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Author Topic: OT some what QSC plate amps  (Read 14514 times)

Douglas R. Allen

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OT some what QSC plate amps
« on: April 05, 2012, 04:53:07 pm »

For the do it yourself people QSC has their 700 watt subwoofer plate amps on sale. $210 dollars. Designed for the HPR151/HPR181w subs. I called qsc and was told both models have the same low cut freq.
I picked up 2 for some subs I have.
Might be handy for someone.

Douglas R. Allen
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #1 on: April 05, 2012, 04:53:50 pm »

For the do it yourself people QSC has their 700 watt subwoofer plate amps on sale. $210 dollars. Designed for the HPR151/HPR181w subs. I called qsc and was told both models have the same low cut freq.
I picked up 2 for some subs I have.
Might be handy for some here.

http://www.qscparts.com/wp00151600.html

Douglas R. Allen

(Forgot the link)
« Last Edit: April 05, 2012, 04:59:32 pm by Douglas R. Allen »
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john sanders

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Re: OT some what QSC plate amps
« Reply #2 on: April 06, 2012, 09:42:02 am »

Do you plan on installing the plate amps in QSC boxes or do you have other subs you'll attach them to?
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Bill Hornibrook

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Re: OT some what QSC plate amps
« Reply #3 on: April 06, 2012, 12:25:35 pm »

Do you know what the weight of these amps are? Just curious - there's not a lot of specifics up about them from what I've found.

I imagine that they weigh maybe 20 pounds or so being the older Class H designs.
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #4 on: April 06, 2012, 04:15:22 pm »

Do you plan on installing the plate amps in QSC boxes or do you have other subs you'll attach them to?

I have had some HPR181i subs for some time now. Other than the input gain knob being different (and of course the hpr151w silk screening its the same amp section) I picked up 2 thinking  spares. I may put them in some very simular boxes I have or not. I'll have to see how long they sit. It would be easy to test the amps before installing. Not sure of what eq settings are in them other than the low cut filter and high cut filter. I believe its 40 hz low cut,110 hz high cut. Fixed. I'll look at them with Smaart when they come in.

Still at $210 dollars its a great price for a 700 watt at 8 0hm plate amp.

Douglas R. Allen
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #5 on: April 06, 2012, 04:27:23 pm »

Do you know what the weight of these amps are? Just curious - there's not a lot of specifics up about them from what I've found.

I imagine that they weigh maybe 20 pounds or so being the older Class H designs.

That would be a good guess. Not an extreme deal breaker for me. I think mine should arrive next week and I'll put them on the scales.
The speakers in my HPR181i subs are 8 ohms. The amps are rated at 700 watts. I remember when they first came out there was some info on them. I believe they have a bridged amp section in them. I seem to remember it was from the rmx1450 bridged but I'm unsure right now.I doubt they will run 4 0hms. But at $210 for an amp for single 18 subwoofers etc. 700 watts is a good power range for club/weekend bands. The added QSC name is of course a big plus.
Maybe someone from QSC will post as to weight/power ouput and if 4 ohm operation is possible.
Douglas R. Allen
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Bill Hornibrook

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Re: OT some what QSC plate amps
« Reply #6 on: April 06, 2012, 05:49:56 pm »

The RMX 1450 weighs more like 40 pounds, so yeah - if you could weigh them that would be great. Anything else you find out about them too if you test them would be handy too :)

I have a couple of home built single 18's (loaded with B&C 18NW100s) that I use for non-critical applications which might be somewhat appropriate (doesn't have to be a perfect match). But I don't want to take what are now 85 pound boxes and make them 125 pound boxes. Their light weight is their biggest advantage right now.
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #7 on: April 06, 2012, 08:14:01 pm »

The RMX 1450 weighs more like 40 pounds, so yeah - if you could weigh them that would be great. Anything else you find out about them too if you test them would be handy too :)

I have a couple of home built single 18's (loaded with B&C 18NW100s) that I use for non-critical applications which might be somewhat appropriate (doesn't have to be a perfect match). But I don't want to take what are now 85 pound boxes and make them 125 pound boxes. Their light weight is their biggest advantage right now.

I may just pull one out from a hpr181i and check the weight if I get a chance late tonight. Not sure how busy I'll be. Won't have time to smaart one as I'm using them at a gig tonight.
If I don't have a chance I'll report back when the new ones come in.

