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TOPIC: Re: 4 Way speaker project Quarter wave & Horn loading

4 Way speaker project Quarter wave & Horn loading 6 years 4 months ago #9008

  • crackie
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Hello all,
The goal of the project was to improve on the sound quality of the Duntech Marquis speakers I used at home. The plan was to build an active DEQX based system using the Impulse H2 speaker as the inspiration. When searching for bass drivers I found Troels Gravesen's site; Troels' 4 way DTQWT design uses the same quarter wave loading as the H2 but with two Voight pipes. www.troelsgravesen.dk/JA8008_DTQWT.htm
The DEQ used IIR but expensive and only 3 way so after reading Paul Spencer's great miniDSP / DEQX / Ultradrive test articles a 4x10 Hd was the way to go.

Holmimpulse software was used to optimise driver positions and final time alignment but I used ARTA for most of the test measurements. UMIK-1 wasn't available when I started so an ECM8000 did the measuring via a TASCAM US122 mkii interface.

I'm delighted with the performance of the 4x10 Hd using both the analogue and digital inputs; I used 2 or 3 different test discs with 0dbs to set up the gain structure to try and optimise S/N ratio and the noise floor is very low even with 95dB drivers.

The system uses a Wadia 301 ( 1.9Vout at 0dBfs ) to feed the 4x10 analogue inputs. A Musical Fidelity USB to SPDIF converter feeds the miniDSP digital via Toslink. The 4x10's outputs are fed to 4 Rotel power amps.

Bass section up to 60Hz = 2 x Celestion BL12-200X 12" drivers wired in parallel, loaded by a 2.2m long quarter wave pipe, driven by a Rotel RB-981 power amp. Single driver is 94dB 1W/1m
Bass mid section 60Hz to 650Hz = SEAS CA21-REX loaded by a 2.2m long quarter wave pipe, driven by a Rotel RB-981 power amp. Driver is 91dB 1W/1m.
Mid section 650Hz to 3250Hz = Audax HM130Z0 Aerogel loaded by spherical waveguide and driven by a Rotel RB-981 power amp.
High section 3250Hz upwards = Monacor DT-300 tweeter with waveguide driven by a Rotel RB-971 power amp.

Note the system and tweeter measurements were made before I bought a mic calibrator to set up ARTA so the absolute dB scale is nonsense. I included the measurements to show in room response at 3m inc 'House Curve' applied via the miniDSP plugin. The +/- 0.7dB for the tweeter is there to show miniDSP correction is capable of, very little smoothing applied too; 24th Octave.













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Re: 4 Way speaker project Quarter wave & Horn loading 6 years 4 months ago #9043

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Nice! Some fine system with some very good measurements to back it up. We can't hear it very well from Hong Kong (maybe try to crank it up a bit more?;-) but I'm sure that it's sounding very good looking at your build.

Thanks again for sharing with us and glad that you're having a good time with this nice 4way configuration!

DevTeam
MiniDSP, building a DIY DSP community one board at a time.
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Re: 4 Way speaker project Quarter wave & Horn loading 6 years 4 months ago #9050

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Hi Devteam,
I read my original post again and realised I didn't thank MiniDSP; I'd like to say a big thank you to the whole team for the 4x10Hd. Fantastic product.

Mid Horn


Cab section drawing


Cabinet made from 19mm ply faced with 9mm solid Oak.


'High efficiency' project is underway using Pro rather than Hi-Fi drivers ....105dB/1W/1m is the target :whistle: ....... each channel will use 2x Precision Devices PD2150 woofers in 150L sealed enclosures for bass up to 300Hz, Mid will be 2x Ciare 6-1.5 midranges NDK on an open baffle D'Appolito with single Beyma CP21F or Beyma SCM8060 for HF.

Thanks again Devteam,
Dave.
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Re: 4 Way speaker project Quarter wave & Horn loading 4 years 11 months ago #16070

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Great looking project! It has been a while since your last post. Care to update us with new pics and changes you've made?
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Re: 4 Way speaker project Quarter wave & Horn loading 4 years 9 months ago #16943

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Hi Champster, thanks for your feedback.

I've not made many changes since the last post...........I'm now using a pair of bridged Rotel RB-971 power amps to drive the Audax mids. The spare Rotel RB-981 is going to be used to drive some new subs I'm working on.

The first sub uses a 12" Peerless 830845 XXLS in a 225L reflex cab tuned to 17Hz. 1.0Pi adjusted winISD sims predict 115dB at 20Hz and -3dB at 15Hz. The second sub will be a 5.8m long folded tapped horn using two of the same Peerless drivers in parallel. Hornresponse sims predict 1dB or so more extension than the reflex but the TH will be much more efficient. The tapped horn won't be made until I move into a new house next summer. The whole system will be moved to a bigger, acoustically flattering room; the length/width ratio is Fibonacci and the height is close.

Hope to have the reflex sub in and working by the end of Jan; will post some more pics when it is in.
Last Edit: 4 years 9 months ago by crackie. Reason: additional content
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