advertisement


Aftermarket crossover for Naim speakers (DBLs)

Bub,

I have a fundamental problem with housing microphonic electronics in a loudspeaker enclosure, no matter how elegant that may seem. If you think your ATCs sound fantastic now, just think how much better they would be if the amps were 'outboarded', so to speak. You are a surgeon, yes?

James
 
"I'm sure you are right, well, I'm not actually, but I'll take your word for it. The ATC amplifiers were described by a friend as "agricultural"."

Agricultural is good.

Mr Tibbs

Country boy :)
 
While the Amps are not the last word, they don't need to be because they operate in an active environment where each amp operates well within the parameters of what it is feeding... Same goes to the active x/o. I'm in no doubt they can be improved upon but the point is they don't need to be.

The procedure for removing the amp packs is very simple and ATC will sell you a mounting kit to put each amp into a 4U rackspace. I've tried it from time to time with my own (even more agricultural) ATC100s and there's very little difference that I can tell. I'll go further. There's no difference.

I somehow suspect ATC have already thought of Microphony when they released not only the Active ATC100s but later incarnations also and still kept the amp packs internal. They seem to have thought of everything else which is why these speakers sound so much better than everything else I have heard in 20 years of dicking about with "HiFi".....

Also, lots of other brands of pro studio monitors have internally mounted amp packs where this seems to be the norm. I somehow suspect the advantages outweigh the disadvantages and ATC has weighed up the pros and cons. They are a very thorough company and they have no time for HiFi nonsense of the kind often seen on these forums...

Fox
 
"While the Amps are not the last word, they don't need to be because they operate in an active environment where each amp operates well within the parameters of what it is feeding..."

I'd agree.

"Same goes to the active x/o."

Hmm... The active XO is going to be just as critical to outright performance as the pre-amp IMO.

"I'm in no doubt they can be improved upon but the point is they don't need to be."

I must get to hear these things some day :)

Mr Tibbs
 
You have a standing invite, get on a boat or a plane and prepare to be utterly, completely & comprehensively blown away. In a nice way, of course.

As fox says, they are the best, and make everything else seem like a child's toy. They will play anything you like, and seem to take on a new character with every disc.

Then we can go for some beers.
 
"You have a standing invite, get on a boat or a plane and prepare to be utterly, completely & comprehensively blown away. In a nice way, of course."

You are too kind Bub, especially the bit about the beer.

One a these days....

Mr Tibbs
 
Mr Tibbs,

Once you have taken up Bub's offer, you'll have to reciprocate. Unless, of course, you feel thereafter that the E-IIIs might be disgraced in comparison. Then, you'll have little choice but to consider the E-Vs.

James :D
 
"Once you have taken up Bub's offer, you'll have to reciprocate. Unless, of course, you feel thereafter that the E-IIIs might be disgraced in comparison. Then, you'll have little choice but to consider the E-Vs."

Goes without saying Bub's welcome this side. If they disgrace the E-III's then they are... not of this earth...

Thought's of the V's are giving me that itchy feeling ...

Then I hear the music I already have :)

Mr Tibbs
 
"Then I hear the music I already have "

I know what you mean, Tibbsy. But the E-IVs do show the E-IIIs up in one little but important area. That, I'm afraid, is an area that needs redress. Tell me how you feel after Quincy has built his E-IVs.

James
 
James

The IVs may have to take a back seat for a while while I get on with pleasing Yvette with bespoke furniture.

But if they look like this baby then musical appreciation will be relegated to second place.

quincy
 
Quincy,

Congratulations, I don't think I've ever seen more skilled use of Fablon. Scumble Johnston would be proud.

"Tell me how you feel after Quincy has built his E-IVs."

James,

I fear the reaper will have paid a visit to Funkytown before then :eek:

Mr Tibbs
;)
 
"I fear the reaper will have paid a visit to Funkytown before then"

... and to think I developed the E-IVs especially for Quincy.

<sigh!>

Never one to miss an opportunity, here is your chance to build another pair of loudspeakers, but this time for profit. ;)

James
 
Almost a year ago I started this thread after having great success optimizing a design and component selection for crossovers for the DBL. We were all pretty much in agreement that the midrange and tweeter are at best mid-grade units. But with these crossovers and finally introducing a balanced power isolation transformer (10 kVA worth) they took on a greatly enhanced degree of purity and extension that pushed back my inclination to muck around with the drivers.

Months ago I had some custom built 5.25 inch drivers made at circa $200 USD a piece as their 6.5 inch bretheren are amongst the most neutral and transient preserving drivers I have heard. These were custom designed by the very guy who initially designed my crossover and were the product of over 5 years R&D and many, many iterations before they actually met the specifications he provided.