Douglas R. Allen
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John Livings

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Bill Hornibrook

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Re: OT some what QSC plate amps
« Reply #9 on: April 07, 2012, 07:19:33 am »

I may just pull one out from a hpr181i and check the weight if I get a chance late tonight.

Good heavens I hope you didn't do that! There's no hurry on this at all. If you could possibly weigh your new ones when they arrive that would be helpful though :)
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #10 on: April 07, 2012, 11:47:09 am »

Good heavens I hope you didn't do that! There's no hurry on this at all. If you could possibly weigh your new ones when they arrive that would be helpful though :)

Opps, too late. Hey we're all friends on the LAB. :-)
Using an ultra high tech digital bathroom scale borrowed from the front desk the amp weighted 18 lbs.

Unit does have a sealed sub chamber. With it there I would make one if your putting these in your boxes. It measures 5 1/4 deep from bottom to inside top.
 7 1/2 wide. It is the length of the sub box but a 24 inch long box would work.

Box is what looks to be 3/4 stock. Routing around to set the plate in is 1/2 inch wide. 1/4 inch deep.

( All sizes measured with a top notch, ultra quality plastic ruler again borrowed from the front desk )

Most of the weight is from the transformer no doubt there. Its very beefy and amp overall looks to be a robust design.

I only had time for 2 quick pictures as it was getting close to 3am but I hope you can get the idea.

Let you know more when the new ones come in.

Douglas R. Allen
« Last Edit: April 07, 2012, 12:44:43 pm by Douglas R. Allen »
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Bill Hornibrook

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Re: OT some what QSC plate amps
« Reply #11 on: April 07, 2012, 02:04:22 pm »

Wow - thank you Douglas! Actually your pics do help because I didn't realize that they are housed in a cup. I'm not sure I'm going to go in this direction but at least I know what I'm in for if I do.

A followup on your own project will be fun to read. Best of luck :)
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #12 on: April 21, 2012, 09:04:17 pm »

Wow - thank you Douglas! Actually your pics do help because I didn't realize that they are housed in a cup. I'm not sure I'm going to go in this direction but at least I know what I'm in for if I do.

A followup on your own project will be fun to read. Best of luck :)

Wanting to put the amps into "something" I picked my old loaner,you need some subs? here use these to put the amps in.

Things about the QSC amp. The amp is for their hpr151w sub. A 15 inch sub box. The Low cut on the amp is higher than the hpr181w sub and the high cut is higher in freq and not as steep a slope as the hpr181w. Comparing to my hpr181i the limiter seems to clamp down longer as well. This is all good as I will be loaning , giving out these to local bands/friends to use for this and that.

I put them in my boxes and to be honest they sound pretty good.
What you'll see in the pictures is the amp cavity and some quick testing I did. I've looked at my HPR181i subs more than a few times. They have a little peak around 55hz and you'll see a peak at around 83hz for the 151w module. I'll do some real testing and comparing when I get some time.

Overall they sound pretty good. The Low cut seems to be a pretty steep slope at least 24db if not even 48db per octave. My guess would be the filter starts around 50hz. Its about 6dbs down at 45hz.The High cut seems to be 18db. If you look at the 125hz range its is close to 0db and one octave up at 250 its down 18dbs. There is a 4/5 db boost at 83hz. My guess is to put some punch into the sub.
Again overall happy with the amps in these boxes. I'll report back when I have a chance to use them out on shows.
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #13 on: April 21, 2012, 09:05:24 pm »

The amp chamber installed.
Douglas R. Allen
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #14 on: April 21, 2012, 09:07:22 pm »

Amp installed.

Douglas R. Allen
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #15 on: April 21, 2012, 09:08:53 pm »

Quick picture of the response in my living room.
Not the best I know but it is a rough idea.

Douglas R. Allen
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #16 on: April 21, 2012, 09:20:33 pm »

Quick picture of the response in my living room.
Not the best I know but it is a rough idea.

Douglas R. Allen

Looking at the specs for the HPR151w sub on the QSC site I see these specs.

47 Hz - 110 Hz 6dbs down
43 Hz - 140 Hz 10 dbs down.

I'm pretty much right on the money.

Douglas R. Allen
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #17 on: April 21, 2012, 09:26:10 pm »

For those who may want to know they have a fresh set of these installed in them.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=294-307

500 watts rms.
1000 watts program.

