New custom 'PM' (public music?) rig.

[psin3t]

Hi all. I have been a longtime lurker and irregular contributor, but I have been working on a project that might interest some, plus I am always up for advice.

The first thing to point out is that I am on a tight budget. I have been building this rig for some time, but I have been lucky to put aside $100 maximum per week towards it. Patience and D.I.Y. are a virtue and you can get a long way eventually.

First up, the Plan. I wanted an outdoor PA system for the purposes of playing electronic music to small crowds, mainly for private use. As the plan grew, I realised it might be something other people wanted to hire (eventually).

It had to be super-efficient and run from a single 10A 240V (Australian) outlet. This also makes it easier to pwoer in remote locations ('doofs').

I wanted 2 large main speakers and a single sub. The mains would be mounted on stands such that the mid speaker would be at approx. ear height, with the tweeters a little higher so as to be able to pass overhead of the first row of dancers/listeners. I wanted a highly directional system so as to minimise the chance of annoying neighbours. As I said, I had very little money. They are white, because they are going to be painted by a local artist with a 'psychedelic' bent

What I built is this:

 

[psin3t]

No not the kid (though I made that too).

The subwoofer is yet to be built, however I have a high quality [email protected] RMS Class D amplifier for it.

Tweeters: Vifa H25TG05-04
Mid: PRV Audio 6MR500-NDY-4
Mid-Low: PRV Audio 15W700

The mids are in a sealed enclosure, inside the main cabinet. Each driver is driven independently from its own amplifier:

Tweeters: Roger Godinsksy Research Model Five Power Amplifier ([email protected])
Mids: Sansui B-2101 Stereo Power Amplifier ([email protected])
Mid-Low: Yet to be purchased Stereo Power Amplifier ([email protected])

 

[psin3t]

One of the really interesting budget 'cheats' I discovered, was a reasonable quality active crossover for a fraction of the price I would have paid for a professional active balanced crossover:

Lanzar OPTIXA6B. While Lanzar are the greatest name in audiophile equipment, their 'Optix' range is their 'Premium" range - and it has 6 separate stereo outs with adjustable LPF, HPF and bandpass.

Between this and a 2-channel 31-band graphic EQ (also not yet purchased), any required sound shaping can be done.

The downside is using unbalanced signals - but the quality of the amplifiers and their power supplies - so far - means that they are truly dead-silent, even at full power.

http://www.lanzar.com/sku/OPTIXA6B/...-Output-15V-Line-Driver-and-Remote-Bass-Boost

 

[psin3t]

So - I have yet to purchase a subwoofer driver, construct the subwoofer cabinet, purchase an equaliser and purchase an amplifier for the 2x 15" woofers in the main cabinets (350W RMS min.) The subwoofer will then also be painted white, because a local artist is going to paint over them.

Any advice, questions or suggestions are welcome!!

 

[psin3t]

Lanzar OPTIXA6B active unbalanced crossover specifications:

SPECIFICATIONS
GENERAL
Total Harmonic Distortion @ 1KHz………………………………………………………0.04%
Signal to Noise Ratio…………………………………………………………………….>105dB
Stereo Separation…………………………………………………………………..……...>70dB
Current Drain………………………………………………………………………….……200mA
Remote Turn-on Time………………………………………………………………….….0.5sec
Recommended Fuse……………………………………………………………………..........1A
Dimensions.................…………………………………………………….1.6”Hx5.9”Lx12.8”W
INPUTS
Input Impedance
Front & Rear & Subwoofer…………………………………………………….….22K-Ohm
Input Voltage………………………………………………………….………….150mV~1.6V
OUTPUTS
Crossover Cut Off Slope…………………………………………………………..12dB/Octave
Maximum Output Voltage…………………………………………………………………….15V

SUBWOOFER
Low Pass Crossover Frequency………………………………………….40~400Hz
Subsonic Filter……………………………………..………………….Full/30Hz/50Hz
Phase Shift……………………………………………………….……………..0 or 1800
Bass Level Remote Control…………………………………………………….Wired
Rear (Mid Bass/Band Bass 3):
Mid Bass: Low Pass Crossover Frequency…………………………40Hz ~ 1KHz

Band Bass 3:
High Pass Crossover Frequency……………………………………..40Hz ~ 1KHz
Low Pass Crossover Frequency…………………………………….. 1KHz~12KHz
Front(HIGH/Band Pass 1/Band Bass 2):
High:
High Pass Crossover Frequency…………………………………..…1KHz~12KHz
Band Bass 1 & Band Bass 2:
High Pass Crossover Frequency……………………………………..40Hz ~ 1KHz
Low Pass Crossover Frequency…………………………………….. 1KHz~12KHz


If anyone is selling an amp/EQ or subwoofer driver, let me know! Plus, the rig needs a 'name' for marketing....

