no matter the quality; also I used the example of Eclipse too and again it was merely to illustrate that most HUs clip before max volume.

So lighten up...

 

Hey guys I just ran this information for setting gains. www.jlaudio.com has step by step instructions on setting gain using a voltage meter in the Tutorial section. All you have to do is figure out what the voltage should be with your amp and tune for that target voltage. To do this simply multiply the rated RMS wattage for your amp by the load or speaker impedance. Then take the square root of that number. So for 150W RMS and 4ohm speakers it would be 150X4=600 and then the square root of 600 which is about 24.49Volts. I used a digital readout multimeter and rounded to 1/100th. If anyone has trouble just email me at ieat.drt@verizon.net and I'll reply with the attached .pdf file from Jl audio and your target voltage if you give me either your RMS or make and model of the amp.

 

drteater,
That is a great procedure to use. That is how I set the sensitivities on my 500/5. The only thing I did different is that I maxed my volume. No sense in pushing the amp into clipping.

Here is a link to the page where the tutorial resides. Flash Player required.

http://www.jlaudio.com/tutorials/index.html#

 

Setting the gains with a DMM is a rough way of doing it, but for most it works. However, to set them correctly you would need an o-scope.

"ok, i broke out my oscilloscope today and took some readings on this deck.. this should sort out all the controversy about the weak pre outs on this unit..

i used 100hz and 1khz test tones, and a steady 14.4 volt power supply ( i modified a antec PC 450 watt power supply ), the oscilloscope is a tectronics 211.

first off, the front/rear pre outs.. these performed very well.. max volume on this unit is "35".. the front/rear pre outs do not clip at all until "32".. so you get the max performance at 31.. the voltage at 31 was a steady 3.9 volts RMS.. which is quite nice, considering that the unit is rated at 4v rms, however at 32 the clipping is quite dramatic, so dont ever turn it to that, 31 is the absolute max. these results were EXACTLY the same with either test tone, which i found to be strange, but my room-mate who is an electrical engineer said that is to be expected.

now, the sub pre out.. the trouble maker..

good news: the sub pre out doesnt clip at all, ever.

bad news, at volume level 35 ( max volume ) its only putting out 3.5v rms, which isnt THAT bad if you think about it.. but, and this is a big *but*, since the front/rear clips at 32, you cant run the sub pre out at any level higher than 31.. and at that level its putting out a meager, mere, pathetic 1.7v RMS...

so there you have it, this is the second 7897 i have had, and both have had the same problem.. id like to get my hands on some other decks to test..

so there you have it.. the real deal" by kepone on either elitecaraudio.com or sounddomain. There are quite a few complaints about the sub outs being weak by users with other decks too.

 

Boy, you really did some research on that one.

 

Just for grins I took my Fluke DVM and measured the preout voltages on my CDA-9815. First I set the EQ to flat, x-over frequency at 100Hz with 0db attenuation for F/R/S, and the sub level set to +15.

1. I disconnected all speaker leads.
2. I put my DVM probes on one of the the sub preouts.
3. I rolled on the volume until the DVM read 2.88V RMS (4.07V peak). This occured when the volume reached 33 (35 max).

I repeated this process for the other sub preout with same results. Then I repeated this process for the front and rear channels with the same results.

I assume that the Alpine unit does not clip before reaching 4Vpeak. So non-clipping region of the HU is 0 to 33. 34 and 35 may clip but I would need an o-scope to confirm.


Setting the Amp gains (using the JL Audio procedure):

I set my F/R gains with the HU volume set to 33.

I backed my subwoofer output level down from 15dB to 8dB and set my sub gain again with the HU volume set to 33. This way I can boost the subwoofer level for older CDs where the bass material is recorded at a lower relative level.

 

Preamp voltage has nothing to do with clipping (at the preamp anyway). A DMM will tell you nothing about clipping at the preamp, all that does it keep you from clipping at the amp, by allowing you to match the voltage that is coming into the amp.

"I assume that the Alpine unit does not clip before reaching 4Vpeak."

That is a BIG assumption. Read the quote that I posted. He could not get the advertised 4 volts out of the sub outputs unless he clipped the front and rear channels (hard).

There is a comparison of apples and oranges here....

Clipping at the HU can clip at any voltage it just depends on the HU. I essentially believe the same thing as you…I believe HUs should do advertised voltage before clipping; however this is not always the case, and this is my complaint. Generally on most HUs the "3/4ths rule" is a good one to follow as most HU begin to clip shortly after 3/4ths volume (or used to), plus it does give you extra room and allow you to clip your amp so you can get more power out of it.

Clipping at the amp occurs when the voltage that is going into the amp exceeds its input sensitivity. This can be harmful to the speakers, but at the same time the power output from the amp can be greatly increased, which is why SPL competitors some purple drive their amps into clipping.

Either type of clipping can be harmful to the speaker because it cause the speakers voice coil to "hang” for fractions at points of excursion and allowing heat to build up. Overtime this can damage the speakers.

So again JL guide is a very rough way of setting the gains, essentially they use "3/4ths method." If you follow the "3/4ths rule" you can generally avoid clipping at both the HU and the amp if done correctly, which is why it is so widely recomended.

 

Hazard,
Just to clear the air on the Alpine preout voltages, I brought home a portable oscope from work tonight. With max HU volume, the Sub, Front, and Rear preouts all read 3.7 +/- 0.05V RMS. That is 5.23 +/- 0.07 V peak. Substantially more than the advertised 4V peak. Absolutely no clipping or distortion of the preout signals on any channel.

So if Alpine had a problem with their preout voltages, they corrected it in the CDA-9815.


To all interested, here is a link to an abundance of car audio information. Enjoy.
http://www.bcae1.com/

 

Thanks for all the advice fellas. I appreciate it.

I have better control over the system now.

Now I just need to kick it up a notch and get some of those planar ribbon speakers!!!

 

I just find that VERY hard to believe that there was no clipping even at full volume.

Also, I know all Alpines did not have the same problems, but there has consitantly been people complaing about their sub level dropping once tey switch to an Apline. However, again I am not sure if it was a problem with the 9815 or not.

What was the sub level set at?

 

Just curious - Did you have the outputs wired into an amp, or were they un-terminated ?

If un-terminated, I would be interested in seeing the output levels when connected to the amps.

BTW - My 9813 can play wide open as well, without clipping.

 

I say all us Alpine supporters gang up on Chris and show him the error of his ways.

7969=unclipped 4V, toslink out, copper chasis, dead head and I love it.

 

Hey Haz, you better quit working on that aquarium stand and defend yourself. Sounds like the "big guns" are getting on to ya.

 

B-Man,
The preouts were unterminated.

You know the 9813 and 9815 have the same features except for the two line text display. So your preouts should operate the same as mine.

I found that with the HU volume maxd and 6dB EQ boost at 50Hz and at 1kHz, I got the preout voltages up to 4.8V rms with no clipping. These HUs must have a limiting circuit on their preouts. I say this because 4.8Vrms +6dB should yield 9.6V rms (for every 6dB the voltage doubles) but they maxd at 4.8V rms.

I set my gains using 3.7V rms (max volume, no clipping). The sub channel gain was 7.41 for 250W into 3ohms, the front channel gain was 5.41 for 100W into 4ohms, and the rear fill gain was 2.70 for 25W into 4ohms.


Hazard, the preout for the sub level control is set to max (+15).