Developing cheap speaker suitable for domestic Hauptwerk

[David Pinnegar]

Hi!

I have been working recently on developing a cheap speaker suitable for Hauptwerk for home installations. The 15 inch at the beginning of
http://www.youtube.com/watch?v=2I_9pxKPYXc
is the result.

The drums at 01:05 are an indication of the sort of bass which one can expect and it's better in real life. Driven by around 30-50Watts per channel a pair of these will quite realistically reproduce the organ spectrum but I need to experiment further with crossovers and phase.

Total cost of these units is under £160 per pair, which contrasts substantially with the very expensive and PA optimised active monitors that the Hauptwerk software writers like to to promote.

I have recorded with other top speakers for comparison.

Whilst making these test recordings it was apparent that the Manger speakers are very excellent near-field monitors and am sure that these, which a friend wants to sell, would work pristinely for a home Hauptwerk and h-fi installation.

Best wishes

David P

[KB7DQH]

Oddly enough, the Tannoy speakers had the best "dynamic presence"... based on what I could observe here...

Your 15 inch unit, dust cover removed, and tweeter mounted behind has a bit less  on the "high end" than the rest and as you say are less efficient.  I have seen small tweeters mounted in front of the woofer using the central magnet pole for support, but maybe working on the crossover could bring the high end up, possibly the "drinks bottle" cone helps???

Eric
KB7DQH

[David Pinnegar]

Dear Eric

It's an interesting experiment isn't it?!

I thought that the tweeter might be wired up in the wrong phase . . . and this proved to be the case. I've just been hearing "The Organ at the Met" - a recording of Matthew Copley's instrument at Edinburgh with three 32ft ranks and the speaker really brings it to life. Excellent reproduction of the flues, chiff, exciting reeds, mixtures but most importantly quite earth rattling natural bass.

Crossing over at around 1kHz, I was worried by power handling but I tested the tweeter at high output and it's been quite happy without signs of overheating and distortion and the unit is ratable at around 30W RMS, 50W-60W peak producing an adequately deafening domestic volume.

The secret of this is the matching of the two units both electrically and acoustically in terms of useful frequency response and sensitivity, as well as exact physical dimensions. I guarantee the results of this marriage to be better for home organ installations than Mackie PA speakers as well as significantly cheaper.

Best wishes

David P

[KB7DQH]

I thought that the tweeter might be wired up in the wrong phase . . . and this proved to be the case.

:o :o :o ;) ;D ;D ;D

A friend sent me a few links to an "audiophile" forum...  Whilst reading through posts made by a member whose system was auditioned by this same friend, I ran across a thread where this member had a contractor do what likely was thousands of dollars of work to the acoustical room treatments only to discover that one of his subwoofers was likewise wired out-of-phase! ::)  And this is after doing "professional acoustical evaluations ;D  Mind you, this guy spent more money on his "hookup cable" than I have blown on  the whole of my system...  He posted the story to make sure others don't "repeat his mistake" ;D ;D ;D   Fortunately the combination of reversing the wiring and the work on the acoustical treatments did result in "significant system performance"...

Whatever that means :o

   (Note to self: Make high-quality audio recording of "in-phase" and "out-of-phase" White Noise from the "THX Optimiser" track on one of my movie DVD's to serve as source signal ;)  That, with a reasonable "reference microphone" and the FFT program running on a computer should greatly speed up some of the "objective" audio measurements ;D

Speaking of "audio measurements"... I finally gave the "high-power" Audio dummy resistor a workout... This consists of the three heating elements wired in parallel, giving a resistance of 5.5 ohms... and a power handling capability of around 10KW... salvaged from a forced-air electric furnace.  This permits fairly reasonable measurement of the output power of a given audio amplifier
by simply measuring the voltage being applied to the element and doing a bit of math...   Likewise when evaluating speakers it can be placed in series with said speakers and similarly "doing the math"  Depending on what you use to "measure the voltage" one can actually integrate the power consumed by the speaker with the sound level made and plot a number of things 8)

Eric
KB7DQH

[David Pinnegar]

Hi!