 

[chris661]

Hi,

A few thoughts:

- You really don't need 15" midbass drivers if you're going to use a sub. 12" drivers are smaller, lighter, and will provide plenty of kick down to, say, 80Hz.
- It might be worth using a compression driver based tweeter if you're aiming for high power levels. The horns used with compression drivers have much more directivity than small dome tweeters.
- You appear to be using class AB HiFi amps. I'd strongly recommend using class D amplifiers (Behringer iNuke are decent, and cheap), which will draw around half the current of your HiFi amps for the same power output.
- For subs, have a look at a TH-18 in the subwoofers section. 35Hz extension, plenty of SPL available. Particularly for subs, I'd recommend saving up for a while and buying a really nice driver.
- a Behringer 31-band graphic will do the job.

- You haven't set any SPL/coverage goals, so an idea of roughly how loud you want to go, and how low you want the bass go to would give us a good idea of what to recommend.

Chris

 

[psin3t]

Well I already have the drivers and amps - and built it - as it says. I am not about to return them or start again........

Class D amps have terrible specifications and audio - period - unless you can afford to spend a small fortune. I can't. A Powersoft would be great.

Behringer do not advertise specifications, therefore I will not touch them. I will have a good look at the TH-18 though.

 

[bitSmasher]

You're attempting PA usage with hifi gear and approach. Not viable unless you dump money on it...

 

[chris661]

Well I already have the drivers and amps - and built it - as it says. I am not about to return them or start again........

Fair enough.

Class D amps have terrible specifications and audio - period - unless you can afford to spend a small fortune. I can't. A Powersoft would be great.

They did 20 years ago. The extra efficiency and weight savings from modern switch-mode amplifiers are non-trivial, and shouldn't be discounted so easily.

Behringer do not advertise specifications, therefore I will not touch them. I will have a good look at the TH-18 though.

Fine, here's some specs.
Behringer inuke NU6000 vs KAM KXD7200 bench tested - Speakerplans.com Forums - Page 1

Let me know if you want more.



What sort of area are you aiming to cover? What SPL? How low do you want the bass to go?

Chris

 

[Enzo]

Class D amps have terrible specifications and audio - period

Agree with chris, this is not at all true. Every major manufacturer of power amps and powered speakers, including subwoofers, makes class D amps now in their lines, and some, like Behringer, are not expensive at all. Now if you want to build it yourself and spending as little as possible, that is OK, that is your choice, but the digital stuff works well and reliably, and sounds killer.

I am sure you will get pleasing results with your effort, but in general, speakers and speaker systems for PA use are MUCH more efficient than home stereo speakers. It would be like multiplying the power of your system. PA speakers are also designed to project sound out into the audience, rather than spread it around the room in the near field.

 

[psin3t]

I am not sure I came here to 'argue' about what I have already got

In my price range, Class D amps are strictly for 1500hz and lower. At higher frequencies their sonic shortcomings become audible.

Feel free to correct me with a link to a Class D amp with specs that match or better the amps I have (not in power - in fidelity) for the same or similar price.

I go for top-end specs - on a budget. Weight is not an issue. Most of what is said here is just opinion because if you think low-end Class D amps are 'sufficient', then we are not on the same page.

They are not.

Check the specs of the equipment included. Then check the price.

I got ALL THREE amps for $870 (2X 1200W [email protected] ohm >0.5% distortion, over 105dB unweighted!). All drivers: $50 + $200 + $300 plus shipping and currency conversion.

Tweeters: 150W RMS (8khz-20khz) - 102dB 1W/1m - 0.73kg each
Mid: 250W RMS (1.5khz-20khz) - 97db 1W/1m - 1.5kg each
Mid-low: 350W RMS (60hz-1.5khz)- 95dB 1W/1m - 5kg each
Sub: 350W RMS (30hz-60hz)- 94dB 1W/1m - 5kg each

I don't know what you call home stereo 'hifi' gear - but that ain't it. Opinions are great - just make sure you don't try and pass it off a 'hard fact'. These mains have already been tested and demoed in front of many audiophiles already. The sound is astonishing.

If you can point me towards products with the same or lower price that have better specifications, I would love to hear about it - please post them with specs?

Edit: Must return to essay writing for my science degree - back later

Cheers,

Adam

 

[psin3t]

Clearly, this is not about DIY at all - it is about 'Do It My Way'. Or maybe 'Do It This Way or Do It Wrong'.

All early responses are always resident cynics who - while having a reasonable knowledge base - have essentially devolved to only criticising DIY posts for not meeting their own criteria.

Sadly this is not even saddled in good-natured language - just bland cynicism loosely based upon reason. This is true for any aged forum with special interest. It is the primary reason I would usually never post.

It is hard to critique criticism, as you can only really come off as ungrateful, touchy or angry (you mad?). But the reality is that this system has more power and fidelity than what most people could ever hope to achieve for less than $1500.

Hence - long live DIY and good on me for having a go.

