Driver selection for waveguide hack synergy horn

[rhapsodee]

Hi Guys,

The PRV audio waveguide seems to be a good candidate and i'm very keen to start my own attempt at a small synergy horn.

Waveguide : https://www.parts-express.com/prv-audio-wg35-25-b-1-90-x-60-abs-waveguide-2-3-bolt--294-2892

Tweeter 1 :https://www.parts-express.com/peerl...c90-04-1-dual-ring-radiator-tweeter--264-1014

Tweeter 2 : https://www.parts-express.com/peerl...pression-horn-driver-2-4-bolt-8-ohm--264-1420

Woofer : https://www.parts-express.com/dayton-audio-dc130b-4-5-1-4-classic-woofer-speaker--295-307

i guess i'm still torn between using:
1. Ring radiator tweeter
2. Compression driver tweeter
3. 1.5 inch full range speaker

Is the dayton 5.25in woofer suitable? It has Qts 0.35, motor is not too strong at BL 4.89.

i guess matching all the components are important to distribute the cost and keep the chains in the link equally strong, as opposed to having an obvious weak link in one component. It seems the woofers would be hard pressed to keep up with the Tympany CD?

 

[xrk971]

I've used no name PE 5.25in woofers in a small Trynergy - 4 of them and found bass was not sufficient for higher SPL. Look for 7in or 8in woofers even with large excursion. In which case the shorter waveguides are too small. By if you are good with 90dB to 95dB SPL at near field - the 5.25in woofer can work fine. For the 1in throat waveguide you will have to go with a dome tweeter or compression driver.

This is from Trynergy thread:

As you can see the HD starts to rise due to limited excursion ability of these budget drivers.

Look at the following threads for more info:

http://www.diyaudio.com/forums/full...l-range-tractrix-synergy-118.html#post4551674

http://www.diyaudio.com/forums/multi-way/285030-bookshelf-multi-way-point-source-horn.html

http://www.diyaudio.com/forums/multi-way/286679-synergy-attempt-without-compression-driver.html

http://www.diyaudio.com/forums/multi-way/292379-small-syns.html

You might want to read the above threads as there is a wealth of info there that will save you time. Don't reinvent the wheel for lack of research.

If you want to go with dome tweeter or compression driver you need the woofer/mid to cross rather high at circa 1khz to 1.5kHz. This can be tough to do with a band pass injection port unless carefully placed and fitted with a volume filler plug.

 

[rhapsodee]

Thanks X. i guess i don't have too good a feel of how loud 95db is in nearfield. For typical 2 way bookshelf speakers with 5 or 6in woofers, do they also start to increase in HD (run out of steam) by about this level? i find myself to be quite sensitive to distortion, i'd be the first to turn a speaker down when it get's too 'loud'.

I'm not trying to hit reference level, but i do need a bit more volume than nearfield desktop monitors. These would go in a living room for nice ambient music, not really serious 2ch listening. Well that's if they work out. Now it's just to get feet wet without spending a fortune.

I have been researching the various threads. Like you said, i'm worried about the XO being in the 1khz range. With the 1in waveguide, the PRV is limited in small full range drivers.

This 1in TB is 81dB, 2mm xmax. if XO at 600hz, would it be able to handle 95dB? More?
https://www.parts-express.com/tang-band-w1-1070sh-1-full-range-driver--264-863

i can then squeeze in 6.5in woofers like this one? It should fit in the PRV waveguide.
https://www.parts-express.com/pyramid-w64-6-1-2-pro-plus-midbass-woofer--290-025

Between the pyramid woofer and the 1in TB, which one would be the limiting factor in HD?

 

[xrk971]

I think four DC130's should do the trick. 88dB +6dB for series parallel and you get 94dB sensitivity. With 1W of power into 4 drivers distortion should be pretty low. 94dB at 1m is 88dB at 2m. 89dB is about "dance floor loud" you sort of have to yell to have a conversation. There is still headroom for about 6dB crest factor without distorting too much.

Dayton Audio DC130A-8 5-1/4" Classic Woofer Speaker

 

[rhapsodee]

X, you're saying 4 DC130s per side? Which tweeter should I use with that? Either the XT25 or the tympany compression driver for a ~1khz xo?

