Need your advice. Should I get a new amp for my DIY subs - AVS Forum
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post #1 of 22 Old 07-27-2014, 01:28 PM - Thread Starter
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Need your advice. Should I get a new amp for my DIY subs

Hey guys, I currently have 4 DIY Ultimax 15s in their own 3 cuft enclosures. I am running them off of a CV-5000. So there is a ton of power going to them.

I also have an Anthem reciever, and when I run ARC, it shows a null starting at about 22hz. For the rest of the curve, ARC makes it pretty flat. Except for 22hz where it starts to drop off.

So I was thinking of selling the CV and getting an Inuke 6000 dsp so that I can fix that 22hz null and make it flat down to as low as possible and still hopefully as loud as possible.

If I do this, I can only get 1. At least for a long while. If I made the switch, it would greatly reduce the power going to each sub. Right now they each get about 1200 rms. If I make the switch, they would get about 550 each rms.

Is the huge difference in power in order to get dsp worth it? Should I sell the CV and get the Inuke?

My room is essentially an open unfinished basement. So worst possible room there is most likely.

Oh, I also can't spend any money. So by me selling my CV then buying the Inuke, it should cover all the costs. That's why I can't get a second or spend any extra money.

Thanks!
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post #2 of 22 Old 07-27-2014, 02:49 PM
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Save up change and get a mini-dsp.
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post #3 of 22 Old 07-27-2014, 02:51 PM
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Why not get a Beringer peq ? On eBay there like 100-125$. Used even cheaper. I know you don't want to spend extra dough but I wouldn't want to lose that much power.
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post #4 of 22 Old 07-27-2014, 04:01 PM - Thread Starter
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Beghringer PEQ??

Thought about mini dsp. For some reason just don't want to go that route. Seems like too much of a hassle. I could be wrong though.
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post #5 of 22 Old 07-27-2014, 04:21 PM
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I know everyone likes to have extra power - so this noob's opinion may not be popular - but are you using the power? I mean do you over clip the amp? I bet you probably hardly ever tickle to -10dB light, am I right?

And someone correct me if I'm wrong here, but dropping the power by half is going to mean -3dB headroom, right? I realize you want to add DSP so you can boost the low end - and there goes the rest of your headroom... but how much do you actually use?
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post #6 of 22 Old 07-27-2014, 06:00 PM
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Quote:
Originally Posted by HopefulFred View Post
I know everyone likes to have extra power - so this noob's opinion may not be popular - but are you using the power? I mean do you over clip the amp? I bet you probably hardly ever tickle to -10dB light, am I right?

And someone correct me if I'm wrong here, but dropping the power by half is going to mean -3dB headroom, right? I realize you want to add DSP so you can boost the low end - and there goes the rest of your headroom... but how much do you actually use?
When I listen at 5dbs from reference with my ported 15" during heavy bass scenes I tickle the red light. With my one sub that is getting 1100 watts it rarely goes past three lights. If he listens at only -10 dB's then he's fine.

I'm upgrading my 3000 to a 6000.
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post #7 of 22 Old 07-27-2014, 06:35 PM - Thread Starter
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I have never really looked at the lights when on to be honest. I will do that next time and see what lights up.

In case I wanted to get the Mini dsp, what would I need to get? I know it needs special adapters or something like that.
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post #8 of 22 Old 07-27-2014, 06:44 PM
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Quote:
Originally Posted by 04rex View Post
I have never really looked at the lights when on to be honest. I will do that next time and see what lights up.

In case I wanted to get the Mini dsp, what would I need to get? I know it needs special adapters or something like that.
I run some bass clips and just watch the lights to make sure I'm in the safe zone. Normally when watching a movie I don't look at them.

There are good tutorials on minidsp site and here as well. I've never used one.
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post #9 of 22 Old 07-27-2014, 07:49 PM
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The miniDSP 2x4 balanced has Phoenix connectors for input/output and power input. These are small connectors that accept bare or tined wire. You need to go from XLR or RCA (depending upon what you are using) to those.

I have two of the balanced miniDSP 2x4 boxes and what I ended up doing was purchasing 2 of these:
https://www.parts-express.com/neutri...tic-d--092-092

and 4 of these:
https://www.parts-express.com/neutri...tic-d--092-090

I also purchased some chassis mount RCA jacks and switches so I could toggle that switch which straps pins 1&3 for the unbalanced RCA connection. I got a 2.1mm DC jack as well so I could use a common 12v wall wart to power the box. Then built a very simple housing which was just a base made from 3/4" MDF with two 1/8" hardboard pieces screwed onto opposite ends which are used to mount the input/outputs jacks into.

