Something Stirs in the Workshop

Dedicated to those large boxes at one end of the room
vinylnvalves
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#136 Re: Something Stirs in the Workshop

Post by vinylnvalves »

Having read an article about the precide Kithara speakers this week, I had a though ( I know thinking is dangerous), which maybe answers the question of how to integrate the midrange AMT’s I have - utilising the bipolar response. The challenge has always been what to do below the AMT, as bipolar waves aren’t easy, unless you take the Beolabs approach of multiple drivers.

The Kithara speaker has an upward firing midrange driver, similar to Linkwitz Pluto. So my thoughts are use the Beyma 12p80nd driver firing upwards, gets around the beaming issues.
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Using a forward and maybe a rear waveguide on the AMT, with a dispersion cone under it to control reflections off the wave guide by the midrange driver. I have seen some suggestions of inverting the midrange driver to get better dispersion.

Will end up looking like a number of omnispeakers such as the Duevels. Only ever the Duevel bella’s once and cannot say they were memorable, mine will be on steroids though as cone area will be a lot bigger. Like the Pluto’s though in a small room.

Thoughts, or your experiences of these type of speakers please, trying to understand if the benefits outweigh the refractions inherent with these type of designs.
vinylnvalves
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#137 Re: Something Stirs in the Workshop

Post by vinylnvalves »

Another prototype becomes reality... A plagiarised design for use with planar drivers or an array of 3” full range drivers. To hopefully cover 300 hz to 20 k without any additional drivers xover etc. I have some of the new BG cloned planar drivers from GRS to try out first.
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The WAM show is going to Yorkshire this year so I am hoping to get a room, to show that “ horny” speakers work in small rooms.
I have the back up of my existing system if this latest prototype ends up as fire wood. If there is promise may have to get Chris’s help with a conventional xover for it.

Interestingly I got some feedback on one of the es290 horns I made , it’s being used now with a BMS 4592 driver. Apparently someone has designed an acoustic lens to get rid of the beaming you get if listening at less than 10m. Keith seems happy, selling off a lot of his exotic compression drivers to buy the BMS ones, and having more money than when he started. Shame I let my BMS drivers go the Chris, as would have been an interesting to see if the lens do as are claimed, in the ES290 horn.
chris661
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#138 Re: Something Stirs in the Workshop

Post by chris661 »

If we get together to play with those new horns, I can bring a BMS along to try if you like.


I must admit that I haven't got around to doing much with them just yet. There's thought towards a Synergy horn build for PA use, but it's very much in the contemplative stage at the mo.

Chris
vinylnvalves
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#139 Re: Something Stirs in the Workshop

Post by vinylnvalves »

I have 3/4 of an es290 horn somewhere in the garage... I would need to get the 3D model of the acoustic lens so I can print one. The es290 is a bit of a distraction currently. Seeing if this one with the planar drivers, or maybe Mark drivers is any good would be my main focus - and aim for the WAM show.

I am testing and listening to the horn, with Dave “golden ears” tomorrow, to see whether it’s worth wasting plywood on a second one. As 9 months to get something ready for a show is a short time. The bar at the WAM show is set by Steve’s red open baffle transmission line speakers, so not that high 😉.
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#140 Re: Something Stirs in the Workshop

Post by steve s »

vinylnvalves wrote: Fri Jan 13, 2023 3:53 pm

The bar at the WAM show is set by Steve’s red open baffle transmission line speakers, so not that high 😉.
Not a particularly high bar steve, but nevertheless nice to hear.

A mate is cutting me some wood so hopefully when rhe weather improves I'll start another speaker build

At the moment I'm in a state of confusion, so it's going to be more of a test rig.

I'm really happy with the bass and lower mids and everything else really,
But I wonder if there's room for improvement.
I've got this idea for none reflective, more wave guides than horns !

I'm sure it's not a new idea but it's new to me !
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
vinylnvalves
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#141 Re: Something Stirs in the Workshop

Post by vinylnvalves »

Dave came around to listen and chat.
We connected up the speaker, after I found some bell wire in the garage. Quite a small horn really - sub only being used as a stand.
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It’s always hard to qualitatively assess the attributes, with only one speaker, but it seems to have body and airiness and spades of detail. Covering the 300hz to 18k nicely. I need to find some time to measure it properly. I can get it flat with the DSP what ever it throws my way. Replicating that in a conventional crossover will be the challenge. Also need to experiment with acoustic resistance at the back a closed box will kill the airiness, so foam or wadding maybe enough to get the cardioid response pattern to work well in any room.