So yesterday I took my DBL upper enclosures over chez Daryl to see how they would respond to replacing their midrange units and what revisions of the crossover would be required.

First off...the driver was too tight of a squeeze to drop directly into the DBL cutout...which had to be filed ever so slightly to allow insertion. Secondly the screw holes were maybe 1 mm different in location from the stock drivers, to the holes of the replacement drivers had to be elongated via a slender file-more work.

Once the new driver was inserted a frequency SPL sweep was done. Oddly enough there was a huge suckout (17 dB) at 1.2 kHz that no amount of crossover modelling would adequately correct. As this driver is about as linear as could be, this deviation HAD to be cabinet related. The stock driver had an in-cabinet response that was rather more linear and certainly had no such suckout.

So the stockdriver was then mounted to a flat surface and a free air SPL frequency sweep done. This sucker has a 22 dB resonant peak at the very 1.2 kHz. However the way it is mounted in the cabinet is on a compliant baffle that has rubber sealed slits around it which primarily serves as a mechanical notch filter rather than to mechanically decouple it from cabinet vibrations as claimed. Which means the ONLY way to replace this driver would to be to find one that has a huge peak at the same 1k zone-which excludes about any other 5.25 inch driver extant. I briefly contemplated sawing out the baffle containing this complaint mount and replacing it with a glued-in fixed board that would then allow any driver to be mated to the DBL, with a very good idea that this would allow the benefits of a superior driver to be quite evident. Sanity prevailed and I returned the enclosure back to its rightful place top portion of the DBL frame. My monkeying with the crossover and internal wiring is about as far as I am willing to go.

I can only speculate what the result would have been if Naim had decided to use a higher quality, more linear and costlier midrange driver mounted in a more conventional fashion. Intuition says that having a compliant mount would only cause loss of detail and diminished transient reponse.

And here are the sweeps....

Stock midrange driver SPL sweeps. Free air = purple; in cabinet = green
The upper sweep shows the free air response (purple) and in-cabinet reponse (green). Note the free air response has a very large resonant spike centered at 1.2 k with shoulders to 800 Hz and 1.7 kHz.

The green in-cabinet sweep has no indication of any residual peak, as resonance (and musical information) in that region has been sucked out. The efficiency of the lower midrange is circa 5 dB higher than that of the upper midrange as previously noted.

SPL sweeps of aftermarket midrange driver in cabinet (red) vs stock driver free air (purple).
The lower (red) sweep shows the in-cabinet response of the aftermarket midrange driver with a 17dB suckout at the 1.2 k derived from the compliant mounting. This is compared with the free air reponse of the stock driver showing the peak in precisely the same place as the cabinet-derived suckout of the former.

Oh well....it was worth a try.

Having said that, the DBLs are sounding great as I type...but still I wonder. And wonder.
 
Ron,

I think the logical conclusion to your loudspeaker adventure is to build a new pair from the ground up. I'm sure Daryl can easily reuse the ATC 15-inch bass driver and partner it with your new mid and a much better tweeter than the Naim-modified Scan-speak unit. I'm betting it's only a matter of time ...

James
 
IIRC, ATC electrically compensates, in the crossover network (active or passive), for a known acoustic response peak in the midrange dome, such that, when used with non-ATC crossovers lacking that compensation network, the driver tends to scream out at that peak.

Perhaps, Ron, you've simply discovered an anomaly that most loudspeaker driver manufacturers have known for years (!), and, that the design of the DBLs you have implements this compensation in a (arguably) different manner than most.

A more revealing measurement, BTW, would be the electrical impedance of Naim's midrange driver wrt frequency, in both free space and in its intended enclosure. Perhaps they're on to something....
 
I don't mean to come across as derogatory to the DBL speakers....I have used them for circa 10 years in many, many different guises. I have found through considerable experimentation that the passive crossover has-shall we say-room for improvement. The cabinet/driver combo has some idiosyncratic and almost unique approaches to design and is capable of far, far better results than allowed by the conventional PXO. It was only after I had a passive crossover tuned to the in-cabinet driver responses that I was even remotely happy with the capabilities of passively driven DBLs. If you go back to my first few postings of this very thread, you can see how much I have began to enjoying experience of passively amped DBLs.

As readers of the 'other' forum may know, I had an Equitech balanced power transformer installed almost 4 weeks ago. This has literally revolutionized the ability of my equipment to perform at the design envelope-but not immediately. The first few days after installation were a sonic mess in terms of the rythmic abilities. The subesquent couple of weeks added attributes such as extension, purity and soundstaging, yet the ability of notes of different frequencies to keep up with each other was still less than the standard required to begin to be able to suspend disbelief and to stop having to mentally compensate for hot and coldspots in the scale.