Kind of a pain to build but it does not cost all that much and is extremely flexible. The only downside I see with the 2x4 version of the MiniDSP is the 7.5ms limit on delay. If you have multiple subs spread around your room for smoothing you can only delay the closest ones up to roughly 8.5' to bring them into alignment, which is not a whole lot. 50ms would be much better.
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Last edited by mtg90; 07-27-2014 at 07:52 PM.
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post #10 of 22 Old 07-27-2014, 08:01 PM
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Nice post Matt. Quick question Matt, if I have my two front subs 8' away and my nearfield 18" away how much delay to put on nearfield ? Currently I have it on 20ms. I have no idea what setting should be.
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post #11 of 22 Old 07-27-2014, 08:56 PM
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Quote:
Originally Posted by chalugadp View Post
Nice post Matt. Quick question Matt, if I have my two front subs 8' away and my nearfield 18" away how much delay to put on nearfield ? Currently I have it on 20ms. I have no idea what setting should be.
A 6.5' distance represents a 5.77ms delay
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post #12 of 22 Old 07-27-2014, 09:01 PM
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1ms of delay is just over 1' of delay, so you would want to delay your near field subs roughly 6.5' or around 6ms assuming these are identical subs.
Best practice to measure any of these changes. Stick you mic at the LP and measure the front subs only (with the AVR crossover set all the way up), then measure only the nearfield subs. Now run both and look at the summed response you should see gain across the board, if there are any nulls in the passband (below your crossover) the delay should be adjusted. Move it one one way, if the null gets worse or deeper you know you need to go the other way.


A similar approach can be used when adjusting the subwoofer out delay on your AVR to make sure your speakers/subs are aligned correctly and working together at the crossover rather then fighting each other.

Making sure your subs/speakers are working in together and are time aligned can result in gains of 3-6dB or more over an improperly setup system which is like doubling the number of subwoofers and amplifier power for free!
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post #13 of 22 Old 07-27-2014, 09:05 PM
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Thanks guys !!! I noticed when I measured the phase that it made a 3db difference. My nearfield is much better with 180°. I will change my delay.
Love this forum
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post #14 of 22 Old 07-28-2014, 07:15 AM - Thread Starter
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Ok, so what would i need exactly if i wanted to get a Minidsp? Currently i am running an Anthem reciever which is RCA out to a RCA to XLR adapter that connects to the CV-5000. So what would I need (including type of Minidsp) and all that Phoenix connector stuff?
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post #15 of 22 Old 07-28-2014, 07:37 AM
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Quote:
Originally Posted by 04rex View Post
I also have an Anthem reciever, and when I run ARC, it shows a null starting at about 22hz. For the rest of the curve, ARC makes it pretty flat. Except for 22hz where it starts to drop off.
It "starts to drop off" until where? 25Hz? 50Hz?
You're probably looking at a room null, especially in your admittedly non-ideal room, which you will only be able to minimize by experimenting with placement of your subs. Your best bet is to invest <$100 in a microphone and a lot of time into learning the basics of Room EQ Wizard (REW), much help for which is available here, and get your room set up right.
You can't eq everything.

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Did you really need to quote that entire post in your reply?
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post #16 of 22 Old 07-28-2014, 07:46 AM - Thread Starter
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Well, here is a link of my sub graph i posted in the Anthem Thread. It shows the drop off at the end. Sorry I cannot just post the pic. I am at work and undable to do that.

Anthem MRX Receivers - 300, 500, 700 Owners Thread & Tweaking Guide

Post 16547

Thanks
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post #17 of 22 Old 07-28-2014, 07:55 AM
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You're getting good advise there, which pretty much duplicates what I would say here. It looks like it's just rolling off below 20Hz, which is fine. If you want to go lower, you'll need to boost the low end until just before your subs blow up.
Realistically, how much more (lower, not louder) bass do you want?

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post #18 of 22 Old 07-28-2014, 08:01 AM - Thread Starter
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I dont know. I am good with the bass now, but just seeing that dip, and always hearing people rave about 10 or 15hz content, i just dont want to miss any of it, provided my system is capable, which i believe it is. Problem is after 20HZ, I have no idea if it continues to dip dramatically, or evens out or what.
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post #19 of 22 Old 07-28-2014, 09:49 AM
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Actually, there is some (friendly) debate about the "value" of sub-16Hz output. As with most things, costs start to increase exponentially.
Your output probably rolls off smoothly and normally. How about using an SPL meter or an app for your smartphone to get some ballpark measurements?
I presume the boxes are sealed. You might want to tackle a ported design to dig lower.

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post #20 of 22 Old 07-28-2014, 09:51 AM - Thread Starter
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They are sealed, yes. I think i will just hold off for now then. Maybe once i actually finish my basement, i will see how it works out. I am fairly confident that it has to do with the fact that my basement is unfinished.

Thanks for all your help.
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post #21 of 22 Old 07-28-2014, 10:14 AM
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One more stupid comment before I go:
The amp's high pass filter is off, right?

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Did you really need to quote that entire post in your reply?
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post #22 of 22 Old 07-28-2014, 10:40 AM - Thread Starter
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Correct. I made sure it was off. No filtering is being done by the amp.
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