Compact PA - in a car handled by a single man.

[pelanj]

We are running a small outdoor festival with a 6x4 m stage. Since the area is surrounded by walls from three sides, a relatively low power PA is sufficient. In the four years, the sound guys had the following:

1. KV2 top + sub (looked like bandpass), all active. One of the subs burned during the show, a single one was actually still sufficient

2. HK Audio Actor system with 1 sub - this was a bit on the edge, but still passable.

The sound guy using these came in a Mitsubishi Pajero with 4 active monitors.

3. A homemade PA system, biamped - bass and tops had a separate amp. This one needed to be on a small trailer - but I liked especially the bass boxes - simple bass reflex with Celestion FTR15-4080FD - a single pair was sufficient even with the non-ideal placement (one on each side more or less). Last year it was with two other subs, but it worked this year really well without them.

This lead me to an idea - today, amp power is relatively cheap and class D amps are not too heavy. What would it take to build a relatively compact, light (neodymium speakers) and not too expensive three way system with great performance? The contitions are the main PA must fit into a larger car or a small trailer and all the boxes must be as light as possible to be easily handled by one man. Any inspiration from your systems would be appreciated

Recently, these boxes were linked in a thread here: Soundgear - Speakers - Amplifiers - DSP - these with a sub would probably work if the dispersion was not as narrow. Also, these would be too complicated to build.

I would think a 15" BR sub, with a 12"(15") + 2" top could be great.

For an even more compact solution, if the sub could play up to ca 400 Hz, the RCF H6000 8" horn + a 1" driver could maybe work as well - a sort of passive RCF 6001 split into two boxes with the low part playing a bit lower.

Or are my ideas completely off the limits?

I 've got some huge bass and midbass horns, but these need a large van to transport - but I would be willing to do a bit of compromise between the efficiency and sound quality and smaller dimensions - for smaller venues like the one described.

 

[kipman725]

Chris's stuff sounds good: PA Systems | grimshaw-audio
two high end 10", 1.4 inch comp, I think this horn? Product Detail - RCF
15 inch subs tuned high 40Hz? for compact boxes

Trade off is for small and loud is expensive drivers and lack of the lowest bass.

 

[Pano]

Interesting puzzle. One which a lot of people would like to solve. From the looks of it, you are trying to get loud, right? Any idea of SPL at a given distance? The angle look pretty narrow, so that helps. A good Synergy horn and sub on each side would probably do, but would not fit in most cars.

I see a lot of small gigs these days down with powered speakers from QSC, JBL, Yamaha, Mackie, etc. Tops and subs. Is that enough for your needs?

 

[pelanj]

kipman725: This is the tradeoff I am willing to accept. The PA systems used in the past (the HK Audio Actor system) has a -3 dB point at 48 Hz - PRODUKTARCHIV - ACTOR DX System - HK Audio The system you posted looks really nice - if something similar would be possible with a 1x12 instead, it would be perfect.

Pano: It actually does not need to be too loud. It is used basically to get vocals, keyboards, electro-acoustic instruments, bass and drums to the level of guitar amps. In this small area, it can get louder than comfortable. The puzzle was solved already by these two guys. So I think it is about optimizing the box sizes. E.g. smallest 15" 40 Hz tuned subwoofer and a compact top. Unfortunately, I did not measure the SPL (I should have done that, now that I have an iPhone!). A pair of active 1x12 and active subs should be fine, but I would like to use a small rack with class D amps instead. In previous years, we had guys with a 2x12+2" and 2 and later just 1 18" sub - and that system was actually louder than needed, I asked them to turn it down not to be too loud.

I was acually surprised by the bass from these little boxes. The tops should not be such a problem.

 

[pelanj]

So I think the best would be to measure my trunk dimensions and try to fit in some reasonably large BR boxes with Nd magnet drivers. That should be some fun. I think I will go for a 1.4" HF driver in a large horn. I will also try a pair of BC 8PE21 (that I bought for another project) with the H6000 horn below that and some nice 15" for the sub.

 

[chris661]

Chris's stuff sounds good: PA Systems | grimshaw-audio
two high end 10", 1.4 inch comp, I think this horn? Product Detail - RCF
15 inch subs tuned high 40Hz? for compact boxes

Trade off is for small and loud is expensive drivers and lack of the lowest bass.

Thanks!

You've pretty much got it. Different horn, though. Drivers below:

HF - 18Sound ND1460 on an RCF HF94
MF - Faital Pro 10FH520
LF - Faital Pro 15HP1060

Main speakers are 2x10" + HF, and I have eight subs.

I was running four subs in total here: YouTube
Look for the little black boxes half way up the stands. That was 85dBC-slow (103dBC peak) at around 280' from the stacks.


Looking at what you've had so far, a cut-down version of that system (1x10" and 1x15" per side) would likely out-perform the systems you've had previously.

One other tradeoff of my system is that it's quite power-hungry. I have 1KW on tap for each 10" driver.

Chris

 

[pelanj]

Thanks for sharing. That sounds good. And the drivers you used are easily available, which is a big plus for me. So it looks like it is possible.

 

[chris661]

Last thing - the subs are tuned at about 40Hz. Compact reflex boxes with plenty of port area.

None of what I've done is revolutionary - just sensibly-designed cabinets, really good drivers and lots of power.

Chris

 

[Think]

A better setup of the speakers would give a louder and cleaner sound as the setup in picture 1 is a comb filtering disaster.