Last night I thought that I reversed the phase . . . with not much apparent change in result recorded but in real life it did . . . and here's the unit with direct comparison to Manger:
http://www.youtube.com/watch?v=IezHNsuNI58

It's very much intended for organ work but doesn't do very badly on hi-fi either and indeed last night I spent a very enjoyable hour listening to the recording of St Mary's Edinburgh organ. The 32ft ranks nearly blew the back off the cabinet (which in its experimental form is only 2 inch lightweight foam panel) but were very impressive on the other side of the room. The cabinet is specifically intended to do well in this region when placed in room corners.

The cost is intended to help to make Hauptwerk affordable and the units supplied for self assembly should not cost more than £120 for a pair at the outside or £150 assembled.

Best wishes

David P

[KB7DQH]

 :o Foam panel?  I am familiar with the "almost open-cell" foam insulation board... and it is "fairly rigid"...  But I suppose for "quick-and-dirty" it is easy to form and lightweight stuff... 

But it reminded me that I have sitting beside me a rather intriguing speaker I found in the process of helping a fellow Ham radio operator whom I didn't know, but was living in a nursing home and a house he owned, all rooms filled with various bits of electronics, and used exclusively to store this collection, was structurally sound but nonetheless "declared a public nuisance" and the whole of the collection needed to be "made to go away" forthwith...  OK I digress...

Anyway this thing is built with no spider whatsoever, the voice coil bonded directly to..........
A Styrofoam diaphragm!  This particular unit gathered crud in the magnet assembly and/or was misaligned at the factory and the voice coil has always "scrubbed" the magnet so I never really used it for anything...   But it has given me an idea for "something completely similar" but using the "bog standard" 1/2" thick insulation board and one of the 1-1/4 meter diameter fiberglass Satellite
dishes I have a number of...  I just have to figure out which of my "scrap" loudspeakers will have to be sacrificed for the required hardware to see if my crazy idea will work, if at all :o ;D

Eric
KB7DQH

[revtonynewnham]

I thought that the tweeter might be wired up in the wrong phase . . . and this proved to be the case.

:o :o :o ;) ;D ;D ;D

A friend sent me a few links to an "audiophile" forum...  Whilst reading through posts made by a member whose system was auditioned by this same friend, I ran across a thread where this member had a contractor do what likely was thousands of dollars of work to the acoustical room treatments only to discover that one of his subwoofers was likewise wired out-of-phase! ::) 


Eric
KB7DQH

Hi

Some professional!  Actually, if there's significant stereo content it isn't always easy to spot out of phase - although with sub woofers, the lack of extreme bass should have given the game away.

The simplest way to check phase is to place the 2 speakers next to each other and feed them with exactly the same signal - preferably with low-frequency content (it's easier to spot phase problems).  If the units are out of phase, then the bass in particular will almost disappear.

I did once get caught out by a reverse connection on a balanced mic cable - fortunately I did a mono check on the recording and was able to sort the problem before the radio programme was sent to the station for broadcast!

Every Blessing

Tony

[David Pinnegar]

Dear Tony

Bass phasing is as you say an easy problem to spot but tweeter phasing is an interesting phenonoma - one only notices it with a slightly hollow sound as the phases cancel in the crossover region.

I'm not sure that I have noticed a lot of difference having, I thought, switched the tweeter phase but this could be on account of the effectiveness of the second order crossover, minimising the area of confusion to possibly only four or five notes, to which the crossover adds in any event.

Tannoy gets over the problems by arranging the crossover frequency to be exactly the half wavelength from tweeter voice coil to woofer coil, and thus reversing the phase at that point. The distance afforded by the good value woofer puts this frequency significantly above a 1000Hz crossover. There's mileage in changing the way in which the horn develops through the tweeter hole and either possibly cutting back the voice coil former flush to the cone as it protrudes beyond the cone, or even adding a whizzer cone.