Just so you remember what this site is supposed to be about

 

[psin3t]

While Lanzar are the greatest name in audiophile equipment, ...[/url]

Hehe - correction:

While Lanzar are NOT the greatest name in audiophile equipment,....

 

[chris661]

Behringer NU6000, around 2KW/ch into 4ohm, <0.05% THD throughout its power range. With some excellent DSP, £300. You didn't read my link, did you?

I'm not entirely sure if you realise who you're talking to around here. Lots of use have degrees or PhDs in science-based subjects, and have been doing this audio thing for years. If you'd like to compare systems, I've just posted some measurements of mine. It's in this section. I'd be interested to see the curves from your setup.


In your initial post, you said you wanted some directivity, so that you're not throwing sound at nearby neighbours. In response to this, I suggested that you use compression drivers and horns, since that's the easiest and cheapest way of getting some directivity. Compression drivers will also handle much more power than small dome tweeters, which again is useful to you.

In all, it honestly does look like you're assembling a powerful home-HiFi system, and using it for PA use. The design criteria are different, and we're trying to show you that.

Chris

 

[JMFahey]

Clearly, this is not about DIY at all - it is about 'Do It My Way'. Or maybe 'Do It This Way or Do It Wrong'.

Funny you rise that point

It is the primary reason I would usually never post.

But you did ... am I missing something?

Just so you remember what this site is supposed to be about

Oh, we know.

You build something, post it here, Forum members read your post and answer, (if found worthwhile).

Possible answers are:
* questions
* suggestions
* corrections

* praise
* admiration
* adoration

maybe you expected the last 3 and none of the first ones?

 

[psin3t]

Let me guess. You own an iNuke too..

Sigh. Have fun guys. I am sure you know all about how what I made sounds in person.

GO BEHRINGER? Wow. Never thought I would get such awful advice here.

You are aware of the large market of non-China sourced amplifiers? You are aware MOST people in the profession will not use them?

No. You are not. You suggest the lowest possible quality. "Look - it is passable!'

Grumpy resident 'gurus'. Same as all forums.

'Change your 15 for a 12'.
'Get a Behringer amp'.
'You can't cross the hifi and PA beams or we 'SPLODE!!'

AWFUL advice all round.

 

[psin3t]

Basically, it is just contrarianism.

I would love to return with the properly measured output once it is finished.

But I see no point. No matter how well it comes out - for the little money it cost me - I will only be exposing myself to mockery from people who think that posting on a forum makes them the Lord of All Audio.

It doesn't matter how much time and effort went into it. Doesn't matter how much planning, mathematics, sound theory or smart compromises were made.

I have seen it on Car audio forums, horse forums, gardening forums and even local council.

If the resident critics didn't design it themselves, if you didn't choose what they would have chosen - then your attempt is for nothing - according to them.

The fact is, I am smart enough to know that you are wrong. Most wouldn't, sadly.

Do you really think that - when I am finished - I will decide:

'Man, that sounds so bad. I should have listened to those guys on DIYAudio. I need to rebuild my cabinets to fit a 12in instead of a 15in, I need Class D Behringer amps and a compression driver'.

No. I will not be saying that, for certain. NO sane person would.

I hope others who have experienced the same see this and take heart. Just because someone on the internet criticizes you, does not make them knowledgeable or correct.

Just like in religion, dogma dominates. It is not about physical laws - just belief.

 

[bitSmasher]

Are you still planning to use this outdoors at camping music events (doofs), or even hire it?
I'm curious to see how it'll handle that use/abuse

 

[psin3t]

Not interested now. If I could delete the post I would.

 

[chris661]

Let me guess. You own an iNuke too..

Sigh. Have fun guys. I am sure you know all about how what I made sounds in person.

GO BEHRINGER? Wow. Never thought I would get such awful advice here.

You are aware of the large market of non-China sourced amplifiers? You are aware MOST people in the profession will not use them?

No. You are not. You suggest the lowest possible quality. "Look - it is passable!'

Grumpy resident 'gurus'. Same as all forums.

'Change your 15 for a 12'.
'Get a Behringer amp'.
'You can't cross the hifi and PA beams or we 'SPLODE!!'

AWFUL advice all round.

Behringer X32 desks have been used at lots of major events around the world.
You said you're on a tight budget, so we suggest lower-budget items that will give good performance at that price point.
You said you want directivity, we give you some ideas how that might be achieved.
My suggestion to swap the 15" for a 12" was so that you'd be able to use more compact tops, and not lose out when a sub is added. I've lived with both 15" and 12" tops for extended periods, and I know which my back prefers.


It must be very difficult to tell, but we are trying to help you achieve some of the goals you set out.
That said, at this point you're just coming across as someone that thinks he knows much better than the rest of us, without much to suggest that he might.

I'd be interested to read your design considerations for the tops you have. There are some things I might have done differently, but my priorities may be different to yours.

Chris