In Development: Hestia V-Dome

tonytopshed · « **Reply #20 on:** 24 Dec 2014, 01:10 pm »

Christmas greetings everyone!

Here are my efforts so far. Vifa XT19 with 1.5 uF in series; Seas FU10 with 30 uF in series and an L_Pad. Both driven from an Arcam A38 amp.
10" FaitalPro and Seas 8" (in H-frame) U22REX H1659-08 wired together in parallel, driven from a miniDSP and Myryad amp.

I don't know if all this makes acoustical sense? - I am pleased with the sound so far; cellos and the lower piano notes have a good vibrancy and the elephant in Saint-Saens' Carnival of the animals is definitely in the living room!

I'll relax and listen to music as opposed to 'sounds' over Christmas and then try to develop it further...

Any suggestions as to where to go next gratefully received - I still feel I'm groping in the darkness!

matevana · « **Reply #21 on:** 24 Dec 2014, 03:10 pm »

Hey Tony,

Looks very nice! Congrats.

I'm intrigued by your description and have a few questions at your leisure. Did you mean that both the Faital and Seas drivers are wired together and driven by the same amp through the MiniDSP? If so, can you go into a little more detail on this. Are they wired in left/right pairs or mono? Do you remember the MiniDSP settings for slope and crossover point? It sounds like in your version both the 8" and 10" drivers are crossed the same, so you essentially have a 3-way instead of a 4-way... or maybe I misunderstood.

tonytopshed · « **Reply #22 on:** 24 Dec 2014, 05:25 pm »

Quote

Did you mean that both the Faital and Seas drivers are wired together and driven by the same amp through the MiniDSP?

Yes, I had tried an 8 mH inductor with the Faital, but didn't seem right and I wasn't sure what to do next. Then when I got the Myryad locally at a sensible(ish) price and the MiniDSP from Ebay. I reckoned that the DSP had plenty of adjustments which might deal with all the bass end in one go.So it is, as you say, a three way system.

Quote

Do you remember the MiniDSP settings for slope and crossover point?

After Christmas I'll give you details, if you don't maind waiting a few days. I'm still fiddling around with settings, once I get a longer USB extension it will be easier - from a comfy seat, not crouched on the floor behind the speakers!

I'll also save a graph from REW for you to comment on. Am I right to place the mic 6 to 8 ft in front of the speakers (the region where I sit) and point it upwards?

matevana · « **Reply #23 on:** 24 Dec 2014, 07:48 pm »

Sounds good and take your time Tony! Always interested to hear someone else's approach. The great thing about speaker design is there are often many ways to accomplish the end-goal. Happy listening!

Juhazi · « **Reply #24 on:** 31 Dec 2014, 10:48 pm »

Tony, you are not getting all the potential out of bass drivers if tehy are coupled like that. They definitely should have separate dsp channels. Which model is your minidsp? If something must be passive let it be mid to tweeter xo. Delay settings are also quite important . Typically we need one 2x4 for each speaker or a 4x10HD which handles both L/R. Lots of amplifiers too!

Here is good info about using minidsp for multiway dipoles http://www.hifizine.com/2011/03/refining-a-4-way-open-baffle-speaker-minidsp-2x4/
And you should read this too http://www.hifizine.com/2010/12/prototyping-4-way-open-baffle-speaker-with-the-minidsp-2x4/

A measurement system based on FFT is needed. REW is free and simple http://www.roomeqwizard.com/
Minidsp UMIK-1 is nice http://www.minidsp.com/products/acoustic-measurement/umik-1

DSP is extremely flexible and potent tool for Obs. Look at http://www.linkwitzlab.com/What_is_new_at_linkwitzlab.htm and NaO NoteII RS http://www.musicanddesign.com/NaO_Note_II_RS.html

tonytopshed · « **Reply #25 on:** 6 Jan 2015, 09:18 pm »

Hi folks

Quote

you are not getting all the potential out of bass drivers if tehy are coupled like that

Yes, I'm aware it's not the best method but I'm limited to what resources I have withoit spending a fortune! I'm aiming to boost the bass response as much as I can. Perhaps it would make more sense if both bass woofers were the same? I don't want to widen the baffle too much with 15" drivers. And with only a few inductors and caps to play with the minidsp gives me plenty of flexibility.

I have the miniDSP 2x4 and settings are -

These are the settings - at the moment! - the minidsp input is from my ARCAM a38 pre-out and its output goes into a Myryad amp.

Do different amps create any timing or other difficulties?