However, as it is it's exceptionally good for reproducing organ and like the Manger, one can listen to it for long periods without tiring. Both the other top-end speakers I trialled in the videos have very forward treble which can create a super-realism with strings and harpsichord but certain recordings are difficult to listen to.

One such recording, which I thoroughly recommend is Simon Nieminski playing "The Organ at the Met", the Matthew Copley organ at Edinburgh. This is a true speaker tester - from memory 3 32ft stops and the upperwork in the recording is guaranteed to hit any annoying tendencies towards any high frequency resonances, which might work spectacularly in any large environment but are painful in domestic surroundings.

Best wishes

David P

[revtonynewnham]

Hi

Yes - crossover phase is a problem - not only is there the issue of relative phase between the 2 speaker units (sometimes both are in phase, whilst other designs put the tweeter in reverse phase - probably in an attempt to "hide" the crossover point).  Another issue is that the filter networks will change the phase relationship in a frequency-dependent manner - adding yet another variable to the equation!  I think that there's some advantage in using electronic crossovers at line level, and using individual power amps for each frequency band - but that obviously has cost & design implications.

Every Blessing

Tony

[David Pinnegar]

Dear Tony

Yes - active crossovers have been seen as a panacea but many purists rail against them especially on account of phase disorders and this is one reason why the Mackie type PA speakers that the Hauptwerk software writers seem to favour are not the bees' knees.

The Tannoys deliberately use out of phase tweeters as at the point of crossover, the delayed phase of the tweeter horn emerging at the point of the woofer matches up.

The 15 inch speakers provide a better realism at close quarters on account of being a point source coaxial solution and a frequency range that does justice to pedals at 16 and 32 ft and they do so effectively at ultra low cost.

I'd prefer to be using first order crossovers but the specific high power requirements of organ pedals together with frequency range extension requires better protection of the tweeter from low frequencies and causes better results to be obtained with a 2nd order filter at 1kHz rather than a 1st order filter at 4kHz.

I should add that the design is against my conventially held design principles which I believe hold good for large installations, but it works very well for domestic use.

Best wishes

David P

[revtonynewnham]

Hi David

Very interesting - I've just listened to the You Tube comparisons.  Obviously, the limitations of the compressed audio - and the listening conditions at this end - make it impossible to get more than a general impression.

The coaxial setup has advantages in terms of imaging accuracy (not that that's an essential ingredient of digital organ sound production).  It would be interesting to see some measured frequency & directivity plots - but given the need for an anechoic room (or possibly open-air - hardly practical at this time of year!) listening will have to suffice.

I look forward to your final conclusions.

Every Blessing

Tony

[David Pinnegar]

Dear Tony

More than merely imaging considerations, I always have the impression that coaxial speakers or dual concentrics as Tannoy market them have some sort of wholeness to the soundspace, certainly at closer quarters, which makes them less of what we associate with loudspeakers.

Using the cone of the woofer as horn of the tweeter gives a coherence to the total soundwave. I suspect that were one to mount the tweeter horn of a Tannoy outside the woofer area, the speaker would be much less successful. Certainly the Tannoy Mercury, no doubt designed on perfectly good and possibly similar frequency considerations as the dual concentrice, is no match for the coaxial versions of the same maker.

Best wishes

David P

[revtonynewnham]

Dear Tony



Using the cone of the woofer as horn of the tweeter gives a coherence to the total soundwave. I suspect that were one to mount the tweeter horn of a Tannoy outside the woofer area, the speaker would be much less successful. Certainly the Tannoy Mercury, no doubt designed on perfectly good and possibly similar frequency considerations as the dual concentrice, is no match for the coaxial versions of the same maker.

Best wishes

David P

Hi

I would agree. 

Every Blessing

Tony