Need tech help please

brody05

Hi all, I need some help with a problen I have.
I am running two 10" drivers in series (drivers are 4 ohms - in series makes it 8 ohms), I am putting 350watts RMS x 1 (monobridged parasound amp) into them and with heavy tracks and low bass the overload lights come on and the amp will shut down at about -10 on a Denon AVCA1se.
Can I fix this by simply buying a bigger amp ie running 650 watts RMS at 8 ohms into it or is the problem still gonna be there.
Any help will be gratefully appreciated, I would have expected this idea to work but someone told me it want make any differance.

PolkWannabie

What amp is it ?

brody05

Parasound HCA1000

Planning on upgrading to HCA1500a (what do you think?)

I see you haven't changed your 'name', your a wannabe no more, what do you think about the 10hz thing mentioned under the old SRT thread we were using?

cmy330go

I think you would be fine with the 1500a you would be darn near doubling your overall power plus adding about 15 more amps peak per channel. I think those two driver are just way too much to ask of the 1000.

Best of luck
Dave

brody05

Hi, thanks for the input, that was my thought too and the HCA1500a mono bridged gives 30 to 35 amps (or as you said 15 per channel) for the subs, I could even try running each sub off one channel giving each sub 315 watts at 4 ohms with the new amp but I dont think there is anything to be gained.
The more techy people agree with the upgrade working in theory the more confident I am in giong ahead with the purchase.
Regards
Brody

radkrisdoc

What speakers are you using? There should be two problems in your setup, it's just a process of elimination....
1. Speaker impedance.....if you can, run an impedance curve or try obtaining one for the speaker you are running; solution: if the impedance dips below 2 ohms (one individual unit's impedance) or below 4 ohms with both speakers in series, either change the speakers, cos the HCA1500A will also "look" at the same impedance in bridged mode and u will have the same problem that you are facing now OR use the 1500A in stereo mode.
2. While speaker impedance is highly unlikely to be the problem, (cos the speakers are in series) see if the Denon's preamp outputs are not overdriving the Parasound amp. Try running the Parasound with a different preamp, preferably one with variable output. You might have to go for another preamp if that resolves the problem.
If you do find that an upgrade to the 1500A will work after this, I'd like to know if you will be selling the Parasound 1000A
Kris

PolkWannabie

Brody,

The Sunfire I use for the uppers is 425 wpc into 8 ohms and gets two channels one for the stereo array and one for the SDA array and the CinePro that I'm using at the moment into the subs is more like 800 wpc into 4 ohms ( as the original sub drivers are each 2 ohms ) but BOTH the Sunfire & CinePro are about 120 amps / channel peak to peak. There are lots of people who like the Parasound amps and I'm not knocking them. However, I have seen several people mention from their own personal experience that they run out of power in applications like this.

I'm not following your comment about the 10hz thing ? What are you asking ?

radkrisdoc

Oh yeah, I forgot, you can also use a Y-connect to drive both channels in your Parasound 1000A separately....this time around though, connect the speakers to each channel of the Parasound and not in series. You will definitely experience a louder volume level because there are two amplifiers putting out the same material into two speakers and the amps wont have wierd loads due to speaker interaction. If the amps shut down again i'd suggest replacing the speakers rather than upgrading to a better amp. The Parasound that you have is pretty good.
If you do plan to upgrade look at NAD; I dont have much experience in searching for amps that withstand under 2 ohm speaker impedances. Im sure the other guys in here will help. Kris

HBombToo

I think you should measure the dc resistance of the 2 subs so you know what the minimum is. At very low frequencies the amp is going to see very low impedance which is probably the problem.

If you have a Volt Ohm meter just simply measure across the +/- of each speaker and note the Ohm reading. This should be close to the very worse case.

HBomb

brody05

Hello all and thanks for your invaluble help,

I have measured with a rather budget reader and got 3 ohm's, I am sure the drivers were meant to be 4 Ohm but Rick says they are 2 and I would be suprised if he was wrong. I guess that makes them 4 ohms total in series.

What you say is right, it seems to overload now on more low freq than higher volume normal stuff, maybe having a sub that goes down to 10 hz is not such a good thing, perhaps I need to somehow cut the bottom 5 -6 hz out of it.

In regards to the 10 hz thing, I found it interesting that the original only goes down to 16hz yet this does 10hz.

Yes I will be selling the HCA 1000, it has a dual transformer built in for either 110 or 230 volts and I have the original box too. Our NZ dollar is so weak against the US that it would be a cheap buy to you over there (and we dont have the high freight charges that you do either).

Would the HCA1500a run a driver each if I just used it as a two channel, I am guessing that 2 ohms would be too much for it.
It has 60 amps as opposed to the 25 or 30 of the 1000. All I can do is try the bigger amp, if it doesn't work then I guess that will be for sale too. Getting to be a costly execise this.

Thanks to all for your help, it is 3am in NZ ao I'm getting some shuteye for a while, back in about 7 hours.
Brody

PolkWannabie

Brody,

If these are the original SW1080/1/2 drivers for the SRT's you are talking about then yes they ARE 2 ohms and present themselves combined as 4 ohms.

