Today we were in the workshop repairing and upgrading customers DSP’s. Coincidently whilst we were upgrading a DSP7200.1HC to a DSP7200.2HC we had a legacy DSP5500HC ( .2 Smiley) on the bench.
We thought it would be interesting to have a look at the two loudspeakers electronics panels side by side, so we took a few shots to show the differences.
Unlike the mechanical speaker layouts the electronics layouts are quite different. The single shot below shows the development of a legacy configuration to the DSP7200 electronics backbone.
The first thing to notice is that the DSP5500HC’s power supply board is a separate chassis mounted board. (the same board configuration as the DSP8000), whilst the DSP7200.2HC combines the power supply function onto the main amplifier board.
The DSP5500HC’s mains transformer is mounted on a separate panel assembly, simply because the DSP5500HC back chassis is sheet and would bend too much with the transformer mounted on a longer chassis.
The ‘Comms’ board in both models are enclosed with what essentially is a tin can providing an enclosed earth plane , the DSP7200.2HC shown below has yet to have the enclosure re-attached.
The ‘Comms’ board of the DSP7200.2HC utilises a differential or balanced output. This means there are nine analogue connections (the wiring loom (red/black at the bottom of the photo below) to the main amplifier board. (Tweeter, Mid and Bass) This benefit of this is reducing susceptibility to any external noise caused by electromagnetic interference.
The power for the board is via a ribbon cable (can be seen under the analogue loom shown above). There is additional on board rectification, a separate rectification IC is added to the chassis under the ‘Comms’ board allowing for heat dissipation.
Please note the DSP7200HC (and DSP7200) upgrade to .2 is no longer available from Meridian, we had utilised a kit we had in stock.
The upgrade kit initially offered by Meridian consisted of a new .2 ‘Comms’ board and an upgraded tweeter (SEAS Model 27 TAFCD/GW-ME H1612 – 04 Ohm, Black Dome).
The comms board change was due to the lower sensitivity of the new tweeter. The sound quality upgrade is significant. Now of course the SE upgrade kit is available.
The ‘Comms’ board change involves resoldering the 9 differential outputs onto the new board shown below.
The DSP7200.2HC power supply and main amplifier board is a single board with the power devices running along the side of the board bolted to the cast chassis for heat dissipation.
There are four identical amplifiers, one for each driver. The balanced feed for the bass drivers being linked on the board (separate high impedance link).
The DSP5500HC on the other hand utilises 2 identical amplifier boards each having two channels. The DSP5500 series chassis being a development of the original DSP6000 chassis.
The alternate configuration of the DSP7200.2HC chassis allows simplification of the loudspeaker driver wiring looms. (DSP5500HC taking separate bass feeds and a combined mid/tweeter).
Interestingly the front eight character dot matrix display boards are the same in each speaker. This design remains unchanged to this day, which did mean we were able to take this rather strange shot.
There is a generic evolution from the DSP5500HC to the DSP7200HC.2.The loudspeaker internal working volumes are essentially the same and both designs use the classic d'Appolito configuration. This configuration is ideal for horizontal centre speaker applications.
The DSP5500HC tweeter is the SEAS H539 and is mounted as part of the mid range enclosure. This tweeter is used on the 6000, 5500, 5500HC and 7000 legacy products.
The two SEAS CA 21 chassis bass drivers are individually reflex ported in a nominal 20 litre enclosure each, the DSP5500 floorstanders use both drivers in a single reflex ported enclosure, as reported elsewhere bass is very lively in that design, although tamed a little with the 2011 DSP upgrade software roll out.
In the DSP5500HC, the SEAS P17 mid range driver sits in a separate sealed box enclosure, nominal 11.5 litres. Above is the P17 chassis and the T17 chassis. The later was only used in the DSP8000 legacy (and SL legacy).
The T17 chassis translucence is the result of Meridian’s usage of TPX™ polypropylene which possesses the lowest density among thermoplastic polymers, thereby providing a lightweight cone material enabling a further performance increase. This cone material is used in the current range of .2 and SE mid range drivers.
The DSP5500HC utilises the same bass specification drivers (Thiele/Small parameters) as the DSP7200HC (there is a chassis difference), however the later uses the mid range from the DSP8000.2 and a the .2 tweeter).
DSP5500HC the star of the legacy range
The DSP5500HC (along with the magnificent DSP6000.2) is the ’star’ of the legacy range and still represents significant value for money.
Apart from EBA capability of the DSP7200.2HC the sound quality of the two loudspeakers is very similar, the DSP5500HC retaining the classic ‘Meridian Legacy polite sound’ whilst the DSP7200.2HC enabling a more detailed view of the soundstage.
The DSP6000 will be discussed in ‘Meridian Evolution’ coming soon.
The views and facts presented here have been collated by observation of Meridian products and publicly available information. No reverse engineering in any form has been undertaken.