The 700 watts the QSC supplies should be about right for the drivers.

Douglas R. Allen
« Last Edit: April 21, 2012, 09:28:16 pm by Douglas R. Allen »
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Tim Padrick

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Re: OT some what QSC plate amps
« Reply #18 on: April 21, 2012, 11:18:01 pm »

A boost at 83?  I most always have to cut there, no matter the rig.
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #19 on: April 22, 2012, 07:16:40 am »

A boost at 83?  I most always have to cut there, no matter the rig.

This boost could have been put there by QSC to even their subs response out. Maybe the box/speaker combo they where using had a dip in its response there.
I'll look at the eletronic output of the amp and see if it is there as well or if it is in my own box setup.
I agree the response will make a boomy sub but I'd rather eq a peak out then add eq to a drop in response.

Douglas R. Allen
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #20 on: April 28, 2012, 03:11:43 pm »

Did my last testing with the subs before they go out. Looks to be May 12th for their first gigs.
I found they matched up well with the QSC hpr181i sub. About 22 degrees out of phase at 50hz and around 12 degrees at 80hz.

Combining 1 QSC home built with 1 hpr181i sub I got 6db boost at 80hz and still respectable 4 db boost at 50hz.
The Home brew sub has a steeper low cut filter so this adds to the phase difference. Still I would use the 2 subs together if it was ever needed.

Happy with the project and how well the subs sound. I had for some time thought about getting some Proel subs but these should do as good of a job and for less money invested. Per box I have about $180 in the driver with $225 in the amp/wood/glue etc. About 16 hours in total for both subs. I don't count the labor as I called it hobby time.
So for about $400 dollars I have a pair of 700 watt QSC powered subs that sound good and are not that hard to move around.

They matched up well with my Yorkville EF500ps and the Yamaha MS400s I have.

Douglas R. Allen
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Douglas R. Allen

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Re: OT some what QSC plate amps
« Reply #21 on: May 13, 2012, 10:41:18 am »

Some friends of mine played last night. They let me try the subs out and mix them.
They have the JBL JRX118sp subs that they normally use.

http://www.ebay.com/itm/JBL-JRX118SP...item20c5393351

For tops they have the PV 2-15 and horn. I gave the sub and tops a listen. I thought the sub was high cut quite high. Even in the 250hz range or so it was still putting out quite a signal. On the tubby side.
I listened to the tops and felt something was just not right. It sort of sounded ok but the horns were very loud in relation to the lows. I couldn't get the expected level out of either speaker. I looked the speakers over to find a Parts Express 2 way crossover with no cd horn eq had been put in them. Popping a handle off I found a Peavey 22xt driver duct taped to the horns in place of the 14t horn that should be in it. Black widdow speakers were in place at the bottom speaker location. Also as the crossover was just a 2 way someone had run the 2 15s in series.
The crossover did have a horn level knob so I turned it almost off to get a good blend. Set up like this I thought the speaker sounded better. Horns were soft sounding in the highs. I put a high shelving eq starting a 2k with a 6db boost to make up for the missing cd horn eq. This made them sound ok. I used my CS800s amps with built in crossovers to power the tops 100hz and above.

Leaving their subs in place "In case" I put the tops on my subs and did the show. (they made great monitor/amp stands) I'm not a fan of subs on each side of the stage but it put the tops just high enough to get the job done. I had some very large power alleys in the room but everyone was happy with the sound.

The subs;
Subs really did work great. The QSC amp modules never ran more than just warm/cool. The boxes pounded harder than they had before. They moved a fair amount of air for the size. Before I had 800 watts per box but the 700 watts provide by the qsc amps seemed tighter yet as deep. I believe the low cut filter at around 45hz instead of the 40hz I used on the amps for them before may be part of it. Of course the room I used them in comes into play hear as well. To be honest I found a rattle on the bottom where the port is that I never noticed before. They did come alive. I'm sure not having long speaker cable runs also added to the tight sound.

Overall everything worked better than expected. Nice small subs for shows just like this. Had fun

Douglas R. Allen
« Last Edit: May 13, 2012, 10:43:26 am by Douglas R. Allen »
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Re: OT some what QSC plate amps
« Reply #21 on: May 13, 2012, 10:41:18 am »


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