Focal-Seas 2-way: Old Meets New

[tpremo55]

While this will be a somewhat unique project as there are very few people out there with old Focals laying around, I wanted to post it here to both glean what experience I could off the list from working with these drivers as well as portray the design process for the benefit of the expert tutelage that is so often provided. …that and I just can’t bring myself to throw these up on ebay and go buy a pair of ‘new’ drivers.

For about fifteen years, I’ve had a set of Focal 7K011 DBL drivers in boxes waiting for me to pick up the hobby again. Fifteen years ago, the tools that we have today were largely not available and certainly not to someone with a college budget. I’ve decided to pull them out and create what I hope to be a respectable 2-way floor-stander.

After reading a lot of the recommendations given here and listening to many designs (ModulaMT, Murphy blaster RS 3-way to name a few), I picked up a pair of the Seas H1212 (27TBFC/G) to match with these.

While I am running a few basic design calcs, I have read a number of references to the tendencies for the Kevlar cones to have some issues in their response – I believe I the upper mid-range. While I have run across many general comments, I have not seen anything specific on what the issues are. Has anyone had experience with this or other Kevlar drivers and wouldn’t mind providing some insights?

I’d like to post a bit of progress as I go in hopes this also helps keep me running with the learning curve on the design tools.

As T/S detail on these is somewhat limited, I did pull a few tests in Sound Easy after a 48-hr tone at Fs to about ½ x-max and got the T/S Parameters posted below for starters. I do not yet have a mic and preamp (next $100 out the door). For starting enclosure design, I’ve got a 21L enclosure with a 41Hz tuning frequency that looks decent for starters. I could get a little uneasy about the excursion in the sub-20Hz region, but I won’t need these to play at crazy high levels for HT or anything – after all, I just built the Statements for that application.

Thoughts, comments, and opinions welcome - especially those that may apply to this project. :T

Thanks,
Todd

[Nichol1997]

I have the same mids as you and 2 years ago I finally got around to making an enclosure for them. They were sitting in the basement for nearly 20 years just waiting to be used.

I made them into a 3-way system with Focal tweeters (T120k) and woofers (10k 515) from the same era. I am using an active crossover at 100 Hz 24 dB/octave and 2,700 Hz 24 dB/octave both with Linkwitz-Riley slopes.

The mids are in a sealed enclosure of about 0.25 cubic foot and I think the f3 is around 100 Hertz.

I have heard the same thing about them ringing in the upper frequencies but the Focal spec sheet that I have shows no peaks in their frequency response. The speakers sound very detailed and at times can sound a little harsh. I am not sure if this is the driver or if it is the recordings.

I know that it is best to cross them as low as possible to avoid this ringing that everyone talks about. The dealer that I bought them from suggested to cross them at 2,500 Hz. You picked a good tweeter to go with these because you have the option of crossing them low.

[tpremo55]

I have the same mids as you and 2 years ago I finally got around to making an enclosure for them. They were sitting in the basement for nearly 20 years just waiting to be used.

I made them into a 3-way system with Focal tweeters (T120k) and woofers (10k 515) from the same era. I am using an active crossover at 100 Hz 24 dB/octave and 2,700 Hz 24 dB/octave both with Linkwitz-Riley slopes.

The mids are in a sealed enclosure of about 0.25 cubic foot and I think the f3 is around 100 Hertz.

I have heard the same thing about them ringing in the upper frequencies but the Focal spec sheet that I have shows no peaks in their frequency response. The speakers sound very detailed and at times can sound a little harsh. I am not sure if this is the driver or if it is the recordings.

I know that it is best to cross them as low as possible to avoid this ringing that everyone talks about. The dealer that I bought them from suggested to cross them at 2,500 Hz. You picked a good tweeter to go with these because you have the option of crossing them low.

Thanks for the response. You are correct in that one of my goals with this setup is to get the crossover frequency as low as reasonable. Based on other designs using the H1212 (27TBFC/G), it appears that 1800 Hz is a popular crossover point and is pretty low.

WhatI have not seen yet is the published upper end frequency response plot for the 7K011-DBLs. They are old enough that I cannot find the detail online and have done a fair amount of looking.

Does anyone have a FR/Imp plot from a reasonable source? Nichol1997, did you happen to measure yours and have files I could load into SoundEasy?

I wish to measure my own once I get the setup, but the published plots are always good to see how well my test correlate as well as being a good place to start in the interrim.

About 20 years ago, I listened to a few designs using Focals in 2-way t-line alignment. They sounded incredible to me at the time (wonder if I would still think so). I ran some quick calcs with SE for both T-line and standard vented and found little benefit to the T-line design. Has anyone had experience with these drivers in a T-line setup?