So, the 10" FaitalPro and Seas 8" (in H-frame) U22REX H1659-08 wired together in parallel, The Faital seems to be the louder.
Seas FU10RB now has a 270mH inductor in series as well as the 30uF Cap. Yesterday I mounted this driver behind the baffle - 20mm - rather than halfway which seems to have taken the shrillness from it. Because of this I've taken out the L-Pad.
I have replaced the Vifa tweeter with my Fountek Neo CD3.0 (from an IPL TL kit) which I think is better (or is it? Not a great deal of difference). It's mounted behind the baffle (12mm) as I don't want to carve out the hole at this stage. 1.5uF cap and 5R6 both in series.

With the speakers about 3' 6" from the wall behind them, 6' 6" apart and a mic 10' in front I get this graph -

What are your comments arising from the graph?

All this probably sounds crazy to you experts! However, I have got a system which, even at this stage, is way better than anything I've had before, and friends have been impressed.

So what next?

Thanks Juhazi for the links - I have looked at - but not 'studied' them! There is a lifetime's reading out there!

matevana · « **Reply #26 on:** 9 Jan 2015, 01:06 pm »

Hey Tony,

Here's a quick experiment you can try. Take the Seas 8" driver out of the loop and conduct the same test. I'm not sure the driver is adding anything in this setting and the amp may have better control over the Faital's VC without it. If that improves the sound, the next step would be to add back the H frame, but this time under the separate control of a plate amp/crossover when you can afford to do so.

tonytopshed · « **Reply #27 on:** 12 Jan 2015, 10:36 pm »

Hi,

I've two graphs here, the black line is with all 4 drivers.

This first one I have taken out only the Seas 8"

In this second graph I have taken out only the 10" faitalPro.

I've made a change since my last post - The Arcam amp has a button to seperate the pre-amp from the speaker amp part (is there a name for this?), so I've taken the other two outputs from the MiniDSP for the mid and tweeter. Like the bass, I'm feeding the mid and tweeter together with the crossover I gave in an earlier post.

No doubt a 2x8 MiniDSP would be better (with more amplifiers!), I'm trying to make the best use of the resources I have at present.

I haven't yet listened to music without one of these bass units - I'd better do that next and get some idea of what contribution they make on my ears

Anyway, it's a good improvement!

matevana · « **Reply #28 on:** 13 Jan 2015, 01:59 pm »

Kind of what I suspected in this case. The Seas driver is just mimicking the more efficient Failtal Pro driver and if anything contributing to a curve that is less flat, and probably some audible doubling in the lower frequencies. If you relegate the H-Frame to a low-pass of no more than 90-100Hz you will reduce some of that low register smearing and clean up the funk. This will also help to fill-in the lowest register which is somewhat lacking presently.

JohnCZ · « **Reply #29 on:** 29 Apr 2015, 05:19 pm »

Hey Ed (Matevana),
Assembled my drivers for the Hestia V Dome and I'm about to order my flats for the project. I have some large enough scraps of 3/4 Birch ply and want to experiment with my current open baffle driver (for a second system later). Currently I'm using the Tang Band 1808 driver with the Alpha 15 and it sounds great. Interested in the Hestia because I would like a larger sound presentation. And if the Hestia has anything close to the presentation of the Linkwitz project and only require 1-2 amps, I would be very happy.

I would hate to just box up my 1808 drivers. Could it be substituted for the Seas midrange with the Eminance and tweeter? In a previous topic you suggest that I use a conventional L-pad with 2 resistors on the Eminance. That is in addition to the 9.0 inductor, correct?
John

matevana · « **Reply #30 on:** 29 Apr 2015, 07:19 pm »

Hey John,

Remind me what you are proposing for each of the drivers and whether you plan to use one or two amps?

JohnCZ · « **Reply #31 on:** 29 Apr 2015, 07:40 pm »

Ed.
Building the Hestia V Dome. I have the Seas, Lil Buddy and the Vifa tweeter. Also, using the Alpha 15 for the bottom. I have a cap and 4.7 inductor on the Alpha.
As an experimental second system I thought I would reuse the Tang Band 1808 instead of the Seas midrange. At the moment I am using just one amp driving the Tang Band and Alpha. In the future I plan to use plate amps to drive just the Alpha 15s or an upgraded version.
The Tang Band 1808 is about 94db and has a very nice midrange. In its present application I have no filtration on the driver - using it full range.
I also plan to use all of the filter values you recommended for each of the drivers.
John

matevana · « **Reply #32 on:** 29 Apr 2015, 07:58 pm »

You could but I suspect the presentation will be very different. The crossover will take some work as the 1808 is more efficient than the Seas midrange, and will likely produce more overlap than the Seas as well. This will result in a more forward presentation. Still though, it can be done with a little trial and error, or the right modeling tools.

tonytopshed · « **Reply #33 on:** 9 May 2015, 09:23 pm »

Hi Matevana,

I've left the bass units in abeyance at present and decided to put in the Jordan Eikona 2. Wow! What a difference! Instead of asking myself "what can I do next to try and make the sound better?" I now am asking "Is there anything I can do to make it better?" I left room for a tweeter, but I'm very doubtful if it is needed - maybe my elderly ears of course! Sometimes speech sounds as if it needs sharpened up, but again my ears? I do have some loss around 4000 hz and up.

