Amp Question

Massif

I recently purchased both the MM651 and MM6501 for my Sony CDX-GT630UI head-unit. I have 2 12" subs that is powered by a 500W mono Kenwood amp. I haven't heard how the speakers sound yet. Should I get a 4 chan amp to power the speakers since they are 2.7 ohms or will the head-unit be sufficient amplification? I really want the most out of the speakers but I also don't want ear piercing treble. If it's advised to get an amp would this one be suffice? Thanks.

arun1963

Welcome to CP.

MM series are very nice. Oh yes you will need to amp them. 80watts rms per speaker will give you good head room. (for the times you want to crank it louder than your normal listening level while maintaining clarity). Look at polk, kicker etc for clean power and vfm.

Your 2x12" subs, make and model? 500 watts between two 12's may be a bit short, lets see. Are you running them in a sealed or ported encl?

IMO to hear the true potential of a good speaker you have to do two things. Generate a clean strong signal from your hu, amplify it with min distortion and then feed it to the speakers. I guess I have reservations about the sony xplod being able to generate the required signal. You could look at upgrading the hu as and when you can.

For now, get the amp and hook up the speakers and enjoy.

Massif

Thanks for the response. I'm kind of on a budget so I can't afford anything too crazy in terms of an amp so would this one be suffice? Also the subs that I have are in fact Sony Xplode. I'm new to car audio so I'm not really sure what I'm doing right now. I just want a good sound with no ear piercing treble.

arun1963

Personally, I would spend a bit more on the amp and go for the Alpine mrp f600, 100wattsx4 for about $70 more. If not, the kenwood would do fine.

500watts rms for 2 sony subs could be fine.

Polk speakers from the entry level (and the mm's are the mid series in mobile audio) to the top end are known for balanced sound and overall sound quality. So you wont have the harsh, piercing highs that you would get from cheaper components. Your xover for the mm6501 has a tweeter attenuating switch with the option of 3 settings. -3 / 0 / +3. Factory setting is at 0. If you find that too bright go to -3.

Hook everything up and take a listen. If you feel you need to go higher on the sound quality level you can upgrade your system over a period of time. You have made a good start by buying good speakers.

Or you may find that what you have is good for you, in which case enjoy

ps : remember you have to use the hpf from the amp for your components and the 651's. Your hu does not give you this option. Start off with hpf at say 80hz for front and rear and then try going lower/higher see what sounds best. Also play with the gains for front and rear. Start with keeping both the same then try keeping the rear gain lower. Find the setting that gives ou the best sound.

Massif

My hu has both hpf and lpf but It's probably advisable to go with the amps hpf I'm sure. And I think I'm going to with this amp. Crutchfield has it for $300 and is the same price as the Alpine but I can't find the Alpine as cheap so it's a good deal for me.

Massif

If you had to choose between this and this what would you go for? These are my only options right now because I found very good prices for them (under $200).

arun1963

Massif wrote: »

My hu has both hpf and lpf but It's probably advisable to go with the amps hpf I'm sure. And I think I'm going to with this amp. Crutchfield has it for $300 and is the same price as the Alpine but I can't find the Alpine as cheap so it's a good deal for me.

If your Hu has hpf and lpf, then do it from the hu. More conveniant than having to go to the boot to change settings(assuming thats where ure installing the amp).

Had checked the sony explod site last night for your model and the specs page didnt mention the filters Thats why I mentioned doing it from the amp. Re checked and yes its mentioned on the features page.

You can actually do it from both hu and amp and get steeper slopes. But lets keep it simple for now and do it from the hu.

arun1963

Massif wrote: »

If you had to choose between this and this what would you go for? These are my only options right now because I found very good prices for them (under $200).

Yes I saw the kicker also last night but both kenwood and kicker are around the 50-60watts mark. I was trying to get you more headroom with the alpine.

Of the two I would go with kicker. It has a better signal/noise number hence cleaner amplification. As brands, both kenwood and kicker put out reliable numbers.

Massif

Does is matter that the kicker doesn't have a cooling fan or do most amps not have cooling fans? If it does matter, Is this something that I have to buy separate? Thanks for all the help.

arun1963

Not really. Some amps dissipate the heat using a fan while others use a heat sink. Both work. Again personaly I would go with an efficient heat sink design. It eliminates the remote possibility of the signal picking up noise from the fans motor. The kicker amp is fine go with it.

arun1963

BTW, dont forget to dampen the front doors with dynamat or like product, when you install the components.

Massif

whats the dampening need for?

Edit: Never mind, I think I got the idea, thanks.

Massif

Last question promise ... this or this. The Fosgate has a lower signal to noise ratio but has other better specs than the Kicker.

arun1963

question count is not an issue, dont worry. The RF over the kicker.