4 woofers would be too much for the 1in TB full range?

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[xrk971]

The horn will add 10dB sensitivity to a full range driver. So a 84dB full range (typical) will be perfect. A full range driver is easier to cross over around 800Hz which is easier than pushing those woofers above 1kHz.

 

[rhapsodee]

OK, the 1in TB is only 81db and 2mm xmax, I think it may not keep up with 4 dc130. Also prefer 2x woofer per side to keep the startup cost lower.

So with 2 woofer per side, is 2x dc120 better, or 2x the pyramid 6.5in woofer better?

I should model the woofers in a bandpass enclosure, how do I figure out the flare in the PRV waveguide? Also, I couldn't figure out how to get to the multi entrant horn wizard in horn response.

Last question, assuming spl is within HD limits and response eq to flat, will the 1in TB sound different in the treble compared to the Vifa xt25?

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[rhapsodee]

Guys,

i'm about the pull the triggers on the hardware. Does anyone have the PRV waveguide on hand? i'm wondering if it can actually fit the DC160 6.5in woofer vs the DC130 5.25in woofer on the side of the PRV? Could i trouble you for a measurement? It's close from my estimation, either the DC160 just fits, or it's too big by a half inch maybe.

Thanks!

 

[bwaslo]

rhapsodee -

With the PRV horn -- On the side surfaces, you have 6" max from the throat (under the tweeter mount) to the end of the flair (before the horn's mounting surface) on the outside. On the top/bottom there is about 5.25" max.

In either case, there isn't room for a circle of that diameter on just the horn wall, but you're going to need to attache a mounting board anyway (the walls of the horn look flat, but they aren't). You will need to put a completely flat mounting board or plate for the woofers and seal under it with something. I used epoxy putty (with a SEOS15 horn) for attaching the plate and sealing under it between the horn's outside wall and the board. My mid drivers are smaller though (4"D).

 

[rhapsodee]

Thanks Bill. DC130 it is then.

I tried modeling the multi entrant horn in horn response, but am struggling to enable the function. Been reading the help file step by step, but seem to be missing something. Is there a guide or tutorial on this that I have missed? Most posts are on the results, not how they did it in HR.

Thanks!

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[bwaslo]

rhapsodee,

see the pdf file that goes with my SynergyCalc spreadsheet. You don't need the spreadsheet (though the PRV horn shape would probably be close enough to what it can model that you can get the values to use in HornResponse by playing with cutoff frequency and vertical/horizontal angles till the dimensions come out about right). The pdf file does tell you how to set up HornResponse for offset driver speakers (and what to watch out for in the numbers you put in!).

 

[rhapsodee]

Many thanks!!

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[rhapsodee]

The items have arrived! So it looks like the 1in TB full range is too large for the 1in horn. The cone is the same diameter as the horn, but that leaves the entire rubber surround bigger than the throat. My options are:
1. Make a gasket spacer for the surround, and mount the driver as is.
2. Try to enlarge the horn throat using a radius router bit to fit the entire cone + surround of the 1in TB full range?

Option 1 is easy but there will be a lot of gaps where the gasket provides clearance for the surround. Will this cause nasty dips?
I think option 2 was done by bush on his SB full range in the xt1464 waveguide. Worked great. Any downside, like messing with the throat geometry, it would be like a venturi shape, wide(where I enlarge it) -narrow- wide again.

I'm actually travelling this week, parts arrived Sunday afternoon so I didn't have time to do anything much with them..

Thanks!

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[xrk971]

Take some MdF and stack two pieces to get 1in thickness. Take a 1in hole saw through it. Take a wood file and work on making an adapter to go from dia of driver plus surround to smoothly taper to 1in throat. Add some felt as gasket between TB driver and adapter - should work to get you out to 20khz with EQ +10dB Q=0.5 from 4khz high shelf.

Or if you have 3D printer simply print it. Something like this:

 

[bwaslo]

How about taking a file to the throat of the horn and tapering/widening it just at the top, and just enough so that the surround won't rub (kind of like on xrk's adaptor sketch)? If you have a small router and and a ~45degree roundover or bevel bit for it, you might be able to do it with that.