About the bass units, supposing I put two the same each side, such as 10" Seas similar to that which Linkwitz has used in a W-frame, connected in series, would that make sense? I'm thinking of a two way system using a MiniDSP and limiting size to 10" for space reasons. Perhaps the SEASL26 R04Y D1004. Fs 24, sens 85.5, Qts 0.27, power rms 250?

At present I have the low pass at 250 LR48/octave, high pass at 50 LR48/octave with a little equalisation top and bottom. What I'm getting sounds pretty good, the SPL does show a falling off at the high end.

I'm waiting for a couple of pairs of ears to listen, ears that have had experience in broadcasting and hi-fi business.

Are you any further on with your project?

matevana · « **Reply #34 on:** 10 May 2015, 12:29 am »

I've heard the Ted Jordan original metal cone driver. It can sound nice. I'm sure the later stuff is even better. Can you remind me what your current configuration is? (drivers). If you are using a full range driver, you should not have significant loss at 4k. Most are pretty prevalent in that range and start to peter out 12-14k.

tonytopshed · « **Reply #35 on:** 10 May 2015, 09:05 am »

10" FaitalPro and Seas 8" (in H-frame) U22REX H1659-08 wired together in parallel, driven from a miniDSP and Myryad amp. Jordan Eikona 2 driven from Arcam A38, using the other 2 channels on the MiniDSP.

This was with the crossover at 100; I should have remembered before posting that I've altered the settings since! I'll set up the mic again when I've time.
(Why is there always less time to do anything in retirement?)

JohnCZ · « **Reply #36 on:** 19 May 2015, 02:17 am »

In the process of starting my Hestia build. One question about the bass unit.
Have the Alpha 15 and the Delta 15a. (Will use one or the other)
Would like to build a bass bin enclosure. Is there a golden ratio regarding the size of the enclosure?
John

matevana · « **Reply #37 on:** 24 May 2015, 10:14 pm »

Quote from: JohnCZ on 19 May 2015, 02:17 am

In the process of starting my Hestia build. One question about the bass unit.
Have the Alpha 15 and the Delta 15a. (Will use one or the other)
Would like to build a bass bin enclosure. Is there a golden ratio regarding the size of the enclosure?
John

To my knowledge the golden ratio referred to in box construction is designed to tame standing waves within a sealed or ported enclosure. While standing waves can exist in both U and H frames, the effect is minimal by comparison, so other design parameters often take priority. You might want to take a look at Martin King's paper on comparing U and H frames; in it he discusses the effect of both frame width and length. His paper is located here: http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf

JohnCZ · « **Reply #38 on:** 4 Jun 2015, 07:28 pm »

They are complete and I like them very much. I am going to be experimenting with an active crossover (bottom section only) over the holiday break. The passive crossover used with the Peerless SLS drivers sounds nice but is limiting the gain to the Adcom GFA-565 amplifier that drives them. I plan use a DBX 223xs crossover which will provide proper gain to the Adcom and offer a 24dB/oct rolloff. That being said I would not want to change the top section at all. In fact, I often run them w/o the Peerless and they sound very nice. I will post my observations over the break.

Hi Ed,
Decided to go with the Peerless 830688 drivers. Are you using a second order passive filter or did you implement the DSP? Found the post above but could not find any other information. Thanks,
John

matevana · « **Reply #39 on:** 4 Jun 2015, 09:56 pm »

Hey John,

I'm using the DBX 223 on the bottom section only. It's a good quality analog electronic x/o. Since I run passive preamps, I experience a level problem with most digital x/o's like the MiniDSP. The DBX unit has more than enough gain to drive my Adcom power amp to the proper level. They are also silent.

The DBX 223 has a fixed 24dB/oct slope which is a bit steep for many OB designs. To get around this, I run the bottom end in mono and parallel the input. The left channel is then set to overshoot the intended crossover frequency while the right channel undercuts it by the same amount. Not perfect but this tends to simulate a more shallow slope (something closer to a 12dB order) and sounds very nice.

The only other changes I have made involve removing the whizzer cone from the Eminence mid-bass unit and replacing it with a standard dust cap and then tweaking the midrange frequency in the x/o.

I am extremely happy w/both the Hestia V (AMTPro) and Hestia V Dome (Vifa x19). I listen to both daily and have no desire to change anything.