1. more watts and cleaner, much lower THD. Total harmonic distortion. Slightly lower s/n but thats ok.

2. steeper slopes. Unless your hu does 24 db slopes, go back to thinking about doing the slopes from the RF amp. Steeper slopes between mids and sub = cleaner lower end of the sound.

Glad u decided to spend a bit more. With this amp you will be set for the next 5 years. No matter where you go with the rest of the setup. That is 1826 days at least. Look at it this way. You're spending an an extra $150 over your original choice, for greater and cleaner power and better sound and its only costing you 8 cents per day.

Massif

Thanks. It says for the Fosgate... "Fuse Rating : In-line 100 amp, not included" I guess that's another thing I need to purchase. Will any brand do? for instance.

Massif

Well I bought the RF. Best Buy is going to be installing all my new gear so I'm sure they have all the equipment needed in the shop. Thanks for all the help.

Toxis

uuuuuuuuhhhhhh please do yourself (and your car) a favor and find a local shop. If there's not one near by, drive 100 miles to find one. It'll be worth it if you have any respect for your car and your new found gear.

Massif

I've installed with Best Buy in the past and they've always done an excellent job for good/better prices than the local shops.

Massif

arun1963 wrote: »

1. more watts and cleaner, much lower THD.

I think the THD for the RF could be a typo because I don't see any other amp, even the most expensive of 4 channel amps, with that low of THD. I hope I'm wrong. Is it even possible for the THD to be that low?

arun1963

RF numbers are genuine. THD figure of 0.01% would be genuine. The amp would give you clean power.

Also if ure not a diy person like me, its important to have a reliable source for all future install / trouble shooting work. That is why I would agree with Toxis. I have just gone thru a turbulent period because I didnt have a solid contact and I hate install / connection work etc.

Massif

arun1963 wrote: »

RF numbers are genuine. THD figure of 0.01% would be genuine.

It's 0.1% not 0.01% though.

Massif

I just received my amp. Is it normal for something to sound loose inside of the amp? Something is rattling around in there.

arun1963

No, its not normal. Get in touch with the cs people from where you bought the amp. Give them your purchase and payment details and lodge the complaint. See what they say. Let them advise the next course of action. At this point, you don't want to do anything that would allow them to claim breach of warranty, down the line.

If I were in your place, I'd be pissed as hell and very tempted to unscrew the dman cover to find out what was rattling inside. :mad: . However dont open the cover just yet. You may have to return the amp and they would check to see if has been opened.

Massif

arun1963 wrote: »

No, its not normal. Get in touch with the cs people from where you bought the amp. Give them your purchase and payment details and lodge the complaint. See what they say. Let them advise the next course of action. At this point, you don't want to do anything that would allow them to claim breach of warranty, down the line.

If I were in your place, I'd be pissed as hell and very tempted to unscrew the dman cover to find out what was rattling inside. :mad: . However dont open the cover just yet. You may have to return the amp and they would check to see if has been opened.

Oh believe me, I was pissed as all hell. Luckily the company that I bought it from is happy to exchange it so everything is all good.

Massif

This set-up sounds freakin' amazing BTW. Best system I've ever had by far (and better than I've heard in other peoples cars).

arun1963

What can I say?........congrats??? Enjoy for sure.....lol

Massif

I'm getting a lot of engine whine/wheeze through the speakers. Got any ideas on how to stop it?

arun1963

I had the same issue sometime back. Two things that come to mind are

1. Grounding issues
2. Rca issues

Check the point where all the elec wires are grounded. Make sure this point is free of paint, the nut iis tight, no wires are loose etc. Also check the contacts at the battery.

It could also be an issue with the rca's. Maybe they are getting pinched somewhere. You can try swapping your rca's with another pair if you have one. Which rca's are u using?

When I had the issue I checked the ground point which was fine, so I just replaced my rca's with stinger's and no problems since.

Massif

Ok so I got rid of the engine whine. The next day the bass from the sub woofer started to cut-off every now and then when turned up to normal listening volumes. The following day the sub just stops working completely and I've ruled out that it is the amp as someone I know tested the amp for power and there is nothing coming out of it. The sub is fine as I tested it. Got any suggestions on a mono amp? I don't want a Kenwood this time. Do I need an amp that can put out more than 500 watts? Thanks.

Massif

so far I'm looking at this one

http://www.crutchfield.com/p_575R5001/Rockford-Fosgate-Prime-R500-1.html?tp=115

arun1963

500 watts rms at 2 ohm is prob less for 2x12". BTW which subs are you running. Look for an amp that puts out 800-1000watts at 2 ohm.

What you heard the day before your kenwood died, i.e. the bass cutting off and then coming back, was your amp clipping. I.e. the subs were trying to pull more watts that the amp could generate. Thats another indication that you need a bigger mono amp. It would also depend on where you had your gains set.