I've also considered two alignments for the dual voice coil arrangement. First, I can simply run jumpers so that the two coils are wired in parallel and yield a 3.6 ohm nominal VCR. Atlernately, I have considered using the second coil for BSC. Has anyone ever used a DVC driver with one coil doing BSC duty? Any concerns with this approach?

Thanks again.
Todd

[Habs4life]

Atlernately, I have considered using the second coil for BSC. Has anyone ever used a DVC driver with one coil doing BSC duty? Any concerns with this approach?

That should work fine and that is what Audio Concepts did when they used that exact driver in their Sapphire model.I could probably dig up the xover schem of that model if you are interested.

[tpremo55]

That should work fine and that is what Audio Concepts did when they used that exact driver in their Sapphire model.I could probably dig up the xover schem of that model if you are interested.

That would be great - I'd very much appreciate it. I've studied what I could find on the Sapphires and used to follow AC a fair amount back in the day. Made a few designs with their AC8 and AC10 woofers - well performing drivers of the early 90's and a good value for the money. IIRC, the Sapphire had a much higher crossover (I want to say around 3200Hz, but I could be wrong). That used the Focal T120K kevlar tweeter - didn't it? I think the Seas can go much lower than the Focal tweeters. I do however note that the T90 and T120 series are still available through Zalytron.

[Habs4life]

OK I found it in an old copy of Speaker Builder.As long as the moderator does not mind me doing so I will scan it and post it for you when I get a chance.Its unusual to say the least.They say it is a minimum phase (first order) design and uses the second coil for upper midrange response shaping.This is the MKII version of the Sapphire and yes it used a modified Focal T120K tweet.Later versions used the Focal Titanium dome then the Scan Speak 9500 was used but xover was likely modified accordingly.

[Habs4life]

It appears AC didnt actually use the second coil for BSC but connected a notch filter on it to tame a problem at 3.7k.However scanning through old copies of SB I found two examples of designers using the second coil for BSC.One is the Focal Egg that used a Focal 7C014-DBE and the other is the Swan IV that used a pair of 5N412DB 's.

[ThomasW]

OK I found it in an old copy of Speaker Builder.As long as the moderator does not mind me doing so I will scan it and post it for you when I get a chance.

No problem... :T

[tpremo55]

It appears AC didnt actually use the second coil for BSC but connected a notch filter on it to tame a problem at 3.7k.However scanning through old copies of SB I found two examples of designers using the second coil for BSC.One is the Focal Egg that used a Focal 7C014-DBE oNE

Interesting...
What year/version # of SB are you referencing? I think I only go back to about 1995, which it probably just after these were heavily discussed.

[tpremo55]

No problem... :T

Thanks Thomas. I rather feel like we are digging through a chest up in the attic and blowing the dust of old books... 8)

[Habs4life]

Interesting...
What year/version # of SB are you referencing? I think I only go back to about 1995, which it probably just after these were heavily discussed.

Issue 6 1990 and issue 4 1988(SwanIV).

Thanks Thomas I just wanted to be sure.

[Nichol1997]

I have the Focal spec sheets for all 3 drivers that I used in my design. Let me know if I can post it here (ThomasW) or I can email it to you.

[ThomasW]

I have the Focal spec sheets for all 3 drivers that I used in my design. Let me know if I can post it here (ThomasW) or I can email it to you.

Sure post it here.

[Habs4life]

Here you go tpremo55.



The ACI Sapphire II xover.

[Nichol1997]

The pdf that I have is too large to attach to the post. I can email it to whoever provides me with an address.

[Nichol1997]

The Focal specs for the 7k011-dbl show a 3 dB peak centered at 4kHz before they roll off. This does not seem like a big deal to me but I might be wrong.

I have heard that Focal tends not to fudge their specs. But like I said I have heard some harshness to them, not sure if it is the recording. If a CD does sound harsh I will turn the gain down on the tweeters (I have a Marchand vacuum tube cx, I think it is model number XM126) and this usually makes them sound more natural.

I am curious what you end up doing with the cx design. I might venture into designing a passive cx. Do you think you might measure the drivers in the future?

[tpremo55]

I am curious what you end up doing with the cx design. I might venture into designing a passive cx. Do you think you might measure the drivers in the future?

We'll I won't have them measured immediately even if I get the equipment in the next few weeks. I'll be traveling the balance of the year between business and family. In the interrim, I will likely get the curves into Jeff Bagbys PCD or even SE and play around. Once I get to something that I think is a good start, I will post it here. I'll probably prototype a cabinet fairly quickly and use dual binding posts to I can mess with the crossover externally until I get it voiced.

This is a learning curve for me, so please be patient - and thanks again for the guidance and information.

Todd