My 'Volks-OB' Mission Accomplished

scorpion · « **on:** 31 Oct 2007, 08:11 pm »

This is how German Klang & Ton should have done their dipole with Monacor SP 130/X8. However they made some mistakes and evidently had some bad Monacor SP-130/X8 units. I have now corrected them.

It is a 'Mother of Tone' design, all Spruce, but not very resonant in that elements all are secured by my 'patent' with Venetian Blind cord and strip seal, which is working beautifully. I shall treat these enclosures with Damar to see if that has any effect,

It is a very simple baffle, 40 x 16" with 90 degree wings 24 x 12 " in the low end to care for bass. Bass elements are AD 1524 from High-Tech Hi-Fi in Germany, link: http://www.traumboxen.de/ad-audio/r1524.htm , extremly good for OB. Bass is very clean down to 40 Hz in this design.

Crossover as I drive them now is active L-R 12 dB at 200 for bass and 300 12 dB L-R for Fullrange. These will be carried over to a passive design (calculated with MJK's worksheet), which I hope will still contain all he good virtues of this combo. I have ordered some exotic Obligatto capacitors for the crossover.

The Monacor units, I don't know if you can have them over there, are true Gems, link: http://www.monacor.de/en/produktseite_monacor.php?artid=5881&spr=DE&typ=u&spr=EN. They first appear as toy speakers but when you connect them they do play. Voice coils are made by paper! In fact I have a hard time to choose between this loudspeaker and my B200 combo. It's that good. The inside of the chassis legs are treated by felt to avoid back cone reflections. Respons inside my listening room is 35 - 20000 +- 5dB with some help of my Behringer DCX2496, but not that much. The B200's dissolution and separation is a bit better but you have to listen hard to get this. Some pictures:

Measured respones is like this:

The cost of this speaker as it stands now is about 140 $ per speaker, the passive crossover will raise that about 75 $. Hopefully the result will justify this amount.
The quality of these OBs compared to their price is nothing but sensational !

/Erling

ttan98 · « **Reply #1 on:** 31 Oct 2007, 09:23 pm »

Hi,

Nice setup and it is cheap too!

BTW what is rational behind using rope to suspend driver from the baffle, what's the advantage over screw mounting them on the baffle?

scorpion · « **Reply #2 on:** 31 Oct 2007, 09:32 pm »

It is supposed to be a 'Volks' design. Try this and see.

The same as by Magnet Mounting. Resonance free ! But simpler ! From the chassis. You would anyway get some influence from cone motions and pressure.
Depending on what you are using for baffles, I would say MDF is about the worst and probably Birch Ply the best and in between solid wood panels. About MDF I had to learn the hard way, I think even simplex is better.

In this case you can't compare cost to performance. You will be way up in the 1000$ league to get this kind of sound.

/Erling

ttan98 · « **Reply #3 on:** 31 Oct 2007, 10:18 pm »

From your design,

1. the woofer is mounted as Y or U configuration? Do you get any resonance with the
way you mount it or not at all?

2. you use DCX2496, did you feed the cd digital o/p directly into the DCX?
I am using biamp and analog x-over at the moment? I am thinking of moving
to DCX, your opinion, any real sonic advantage? if so elaborate.

3. The place where you live you can get many varieties of woofers at really good price but
not the place where I live.

thanks..

scorpion · « **Reply #4 on:** 31 Oct 2007, 11:06 pm »

ttan98,

By the way, about the cheap 12" woofers before, I think it is a Goldwood/Senon design available almost everywhere. There is a 15" unit which might be interesting.

Bass baffle is a topless U, nothing special. No resonances what-so-ever !

Regarding DCX2496. I think it by itself is a very capable unit. I drive it SPDIF from CD. It outplayed my Sony CD by a big margin, it also outplayed
the DAC-AH Nos dac easily.

The A&D 1524 is probably a HIGH-TECH HiFi designed unit, but they all come from China, HongKong.

/Erling

ttan98 · « **Reply #5 on:** 31 Oct 2007, 11:29 pm »

I can't even get Goldwood here(in Australia)

I can get Eminence, by the time they get here, the prices are inflated, due to
1. transport cost
2. higher markup, less competitive here because the market size is small

In general there are less variety here and prices are inflated.

I use 4*12in el' cheapo woofers($20 each, 2 per side)) with Qts=0.55 they seem to work quite well.

thanks for sharing.....

scorpion · « **Reply #6 on:** 31 Oct 2007, 11:44 pm »

The Eminence Alpha 15 would be a very good candidate for this design. The A&D 1524 may produce a bit dryer and distinct bass, however.

/Erling

weidok · « **Reply #7 on:** 2 Nov 2007, 08:41 pm »

Quote from: scorpion on 31 Oct 2007, 11:44 pm

The Eminence Alpha 15 would be a very good candidate for this design. The A&D 1524 may produce a bit dryer and distinct bass, however.

/Erling

Hi,

nice topic,

I am planning to build an OB with the A&D 1524 and the Fostex FE 167 E
The A&D are out of stock at this moment so i will have to wait a while..

Hope show the building process here soon... sorry

scorpion · « **Reply #8 on:** 2 Nov 2007, 09:27 pm »

Yes, I got the last two Thomas Herget had at home.

I also got most of the crossover components to be able to set it up passively.
Crossover is parallel with speakers in phase, Linkwitz-Riley characteristics 12 dB/octave.
Bass is fed via 12 mH and 47 uF for low-pass at 200 Hz and SP130X/8 with 30 uF and 8 mH to give 300 Hz high-pass.
No Obbligatos so far but this I hope will only change Fullrange tone to the better, now the 30 uF is a combo of bipolar, Mundorf M-Cap and a Jantzen polyester cap. Sound is very good also with passive drive, all the good virtues from the active drive is carried over. I had to take down bass-level about 3 dB with a 3.3 ohm resistor. Sensitivity at 1 kHz/1 watt/1 meter is measured to 93 dB.

