Acapella Sphaeron Excalibur and new IB Subwoofer with 4 pcs. Precision Devices PD184

[tiefbassuebertr]

A friend has bought these speakers recently in used condition for very resonable costs. There are several versions of this model. My friend have the version from the pictures of this URLs:
https://web.archive.org/web/20160404212029/http://www.higherfi.com/pix100k/acapella_sphaeron.jpg
https://web.archive.org/web/2015041...10/Acapella-Audio-Arts-Sphaeron-Excalibur.jpg
Unfortunately the space in his listening room for the genuine bass unit, which is located between the satellite speakers, is too small. For this reason he sold the genuine bass unit individually and have make an IB-Subwoofer (see one of the attached images) which works from arround 22 until 70Hz.
I now support him in finding the optimal solution for the adaptation and thus best sonic quality.

The most important question in this case is follow:
Will he need an additional speaker box (for arround 70 until 250 Hz) or not ?

In order to answer this question, actually nearfield frequency measurements are necessary. Maybe one of the members have hifi reviews like stereophile, where are measurements released.
Thank you very much for upload.

Description to the pictures:
1) Subwoofer 4xPD184, each 16 ohms with one additional board for reducing vented area
2) Frequency response of this Subwoofer, nearfield, without crossover network
3) impedance of this subwoofer - blue/white - with/without correction board at vented area
4) impedance of Acapella Sphaeron Excalibur satellite speakers (obviously no integrated high pass function in the integrated crossover network)
5) Frequency response of Acapella Sphaeron Excalibur satellite speaker - only the low-mid horn, nearfield
The showed measurements was performed by DAAS3NT - go to the PDF in post #3 under
https://www.diyaudio.com/forums/mul...-4-plasma-corona-ion-tweeter.html#post6772263

 

[SpeakersinBelgium]

Comments

Some comments:

- Very strange! Is it really nearfield measurement of the subbass ? It should have flat response to the lowest frequencies - above 200Hz a lot of decline... I would not use this cabinet that high in freq.
- low mid-horn looks very strange. Strong resonance at 350Hz and remarkable decline above even within one octave only!! Such a horn should work linear over 4 oct- sometimes it is possible to even reach 5 octaves...

I would measure at first all components individually outside (Freefield)
After that, I would measure the room - what is the reverberation time/frequency ? Etc.

To really get the maximum from this speakers you need more data, that what you presented...

It seems that the whole system needs serious rework and new x-over design.
But for that you need to know the strength and weakness of each individual speaker components.

And/BUT: I would ONLY run such system in an ACTIVE environment - so individual amps/speaker with comprehensive FIR-Filter x-overs and real-time control (Timings between speakers, etc..)

Good luck!

 

[tiefbassuebertr]

In the attachment more measurements of frequency responses (nearfield and listening place).
The first picture (Dynaudio 30W54 without crossover network, white graph without additional trictrax horn) and the third picture (30W54 and Dynaudio midrange soft dome D52, both graphs with crossover network and with used horns) shows clearly the increase between 200 and 700 Hz, caused by the horn in front of the 30W54. The smaller trictrax horn for Dynaudio's D52 don't create such an enhancement at the frequency response (see second graph in the third picture so as the fourth picture).
This means for me clearly the additional use of a damped notch filter as a supplement for the present crossover network.

 

[POOH]

What a mess?? It appears the bass system being used won't keep up at all with the midbass horn, How low does the midbass horn (big spherical horn) go at the listening position?

 

[tiefbassuebertr]

What a mess?? It appears the bass system being used won't keep up at all with the midbass horn.
How low does the midbass horn (big spherical horn) go at the listening position?

The second picture show this. Subwoofer doesn't operate while this measuring.
The blue graph shows the results without the big spherical horn. The bandwidth from this horn is only between approximately 200 and 600 Hz, because this is the enhanced area created by the horn (better to see in picture one).
Next step will be to introduce an additional amplifier with an equalizer like that one under
http://kenrockwell.com/audio/technics/sh-8065.htm for linearisation this rail independend of the other rails (temporary solution). Additional I will enhance the cut-of frequency from the midrange (from 200 to 600Hz) due to too wide overlapping presently.
The tuning/adjusting of the subwoofer ist the most easy and last step.

 

[tiefbassuebertr]

The second picture show this. Subwoofer doesn't operate while this measuring.
The blue graph shows the results without the big spherical horn. The bandwidth from this horn is only between approximately 200 and 600 Hz, because this is the enhanced area created by the horn (better to see in picture one).
Next step will be to introduce an additional amplifier with an equalizer like that one under
Technics SH-8065 33-Band Stereo Graphic Equalizer (1982-1987) for linearisation this rail independend of the other rails (temporary solution). Additional I will enhance the cut-of frequency from the midrange (from 200 to 600Hz) due to too wide overlapping presently.
The tuning/adjusting of the subwoofer ist the most easy and last step.

Now I have tested this, but in a single amp mode, i. e. without extra amp for the rail, where correction is necessary. In use are currently two equalizer models:
1) BSS FCS-960
2) RANE GE-60
Both equalizers provide after correct adjusting a great enhancement in sound quality despite the fact, that also the upper mids and the high frequencies runs about one of the Equalizer.

But the difference in sound charakter between both eq models are also clearly audible: The RANE GE-60 sounds more lovely (earfriendly) while the BSS FCS-960 sounds very clean and tight, but sometimes too hard. In cases, where in the Bass-Mid area an extra amplifier is in use (i. e. upper midrange and high frequencies without EQ) maybe the BSS FCS-969 is the best choice.
Below some pictures of the measuring results.

Next step is the introduce of an extra power amplifier with integrated variable band pass filter (consist of a variable 24db low-pass and high-pass - this unit should replace the Equalizer)) and additional a 24 db variable high-pass for perfect adjusting the cut-off frequency arround 60-150Hz (for operate with the now present IB-subwoofer)

 

[tiefbassuebertr]

After introduce of an extra amplifier for the rail with the equalizer
there was a massive increase of sonic quality in the upper frequency range, because the eualizer isn't longer in the signal pad for that frequency area.

But an integrated amplifier must be chosen, because the voltage gain factor from an typicall power amplifier was too low.
As an interim resp. a transitional solution, I used a PA-1050 from Nordmende with a Rane GE60 before that (see attached images).

Now I want to create a notch filter with voltage gain stage for installation in a power amplifier as a replacement for the RANE "GE-60".
I want to use the power amp model "E41" from KS, Wuppertal - go to the attachments.

Please let me know a good circuit therefore - thank you very much

 

[tiefbassuebertr]

both URL's from post #1 was dead. I have make correction.

 

[tiefbassuebertr]

some images of remove an interrupt at the midrange
The tweeter from first image is this one:
Plasma Speaker Homepage
Acapella Triolon Excalibur Loudspeaker
Ionophone - Corona - ATR - Plasma Tweeters
A Capella/ATR TW-1S
수입오디오-장터 - 아카펠라 프라즈마 이온 트위터
https://www.monoandstereo.com/2014/07/acapella-ion-tw-1s-ionic-tweeter.html
Who can upload a service manual ?