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Old 21st February 2010, 10:40 PM   #41
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And here is the large horn that Andrew Bird uses on stage:

big horn
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Old 21st February 2010, 11:16 PM   #42
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by max axe View Post
...Anybody have a suggestion for a compression driver good for 200 HZ, moderate power of not more than say 40 watts? Im not very familiar with them...
Hi Max,

As you never put a cost limit so IMO for your purpose a suitable compression (horn) driver that can be driven 100 Hz below recommended. XO point = 300 Hz and can guaranteed put out a minimum of 124 dB SPL at 200 Hz is:

http://bmsspeakers.com/fileadmin/bms...mid_t_data.pdf

Quote:
Originally Posted by max axe View Post
...No chance of approximating the required throat geometry for 4 peerless 2 inchers?...
No problem at all. All you need is to properly use the HR and the hint is to correctly interpret the visual results that affect all output screens when changing the parameters.

Quote:
Originally Posted by max axe View Post
...I wonder how well Hornresp models the geometry of the throat? Of course there is no phase plug...but you can input throat area and volume, and then conical sections...
What are you aiming at? Did you find unwanted discrepancies in my posted HR plots using the 4 x Peerless 830970 drivers?

See the foundation/investigation and more (two picture I never intended to post but may be of some use?) I made prior to the posting of this one.

If you want to separate the ‘horn’ from the drivers in use, i.e. investigate the passive plots of the horn transfer functions, just enter a Zero Voltage = 0 V for the Eg value at the main HR input screen and then press the calculate button.

To find the throat impact: disable the expanding horn part, with or without a rear side closed box, but not the throat definition (areas and lengths) and repeat pressing the calculate button.

b
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File Type: jpg Peerless-830970-alt.JPG (459.0 KB, 139 views)
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Old 22nd February 2010, 06:27 AM   #43
max axe is offline max axe  United States
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bjorno

Thank you. I am swimming upstream with new tools. Thanks for your efforts and minimal but pointed hints (correctly interpret the visual results upon changing parameters; funny). GM said "...more drivers.. means a higher compression ratio for a given throat area which in turn means adding a filter chamber and phase plug, i.e. create a compression driver. For all but the most avid and/or knowledgeable, such a project is beyond the scope of DIYers. Ditto for designing/building a Unity concept horn."

So this led to the questions which you answered in your response. I didnt find discrepancies in your HR plots but in truth Im still digesting. I guess it could be very critical how one created the entrance into a horn, and using four drivers, I didnt know what the effects might be of abrupt steps in throat area etc. GM was not encouraging. So the compression driver was a possible alternative to unknown multiple driver throat geometries.

The nice extended range compression driver you mention indeed is costing about 600 Amerikan Dollerz. I will have to find something cheaper for now. On the opposite cost spectrum there is the MCM DU-40 for $22. Parts Express has the Dayton D1075T 75W for around $50, and I am seeing others in the $150 range. One of the Peerless 2 inch in my test horn is amost as loud as required except in the low range where it bottoms out. I dont know how much a crossover might help with this. But the point is that I may not need ultimate SPL. I do have a mic in front of me during performance.

My apologies for the long and stumbling posts, but I hope you kind folks might help me along a little bit more as I am making some progress thanks to you, and the time for construction is closer.

Max
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Old 22nd February 2010, 11:03 AM   #44
max axe is offline max axe  United States
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bjorno

Some thoughts when duplicating your small horn with 4 peerless;

It seems there is no way to really horn load them unless one wants to accept multiple peaks of 10db. With your approach, It seems that the horn enclosure does little to modify the response or improve sensitivity. The lower region is modified by the rear enclosure volume. Sensitivity grows by 6 db due to 4 drivers, from 82 to 88 db. Then I wonder why you chose half space instead of full space for the radiation environment. I would guess the unity design is similar in that there is no boost from horn loading the lower midrange because of limitations in the horn size...or is that true? Using fullspace and the four peerless, 1.7 mm extension, the maximum SPL is driver extension limited at 105 db below about 350 hz, cutting off at 12db per octave. At least that is what my foray into HR indicates to me.

Your thoughts?

Thank you,
Max
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Old 22nd February 2010, 03:20 PM   #45
GM is online now GM  United States
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Quote:
Originally Posted by max axe View Post
Thanks for your efforts and minimal but pointed hints.........

GM said "... I guess it could be very critical how one created the entrance into a horn, and using four drivers, I didnt know what the effects might be of abrupt steps in throat area etc. GM was not encouraging.

The nice extended range compression driver............
There are 'bottom feeders' who browse the forums looking for others intellectual property to use for their personal gain, so some of us choose not to elaborate in detail on some subjects, though we're ultimately fighting a losing battle because there's some folks who apparently believe that all should have access without having to do any extensive 'due diligence' judging by their postings.

Hey! Don't take my word for it, just do a 'Unity' search for design theory/proof-of-concept builds threads to get a reality check on what it takes to do one right.

That said, you can either follow Tom Danley's suggestion when asked about DIYing a Unity over on the HE forum or if you can hear your music good enough when 'buried' in considerable harmonic distortion, then start with the original Unity's WG and mount one Peerless on each side as close to the throat as its effective piston diameter will fit and cut off the receding excess, then bolt a fifth one at this new 'throat'.

If it still excessively exceeds Xmax/bottoms out at high SPL after digitally EQing to shape its response as required, add a 4th order digital high pass at whatever frequency yields an acceptable diaphragm excursion Vs distortion and keep spare drivers on hand since these aren't 'bullet-proofed' for PA apps.