There was some discussion of whether 4 2.5” FR drivers would sound better, an experiment for another day.

Steve - all my recent horns are really only waveguides- they only really help in a domestic environment, not at Owston.
chris661
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#142 Re: Something Stirs in the Workshop

Post by chris661 »

Steve,

If you're thinking about 2.5" drivers, the SB65 is worth a go. Nice little driver with a copper sleeve on the polepiece for demodulation.

Chris
vinylnvalves
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#143 Re: Something Stirs in the Workshop

Post by vinylnvalves »

Got a chance today to measure the new horn arrangement. Either my measurement technique is up the swanny or something is really bad with these drivers. Measurement to centre of horn at about 700mm distance
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.

The measurements arent aligning with the input signal. Feeding the drivers with a signal that has a LR4 xover at 350 and or 600Hz, and i still get a massive spike around 150hz, where it shouldnt be seeing a signal. Also the driver seems to die according to the measurements arounf 3KHz. It definitely isnt dying from the chirp- i can hear it loud and clear at least upto 10KHz.

The red trace is where i flipped the horn so it was effectively the drivers playing into the room OB, the 150Hz peak is most pronounced for this one. I have disconnected one driver and tried changing polarity between the drivers with much change which should yield a big suckout. Best response was when i used the MLS instead of the chirp (green trace).

It sounds quite balanced - should sound awful based on these traces.........
vinylnvalves
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#144 Re: Something Stirs in the Workshop

Post by vinylnvalves »

As my traces don’t look like.... these from Troy’s measurements.
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.

So maybe some help needed from the measurements specialist... up near Sheffield :D
vinylnvalves
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#145 Re: Something Stirs in the Workshop

Post by vinylnvalves »

With a fresh mind this morning... i had another look at what was going wrong with the measurements. Looking at the settings - it became apparent that windows being helpful had its onboard audio as the default settings.... changed that to the external soundcard/phantom mic drivers and all is good again.
Carried out three measurements - 0 30 and 45 degs. I am a little disappointed with the frequency response past 11k.
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So all is good in the world and i can trust my hearing over bogus measurements. Time to plan and machine another horn, - makings of a system for the WAM show is developing. ( Dont worry - Owston is the dummy run!!)
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#146 Re: Something Stirs in the Workshop

Post by IslandPink »

I'm glad you got that sorted out, and interested to see what you are developing for October.
Is the drop-off above 11k just a consequence of equalising the curve lower down ?
I mean - horn-loading will tilt the frequency response of the unloaded driver. It might only be possible to extend it by increasing the magnet strength ?
"Once you find out ... the Circumstances ; then you can go out"
vinylnvalves
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#147 Re: Something Stirs in the Workshop

Post by vinylnvalves »

The driver alone according to the manufacturer looks like this..https://doc.soundimports.nl/pdf/brands/ ... -sheet.pdf

Can equalise the response, whether I need above 12k for a group of over 40s is questionable :D
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IslandPink
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#148 Re: Something Stirs in the Workshop

Post by IslandPink »

Ok so the driver drops off anyway, but i think the horn-loading won't help because it'll pivot the whole response curve as it flattens the bit under 10k.
I do think you need a bit more, and maybe your ears will tell you that on cymbals and bells & suchlike. It depends a lot of what the phase does, if the phase stays flat right to 11 or 12k it won't be so bad, but it may be that it starts rotating earlier, in which case it'll sound like it lacks 'air'. Equalisation won't help that, but I would do that anyway, as you know .. :)
"Once you find out ... the Circumstances ; then you can go out"
chris661
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#149 Re: Something Stirs in the Workshop

Post by chris661 »

Just a quick note that FIR-based DSP can manipulate frequency and phase responses independently of each other.

ie, you could dial in a boost/cut without any phase shift, or dial in phase shift without changing the frequency response.

Chris
vinylnvalves
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#150 Re: Something Stirs in the Workshop

Post by vinylnvalves »

this is the phase plot
es2502.jpg
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Chris - remember design brief - no DSP Wizardry - target market, believe it sounds worse, and like 2nd harmonic distortion, which this horn could accommodate as around 98db efficient
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