Better not mix speakers putting out the same frequencies and never put top speakers (mids/highs) in the horizontal plane when they put out the same signal. The 2 bullet tweeters top box in pic 5 should never have been build.
I would leave the top boxes at home, put the speakers a bit higher, point them a bit down and put the upper speakers upside down so the horns (high frequencies) are as close as they can be.
If you play stereo; rotate the lower speakers inwards and the upper ones only a little bit. This will give the least comb filtering and the best stereo experience.

All subs should be together at a wall or be at least 5 meter (more = better) away from walls.


For a new system I would go with top speakers with multiple 6.5" or 8" drivers, as they will have better off axis response and more detailed mids. 2x8" with 2x200w will outperform a 12" with 800w in output.

A while back I was looking at 4x 6fe200 (€37) in 16Ohm; these can live in a tiny sealed box and make a 100 dB/W 4 ohm speaker which can be fed a kW of program power. Which would make 130dB minus power compression. But as the power is spread over 4 voicecoils this loss will be less then with 1 or 2 driver(s).
You can cross these higher to a tweeter then bigger drivers, so you have more choice and less cost (and weight) for the tweeter. A 1" tweeter will also have better performance above 10kHz.
Add subwoofers to your liking and cross them <150Hz.

 

[pelanj]

Another interesting suggestion, Think. The PAs in the pictures are not mine, they just illustrate the size/SPL I need. I think the horns in the 15" boxes were not functional.

The 6fe200 would be in a line, horn on top or in the middle, 2x2 with horn on the top or 2x2 with horn in the center?

 

[pelanj]

I somehow like the idea of the 4x6" with horn in the middle, it would look similar to the traditional 4x10 bass guitar cabinets. With the correct horn matching the dispersion and woofer depth, the crossover should not be too difficult to have a time-aligned speaker. This definitely goes on the potential project list Aiming for 150 Hz crossover point should be also really easy. I would use 4 ohm series-parallel and a 8 ohm compression driver. What would be a good crossover point with a 70 or 90 deg round waveguide? Something like this one: Megaton A7070 zvukovod | Reproduktory - Zvukovody - Zvukovody 1" | PRODANCE (measurements with DE25 here: http://www.prodance.cz/protokoly/megaton_a7070+de25.pdf )

 

[Pano]

2500-3000 Hz maybe? It's small. The baffle face might help some.

 

[pelanj]

In a 20 l box tuned to 100 Hz I get 120 dB/1m at the specified input power (a little more than 600 W). Which is about the same with a single Faital Pro 10FH520 in a similar sized box.

 

[chris661]

How do they compare for cone excursion?

Chris

 

[kipman725]

6FE200: SD = 118cm^2, xmax = 4.62 mm, $47.00 (parts express)
4*6FE200: SD = 472cm^2, xmax = 4.62 mm, $188 (parts express), Volume displaced 0.218064 litres
10FH520: SD = 321 cm^2, xmax = 7.25 mm, $267.00, volume displaced 0.232725 litres.

So pretty close to the linear displacment of the 10FH520 but lower cost and greater surface area (reduced cone excursion for given SPL), higher maximum crossover frequency. I would say it looks like a good option if that form factor suits you.

 

[pelanj]

In hornresp, the excursion limited SPL at 150 Hz is 121 dB for both, the 4x6 combo is a few tenths higher - therefore I say it is practically the same - but the 10FH520 is 8 ohm. So a pair in parallel would put out 6 dB more with a stronger amplifier. The 4x6 option will weight 4,3 kg more per box, that is acceptable for me.

 

[pelanj]

A single Faital Pro 15HP1060 in a 62 l box tuned to 40 Hz can do 125 dB from 40 to 150 Hz easily. That is comparable to the pair of the boxes with Celestion FTR15-4080FD that played during the last event. All that in 1/4 of the total box volume and with half the power. Very impressive. So a very minimal system would be the two tops with one sub and in theory the output will be beter or equal to what we had. I have a pair of DE500 drivers, these should be a good match for the total power handling and output as well.

 

[chris661]

A single Faital Pro 15HP1060

Good drivers. They get the thumbs-up from me.

Chris

 

[kipman725]

In hornresp, the excursion limited SPL at 150 Hz is 121 dB for both, the 4x6 combo is a few tenths higher - therefore I say it is practically the same - but the 10FH520 is 8 ohm. So a pair in parallel would put out 6 dB more with a stronger amplifier. The 4x6 option will weight 4,3 kg more per box, that is acceptable for me.

the 6" is also available in an 8 ohm version so you could use 8 per side to get the same results as 2*10".

 

[kipman725]

A single Faital Pro 15HP1060 in a 62 l box tuned to 40 Hz can do 125 dB from 40 to 150 Hz easily. That is comparable to the pair of the boxes with Celestion FTR15-4080FD that played during the last event. All that in 1/4 of the total box volume and with half the power. Very impressive. So a very minimal system would be the two tops with one sub and in theory the output will be beter or equal to what we had. I have a pair of DE500 drivers, these should be a good match for the total power handling and output as well.

worth noting that faital pro are using a more optimistic than normal xmax formula. They use (Hg+Hc)/2+Hg/3 wheras (Hg+Hc)/2+Hg/4 is used by other manufacturers and (Hg+Hc)/2 is the old standard. So the comparably priced RCF LF15X401 is actually on paper superior (for excursion capability) having a 15mm thick magnetic gap/top plate compared to 12mm despite lower headline xmax.