Hmm, forgot about these relatively new duplex compression drivers........ yeah, this probably would be an acceptable solution on a big enough WG.

GM
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Old 23rd February 2010, 09:29 AM   #46
max axe is offline max axe  United States
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Playing with Hornresp, It seems that even four 2 inch peerless are pretty well excursion limited. Using a very small enclosure, you can barely put in one watt before they bottom out. Does that seem right? Its naturally rolling off at 200Hz. This limits the SPL to about 92 db.

I didnt find specs on low-mid compression drivers. I wonder how the cheaper ones would compare to 4 of the two inch peerless using a less than optimum horn. I put in specs for one Tang Band W4-1337SD 4", again using a very small enclosure, it appears to be nearing 100 db at 8 watts. But I could not tame the 8 db peak and valley. I knew I was bottoming out in my little tests but I wasnt sure exactly what was going on. I guess 200 Hz was aiming too low! But I am not quite grasping these small full range drivers. It seems either you would need to limit the low end with a x-over, or feed them no more than a watt, and forget ported enclosures.

I have not completely given up on the small mouth horn loading, even facing disdain and abhorrence from the audiophile community. (Imagine how much distortion is willingly added to guitar amps). The reintrant horn was as strident and honky as you would imagine, not at all acceptable, but an inline 24 inch cone with flare at the end sounded quite satisfying with horn and sax.... try suspending disbelief. The reason its tempting is because it fulfills the visual goal and does add many db SPL. If only one could reduce 3 or 4 peaks from 400 hz to 1k...

max
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Old 23rd February 2010, 02:30 PM   #47
GM is online now GM  United States
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Correct, you have to enclose the back side of the driver to balance out any horn loading, so read up on how to use Vrc, Lrc to add a sealed rear chamber and Apt, Lpt to see how venting it affects the response.

Again, the Unity horn is too small to play down to < ~1 kHz with the 1" exit conventional compression drivers unless multiples are used and my SWAG without working it out is that even adding four more won't do it and I assume the main reason for Tom creating his own with larger point source drivers.

GM
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Old 23rd February 2010, 06:50 PM   #48
max axe is offline max axe  United States
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Thanks

Read about the effect of Vrc etc where? Hornresp indicates a cubic enclosure 2.3 inches per side, no chance extending the length. Unless I missed something, any port allowed more excursion. Of course its undersized so there is a bass peak. Not the sort of gentleman's closed box 3db down tailoring perfection...

But thinking about a compression driver like the atlas PD-5vh. I dont find specs other than 110 Hz to 4k with full power rating of 40 watts down to 250 Hz. Now put a 2 inch driver into Hornresp, and check the excursion with a large horn at 40 watts and you see something like 4 mm at 250 Hz. Limiting excursion to what I imagine is more reasonable, say .5 mm (I have no idea, no specs!) you are back to less than a watt and low SPL, so I think I must be doing something wrong. I need to move forward...

Thank you

Max

Last edited by max axe; 23rd February 2010 at 06:58 PM.
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Old 24th February 2010, 01:14 AM   #49
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Quote:
Originally Posted by max axe View Post
Thanks

Read about the effect of Vrc, etc, where?
Max
Hi there: First Go to Hornresp help; page 4 for definations, page 9 for rear chamber, etc. Second google-up JHS Audio; click on Horn Design 02/07/06, 1/2 way down to the the paragraph on Hornresp, there is a information on what to look for in your design as you add then modify the rear chamber. Third, call up Hornresp and your design, add the chamber, go back and evaluate the effect, as discussed in step two, then prepare redo, redo, redo, redo untill you get the SPL response and other factors to meet your requirements. Pay close attention to XMax during every step along the way, (at the maximum Eg you intend to use on stage) as others have mentioned. You don't want to get on stage and blow the perfect note and the drivers at the same time! ... regards, Michael
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Old 8th March 2010, 06:54 AM   #50
max axe is offline max axe  United States
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Where Im at;

I actually ordered a Tang Band W4 656SC-4 For the yet to be constructed musical instrument mounted horn. Well, it feels too heavy (at 4 lb). Sounds light I know. So Im going back to my little peerless two inchers. It looks like with severely small rear chambers I can get as much as 110 dB with two in series without excursion limitations. The low cut off is 200 Hz.

My question at the moment is how to couple two drivers into the one throat. I wasnt expecting to have a useable freq range beyond 3k Hz. 1/4 wavelength of 3k Hz is in the 1 inch range. The question is should I fiddle with some kind of phase plug. Even without, its a question on how best to get two speakers into one throat. The throat is 5 sq cm, with 5:1 CR.

I am also waiting for a trombone bell from Ebay to play with. The flare is not right for good response. Conical is more ideal as indicated in Hornresp. But I havent entirely given up on the Karlson hybrid idea. I would make a paper mache or something test piece from the trombone bell and try cutting a slot to see if it improves response. Guess I will have to fire up a freq resp test software of some kind. If its no good, I may have to make a conical horn and live with the look.

Im still looking into the shaped TL bass design per bjorno's inspiration. Accepting less than flat response, you can get over 115 dB SPL, 50 Hz, with a 1.5 Cu Ft TL, 15 watts. By contrast, it would take four drivers in an enclosure 1/3 as big for somewhat equivalent specs. Is that a trade off worth consideration?

Thanks
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