As far as frequency response goes, the originals are flat down to about 16 hz and do respond below that but not at the same level.

You aren't saying that your homegrowns have a flat response down to 10 hz are you ?

cmy330go

Originally posted by brody05
Yes I will be selling the HCA 1000, it has a dual transformer built in for either 110 or 230 volts and I have the original box too.

Just curious if you have any idea yet what you want for your amp?

Dave

radkrisdoc

lol I didnt notice that you were in NZ.....sorry bout that, I assumed u were in the US too. Kris

HBombToo

regardless of what (amp) amplifier you have, the risk remains in exceeding the limits of that amp as you approch the dc resistance(or exceeding the excursion limits of the sub). Which ever is the case its not a good situation.

What you should really look into is a subsonic filter like the ones sold by SVS that are manufactured by Marchand. You will maintain the integrity of the amp and the subwoofers by using one. I cut my dual subs off at 20hz and don't have an issue plus it sounds great. Besides anything below 20Hz is probably artificial anyway...

HBomb

brody05

Good morning all,

In regards to the freq range, I have notice with a test disc the homegrown does go lower, the others never produced sound at all at 10 hz and this 'new' one does, I can do some spl readings after this is sorted out ( and I have an exam in 2 days which the study is been somewhat neglected for).

It wouldn't be too difficult to get $550- NZ which is about $330- US. Is tht cheaper than what it would cost in the US?

Here is an excert from the manual re 110 volt and 220volt:

"As it is supplied for 110 V to 120 V operation the red and white transformer primary wires are attatched together. The black and yellow primary wires are attached together.
To convert to 20 V to 240 V operation, the yellow wire is disconected from the black wire, the white wire is disconected from the red wire. The yellow and white whires are then attached together."
This is followed by a simple diagram.

I will look into the subsonic filter, is it powered (ie electronic) and if so convert to 230 volts easily.

I really appreciate all your help, I think that from the information thus far the HCA 1500a will do the job but the low freq stuff may need to be decreased with a controller of some sort.
Cheers
Brody

HBombToo

Originally posted by brody05


I will look into the subsonic filter, is it powered (ie electronic) and if so convert to 230 volts easily.

SVS filter

http://www.svsubwoofers.com/marchandsubsonic.htm

Questions

http://www.svsubwoofers.com/questions.htm

good luck.

HBomb

madmax

If the speakers are 2 ohms each I would try using both channels as someone else suggested. That should be fine.
madmax

brody05

Hi, all.
An update on the learning over the last week or so regarding the problem. I have a NAD 218 on demo at the moment, seems to do the job really well (so it should, mono bridged gives over 700watts at 8 ohms), its not as good on paper as the Parasound amps but it has a higher amperage allowing it to handel the load. I am quite unfamiliar on NAD amps and wonder what is better, the NAD 218 or the Parasound HCA1500a? the price is similar, what would you guys prefer?
Thanks again for all your help, it has been invaluable and those crossover units from SVS are pretty awesome.
Brody:D

PolkWannabie

Not as good on paper in what respect ...

If the NAD does the job then I don't think I'd buy the Parasound until I saw and heard how it performed.

Regarding your previous comment about the 10 hz capability, how do you account for the difference ? the drivers & cab's are virtually the same with I suspect the only different in those respects being that the port might be somewhat different. One would think any real differences would be in terms of amplification i.e. the plate amp versus the external amp.

brody05

Good morning,
I am not really sure, the only guess I have would be the SRT controller may cut that >16hz stuff out to protect the amp or possibly drivers, from what I now understand the low freq lower the impedance and increase the load on the amp, the port is also virtually identical in dimension and material construction. Just a guess.

The Parasound amp has a damping factor of 800 as opposed to the NAC of 200
slew rate 130 ....... 100
headroom 1.5 db.........1
also a higher signal to noise ratio

I haven't got a HCA1500a to try out, its just buy it and see, I cant see it being a proplem, it has 60 amps per channel and correct me if I'm wrong but the proplem with the smaller Parasound is it only has 25 - 30 amps per channel.
Brody

brody05

Just thought I would update everyone on the progress over here. Firstly I sold the HCA1000 for $600- NZ.

The Nad I have pushed hard, left it on mono and in series and only managed to get it to cut out once, so it has its limits but they are very high, lets say I dont think I would hit the limit in normal or even a bit above normal listening conditions. One thing that does impress is the bass seems better than the original, the lower freq really can be felt, Rick, if your reading this, go ahead and build one, it may have taken a bit of dorking around but the final outcome is fantastic.

Thanks all for your help, it proved invaluable and I really learnt a lot from it, will also look in to the SVS controller too, but I dont think I need to cut the lower than 15hz stuff out now, kinda getting used to it.

Thanks
Brody

PolkWannabie

You could ask Polk about whether or not the SRT controller filters out the really low freqs but imho it isn't as I'm not experiencing that.

As an experiment you could try swapping your DIY sub in place of the SRT subs and see what you get in the way of the low freqs. If they disappear than one would think it has to be the controller and if not then maybe the plate amp ... or ... maybe it's old .vs. new drivers ?