Measured response (1 m distance at Fullrange height) is 43 - 20000 Hz +- 4 dB like this:

/Erling

ttan98 · « **Reply #9 on:** 5 Nov 2007, 01:43 am »

Scorpion,

How do you ensure your FR measurements at low freq, ie below 300Hz is as accurate as can be? The s/w I use Soundeasy measured at 1m does not gurrantee the accuracy below 200-300Hz, using digital MLS technique.

Can you elaborate the technique you use for good accuracy?

thanks....

scorpion · « **Reply #10 on:** 5 Nov 2007, 09:13 pm »

I am using the ARTA software: http://www.fesb.hr/~mateljan/arta/news.htm. It uses several techniques for FR measurement. The MLS method is considered 'inferior to swept-sine or periodic noise driven systems when implemented with a regular PC soundcard', quote from ARTA manual. Periodic pink noise gives the most robust estimation.

In the Manual I have found nothing about difficulties with low end estimates. But my system is not very sofisticated. The soundcard is a Creative X-Fi and has passed ARTA's test with very good result. I am using the soundcards mic input directly and uses the periodic pink noise for exitation. My microphone is home built with a Panasonic WM-61A electret capsule, which is universally acclaimed for excellent performance. I have however not been able to calibrate the microphone as I have no access to calibration instruments. I have however compared the ARTA measurements to measurements made with Radio Shack's digital SPL meter and pink noise under the same circumstances. The two measurements show so striking similarities that I would like to conclude that they support both measurements with credibility. The pink noise is discrete standard 1/3 octave frequencies but the periodic pink noise is a continous spectrum of frequencies. The ARTA should therefore perhaps give a better overall esrtimate.

I am confident that they will not miss the thruth by much.

/Erling

jonners · « **Reply #11 on:** 11 Nov 2007, 09:34 pm »

Quote from: scorpion on 31 Oct 2007, 08:11 pm

It is a 'Mother of Tone' design, all Spruce, but not very resonant in that elements all are secured by my 'patent' with Venetian Blind cord and strip seal, which is working beautifully.

I tried your 'patent' method but using plastic cable ties instead of Venetian blind cord. Thanks, it works well.
John

scorpion · « **Reply #12 on:** 11 Nov 2007, 10:46 pm »

OK, John, sounds fine.

Probably won't be long now til we have the Single Rope Speaker in the now Enlightend World.

/Erling

scorpion · « **Reply #13 on:** 21 Nov 2007, 06:26 pm »

Obbligatos are now in place and have been playing for a week. I am extremly pleased by the result. Here is the final 1m frequency response I have taken:

This you can trade for any speaker in the world and all the good sound is also left with the passive solutiuon.
Much more for instance if compared to my B200 combo passive and active.

/Erling

ttan98 · « **Reply #14 on:** 21 Nov 2007, 10:29 pm »

Sciopion,

You are using one woofer in your setup, do you think you would get better performance from using 2 woofers instead, ie get more impact, ie moving more air?

I am tossing up between using either 1 or 2, 15in woofers any comments?

richidoo · « **Reply #15 on:** 22 Nov 2007, 12:49 am »

Mighty impressive scorpion, congrats! I bet it sounds awesome. Thanks also for your opinion of DCX2496. Glad to hear it is not so bad as stock. Several ACers are working on modifications for it. Perfect for tweaking in a new speaker.
Thanks
Rich

scorpion · « **Reply #16 on:** 22 Nov 2007, 01:52 pm »

One or two woofers ? That depends on what speakers you are combining. With B200 I would go for two. In this combo I had to take down bass a bit
to get a balanced response. This bassunit is quite capable and you get a good impact from one basspeaker alone but OB-bass is never like enclosure bass, just
better and more dry. I would wholeheartedly recommend this german High-Tech Hi-fi unit for OB, link above.

I am using both DCX2496 and SCR2496, both I think are quite satisfactory in stock form. If you just would like a DA-conversion I would say that the SCR2496 is a bit better sounding in DA-conversion than the DCX2496, probably from how it is built.

/Erling

ttan98 · « **Reply #17 on:** 22 Nov 2007, 09:54 pm »

Quote from: scorpion on 22 Nov 2007, 01:52 pm

One or two woofers ? That depends on what speakers you are combining. With B200 I would go for two. In this combo I had to take down bass a bit
to get a balanced response. This bassunit is quite capable and you get a good impact from one basspeaker alone but OB-bass is never like enclosure bass, just
better and more dry. I would wholeheartedly recommend this german High-Tech Hi-fi unit for OB, link above.

/Erling

good response thanks...

ttan98 · « **Reply #18 on:** 7 Dec 2007, 04:34 am »

I send you a message did you receive it...

hope for a response..

scorpion · « **Reply #19 on:** 7 Dec 2007, 11:28 am »

ttan98,

I received it. I can as well answer here.

Measurements is of the right speaker with microphone on 1 m distance at the fullranger axis 85 cm above floor. That's about all.
Measurements are taken in my living room, which is 7.5 m x 4.5 m and 2.30 m to the ceiling, with the ARTA system and Periodic Pink Noise as I wrote above, I have done nothing to try to adjust for some different effects. So the measurements are as they are with many possible weaknesses.

I brought the speakers to a DIY-show in Stockholm last weekend, they made quite an impact I would say !

/Erling