In the last week I had been unable to listen to music due to recent upper respiratory illness that resulted in a temporary low pass filter being applied to my labyrinths, making any music I listened to sound dull, slow and pedantic. I also was down for 4 days while experiments were being conducted on one of my upper DBL enclosures.

And today for some reason, very close to 4 weeks after the transformer was installed, a sharp corner was turned. This morning I found myself captivated both emotionally and sonically by of all things a Klezmer band. I then had to leave the house most of the day, only to return some 11 hours later and play some more music. And what I have hearing tonight has not but gently hinted at in the near past. Even with the preconceptions I had incorporated regarding the core design of the DBLs, I was embraced by a sound that was as nimble and agile as any I have heard. Plucked notes on a double bass now are more like a ball being bounced rather than slowly rolled. And as hard as I try I cannot hear discontinuities in the spectral balance or frequency dependant dynamics. I listened to Nelly's Nellieville and the speakers were pumping out the deepest, tightest and most tunefull low end with no (or almost no) sense of strain.

I wonder if maybe...just maybe....the attempt to mechanically decouple the midrange driver from the cabinet resulted in a large narrow suckout, and a driver that mirror-imaged its departure from linearity had to be designed/constructed to sum as having a relatively linear SPL response.
Still I would have rather a linear driver been mounted in a Seperate Box (wait a minute....was this not the design parameter of the SBLs?) instead of adding a lossy mechanical notch to a driver that is attached to the same box as is the tweeter.
 
Here are the electrical impedence sweeps of each driver, mounted in the cabinet, without the crossover. The midrange unit appears well behaved in this environment above 300 Hz....unlike the tweeter which has a resonant spike centered around 800 Hz and extending into its original crossover determined bandwidth.

 
Dear all,

Ron has asked me to post a small review of his x-overs as it seems that I am the first to try them outside of the USA. Ron and I have had pretty similar systems, both going from CDS2/52/six pack to CDS3/552/500, and in both cases with DBL's. We have also had similar experiences with the 500 being a bit 'fierce' compared to the active set up. The real difference is that while I have been scratching my head as to what to do, Ron has had new x-overs made to a spec that is dramaticaly greater than the standard Naim affair. No small feat in itself.

The areas I have had difficulty with the Naim PXO is that while exciting, the midrange and the treble is quite forward, aggressive and harsh and there is quite a suck out in the upper bass/lower mid region. This leaves a feeling of thinness to the sound with no real believeable body to instruments or voices. I also have a bit of bass boom even though my room is well bass trapped. As you can imagine this does not a happy camper make and after speaking to Marc Newman and Ron who both convinced me that the new x-over would cure all of my ills,I was willing to pay out on postage to give them a try (around £250 to the U.K. + about £70 to customs). When they finally left the factory the travel time was about 10 days by air mail which is good.

Once opened, I spent no time in fitting them in place and the first notes out of the boxes were very smooth indeed. Gone was all the harshness in one fail swoop and in return a sound that projected well out into the room. For a while the speakers were stuck on Mana SBs quite close to the wall and I went about a week before I was able to get someone to give me a hand to shift them out into a new position. I had been told that the DBLs would need moved out from the wall about 12" to cope with the extra bass and to expect a fair lift in performance once done. I have ended up about 16" out from the back wall but do have a bass that still booms a bit but is better controlled than before.

The long and the short of it all is that I think the new x-overs are stunning. I now have DBLs that image like crazy, have dynamics and slam in abundance and a far greater cohearance to the sound. Singers take on such a presance centre stage that makes you want to open your eyes to make sure they are not there. Individual instruments have a life of their own that is so believeable and out of the box that I know that I had never heard my 500 perform at anything near it's full potential.

As you can gather the x-overs are not going back. However I am not buying this pair (the original porototypes) but rather ordering the same that Ron uses himself, with the Cardas caps and cable. Although they have not fully cured my bass problems living in a 2nd story flat with springy floorboards they propably wouldn't. I am about to move to a new house that has a slightly bigger room, a concrete floor and a back wall about a foot and a half thick. How they will sound? I can only wonder. This pair will be available for dem once my new pair arrives so Ron tells me. I guess anyone wishing to hear them can get in touch with Ron and then let me know.

I have to say at this point a big thanks to Marc and Ron who have both offered lots of encouragement in taking the chance to try the x-overs and especially to Ron who took the big risk in sending them to me.

Sean.
 
Sean,

Congrats - on the x-vers and new place. Hope all is well with you. Give me a call sometime.

rgds

Dev

ps. I have a set of Audio 42 "Ultimate reference" x-overs between my SBL's at the moment - apparently they cost £4k!, very nice though.
 
You must log in or register to reply here.


advertisement


Back
Top