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Thread: Lockwoods in da house! - advice please

  1. #151
    Join Date: Sep 2014

    Location: Northern Ireland

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    I'm John.

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    Morning all. Only got a quick listen last night but definitely a more bass focused presentation with the ports in place. Of course this seems at the expense of some midrange magic but that's probably expected as the mids aren't as well pronounced now things are more balanced. I think the soundstage is even deeper and more specific in placement which is good but overall the sound is not as engaging as before with the crossovers pushed into the box, but it's early doors. Possibly a slight lack of snap on leading edges and transients. The box isn't singing with the extra bass at all, they're very solid and inert.

    There are two options if I decide to go for new cabs, bigger standmounts around the 130L mark or full on floorstanders 170L or so. It's a small upstairs room though with a suspended floor and I am concerned about boom. My stands are slightly oversized in footprint so could take a bigger box comfortably and the height could be reduced by cutting the legs a bit.

    Not rushing into anything yet. Any ideas on cost to get half decent cabinets made?

    Oh, Ken, from the "measured" data for the 385 on the hilberink site effective driver diameter is 32cm.

    Edit - I'd like to try these with a good SS amp before making any further decisions. I'll have to see if I can annoy someone
    Last edited by JohnJo; 16-04-2017 at 08:36.

  2. #152
    Join Date: Feb 2013

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    I'm Grant.

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    Excellent advice Ken ... agree room size might give issues potentially, yet Marco,s room is pretty small and his speakers are humongous
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  3. #153
    Join Date: Jan 2013

    Location: Carlisle - UK

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    I'm Ken.

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    I believe the Arden was 175 L, check out its specs (HPD version), for what to expect performance wise.

    Spot the easy mistake I made in calculating the ports anyone?
    I used diameter and not radius in the Pi Rsq calculation.
    Well it was early and I was half asleep.

    A diameter one third of the 32cm piston diameter = 89.3cm sq min area.
    Your pair of small twin ports = 19.2cm sq total

    Still a long way from ideal.

    I can't help on cabinet costs as I always build my own.

    You seem to know what your doing and what your goals are, keep us posted with your progress.

  4. #154
    Join Date: Mar 2017

    Location: Seaford UK

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    I'm Dennis.

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    From Colloms' book "High Performance Loudspeakers", he says that in a well designed system there should be no need for damping the fundamental resonance used for bass O/P reinforcement, but that there is of course a need for it to reduce/eliminate the mid range rear energy from the cone, and which may come out of the port, (which sounds awful even on many professional monitors).

    The accepted correction for room reinforcement of bass, is approximately a sigma curve from about 80 Hz sloping down to a figure of -7dB at 20 Hz.

    This is the hardest thing to get right IMO because of the real possibility of changing rooms, and having to make new boxes and alignments.

    Addendum.
    I think I can remember his exact sentence;
    "In a well designed system, there should be no need for box filling at fundamental resonance,, but there is of course a need for filling to absorb the mid range energy".

    Filling can increase the effective internal volume by up to 40%, (depending on whose figures you validate), and filling the volume is of course useful in lowering the O/P at fundamental resonance to adjust it to suit, but it should not be allowed to move about under drive.
    Last edited by Pharos; 16-04-2017 at 10:21. Reason: Addendum

  5. #155
    Join Date: Sep 2014

    Location: Northern Ireland

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    I'm John.

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    Thanks guys for all the feedback. I shall chew the cud, digest and report back in due course

  6. #156
    Join Date: Sep 2014

    Location: Northern Ireland

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    I'm John.

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    Bit of thread resurrection here

    Borrowed a signal generator and used it to test my system tonight and the results were most interesting.

    I was primarily interested in the bass response of my speakers. (A quick summary so you don't have to read the last 16 pages is that they are Lockwood Academy fitted with 15" Tannoy 385 HPD drivers in a sealed box which is probably much too small to do the Tannoys justice in the bottom end with an internal volume of just 68 litres). I should say I have eased open the crossover panels on the back of the speakers to let them breathe, so no longer sealed cabs really.

    By ear at the speaker front, bass response was pretty flat to 43Hz then rolled off gently to about 40Hz from where they fell off a cliff to be all but inaudible by 30Hz.

    Better than I expected to be honest but I suppose not fantastic given that an open E string on a bass guitar is 41Hz, I think.

    Having said that, maybe it's my hearing that's rolling off sharply below 40Hz.

    I have often toyed with building new larger cabinets for the drivers to improve bass performance but looking at this predicted response in a 200L cab from the 44BX site I'm not so sure it's worth doing as I don't seem to be losing that much, maybe 5 or 6 Hz before roll off.

    Last edited by JohnJo; 19-09-2018 at 21:24.

  7. #157
    Join Date: Sep 2014

    Location: Northern Ireland

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    I'm John.

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    Took a set of measurements with an app on my phone from the listening chair, obviously a lot of variables here but gives an idea of in room response.

    Note: This is not a measured 1w@1m thing, it's just a certain position of the volume control.

    Notice the suck-out at 55Hz. I take it that's a room mode?

    Edit: Horizontal axis is frequency in Hz, vertical axis is db reading using phone app.

    Last edited by JohnJo; 20-09-2018 at 08:29.

  8. #158
    Join Date: Sep 2014

    Location: Northern Ireland

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    Interestingly, the drivers were still outputting at 100KHz according to the phone app, I gave up and didn't try anything higher.

    Sounded like the drivers were crossing over a smidgeon below 1KHz, does anyone know if this is correct for HPD 385s, seems very low?

  9. #159
    Join Date: Mar 2010

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    Your phone microphone won't reach 20kHz nevermind 100kHz, most studio mics don't even reach 25khz
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  10. #160
    Join Date: Aug 2009

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    I'm Martin.

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    Quote Originally Posted by JohnJo View Post
    Interestingly, the drivers were still outputting at 100KHz according to the phone app, I gave up and didn't try anything higher.

    Sounded like the drivers were crossing over a smidgeon below 1KHz, does anyone know if this is correct for HPD 385s, seems very low?
    That sounds about right. But there's no way they are doing anything at 100Khz!
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