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Thread: RFC News

  1. #121
    Join Date: Aug 2010

    Location: Gloucester, UK

    Posts: 91
    I'm Ben.

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    Paul, that's annoying about the drivers. But, from what you write about the replacements, also serendipitous perhaps. All the best with these latter stages of the project. :-)
    NVA TFS media PC > One4 (Wonfor) Class A power amp > Homemade 3-way speakers
    DC blocker > Sovereign MTBPS balanced power supply.
    TQ (Wonfor) UB cables.

  2. #122
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    Quote Originally Posted by docfoster View Post
    Paul, that's annoying about the drivers. But, from what you write about the replacements, also serendipitous perhaps. All the best with these latter stages of the project. :-)
    It was quite a blow Ben. I went to extreme lengths to get exceptionally accurate measurements for TS parameters including setting up a special rigid open frame for suspending drivers clear of boundaries for Fas measurements and also the construction of a very rigid test box to determine "Vas" (equivalent air volume). Tests were repeated with a number of the drivers and results compared with the manufacturer's claims. The results were quite staggering in just how far out the manufacturer's data was.

    I've been working 12 hours a day on this issue recently, with no let-up as the driver specifications are everything to achieving the response and sound qualities that I'm after. The box size stays where it is for a number of reasons, including aesthetic, for low clean bass and because there are other units that will work with these cabs should the latest ones not work out. It just means tuning bass down if Vas drops providing that the drivers can maintain reasonable SPL levels for the cab volume and tuning point. As you move smaller with cabs, correct matching and tuning becomes more critical to avoid upper bass hump issues, so better going slightly larger on the box size and picking drivers with very low Free Air Resonance properties (ideally below 35Hz). A lot of the performance is determined by total system "Q" or damping factor.

    Low Q drivers typically have more powerful magnets and higher electrical damping so work well in small enclosures where they can deliver a low resonant frequency against a relatively high air compression force and as open baffle drivers. High Q drivers typically require larger cabinets, produce slower less well damped bass and are less able to resist high air compression forces. For good taught bass in my cabs, I need drivers with a Qts of between 0.3 and 0.35 although slightly lower may work providing SPL levels can be maintained. The difficulty arrises where as cab volumes increase, the lower range of this Q value results in an over-damped system producing low bass SPL.

    The latest drivers tick these boxes but need to be measured and tried.

  3. #123
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    Testing resumes tomorrow with the new (improved!) drivers for the Rhapsody. No changes were required for the cabinets, just the tuning and crossovers. Initial review of data suggests superb off-axis response and very low group delay, along with very fast transient response for a ported enclosure. A few tricks are being used to minimise mid-range port leakage to all but inaudible levels.

    I may be trying two types of driver from the same stable. As one is considerably more expensive than the others, and only found in high-end commercial designs, it will be an option for a special edition (Rhapsody "SE" loudspeaker).

  4. #124
    Join Date: Aug 2010

    Location: Gloucester, UK

    Posts: 91
    I'm Ben.

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    Quote Originally Posted by Reffc View Post
    A few tricks are being used to minimise mid-range port leakage to all but inaudible levels.
    A rolled-up old sock...?
    NVA TFS media PC > One4 (Wonfor) Class A power amp > Homemade 3-way speakers
    DC blocker > Sovereign MTBPS balanced power supply.
    TQ (Wonfor) UB cables.

  5. #125
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    Quote Originally Posted by docfoster View Post
    A rolled-up old sock...?


    Not quite Ben

    I take delivery of the drive units today and the cabinet baffles are currently at the CNC machine shop. All bracing now completed and cabinet main panels being sorted out.

    Drive units will be left to temperature stabilise for 24 hours at room temperature before testing (otherwise overly stiff compliance throws measurement results out) so that crossovers can be individually matched. Looks like end of next week for the first pair to be completed.

  6. #126
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    There's been some major website updates and revisions over the past few days. For a look at the better organised products pages, please see the following link. Lots of new goodies added including some VERY tasty turntables!

    http://referencefidelitycomponents.co.uk/products/

  7. #127
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    New!

    I'm delighted to announce that as of TODAY, RFC is able to supply high quality Atacama Nexus and HMS (high mass) speaker stands, in heights from 500mm high to 1000mm high to cater for just about all types of stand mount speaker made today.



    I have been looking for a while for a company who could provide me with stands that are more than just a few tubes thrown together, and Atacama certainly know their stuff. After discussions with their head Marketing Director and having seen their products, I now understand just what goes into these stands in terms of design.

    There are many stands available on the market, so why Atacama? Well, like the small handful of really well engineered speaker stands avaialble today, their design is more than just in fashionable looks. The range that I now promote (Nexus and HMS) are both designed so that they bring genuine improvements to sound clarity achieved through mass loading the High Carbon Steel supports (no cheap allows or mild steel in these...they are extremely stiff and heavy stands) which are shaped to minimise resonance and help to sink speaker vibrations to the floor couling spikes.

    Not all stands do this well. Some actually make matters worse!

    I am also working with Atacama on a bespoke design to be developed specifically for the Reference Rhapsody Loudspeaker. These will be announced following the launch of the Rhapsodys in January 2014.

    To read more, or to buy, please visit my web pages:
    http://referencefidelitycomponents.c...tands-atacama/

    Prices from JUST 74.99 per pair! (that's pretty astonishing value for the quality and performance...they really are a "no-brainer" choice). Shipping anywhere to the UK (only UK I'm afraid) 15

  8. #128
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    Had a major revamp and clean-up of the website today: see what you think of the changes.....RFC Website

  9. #129
    Join Date: Mar 2012

    Location: Gloucestershire

    Posts: 3,950
    I'm Paul.

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    New drivers for Rhapsody speakers







    I'll publish full specifications once I have the speaker's completed and these bedded in properly. All I can say for now is that they are extremely high quality drivers and are optimally matched for my cabinet design. You won't find these in more than a small handful of speakers in the UK which carry serious price-tags.
    Last edited by Reffc; 13-12-2013 at 20:14.

  10. #130
    Join Date: Jan 2013

    Location: Bristol

    Posts: 6,168
    I'm Justin.

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    Quote Originally Posted by Reffc View Post
    Update on Reference Rhapsody Loudspeaker DevelopmentThe crossovers are doing their job well and the resultant system impedance curve is nice and smooth with no nasty amplifier loads, plus phase angles are nice and low...easy amp load. The problem lies in the free air resonance of the original woofers specified, which were twice as high as the manufacturer claimed. At first, it was suspected that test voltages and currents were not sufficient to replicate the claimed response, but these were all checked and the measurement tools certified to be within 1% accuracy. The woofer manufacturer later claimed that specifications had changed over the years and apologised saying that they should update them. Yes, they darned well should. Many people will be out of pocket and will not be getting what they thought they were getting otherwise.

    Luckily I have found out now rather than later by my own testing, and the new replacement units are a very modern take on the ones specified originally (and from a different source), but are bang up to date in terms of materials technology and construction. Of particular appeal is the lightning fast transient response of the new woofers and the fact they'll work well in ported enclosures. I take delivery of those next week and then the poor old crossover board will go under the knife once again! Cabinets will be ready in a few weeks.
    Was this duff drive unit the one you e-mailed about? Just curious - TBH though I didn't say I thought they were out of production but had assumed I was wrong about that as you obviously seemed to think you could get some!

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