Monsoon Amp X-over freq and strange behavior?

[TbeaunTx]

For the Audio-heads here, I have a couple of questions...

1) Does anybody know the crossover frequencies the Monsoon amp uses to separate the front tweets from the Mid-bass door speakers?

2) I did some tests prior to doing speaker replacements to get rid of some of the factory cheap hashy inarticulate sound, and I noticed something weird. When I fade all sound to the front I lose almost all bass output from the Sub. When I fade all sound to the rear, the bass returns, but the sound from the rear speakers reminds me of my first transistor radio from the 70's - complete $#!+. Does anyone know the low-pass and high-pass frequencies used for the rear speakers or is the output to them full range (I tend to doubt it). I was hoping to do a front speaker upgrade and cut the rears altogether, as any true audiophile would do...but I wanted to avoid the cost and hassle of upgrading the amp if possible. I've found with some of my other cars (BMW's etc) that the factory head units were often pretty good, but the sound was then ruined by cheap paper cone speakers and/or crap amplifiers. I have Onstar and would like to leave its function in tact without spending $1000's on this upgrade.

[GM Roadster Club]

Originally Posted by TbeaunTx For the Audio-heads here, I have a couple of questions... 1) Does anybody know the crossover frequencies the Monsoon amp uses to separate the front tweets from the Mid-bass door speakers? 2) I did some tests prior to doing speaker replacements to get rid of some of the factory cheap hashy inarticulate sound, and I noticed something weird. When I fade all sound to the front I lose almost all bass output from the Sub. When I fade all sound to the rear, the bass returns, but the sound from the rear speakers reminds me of my first transistor radio from the 70's - complete $#!+. Does anyone know the low-pass and high-pass frequencies used for the rear speakers or is the output to them full range (I tend to doubt it). I was hoping to do a front speaker upgrade and cut the rears altogether, as any true audiophile would do...but I wanted to avoid the cost and hassle of upgrading the amp if possible. I've found with some of my other cars (BMW's etc) that the factory head units were often pretty good, but the sound was then ruined by cheap paper cone speakers and/or crap amplifiers. I have Onstar and would like to leave its function in tact without spending $1000's on this upgrade.

If memory serves me correctly this has nothing to do with the Frequency's, you lose bass when you fade to the front because the Sub's Volume is in Sync with the rear speakers......I also hate to tell you this but if you really want the nice clean sound then you'll need to replace the factory Monsoon Amp (it's to weak to drive upgraded speakers properly)...Since you are already plan on cutting out the rear speakers I would purchase an Alpine PDX 4.150 and use it to run your new front's and bridge the other two channels and run an upgraded subwoofer.

You can get the wireing diagram from your dealers parts department and use the Low Level out's from the Stock head unit to drive your new amp.


Trust me $400 later you'll be much happier.....I hope this helps....

Martin

[TbeaunTx]

I figured that would be the case, but hoped I could get by for a while before upgrading the Amp...I have always had good luck with Alpine amps, had quite a few of the older V-Powers, have a 6 or 7 year old one in my Infiniti G.

Thanks again,

Beau

[TbeaunTx]

Well I decided to go ahead and do some speaker upgrading prior to getting an Amp just to see what effect it would have. Here's what I found:

1) Friday night I upgraded the door woofers with the woofers from a set of MB Quart Discus series 6.5 Comps...it got dark so rather than starting on the tweeters, I gave it a listen. There was at least a 100% improvement in the quality of sound, and I noticed no strain or added distortion by the amplifier despite these being 4 ohm woofers (the factory ones do have 2 Ohm printed on them)...I don't like ear-bleeding volume anyway. I would highly recommend this upgrade to anyone who just wants to improve the muddy sounding front speakers on a Monsoon system. and richen the mid-bass quality.

2) Saturday morning comes, and I tear into the tweeters, low and behold I discover a high-pass passive crossover on the monsoon tweeters (4.7 uF 50V cap wired inline, and mounted on the tweeter bracket...this only proves that prior posts on crossovers being located in the Amp are at least incomplete, and possibly wrong. So I went ahead and installed the MB Quart Tweeters with no crossover. The sound now became inbalanced (due to the monsoon amp and its strange way of synching the Sub with the rear speakers, and the various balances between mid/high and bass, nothing was quite right...but still sounded better than the factory tweet/woofer combo, and there was sill plenty of power.

Initial Conclusion:

There is no Ohm rating printed on the monsoon tweeters, so if they are 2 ohms as previously posted, then this Cap passes only frequencies above 16.9 kHz...I highly doubt that as I can hear them and I don't have hearing above that frequency. If the tweeters are of higher impedance, then the capacitor would cause a crossover at a lower frequency with a 90 degree phase shift. My guess is that one of two things is happening...either the tweets are more like 4 ohm and the cap is crossing over at somewhere around 8.5 kHz, or there is a 3rd order crossover in the monsoon amp and the tweeter cap is effectively only added to cause phase shift back to zero rather than attenuate any audible frequencies (upper threshold of human hearing is generally considered to be 16.1 kHz iirc).

Anybody know for sure what is going on here?

[lil goat]

I put in a set of JBL GTO 6.5's with tweeters. I ran the subs of the amp for now and just put the Xover in line on the new tweeters, it's better but not great. I would love to know how the amp is wired as well, and where is it? Be nice to do the xover at the amp.

[Krelubot]

Thanks for the info here. Now I know where that crossover is.
The amp is behind the drivers seat. From the wiring diagram, it appears to be an 8 channel one with two channels being wired to a dual voice coil sub. Somewhere on these forums(audio section) is a wiring diagram.

[TbeaunTx]

So today I added a capacitor to cross over the MBQuart tweeters at the designed frequency of the MBQ comps, and to retain the phase relationship designed in the factory monsoon setup...the funny balance and sound disappeared as I expected and everything is better now.

I also discovered that once again, many people on this board have incorrectly posted the speaker impedances at 2 Ohm, I found the tweeters, and the rear speakers in the corners behind the seats are all indeed 4 ohm. Only the door woofers and the DVC Subwoofers are 2 Ohms. This should help open up some options for people wanting to upgrade in stages like myself. I like the improvement made by the MB Quart Comps up front. I may just wait until I blow the Sub or something before doing any more...Naaah, Ill keep playing with it.